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Translating Climate Models to the Language of Paleoclimate Data

Fri, 05/24/2019 - 12:28

When it comes to climate modeling, understanding the past is critical to predicting the future. Scientists use all manner of materials to reconstruct Earth’s past climate. Tree rings, ice cores, corals, bat guano, and even whale earwax can reveal clues about historical conditions.

Among the various climate reconstruction strategies currently in play, lake sediments stand out for their completeness and continuity. The deposits lining lake basins supply a trove of data on changes in air temperature, water temperature, and hydrology. The global lake data record spans hundreds to thousands of years; in some regions, lake sediment archives offer a cohesive view of lacustrine conditions dating back to the Last Glacial Maximum, approximately 21,000 years ago.

Unfortunately, paleoclimate data, like those scrounged from debris at the bottom of a lake, do not always produce a clean and coherent signal. Climatic variables like temperature and precipitation can often be masked and hard to constrain. In turn, such data are more difficult to incorporate into climate models, so scientists use proxy system models to translate climate model data into the same reference frame as paleoclimate data. This translation puts the two data types on a level playing field for an apples-to-apples comparison. These translations are essential for improving the physics that underpin climate forecasts.

In a new study, Dee et al. detail the first comprehensive proxy system model for lake archives, called PRYSM (Python, Proxy System Modeling). The model describes several components of a lake’s history, including the energy balance and hydrology of the system, the accumulation of leaf waxes or other physical and biological deposits, and sedimentation and compaction at the bottom of the water body. PRYSM also provides an accounting of errors in data sampling, dating, and analysis.

To validate the model, the authors used the Paleoclimate Modelling Intercomparison Project Phase III (PMIP3) to simulate the 20th century conditions in two African lakes, Lake Malawi and Lake Tanganyika. They then compared the results to data in the field. The comparison between the simulated and real-world data revealed that lake systems exert a confounding influence on the climate signal of interest (e.g., air temperature). For instance, the results showed that lake surface temperatures respond differently than air temperatures to changes in mean climate; therefore, changes in lake temperature may not adequately reflect changes in air temperature. The revelation has far-reaching implications for understanding how lakes may respond to human-caused climate change.

The lake model promises to improve interpretations of past climatic conditions and predictions of the future climate. The model will also help researchers answer questions like, What percent change in precipitation is needed to simulate a 150-centimeter change in lake level over 100 years?

PRSYM, now in its second version, is the first step toward a larger distribution platform for lake sediment data and proxy system models that describe them. Eventually, the authors envision a fully operational platform that can serve as a research tool and resource for the entire paleoclimate community. (Paleoceanography and Paleoclimatology, https://doi.org/10.1029/2018PA003413, 2018)

—Aaron Sidder, Freelance Writer

On the Prospect of Ancient Metallic Volcanism on Asteroids

Fri, 05/24/2019 - 11:30

There are several examples from icy and rocky worlds in our Solar System explored by spacecraft of volcanic processes either occurring or having occurred in the past. Volcanism is apparently a common process and displays a wide variety of forms. We have yet to explore, however, metal worlds (i.e., the exposed cores of differentiated planetesimals).

Abrahams and Nimmo [2019] seek to determine whether ancient metallic volcanism could have happened on a metal asteroid. Unfortunately, observations of metal asteroids are largely just points of light in the sky, tantalizingly unresolved. The authors thus make predictions that may enable exploration via variations seen in iron meteorites. In addition, this possibly sets the stage for potentially amazing discoveries when Psyche (the spacecraft) arrives at Psyche (the asteroid), as no one knows the form that metal volcanic constructs could take.

Citation: Abrahams, J. N. H., & Nimmo, F. [2019]. Ferrovolcanism: Iron volcanism on metallic asteroids. Geophysical Research Letters, 46. https://doi.org/10.1029/2019GL082542

—Andrew Dombard, Editor, Geophysical Research Letters

Congress Hears Biodiversity Warning During a Charged Hearing

Thu, 05/23/2019 - 16:08

Some of the world’s leading scientific experts in biodiversity delivered to Congress the message of a damning new report that up to 1 million species face extinction.

“The evidence is unequivocal: Biodiversity, which is important in its own right and essential for human well-being, is being destroyed by human activities at a rate unprecedented in human history.”They delivered that message despite efforts by several Republican members of Congress and their witnesses to belittle, dismiss, and drown out those findings at a 22 May congressional hearing.

“The evidence is unequivocal: Biodiversity, which is important in its own right and essential for human well-being, is being destroyed by human activities at a rate unprecedented in human history,” Robert Watson, immediate past chair of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), testified before the House Committee on Natural Resources’ Subcommittee on Water, Oceans, and Wildlife.

In a recent report, IPBES found that the global rate of extinction “is already at least tens to hundreds of times higher than the average rate over the past 10 million years and is accelerating.”

“The loss of biodiversity is not only an environmental issue, but an economic, development, social, security, moral, and ethical issue,” Watson testified.

The report found that many species could become extinct within decades, largely because of human activities. The report states that “goals for conserving and sustainably using nature and achieving sustainability cannot be met by current trajectories, and goals for 2030 and beyond may only be achieved through transformative changes across economic, social, political and technological factors.”

IPBES released a summary of its peer-reviewed report on 6 May and plans to release the full report soon.

Responding to Charges of “Exaggerated Claims”

Rep. Tom McClintock (R-Calif.), the ranking Republican member of the subcommittee, characterized the IPBES report as “the latest contribution to apocalyptic predictions.”

Patrick Moore, chairman of the board of the CO2 Coalition and a witness at the hearing, testified that “the highly exaggerated claims of the IPBES are not so much out of concern for endangered species as they are a front for a radical political, social, and economic ‘transformation’ of our entire civilization.”

The nonprofit CO2 Coalition promotes positive contributions of carbon dioxide and pushed for the United States to withdraw from the Paris climate accord.

However, Watson sharply disputed the charge, saying that the numbers in the IPBES document are drawn from two distinct lines of evidence, including an independent analysis and a straight extrapolation of the International Union for Conservation of Nature’s (IUCN) Red List of Threatened Species. Watson added that IUCN has endorsed the IPBES analysis.

Moore, who is an ecologist and a policy adviser to The Heartland Institute, a free market think tank based in Arlington Heights, Ill., also stated in his testimony, “As with the manufactured ‘climate crisis,’ they are using the specter of mass extinction as a fear tactic to scare the public into compliance. The IPBES itself is an existential threat to sensible policy on biodiversity conservation.”

Marc Morano, editor of ClimateDepot.com and a prominent climate change denier, according to the DeSmog blog, criticized Watson, whom he sat next to at the witness table. “[Watson] says it’s our last chance to save the planet. These are the words of a salesman, a science bureaucrat, not a disinterested…” Morano never finished that sentence because subcommittee chair Rep. Jared Huffman (D-Calif.) interrupted and told Morano to direct testimony to him.

Later in the hearing, Huffman castigated Morano, saying, “I don’t know what inspires someone to make a career of trolling scientists or monetizing contrarian ideology on the YouTube and Ted Talk circuit. But it’s just a very different kind of conversation than the science-based conversation I think many of us would like to try to have.”

“Shadowy Stuff”

Huffman criticized Republicans for choosing Morano and Moore as their witnesses.

“There’s a narrative around here [in Congress] that Republicans are coming around on science and climate. Look no further than the witnesses they continue to dredge out of the fever swamp for these subcommittee hearings, and you’ll see that they’ve got a long way to evolve,” Huffman told Eos in an interview. “This is shadowy stuff, and we see it week after week: instead of scientists, people from these junior varsity think tanks that they keep dredging up. Apparently, witnesses from QAnon and Infowars”—a conspiracy theory group and website, respectively—”were unavailable, and so this is what we get.”“It’s just a choice that the Republicans keep making in these hearings. Instead of serious policy conversations, serious science conversations, they want to do politics.”

Morano “brought a provocative, almost like a World Wrestling type of ethos to his testimony. There were very few facts and certainly no science. He admitted that, at the outset, he’s a political science guy, and he’s a former staffer to Jim Inhofe,” Huffman told Eos, referring to the Oklahoman senator who authored a book entitled The Greatest Hoax: How the Global Warming Conspiracy Threatens Your Future. “[Morano] is here to throw bombs. It’s just a choice that the Republicans keep making in these hearings. Instead of serious policy conversations, serious science conversations, they want to do politics.”

Huffman said the way to counter the attacks on science is to present expert witnesses. “Well, look, we just presented you with four of the world’s leading scientists, for God’s sake. That’s probably where you start in countering that,” he said. “Then people can weigh for themselves: Do they want to consider the overwhelming weight of the world’s best scientists or the shadowy junior varsity think tank from people that used to work for Jim Inhofe?”

“Today, We Are That Asteroid.”

The last time there was a mass extinction “it happened because an asteroid hit the planet. Today, we are that asteroid.”After the hearing, another witness said he was disappointed in the “antiscience view” expressed by Morano and Moore. “It’s hype. It’s bombast. It’s all of this stuff that is not based in reality,” Jacob Malcom, director of the Center for Conservation Innovation for Defenders of Wildlife, a Washington, D.C.–based conservation group, told Eos. “I don’t think it will ever go away. But as long as it stays marginalized, I think more and more people will see it for what it is.”

Malcom, at the hearing, said that the last time there was a mass extinction “it happened because an asteroid hit the planet. Today, we are that asteroid.”

Watson, who chaired the Intergovernmental Panel on Climate Change from 1997 to 2002, told Eos that perhaps Republicans chose Morano and Moore as their witnesses “because we have said”—in the IPBES report—“that climate change and biodiversity must be dealt with together.”

“I would have hoped that the Republicans would have chosen two very good scientists who could have debated the merits of the IPBES report rather than clearly someone who’s just a straight climate denier,” Watson said, referring to Morano.

Why People Should Care About Biodiversity Loss

Watson told Eos that “the evidence is strongly behind this report” and that it is “the most heavily peer-reviewed document you could imagine.” The report, which assessed about 15,000 articles and responded to about 15,000 comments, was prepared by 145 expert authors and is the most comprehensive document ever prepared about biodiversity.

Watson said that the American public should care about the IPBES report for several reasons. “First, we shouldn’t destroy nature. Every religion in the world says we shouldn’t destroy nature. Nature is important,” he told Eos. “But more important than that, you could argue, is it is the substance behind food security, water security, it does control our climate in part, it does control pollination, it does control storm surges. These are things that affect everyday Americans. If we continue to lose biodiversity, if we continue to fragment our ecosystems, then human well-being will indeed suffer. This is something the average American should care about.”

Trump Administration “Going in the Opposite Direction”

At the hearing, Huffman said that “scientists have been ringing the alarm bell for years” about threats to biodiversity. However, Huffman criticized what he said are efforts by the Trump administration to increase the risk to species, including the administration’s attempts to weaken the federal Endangered Species Act, its efforts to expand oil and gas activities in the Arctic National Wildlife Refuge and elsewhere, and its plan to withdraw from the Paris climate accord.

“All of these are things we can do something about, but we are not yet on track to slow the extinction crisis. We need to do more.”“Despite overwhelming evidence that we have an extinction crisis on our hands, the Trump administration is going in the opposite direction to appease special interests and big donors,” he said.

The IPBES report states that the direct drivers of change in nature that have the largest global impact currently are, in order, changes in land and sea use, exploitation of organisms, climate change—with the report warning that future impacts of climate change on biodiversity and ecosystem functioning are projected to become more pronounced over the coming decades—pollution, and the invasion of alien species.

“All of these are things we can do something about, but we are not yet on track to slow the extinction crisis,” Huffman said. “We need to do more.”

—Randy Showstack (@RandyShowstack), Staff Writer

New Study Shifts Paradigm of Coastal Sediment Modeling

Thu, 05/23/2019 - 13:25

Coastal habitats bear the brunt of global environmental change. Rising sea levels, intense shoreline development, and pollution all contribute to worldwide habitat losses on the order of 1% to 7% per year. Cumulatively, nearly half of the world’s wetlands, mangroves, and seagrass habitats have eroded away over the past several decades.

Coastal ecosystems serve as vital carbon sinks and storm buffers while also providing critical habitat for countless species, both rare and abundant. To protect and maintain both natural and developed shorelines, scientists and landscape planners need reliable models on how water, sediment, and vegetation interact in coastal environments.

For years, so-called sediment transport models relied on measurements of bed shear stress; however, recent studies indicate these models underestimate the amount of material transported through plant-laden waterways. Specifically, the models do not account for the turbulence plants create in flowing water. In response to these shortcomings, Yang and Nepf propose a new framework for modeling sediment transport along vegetated shorelines and floodplains.

The authors developed an alternative method that relies on turbulent kinetic energy to predict the rate of sediment transport in vegetated zones. They conducted experiments in a 1-meter-wide by 10-meter-long flume that recirculated water and sediment while they varied the amounts of model plants and water velocity in the flume.

Upon successfully developing a model for vegetated regions, the authors tested their work in conditions lacking vegetation, scenarios that the bed shear stress model typically captures well. The results of the follow-up experiments suggest that the turbulence models also successfully predict sediment movement in unvegetated channels; in some cases, the new model worked even better than the standard model.

When taken together, the results from both the vegetated and bare-channel experiments indicated that turbulence is a better universal predictor of sediment flow than bed shear stress. The findings represent a significant advance in the field of coastal hydrology and geomorphology. The newly developed model should improve predictions of sediment transport and retention in both vegetated and unvegetated regions while improving restoration and planning in coastal environments. (Geophysical Research Letters, https://doi.org/10.1029/2018GL079319, 2018)

—Aaron Sidder, Freelance Writer

Understanding ENSO in a Changing Climate

Thu, 05/23/2019 - 13:24

The El Niño–Southern Oscillation (ENSO) is the strongest year-to-year climate fluctuation on the planet. It is spawned in the tropical Pacific Ocean, but its societal and environmental impacts are felt worldwide. The character of ENSO, which is a naturally occurring phenomenon alternating between warm (El Niño) and cold (La Niña) phases, depends on the background climatic conditions in which it develops.

The climate conditions associated with ENSO are changing as the planet warms through unabated atmospheric greenhouse gas emissions, raising questions about whether anthropogenic greenhouse forcing has affected ENSO already, or will in the future. These questions have been debated for nearly 30 years, but they take on greater urgency as the manifestations of climate change become ever more apparent.

Sixty research scientists from around the world gathered to address these questions at a symposium held at CSHOR in Australia.

Participants considered suggestions from the instrumental record and paleoproxy data—primarily of tropical Pacific sea surface temperature—that climate change has affected the observed ENSO cycle.

The evidence was deemed to be inconclusive.

The past 40 years have witnessed three extreme El Niños (1982–1983, 1997–1998, and 2015–2016) unlike any comparable period in the nearly 150-year-long instrumental record. However, 150 years is too short a period to unambiguously determine a climate change effect, considering natural variability and data reliability before 1950.

Regardless of whether the ENSO cycle has been affected already or will be affected in the future, the effects of ENSO today appear to be compounded by climate change.Paleoproxies can provide much longer records, with some studies finding that 20th-century ENSO variance is higher than in the distant past. However, paleoproxy records are relatively limited in geographical distribution, and their interpretation is complicated by the convolution of biological, geochemical, and physical factors not related to climate, leaving large uncertainties.

For future projections, scientists rely on climate models whose performance has been improving with regard to representation of ENSO, although the climate sensitivity varies widely across models and systematic errors persist. However, the latest modeling studies coupled with theoretical understanding suggest that under the usual emission scenarios, occurrences of strong ENSO events may increase by the end of the 21st century.

Regardless of whether the ENSO cycle has been affected already or will be affected in the future, the effects of ENSO today appear to be compounded by climate change simply because of the superposition of ENSO conditions on a warmer background state. This became most evident during the extreme 2015–2016 El Niño, which coincided with record-breaking cyclone activity in the tropical Pacific, an unprecedented global coral bleaching event, and extreme disruption of ecosystems and fisheries in the central Pacific (linked to record high sea surface temperatures there).

The ENSO Science Symposium participants discussed the need to reduce uncertainty in ENSO predictions and long-term projections, which will require ongoing efforts to sustain satellite and in situ climate observing systems, expand the database of paleoreconstructions, and improve models. There is likewise a need for better understanding of climate interactions across ocean basins, across timescales spanning decadal variability, and interactions with biogeochemistry. Significant progress has been made on many of these topics, but more work remains to be done.

The symposium was followed by a 2-day coordination workshop on an AGU monograph for the AGU Centennial titled ENSO in a Changing Climate, which will cover the latest science on ENSO dynamics, effects, prediction, and future projections.

Acknowledgments

CSHOR sponsored the symposium and the book workshop. CSHOR is a joint research center between the Qingdao National Laboratory for Marine Science and Technology and the Commonwealth Scientific and Industrial Research Organisation. This is Pacific Marine Environmental Laboratory (PMEL) contribution 4951.

—Michael J. McPhaden (michael.j.mcphaden@noaa.gov), PMEL, National Oceanic and Atmospheric Administration, Seattle, Wash.; Agus Santoso, Australian Research Council (ARC) Centre of Excellence for Climate Extremes and Climate Change Research Centre, University of New South Wales, Sydney, Australia; and CSHOR, CSIRO Oceans and Atmosphere, Hobart, Tas., Australia; and Wenju Cai, CSHOR, CSIRO Oceans and Atmosphere, Hobart, Tas., Australia; and Key Laboratory of Physical Oceanography/Institute for Advanced Ocean Studies, Ocean University of China and Qingdao National Laboratory for Marine Science and Technology, Qingdao, China

Celebrating a Century of Nonlinearity Across the Geosciences

Thu, 05/23/2019 - 13:23

Throughout the 19th and early 20th centuries, the concept of linear systems—in which any changes in output are directly proportional to modifications made to their inputs—dominated the thinking and methodology used to study the physical sciences. Following the end of World War II, however, advances in observational techniques and the development of increasingly powerful computational devices began to alter the way scientists formulate physical problems and solve them mathematically.

During the past half century, these breakthroughs led to a rapid expansion in nonlinear approaches to studying the physical sciences, a development that can only be characterized as revolutionary. The evolution of nonlinear concepts, which describe the cause-and-effect relationships in most natural systems, has significantly increased the range of inquiries geoscientists are able to address. Still, only a small number of nonlinear methodologies in the discipline currently exist, according to a recent paper by Ghil.

The author highlights a small selection of key achievements that aptly illustrate the importance of nonlinear concepts in the geosciences. These include novel insights into fluid dynamics, such as the role of multiple large-scale flow patterns in the ocean and atmosphere, which greatly improved long-range weather forecasting; applications related to geophysical turbulence and stochastic dynamical systems; the development of vacillation theory, which led to the theory of strange attractors; and the concept of networks, whose applications include modeling aspects of climate dynamics such as the changes in sea surface temperature patterns associated with the El Niño–Southern Oscillation.

By offering a broad overview of the development and application of nonlinear concepts across the geosciences, the author affords researchers from numerous disciplines an opportunity to reflect on the importance of nonlinearity for understanding geological and geophysical phenomena.

The logical next step, the author argues, is to apply the ideas he presents to the problem of prediction, which will serve as a crucial test of geoscientists’ physical and mathematical understanding of the natural world. (Earth and Space Science, https://doi.org/10.1029/2019EA000599, 2019)

—Terri Cook, Freelance Writer

Green and Grand: John Wesley Powell and the West That Wasn’t

Thu, 05/23/2019 - 13:19

The American West, while steeped in mythology, is also a region that depends heavily on science for its long-term livability—and perhaps no one was quicker to realize that than John Wesley Powell. A Civil War veteran and an indefatigable explorer, Powell landed on the national stage in 1869, after an expedition he led became the first to navigate the Colorado River’s path through the Grand Canyon.

In the decades that followed, Powell would argue that careful, democratic management of water resources in the West must be a crucial component of its development and that a pattern of settlement and land cultivation based on the 19th century status quo would prove unsustainable.

He couldn’t have had a more unreceptive audience. Elected officials, industry titans, and even fellow scientists wanted a narrative that better supported the westward march of “progress,” narrowly defined.

Fast-forward 150 years, and Powell’s 19th century appeals are making modern headlines on the strength of their perception and foresight. Even while western states lead the nation in population and economic growth—Arizona, Colorado, Nevada, and Utah were among the top five states with the fastest growing gross domestic product between 2016 and 2017—drought conditions that have persisted for decades have left parched cities under constant threat of water emergencies.

On the Colorado River, the country’s two largest reservoirs—Lake Mead on the border between Nevada and Arizona and Lake Powell (so named for John Wesley) on the border between Arizona and Utah—are being drained faster than they can replenish. The effects of climate change are only adding to the pressure on limited water supplies.

In Powell’s account of his explorations, published in 1895 as Canyons of the Colorado, he describes the river’s waters emptying “as turbid floods into the Gulf of California.” Today, only in very wet years does the river reach the ocean. Meanwhile, communities that rely on the Colorado for water, including sprawling metropolitan areas like Phoenix, Denver, and Los Angeles, are facing the possibility of having their supply cut off or severely limited in a future that’s moving alarmingly nearer.

Unforeseen Potential

It’s tempting, then, to imagine how the West might have evolved had Powell’s vision for its development been implemented, rather than shunned, a century and a half ago.

What if Congress, undeterred by the siren song of American expansion, had listened to the call of the pragmatic?

Would L.A. be a backwater?

Would Tucson even appear on the map?

Would the Colorado still rush freely to the gulf from its headwaters in the Rocky Mountains?

Speculation about what might have been is complicated by society’s shifting priorities and values, as well as by technology. Powell, for his part, envisioned much smaller communities dispersed over the western landscape.

“One of the big things that would’ve happened if we’d listened to Powell is that we…would have responded earlier to the information about global climate change.”“One thing that he didn’t anticipate [was] the degree to which we would accumulate western society in big, urban complexes,” says Jack Schmidt, the Janet Quinney Lawson Chair in Colorado River Studies at Utah State University and former chief of the U.S. Geological Survey’s (USGS) Grand Canyon Monitoring and Research Center.

Powell, Schmidt says, might not have imagined that these urban complexes “would have these tentacles that extended way out into the distant landscape [or] the degree to which these big urban centers would be maintained by these really long canals…these really complicated electricity transmission systems that bring in power from distant coal-fired and nuclear and hydroelectric dam facilities.”

Although Powell’s vision of small communities was largely focused on irrigated agriculture, water management, he thought, would be developed at a more local scale. This would, among other benefits, help to hedge against the uncertainties of climate variation. When, for instance, the 1922 Colorado River Compact apportioned shares of Colorado River water to seven states, it was during a particularly wet period, leading to overestimated water allocations.

“One of the big things that would’ve happened if we’d listened to Powell is that we…would have responded earlier to the information about global climate change,” says John F. Ross, author of The Promise of the Grand Canyon: John Wesley Powell’s Perilous Journey and His Vision for the American West. “He was a great proponent of America’s potential; he just wanted to do it in a way that was sensible to what was on the ground.”

When the West Was Young

The Union Army major—who was injured while fighting in the Battle of Shiloh—conquered the unpredictable 1,600-kilometer route with one arm, a small fleet of wooden rowboats, and a cobbled-together team of nine willing but inexperienced adventurers.In 1869, as the post–Civil War United States was knitting itself back into a union, the sparsely settled expanse of states and territories that stretched between the 100th meridian and the Pacific coast was still a great unknown for many Americans. That year, Ulysses S. Grant was inaugurated as the 18th president of the United States, Wyoming became the first U.S. state or territory to grant women’s suffrage, and a spike driven at Promontory Summit in Utah connected the country’s first transcontinental railroad.

To many communities in the East and Midwest, the newly accessible West was brimming with possibility and scarcely tapped resources. John Wesley Powell, then a professor of geology at what is now Illinois State University, had identified an opportunity as he contemplated the last blank spot on the map of the continental United States: the Colorado Plateau. Today it’s an area made up of eight national parks—including Arches, Zion, and Grand Canyon—and nearly two dozen national monuments, historic sites, and recreation areas. In Utah alone, the region’s five national parks brought in 15.2 million visitors in 2017.

But in the late 19th century it was an altogether different story. When Powell undertook the 3-month descent of the Colorado River in the name of science, the journey was considered by some to be all but suicidal. Still, the Union Army major—who was wounded while fighting in the Battle of Shiloh—conquered the unpredictable 1,600-kilometer route with one arm, a small fleet of wooden rowboats, and a cobbled-together team of nine willing but inexperienced adventurers (all white men).

Powell’s expedition down the Colorado was honored by the U.S. Postal Service on the expedition’s centenary in 1969. Credit: U.S. Bureau of Engraving and Printing, Smithsonian National Postal Museum

The expedition departed from Wyoming’s Green River City on 24 May 1869, with 10 months’ worth of supplies, an optimistic collection of scientific tools, and, among some of the men, hopes of finding a fortune. Four men would eventually abandon the expedition, one at the first opportunity and three others less than 2 days before the remaining team successfully emerged from the Grand Canyon. (Those three men were never seen or heard from again.)

John Wesley Powell at age 35, the year he led the first expedition down the Colorado River and through the Grand Canyon. Credit: USGS

Although Powell’s scientific ambitions for the expedition were largely scuttled by the demands of survival, the widely heralded trip would help to launch his decades-long career as a geologic surveyor, shrewd political player, and government administrator. His recommendations to Congress would be instrumental in the creation of the U.S. Geological Survey, and he would later serve a dozen years as its director while also leading the Smithsonian’s Bureau of Ethnology and helping to found the Cosmos Club and the National Geographic Society.

But it was Powell’s unswaying advocacy for land and water management in the West that would prove to be one of his most remarkable legacies.

A Watershed Idea

It was the railroad that made it possible for Powell and his team to launch the expedition from the banks of the Green River. The conveniently located station at Green River City meant that Powell could easily bring his boats and supplies by train. But the technology that benefited Powell’s plans in 1869 would also facilitate the idealistic expansion that he would ultimately spend the latter part of his career warning against.

The completion of the transcontinental railroad was especially timely for a nation in pursuit of Manifest Destiny, which disregarded the realities of climate and the native peoples who occupied the land in favor of spreading American industrialism and progress from coast to coast. Politicians, speculators, and homesteaders were eager to exploit the promise of the West’s seemingly endless resources and would be quick to deny the hard truth that lives and livelihoods depended on one all-important ingredient: water.

In his 1879 Report on the Lands of the Arid Region of the United States, with a More Detailed Account of the Lands of Utah, with Maps, Powell foresaw the consequences of applying American optimism—and opportunism—in a part of the country where annual rainfall measured below 50 centimeters a year. He warned that there wasn’t enough water to support large-scale farming or the rapid settlement of federal lands stimulated by the Homestead Act of 1862. In addition, the costs of establishing effective irrigation systems threatened to keep control out of the hands of small farmers.

Certain conditions, Powell said, had to be met to develop the region successfully, including the identification of irrigable areas and local control of dam and irrigation projects.

It was a position Powell would refuse to abandon.

As director of the USGS in 1890, Powell presented this map of western watersheds (drainage districts) to Congress. Credit: USGS

While testifying before a congressional committee in 1890, when he was head of the USGS, Powell deployed a unique visual aid: a map that divided the western states and territories into a series of drainage districts.

On first viewing, it’s a surprising example of 19th century cartography, made all the more striking with rich colors and irregular, organic-looking boundaries that contrast sharply with the boxy borders we’re familiar with today.

But the schematic didn’t hold water, so to speak, with a nation determined to grow and expand. The outlook of the nation was invested in myths that encouraged development and defied science, whereas Powell, Schmidt says, lacked the tolerance for pursuing such myths, including the widely held belief that “rain follows the plow.”

In 1902, the year Powell died, Congress passed the Reclamation Act to “reclaim” the arid region for agriculture and settlement.

“That set the stage for this really large-scale water development in the West that almost defied the functioning of the watershed from an ecological perspective,” says Sandra Postel, founder and director of the Global Water Policy Project and author of Replenish: The Virtuous Cycle of Water and Prosperity.

Today, “the river is really operated more according to needs for hydropower, flood control, irrigation, and water supply,” Postel says. “You couldn’t have cities like Las Vegas and Los Angeles and Phoenix and Tucson without this extra water.”

In the Same Boat

Powell “introduced the idea that arid cultures either stood or fell…not on the absolute amount of water, but on how equitably—politically and economically—the system divided that resource.”Although deeply unpopular at the time, today, it’s apparent that Powell’s insistence on viewing the West’s water problem with scientific objectivity was a forward-thinking approach. Now science is taking a leading role in helping to reclaim the region for the environment while facilitating ways for a growing population to live there sustainably.

Powell believed that “science is a process of continually improving the details of our understanding of natural processes, and he would be very proud of the role of science in informing river management and protection,” says Schmidt.

According to Ross, Powell set the stage for the type of conversation we should be having about our natural resources. “He introduced the idea that arid cultures either stood or fell…not on the absolute amount of water, but on how equitably—politically and economically—the system divided that resource,” he says.

This boat, the Emma Dean, carried Powell and his characteristic chair down the Colorado in 1872. Credit: National Park Service

And what lessons can be taken from Powell as the West moves forward?

Says Ross, “We’re seeing this kind of bioregionalism now, where decisions are made not by the federal government but on a more local, or regional, basis—[which is] really the only way to work out these very knotty issues.”

Postel says that successful restoration often involves collaboration, such as conservationists working with farmers to find solutions to water management issues.

“If we get smarter about using and managing water, we can do better with what we’ve got than we’re currently doing,” she says.

As the challenges and accomplishments of western settlement continue to ebb and flow, Powell’s influence still lingers.

Like Postel, Schmidt believes that the key to water management in the West is in working together as a watershed community. “In a sense, that’s an idea of Powell’s that still exists today. It’s just that the community that we call the watershed includes the entire Colorado River basin. It includes every one of the seven states, all sitting around the table together.”

—Korena Di Roma Howley (korenahowley@gmail.com), Freelance Journalist

No Underground Magma Ocean on Jupiter’s Fiery Moon?

Wed, 05/22/2019 - 11:46

Jupiter’s closest Galilean moon, Io, is the most volcanically active object in the solar system. Kneaded and heated by Jupiter’s rhythmically reversing tidal stresses, the moon hosts hundreds of active volcanoes, some of which spew lava and sulfur dioxide more than 400 kilometers high.

Scientists have long argued over whether Io’s intense volcanic activity is fueled by an underground ocean of magma. Now a new analysis of data from the Galileo spacecraft provides fresh fodder for that debate, suggesting that such an ocean could be absent.

Galileo flew past Io several times in the late 1990s and early 2000s, including a risky pass between Io and Jupiter that exposed the spacecraft to intense radiation and temporarily damaged its computers. Despite the technical glitch, Galileo collected valuable measurements from the hot, ionized gas—or plasma—that escapes from Io into Jupiter’s magnetosphere, feeding a donut-shaped ring of dense plasma around Jupiter called a torus. It also captured interactions between Jupiter’s powerful magnetospheric plasma and Io’s thin atmosphere, which produce brilliant auroras.

On the basis of Galileo’s data, some scientists have concluded that Io’s own magnetic field is driven by a subterranean magma ocean. As Jupiter’s magnetic field sweeps back and forth across the moon, the theory goes, it generates electrical currents within a global conductive ocean of molten rock. This process produces its own magnetic field, which contributes to massive perturbations in the surrounding magnetic field of Io.

But in the new study, Blöcker et al. argue that the measured magnetic perturbations in Io’s environment come instead from asymmetries in Io’s thin atmosphere. Io’s entire atmosphere collapses into frost on a daily basis, whenever it falls into Jupiter’s shadow. The atmosphere is also larger and denser on the side of the moon that faces away from Jupiter. On a local level, massive volcanoes also make Io’s atmosphere irregular. Computer models used in past studies haven’t focused much on these asymmetries, leaving room for error, the team argues.

To remedy that omission, the scientists used the same type of computer model that past groups have employed, called a 3-D magnetohydrodynamic model. Instead of focusing on Io’s interior, they focused solely on the moon’s atmosphere. Their goal was to see if an asymmetrical distribution of gas in Io’s atmosphere alone, independent of any contribution from a global conductive magma ocean in Io’s interior, could produce magnetic perturbations similar to those observed by Galileo.

The model produced the same magnetic field perturbations in Io’s simulated atmosphere as those observed by Galileo. The study doesn’t entirely rule out the possibility that an underground magma ocean could exist on Io, but it suggests that there’s no need for one. Instead, the moon’s unusual atmosphere accounts for Galileo’s observations all on its own. (Journal of Geophysical Research: Space Physics, https://doi.org/10.1029/2018JA025747, 2018)

—Emily Underwood, Freelance Writer

Historic Solutions to Sea Level Rise May Help Modern Communities

Wed, 05/22/2019 - 11:45

For centuries, fighting rising sea levels has been a regular part of life for people in the Netherlands. Since the early 20th century, archeologists have been digging into how humans adapted and thrived in these flooded environments.

Settlers in the low-lying region of what is now the northern Netherlands built elevated platforms on the land, protecting their homes, crops, and livestock from the rising ocean and frequent flooding. These constructed landforms were highly successful, allowing settlers to thrive in low-lying lands for more than 1,500 years.

Although most research documenting such early engineering practices has been presented to archaeological societies and in archaeological journals, these ancient adaptations to flooding might be of interest to other modern communities, especially those concerned with coastal management and policy.

“I wanted to show the results of our research to a wider audience than just archaeologists,” says Annet Nieuwhof, an archaeologist at Groningen Institute of Archaeology at the University of Groningen in the Netherlands and lead author of a new paper in Ocean and Coastal Management. “I think we can contribute something to the problems of today with rising sea levels, because that is exactly what people in the past were also dealing with.”

Living in Salt Marshes

Salt marshes on the northern coast of the Netherlands have been home to settlers since around 650 BCE. The fertile soils that attracted settlers to the area were created by the same processes that threatened their settlements: floods. This land experienced storm surges and flooding, as well as moderate sea level rise—about 3 to 4 centimeters of rise per century—which inundated their homes.

To deal with flooding, settlers built raised platforms of sediment called terps. A terp is a dwelling mound specifically built to allow humans to adapt to a regularly flooded area.

“The terp has a long history,” says Nieuwhof. She and her colleagues pieced together the history and evolution of terp settlements in the northern Netherlands by using a large data set of archaeological research collected over the past few decades, including excavations of terps and age dating of buried finds within the platforms.Early terps were built for a single home and were modest in height—only about 0.4 to 1 meter above what were likely the highest expected flood levels.

The Evolution of Terps

Terps were not simple piles of dirt, says Nieuwhof, but engineered structures that were resistant to erosion and could support a house without sagging. Early terps were built for a single home and were modest in height—only about 0.4 to 1 meter above what were likely the highest expected flood levels.

Over time, this subtle rise was not enough protection. In addition to the slow sea rise, colonizers living on terps during the pre-Roman Iron Age (about 500 to 1 BCE) began to unintentionally undermine their settlements.

“They dug ditches to reclaim the area, to cultivate the area, and they started plowing,” says Nieuwhof. “That caused oxidation of the peat and subsidence—that made the whole area very vulnerable to the sea.”

Under threat of inundation, colonizers increased both the height and area of the platforms. Nieuwhof explains that eventually, individual terps grew together, creating raised surfaces several meters high and big enough to include room for gardens or even fields. These expanded terps hosted small communities, sustaining populations of 15–20 people per square kilometer.

Historic Solutions for Modern Problems?

Understanding how humans have dealt with past sea level rise could be helpful in present-day coastal management strategies.

“That type of perspective is really valuable and important because it helps us to look at long-term responses of landscape to human manipulation.”“This [paper] is a really nice synthesis of how people interacted with this coastal landscape over more than a thousand years,” says Elizabeth Chamberlain, a postdoctoral fellow at Tulane University who was not involved with the study. “That type of perspective is really valuable and important because it helps us to look at long-term responses of landscape to human manipulation.”

Chamberlain mentions that directly applying the same engineering solutions to present-day conditions isn’t a one-to-one approach.

One big difference is the number of people at risk: Terps supported up to 20 people per square kilometer, but “in contemporary times, the population density [in that area] is roughly 488 people per square kilometer,” says Chamberlain. In places like Bangladesh, she notes, population density is even higher, averaging more than a thousand people per square kilometer on the delta plain.

Even with these population differences, Chamberlain says it’s really useful to have this kind of historical information, especially for region-specific strategies for at-risk coasts. “You can pull the components that are most valuable for present-day society and try to engineer better and more sustainable systems by building with nature,” she says.

Adjusting to sea level rise will likely mean societies will have to adjust to new protections.

“In the Netherlands, we trust just our dikes, I think, a bit too much,” says Nieuwhof. She says it may be time to revisit the older strategies for new ideas. “We have to try other things and experiments—perhaps lower dikes to allow some flooding, perhaps live on terps again in some areas.”

—Sarah Derouin (@Sarah_Derouin), Science Writer

Low-angle Normal Fault in Papua New Guinea is Rolling Along

Wed, 05/22/2019 - 11:30

Low-angle normal faults are recognized in both oceanic and continental extensional regimes and are commonly associated with metamorphic core complexes. These core complexes are comprised of suites of crustal rocks that have been exhumed to the surface from significant depths, and that record deformation associated with crystal-plastic as well as brittle (seismogenic) processes. The mechanisms by which low-angle normal faults exhume rocks from such deep crustal levels, however, are unclear.

Through a combination of detailed geologic and structural observations and geomorphic mapping, Mizera et al. [2019] present a detailed analysis of the geometry and kinematic evolution of the Mai’iu fault, an active low-angle normal fault that bounds the Dayman Dome metamorphic core complex in Paupa New Guinea. Progressive tilting of the fault surface accompanying exhumation supports a “rolling-hinge” model of extensional tectonism, in which deep crustal plastic flow isostatically uplift and domes the tectonically denuded metamorphic core complex in the foot wall of the fault.  This study should be of wide interest due to the ubiquity of low-angle normal faults in both extensional and contractional orogenic belts globally.

Citation: Mizera, M., Little, T. A., Biemiller, J., Ellis, S., Webber, S., & Norton, K. P. [2019]. Structural and geomorphic evidence for rolling‐hinge style deformation of an active continental low‐angle normal fault, SE Papua New Guinea. Tectonics, 38. https://doi.org/10.1029/2018TC005167

—Nathan Niemi, Editor, Tectonics

New Stamps Tell a Wild and Scenic River Story

Tue, 05/21/2019 - 18:40

The Flathead, Deschutes, Ontonagon, and Koyukuk are among more than 200 waterways protected by the U.S. National Wild and Scenic Rivers System. They are also among the 12 free-flowing rivers splashing, burbling, and cascading in an evocative set of Forever stamps that the U.S. Postal Service (USPS) is issuing starting today, 21 May.

Nearly 51 years after U.S. President Lyndon Johnson signed into law the Wild and Scenic Rivers Act in August 1968, USPS is printing up 5 million panes of the 12-stamp collection for a total of 60 million stamps

“Holy mackerel!” Tim Palmer, one of the photographers featured in the stamp set, told Eos upon hearing about the number of stamps being printed.

That’s more than 2,660 first-class letters that can be posted for every kilometer of the Wild and Scenic Rivers System, which currently protects more than 22,530 kilometers of riverways. That includes 418 kilometers added in March to the system that designates and protects rivers and river stretches as wild, scenic, or recreational.

Stamps That Represent the Best of America

The postal service views its job in printing stamps “as representing the best of America.”Scenic stamps do very well with the general public, said William Gicker, acting director of USPS Stamp Services. The postal service views its job in printing stamps “as representing the best of America. And we want to do things that are, of course, also popular with the American buying public,” he told Eos. These river stamps fit both criteria, he said.

Each year, the Citizens’ Stamp Advisory Committee, appointed by the postmaster general, receives about 40,000 requests for new stamp designs, and USPS issues about 25, Gicker noted.

This new set of stamps, designed by USPS art director Derry Noyes, includes spectacular photographs of rivers from across the United States by three of the country’s best nature photographers: Michael Melford, who has been featured in National Geographic magazine and elsewhere; Bureau of Land Management staff photographer Bob Wick; and naturalist and author Palmer, who has written extensively about the Wild and Scenic Rivers System.

The U.S. Postal Service has issued a set of 12 stamps celebrating the National Wild and Scenic Rivers System. Credit: USPS A Special Stamp of Montana’s Flathead River

Among Palmer’s four photos featured in the stamp set is a picture of Montana’s Flathead River near Glacier National Park. That exact location, a narrow stretch along the river, is the site where the U.S. Army Corps of Engineers in the 1950s had proposed building the Spruce Park Dam. During a successful fight to block that dam, pioneering wildlife biologists John and Frank Craighead made a case for protecting the nation’s remaining wild rivers, according to Palmer. “That was the seed that grew into the National Wild and Scenic Rivers Act,” he said.

“I actually would have run in to get an even earlier morning photo except that’s prime grizzly bear country and I did not want to surprise a bear by approaching quickly on a dark trail.”The photo shoot was pretty special, too, according to Palmer, author of a number of books, including Wild and Scenic Rivers: An American Legacy and America’s Great River Journeys: 50 Canoe, Kayak, and Raft Adventures.

“It was just a beautiful summer morning. You’re high in the mountains, so there is that cool brisk air of the northern Rockies, and it’s pine and fir scented because it’s all coniferous forest there. And this magnificent crystal clear water was just bubbling through and rushing by,” he recalled. “The rocks are this gorgeous mosaic of metamorphic color: red, gray, blue, black, white.”

Palmer said that he got up before dawn to hike the 12 kilometers to the site. “I actually would have run in to get an even earlier morning photo except that’s prime grizzly bear country and I did not want to surprise a bear by approaching quickly on a dark trail,” he added.

Photography “Makes You See”

Palmer’s other photos in the stamp set include a sunrise shot of Washington’s Skagit River, a “classic scene” of Wyoming’s Snake River, and a shot of Michigan’s Ontonagon River rushing through a lush gorge.

“The really wonderful thing about photography is that it makes you see,” he told Eos. “We can all be looking at things but not really seeing them. When you’re there to take a photo, you’re looking deeper: for light and for movement and for contrast and for color.”

Michigan’s Ontonagon River is one of hundreds protected by the Wild and Scenic Rivers System. Credit: USPS

There is something “extremely refreshing” about entering this other world “of just astonishing beauty,” he said, summing up his experience of photographing rivers.

“All of this begins to build emotionally. I’m there physically, it’s fun, it’s a beautiful scene, I’m enjoying that. The river is making these wonderful sounds. And I’ve got a creative mission to accomplish here, which is to capture the photos,” he said. “I realize that all of this is for sharing it with other people and the rest of the world so that they, too, can know the value of wild rivers and therefore protect them.”

Gicker at USPS added that one of the biggest challenges of designing stamps is creating “an impactful image in a very small size that captures your attention and imagination very quickly.”

Gicker told Eos that he hopes people will see these river stamps as “a little light in their day” and “stop to think about what this country is. It’s not just the highways that [we] see driving to work.’”

—Randy Showstack (@RandyShowstack), Staff Writer

Farm Ponds Sequester Greenhouse Gases

Tue, 05/21/2019 - 12:22

The world’s farmers nourish their fields with more than 120 million metric tons of nitrogen-based fertilizer each year. Nitrogen is a key component of chlorophyll, and it’s necessary for photosynthesis, but it’s not harmless, and when it’s used in fertilizer, it doesn’t just stay in the soil.

A small percentage of the nitrogen in fertilizers is converted into nitrous oxide (N2O), a gas that accounts for about 5.6% of total greenhouse gas emissions in the United States. Nitrous oxide traps heat at about 300 times the rate of carbon dioxide and can comprise as much as half of a farm’s warming effects.

In North America’s Great Plains, tens of thousands of farm ponds store water for livestock and irrigation, and they’re squarely in the path of fertilizer runoff from large-scale agriculture throughout the region.

Researchers found that farm ponds “were undersaturated and were actually acting as N2O sinks, which was a big surprise.”Kerri Finlay, an assistant professor of biology at the University of Regina in Canada, and Jackie Webb, a postdoctoral fellow in biology at the University of Regina, hypothesized that these ponds would be heavy greenhouse gas emitters. Most inland bodies of water are sources of greenhouse gases, even without regular nitrogen deposits.

“We assumed that with all of the nitrogen fertilizer on the landscape there would be quite a lot of N2O emitted,” says Finlay.

“But we found they were undersaturated and were actually acting as N2O sinks, which was a big surprise.”

The researchers sampled emissions from 101 farm ponds in the Canadian province of Saskatchewan and found that just over two thirds of them were acting as N2O sinks. Their results were published in the Proceedings of the National Academy of Sciences of the United States of America.

Engineering Ponds to be N2O Sinks

Finlay and Webb are working on guidelines that could help farmers turn existing ponds into sinks and build new ones to absorb gases from the outset. To help with this, they have identified key characteristics associated with the ponds that were not N2O emitters.

Most of the N2O sinks were more than 3 meters deep and were surrounded by small hills that shielded them from the wind. Deep, still water encourages the growth of algae, which consume nitrogen before it becomes a gas. Eventually, the algae die and fall to the bottom of the pond, never allowing the nitrogen to escape into the atmosphere.

The researchers aren’t focused only on N2O in farm ponds. High soil pH levels in the study area mean that carbon dioxide in the ponds is converted to other forms of dissolved carbon, meaning the ponds act as carbon sinks as well as nitrogen sinks. Like pond depth and wind shelter, the pH level of ponds can be controlled.

“We are looking for consistency in the characteristics that keep methane, carbon dioxide, and N2O low.”Finlay and Webb also found that some ponds had low methane emissions, but they aren’t yet sure why.

“We are still trying to work that out,” Finlay says. “But we are looking for consistency in the characteristics that keep methane, carbon dioxide, and N2O low. We think we can find a subset of sites like that, and may be able to manage other sites to shift to that.”

Building guidelines for agricultural ponds could help transform a necessary farm installation into a carbon offset, but the policy instruments to encourage this don’t yet exist.

“We don’t have monitoring, reporting, and verification in place,” says Margot Hurlbert, a coordinating lead author of the Intergovernmental Panel on Climate Change’s Special Report on Climate Change and Land. Hurlbert was not involved in the farm pond study.

“But some countries are beginning to think about how to bring agricultural practices into the system, so that farmers can benefit from them. That would be really exciting, but currently it’s a gap. If we were to get serious about monitoring, verification, or reporting greenhouse gas emissions, then there could be a linkage.”

—Ty Burke, Science Writer

New Book Examines the Legacy of Apollo

Tue, 05/21/2019 - 12:21

With the 50th anniversary of the Apollo 11 Moon landing around the corner on 20 July, celebrations, recollections, and analyses of that historic achievement aim to fill up television screens and weigh down bookshelves.

Now a new book by former NASA chief historian Roger Launius provides a look back, from a U.S. outlook, at the political, technological, and economic challenges in the race to the Moon and that first Moon landing. The book, filled with drama even though we know the outcome, provides fascinating perspectives about the meaning and legacy of the Moon landing.

“The astronauts who first landed on the Moon half a century ago carried with them the hopes and wishes of all whom they had left behind on Earth, as well as uncertainty about what they would experience on the lunar surface,” Launius writes in Apollo’s Legacy: Perspectives on the Moon Landings, which was released this month. “Setting foot on another world, they knew, would be the climax of humanity’s greatest adventure to date.”

“Virtually everyone embraced the flight of Apollo 11 as a shared success for the planet.”Indeed, Launius notes that former U.S. president Richard Nixon declared that the Apollo Moon landing made for “the greatest week since the beginning of the world, the creation,” and former NASA rocket developer Wernher von Braun compared the landing to the moment when the first creature left the sea for dry land.

“All of these were overstatements, but virtually everyone embraced the flight of Apollo 11 as a shared success for the planet,” Launius writes.

However, he details in the book, that success and the road leading up to it were immediately more beneficial for the United States in its efforts to challenge the former Soviet Union and show the world its technological prowess.

The Space Race as a Cold War Battle

Events moved dizzyingly fast at the start of the space race, which came in the middle of the Cold War between the United States and the former Soviet Union. Less than 3 months after President John F. Kennedy was sworn into office on 20 January 1961, Soviet cosmonaut Yuri Gagarin became the first human to orbit Earth on 12 April. Five days later, on 17 April, the United States launched its botched invasion of Cuba at the Bay of Pigs.

Then, on 21 April, Kennedy announced at a press conference, “If we can get to the Moon before the Russians, then we should.”

That statement, an example of the kind of detailed information included in Apollo’s Legacy, came more than a month before Kennedy’s 25 May historic address to Congress. That’s when Kennedy declared, “We choose to go to the Moon in this decade and do the other things, not because they are easy, but because they are hard.”

From there, it was off to the (space) races, with an enormous national commitment to overcome technological and other challenges to reach the Moon.

Lunar module pilot Edwin “Buzz” Aldrin faces the U.S. flag on the lunar surface. Credit: NASA History Office

“Through Apollo, two American presidents came to appreciate the power of science and technology to increase confidence in the US government both abroad and at home,” writes Launius, who also previously served as associate director of collections and curatorial affairs at the Smithsonian’s National Air and Space Museum. “Indeed, at a fundamental level both John F. Kennedy and Lyndon B. Johnson consciously used Apollo as a symbol of national excellence to further their objectives of enhancing the prestige of the United States throughout the 1960s.”

A “Moondoggle”?

Some thought the concept was a “moondoggle.”Not everybody was on board with the race to the Moon, Launius explains as he explores different perspectives and disagreements. Some, on both the political right and left, thought the effort was a “moondoggle.”

Launius writes that former president Dwight D. Eisenhower cautioned that the Moon race “has diverted a disproportionate share of our brain-power and research facilities from equally significant problems, including education and automation.” And Congress challenged the enormous funding request for NASA.

Later, Launius writes, civil rights leaders from the Southern Christian Leadership Conference (SCLC) protested the Apollo 11 launch to draw attention to the plight of poor people in the United States.

In an evocative scene, Launius details a meeting between Ralph Abernathy, Hosea Williams, and other SCLC leaders with then NASA administrator Thomas Paine near the launch site the day before liftoff.

Drawing on Paine’s record of the incident, Launius writes that Paine “commented on how hard it was to apply NASA’s scientific and technological knowledge to the problems of society.” Launius quotes Paine as commenting, “The great technological advances of NASA were child’s play compared to the tremendously difficult human problems with which [Abernathy] and his people were concerned.”

Launius writes that Paine asked the SCLC group to pray for the safety of the astronauts. Abernathy, an ordained minister, “responded with emotion that they would certainly pray for the safety and success of the astronauts, and that as Americans they were as proud of our space achievements as anybody in the country,” according to Paine.

Even after the Moon landings, a few people were not convinced that they happened, dismissing the landings as a hoax. Launius includes an interesting chapter about this.

Some people, including Launius’s paternal grandfather, simply thought the landings were technologically impossible.

With a spectacular earthrise on the horizon, Apollo’s lunar module approaches the command and service module (the mission’s “mothership”) for docking and the return trip to Earth. Credit: NASA History Office The Legacy of Apollo

“NASA’s engineers and scientists went to the Moon, one of the hardest tasks ever accomplished; might we be able to solve equally challenging problems in the future in a similar manner,” such as dealing with climate change, global population, water scarcity, or other issues?Apollo advanced technology, science, and people’s perspective of our home planet, among other things.

But, Launius asks, what is the real legacy of Apollo?

“Apollo had shown that virtually anything was possible,” he writes. “NASA’s engineers and scientists went to the Moon, one of the hardest tasks ever accomplished; might we be able to solve equally challenging problems in the future in a similar manner,” such as dealing with climate change, global population, water scarcity, or other issues?

Launius notes that these and other problems are largely political and social issues, with more limited potential for applying the sort of technical solutions that dominated the Apollo program. “Will they also be solvable using those lessons from Apollo? In other words, ‘If we can put a man on the Moon, why can’t we do X?’” he asks.

The author also wonders how much the race to the Moon was a product of a particular moment in time that motivated the public and convinced Congress to open the federal coffers. “Returning to the Moon certainly will not happen again anytime soon without a major realignment of rationales, needs, and priorities,” he writes.

With U.S. Vice President Mike Pence recently calling for the country to put an American astronaut back on the Moon in the next 5 years and with the Trump administration on 13 May requesting an extra $1.6 billion to help make that happen, time will tell whether the administration’s realignment will bear fruit.

—Randy Showstack (@RandyShowstack), Staff Writer

Mud on the Move

Tue, 05/21/2019 - 12:19

The Congo River doesn’t end where it meets the Atlantic Ocean—not by a long shot. You can follow pulses of its sediment-laden water for hundreds of kilometers as they shoot away from the coast of Africa, down the continental slope, through a canyon that in places cuts a kilometer deep, and eventually deposit their load in a fan-shaped formation the size of Arizona.

These pulses are called turbidity currents. They form when water becomes so heavy with sediment (hence turbid, or muddy) that the weight of the particles drives the mixture down a slope. The currents are often released from rivers but also can originate at sea, caused by earthquakes, landslides, tides, and even activity from fishing trawlers.

Turbidity currents occupy the minds of scientists of all stripes: Engineers worry about the damage they can do to submarine infrastructure; oceanographers want to understand how they sculpt the areas they traverse; geologists study the formations (turbidites) they leave behind. And climatologists are starting to reckon with the capacity of the largest turbidity flows to help regulate climate.

“The flows in the Congo Canyon seem to carry about 2% of the organic carbon that is transported into the deep ocean over the whole world every year. Just this one canyon.”Every year, for instance, the Congo Canyon serves as a conduit to the ocean floor for tens of millions of tons of organic matter culled from the river’s watershed on the African continent. The submarine canyon keeps the carbon-rich sediment removed from the atmosphere for millions of years, in which time it may give rise to oil and gas fields.

“The flows in the Congo Canyon seem to carry about 2% of the organic carbon that is transported into the deep ocean over the whole world every year. Just this one canyon,” said Matthieu Cartigny, an Earth scientist from Durham University in the United Kingdom. “There are many, many submarine canyons in the world. So these processes must play a dominant role, impacting the carbon cycle and thereby the climate.”

Elucidating the role of these flows in the world’s climate is an important reason to study turbidity flows. Another is to prevent these forces of nature from colliding with human infrastructure under the waves.

A classic example of this interference happened in 1929, when 12 transatlantic cables snapped after the magnitude 7.2 Grand Banks earthquake off the eastern coast of Canada. Five of these cables broke 13 hours after the quake, one after the other, from north to south. Not until more than 2 decades later did Bruce Heezen and Maurice Ewing of Columbia University put forward a solution to the mystery: The earthquake had caused an undersea landslide, and a turbidity current had propagated toward the cables and taken them out.

While communications technology progressed, data collection on the phenomenon hardly did. In 2006 and 2009, turbidity flows in the Gaoping Submarine Canyon off Taiwan caused fiber-optic cables between North America and Asia to break. From the distances between the cables and the times of failures, the currents’ velocities were estimated to lie between 5.6 and 12.6 meters per second (20–45 kilometers per hour). But that was about all that could be said.

From “Nigh unto Impossible” to “Doable”

A picture has emerged of turbidity currents as an intricate dance of fluid and solids—not just a muddy submarine river that stops and starts, but also a flow in a class of its own.“The general feeling was, it’s nigh unto impossible to actually study flows in the field in real time,” recalled Charlie Paull of the Monterey Bay Aquarium Research Institute (MBARI) in California. “For one, you need to go to a place where you’re likely to have something happen during the experiment, and there are precious few places on the Earth where we historically know that this will be possible. The flip side is, if you’ve found a place, you would have the nightmarish problem of putting expensive gear down and standing a high chance of losing it” to the onrushing cascade.

For that reason, researchers were forced to rely mostly on laboratory experiments, computer models, and analysis of geological features.

But in the past few years, “nigh unto impossible” has turned into “doable,” partly thanks to equipment that can study current velocities at a safe distance.

There are now a number of locations where turbidity currents have been studied in detail. One of them is the Monterey Canyon, at the head of which, conveniently, Paull’s MBARI is located. Another is the delta of the Squamish River in British Columbia in Canada. And a third is a stretch of the Congo Canyon.

From those places, each of which was studied using different instruments and focusing on different aspects of the currents, a picture has emerged of turbidity currents as an intricate dance of fluid and solids—not just a muddy submarine river that stops and starts, but also a flow in a class of its own.

Tumbling, Racing Sediments

For getting a handle on what occurs in the Congo Canyon, scientists can thank the caution shown by the Chevron oil company in 2009 and 2010, said Cartigny.

Turbidity currents emanating from the Congo River interact with the 280-kilometer-long Congo Canyon off the west coast of Africa. Credit: Mikenorton and NASA WorldWind

“Chevron wanted to cross the canyon with a gas pipeline. Then somebody said, ‘That’s a big canyon; you might want to check before you put that expensive pipeline there.’ They put some instruments in, and they found there’s lots of flows, and then they decided they had better directionally drill under the canyon, at 2 kilometers of water depth, at great cost. There was far too much activity. They published this in a very small conference abstract, saying it might be of interest to other people. My colleague Peter Talling [also at the University of Durham] contacted them and said, ‘Th[ese are] amazing data; could we have [them]?’”

For the past 6 years, Cartigny and his colleagues have been working with the data that Chevron had gathered from the deep, using downward looking acoustic Doppler current profilers, instruments that bounce sound off particles suspended in water to measure flow velocity.

Shown are bathymetric maps of (a) the area of the Congo Canyon in which turbidity currents were studied and (b) the two mooring sites deployed by Chevron. The contours in the first map are displayed in meters. Credit: Azpiroz-Zabala et al., 2017, https://doi.org/10.1126/sciadv.1700200, CC BY 4.0

The scientists were immediately surprised.

“We always thought such flows would last minutes, or hours, maybe a couple of days if the river is in a flood and carries a lot of sediment,” Cartigny said. “But they lasted for a week to 10 days, longer than we’ve ever seen before with such currents. Also, we now know that the front of the flow moves at 1.4 meters per second, and the tail only 20 centimeters per second. We had so many questions.”

Laboratory experiments had suggested that the dense front part, the “head” of the turbidity current, would be the slowest, as it has to push aside the surrounding nonturbid, nonflowing water. Sediment from behind, unhindered in that way, would come in faster and pile up against the head.

“There doesn’t seem to be a relation to any floods, earthquakes, undersea landslides, or storms. Something else is happening.”Instead, a turbidity current—at least when it is transporting very fine, muddy sediment, as in the Congo Canyon—is actually more like a powerful locomotive. This follows from an analysis of the measurements, published in the journal Science Advances by Cartigny’s Ph.D. student Maria Azpiroz-Zabala, now at Delft University of Technology in the Netherlands. The turbidity current’s head, heavy with suspended sediment, races downhill and scours the canyon. As long as the seafloor provides both grade and grime, this process can continue and, as the “body” of the sediment burst keeps lengthening, gives rise to the prolonged turbidity currents witnessed by the Chevron engineers.

Whether long or short, a turbidity current has to start somehow, somewhere. For the Congo Canyon, this is still a mystery, Cartigny said.

“There doesn’t seem to be a relation to any floods, earthquakes, undersea landslides, or storms. Something else is happening.”

Origins Predicted by Modeling

The origin of turbidity currents is easier to study with a smaller river and closer to shore.

Talling and Cartigny’s team has been observing just such a location, the delta of the Squamish River in British Columbia, which regularly launches turbidity flows. The flows were not seen directly, but their occurrence was deduced by measuring sudden changes in the submarine topography of the delta.

Jamie Hizzett of the University of Southampton in the United Kingdom, a Ph.D. student of Cartigny’s, published an analysis of conditions associated with Squamish turbidity currents in Geophysical Research Letters.

Concrete events triggered about a quarter of the 95 currents Hizzett studied. Chief among these were undersea landslides, caused by sediment accumulating along a steep gradient until it became unstable.

But the vast majority of the turbidity currents, 73%, arose much more peacefully, with the river bringing in sediment gradually but turbidity currents taking off intermittently.

Cartigny is excited by this result, as it meshes with mathematical analysis and computer modeling of the start of turbidity currents done by Ricardo Silva Jacinto of the French marine research organization Institut Français de Recherche pour l’Exploitation de la Mer (Ifremer).

Jacinto concurs.

“What we are observing around the world is that we may have [many] more turbidite currents than we thought, and they may already happen with fairly dilute suspensions,” he told Eos.

Such a suspension can become supercritical: Any perturbations in the flow will travel more slowly than the flow itself. That includes any compression of the front part of the sediment flow, which will then be overtaken by more sediment and become even more dense.

“And so everything is ignited,” Jacinto said.

Helical Flows

Once launched, turbidity currents turn out to behave in ways not seen in any other flows.

In another paper published in Geophysical Research Letters, Azpiroz-Zabala showed that as sediment shoots through the Congo Canyon, it doesn’t just veer left and right as its channel meanders but follows a helical path. Such secondary circulation occurs in rivers as well, but as Azpiroz-Zabala discovered using the Chevron data, turbidity currents give this phenomenon their own unique twist.

In a river, the circulation is set up when the current is forced around a bend and the centrifugal force pushes the water up against the outer bank. Along the bottom, the difference in the water level results in higher pressure near that bank, causing water to flow inward, with a compensating flow outward nearer to the surface. Thus, a cell of circulating water is set up. Added to the downstream water movement, this results in a helical flow.

Researchers saw two helical flows on top of one another: the upper one riverlike, the bottom one river reverse.Important for understanding the idiosyncrasies of turbidity currents, the water moving along the bottom from the outer toward the inner bank often will pick up sediment and thus become relatively heavy. As the river comes out of the meander and straightens, the higher pressure at the outer bank due to the centrifugal force weakens and is overpowered by the higher pressure at the inner bank due to the higher density of the water there. The resulting opposite circulation, more commonly seen in estuaries than in rivers, is called river reverse.

What pattern would dominate in turbidity currents? The observations of the Congo Canyon gave an answer no one expected: It’s both. As the flow started to leave the meander where the Chevron instruments were located, the researchers saw two helical flows on top of one another: the upper one riverlike, the bottom one river reverse.

In hindsight, having two patterns at once makes sense, as a turbidity current can be seen as two stacked rivers, with the top one upside down, Azpiroz-Zabala explained. “The fastest flow in a river is at the surface, but a turbidity current experiences friction both at the top, with the ambient water, and at the bottom. So the middle of the flow is going at the fastest speed.”

Breaking Ground Beneath the Currents

Whether the flows in the Monterey Canyon also display helical secondary circulation is not yet known, said Paull of MBARI. “I don’t think we’ve digested the data enough to make a serious comment about that. We’re still trying to understand the primary data set.”

For their recent study, Paull and his team made observations for 18 months, using not just acoustic Doppler current profilers but also dozens of other types of instruments. Their first result turned out to be literally groundbreaking.

The bottom of the Monterey Canyon itself, as well as outflow from the Salinas River, contributed to turbidity currents in Monterey Canyon in California. Credit: Earth Science and Remote Sensing Unit, NASA Johnson Space Center

Among the instruments researchers deployed were motion sensors, buried in the bottom sand like boulders. The sensors were expected to record how sand was moved by a turbidity current swooshing by. But what these “benthic event detectors” recorded instead was the canyon bottom itself moving downslope at speeds even greater than the water flowing over it.

“To what extent that was the preexisting bottom that is moving, and exactly how it’s moving, that’s still slightly murky,” said Paull. “But it is clear that a very dense layer down at the bottom is moving very quickly. And the turbulent cloud above, which is what many experiments have been measuring, is, at least in the Monterey Canyon, a by-product.”

That means that experimenters and computer modelers have some catching up to do, Paull said. “Models that don’t deal with a movable substrate but are done over a stainless steel surface at the bottom of a test tank are less valuable.”

Whether the bottom of the Congo Canyon also is an integral part of the turbidity currents there is something upcoming observations may establish. A cruise to place instruments at the canyon will take place in September 2019, and two more are planned for 2020 and 2021 for what is billed as “the first detailed measurements of turbidity currents in the deep-ocean.”

It won’t be easy, Paull predicts.

“The Monterey experiment took between 120 and 140 ship days. We could schedule things because it is right out our back door. We could launch multiple short day trips to talk to equipment on the seafloor, to see what its status was. We had instruments that would tell us if something happened, so we could launch event response cruises. It’s going to be hard in the Congo Canyon, going by for just a few times on a ship, in a very set time window. And it’s much deeper water. But [it’s] well worth trying!”

—Bas den Hond (bas@stellarstories.com), Freelance Journalist

Bill Would Create a Wildlife Corridors System to Protect Species

Mon, 05/20/2019 - 17:36

New legislation to establish a national system of wildlife corridors in the United States comes just days after a United Nations (UN) report on threats to biodiversity warned that about 1 million species worldwide are threatened with extinction.

The legislation, known as the Wildlife Corridors Conservation Act of 2019, would establish the wildlife corridors system to help native animal and plant species—including protected species—that face habitat loss, degradation, fragmentation, or obstructions to connectivity between their habitat areas.

The bill, which was introduced in Congress on 16 May, aims to help restore movement by wildlife and “to provide long-term habitat connectivity for native species migration, dispersal, adaptation to climate and other environmental change, and genetic exchange.”

In addition, the bill would establish a wildlife movement grant program on nonfederal land and water to increase wildlands connectivity. It would also include a wildlife corridors stewardship fund to help manage and protect the corridors.

“A Critical Step to Protect Wildlife”

The legislation is “a critical step to protect wildlife,” Sen. Tom Udall (D-N.M.), who introduced the legislation in the Senate, said at a 16 May briefing about the bill.

“While we are in the middle of a human-caused sixth mass extinction, scientists are raising the alarm. We are almost out of time to save the planet as we know it.”“While we are in the middle of a human-caused sixth mass extinction, scientists are raising the alarm. We are almost out of time to save the planet as we know it,” Udall commented, referring to the 6 May UN report by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services.

The report, which was compiled by 145 expert authors, states that the rate of global change in nature during the past half century “is unprecedented in human history.” It also found that the global rate of species extinction “is already at least tens to hundreds of times higher than the average rate over the past 10 million years and is accelerating.”

The report calls for urgent “transformative changes” to reverse the situation and states that direct drivers of change in nature that have the largest global impact are, in order, changes in land and sea use, exploitation of organisms, climate change, pollution, and the invasion of alien species. It warns that the future impacts of climate change on biodiversity and ecosystem functioning are projected to become more pronounced over the coming decades.

Speakers at the briefing said that biodiversity is important to protect not only because species have their own purposes in the ecological web but also because they provide substantial benefits to people.

“If anyone thinks that biodiversity is not crucial to human existence, think again,” Udall said, noting that at least 40% of the world’s economy is based on biological resources and that the diversity of life provides humanity with food, shelter, medicine, and economic development, among other benefits.

Establishing a wildlife corridors system “is something that shouldn’t be about party. It should be about just saving our planet.”“Living ecosystems support us. America’s wildlife is in great jeopardy,” he said. “We must act now.”

No Second Chance After a Species Goes Extinct

Establishing a wildlife corridors system “is something that shouldn’t be about party. It should be about just saving our planet,” said Rep. Don Beyer (D-Va.), who introduced companion legislation in the House. “This is an absolutely critical time considering the UN report on accelerated species extinction rate.”

Beyer, who is cochair of the New Democrat Coalition’s Climate Change Task Force, said that he and Republican cosponsor Rep. Vern Buchanan (R-Fla.) will be working with the House leadership to get the bill on the House calendar. He also related that Rep. Raúl Grijalva (D-Ariz.), chair of the House Committee on Natural Resources, has indicated that he wants to push this legislation in that committee.

Beyer optimistically stated that he expects “scores of Republican votes when it gets to the House floor.” No Republicans had signed onto earlier versions of the bill introduced during previous sessions of Congress.

“We don’t get a second chance once a species becomes extinct.”Buchanan, who so far is the sole Republican cosponsoring the new legislation, said in a press release issued by conservation groups supporting the bill that protecting wildlife and promoting biodiversity “are of critical importance” in light of the UN report. “We don’t get a second chance once a species becomes extinct,” he said.

Raising Concern About Biodiversity

At the briefing, Ron Sutherland, chief scientist with the Wildlands Network, a Seattle-based conservation group that supports the legislation, speculated about why concern about biodiversity hasn’t yet caught on as a hotter issue in the same way that climate change has.

“One perspective might be that there was a huge push to protect biodiversity for its own sake in the ‘90s, and I think that that push eventually earned the sort of inevitable fatigue on all the champion for it. Climate change became kind of the new cause, and a lot of young folks have joined into that movement,” Sutherland said. “I think we’re remembering the fact that that we depend on the Earth’s biodiversity. Now, pollinators have become such a huge cause lately. So I think that the pendulum is shifting or at least is broadening again, so that there’s room again to talk about the other environmental challenges that we’re facing. It’s not just climate change. It’s land use change that is causing a huge threat to biodiversity.”

Sutherland noted, “That’s where this bill really could help out here in the United States: by helping repair the landscape to help species to survive and also to respond to climate change.”

Beyer said that his sense as to why the threat to biodiversity hasn’t yet caught on like climate change is because “climate change is so visible” as an immediate threat. “We can have these incredibly sad images of polar bears floating on small little pieces of ice or the incredible forest fires in the West. Just the extreme weather impact, that there are so many ways that climate change is becoming real in our lives right now,” he said. “Biodiversity is a little harder to see. We have to think more from a scientific perspective and the long term because it doesn’t seem to change my life today at all.”

A Political Problem, Not a Scientific Problem

“We already know how to address this crisis. This isn’t a scientific problem. It’s a political one.”The legislation “is a call to us all to step up and to realize that we have not only a moral and ethical responsibility to stewarding the planet. But it’s our time to recognize that we need to strengthen our bedrock environmental laws, not weaken them. We need to hold ourselves accountable to the future,” Jamie Rappaport Clark, CEO and president of Defenders of Wildlife, a conservation group headquartered in Washington, D.C., said at the briefing.

“Human intervention caused this mass extinction crisis. Now human intervention through legislation must reverse the tide,” Udall added. “We already know how to address this crisis. This isn’t a scientific problem. It’s a political one. The science is clear: Corridors help protect our most iconic species.”

—Randy Showstack (@RandyShowstack), Staff Writer

How Will the Jet Stream Respond to Future Warming?

Mon, 05/20/2019 - 11:33

Midlatitude jet streams, narrow bands of strong upper atmospheric winds, steer high- and low-pressure weather systems and help maintain our planet’s habitable climate. They are closely related to the preferred track of midlatitude low-pressure storm systems known as storm tracks.

The position and intensity of jet streams typically vary in response to processes that affect surface temperature gradients between the equator and the poles. Although many comprehensive climate models predict that Earth’s jet streams will shift poleward as the planet warms, the projected magnitudes of these shifts appear to vary widely depending upon the planet’s response to changes in radiative energy.

Now Tan et al. have developed a series of simulations to test how different approaches to modeling radiation can affect the response of jet streams to global warming. The results indicate that when using a gray radiation scheme, which has been used in many simplified modeling studies, the midlatitude jet stream responds by shifting toward the equator rather than the pole.

The authors conclude that despite the prevalence of the gray radiation scheme, this approach does not adequately capture the circulation response to global warming. Instead, the researchers showed that using a simple, four-band longwave radiation scheme that incorporates the effects of water vapor more effectively replicates circulation responses in full general circulation models.

The results suggest the authors’ model captures the fundamental processes that influence the response of midlatitude circulation to increasing temperatures and demonstrate that this approach can boost our understanding of how jet streams and storm tracks will respond to future warming. (Journal of Advances in Modeling Earth Systems (JAMES), https://doi.org/10.1029/2018MS001492, 2019)

—Terri Cook, Freelance Writer

Podcast: A Tale of Two Journeys

Mon, 05/20/2019 - 11:32

In the early years of the 20th century, several groups of explorers attempted to be the first to reach the South Pole, as Antarctica was one of the last unexplored places on Earth. A team of Norwegian explorers led by Roald Amundsen was the first to reach the pole, on 14 December 1911. A competing British party led by Capt. Robert Falcon Scott reached the pole roughly a month later. Amundsen’s team returned safely home, but Scott’s team perished on the ice in March 1912.

New research indicates that warm weather and good conditions were a boon to the South Pole expedition led by Roald Amundsen, above. Credit: Roald Amundsen

Recent research has suggested that Antarctica experienced unusually warm weather during the Southern Hemisphere’s summer of 1911–1912, and this weather may have influenced the outcome of Amundsen’s and Scott’s race to the South Pole. In 2017, Ryan Fogt, an atmospheric scientist at Ohio University, used data from numerous weather stations in the Southern Hemisphere to reconstruct atmospheric pressures over Antarctica from 1905 to the present.

Fogt found that Amundsen and Scott experienced exceptionally high pressures that were often associated with unseasonably warm summer temperatures on their expedition routes. The warm temperatures were a boon to Amundsen’s crew but hindered Scott’s progress in two instances, and those setbacks may have contributed to the deaths of the Scott party in March 1912.

In this Centennial episode of Third Pod from the Sun, Ryan Fogt recounts the journeys of Scott and Amundsen during this fateful summer and discusses how the extraordinary weather affected the two polar parties in vastly different ways.

—Lauren Lipuma (@Tenacious_She), Contributing Writer

Polar Vortex Deformations Change Tidal Weather in the Mesosphere

Mon, 05/20/2019 - 11:30

A variety of weather processes in the troposphere, solar radiation absorption in stratospheric ozone and nonlinear wave-mean flow interactions excite a longitude-dependent spectrum of atmospheric tides – global scale wave motions – with periods defined by Earth’s rotation rate. Growing exponentially in magnitude when propagating upward, tides are a key ingredient in coupling the lower with the upper atmosphere and cause regular semidiurnal wind oscillations on the order of +-50 meters per second in the upper mesosphere.

During Stratospheric Sudden Warmings, a deformation or split of the polar vortex, the semidiurnal tide in the upper mesosphere changes by as much as its average amplitude. Understanding the reasons for this dramatic impact requires to resolve the global wavenumber spectrum of the semidiurnal tidal oscillations on a day-to-day basis. This has always been a challenge because satellites do not have the necessary time resolution and single ground-based observations lack the spatial information.

Hibbins et al. [2019] present a new approach using meteor wind data from the Super Dual Auroral Radar Network (SuperDARN) in the northern hemisphere to resolve the semidiurnal wave spectrum at 95-kilometer altitude around 60oN latitude with high time resolution. By separating migrating (Sun-synchronous) and nonmigrating (non Sun-synchronous) tides, the authors are able to conduct a statistical analysis of short-term tidal variability in response to Stratospheric Sudden Warming using 20 years of available data.

They demonstrate that the migrating semidiurnal tide is absent during the period immediately following the Stratospheric Sudden Warming onset but anomalously large during the recovery phase due to propagating conditions and stratospheric ozone driving. Nonmigrating tides play a lesser role. This study may also help to better understand how stratospheric sudden warmings impact the ionosphere through dynamo processes because of the global nature of the tides and to guide further model developments.

Citation: Hibbins, R. E., Espy, P. J., Orsolini, Y. J., Limpasuvan, V., & Barnes, R. J. [2019]. SuperDARN observations of semidiurnal tidal variability in the MLT and the response to sudden stratospheric warming events. Journal of Geophysical Research: Atmospheres, 124. https://doi.org/10.1029/2018JD030157

—Jens Oberheide, Associate Editor, JGR: Atmospheres

Did a Volcanic Eruption in 1783 Change the Climate in Europe?

Fri, 05/17/2019 - 12:08

In June of 1783, the Laki volcano in Iceland started an 8-month-long eruption sequence, including 10 explosive eruptions and continuous emission into the lower atmosphere.

The event had far-reaching consequences: Air pollution and acid rain decimated crops in Iceland, contributing to a famine responsible for the deaths of 60% of the island’s livestock and 20% of the human population within a year. In Europe, a layer of hazy “dry fog” settled over the continental mainland, leading to respiratory problems, headaches, and other health problems for millions.

Although these consequences of the eruption are well documented, scientists have been conflicted as to whether the global climate anomalies in the following year were caused by the eruption or merely the result of normal year-to-year variability.

Following a large volcanic eruption, scientists typically expect to see net cooling effects due to the release of sulfur dioxide, which travels to the stratosphere and forms sulfuric acid aerosols. These aerosols reflect incoming light from the Sun, effectively shading the planet. But eruptions can also exert a warming influence on the climate as they release large amounts of greenhouse gases.

Following the Laki eruption, the summer of 1783 was anomalously warm in Europe, leading some experts to question whether a magnified greenhouse effect was responsible for the heat wave. Similarly, the winter of 1783–1784 was particularly cold in Europe, and scientists have wondered whether the negative radiative forcing from sulfuric acid aerosols could be to blame.

In a new study, Zambri et al. used the Community Earth System Model from the National Center for Atmospheric Research to simulate the Laki eruption in conjunction with other sources of natural climate variability from the time period.

Their analysis indicated that the abnormally warm European summer of 1783 was, in fact, not attributable to the Laki eruption. Instead, the researchers found that the high temperatures could be explained by atmospheric blocking, in which a high-pressure system to the north of the continent impeded the southerly flow of cold polar air, keeping Europe warmer than average. In fact, the authors suggest that without the negative radiative forcing from the eruption, Europe may have been even hotter still.

As for the cold winter that followed, the researchers concluded that the Laki eruption was not the cause of the negative North Atlantic Oscillation (NAO) and thus not responsible for the anomaly—at least not for the months of December, January, and February. For the later winter and into the spring, the researchers report that they did find a “robust” negative NAO response as well as an El Niño–Southern Oscillation response to the Laki eruption, suggesting, again, that the primary climate impact from the event was cooling.

The results, the scientists say, show the limitations in forecasting how future eruptions may shape the planet’s climate in the short term and help to paint a clearer picture of how various climate forces interact. (Journal of Geophysical Research: Atmospheres, https://doi.org/10.1029/2018JD029554, 2019)

—David Shultz, Freelance Writer

When Water Met Rock

Fri, 05/17/2019 - 12:07

It’s hard to imagine Earth without water. After all, water helps puts the “blue” in astronomer Carl Sagan’s famous description of our planet as a “pale blue dot.”

The first known interaction between water on Earth’s surface and rock happened about 3.5 billion years ago.But billions of years ago, there was no water on Earth’s surface, and exactly when our pale dot got its liquid “blue” is a fuzzy tale, largely because most of the rocks that existed back then have been erased by different geologic processes.

However, in the northeastern region of Labrador, where polar bears patrol the landscape, some of Earth’s oldest rocks exist. And these rocks, according to new research, bear chemical evidence revealing that the first known interaction between water on Earth’s surface and rock happened about 3.5 billion years ago. The results were published in April in Geology.

Deciphering the Saglek

The discovery started in 2012, when a team of scientists ventured into the Arctic for a 5-week expedition. They went there because, according to Adrien Vezinet, a geochemist at the University of Alberta in Edmonton who led the team that made the new find, there has been very little research into these Arctic rocks—part of the Archean-aged Saglek Block—over the past 3 decades or so.

Vezinet thought that there might be more to learn.

He was right.

Vezinet and his team measured the concentration of oxygen isotopes in zircon crystals in the rocks, and they found an unusually high concentration of oxygen isotopes coinciding with parts of the rock that are about 3.5 billion years old.

“The observed deviation in our zircon is almost twice higher than the ‘normal’ deviation measured in early Archean zircon,” Vezinet said. “It’s pretty much the only value that’s that high during the Archean.”

The only way that the rocks could acquire such an isotope value is if they were in contact with water on the planet’s surface, he explained.

“It’s the oldest evidence of this elevated oxygen,” said Simon Wilde, a geologist at Curtin University in Australia who was not involved in the new research.

Domain of the Zircons

Zircon is the superman of minerals: It’s resilient and can last an extremely long time in the planet’s rock record. Nevertheless, anything that persists for billions of years of the planet’s history is likely to face forces that can alter its original chemical composition. So the chief challenge facing Vezinet and his team was being able to say for sure that the crystals acquired their elevated oxygen isotope signature 3.5 billion years ago and not at some later time.

To sort this out, the team took a close-up look at crystalline domains within individual zircon crystals, something that was not really possible with technology that existed a few decades ago. Vezinet explained that if the domains had changed their composition since they formed, then the crystal structure, as well as the domain’s chemical makeup, ought to have altered as well. This domain-by-domain approach allowed the team to pinpoint which areas of each zircon crystal had oxygen isotope values that formed at the same time that the crystal formed and thus say for certain that the isotope value is a result of interactions with 3.5-billion-year-old surface waters.

One unexplored domain, though, is that it is not clear yet just how much surface water there was back then. It could have been a small inland sea, or it could have been an entire ocean. “I’d imagine that it’s widespread,” said Wilde.

But to be sure, tests of the isotopic content of similar rocks elsewhere on the planet need to be done to see just how blue our pale dot truly was.

—Lucas Joel (lucasvjoel@gmail.com), Freelance Journalist

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