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Après Snowpack • The Challenges of Forecasting Small, But Mighty, Polar Lows   • The Changing Climate’s Snowball Effect   • How the Ski Industry Stopped Worrying and Learned to Love Climate Activism   • How Infrastructure Standards Miss the Mark on Snowmelt   • The Who, What, When, Where, and Why of the Polar Vortex   • Testing on the Tundra: NASA Snow Program Heads North   • SnowSchool Spans the States   • Winter’s Melting Point  

It begins at the height of winter in the mountains, when the landscape is particularly inhospitable. The surveyors arrive on skis, snowshoes, and snowmobiles. Some fly in by helicopter. Others travel the backcountry for days. When they arrive at their destination, there’s critical information to collect: the depth of the snowpack and how much water it holds. For regions confronting the effects of climate change, more and more hinges on the results.

“It all boils down to how much water makes it down into the reservoir,” said Sean de Guzman, chief of snow surveys and water supply forecasting at the California Department of Water Resources. De Guzman has it easier than some. Between February and May, around the first of each month, he drives to the Phillips Station snow course—a designated site for measuring the snowpack—located at around 6,800 feet (2,100 meters) of elevation in the Sierra Nevada. Once there, he manually inserts a tube into the snowpack, an instrument and method developed in the early 20th century by James Church, a professor at the University of Nevada, Reno who wanted to help put an end to local water wars by finding a way to estimate how much Lake Tahoe would rise in springtime. With the tube, de Guzman is able to measure the snowpack’s snow water equivalent, or the amount of water the snowpack contains at that location.

Today there are approximately 1,600 snow courses in the United States, with around 260 in California, primarily in the Sierra Nevada and the southern Cascades. Some date back more than a hundred years. Data from these locations, said de Guzman, represent the longest-running climate record in the Sierra Nevada. In the West, manual snow surveys are augmented by data from an automated snow telemetry (SNOTEL) network maintained by the Department of Agriculture’s Natural Resources Conservation Service that provides hourly snowpack measurements.

What these collective data tell snow surveyors, water resources managers, policymakers, and millions of people enduring water shortages, drought, flooding, and wildfires is that the snowball effect of climate change often begins, appropriately enough, with snow. And snow—how much falls, where and when, how much accumulates, and how quickly it melts—is changing.

“As a whole, over the last 70 years, we’ve seen a decline in snowpack,” de Guzman said. “With the warming temperatures and a warming climate, you can expect the snow-line—basically where that snow transitions into rain, and vice versa—to increase,” or climb in elevation.

Even when the snow survey data are relatively promising, other climate factors can inhibit a favorable outcome. At 59% of average on 1 April, California’s 2021 winter snowpack had more snow than was measured in any of the state’s 2012–2016 drought years. At the height of that drought in 2014, the snowpack on 1 April was at only 5% of average. And yet, de Guzman said, the 2021 snowpack yielded about the same amount of runoff as during those very dry years. “If you have more snow, you expect more [runoff], but that didn’t happen this year,” he said. The reason in part was that another low-rainfall year resulted in dry soil, which soaked up more of the runoff. “The snowpack was melting,” de Guzman said, “but the rivers weren’t rising.”

A Shrinking Season

There are different contexts and consequences across the United States, but all regions are struggling with rapid change. While the West grapples with water shortages amid severe drought, other parts of the country have become more vulnerable to extreme thunderstorms and flooding as more precipitation falls as rain rather than snow and as snowmelt occurs earlier in the spring. Increasingly, snow will also accumulate later in the season. An analysis by Climate Central showed that between 1970 and 2019, snowfall measured in 116 U.S. locations had decreased by 80% before December, and at 96 locations it had decreased by 66% after 1 March. But though historical data can reveal broad regional trends and patterns, they are becoming a less reliable forecasting tool as the warming climate throws snowfall patterns into disarray.

“The snow season is shrinking,” said Hans-Peter Marshall, an associate professor in the Cryosphere Geophysics and Remote Sensing group at Boise State University. But how much snow falls within that shortened seasonal window, he said, is difficult to predict. “The main thing we know is there’s going to be larger fluctuations, and the year-to-year variability is likely to increase.”

That variability includes the possibility of heavier snowstorms even as temperature averages trend upward. There’s no consensus on why warming has what appears to be a counterintuitive impact. According to Marshall, one reason the western United States might experience bigger storms is that a heated atmosphere can hold more water. In a warmer climate, water from the ocean could potentially make its way to the mountains, and more of that water might fall as heavy snow or torrential rain.

Meanwhile, warming Arctic temperatures may contribute to the kind of frigid blasts that reached as far south as Texas in 2021 (with catastrophic results) by disrupting the polar vortex, weakening the Northern Hemisphere’s polar jet stream and causing Arctic temperatures to dip south and warmer air to move north.

In the West, as the snow season shortens and the snowpack shrinks, so too does the water supply. In August, the federal government for the first time declared a water shortage on the Colorado River, a move that will reduce the amount of water allocated to Arizona and Nevada in 2022. (Mexico will also see a reduction in its share of the Colorado.) A continued water shortage will reduce water allocated to California.

“If you’re living in the West, you’re going to feel it,” said Amato Evan, an associate professor of climate sciences at the University of California, San Diego’s Scripps Institution of Oceanography. “In regions where the snowcap is vulnerable, like California, we’ve had year after year of 46 drought already,” demonstrating that the consequences are real.

The mountain snowpack, Evans said, acts as the state’s water bank for the year, melting slowly over the course of the summer and refilling depleted reservoirs. But snow that melts too early overwhelms reservoirs and can’t be captured and stored for use later in the year. And runoff that evaporates in warm, dry conditions or, as de Guzman described, gets absorbed into the earth before it reaches reservoirs, results in low water supply early on in the season.

A Recipe for Disaster

Both scenarios may have far-reaching consequences. In California, 2021’s lower than forecast runoff contributed to drought emergency proclamations being declared in May, for 50 of the state’s 58 counties, with state agencies directed to instigate a series of measures to conserve the water supply.

According to Marshall, the entities that decide how much water to release from dams must constantly estimate how much remains in the seasonal snowpack—decisions made more challenging by unpredictable snowfall. Though snow surveys and telemetry data provide accurate measurements for the area immediately surrounding snow courses and sensors, the data aren’t necessarily indicative of what’s happening between the sites. Currently, Marshall said, water managers might take a survey site’s 30-year average, compare it with streamflow over 30 years, and find the statistical correlation between the two. But that approach depends on a stationary climate, and these days, Marshall said, the current year is rarely representative of the past 30.

“As predictions get harder and harder in a changing climate,” he said, “we’re at this point where we need to make a paradigm shift, [and go] from just looking at individual sites and correlating them over the last 30 years to actually being able to estimate how much snow is everywhere on the landscape.”

Marshall and his group at Boise State are helping to fill in the data gaps by supporting NASA’s SnowEx campaign, which uses coordinated airborne and field experiments to determine the best combination of sensors for measuring snow globally from space. Current monitoring from space can tell scientists where snow cover is located but not how much of it there is.

“We’re operating old infrastructure in a changing climate, and that is a recipe for disaster.”“That’s one of the largest components of the water cycle that we just don’t have a very good handle on,” Marshall said.

When Marshall first began his work in Idaho in 2008, water managers showed less interest in new approaches than they do today. As the climate changes, weather events are altering the snowpack in unique ways, making reliable forecasting technology crucial for implementing decisions that affect water allocation for agriculture, water supply for communities, and flood forecasting.

According to de Guzman, incorporating forecasts into infrastructure operations, rather than relying on historical data, would enable water managers to better determine when to release water from reservoirs.

“A lot of the regulations and operations and maintenance manuals on how we operate reservoirs are built off old historical data,” de Guzman said. “So we’re operating old infrastructure in a changing climate, and that is a recipe for disaster.”

All Over the Map

In the Midwest and Northeast, less snowfall and more rain affect everything from agriculture, as farmers struggle with soil erosion, to the recreation industry, as the snow sport season shortens. In both cities and rural areas, increased rainfall and more frequent severe snowstorms will strain critical infrastructure systems and put vulnerable populations at risk.

In the Great Lakes region, warmer temperatures reduce ice cover on lake surfaces, leaving water open for lake-effect snowstorms. Increases in these storms in the short term could overwhelm snow and ice removal systems and affect roadways, buildings, and power lines. In the long term, as temperatures continue to climb, the air moving over the lakes will be warmer, and rain will fall instead of snow.

Abigail McHugh-Grifa is a founding member and executive director of Climate Solutions Accelerator of New York’s Genesee-Finger Lakes Region, which includes the city of Rochester where the nonprofit is based. McHugh-Grifa sees signs that the climate is changing. “Certainly we are already seeing the impacts of the weather just getting weirder and more unpredictable at all times of the year,” she said, adding that in the past few years, heavy snowfalls have quickly melted rather than accumulating. “It will dump a lot of snow on us and then melt and then dump a lot of snow on us and melt again. It’s just all over the map.”

“Even though we are seeing extreme weather conditions and other impacts of climate change, most local municipalities and community members aren’t making the connection yet.”Patterns can be difficult to tease out in an area like Rochester, where winter is the fastest warming season. The city has experienced a slight downward trend in snowfall over the past 50 years, with a more dramatic decline expected in the next 20–30 years, according to Climate Central meteorologist Sean Sublette in an interview for Rochester’s WROC TV. But in the short term, Rochester, like other Great Lakes communities, will likely see more lake-effect snowstorms, followed by warming springtime temperatures that can hasten snowmelt and lead to, among other changes, disruptions to the growing season.

For McHugh-Grifa, whose organization seeks to engage the community and public officials in mapping out solutions for adapting to climate change, getting leaders to recognize the urgency of the task can be the biggest challenge. “I wouldn’t say that any municipality around here is being bold enough or ambitious enough in their approach,” she said. “Even though we are seeing extreme weather conditions and other impacts of climate change, most local municipalities and community members aren’t making the connection yet.”

New York is a home rule state, meaning in short that municipalities have the autonomy to pass local laws. McHugh-Grifa believes that for public policies to shift toward climate adaptation planning, multiple municipalities must get on board. “If one municipality wants to go above and beyond, it’s challenging for them because there’s a real fear that, for example, if they…demand higher standards for building efficiency, then the developer is just going to go to the next town over.”

Without increased regional cooperation and collaboration on land use, transportation, and building codes, McHugh-Grifa said, policy planning for climate change adaptation will continue to stall. In part to respond to this challenge, Climate Solutions Accelerator uses a collective impact approach, working to convene partners, ensure that the voices of those most affected are represented, and develop a shared regional plan. “No one organization or one individual or one solution can possibly meaningfully address this problem, so we need this kind of massive coordinated response,” she said.

In many urban areas where snow, and winters in general, are predicted to transform in the decades ahead, climate action plans have been developed to set goals for reducing greenhouse gas emissions. Chicago, Boston, and Philadelphia are among the U.S. cities that have joined C40 cities; a global network of so-called megacities whose mayors have pledged to deliver on climate change goals. Ultimately, with sharply divided political positions among top elected officials, local leaders may have the largest influence on whether their cities can adapt quickly enough to meet the changing climate.

A Climate to Reckon With

In Alaska, one of the fastest warming regions on the planet, the effects of changing winter patterns—including snowfall, snowmelt, and permafrost thaw—will have wide-ranging ramifications for the state’s human and wildlife inhabitants. Many animals and native or migrating fish depend on snow, ice, and streamflow for habitat. Communities rely on snow for transportation and recreation and on snowmelt for hydropower. Uncertainties for such key industries as timber and fisheries contribute to economic vulnerability.

In northern coastal areas, Alaska Native communities that hunt for subsistence or migrate to work depend on the sea ice and permafrost—a layer of frozen ground—for survival. As the ice melts and the permafrost thaws and becomes less stable, villages may lose homes and other structures to flooding or erosion. Diminished mobility cuts off access to hunting and fishing grounds and isolates residents from emergency services. In some cases, the thaw has proven fatal.

“In the last couple of years, we’ve had at least a dozen people go through unstable ice,” said Amy Lauren Lovecraft, director of the Center for Arctic Policy Studies and a professor of political science at the University of Alaska Fairbanks. “It’s unimaginably tragic,” she said. “It’s the people who don’t produce or produce very little carbon emissions who are most impacted.”

And yet, Lovecraft said, current and past governors have been careful to avoid politically charged policies that directly address climate change, leaving it to villages and boroughs to take on the role of strengthening their communities. “In the absence of federal or state direction, it’s happening at the local scale,” Lovecraft said, adding that, in fact, these communities know best about how changes in snow affect them. “It’s not an entirely negative thing that it has to happen from the bottom up.”

Still, there is a role for the state to play, Lovecraft said, including setting parameters, spreading information, and backing local-scale projects that address mobility, housing, hunting, and other concerns. “It’s a matter of how smooth that transition could be,” she said.

As scientists continue climate research and refine technologies for accurate forecasts and measurements, communities will need to find support for applying new methods and data and implementing policies that address specific changes in their regions. But for some areas already deeply affected by changing winters, paradoxical weather events and the vagaries of snowfall patterns, winter storms, and snowmelt may hinder efforts to communicate the urgency of taking action.

Ultimately, the question for Alaska, Lovecraft said, isn’t whether the science on climate change is correct but, rather, whether it’s a message that anyone wants to hear.

“Does Alaska really want to face the pain of doing a transition that’s conscious, or do we ignore it? Eventually, we’re going to have to reckon with it.”

Author Information

Korena Di Roma Howley (korenahowley@gmail.com), Science Writer

Après Snowpack • The Challenges of Forecasting Small, But Mighty, Polar Lows • The Changing Climate’s Snowball Effect • How the Ski Industry Stopped Worrying and Learned to Love Climate Activism • How Infrastructure Standards Miss the Mark on Snowmelt • The Who, What, When, Where, and Why of the Polar Vortex • Testing on the Tundra: NASA Snow Program Heads North • SnowSchool Spans the States • Winter’s Melting Point

An interview with the president of the International Ski Federation, Gian Franco Kasper, made its way around the Internet faster than locals flocking to the first chair on a powder day. In the 2019 interview, Kasper told a Swiss newspaper that he preferred working with dictators to environmentalists and that there is no proof of “so-called” climate change. The International Ski Federation represents more than a hundred national ski organizations in the world and organizes the Olympic ski events.

Many did not take kindly to Kasper’s remarks. Days after an English translation of snippets from the interview was published in the sports publication Deadspin, the outdoor community sent a letter with nearly 9,000 signatures to the federation demanding that Kasper step down.

The letters said that climate change threatens the existence of the ski industry and that Kasper’s comments went against the experience of resorts that have already closed because of climate change. “Kasper’s remarks should disqualify him for a leadership position in any business capacity, let alone that of a ski federation,” read the letter from the nonprofit Protect Our Winters (POW).

Kasper apologized, and 7 months later, the International Ski Federation signed on to the United Nations Sports for Climate Action Framework. This year, Kasper retired after 23 years as president and was replaced by a candidate, Johan Eliasch, endorsed by John Kerry, the U.S. special presidential envoy for climate.

Skier and mountaineer Caroline Gleich swapped her ski gear for a blazer and slacks before testifying before Congress in February 2020. Gleich is a salaried athlete influencer for the nonprofit Protect Our Winters. Credit: Caroline Gleich

The shift in perspective symbolized by Kasper’s final years in office reflects a concern by the industry that winter may become a shell of its former self. Already, the snow-water equivalent in the western United States has dropped 41% since the early 1980s, and the ski season has decreased by 34 days. Half of all Northeast ski resorts may go out of business by 2050, and climate modeling predicts that 90% of ski resorts in the West won’t be financially viable by 2085 if greenhouse gas emissions aren’t curtailed. Not that they’ll have much to drink anyway: snow melt provides up to 75% of the water supply in western states.

Until recently, “there was an ethos within the outdoor industry and even the outdoor community to try and remain apolitical, and [these groups] saw climate change as a political issue,” said Mario Molina, executive director of POW, which organized the letter campaign to oust Kasper.

Social media abuse would rain down on those daring to mention climate change, Molina said. Trolls descended on athletes speaking about climate, telling them to stick to their sport. Resorts risked angering customers when unleashing new sustainability initiatives.

Outdoor enthusiasts remained ambivalent. A 2020 POW report focused on the United States concluded that members of the community—people striving for physical sensations, for inner well-being, or to achieve new personal records—“are not prime candidates for abstract communal action.”

But the same report showed that 90% of outdoor enthusiasts think climate change is caused by humans. The report also found that people who participate in outdoor sports are politically diverse: Democrats make up 40% of outdoor enthusiasts, whereas 31% are Republican and 29% identify as independent. The results were based on surveys of 2,100 people across a variety of sports, interviews with professional athletes, and online focus groups.

Downhill Emissions

Ski resorts are cutting emissions in creative ways.

Aspen Skiing Company in Colorado partnered with a local mine operator to trap methane from one of its coal mines that would otherwise leak into the atmosphere. The methane powers the ski area, producing energy equivalent to what’s needed to power roughly 2,400 homes. Berkshire East Mountain Resort in Massachusetts powers itself on 100% renewable energy using solar and wind on site. Jackson Hole Mountain Resort in Wyoming operates 100% on wind energy purchased from a wind farm in neighboring Idaho.

Skiing and snowboarding produce greenhouse gas emissions by powering ski lifts, snowmaking, and lodges. Tourists fly and drive across the world to ski, staying in chateaus and drinking at heated outdoor bars. But cutting their emissions won’t stop global climate change.

“Even a victory like a large corporation cutting its carbon footprint by 30 percent—the stuff of Shazam-level super-heroism and incredibly difficult to pull off—wouldn’t even dent the climate problem,” wrote Aspen Skiing Company senior vice president of sustainability Auden Schendler in the Stanford Social Innovation Review in 2021. “Systemic change is the only path to climate stability.”

For their sport to survive climate change, skiers will need to not only cut their emissions (see downhill emissions) but also somehow convince the rest of the world to cut its as well.

Because the industry’s longevity relies on the actions of others, it has been slowly emerging as a vocal advocate for broad-based systemic climate reform. Activists have been spinning two webs of influence to enact change: (1) creation of an influencer-led, identity-driven voter bloc and (2) a jobs-first pitch to lawmakers on Capitol Hill.

The NRA of Skiing

The National Rifle Association (NRA) is not a group most would associate with skiers and snowboarders. But Schendler said the cohorts have more in common than you might expect.

“This is a unmobilized cohort that could swing elections.”“It’s a very similar group if you think about why they’re motivated,” Schendler said. “They’re gun people in the same way that I have a friend who says, ‘I don’t climb, I’m a climber.’ ‘I don’t ski, I’m a skier.’”

“Think about gun owners, and then think about who’s just as amped up, passionate, influential, wealthy, crazed? Well, it’s the outdoor [community]. These are all fanatics,” he said. Just look at how they spend their time: Skiers hit the slopes wearing garbage bags in the rain. Climbers live in their vans chasing the next project. Runners don headlamps to clock kilometers before dawn. “This is an unmobilized cohort that could swing elections.”

If emissions remain unchecked, the snow season will be cut at least in half by midcentury at many ski resorts in the contiguous United States. Credit: NOAA

The NRA has outsized power in Washington despite its middle-of-the-road spending on lobbying. As Gallup reports, although most people in the United States approve of gun control, Congress hasn’t imposed tighter regulations.

Even the NRA’s election spending is a fraction of what companies or individuals invest in attempting to sway polls.

“The NRA is not successful because of its money. To be sure, it is hard to be a force in American politics without money. The NRA has money that it uses to help its favored candidates get elected. But the real source of its power, I believe, comes from voters,” said Adam Winkler, a professor of constitutional law at the UCLA, School of Law and author of Gunfight: The Battle over the Right to Bear Arms in America, told the Guardian in 2018. The organization remains one of the most powerful lobbying groups in Washington.

No longer are skiers and snowboarders just people who like chasing powder for fun; they are citizens of the “Outdoor State,” a body politic that demands their allegiance and fidelity.As the chairperson of POW’s board, Schendler has talked about the NRA as an inspiration for years. POW’s mission is to mobilize millions of outdoorsy people to climate action. Although POW originally focused on snow sports like skiing and snowboarding, the organization’s target demographic now includes climbers, trail runners, and bikers as well.

POW mobilizes its base by reframing the political identity of an outdoors person, complete with voter guides and influencers. No longer are skiers and snowboarders just people who like chasing powder for fun; they are citizens of the “Outdoor State,” a body politic that demands their allegiance and fidelity.

The Influencer Economy

Professional snowboarder Jeremy Jones founded POW in 2007, and ever since, the organization has recruited a collection of famous athletes to spread its message. “What makes POW different and unique—and I think where our potential really lies—is in this cadre of influencers,” Molina said.

The more than 100 athletes in POW’s alliance program have received training in science, advocacy, and clean energy. In exchange, they agree to appear at a certain number of public speaking events, to write op-eds and social media posts, and to generally exist as POW ambassadors. The arrangement is somewhat like the billion-dollar industry of influencers who represent corporate brands on Instagram and other social media sites. But most of POW’s athletes volunteer their time apart from four paid “team lead” athletes who manage volunteers.

Tommy Caldwell, a world-famous rock climber with 820,000 Instagram followers, hosted an event with the League of Conservation Voters to get out the vote.Premier athletes like skier Hilaree Nelson, who boasts the first ski descent of the fourth-highest peak in the world (Lhotse, in China and Nepal), touts POW to her 59,200 followers on Instagram. Tommy Caldwell, a world-famous rock climber (821,000 Instagram followers), endorsed Joe Biden for president because of his climate-friendly policies and hosted an event with the League of Conservation Voters to get out the vote in 2020. Endurance runner Clare Gallagher (44,500 Instagram followers) penned an op-ed in UltraRunning magazine in April 2021 on coping with climate anxiety.

In the U.S. Senate race in Montana in 2018, POW athletes rallied around Democratic candidate Jon Tester, a two-term senator with a proenvironment voting history.

Mountaineer Conrad Anker of Bozeman and fly-fisher Hilary Hutcheson of the greater Missoula area led the charge. The two gave press interviews, wrote op-eds, and posted on social media in support of Tester, all of which POW shared with its followers through social media, email, and the web, said Auden. Tester won by nearly 18,000 votes.

Although it’s unclear how much POW played a role in Tester’s victory, athletes drawing in incremental votes is exactly the organization’s mission, Schendler said.

Other organizations also target environmentally conscious voters. The nonprofit Environmental Voter Project (EVP) reaches out to people who consider the environment one of their main political issues but visit the polls only in presidential elections. This cohort could pack a punch: An EVP report from this year found that environmental voters could swing 2022 midterms in six purple states if they showed up. These voters are predominantly young, female, and disproportionately Hispanic, Asian American, and Pacific Islander.

Like POW, EVP wants to remake the model of a “good environmentalist” from someone who recycles or is a  vegetarian into someone who votes in all elections, big or small.

Protect Our Winters founder Jeremy Jones, rock climber Tommy Caldwell, and ski mountaineer Caroline Gleich testify in front of the Senate Democrats’ Special Committee on the Climate Crisis in Washington, D.C., in 2019. Credit: Jesse Dawson

Consumer preferences force businesses to adapt, too. A 2016 study of 83 Western ski resorts published in Strategic Management Journal found that “environmental institutional pressures”—defined as regulatory, normative, and cultural pressures—have led to increased adoption of climate change mitigation practices by resorts. These pressures were more successful at forcing resorts to adapt than were the adverse effects of climate change itself.

“I think we were able to actually nudge the entire industry into the realization that civic engagement is not a political activity.”In June, four of the biggest North American ski resort companies (Vail Resorts, Alterra Mountain Company, POWDR, and Boyne Resorts) signed a charter to enforce, among other things, unity in climate advocacy.

On the retail side, 82 brands have now joined POW’s brand alliance by giving $5,000 or more to the nonprofit. Burton and Patagonia have both contributed more than $150,000.

The recent events suggest that athletes, resorts, and brands agree that talking about climate change is now fair game. POW’s Molina credits his organization for this shift in opinion. “I think we were able to actually nudge the entire industry into the realization that civic engagement is not a political activity,” he said.

The next question is, What will the industry and its fans do with their newly found voice?

From the Statehouse to Capitol Hill

Fifty million Americans participate in outdoor sports, and the pandemic inspired many to visit parks for the first time. Although it’s easy to think of a solo paddle or a hike through a reclusive forest as far from an economic activity, outdoor adventures leave a trail of money in their wake: The gear. The clothing. The transportation. The marathon registration. The cabin. The after-trip milkshake.

But climate change threatens that money train: U.S. downhill skiing, just one subset of the outdoor economy, lost $1.07 billion over a decade because of lower snow years between 1999 and 2010, according to a 2012 POW and Natural Resources Defense Council report. This downturn led to a loss of up to 27,000 jobs, a drop in unemployment of as much as 13%.

Since the release of that 2012 report, there’s been a race to calculate just how much outdoor recreation is worth. POW releases estimates, the Outdoor Industry Association (OIA) has reported its own, and more estimates are in the works.

American consumers spend more on outdoor recreation than they do on pharmaceuticals and fossil fuels combined.In 2016, Congress passed an order for a thorough assessment of how much money the outdoor sector contributes to the U.S. economy. The Bureau of Economic Analysis set up a special fund for this purpose and in 2020 published a tally: $459.8 billion of current-dollar gross domestic product came from outdoor recreation in 2019. (The amount is half of the current-dollar gross domestic product from all arts and cultural activity in the country in 2019.)

According to a 2017 OIA report, American consumers spend about $887 billion on outdoor recreation annually. That is more than they spend directly on pharmaceuticals and fossil fuels combined.

These billions of dollars in market power form the backbone of lobbying by the outdoor industry. “It literally changed the conversation in Washington,” said advocacy lead Chris Steinkamp at Snowsports Industries America (SIA), who led POW previously.

Before hard economic numbers appeared, the ski industry appealed to lawmakers by expressing a love of winter and a fear of its expiration date. Now advocates tout the sector’s economic contribution to the U.S. economy. In Colorado alone, the ski industry generates $4.8 billion annually, according to a study by Colorado Ski Country USA and Vail Resorts.

Trade Organizations Band Together Amid Criticism

In 2019, SIA partnered with two other outdoor trade organizations to amplify their voices in Washington. Their goal is to use a jobs-first agenda to spur legislative climate wins.

The Outdoor Business Climate Partnership (OBCP) combines the power of SIA, which is a collection of winter recreation retailers, suppliers, resorts, and sales reps; the National Ski Areas Association (NSAA), which includes more than 300 alpine ski resorts and more than 400 suppliers; and OIA, an industry heavy hitter that represents 1,200 businesses in outdoor sports from big names like REI to small family shops.

The new partnership targets lawmakers in such states as Utah, Colorado, and New Mexico, where recreation is a major part of the state’s economy. OBCP’s priorities include putting a price on carbon, passing a clean energy standard, and supporting clean transportation.

Lawmakers on both sides of the aisle have aligned with OBCP. The partnership hosted Democratic Rep. Joe Neguse from Colorado and Republican Rep. John Curtis of Utah at a virtual event earlier this year, for instance.

Bipartisanship is at the heart of OBCP’s mission. “We can’t shame our elected officials into agreeing with us,” said Steinkamp. “We have to be allies and not adversaries.”

Steinkamp said that OBCP doesn’t spend time talking to or supporting lawmakers who are climate skeptics, however. Instead, they home in on Republicans like Curtis, who recently launched a conservative climate caucus.

“We were very strategic with the name because we wanted to be very clear that we were embracing the science with climate, but that we were conservatives,” Curtis said of the caucus in an interview with C-SPAN. “Today there are 65 members. It grows every day.”

Snowpack in the Sierra Nevada dropped sharply in 2015 (left) compared with 2010 (right). Credit: Jesse Allen/NASA

The industry’s cross-party approach has attracted criticism, however.

The political contributions of ski resorts and their executives came under scrutiny following a 2016 article by Porter Fox in Powder magazine. Fox, a former Powder editor and author of Deep: The Story of Skiing and the Future of Snow, wrote that industry tycoons such as executives from Vail Resorts and Jackson Hole gave money to candidates or political action committees with a record of opposing climate legislation, according to records from the Center for Responsive Politics.

“We should be thanking these members of Congress, not attacking them.”In a rebuttal, NSAA director of public policy Geraldine Link wrote, “The ski industry, like every other industry, is not ‘single-issue’ in its approach to advocacy.” Republican candidates who were singled out in the article helped protect water rights and support year-round activities, she wrote. “We should be thanking these members of Congress, not attacking them.”

Three years later in an opinion piece in the New York Times, Fox responded. Supporting candidates who bolster year-round activities and water rights but not climate isn’t enough, he wrote. “The time for soft-pedaling passed decades ago. At this very late stage in the game, the snow sports world needs decisive action.”

To achieve the Paris Agreement target of limiting average global warming to 1.5°C, relative to pre-industrial temperatures, the world will need to phase out all carbon emissions by 2040. Humanity has made some progress: Before the Paris Agreement was reached, we were headed toward 3.6°C warming. Now we’ve got that down to 2.9°C.

But we have a long way to go: 2°C would still bring catastrophic climate impacts. And the world will need to make emissions cuts like those from the COVID-19 shutdowns every year for the next decade to keep warming below 1.5°C.

Charting a Line for Years to Come

Famed alpinist and POW athlete Graham Zimmerman spent much of his twenties chasing peaks around the world. Even though he studied glaciohydrology in college, he pushed climate change to the back of his mind. And when he did think of it, he felt guilty for all the plane flights, car rides, and gear he tore through as an international athlete.

But in the 20-minute documentary An Imperfect Advocate from Outside TV, Zimmerman argued that climate activism is for everyone—even those with large carbon footprints. We see Zimmerman calling his representatives and visiting statehouses, high schools, and universities to talk up climate change policy.

“Our goal with solving the climate crisis is not to stop traveling, or stop heating our homes,” Zimmerman said. Instead, it’s to continue to do the things that “inspire us and drive us” but with carbon-neutral or carbon-efficient technologies. “And that all comes from government.”

An Imperfect Advocate represents a tension in climate activism that goes back decades. To halt carbon emissions and slow global warming, should individuals put their energy toward cutting their carbon footprint? Or should people focus on calling for top-down regulation from lawmakers? And what if the emitter isn’t a person, but an industry? Must an industry walk the walk before sticking its neck out for systemic change?

“The outdoor industry and winter sports industry are not the largest carbon emitters, but we rely on those larger [emitting] sectors like transportation and electricity,” said Amy Horton, senior director of sustainable business innovation at OIA. The dependence on these carbon-heavy activities is a catch-22: Carbon pollution is still needed to bring customers, but it’s also slowly eroding away the sport’s future.

A review of 119 research studies of climate change risk to ski tourism across 27 countries, shows clearly that the industry is in for a shake-up. Resorts can’t depend on natural snow anymore. They’ll need to pump more water and burn more power to make artificial snow, ski areas will close, ski seasons will shrink and shift, ski markets will bend and morph as skiers travel for snow or give up the sport altogether, and real estate values will shoot up or down accordingly.

The industry finds itself at a crossroads that environmental activists have long pondered: How can climate policy pass in the United States when the politics remain so divisive?

Steinkamp of OBCP doesn’t think the discussions over the past 10 years demanding immediate action have spurred productive policy, however. Although bipartisanship “takes time,” he said, “I think this is where we see the long-lasting change happening.”

POW has put its bet with a strong voter base of outdoors people—a group that overwhelmingly believes in climate change but is politically diverse—who it says could sway elections. OBCP is betting on forging relationships with emerging Republicans who believe in climate change to adopt climate legislation.

“I think this ship is slowly moving in the right direction,” Molina said of recent partnerships in the outdoor industry. “The next year or two will actually show us how many of the new coalitions and groups that have emerged are going to really put their weight behind the statements.”

Author Information

Jenessa Duncombe (@jrdscience), Staff Writer

The width of bedrock channels is a key factor controlling erosion and transport processes in mountain rivers. Channel width controls flow dynamics, the force exerted on the riverbed, and therefore erosion and sediment transport rates. A narrowing river will concentrate the flow over a small area, potentially enhancing sediment transport and erosion rates, and may generate obstructions. Conversely, a widening river may undermine the hillslopes and make them more unstable, leading to increased hillslope erosion and sediment supply.

Bedrock riverbed and banks are commonly eroded by the repeated impacts of sediment grains during floods. While some models exist that relate the rate of vertical incision to a river’s sediment flux and grain size, the influence of these parameters on the erosion of bedrock walls (and therefore on channel width) is not as well understood.

In an earlier paper, Li et al. [2020] proposed a model that predicts the erosion of bedrock walls through repeated impact by sediment grains by tracking the trajectory of each grain, but such models require huge computational power and time. In a new paper, Li et al. [2021] now provide an analytical solution, that is, a series of equations that replicate the results of the earlier model without needing to track every single grain.

This new model is much faster and can easily be integrated in models of landscape evolution, thus providing a new tool to explore more completely the interactions between sediment flux, grain size, channel width and the propagation of perturbations along rivers and up valley sides.

The model shows the circumstances in which one may expect rivers to narrow or widen as a function of how much sediment is coming through the river and what its grain size is, and is tested against a real river, Boulder Creek, in California.

Citation: Li, T., Venditti, J. G., & Sklar, L. S. [2021]. An analytical model for lateral erosion from saltating bedload particle impacts. Journal of Geophysical Research: Earth Surface, 126, e2020JF006061. https://doi.org/10.1029/2020JF006061

—Mikaël Attal, Editor, JGR: Earth Surface

Reviewers are critical to ensure quality and rigor in scientific publications. In most cases, their contributions are hidden because of our masked peer review system but, while many choose to remain anonymous to authors, it’s important that we know who they are and where they are. To mark Peer Review Week 2021, we wanted to share how AGU has been tracking and analyzing reviewer demographics. We shared previous work on reviewer demographics [Hanson and Lerback, 2017; Lerback et al., 2020] and, over the past few years, have continued to work on expanding the reviewer pool to engage a wider range of perspectives and ultimately publish more inclusive science benefiting larger sector of society. Expanding our reviewer pool also helps to supply an increasing demand for peer reviews as scientific output and submissions increase.

Sources of Demographic Information

AGU has several methods for identifying reviewer demographics. First, we use our member database to match authors and reviewers in our journal submission system with their member profiles containing gender, age, and race/ethnicity information. When  gender is not given in the member profile, we use the gender-name database Gender API, which uses first name and country to guess and we keep guesses with +90% confidence score. Some of the race/ethnicity categories are based on U.S. census categories (e.g., Asian American), so our current race/ethnicity data only applies to U.S.-based reviewers. However, we are in the process of updating our system so that the categories accurately describe the global population. Country of residence is determined from a person’s profile in the submission system. For those that don’t have it, we use their email suffix (when it identifies a country).

Gender of Reviewers

The number of invitations to review a paper sent to women (both total counts and percentages) has been increasing since 2016, although the rate at which they agree to review is slightly lower than male invitees, so the proportion of women agreeing to review papers (“final (agreed) reviewers” in the chart below) has nominally increased each year:

It’s tricky to develop a specific target for invitations to women, as reviewing receives less professional credit than publishing articles, leading research groups, chairing department committees, and other activities. Some members of the community are worried that over-burdening women scientists with reviewing will take their attention away from activities that more overtly advance their careers.

AGU is currently working on expanding co-reviewing opportunities, which will allow senior scientists to partner with those earlier in their careers to work together on reviews.However, by increasing reviewing opportunities for early career scientists, which, in the Earth and space sciences includes a higher proportion of women than older cohorts, younger scientists will benefit more from reviewing papers than those advanced in their careers. AGU is currently working on expanding co-reviewing opportunities, which will allow senior scientists to partner with those earlier in their careers to work together on reviews. This will help train early career scientists in peer review and expand future opportunities to review.

Geographic Region of Reviewers

An interesting comparison is between the location of the invited reviewer and the geographic region where our corresponding authors are located, as shown in the chart below. Though we’ve seen an increase in the proportion of review invitations sent to regions where we see the fastest growth in authors submitting papers, namely China, the increase in invitations isn’t as large as the increase in accepted papers from China. Additionally, the proportions of invitations sent to U.S.-and Europe-based reviewers have been declining but are still higher than their representation in our pool of authors whose papers are published.

Age of Reviewers

It’s important to disaggregate gender data by age group to see where specific improvements can be made. These next charts show age groups of reviewers, authors, and AGU members.

People invited to review papers are predominately mid- to late-career men (40s-60s). The largest cohort of women invited to review are in their 30s.

We typically compare invited reviewers to authors of accepted papers and members, shown below. Both authors and members are skewed slightly younger than invited reviewers, which indicates editors are more comfortable inviting those in the mid- and later-career stages. This could be due to the expertise of those in these stages (including being known published authors) or because these reviewers are a part of the editor’s professional network.

Increasing reviewing opportunities to younger scientists could help decrease the burden on mid-career scientists who likely have more teaching, administration, and/or family-related duties while having the benefit of training younger scientists earlier in their career on how to do a good peer review.

Reviewer Workload

Another interesting way to assess the diversity of our reviewer pool is to calculate the number of invitations per person within various demographic groups. For example, are we inviting the same men more often than we’re inviting the same women? We can calculate this by dividing the number of total invitations by the number of distinct email addresses belonging to that demographic group, with the chart below showing the resulting invitations per person.

The results show that we invite fewer women than men and much fewer unknown gender (majority China-based) than either gender. We also see that as the years progress, we are inviting the same men and women less often.

This decrease in invites per person is also seen in invited reviewer country-region. The chart below shows editors are inviting people in the U.S. more often than those in all other country-regions. However, we also find that we are inviting people by region less often indicating that in 2020, we expanded our reviewer pool.

Reviewing during the COVID-19 pandemic

Across the scientific community, there was considerable concern about how the pandemic would affect people’s capacity to submit papers and their ability to review. In May of 2020, we looked at the initial impact of the pandemic on our submissions; we now have enough data from the past year to understand how this has impacted our community.

Submissions increased overall and across all demographic groups (based only on the corresponding author) with proportions varying only slightly with no statistically significant difference between in-pandemic and pre-pandemic periods. Editors and associate editors invited slightly more reviewers in their 20s and 30s and slightly fewer in their 40s and 50s compared to previous years. Reviewer agree rates dropped a few points among women and increased a few points among men in 2020, as shown in the chart below.

Overall, paper submissions and reviewer activities increased (more submissions, more peer reviews) likely because stay-at-home orders were conducive to these types of desk-based activities (see survey conducted by the American Geosciences Institute on work habits in 2020). Though many survey-based studies showed that women (and men) with children reported less productivity and decreased job satisfaction, we found that these effects of the pandemic weren’t reflected in AGU submission and reviewing rates.

Increasing and Diversifying our Reviewer Pool

The pandemic illuminated the need to expand the reviewer pool, and also made AGU and other scholarly publishers—and quite acutely society at large—consider ways to make processes and systems more inclusive and equitable. Peer review plays a seemingly small part, but the effects on advancing the scientific record could be massive. So, what are some ways we’re trying to increase reviewer representation in key demographic groups?

We ask authors to consider suggesting reviewers who are in historically underrepresented groups in the Earth and space sciences, such as women, early career scientists, and racial minorities. We encourage editors to invite more author-suggested reviewers, not just for those papers but for other submissions. Though there is a worry that some authors suggest their “friends,” these names help to expand the reviewer pool when used for other submissions on a similar topic. We are deliberately increasing editor and associate editor appointments in target demographic groups. This chart shows that they do invite more reviewers from their region:

We’ve enforced term limits and renewals to help our editorial boards to make room for new perspectives. We’ve created author and reviewer resources in other languages (e.g., webinars in Chinese and Spanish and author resources in Chinese and Japanese. We encourage editors to engage younger women for associate editor and reviewer roles when the pool of advanced career women is overworked.

The pandemic impelled us to be even more thoughtful about who contributes to decisions about what gets published. Reviewers are the backbone to that endeavor.Our community takes very seriously our responsibility to publish accurate science that takes into account multiple perspectives and opinions, especially as human-caused climate change threatens to upend our way of life.

The pandemic impelled us to be even more thoughtful about who contributes to decisions about what gets published, which ultimately contributes to the solutions to address our society’s most pressing challenges. Reviewers are the backbone to that endeavor.

—Paige Wooden (pwooden@agu.org, 0000-0001-5104-8440), Senior Program Manager, Publications Statistics, American Geophysical Union

For decades, traditional silicon-based photovoltaic cells have been the industry standard for converting sunlight into electricity—but as a photon-absorbing material, silicon is not actually all that efficient. On average, solar panels made with crystalline silicon convert between 18% and 22% of the Sun’s energy into usable electricity, with an upward theoretical limit of 33%. Despite this limitation, crystalline silicon photovoltaic cells account for 95% of the solar cell market.

By layering traditional silicon cells with a mineral called perovskite, however, materials scientists are engineering more efficient tandem solar cells that significantly boost efficiency, without derailing well-established silicon cell manufacturing pathways.

“Tandem solar cells have significantly higher energy-conversion efficiency than today’s state-of-the-art solar cells. Thus, tandem cells can contribute to lowering the cost of solar energy, in particular in rooftop solar systems, where high efficiency is of central importance,” Dirk Weiss, a materials scientist with First Solar, recently wrote in Joule. “A new generation of low-cost tandem cells is needed to enable widespread implementation. Hybrid-perovskite top cells combined with silicon bottom cells are currently the most popular low-cost tandem candidate under development.”

In a new perspective, published in Applied Physics Letters, a team led by Laura Miranda Pérez, head of materials research at Oxford PV in the United Kingdom, and Chris Case, the chief technology officer at Oxford PV, presents a case for commercializing tandem solar cells by combining existing silicon cell technology with synthetic variants of the perovskite.

The mineral perovskite, also known as calcium titanate, was discovered in the Ural Mountains in 1839, but the perovskite used in solar cells is synthesized in a lab from readily available components. These perovskite solar materials can be applied in very thin layers, making them an ideal material to add to existing silicon cell manufacturing processes.

“Perovskites can enhance and advance silicon technologies without interrupting manufacturing.”“Perovskites are the perfect partner for a tandem system with silicon,” said Miranda Pérez.

By adding perovskite, which more efficiently captures the blue region of the solar spectrum, to silicon, which targets the red region, Oxford PV has set a record solar cell efficiency of more than 29.5%. With further development, efficiencies could reach as high as 39%, said Miranda Pérez. Other research teams have demonstrated that photovoltaic cells made with only perovskite and no silicon are also viable, but these solar cells cannot exceed the practical efficacy of any single solar cell, which is around 26%. The multijunction or tandem approach of Oxford PV is the best way to break the 26% practical efficiency barrier, said Miranda Pérez.

“Of all the alternative solar cell technologies, silicon/perovskite tandem cells are proving to be the most promising because they offer a degree of tunability that you don’t have with a lot of the competing technologies,” said Joseph Berry, a senior research scientist at the National Renewable Energy Laboratory in Golden, Colo., who was not involved in the new study. “This new perspective does a great job of showing how perovskites can enhance and advance silicon technologies without interrupting manufacturing.”

Scaling Sustainably

Oxford PV, a company cofounded in 2010 by University of Oxford physicist Henry Snaith, has focused on developing perovskite-on-silicon tandem cells since 2014. Initially, ensuring the long-term stability of perovskite was the principal challenge, but current perovskite-on-silicon tandem cells have passed key accelerated stress tests for solar cells, known as the IEC 61215, established by the International Electrotechnical Commission. The tandem cells are expected to meet or exceed the industry expectation of 25 years or more of durability in the field.

The team’s next step is to ramp up production at Oxford PV’s factory in Brandenburg, Germany, which houses the world’s first perovskite-on-silicon production line, with a capacity of 100 megawatts. “The line build-out has been completed, and we will be taking tandem cells into the market next year,” Miranda Pérez said.

Initially, the company’s solar cells will be made available for residential rooftops, where space is at a premium. With additional production capacity, Oxford PV has set its eyes on commercial rooftops and utility-scale applications. “As a company we are very concerned about the climate crisis, and the best way we can play our part is to deploy this technology as quickly as we can,” said Miranda Pérez.

As countries commit to reducing emissions to meet U.N. climate goals by 2050, solar power is projected to become more pervasive. “I think tandem technologies will be requisite to hit future solar and climate goals,” Berry said.

“We want to help people understand the huge potential of perovskite-on-silicon tandem technology to boost the efficiency of solar installations and to help the world reach the goal of providing sustainable energy for all,” said Miranda Pérez.

—Mary Caperton Morton (@theblondecoyote), Science Writer

From our perch, surrounded by the undulating sea, we watch a single wave approach. The wind does not roar so much as it pushes. I am recalled to childhood memories of standing on a train platform with my mom as an express line confidently coasts through the station, ruffling our coats as it speeds by and creating just such a push. Today the wind at sea hovers only at about a Beaufort 6—a strong breeze—but it makes me feel small, nonetheless.

The approaching wave is not especially big—I’ve swum with bigger waves, coming face-to-face with rolling masses of water that traveled hundreds, if not thousands, of kilometers to meet me. But it’s not small either, and in this moment, I am overcome by the same sensation of being immersed in the sea and watching an oncoming wave. This time, though, as I track the propagating undulation, I am perfectly dry, dressed not in a swimsuit, but in grimy jeans, worn boots, and a spectacularly tacky, deli mustard–yellow Hawaiian shirt festooned with grape bunches.

If seeing a wave that traveled across the ocean to meet you is a miracle of nature, then watching that wave roll by without so much as adjusting your balance is a miracle of engineering.Now the wave is here, an azure mass of water rolling toward us. As it surges and contorts around the incongruous steel structure supporting us above the water, the wave becomes unstable and breaks, throwing its celebratory whitecap directly under our feet and wetting our soles. The visible sign of breaking comes with its compulsory auditory signature, a resounding crash, eliciting uncontrollable, inarticulate, and giddy whoops of delight from my colleagues and me.

Our lapse in professionalism draws a rebuke directly from the captain, standing on the navigation bridge 6 meters above our heads, and we snap back to reality: It’s fall 2017, and we are in the middle of the Southern California Bight, participating in a major scientific field study aboard a historic, one-of-a-kind oceanographic platform.

We scurry up a series of steel ladders and return to our duties. Later, as I lie in my bunk—a few meters below the water line—I forgive myself. If seeing a wave that traveled across the ocean to meet you is a miracle of nature, then watching that wave roll by without so much as adjusting your balance is a miracle of engineering. And for that, we can afford some giddiness.

Out at Sea but High and Dry

The Floating Instrument Platform (FLIP) is a unique asset in the U.S. ocean research vessel fleet. Technically, FLIP is not a ship or a vessel; it is a platform. Well, to be precise, FLIP is a very, very large spar buoy, a type of cylindrical float that sits upright at the ocean surface and is specifically designed to respond minimally to surface wave motions.

FLIP lies in its horizontal position as it is towed to a research location off the coast of California. Credit: John F. Williams/U.S. Navy, CC BY 2.0

This 109-meter buoy comprises what looks like the front of a ship that’s had its aft section replaced by a 90-meter-long, 4-meter-wide steel pipe resembling the working end of a baseball bat. In its resting state, FLIP floats lengthwise at the ocean surface. For expeditions, it is towed out to sea and, living up to its name, “flips” 90° to “stand” vertically at the surface.

Flipping is achieved by quite literally scuttling (a nautical term for purposefully sinking) the ballasted tubular end of the platform. This controlled, partial sinking—often with the full complement of personnel and equipment aboard—is executed precisely and expertly by the crew, who must be eternally commended for their perfect record in 390 attempts. Although the whole process takes 20–30 minutes, most of the motion occurs in about 90 seconds, taking the platform from an angle of less than 20° to fully vertical. During this time, crew and passengers execute a slow-motion, Fred Astaire–like dancing-on-the-ceiling routine, sans tuxedoes.

After the flip is complete, the “boat” section perches above the water surface. This section contains most of the usable space and sleeping quarters, which meet the comfort standards that satisfied a 1960s era Navy sailor—the word spartan comes to mind. All the interior scientific laboratory space, a galley, and other workspaces are connected by a network of exterior steel ladders and grates. Together with three foldable booms, they give the platform the appearance of a giant mechanical cephalopod or perhaps the treehouse of Peter Pan’s Lost Boys reimagined for the movie Waterworld.

Conceived, designed, and built between 1960 and 1962, FLIP was originally intended to allow collection of precise acoustic measurements at sea. Frederick Fisher and Fred Spiess almost casually presented their ingeniously engineered platform in a journal publication that ran barely 11 pages. By 1969, FLIP had been modified with booms—the arms of the aforementioned cephalopod—to facilitate additional science, and it was being used for major field campaigns.

FLIP was so well engineered to remain motionless amid the waves that during a deployment in the northern Pacific in late 1969, the entire crew had to abandon the platform after 3 days of confinement inside without any power. Tom Golfinos, FLIP’s long-serving captain, and esteemed oceanographer Robert Pinkel, both of Scripps Institution of Oceanography, recounted to me that large Pacific swells overtopped the platform, reaching 15 meters above the still water line and knocking out power. As it had been designed to do, FLIP simply stood impassive as these massive waves broke around it, vindicating its designers but terrifying its occupants.

Among its travels through the remainder of the 20th century and the early 21st century, FLIP was towed from San Diego to Barbados, drifted near the Hawaiian Islands, and was lashed by stormy seas off the Oregon coast. All the while, it provided exactly what Fisher and Spiess envisioned: a stable platform from which to make precise measurements at sea.

A Critical and Charismatic Buoy

The greatest challenge to measuring ocean properties has always been, well, being on the ocean.The beauty and genius of FLIP is that it isolates us from the ocean. The greatest challenge to measuring ocean properties has always been, well, being on the ocean. It is remote, dangerous, alternately cold and hot, wet, salty, and always moving. In an almost metaphysical way, this colossal steel tube allows humans to exist immersed within the ocean while protected from its tantrums.

The physical concept and engineering practice of deploying spar buoys for scientific expeditions were not novel in the early 1960s. But designing a spar buoy to hold scientific expeditions was a boundary-pushing step. The ambition and spirit that Fisher and Spiess captured in their design, which expanded over the platform’s decades of use, helped propel science, exploration, and discovery across the ocean sciences for more than half a century.

In my field of air-sea interactions alone, FLIP contributed to many discoveries. For example, it helped reveal how swells generated by distant storms travel across vast ocean basins, and it enabled scientists to make very accurate measurements of atmosphere-ocean transfers of energy and material (gas), information that remains widely used in numerical weather and climate prediction systems. More recently, scientists aboard FLIP directly measured fine-scale currents and wind patterns within centimeters to millimeters of the sea surface using techniques previously confined to controlled laboratory experiments.

In addition to being a supremely useful platform for scientific study, it was a charismatic buoy—and quite frankly, there are not many charismatic buoys. Simply put, it was interesting to think about, talk about, or just look at, and it left an impression on almost everyone who saw it, let alone on the “Flippers” who have been aboard during a flip.

Once, shortly after my time aboard FLIP, I launched into a lengthy explanation of my research when a man I was chatting with asked about my work. Seeing the glazed look come over his eyes (which speaks more to the quality of my explanation), I changed tack and just showed him a picture of FLIP to illustrate what I “do.” Immediately, his interest returned as he recognized FLIP and recounted how he had learned about it in his fifth grade science class. Indeed, FLIP was a tangible icon with which many in the science-interested public identified.

A Month Aboard a Most Unusual Platform FLIP is a very large spar buoy: It sits upright at the ocean surface and is specifically designed to respond minimally to surface wave motions. The author took this photo of FLIP’s “face” during the 2017 CASPER field study from the end of one of the platform’s three foldable booms, aptly named Face Boom. Credit: David G. Ortiz-Suslow

In October 2017, with a freshly minted Ph.D. in applied marine physics, I spent about 35 days aboard FLIP, and it definitely made a lasting impression on me as well. I was aboard as part of the science team for the U.S. Navy–funded Coupled Air-Sea Processes and Electromagnetic ducting Research (CASPER) program, which involved an interdisciplinary and international cohort of scientists from several academic universities and federal research laboratories. The scientific goal of CASPER was to better understand how the atmosphere and the ocean interact, as well as how this atmosphere-ocean coupling affects electromagnetic energy traveling in the marine environment. The CASPER science team had conducted a field campaign offshore North Carolina in 2015 and then commissioned FLIP for its West Coast campaign during fall 2017.

FLIP bobs; it does not translate. This difference in motion mitigates sea sickness yet leaves passengers with the uncomfortable sense that they’ve been marooned at sea.In some ways, being aboard FLIP was like scientific cruises aboard more horizontal research vessels. Ship life revolved around your watch, the designated period when you do the three primary shipboard activities: work, wait, and eat (sleep, the sanctified fourth activity, is done off watch). Also similar is how you are continually steeped in the aromas of fresh paint, burnt diesel, and brine.

However, in many other ways, time aboard FLIP is not like any other research cruise. FLIP bobs; it does not translate (i.e., move under its own propulsion). This difference in motion mitigates sea sickness yet leaves passengers with the uncomfortable sense that they’ve been marooned at sea. Also, all the livable space is vertically stacked, with hallways being replaced by ladders, which made simply going to bed a challenging multistep process.

After donning class IV laser safety goggles—because of the fascinating nighttime experiments your colleagues are running outside—and noise-blocking earmuffs, you climb down three exterior ladders, make your way through the generator room (hence the earmuffs), and maneuver onto a ladder extending down into the darkness of the spar, or tube, section of FLIP. Through a bulkhead hatch at the bottom of this ladder is yet another ladder to scale down—but don’t forget to first secure the hatch, quietly, without waking up sleeping scientists. Then, finally, you can climb into your own bunk and try to fall asleep to the sound of waves, hoping that you don’t have to use the head (bathroom) some 12 meters above you in the middle of the night.

Its peculiarities and inconveniences aside, FLIP was essential for achieving the objectives of CASPER because we needed a stable vantage from which to make measurements, which FLIP offered, especially compared with typical oceangoing ships. The data we collected from FLIP in 2017 have already given us new, fundamental insights into these physical processes.

For example, we are developing new tools to understand how electromagnetic signals propagate differently in various marine atmospheric conditions, techniques that are important for improved maritime communication and shipboard detection of low-flying objects for national security interests. We are also discovering how ocean internal waves leave distinct imprints on the atmosphere through complex and previously unknown mechanisms, and are getting a firmer grasp of the influence of ocean surface waves on atmospheric processes and atmosphere-ocean exchanges that regulate weather and climate. The CASPER team is also using our measurements to inform and validate sophisticated numerical models to help understand these processes and to generalize and translate our findings to other ocean conditions.

The Sun Sets on FLIP

My time aboard FLIP was short, but being part of the platform’s legacy has been a truly humbling experience.My time aboard FLIP was short, but being part of the platform’s legacy has been a truly humbling experience. Barring a major intervention, the fall 2017 cruise was FLIP’s last. In September 2020, the U.S. Navy ended its support of the platform, and its era of operational use came to an end. Although the pandemic was not the cause of this eventuality, it meant FLIP’s transition to emeritus status came without an opportunity for a public good-bye or any well-deserved fanfare.

Similar to the now defunct Arecibo Observatory in Puerto Rico, FLIP was a creation from a bygone era. Its drift into the sunset comes as research priorities and interests in the Earth sciences are shifting. FLIP was all steel and analog components, but the future will be built with lightweight alloys, carbon fiber, and autonomous systems. There is, of course, the understandable reality that exploring new horizons requires new technologies and that resources to support these explorations are finite.

In short, everything has an expiration date—not even a Hollywood credit helped Arecibo in the end. However, like its Boricua cousin of the planetary sciences, FLIP’s legacy goes beyond the innumerable discoveries it enabled, embodying human ingenuity, curiosity about the natural world, and the drive to witness its unperturbed beauty.

FLIP’s history and significance in oceanography are being actively discussed in the scientific community. My reflection here is only one perspective on a career that spanned decades and involved countless individuals. Given that my experience with FLIP came from its last chapter, I feel it is important to recognize the giant upon whose shoulders I and other researchers have stood. That giant comprised not so much the platform itself, but the engineers and shipwrights who designed, built, and maintained it; the venerable and irreplaceable Capt. Tom Golfinos, whose knowledge, memories, and stories weave an oral history of the past half century of developments in oceanographic science; and numerous full-time crew over the years, including David Brenha and John Rodrigues, who made the 2017 cruise possible. In spirit, if not by name, I would recognize the pioneering scientists who pushed the boundaries of oceanic exploration, inspiring the generations of scientists who followed them. These people and others made my time aboard FLIP possible—my time to bob above the ocean, watch the waves, and whoop as they passed—all without so much as a jostle or a wobble in my feet.

Author Information

David G. Ortiz-Suslow (dortizsu@nps.edu), Naval Postgraduate School, Monterey, Calif.

The coastal ocean is an extraordinarily energetic place where water and sediments are always in motion. More than a third of the human population lives near coastline globally, and we are collectively dependent on the coastal ocean for subsistence, commerce, and recreation. Rising sea levels and increasing intensity of storms are just two consequences of climate change that are influencing and will continue to influence the dynamics of coastal ecosystems. It is these dynamic physical characteristics and important mutual influences that make the coastal ocean critical to study but equally challenging to observe.

Miniaturized biologging devices can make oceanographic measurements and are suitable for small diving marine animals like seabirds.Oceanographers who study coastal ocean processes face a cost-benefit trade-off when planning sampling efforts. Surveys from oceanographic vessels provide opportunities to take measurements over broad areas, but time constraints, ship costs, and vessel drafts limit surveys. In contrast, instruments mounted on moorings can measure long-term time series, but only at discrete strategic locations. Autonomous underwater vehicles (AUVs) offer a mobile and continuous sampling approach, but AUVs are expensive to deploy and maintain, and strong currents, waves, and salinity gradients can reduce maneuverability or prohibit sampling through exceptionally dynamic regions.

Biologging—attaching miniature sensors to animals—is an emerging method for making long-term, low cost, and widely distributed autonomous measurements of the environment [Biuw et al., 2007; Harcourt et al., 2019]. Marine animals like seabirds and seals often access hard to sample locations, and they do so under their own power. Advances in data transmission and sensor technologies are facilitating the development of miniaturized biologging devices that can make oceanographic measurements and are suitable for small diving marine animals like seabirds.

Oceanographic Measurements from Cormorants

The Cormorant Oceanography Project, initiated in 2013, is advancing biologging tag technologies for use with cormorants to measure in situ oceanographic conditions. Cormorants and shags make up a family (Phalacrocoracidae) of about 40 species of birds that inhabit coastal oceans and inland waterways from the tropics to high latitudes. Marine cormorants typically forage along the seafloor at depths up to 80 meters, and they can make more than 100 dives each day. Between dives, cormorants rest on the sea surface, so their movements allow both water column and surface conditions to be measured with biologging.

The biologging tags we currently use are equipped with small, low-power, fast-response sensors to measure water temperature, conductivity (for water salinity levels), and pressure (for water depth). Each tag also features an inertial measurement unit (IMU) to monitor acceleration and orientation. A GPS unit, triggered when a bird surfaces, provides locations for georeferencing measurements, and solar cells recharge the tags’ batteries (at the time of writing, some tags have been transmitting continually for more than 2 years). The sensors collect large volumes of data that are transmitted and retrieved using two-way cellular communications. Cellular communications also allow us to transmit new sampling programs to the tags (Figure 1).

Fig. 1. The Cormorant Oceanography Project uses two-way cellular communications with biologging tags to relay data. While foraging, cormorants make consecutive dives and collect vertical profiles of temperature and salinity, and they provide depth soundings. GPS readings and accelerometer data collected between dives, when birds rest and drift at the surface, provide measurements of surface current velocity and surface gravity waves. Colored dots show water temperature data collected by a diving cormorant in the Columbia River estuary in 2019, where temperatures ranged from about 11°C near the bottom to 19°C at the surface. The data inset shows vertical velocity measured by an accelerometer in a tag deployed on a floating bird in the O. H. Hinsdale Wave Research Laboratory at Oregon State University. Credit: Vexels (flying cormorant image)

The data provide measurements from unsampled dynamic coastal marine environments, allowing us to improve model predictions.We are processing tag sensor data to obtain fundamental information about vertical temperature and salinity profiles, bottom soundings (which measure bathymetry), surface currents, surface gravity wave statistics (which characterize wave motions at the water-air interface), and air-sea temperature contrasts (which help us to understand ocean-atmospheric coupling). The data provide measurements from unsampled dynamic coastal marine environments, allowing us to correct uncertainties in boundary conditions and parameters of ocean models and thus to improve model predictions in a process known as data assimilation.

Processing bottom soundings obtained from pressure records gathered during cormorant dives requires disentangling bird behavior from the data. For example, we use dive shape to distinguish benthic (seafloor) dives from dives to intermediate water depths, which reduces uncertainty in the bottom sounding data.

For information about surface currents and surface gravity wave statistics, we use consecutive GPS fixes and high-frequency IMU measurements. Compiling this environmental information requires using the IMU data to distinguish active bird behavior (e.g., flying and paddling) from drifting passively on the ocean surface.

Measuring well-resolved temperature and salinity profiles is theoretically straightforward with data from diving birds, although engineering challenges remain. These challenges include designing a sensor housing that produces temperature measurements with a short response time and developing a small conductivity sensor that produces stable measurements for the duration of tag deployments. We are working with tag manufacturers to iteratively develop and test tag and sensor prototypes to improve profile measurement capabilities.

Finally, contrasts in air and sea temperatures can theoretically be measured at the beginning of dives when birds first submerge and at the end of dives when they surface. Precisely measuring air temperature is more challenging than measuring water temperatures, however, so improving determination of these contrasts is a long-term goal of the project.

Outfitting Cormorants in the Columbia River Estuary

Insights into Marine Bird Ecology

Cormorants, which forage in biologically rich nearshore areas, can be used as indicators of ecosystem health. In particular, cormorants tend to follow boom-bust cycles that track the availability of the fish they eat. Yet the specific ecological role of many cormorant species is unclear.

Like other predators, cormorants are often viewed as being in direct competition with humans, and they are vilified, persecuted, or simply ignored. The animal movement data collected through the Cormorant Oceanography Project, in tandem with oceanographic data, provide important basic information on the birds’ foraging ecology, distributions, and migrations. This information, in turn, is valuable for efforts such as marine spatial planning, in which human activities are coordinated to balance demands for development with the need to protect the environment.

In summer 2019, we fit 22 Brandt’s cormorants (Phalacrocorax penicillatus) captured from roosting sites near the mouth of the Columbia River, on the Oregon-Washington border, with biologging tags using backpack-style harnesses. At about 40 grams, these tags weighed less than 3% of a cormorant’s body mass, minimizing effects on the birds’ normal activities [Fair et al., 2010].

Brandt’s cormorants are fish-eating foot-propelled pursuit divers—meaning they chase prey—and are endemic to the California Current, a coastal ocean current flowing between British Columbia and Baja California. We found that Brandt’s cormorants are generally loyal to their roosting sites and foraging areas. The Columbia River estuary was their core habitat during the summer, but individual birds moved both north and south. Thus, our tagged birds collected concentrated data near the mouth of the river as well as along much of the Pacific coast of North America (Figure 2a), diving as far as 79 meters below the sea surface. This study allowed us to try out various tag types and collect oceanographic data to use in an assimilative model within a well-studied and highly dynamic estuary system (Figure 2b).

Fig. 2. (a) Cormorants tagged at the mouth of the Columbia River (near the Washington-Oregon state line) traveled long distances along the Pacific coast. About 325,000 dives by these birds (red dots) have been recorded to date. (b) Transect of temperature profiles (color-coded dots) collected by a bird at the mouth of the Columbia River during an ebbing tide over a period of about 1.8 hours. The bird reached the bottom at easting distances less than −2.2 kilometers, but not at easting distances greater than −2 kilometers. (c) Locations of water column profiles, color-coded by maximum dive depth, collected by tagged Brandt’s cormorants at the mouth of the Columbia River. More than 85,000 profiles have been collected in this region to date. Arrows indicate surface current velocities (the maximum shown here is 1.1 meters per second) estimated from the tagged birds, drifting at the surface between dives, along the transect shown in Figure 2(b). The inset shows a tagged Brandt’s cormorant. Click image for larger version. Credits: Adam Peck-Richardson (inset); National Geophysical Data Center (bottom depth and bathymetric contours).

Because of the birds’ autonomy in where and when they dive, the data they collect are heterogeneously distributed, making it difficult to interpret oceanographic information with analysis methods that require regular sampling intervals (e.g., averaging data over a long time at one location or performing a spectral analysis on a time series of data). Instead, we are applying techniques from inverse modeling and data assimilation and are using a numerical ocean model to fill gaps between data points and to infer ocean properties not directly observed.

The ability to estimate bathymetry from frequent, autonomous biologging measurements may have a practical utility for safe ship navigation and channel maintenance.For example, we are inferring seafloor bathymetry from our biologging data. Coastal bathymetry is often poorly known, and it is always changing. The mouth of the Columbia River is continually being filled in with sand, which forms unpredictable shoals and channels [Stevens et al., 2020], and annual dredging operations remove at least 1.5 meters of sediment from navigational channels to keep them safe for commercial shipping. The ability to estimate bathymetry from frequent, autonomous biologging measurements thus may have a practical utility for safe ship navigation and channel maintenance.

Instead of trying to determine the shape of the seafloor directly from the scattered data coming from the cormorants, we apply data inversion. First, we consider various model seafloor profiles using a method developed by Evensen [2009], in which a sample of randomly generated candidate bathymetries is run through a numerical model to obtain a least squares–based statistical relationship between these bathymetries and the observational surface current data [Wilson et al., 2010]. Then this relationship can be inverted (back-calculated) to estimate the bathymetry that best fits the real data.

We are currently testing this inverse approach for use with distributed biologged measurements of surface currents. In the future, we may use similar techniques to determine parameters other than bathymetry, such as the strengths of cold-water currents that upwell from the depths of coastal oceans, for which we could make use of temperature data collected by the cormorants.

Upgrading Tag Technology

Although the tags we have used to date have proven effective, continued advances in tag attachment methods, targeted sampling (recording data when birds are foraging or resting on the sea surface), and battery miniaturization, as well as in tag solar panels, sensors, electronics, and communications, would help to optimize biologging devices for improved data collection and for use with different species.

Several cormorants are seen here in silhouette. Continued technical advances are needed to optimize biologging devices for use with varying species. Credit: Adam Peck-Richardson

Biologging tags should be as small as possible relative to the mass of the animals carrying them, and they should be positioned to have negligible impacts on the animals’ energy expenditure as they fly or dive. Whereas high-latitude cormorants, including Brandt’s, tend to have larger bodies (2.5 kilograms), tropical cormorants can be as small as 360 grams, necessitating further tag miniaturization.

Furthermore, although the use of cell phone technology allows tags to transmit large amounts of data, data transmission is possible only in locations with cell phone coverage. The tags also require occasional electronic updates to keep up with consumer-driven advances in cellular technologies (e.g., 5G).

Finally, considering the birds’ autonomy, the biologging data they collect pose challenges to coordinating near-real-time data processing, archiving, and distribution. Maintaining data provenance, including measures of uncertainty associated with behavioral biologging data (as distinct from uncertainties in data obtained by conductivity-temperature-depth instruments), requires flexibility that has yet to be built into many oceanographic data repositories.

A Work in Progress

Since 2019, we have collected more than half a million dive profiles from three species of cormorants foraging in a range of near-shore habitats (Figure 3): In addition to the Brandt’s cormorants from the Columbia River estuary, we have fit biologging tags to pelagic cormorants to study the water near Middleton Island, Alaska, and to Socotra cormorants in the Arabian Gulf off the United Arab Emirates. We are now evaluating these data and comparing them to numerical models.

Fig. 3. Dive depths from biologging cormorants are indicated here by color-coded red dots, with species photos shown in the insets. (a) Eighteen pelagic cormorants (P. pelagicus) made 71,407 nearshore dives during a 2-week deployment near Middleton Island in the Gulf of Alaska in July 2020. (b) Eleven Socotra cormorants (P. nigrogularis) made 30,611 dives in the Arabian Gulf between November 2020 and January 2021. Credits: (a) Google Earth (shoreline), NOAA (bathymetry), Brendan Higgins (inset photo); (b) NOAA (bathymetry), Sabir Bin Muzaffar (inset photo)

Among other findings, these comparisons have revealed errors in models of temperatures for deep, cold ocean water that upwells to the surface, a common source of uncertainty in regional-scale ocean models on the U.S. West Coast. Future work will investigate other uncertainties about how coastal ocean environments function. For instance, we will use tag data from Socotra cormorants in the Arabian Gulf to diagnose sea surface temperature biases that occur in models and that are commonly associated with uncertain atmospheric forcing (e.g., the influence that dust storms exert on incoming shortwave radiation) [Lorenz et al., 2020].

Although we have made much progress in tag development, our near-term goals are to improve the response times of the temperature sensors we use, to test and improve our conductivity sensors, and to put smaller versions of these tags through trials. Over the next couple of years, we also aim to scale up our tag deployments through international collaborations and through the development of a global cormorant oceanography network. Furthermore, we are building an automated data pipeline through the Animal Telemetry Network to provide our biologging data to the oceanographic research community in near-real time.

With these efforts, we are continuing to expand the range of techniques and data that scientists have at their disposal to better understand highly dynamic—and highly important—coastal ocean environments.

Acknowledgments

The Cormorant Oceanography Project is sponsored by the U.S. Office of Naval Research. Dylan S. Winters (Oregon State University) processed the data for and produced Figures 1, 2, and 3. H. Tuba Özkan-Haller and Donald E. Lyons (Oregon State University), Reginald Beach (Office of Naval Research), and Christopher Wackerman (Naval Research Laboratory, Stennis, Miss.) provide project oversight and guidance. Sabir Bin Muzaffar (United Arab Emirates University) leads the tagging efforts for Socotra cormorants. The biologging tags we use were developed by Ornitela, Ornithology and Telemetry Applications, Vilnius, Lithuania. The 2014 data collection in the Columbia River was supported by Bird Research Northwest field crews, with special thanks owed to Daniel Roby, Yasuko Suzuki, Alexa Piggott, Peter Loschl, Kirsten Bixler, John Mulligan, and Anna Laws and with logistical assistance from Real Time Research. In 2019, efforts in the Columbia River were supported by Stephanie Loredo, Jason Piasecki, Emily Scott, Daniel Battaglia, Margaret Conley, Sam Stark, Tim Lawes, and Olivia Bailey (all at Oregon State University). Middleton Island data collection in 2020 was facilitated by Scott Hatch (Institute for Seabird Research and Conservation) and Jenna Schlener (McGill University), and field efforts were supported by Jillian Soller and Brendan Higgins (both at Oregon State University). Work with birds was approved by the Animal Care and Use Committee of Oregon State University, United Arab Emirates University, and the Office of Naval Research Bureau of Medicine and Surgery and by permits from the U.S. Geological Survey, Oregon Department of Fish and Wildlife, Washington Department of Fish and Wildlife, and Alaska Department of Fish and Game.

The near-Earth space is filled with charged particles that come from two sources, the solar wind and the Earth’s upper atmosphere. A new article published in Reviews of Geophysics investigates the relative importance of the two sources of charged particles and their effects on plasma dynamics, especially the process of magnetic reconnection, which is responsible of coupling the Sun magnetic field to the Earth’s magnetic field. Here the authors explain what ionospheric ions are, what we understand about them, and what there is still to discover.

What are ionospheric ions and where do they come from?

Up in the higher altitudes of the atmosphere is the ionosphere where there are increasing number of charged particles ionized by the Sun’s radiation. These “ionospheric ions” reflect the make-up of Earth’s atmosphere: ionized hydrogen, oxygen, nitrogen, and helium can all be found in this region of space.

Electromagnetic processes can give some of these ions enough energy to escape the Earth’s gravity potential, and magnetic field lines guide these particles in their journey to outer space, where they are further energized.

If that escaping rate remained constant, it would take around 1,000 billion years to deplete the atmosphere.Most of these particles do not go back to the atmosphere, and the net average escaping rate is roughly 5,250 tons per year.

This sounds like a large number, but it is actually a very small fraction of the Earth’s atmosphere. If that escaping rate remained constant, it would take around 1,000 billion years to deplete the atmosphere.

Although the loss of ionospheric ions is small, what impact do they have on near-Earth space?

The near-Earth space environment is known as the magnetosphere, i.e., the region where the Earth’s magnetic field dominates over the Sun’s magnetic field. The magnetosphere is like a magnetic bubble immersed in the heliosphere, the region where the Sun’s magnetic field dominates within the solar system. When certain conditions are met, the coupling between these two regions becomes very efficient, allowing large amounts of energy and particles from the Sun to enter the magnetosphere, generating geomagnetic storms and a variety of space weather phenomena.

The magnetosphere is constantly filled by particles from the solar wind and the Earth’s ionosphere.The magnetosphere is constantly filled by particles from two sources: the solar wind and the Earth’s ionosphere.

The relative contribution of the two sources is variable and roughly of the same order of magnitude, but their properties are quite different.

Solar wind ions entering the magnetosphere are composed mainly of H+ ions and a few percent of He++ ions. Ionospheric ions are initially cold, i.e., have lower thermal energy than the solar wind, and often contain large amounts of O+ ions in addition to the much lighter H+ ions.

Ionospheric ions circulate in the magnetosphere following magnetic field convection and are the origin of various magnetospheric populations, including for instance plasmaspheric plumes or the warm plasma cloak. These populations eventually reach the interface between the magnetosphere and the solar wind, i.e., the magnetopause, and change its properties. Therefore, depending on the time-history (hours to days) of the solar wind and the magnetosphere, the magnetopause changes its location and properties, potentially affecting the efficiency of the coupling between the two regions.

Artist rendition of the MMS mission orbiting in formation the Earth’s magnetosphere, to study its interaction with the solar wind. Credit: NASA/Goddard Space Flight Center (Public domain)

How have recent observations and models advanced our understanding of the behavior of ionospheric ions?

The NASA Magnetospheric Multiscale (MMS) mission has revolutionized our understanding of magnetic reconnection, the main process at work for coupling the Earth’s magnetosphere to the solar wind. Its spatial and time resolution has enabled us to understand how different charged particle populations are energized by the reconnecting magnetic fields.

Thanks to that mission, combined with high-performance numerical modeling, we now understand much better how ionospheric ions modify the reconnection process at a microphysical level. Ionospheric ions circulating in the magnetosphere are accelerated at reconnection sites and constitute a significant sink of energy for the reconnection process. In addition, depending on the ion mass, initial energy, and where the ions are entrained in a reconnection site, different energization mechanisms, some of them more efficient than others, come into play.

Main regions of the Earth’s magnetosphere. Ionospheric ions (light blue) escape and fill the outer magnetosphere until they exit the Earth space environment. Credit: Toledo-Redondo et al. [2021], Figure 1What are some of the unresolved questions where further research, data gathering, or modeling is needed?

We still understand relatively little about how magnetic reconnection microphysics shapes the magnetosphere system as a whole.We still understand relatively little about how these recent discoveries about magnetic reconnection microphysics shape the magnetosphere system as a whole.

The impact of cold ions is still an open field of research, as cold ions introduce a new length-scale and many plasma processes depend on the coupling between different scales.

The MMS dataset is continuously growing and only a portion has been extensively analyzed. Combining it with other mission datasets, such as for instance Cluster or THEMIS, to perform large statistical studies in the solar wind parameter space, will shed light about how the system reacts to ionospheric ions on a global scale.

Moreover, global 3D magnetospheric numerical models coupled to the ionosphere are very advanced nowadays and will also deepen our understanding of the global picture of ion circulation and energization in the magnetosphere in response to different kinds of solar activity.

There is yet another ionospheric population, which is even less understood: cold electrons. They also outflow from the ionosphere, and these are even harder to characterize than cold ions. Electrons play crucial roles on magnetic reconnection and wave generation in the magnetosphere. So far, because of the immense difficulty of observing these low-energy electrons, the effects of cold electrons remain largely unexplored.

Particle-in-cell simulation of magnetic reconnection, the main coupling process between the solar wind and the Earth’s magnetosphere. The color coding represents plasma number density. The magnetic field lines (solid black lines) break and reconnect at the Electron Diffusion Region, generating reconnection outflow jets. Credit: Toledo-Redondo et al. [2021], Figure 13—Sergio Toledo (Sergio.Toledo@um.es; 0000-0002-4459-8783), University of Murcia, Spain and University of Toulouse, France; Mats André (0000-0003-3725-4920), Swedish Institute of Space Physics, Sweden; Nicolas Aunai (0000-0002-9862-4318), Laboratoire de Physique des Plasmas, France; Charles R. Chappell (0000-0002-1703-6769) Vanderbilt University, USA; Jérémy Dargent (0000-0002-7131-3587), University of Pisa, Italy; Stephen A. Fuselier (0000-0003-4101-7901), Southwest Research Institute and University of Texas at San Antonio, USA; Alex Glocer (0000-0001-9843-9094), NASA Goddard Space Flight Center, USA; Daniel B. Graham (0000-0002-1046-746X), Swedish Institute of Space Physics, Sweden; Stein Haaland (0000-0002-1241-7570), Max-Planck Institute for Solar Systems Research, Germany, University of Bergen and The University Centre in Svalbard, Norway; Michal Hesse (0000-0003-0377-9673), NASA Ames Research Center, USA; Lynn, M. Kistler (0000-0002-8240-5559), University of New Hampshire, USA; Benoit Lavraud (0000-0001-6807-8494), University of Bordeaux, France; Wenya Li (0000-0003-1920-2406), National Space Science Center, China; Thomas E. Moore (0000-0002-3150-1137), NASA Goddard Space Flight Center, USA; Paul Tenfjord (0000-0001-7512-6407), University of Bergen, Norway; and Sarah K. Vines (0000-0002-7515-3285), Johns Hopkins University Applied Physics Laboratory, USA

Autonomous vehicles are jauntily steering through the streets of more and more cities, but the navigation systems in these vehicles remain an evolving technological concept. As companies vie for the rights to urban terrains, they typically use sensors based on optical properties (like light waves and video) or radio waves to map and navigate the environment. These options may not provide the best coverage, especially in bad weather. A team of researchers at the University of Michigan is turning to nature to develop something better.

“Animals have the amazing ability to find their way using sound,” said Bogdan Popa, an assistant professor of mechanical engineering at the university and principal investigator on the project. “We want to develop a sensor that uses sound like animals.”

Previous efforts with sound have failed because sound waves do not travel as far in air as light and radio waves. In fact, current ultrasound sensors have a range of only 1 meter and produce low-resolution maps.

Popa plans to leverage knowledge from nature to advance this technology.

Dolphins, bats, and whales use echolocation, a technique where a sound pulse is emitted into the environment. When the pulse encounters an object, it bounces off and sends reflections back to the animal to decipher. Using this approach, animals can navigate their terrain, find food, and avoid predators—all of which happens very quickly.

Popa believes echolocation offers a tantalizing new opportunity that will allow autonomous vehicles to operate in an uncertain world under inclement weather conditions while retaining their autonomy.

The Sensor of the Future

Sound has a limited range as it travels through the air. To propel sound waves more efficiently, Popa and his team constructed an acoustic lens using passive and active metamaterials.

Similar to an optical lens, the acoustic lens consists of two engineered pieces of patterned plastic that are capable of focusing ultrasonic sound waves (35–45 kilohertz) in any desired direction with only the slightest deformation. This capability means that the lens can be fixed to the vehicle and does not need to be cleaned or realigned. With only minor adjustments, the lens can project a focused wave in almost any direction. Popa likens this new sensor to a laser beam compared to traditional sound applications that are more like an incandescent light bulb.

The team also developed a process to analyze the vast amount of information contained in the returning echoes. To do this, they made the project even more multidisciplinary, turning to computer science to interpret biological sensory signals. The Michigan team developed a convolutional neural network, consisting of individual deep learning algorithms that can differentiate, weigh, and assign importance to self-labeled images.

“Using some experiments with dolphins to understand their behavior, we developed a series of neural networks,” said Popa. “Each neural network is specialized to recognize one object, like a type of fish, a threat, rocks, etc.”

For the first stage of the study, the team plans to develop a series of neural networks. Each network will be trained to interpret the returning echoes for a specific object and determine whether the object is present in the environment and its likeliest position.

“This is a modular approach that is more decentralized,” said Popa. “It is easier to do as opposed to one algorithm that has to provide all the data.”

Once identified, the object will be placed on the map in front of the vehicle. Popa plans to simultaneously map the environment with multiple neural networks to identify many different objects to recreate the world before the vehicle.

Next Steps

Once a network is trained, Popa believes it will be able to provide an answer to questions about location almost instantaneously. The team plans to layer neural network after neural network to provide the power of interpretation for an array of incoming echoes.

“For me, the most exciting part is understanding how the natural world does what it does in such an efficient way. We hope to replicate or equal the performance of these biological systems.”Although the team is still acquiring the data to train the various algorithms in the neural networks, they plan to test the system using virtual simulations. If all goes well, they will release the new acoustic sensor-based navigation system into the real world to see how it helps autonomous vehicles navigate the streets.

“Since this technology is still in the beginning stages, it’s hard to say how it will compare with current sensors,” said Teddy Ort, a Ph.D. candidate in the Computer Science and Artificial Intelligence Laboratory at the Massachusetts Institute of Technology. “If it could provide detailed 3D data at range, it could prove very valuable not only to replace, but perhaps to augment the current sensor suites.” Ort did not contribute to this study.

As the demand for autonomous vehicle technology increases, Popa’s contribution could improve the safety of vehicles navigating every community, large and small.

“For me, the most exciting part is understanding how the natural world does what it does in such an efficient way,” said Popa. “We hope to replicate or equal the performance of these biological systems.”

—Stacy Kish (@StacyWKish), Science Writer

Atmospheric levels of carbon dioxide (CO2) are the highest they’ve been in 800,000 years, and they are rising. Since the beginning of the Industrial Age, CO2 levels have increased nearly 50%. The consequences of increased levels of atmospheric CO2 are numerous and have far-reaching negative impacts, including on agriculture, climate, and human health, among others. To make matters worse, once CO2 is added to the atmosphere, it sticks around for hundreds to thousands of years.

Although increasing CO2 levels affect Earth and much of its life, plants are particularly sensitive to variations in these levels. They rely on the gas for survival, and changing carbon concentrations can affect everything from their growth rate to their nutritional value to their toxicity. Some hardy species are benefiting from current conditions, including an invasive plant known as famine weed (Parthenium hysterophorus). New research published in Nature Plants shows that one type of this toxic weed became more lethal under current CO2 levels, possibly making it more competitive and invasive.

Plants in a Carbon-Rich Atmosphere

“The question was, Why is one [famine weed biotype] spreading all over the place and the other is just kind of hanging out?”Famine weed is a flowering plant native to Central and South America but has become an invasive species in parts of Africa, Australia, and the Indian subcontinent. Interestingly, two biotypes of famine weed were introduced into Australia in the 1950s, but only one flourished in its new home.

“The question was, Why is one spreading all over the place and the other is just kind of hanging out?” asked Julie Wolf, a plant physiologist at the U.S. Department of Agriculture and the corresponding author of the study.

According to the international research team that examined how the increase in atmospheric CO2 over the past 170 years has likely changed the biochemistry of the two types of native famine weed plants, the answer lies in one of the organism’s less appealing traits. Famine weed produces a particularly nasty, carbon-based toxin called parthenin that prevents other plants from growing around it. It can also cause severe skin irritation and asthma in humans. This toxin is thought to contribute to the prolific spread of the plant by killing competing plants and possibly deterring predation.

“The current invasiveness and nastiness of [the invasive biotype] is probably being exacerbated to some degree by current CO2 levels.”At current CO2 levels, the invasive biotype produced more toxin by mass than the noninvasive biotype and more toxins than at preindustrial carbon levels, Wolf said. “The current invasiveness and nastiness of [the invasive biotype] is probably being exacerbated to some degree by current CO2 levels,” she said. With the increasing availability of carbon, it is easier for the invasive biotype to grow larger and produce more carbon-based toxin, possibly leading to its increased competitiveness, Wolf explained. The chemistry of the invasive biotype has probably adapted to use high levels of CO2 to its advantage, the authors say.

Focusing on the Future, Overlooking the Past

Further tests will be needed to see how famine weed fares as CO2 levels continue their upward climb, but the implications of its current adaptation are much broader. Danielle Way, a plant physiologist and associate professor at Western University who was not a part of the study, said this research illustrates that the selective pressure of the current level of atmospheric carbon may have already begun to favor carbon-adapted plants. These adaptations may have gone unnoticed because plant-response research has focused on future CO2 changes over the change we have already created.

“What have we already done to our system that is maybe passing under the radar because we’re really focusing on those even larger changes in CO2 and climate that we expect over the next 50 to 100 years?” Wolf asked. Unfortunately, the plants best equipped to thrive in these new conditions may not be the most beneficial to humans. “A plant that is successful in terms of persisting persists in the best way it can, and that might not match what we want from the plants,” said Wolf.

“A lot of times, people uniformly think that CO2 will be a benefit for plants, but it’s very much more diverse and varied.”That doesn’t mean only increased toxicity. Other research studying plant responses in even higher CO2 environments has found that for many food crops, although the size of the plant increased, its nutritional value decreased. When grown under high levels of CO2, species like wheat and rice end up with less protein and lower concentrations of micronutrients even though the individual grains can be larger in size.

Predicting exactly which plants will flourish in an increasingly CO2-rich world is difficult. “A lot of times, people uniformly think that CO2 will be a benefit for plants, but it’s very much more diverse and varied,” Wolf said. She hopes that this work will act as an alarm bell, pushing the community to investigate how plants have already changed in our current, carbon-rich atmosphere to learn what the future holds. Otherwise, we risk a planet rendered increasingly inhospitable not only by temperature and climate but also by the species we share it with.

—Fionna M. D. Samuels (@Fairy__Hedgehog), Science Writer

This piece was produced with support from the National Association of Science Writers’ David Perlman Virtual Mentoring Program.

On rotating planets, differential heating between the poles and the equator gives rise to instabilities. These are manifested as transient disturbances (e.g., Earth’s mid-latitude storms) that transport enthalpy poleward, thereby lessening the temperature gradients and quenching the instabilities. Scientists have long sought to understand how the resultant temperature gradients depend on the degree of destabilization, along with other properties of the system. Gallet & Ferrari [2021] develop a scaling law that quantifies these dependencies and shows how meridional temperature gradients respond – weakly – to changes in the forcing. Their scaling theory bounds the utility of the longstanding but ultimately incorrect hypothesis that eddies relax temperature gradients to a state of marginal stability. These new results provide a fully non-linear benchmark for numerical methods used to simulate geophysical flows, for guiding thinking as to the behavior of less idealized flows, and for inspiring aspiring theoreticians.  As Vallis [2021] points out in a companion Viewpoint, extracting order from turbulence is often seen as academic hardscrabble, which makes the fertility of Gallet and Ferrari’s accomplishment all the more remarkable.

Citation: Gallet, B. & Ferrari, R. [2021]. A quantitative scaling theory for meridional heat transport in planetary atmospheres and oceans. AGU Advances, 2, e2020AV000362. https://doi.org/10.1029/2020AV000362

—Bjorn Stevens, Editor, AGU Advances

Since 1997, NASA has successfully landed five rovers on Mars. The rovers have beamed back data that indicate life cannot survive on the Martian surface; we do not know whether life persists below the ground, however. For subterranean life to endure on Mars or elsewhere, microbes would have to convert—or fix—elements from their inorganic form to a usable, organic form. This skill, known as lithoautotrophy, comes in handy for Earth-bound bacteria, too—specifically for microbes living in caves. These cave environments often lack nutrients because of the absence of sunshine and organic material enjoyed by life on the surface.

In a new paper, Selensky et al. try to move us closer to understanding whether underground extraterrestrial life could exist by exploring carbon cycling in the lava caves at Lava Beds National Monument in California. As lava flows from a volcanic eruption, a stiff outer shell eventually solidifies as magma continues to flow inside, creating hollow tubes. Because lava tubes form through volcanism, they are presumed to exist elsewhere in the solar system, making them valuable models for planetary speleology.

In California, the authors examined the carbon sources used by cave bacteria living in biofilms (colorful microbial communities on the cave walls), speleothems, and soil. They compared carbon isotope signatures in bacterial fatty acids to carbon sources outside the cave.

The researchers found that the fatty acids produced by Actinobacteria in biofilms bear isotope signatures that could not derive from outside sources. In other words, the bacteria are fixing carbon in situ. In contrast, bacteria from other cave features, such as the speleothems, assimilate organic carbon derived from the surface.

The results suggest that some bacteria in basaltic cave ecosystems are fixing their carbon, which indicates that the microbes survive independently of the surface environment. The findings challenge the paradigm that all cave microbiota subsist on surface inputs. Furthermore, the authors say the conclusions have significant and positive implications for the search for extraterrestrial life. (Journal of Geophysical Research: Biogeosciences, https://doi.org/10.1029/2021JG006430, 2021)

—Aaron Sidder, Science Writer

Like Earth, Jupiter’s magnetic field channels electrically charged particles into its atmosphere, resulting in the formation of brilliant aurorae near its poles. However, the brightness and variety of Jupiter’s auroral emissions exceed those generated on our planet. Of particular interest are patches of emission that originate from even closer to the poles than the main aurorae, a feature that appears far stronger at Jupiter than at Earth or Saturn.

Emission in the polar region can be fleeting, lasting minutes or sometimes only seconds. The polar auroral area can be further divided into three morphologies: “dark” regions of minimal emission, “active” regions of vigorous emission, and, at the highest latitudes, “swirl” regions of turbulent emission.

NASA’s Juno spacecraft has detected downward particle fluxes that can account for the main emission. However, no such flux has been found that could account for the bulk of the polar emissions, especially those from the swirl regions. Masters et al. propose a mechanism that would not yet have been observed by Juno: magnetic reconnection occurring not far above the Jovian cloud tops.

The authors perform one-dimensional magnetohydrodynamic modeling to track the evolution of individual magnetic field lines in the vicinity of Jupiter’s pole. They model the region starting at the top of the planet’s atmosphere and extending 2 Jovian radii from that point. This region lies entirely below any extant spacecraft observations.

Waves moving through the plasma enter the model domain from above, generated by interactions farther out in the planet’s magnetosphere. The propagation of these waves has the effect of deflecting the idealized magnetic field lines from a perfectly vertical position. This is a small effect, on the order of 0.01°, but it may be sufficient to kick-start magnetic reconnection events between neighboring field lines.

During reconnection, adjacent field lines break and reform in a more energetically favorable configuration. This process releases energy stored within the field, which is carried away by the acceleration of nearby charged particles. The authors suggest downward traveling energetic electrons may be the source of the swirl regions in Jupiter’s polar aurorae.

Finally, the authors suggest that this effect isn’t important at Earth or Saturn because of their weaker magnetic fields. Jupiter’s field is more than an order of magnitude stronger, and the reconnection rate increases by roughly the square of that value. Thus, Jupiter has strong polar aurorae, whereas Earth and Saturn do not. (Journal of Geophysical Research: Space Physics, https://doi.org/10.1029/2021JA029544, 2021)

—Morgan Rehnberg, Science Writer

June to September is known as “the monsoon” in the Southwest. For these few months, rains quench Earth’s thirst, bringing cactus blooms, insect hatches, and the sweet smell of creosote bushes. But sometimes the monsoon doesn’t come.

Over the past 20 years, the average temperature has risen across the Southwest, from California to Colorado, and drought is shifting from a transient condition to a way of life. Torrential rains that hit Flagstaff, Ariz., earlier this month were a blip amid a 26-year long-term drought that’s left the Lake Mead reservoir on the Nevada-Arizona border at its lowest level since the 1930s. In efforts to conserve water, Las Vegas recently banned “nonfunctional” grass, and the Hopi Nation ordered livestock reductions.

Earth is entering a period that some scientists have called the “no-analog future” because climate change has left them unable to use past experience to predict future weather trends, like rain and water availability. But this month, a new monitoring project called the Surface Atmosphere Integrated Field Laboratory, or SAIL, started collecting data that scientists hope will fill holes in hydrology models and guide water policy in this uncertain future.

This platform holds instruments, including a rain gauge to measure the amount of liquid precipitation that falls during the SAIL field campaign in Gothic, Colo. Credit: U.S. Department of Energy Atmospheric Radiation Measurement (ARM) user facility. Photo by John Bilberry, Los Alamos National Laboratory, CC BY-NC-SA 2.0

Over the next 2 years, SAIL will use dozens of instruments—including radar, lidar, cameras, balloons, and other equipment—nestled near the Rocky Mountain town of Crested Butte, Colo., to measure clouds, aerosols, wind, temperature, precipitation, and a wide array of other weather features with greater consistency and frequency than any previous project. Putting all this information together, SAIL scientists hope to learn how much water enters upper Colorado River watersheds through rain and snow as well as what happens to that water as it makes its way downstream to communities like Window Rock, Phoenix, and Las Vegas. This information can improve models of how water moves through mountainous regions worldwide—information that will help communities that depend on mountain runoff.

Opening the Black Box

“They’re taking what was this big black box between the atmosphere and the streamflow, and they’re opening that up.”Scientists have known for years that the amount of water flowing down from mountains is declining as temperatures rise, but Indiana University hydrologist Adam Ward likens the reasons for this decline to a black box. A self-described “SAIL enthusiast” who’s not directly involved in the project, Ward said he’s excited about SAIL because “they’re taking what was this big black box between the atmosphere and the streamflow, and they’re opening that up.”

Opening this black box will require what Lawrence Berkeley National Laboratory geologist and SAIL senior scientist Ken Williams calls “extreme collaboration.” Several government labs and nonprofit organizations are working with nearly a dozen academic institutions to make this multimillion dollar per year venture possible.

“Our work has really embraced what we call a community watershed concept,” Williams said, referring to the wide variety of expertise represented in SAIL. “It’s allowed our collective research team to gather data that ranges from the tops of trees, to soils, to underlying bedrock.” All this information is necessary to build complex hydrological models to predict water availability more accurately in the coming decades.

Aerosols in the Colorado Rockies

Jessie Creamean is an atmospheric scientist at Colorado State University who joined SAIL to research how dustlike particles called aerosols contribute to snow in the Colorado Rockies. Snow is particularly important to water availability in mountainous watersheds because snowpack that builds up during the winter melts slowly throughout the summer and provides downstream regions with a continuous supply of water.

Just as plants germinate from seeds, storms stem from aerosols.Just as plants germinate from seeds, storms stem from aerosols. These tiny particles bring water molecules together to turn clouds into precipitation. As a graduate student working in the Sierra Nevada Mountains in California, Creamean found that aerosols from as far away as North Africa could affect snowfall. Now, she’s excited to characterize the role that aerosols play in the Rockies, not only because of their scientific merit but also because of the role snow plays in her life. “I’m an avid backcountry skier,” she said. “And so a healthy snowpack really affects my happiness in the winter, quite frankly.”

Alejandro Flores is a Boise State University hydrologist and SAIL researcher who’s taking research like Creamean’s and turning it into models to predict precipitation. Although processes that occur in the atmosphere are important for snow, the interface between the land and the atmosphere matters just as much, Flores said. He’s excited about SAIL’s radar system, which, when combined with other instruments, will give scientists a minute-by-minute view of how snow accumulates on the ground and how water enters the soil. Although previous projects have collected similar data, none have collected such frequent readings over as long a period of time as SAIL.

“It’s a new way of doing science, to get the modelers and the observational teams coordinating from day one.”“This topic is one that is very important to me, not only professionally but also personally,” said Flores, who grew up in Colorado. “I know and understand the pressures that are being put on water in the West by things like climate change.”

Ward said the consistency of the project’s data will make it useful for his own research on mountain streamflow. Earth scientists are often stuck tying together observations made by many different groups in many different ways, and the lack of internal consistency makes it difficult to draw conclusions. But with SAIL, scientists will have a complete set of consistent data describing the inner workings of a watershed.

“It’s a new way of doing science, to get the modelers and the observational teams coordinating from day one,” Ward said.

—Saima Sidik (@saimamaysidik), Science Writer

Biogeochemical cycles describe the flow of elements in the Earth systems. They are strongly influenced by biological and anthropogenic activity and, in turn, influence other aspects of the Earth systems and human environment. Biogeochemical Cycles: Ecological Drivers and Environmental Impact, a book published by AGU, demonstrates how biogeochemical cycles developed over time and how they manifest in different environments, and presents new methodologies available to quantify and predict flow of the elements. Here the book’s editors give an overview of our understanding of biogeochemical cycles and summarize current challenges and opportunities for research.

What makes biogeochemical cycles such an interesting field of study?

The biogeochemical cycles of the elements influence most of the abiotic factors that govern life.The biogeochemical cycles of the elements influence most of the abiotic factors that govern life. Studying biogeochemical cycles is important for understanding how natural ecosystems resist Anthropocene stresses, and also for anticipating and modeling the sustainable functioning of human-impacted ecosystems such as agricultural soils.

Example of isotope analysis application to elemental cycles. Credit: Nägler et al. [2020], Figure 8.7 What is the interest of the Critical Zone concept in the study of biogeochemical cycles?

The Critical Zone is a porous skin of the Earth’s land surface extending from the top of the vegetation canopy to the lower limits of freely circulating groundwater (NRC, 2001). It is a useful concept in biogeochemistry because it brings together soils, vegetation, rocks, and water. Geologically speaking, it is a very thin layer, but it is the layer that shelters life, including humans.

Link between structure and function in critical zone. Credit: Moravec and Chorover [2020], Figure 6.1What are some of the challenges in determining cause and effect relationships within biogeochemical cycles?

Earth systems are incredibly complex and interconnected meaning that one change can trigger multiple abiotic and biological responses and feedbacks. This, for example, can make studying effects of climate change on organic carbon preservation and cycling in soils challenging.

Structure of microbial decomposition models. Credit: Abs and Ferrière [2020], Figure 5.1, adapted from Georgiou et al. [2017]How do human activities affect, and how are they affected by, biogeochemical cycles?

It is hard to name something in the environment that is not influenced by humans, including  biogeochemical cycles. Climate change is a big concern now and effects of climate change and feedbacks are particularly dramatic in the regions of the permafrost. Herndon et al. [2020] demonstrated influence of warming on the cycles of redox‐sensitive elements in permafrost‐affected ecosystems. One of the biggest concerns is positive feedback on the global warming due to the release of CO2 and methane, but many other elements, such as P, N, S, and Fe, are affected.

Why is there urgency in studying the interconnectedness of different ecosystems?

Earth is one system with numerous subsystems that are continuously interacting. Different ecosystems cannot be fully understood if they are studied in isolation because they are not closed systems.Earth is one system with numerous subsystems such as the biosphere, hydrosphere, atmosphere, and the tectonic system that are continuously interacting. Different ecosystems cannot be fully understood if they are studied in isolation because they are not closed systems. There is a continuous exchange of materials, energy, and living matter among them and they are all connected through the biogeochemical cycles.

To understand complex relationships, processes and feedback loops within landscape evolutions we need to understand how different ecosystems are connected in space and time.

The urgency of studying the interconnectedness of different ecosystems is coming from seizing the current opportunities that are offered by the Critical Zone Exploration Network via providing locations for the studies and collaborations among various experts.

What are some of the major gaps in our understanding of biogeochemical cycles where additional research is needed?

Our book lists nine major gaps, of which the two most important are: quantification of the effects of biological weathering across scales, and application of biogeochemical knowledge to solve societal problems.

Spanning orders of magnitude in spatial and temporal scales of processes is challenging in geosciences and adding the connected biological processes makes understanding even more complex. The establishment of the Critical Zone Observatories and their Exploration Network provides opportunities to investigate processes are various scales at numerous locations.

Application and transformation of knowledge to solve societal problems are becoming more pressing and relevant as humans exert a significant influence on the environment, including biogeochemical cycles.

The interdisciplinarity of biogeochemistry and the existing uncertainties in the research findings make it challenging to directly influence decision making. Increased collaborations between fields of biogeochemistry, humanities, and social sciences can offer results and apply solutions for societal problems, such as sustainable food production, food security, carbon management, and sequestration.

Biogeochemical Cycles: Ecological Drivers and Environmental Impact, 2021, ISBN: 978-1-119-41331-8, list price $199.95 (print), $160.00 (ebook). AGU members receive 35 percent off all books at Wiley.com. Log in to your AGU member profile to access the discount code.

—Katerina Dontsova (dontsova@arizona.edu,  0000-0003-2177-8965),  University of Arizona, USA; Zsuzsanna Balogh‐Brunstad ( 0000-0002-5749-1213), Hartwick College, USA; and Gaël Le Roux ( 0000-0002-1579-0178), National Center for Scientific Research, France

Editor’s Note: It is the policy of AGU Publications to invite the authors or editors of newly published books to write a summary for Eos Editors’ Vox.

Earth’s critical zone, which spans from the treetops to the base of groundwater, is where soils and minerals, water and air, and plants and animals all interact and influence one another [Brantley et al., 2007]. These interactions shape the physical landscapes we live on, sustain the waterways and soils that nourish us, and influence climate and the atmosphere we breathe.

The linkages between the critical zone and human well-being have motivated studies of this layer of Earth’s surface that since the mid-2000s, have often been coordinated through numerous place-based Critical Zone Observatories (CZOs) and, more recently, in theme-based Critical Zone Networks (CZNs). These coordinated CZO/CZN efforts have achieved major advances in understanding critical zone characteristics such as soil development, porosity and permeability evolution, and water distribution by addressing common problems using shared infrastructure and data [Sullivan et al., 2017].

The overwhelming focus on silicate landscapes in critical zone science has left large gaps in our knowledge of Earth’s surface and how it affects humans.However, established CZOs cover only a fraction of Earth’s surface and disproportionately represent silicate mineral–dominated landscapes as opposed to those composed of mainly carbonate minerals. The efforts largely neglect the nearly 15% of Earth’s ice-free surface that is underlain almost entirely by carbonate bedrock [Goldscheider et al., 2020] and the larger fraction of the planet with mixed silicate and carbonate bedrock.

Bedrock mineralogy exerts fundamental controls on many aspects of the critical zone, from water availability to soil composition to the many interactions that occur between life and rocks. The overwhelming focus on silicate landscapes in critical zone science has thus left large gaps in our knowledge of Earth’s surface and how it affects humans. Now scientists are looking to address these gaps by refocusing attention on neglected carbonate landscapes through the lens of critical zone science.

Carbonates Versus Silicates

Carbonate minerals such as calcite and aragonite differ in many ways from silicate minerals such as quartz and clays. Whereas silicate minerals are created predominantly through inorganic, or abiotic, means, carbonate minerals form mostly through biotic processes in organisms such as corals and algae. Especially in marine environments, these minerals can form thick deposits of nearly pure carbonate sediments. Carbonate sediments can lithify into dense rock and dissolve to form caves, shaping the critical zone where carbonate minerals dominate.

A karst weathering surface is exposed on Mount Kanin in the Julian Alps of Slovenia, near the Classical Karst region from which karst gets its name. Credit: Matthew Covington

The physical and chemical breakdown, or weathering, of bedrock minerals, whether silicate or carbonate, influences many characteristics of Earth’s critical zone, such as soil types and distribution; land surface morphology; and water quality, retention, and drainage [National Research Council, 2001]. These characteristics combine to provide services, including reducing pollution and providing plants with nutrients, that sustain ecosystems and societies. Human activities, especially modifications to drainages and application of excess nutrients, also affect how life and rock interact in the critical zone.

Earth’s critical zone should be considered a gradient between two compositional end-members: the silicate critical zone and carbonate critical zone.With their distinctive properties, carbonate and silicate minerals weather differently. Silicate minerals weather incongruently to produce new solid materials (e.g., alteration minerals) as well as dissolved species. In contrast, carbonate minerals weather congruently—they dissolve completely, leaving behind large voids in the landscape (e.g., caves and sinkholes). Thus, critical zone characteristics, for example, the architecture of physical properties, water and gas flow, and distribution of substrates where biology and geology intersect, will vary depending on the primary mineral content of bedrock. In recognition of the importance of mineralogy, we propose that Earth’s critical zone should be considered a gradient between two compositional end-members: the silicate critical zone and carbonate critical zone.

Neglected No More

The Carbonate Critical Zone Research Coordination Network (CCZ-RCN) was established in 2019, in part to further transdisciplinary and collaborative research into the critical zone amid landscapes composed of carbonate or mixed carbonate-silicate mineralogies (see sidebar).

The CCZ-RCN convened its first workshop in fall 2020, and the 70 participants reached consensus on 22 important research questions that define unknowns about the carbonate critical zone [Martin and CCZ-RCN Participants, 2021]. The questions align with five key research areas that focus on specific carbonate critical zone characteristics, differences between the carbonate and silicate critical zone, and the effects of varying carbonate and silicate mineral contents and that provide directions for future critical zone studies. These areas involve research into the following: (1) the boundaries and scales of critical zone environments; (2) the biological, chemical, and physical processes at work; (3) the rates and time frames of these processes; (4) carbon dynamics in the critical zone; and (5) the critical zone and society.

Below, we describe the processes and background relevant to each of the five research areas and highlight important questions to be addressed in future work.

Boundaries and Scales

An important difference between the effects of congruent and incongruent weathering is varying permeability, which can be orders of magnitude greater in the carbonate critical zone than in the silicate critical zone. Unlike in silicate terrains, permeability in carbonate terrains tends to scale with the distance over which it is measured, from wellbore to basin scales. The configuration of permeable and impermeable materials influences the movement of water, solutes, and gases into, through, and out of the critical zone, leading to questions of how permeability distribution alters carbonate critical zone architecture. Large voids also allow human access below the surface, which can enrich critical zone studies.

A key question about the critical zone is how the lower boundary should be defined.A key question about the critical zone is how the lower boundary should be defined [Sullivan et al., 2017]. This question is complicated by differences between the carbonate and silicate critical zone lower boundaries. The lower boundary of the carbonate critical zone varies with the location and morphology of voids, which can form a nonplanar surface hundreds to thousands of meters below the land surface. In contrast, the silicate critical zone lower boundary is typically a few meters to tens of meters below the land surface and roughly follows the surface topography.

Biological, Chemical, and Physical Processes

Feedbacks occur among many biological, chemical, and physical processes within the critical zone and with external drivers that force internal processes. For example, physical weathering and fracturing of rock caused by tectonic forces increase surface area and hydrologic connectivity, thus enhancing mineral dissolution. This feedback can produce heterogeneous porosity and permeability distributions that are hallmarks of the carbonate critical zone, in contrast to the regular decrease in porosity and permeability with depth in the silicate critical zone.

Additional feedbacks exist between flow rates and magnitudes, chemical compositions of water and gases, and biological activity in the critical zone. Recharge locations shift with external forcing, such as when floods raise stream elevations above the groundwater table and recharge aquifers through spring vents [Brown et al., 2014]. These shifts alter the structure and activity of biological communities and disrupt gradients in pH and reduction-oxidation conditions that develop from metabolic processes.

Cave divers explore a sinkhole in the carbonate critical zone of the Yucatán Peninsula, Mexico, where a layer of sulfide-oxidizing microbes marks a reduction-oxidation boundary between fresh water and underlying salt water. Credit: Jason Gulley

These and other changes in reduction-oxidation conditions are linked to production and consumption of the three primary greenhouse gases: carbon dioxide, methane, and nitrous oxide. However, the impacts of these shifts on atmospheric compositions of the gases are unknown and represent an example of more general questions about how linked hydrological and biological processes within the carbonate critical zone change magnitudes and fluxes of reaction products.

Rates and Time

Timescales for many processes are shortened in the carbonate critical zone compared with the silicate critical zone because of faster reaction rates of carbonate compared to silicate minerals and elevated flow rates through high-permeability zones. These characteristics create sensitivities to rare and short-lived extreme events that may alter equilibrium states within the carbonate critical zone. For example, flooding of caves with organic carbon–rich surface waters is known to cause mass mortality of troglobitic species that live entirely in underground habitats.

The rapid responses in the carbonate critical zone may provide a bellwether for wider climate change impacts on critical zone processes.The rapid responses in the carbonate critical zone may provide a bellwether for wider climate change impacts on critical zone processes. Improving our understanding of the rates and timescales of processes, such as the effects of changing flood, drought, and fire frequencies, in the carbonate critical zone will provide vital information for comparison with the slower response of the silicate critical zone, where change may occur at timescales longer than common observational periods. Observations of rapid change in the carbonate critical zone should thus aid in the development of models that predict overall responses of Earth’s critical zone to climate change.

Carbon Dynamics

Carbonate minerals represent the largest global store of carbon, making research into carbon dynamics in the carbonate critical zone particularly important. Through numerous reactions and interactions, the inorganic carbon store is linked to organic carbon production, remineralization, and production of various natural acids. Carbonate mineral dissolution by carbonic acid consumes carbon dioxide, contributing to short-term drawing down of atmospheric carbon dioxide levels. However, carbonate mineral dissolution by other acids has the opposite effect of producing carbon dioxide, coupling the carbonate critical zone and climate [Martin, 2017].

Although equilibrium is often assumed between soil carbon dioxide and groundwater, disequilibrium may result from heterogeneous distributions of recharge, flow paths, and respiration often seen in the carbonate critical zone. Understanding the controls of this disequilibrium, which drives carbon dioxide dissolution or evasion and alters pH, weathering reactions, and carbonate mineral dissolution or precipitation, is critical in linking the carbonate critical zone to the global climate system.

Organic carbon cycling is coupled to ecosystem metabolism (the ways that plants, animals, and microorganisms process carbon) through fixation of inorganic carbon to organic matter and remineralization of organic matter to carbon dioxide and nutrients like nitrogen and phosphorous. This nutrient generation supports ecosystems above and below the land surface, although excess anthropogenic nutrients can alter aquatic ecosystems common in clear-water streams of carbonate terrains. Links between dissolved and gaseous carbon dioxide distributions, organic carbon fixation, and mineral weathering make finding answers to questions about carbon dynamics key to understanding many carbonate critical zone processes.

The Critical Zone and Society

The carbonate critical zone, especially where karst landscapes form, has important ecological, social, cultural, economic, and aesthetic values. From the water resources it harbors for up to 25% of the world’s population to common geohazards (e.g., sinkholes), the carbonate critical zone is key to the sustenance and resilience of local communities that rely on its services.

Distinct characteristics of the carbonate critical zone increase its vulnerability to human activities, from dispersed infiltration of pollutants to soil erosion and rocky desertification.However, distinct carbonate critical zone characteristics also increase its vulnerability to human activities, from dispersed infiltration of pollutants to soil erosion and rocky desertification. Local communities’ reliance on and impacts on carbonate critical zone services suggest that those communities should play an important role in the management and maintenance of carbonate critical zone services. In exchange, local communities should receive equitable distribution of the critical zone services, such as access to reliable water supplies, waste handling, and fertile soils. This equity is especially important where these services are limited.

Inputs from local stakeholder groups, through coproduction of scientific research based on experiential and local knowledge, would not only enrich our understanding but also ensure research outcomes reach and benefit the local communities. This approach requires an equitable exchange of rewards and values stemming from research participation by local stakeholders and mainstream scientists [e.g., Harris et al., 2021].

A More Holistic View of the Critical Zone

Carbonate and silicate minerals are end-members of a spectrum of critical zone bedrock compositions, and fundamental differences in their physical and chemical properties create distinct characteristics in Earth’s critical zone. Studies of these two end-members, as well as of regions of mixed mineralogical compositions, can provide a better understanding of the critical zone in its entirety.

To date, however, critical zone research has predominantly emphasized silicate landscapes, leaving us well short of such a holistic understanding. With increased focus on the neglected carbonate critical zone—particularly on the research directions and questions outlined here—we can fill important knowledge gaps about a part of Earth upon which we humans depend so closely.

Acknowledgments

This material is based upon work supported by the National Science Foundation (NSF) under grant EAR-1905259. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of NSF. We gratefully acknowledge valuable contributions of all participants in the workshop as listed in the workshop report.

Diverse Research Needs Diverse Researchers

A subset of participants at the fall 2020 CCZ-RCN workshop developed an action plan with the goal of increasing diversity in the RCN by implementing inclusive RCN activities and creating a space to nurture equitable and accessible participation by scientists with differing backgrounds and identities. Although the plan is just a small step within a small group, it may provide a template of ways to enhance and improve diversity, equity, and inclusion (DEI) throughout the geosciences. Increased diversity will enrich talents and skills, experiences and interests, worldviews, frameworks, and approaches in the study and understanding of the carbonate critical zone.

The first RCN workshop was planned to enhance collaboration among people with different identities, backgrounds, and experiences. Meeting organizers created small working groups based on demographic information from a preworkshop survey. They promoted equitable and inclusive participation of all attendees using the Technology of Participation facilitation method that fosters authentic participation and meaningful collaboration.

In the working group and plenary sessions, participants reflected on the causes and consequences of limited diversity in the geosciences. They discussed ways to enhance DEI within the RCN. Invited speakers described successful DEI programs in the geosciences, including Sparks for Change and the Louis Stokes Alliances for Minority Participation. A DEI interest group was formed to support the development and implementation of the DEI action.

Future RCN activities will include webinars, training sessions, and networking opportunities at conferences and workshops. Travel grants have been established to support students from underrepresented demographics. The RCN will recruit students from minority-serving colleges and universities, particularly at the graduate level, to attend the next workshop (April 2022), training activities, and field trips. The RCN aims to demonstrate how changing the designs of workshops and other activities can enhance inclusion, diversity, equity, and accessibility and further transdisciplinary, collaborative science to improve understanding of the carbonate critical zone.

As rising temperatures across the Arctic thaw increasingly larger areas of permafrost, more and more organic carbon stored within these frozen soils is being released. Because microbes can convert this liberated material into greenhouse gases that further accelerate the warming, its fate is of grave concern.

Despite general agreement that the warming climate is amplifying the carbon cycle in northern high-latitude watersheds, the amount of permafrost thawing into Arctic rivers is poorly constrained because of the lack of a reliable tracer. To help address this gap, Rogers et al. use a novel approach to search for old permafrost-derived carbon in Russia’s Kolyma River, whose 650,000-square-kilometer watershed is completely underlain by frozen soils.

The authors employed two independent techniques to chemically fingerprint thawed permafrost carbon and track it within the Kolyma watershed during late summer, when the most permafrost thaws. The results from both techniques point to the same conclusion: Relatively little old organic carbon is derived from thawing permafrost in the Kolyma River, which is dominated by modern inputs. Importantly, the team’s analyses indicate this conclusion is true for both microbially unaltered and microbially degraded permafrost carbon.

Using a mixing model to further constrain their results, Rogers and colleagues estimated that a maximum of just 0.8% to 7.7% of the river’s late summer dissolved organic carbon comes from undegraded permafrost. This amount translates to about 6% of the 0.82 teragram of the load the Kolyma delivers to the ocean each year.

This conclusion suggests that despite increased thawing, large northern high-latitude rivers are currently transporting only minor amounts of permafrost-derived dissolved organic carbon to the Arctic Ocean. These findings have important implications for understanding the evolution of dissolved organic carbon during permafrost thaw and river transport. More knowledge of where this thawed carbon resides and how it’s affecting the Arctic’s changing carbon cycle is necessary to improve assessments of the region’s potential to accelerate global warming. (Journal of Geophysical Research: Biogeosciences, https://doi.org/10.1029/2020JG005977, 2021)

—Terri Cook, Science Writer

Volcanic eruptions can have a massive effect on Earth’s climate. Volcanic ash and gases from the 1815 eruption of Mount Tambora, Indonesia, for example, contributed to 1816 being the “year without a summer,” with crop failures and famines across the Northern Hemisphere. In 1991, the eruption of Mount Pinatubo in the Philippines cooled the climate for around 3 years.

Large volcanic eruptions like Tambora and Pinatubo send plumes of ash and gas high into the atmosphere. Sulfate aerosols from these plumes scatter sunlight, reflecting some of it back into space. This scattering warms the stratosphere but cools the troposphere (the lowest layer of Earth’s atmosphere) and Earth’s surface.

“What really matters is whether these [volcanic aerosols] are injected into the stratosphere.”Now new research published in Nature Communications has found that climate change could increase the cooling effect of large eruptions like these, which typically occur a couple of times every century. The study also found, however, that the cooling effects of smaller, more frequent eruptions could be reduced dramatically.

“What really matters is whether these [volcanic aerosols] are injected into the stratosphere—that is, above 16 kilometers in the tropics under current climate conditions and closer to 10 kilometers at high latitudes,” explained Thomas Aubry, a geophysicist at the University of Cambridge in the United Kingdom and lead author of the new study. “If [aerosols] are injected at these altitudes, they can stay in the atmosphere for a couple of years. If they are injected at lower altitudes, they are essentially going to be washed out by precipitation in the troposphere. The climatic effect will only last for a few weeks.”

The power of a volcanic eruption influences the elevation at which gases enter the atmosphere, with stronger eruptions injecting more aerosols into the stratosphere. The buoyancy of the gases also contributes to the elevation at which they settle in the atmosphere. Climate change could affect this buoyancy: As the atmosphere warms, it becomes less dense, increasing the elevation at which aerosols reach neutral buoyancy.

Modeling Mount Pinatubo

Aubry and his colleagues used models of both climate and volcanic plumes to simulate what happens to aerosols emitted by a volcanic eruption in the present climate and how that could change by the end of the century with continued global warming. In their models, all the eruptions occurred at Mount Pinatubo.

They found that for moderate-magnitude eruptions, the height at which sulfate aerosols settle in the atmosphere remained the same in a warmer climate. But the cooling effect of such eruptions was reduced by around 75%. This discrepancy has less to do with volcanic emissions and more to do with the atmosphere: The height of the stratosphere is predicted to increase with climate change. Aerosols from moderate volcanic eruptions will therefore be more likely to remain in the troposphere and be removed by rain, reducing their potency.

Volcanic plumes will rise around 1.5 kilometers higher in the stratosphere in a warmer climate.For large eruptions, models indicated that volcanic plumes will rise around 1.5 kilometers higher in the stratosphere in a warmer climate. This change in elevation will result in the aerosols spreading faster around the world. This increase in aerosol spread is mainly due to a predicted acceleration of the Brewer-Dobson circulation, which moves air in the troposphere upward into the stratosphere and then toward the poles. The change in Brewer-Dobson circulation is associated with climate change.

In addition to enhancing the global cooling effect of the aerosols, the increase in aerosol spread reduces the rate at which the sulfate particles bump into each other and grow. This further increases their cooling effect by allowing them to better reflect sunlight.

“There is a sweet spot in terms of the size of these tiny and shiny particles where they are very efficient at scattering back the sunlight,” explained Anja Schmidt, an atmospheric scientist at the University of Cambridge and coauthor of the paper. “It happens to be that in this global warming scenario that [we] simulated, these particles grow close to the size where they are very efficient in terms of scattering.”

“We find that the radiative forcing (the amount of energy removed from the planet system by the volcanic aerosol) would be 30% larger in the warm climate, compared to the present-day climate,” Aubry said. “Then we suggest that would amplify the surface cooling by 15%.”

Stefan Brönnimann, a climate scientist at the University of Bern who was not involved in the new research, said that the study is interesting because “it makes us think about the processes involved [between volcanic emissions and climate] in a new way.”

Brönnimann noted, however, that the simulations limited their models to eruptions of Mount Pinatubo in the summer. It would be interesting to see whether the conclusions still hold for eruptions at different latitudes and in different seasons, he said.

A Changing Stratosphere

It is difficult to say whether the amplified cooling from large volcanic eruptions or the decrease in cooling from smaller eruptions will have a net effect on climate, Aubry said.

Schmidt said that current increases in the frequency and intensity of forest fires could also alter the climatic effects of volcanic eruptions because they are affecting the composition of the stratosphere. “There is really a lot of aerosol pollution in the stratosphere, probably on a scale that we’ve never seen before.”

—Michael Allen (michael_h_allen@hotmail.com), Science Writer

Ground-based early warning systems for flooding are frequently washed away or damaged by floods, as in the case of the Babai River during the August 2014 event. Therefore, proper use of satellite-based rainfall estimates (SREs) is critical at the time of failure of gauge data. However, relying on these SRE products requires a prior performance evaluation with respect to the gauge data. Also, gauge data frequently suffer from data gaps.

Talchabhadel et al. (2021) demonstrate the applicability of well-performing SRE products to fill gauge data gaps and correct the poor performing SRE products with the information of the gauge data on an hourly scale. Their study took a representative case in the West Rapti River basin, Nepal, for an extreme weather event of August 2014.

Application of SREs is a good head start in data-scarce regions. Furthermore, the methodology and findings are scalable in the areas of flood management in Nepal and beyond.

Citation: Talchabhadel, R., Nakagawa, H., Kawaike, K., Yamanoi, K., Musumari, H., Adhikari, T. R., & Prajapati, R. [2021]. Appraising the potential of using satellite-based rainfall estimates for evaluating extreme precipitation: A case study of August 2014 event across the West Rapti River Basin, Nepal. Earth and Space Science, 8, e2020EA001518. https://doi.org/10.1029/2020EA001518

—Jonathan H. Jiang, Editor, Earth and Space Science

World hunger has been increasing since 2014 after falling for decades, and Africa in particular has suffered from this trend. More than 20% of people in Africa are currently affected by hunger, and more than one third are undernourished, the United Nations estimates.

“To date, there is very little work done to try to quantify the relationship between conflict, climate, and food insecurity. This paper does exactly that.”New research suggests that in Africa at least, this increase in food insecurity is being driven by an uptick in violent conflict. An analysis of food insecurity in sub-Saharan Africa between 2009 and 2019 found that the impacts of drought, although significant, remained relatively steady over the period, whereas violent conflict had an increasingly significant impact. Warfare exacerbates and prolongs the impacts of drought by displacing people, affecting local supply chains, and preventing outside aid, the team reported in a new study published in Nature Food.

“This is an excellent paper that comes at the right time,” said Krishna Krishnamurthy, a climate and food security analyst at the environmental consulting and engineering firm Tetra Tech who was not involved in the new research. “To date, there is very little work done to try to quantify the relationship between conflict, climate, and food insecurity. This paper does exactly that.”

Conflict Worsens the Impacts of Drought over Time

To understand the role of potential drivers of food insecurity in Africa, the researchers used a tool called the Famine Early Warning Systems Network to look at the effects of different hazards in 14 of the continent’s most food-insecure countries. Taken together, these countries represent about 70% of the continent’s population that is affected by hunger. The team also analyzed the hazards’ impacts on different occupations, like farming and livestock herding, to figure out whether some livelihoods made people more vulnerable than others. They also looked at how crises unfolded over time and how long communities suffered from hunger as a result.

Because the study data set is continuous, “we can look at not just isolated events but also how food crises have evolved over time.”Because the study data set is continuous, “we can look at not just isolated events but also how food crises have evolved over time,” said Weston Anderson, an agroclimatologist at the University of Maryland and lead author of the new study. Although previous research focused on specific events, this team analyzed an entire region over time to try to spot wider trends.

The team found that although droughts could have devastating impacts on crops and livestock, they tended to last for a discrete period of time. The destabilizing effects of violent conflicts, on the other hand, could cause food insecurity that lasted years. When drought occurs in a conflict zone, Anderson explained, it’s harder for food aid to reach people, and it’s harder for society to function.

Food Insecurity Is Context Specific

The drivers of food security aren’t the same everywhere, and conflict isn’t driving food security in every country, Anderson said. Violence in three countries—Nigeria, Somalia, and South Sudan—made up the lion’s share of conflict-driven food insecurity found in the study, he said, emphasizing that conflict is very context specific. In Nigeria, for example, violent conflict largely associated with the Boko Haram terrorist group began to trigger food insecurity in 2014 and continues to affect food security today. “That [conflict is] certainly protracted and prolonged in a way drought isn’t,” Anderson said.

But as climate change affects the frequency and intensity of drought events, it’s crucial to better understand how these stressors interact. It’s also crucial to understand that these hazards can have different impacts on different groups. One of the most important takeaways from the study, Anderson said, was that food insecurity crises hit livestock herders harder than any other group.

Food insecurity crises analyzed in the study tended to affect 40% to 50% of herders in a given population, compared to fewer than 15% of individuals in other livelihood groups. Herders also suffered for twice as long after droughts—2 years instead of 1—because they would sell their livestock to pay for food.

Climate Change Could Play a Bigger Role in the Future

The team cautions that the research has its limitations. Although they found that locusts have little impact on food insecurity, for instance, the study didn’t cover the most recent devastating locust outbreak in East Africa. In 2019 and 2020, swarms of locusts numbering in the tens of millions took out more than 10,000 square kilometers of pastureland in East Africa, putting an estimated 5 million people at risk of hunger. The researchers also didn’t include Madagascar in their data set, and the country is currently suffering from a brutal drought linked to climate change that is driving famine in the region.

“Our findings don’t diminish the possibility that climate change could lead to droughts that cause food crises, even though that’s not what we found during this time period,” Anderson said.

Erin Coughlan De Perez, a disaster risk management and climate change adaptation researcher at Tufts University, called the study “a good contribution to our understanding of food security.” While cautioning that it’s not a predictive model, she said that the research still provides helpful context that could improve early-warning systems for hunger crises in Africa. It shows that herders, for instance, “experience drought completely differently,” she said. “I think it’s critical that we highlight differences in people’s experiences.”

“We live in an unprecedented time with violence, climate-induced crises, and other shocks,” Krishnamurthy said. “There is an urgency to start addressing the root causes of these issues.”

—Rachel Fritts (@rachel_fritts), Science Writer