EOS

With a yearslong monitoring effort, scientists have tracked the buildup and release of gas pressure beneath Italy’s Mount Etna leading up to its Christmas Eve eruption in 2018. According to new research, some types of gas built up continuously within the volcanic system for a year prior to the eruption, whereas pressure from other gases ebbed and flowed.

“We are able to recognize a process occurring inside the volcano which causes eruptions and to state, ‘Ok, it is starting, it is growing, it is at critical levels!’ At Etna it lasts months to years.”“We are now able to quantify the pressure accumulation in the magmatic reservoir while [the buildup is] developing,” said Antonio Paonita, a geochemist at Istituto Nazionale di Geofisica e Vulcanologia Sezione di Palermo in Italy and lead author of the study. “We are able to recognize a process occurring inside the volcano which causes eruptions and to state, ‘Ok, it is starting, it is growing, it is at critical levels!’ At Etna it lasts months to years.”

When combined with advanced theories for how magma recharges within Etna’s magmatic system, one of the most active in the world, this new insight into how pressure builds up will help scientists better understand and predict its eruptions.

Gases Track Magma Movement

What goes on inside a volcano’s magma reservoirs controls the volcano’s behavior at the surface. Magma and volatile gases flow into a chamber from deep within Earth and sometimes find nonexplosive ways out through conduits, sills, and dikes (as for magma) or degassing vents. Volcanoes tend to erupt when a magma chamber becomes overpressurized, which can happen when more magma and gas enter the chamber than leave it.

Pressure buildup in some volcanic systems can stretch for tens of years leading up to an eruption. Other systems, however, such as Kīlauea and the Alaskan volcanoes in the United States, the Aleutians that stretch between Alaska and Russia, Nyamuragira in the Democratic Republic of the Congo, and Mount Etna, “normally exhibit quicker dynamics and frequent eruptive activity” spanning months or years, Paonita explained. As theories of magma recharge of a reservoir become more sophisticated, surface and remote monitoring of volcanic degassing can help researchers estimate the overall state of pressurization within a volcanic system and anticipate its eruption potential.

“Each gas is then indicative of a range of depth where degassing is occurring and magma dynamics is acting.”Mount Etna is an excellent testing ground for such theories for a number of reasons: It erupts regularly, scientists have modeled its magma recharge system, and an extensive network of instruments continuously monitors the volcano’s degassing. With a combination of remote sensing and on-site sampling, the researchers analyzed the degassing patterns of carbon dioxide (CO2), sulfur dioxide (SO2), hydrochloric acid, and helium isotopes starting roughly a year prior to the 24 December 2018 eruption until about a year after.

“Different gases are released from magma at different depths along the [magma] ascent path,” Paonita explained. “Roughly speaking, each gas is then indicative of a range of depth where degassing is occurring and magma dynamics is acting.”

The team found that the helium isotope ratio emitted by Etna steadily rose from the first half of 2017 all the way up to the eruption, after which it dropped significantly. CO2 flux, which had been low and steady, increased in June 2018 and then fell and rose again cyclically until the eruption. SO2 flux, however, rose only in the weeks immediately preceding the eruption (from about 5,000 metric tons per day to about 12,000 metric tons per day) and fell back to typical levels after the eruption.

“Our study highlighted an imbalance between the amount of gas normally rising with the magma from the mantle beneath a volcano and that emitted in pre- and inter-eruptive phases,” Paonita said in a statement. “Recognizing and quantifying this ‘imbalance’ and its evolution almost in real time provides a new interpretative key for evaluating the ‘state of activity’ of the volcano.” The team published these results in Science Advances on 1 September.

Bespoke Volcanic Systems

Mount Etna looms over Sicily’s second-largest city, Catania; has erupted 50 times so far in 2021; and has grown 31 meters taller in the past 6 months. Can these results help volcanologists predict eruptions? Perhaps for Mount Etna, but probably not for other volcanoes.

Degassing data’s predictive power ultimately depends on how well we understand a particular magmatic system.Long-term surveillance of volcano degassing could anticipate an eruption, but its predictive power ultimately depends on how well we understand a particular magmatic system, Paonita said. A rise in the concentrations of CO2 and noble gases, for example, generally points to magma movement many kilometers below the surface, whereas a sharp rise in SO2 implies magma moving closer to the surface. “In theory, we can interpret degassing data with no basic knowledge of [a] system,” he said.

In reality, however, volcano behavior depends on the internal structure of a magmatic system, and although Mount Etna is an archetype of open-conduit volcanoes, each one is unique. “Our experience on that volcanic system—for example, long records of signals to be compared to its eruptive behavior—and our geological knowledge are precious and irreplaceable information for interpreting monitored signals in the right context.”

—Kimberly M. S. Cartier (@AstroKimCartier), Staff Writer

Forest recovery is an important tool to fight climate change. Recent research, however, shows that recovery in the Amazon has a long way to go to become truly effective.

Secondary forests—wooded areas intentionally replanted after a timber harvest has destroyed a primary or old-growth forest—are one way communities and businesses have responded to deforestation. The trees and shrubs in secondary forests do not entirely replace the trees lost in primary forests, but the plant biomass acts as a carbon sink that offsets carbon emissions associated with the initial deforestation.

According to a new study, however, secondary forests have offset less than 10% of deforestation-caused carbon emissions in the Amazon—even as they take up almost 30% of the total deforested area in the region. With territory accounting for about 60% of the biome, Brazil leads the trend: The country had the lowest carbon offset rate (9%) and the smallest forest area recovery (24.8%).

On the opposite end of the spectrum, Ecuador had the largest forest area recovery (56.9%), whereas Guyana had the highest carbon offset rate (23.8%). These countries, however, represent a small fraction of the Amazon, as they account for just 1.5% and 3% of the biome, respectively.

“Now that there’s data available to all individual countries in the Amazon, they don’t need to make estimates based [solely] on Brazilian findings.”The study, published in Environmental Research Letters, is the first to analyze forest loss and recovery at both national and subnational levels for the whole Amazon region. The researchers analyzed data from all nine Amazonian countries (Bolivia, Brazil, Colombia, Ecuador, France (through the department of French Guiana), Guyana, Peru, Suriname, and Venezuela) and the nine Brazilian states that make up the biome (Acre, Amapá, Amazonas, Maranhão, Mato Grosso, Pará, Rondônia, Roraima, and Tocantins).

The analysis builds on land cover data from the Brazilian Annual Land Use and Land Cover Mapping Project (MapBiomas) between 1985 and 2017, as well as estimates of aboveground biomass and carbon sequestration rates for the period.

The team used MapBiomas remote sensing maps for each year, looking pixel by pixel for the areas that were covered and not covered by vegetation to track changes in land use. “We overlapped the maps looking for where there was vegetation in a given year but not in the next (meaning the area was deforested) and where the opposite happened, meaning there was forest recovery,” explained coauthor Erika Berenguer, a researcher at the University of Oxford and Lancaster University in the United Kingdom.

“The resolution of each pixel is 30 square meters, so MapBiomas gave us quite fine-grained material to work on,” said lead author and Lancaster University researcher Charlotte Smith. Besides fine resolution, the study gives a good picture of what is happening in the whole biome, she said. “Now that there’s data available to all individual countries in the Amazon, they don’t need to make estimates based [solely] on Brazilian findings.”

International and Interstate Disparities

Brazilian states account for more landmass in the region and for a larger share of deforestation. Researchers found that by 2017, the deforested area in Pará alone—more than 260,000 square kilometers, an area larger than the U.S. state of Oregon—was more than twice the cleared area of all other Amazonian countries combined. Deforestation-related carbon emissions from Mato Grosso, Pará, and Rondônia surpass those of any other individual Amazonian country.

Contrasts are stark also among Brazilian states themselves. Whereas Tocantins lost more than 80% of its primary forest and less than 20% of this area was recovered with secondary forest, Amapá had only 4% of its total forest area razed and recovered almost 70% of it with secondary forest. Amapá also managed to offset more than a quarter of its deforestation emissions (26.9%), whereas Tocantins offset only a little more than a tenth (13%).

It is worth noting that Amapá has more than 4 times the forest area of Tocantins, and more than 70% of its area is protected as conservation units or Indigenous lands. The state has the lowest deforestation rates in the Brazilian Amazon according to the Amazon Deforestation Monitoring Project, part of Brazil’s National Institute for Space Research.

Older Forests Have Greater Carbon Sequestration

University of Connecticut professor Robin Chazdon, who did not take part in the study, said it confirms trends observed in previous research about carbon recovery in reforested regions. “It also shows the need for deeper analysis of the economic, social, and political factors that are part of these trends,” she said.

Chazdon explained that the amount of remaining forest in a place is a predictor for unassisted vegetation regrowth. “Sometimes there’s a time lag between forest clearance and land use,” she said, hinting that older secondary forests may yield higher carbon sequestration rates.

The numbers in the study back Chazdon’s observations: Almost 80% of all secondary forest vegetation analyzed was less than 20 years old, with an average age of 8 years. Guyana and Suriname had some of the oldest secondary forests studied, and these countries had the highest carbon recovery rates of the whole biome.

“We’re always told the story of how we are failing the Amazon forest. But places like Ecuador and Amapá show that the Amazon is not all about failure.”“This means that trees must be given time to grow, so their carbon absorption can make some difference,” Berenguer said. She stressed that secondary forests are not absorbing as much carbon as they could for two primary reasons: Deforestation emissions in the Amazon are still overwhelmingly high, and at the same time, secondary forests are razed at a young age across most of the biome. “It is counterproductive to plant a hectare and tear another 10 down,” she added.

Despite the scenario, the researchers see some space for hope. “We’re always told the story of how we are failing the Amazon forest. But places like Ecuador and Amapá show that the Amazon is not all about failure. They’re two cases that need to be looked at in detail so we can learn something that can be useful to the whole biome,” Berenguer said.

“Latin America has the highest forest recovery capacity in the world, with the Amazon forest having the highest potential across the region,” said Chazdon. “Brazil is the single country with the highest forest recovery capacity in the world—but social, economic, and political factors impede regrowth.”

—Meghie Rodrigues (@meghier), Science Writer

Lara Mani was tired of hearing about the Yellowstone supervolcano. Every so often, another news story would appear, proclaiming that the Yellowstone caldera system could erupt with such ferocity that the impacts could cascade into a global catastrophe. “Yes, there’s plausibility in that,” said Mani, a research associate at the University of Cambridge’s Centre for the Study of Existential Risk, “but that’s not the only mechanism. There’s another way that can happen.”

Smaller eruptions, depending on where they occur, could also have catastrophic impacts, Mani thought. Historically, researchers have focused largely on the physical risk—the magnitude of potential eruptions. That’s at least in part because the vulnerability side—the transport routes, communication networks, and other infrastructure that if disrupted would affect societies around the globe—has become a problem only more recently.

“Most of the vulnerability is a relatively new (late 20th–21st century) product of how we humans have changed our technologies, economies, and flow of services,” said Chris Newhall of the Earth Observatory of Singapore. But we’ve already seen how small eruptions can lead to major disruptions. Consider the 2010 eruption of Eyjafjallajökull in Iceland, which grounded more than 100,000 flights and cost the global economy upward of $5 billion.

“That should never have reached the global platform that it did; it was such a small eruption,” Mani said. “Why? What’s the mechanism behind that? What does this mean? That’s where it started.” In a new study in Nature Communications, Mani and her colleagues began brainstorming identifying areas where smaller eruptions could combine with human-made vulnerabilities with catastrophic results. The new knowledge could lead to risk assessments and changes to preparedness.

Pinch Points

Mani and her colleagues began by looking at choke points along shipping routes—a focus that was highlighted this year when a container ship ran aground in the Suez Canal, bringing a major global trade route to a halt. They also looked at air traffic routes and other critical infrastructure like underwater cables and manufacturing hubs. The team identified seven “pinch points,” where active volcanoes overlapped with these vulnerabilities. Four of these points were clustered together in a highly populated geographic corridor from Southeast Asia through the South China Sea. “It makes sense that where you have people, you have systems to sustain those societies,” Mani said.

Pinch points mark the clustering of critical systems and infrastructures with regions of lower-magnitude volcanic activity. These pinch points are presented with the likely associated volcanic hazard and the potentially affected systems. Credit: Mani et al., 2021, https://doi.org/10.1038/s41467-021-25021-8

A small eruption at Mount Paektu on the China–North Korea border, for example, could disrupt air routes between Seoul and Osaka or Tokyo—some of the busiest routes in the world. In the Luzon Strait, a landslide or tsunami caused by an eruption along the Luzon Volcanic Arc could sever critical submarine cables connecting countries from China and Taiwan to the Philippines. Some 40% of global trade passes through the Strait of Malacca (between Malaysia and Indonesia); an eruption of any number of volcanoes along the Indonesian archipelago could shut down air and maritime traffic. The cascading impacts of these events are unpredictable and difficult to calculate: The 6-day blockage of the Suez Canal, for example, cost the Egyptian government as much as $90 million in lost toll revenue. Global trade revenue sank by as much as $10 billion.

“We’ve prioritized efficiency over resilience. If something goes wrong, there isn’t an alternative.”“We’ve prioritized efficiency over resilience,” Mani said. “If something goes wrong, there isn’t an alternative.”

Taiwan is home to the Taiwan Semiconductor Manufacturing Company (TSMC), responsible for manufacturing 90% of the world’s advanced microchips and nodes. An eruption in the Tatun Volcano Group could close the port of Taipei, isolating TSMC from the rest of the world. “Anything that happens to TSMC…sends a shock wave [through society],” said Mani. “Everybody knows that it’s a critical vulnerability, but no one has ever thought about what it’s vulnerable to.”

The team also identified pinch points in the Mediterranean, the North Atlantic, and the Pacific Northwest, where the eruption of one of the Cascades volcanoes could melt glaciers or ice caps, triggering a debris flow that could potentially reach all the way to Seattle.

Mani hopes that pointing out these vulnerabilities in global systems will ultimately help to build resilience. “My hope is that it will raise some questions to the volcanology community, the volcanic risk community, to start having these discussions about what this risk really looks like,” she said, “so that disaster managers, international organizations, and governments can start thinking about mitigation and prevention.”

—Kate Wheeling (@KateWheeling), Science Writer

Utkin and Afanasyev [2021] present a semi-empirical coupled model of compaction-driven fluid flow and numerically solve it to simulate non-reactive transport of magmatic fluid across both the ductile and brittle zones. Their approach accounts for the thermal softening of the rocks and the plastic deformation of their solid matrix through decompaction weakening while guaranteeing material balance for the fluid and solid phases everywhere in the model.

A single numerical simulation concurrently models the following physical mechanisms: Porosity waves form vertical high-porosity channels which transport magmatic fluid across the ductile zone, culminating in high-porosity lenses right beneath the brittle to ductile transition. In this transition zone, magmatic fluid transport occurs through the roof of those high-porosity lenses, resulting in a plume of hydrothermal convection in the brittle zone sitting atop each lens and following a narrowing path toward the surface. The pattern of hydrothermal convection in the brittle zone is completed by meteoric water forming other plumes between the lenses as well as mixing with the magmatic fluid in a process that transfers heat to the surface.

Studying the physical mechanisms of fluid transport in the upper crust is particularly relevant to understand the formations of exploitable geothermal resources and of ore deposits.

Citation: Utkin, I., & Afanasyev, A. [2021]. Decompaction weakening as a mechanism of fluid focusing in hydrothermal systems. Journal of Geophysical Research: Solid Earth, 126, e2021JB022397. https://doi.org/10.1029/2021JB022397

—Beatriz Quintal, Associate Editor, JGR: Solid Earth

The onset of geodesy and seismic monitoring has produced a richer picture of slip in subduction zones that includes not only megathrust earthquakes, but also variations of slow slip events of different sizes and durations. Slow slip events can rival large earthquakes in terms of cumulative moment. Many of these slow slip events occur in the transition zone between the shallow brittle and deeper ductile regimes. Behr et al. [2021] model this transition as a narrow zone of strong clasts embedded within a ductile matrix, as has been observed in outcrops of exhumed subduction zones (as shown in the figure above). The authors simulate slip while systematically varying strength contrasts and relative proportions of weak and strong material. They find three slip modes that result from these variations: aseismic slip with no earthquakes, slow-slip, and regular earthquakes, which mirror observations from subduction zones as well as what is observed geologically in exhumed subduction zones.

Citation: Behr, W., Gerya, T., Cannizzari, C. & Blass, R. [2021]. Transient Slow Slip Characteristics of Frictional-Viscous Subduction Megathrust Shear Zones. AGU Advances, 2, e2021AV000416. https://doi.org/10.1029/2021AV000416

—Tom Parsons, Editor, AGU Advances

When solar wind slams into Earth’s magnetic field, the impacts ripple down through the planet’s ionosphere, the outer shell of the atmosphere full of charged particles. A global array of high-frequency radars known as the Super Dual Auroral Radar Network (SuperDARN) tracks ionospheric plasma circulation from the ground, giving researchers insights into the interactions between solar wind, the magnetosphere, and the ionosphere. Though widely used in space physics research, the network is not comprehensive—each ground-based radar can measure plasma velocity only in its line-of-sight direction, for example. As a result, there are major spatial and temporal gaps in the SuperDARN archive.

Historically, researchers have filled in these gaps with models that make assumptions based either on climatological averages of the SuperDARN data or on solar wind measurements. In a new study, Shore et al. present a new method using a data-interpolating empirical orthogonal function technique, which allows researchers to detect patterns within existing SuperDARN plasma velocity data and then use this information to fill in gaps. The team used observations collected by the network’s Northern Hemisphere stations in February 2001 and filled in missing information at any given time using the velocity patterns deduced from data collected at a given location throughout the month and from other network locations at the same time.

The SuperDARN data set is critical for understanding space weather and its potential impacts on the technologies underlying things like radio communications and satellite services, and this new technique can provide researchers with the most accurate estimates yet of ionospheric electrodynamic variability. (Journal of Geophysical Research: Space Physics, https://doi.org/10.1029/2021JA029272, 2021)

—Kate Wheeling, Science Writer

The northern Indian Ocean consists of two seas: the Bay of Bengal to the east and the Arabian Sea to the west. Historically, tropical cyclone activity in the Bay of Bengal is generally higher than that in the Arabian Sea. But new research showed a shift in this trend.

Researchers found that between 1982 and 2019, there was a significant increase in the frequency, duration, and intensity of cyclonic storms over the Arabian Sea. Specifically, they noted a 52% increase in the frequency of cyclonic storms, an 80% increase in their duration, and an increase in intensity of about 20% in the premonsoon period and 40% postmonsoon. In addition, researchers documented a tripling of the accumulated cyclone energy in the Arabian Sea. The study was published in Climate Dynamics.

“We studied data covering about 38 years by dividing [the period] into two epochs of 19 years each. In the Arabian Sea, we found that the intensity, frequency, and duration [are] increasing, but in the Bay of Bengal there has been no significant change,” said Medha Deshpande, lead author of the study and a scientist at the Indian Institute of Tropical Meteorology (IITM).

Reasons for the increase in cyclonic activity in the Arabian Sea include increases in sea surface temperature and tropical cyclone heat potential. Both measures are reliable indicators of climate change.

Warming Seas and Cyclonic Activity

The recent Sixth Assessment Report by the Intergovernmental Panel on Climate Change (IPCC) showed that the Indian Ocean is experiencing the world’s fastest rate of ocean surface warming.

Roxy Mathew Koll is a climate scientist at IITM, a coauthor of the new study, and a reviewer of recent IPCC reports. He explained that in the Indian Ocean, the Arabian Sea showed temperature changes reaching up to 1.2°C–1.4℃ over the past 20 years. “Compared to global ocean surface warming of 0.8°C–0.9℃, this is quite large,” he said.

A warmer Arabian Sea means more heat for cyclones to draw energy from. It also means more moisture for cyclones to feed on. So warming seas allow for the genesis and maintenance of severe cyclonic storms.

Disaster Preparedness, Mangroves, and Free-Flowing Rivers

On the basis of past cyclone tracks, Koll listed the Indian states and territories that may be most affected by increased activity: Lakshadweep, Gujarat, Maharashtra, Karnataka, and Kerala. Lakshadweep, composed entirely of tiny islands hundreds of kilometers off the coast of Kerala, is particularly vulnerable. The archipelago’s very survival has come under serious questioning given the threats posed by cyclonic activity, sea level rise, and coastal erosion.

Experts said one manner in which states could prepare for the onslaught by cyclone is by conserving mangrove ecosystems. Such techniques also have benefits for climate adaptation and disaster risk reduction. Detailing the benefits mangroves offer, Koll said they reduce the impact of winds and flooding during cyclones and can regrow following cyclonic damage.

In addition to mangrove conservation, “we need to allow rivers to bring fresh water, sediments, and nutrients to estuaries and deltas,” said Jagdish Krishnaswamy, a senior fellow at the Suri Sehgal Centre for Biodiversity and Conservation, Ashoka Trust for Research in Ecology and the Environment. Krishnaswamy, also a coordinating lead author of the IPCC report, was not involved in the new study.

Low-lying coastal areas depend on such sediment flow from rivers to offset soil erosion into the sea. India’s west coast is a very narrow strip of land abutted by the mountains of the Western Ghats, leaving its population “highly vulnerable to disasters because of sea level rise, reduced sediment flow because of dams upstream, and increasing cyclonic activities,” Krishnaswamy noted.

Overall, Krishnaswamy said, the increased vulnerability of the west coast to cyclonic activity demands that developmental plans (including the country’s Coastal Regulation Zone notification system) take the effects of climate change into consideration. In particular, he stressed that natural climate infrastructure like mangroves be given more attention to enhance resilience to flooding and storms.

—Rishika Pardikar (@rishpardikar), Science Writer

Problems from coastal erosion to climate dynamics require a better handle on ocean wave phenomena. Satellites image the surface expression of ocean waves. However, there are coverage limits, and solid earth recordings can provide complementary constraints for ocean and surface dynamics. Here, Shaddox et al. [2021] expand prior environmental seismology analysis and focus on solitary ocean waves passing by a near-ideal test setting, an atoll in the South China Sea which is known to experience large amplitude wave activity. By combing data from a permanent borehole seismometer, temporary stations, satellites and ocean sensors, the authors find tantalizing evidence for the detection of the subtle tilting that might be expected from the ocean-land interactions around the island. Similar signals had been seen on ocean bottom seismometers, but if the land-based detection were to become routine, perhaps with improved seismic sensors, more complete records of ocean dynamics would become available.

Citation: Shaddox, H., Brodsky, E., Davis, K. & Ramp, S. [2021]. Seismic Detection of Oceanic Internal Gravity Waves from Subaerial Seismometers. AGU Advances, 2, e2021AV000475. https://doi.org/10.1029/2021AV000475

—Thorsten W. Becker, Editor, AGU Advances

There’s a stubborn, heat-absorbing particle that floats along in Earth’s atmosphere: It initially doesn’t like water, it absorbs light, and it takes its time moving on. Black carbon in the atmosphere tends to linger until it finally absorbs enough water to fall from the sky. In the meantime, black carbon absorbs the Sun’s energy and heats up surrounding air, creating a radiative effect.

Fresh, young black carbon tends to be resistant to water. Over time, the particles age and become more hygroscopic, or able to absorb water from the air. But when does black carbon start absorbing water, act as cloud nuclei, and remove itself from the atmosphere?

Researchers previously investigated the hygroscopic conditions of black carbon in the lab, with limited conditions on chemical sources and water vapor conditions. In all of these studies, the cloud nucleation values of black carbon were indirect measurements.

In a new study by Hu et al., researchers concurrently measured the concentration of cloud condensation nuclei and black carbon particles. The sampling site was near heavily trafficked roads and industrial centers in Wuhan, China, an urban megacity in the central part of the country.

They first corrected for the size of particles, then measured cloud condensation nuclei and individual black carbon particles in certain levels of water supersaturation in the atmosphere. The team found that the activation diameter, or the size of the black carbon particle where half of the particles will nucleate and precipitate out, was 144 ± 21 nanometers at 0.2% supersaturation. How these black carbon–containing particles could act as cloud nuclei is determined by their size combined with their coatings, the authors say, and in general, the less saturated the air was, the bigger the particles had to be to nucleate.

In addition, the team found that a particle itself may influence the size of nucleation. For instance, the amount of organic content in a particle or any coating on the black carbon can change the hygroscopicity and therefore the activation.

The research team noted that their work can help improve estimates of the longevity of suspended black carbon particles in the atmosphere and therefore the radiative impacts those particles can have.

(Journal of Geophysical Research: Atmospheres, https://doi.org/10.1029/2021JD034649, 2021)

—Sarah Derouin, Science Writer

Dioxins—the category of chemicals that includes Agent Orange—have been banned in the United States since 1979. But that doesn’t mean they’re gone. Like in the plot of countless scary movies, dioxins and other banned chemicals are just buried beneath the surface waiting to be unearthed.

A new perspective paper in Journal of Hazardous Materials calls attention to an understudied area: the remobilization of pollutants buried in riverbeds. Chemicals have a knack for binding to sediments, meaning chemical spills in rivers frequently seep into sediments instead of flowing downstream. Future layers of silt bury the pollutants and hide the problem.

But persistent chemicals in riverbeds are “ticking time bombs,” warned Sarah Crawford, an environmental toxicologist at Goethe University Frankfurt and lead author of the paper. The buried chemicals can easily be remobilized. “It just takes one flood event,” she said.

Little Pockets of Pollution

The paper comes from an interdisciplinary research team based mostly in Germany, a country that faced catastrophic floods this year that defied comparison. As the climate warms, similarly intense storms are expected to increase. Floods cause immediate turmoil, but chemical remobilization can prolong the disaster.

“Cohesive sediments are really stable over long ranges of flow velocities, but at some point the sediment bed just fails,” said Markus Brinkmann, an ecotoxicologist at the University of Saskatchewan and a coauthor of the paper.

“Little pockets of contamination are really easily dispersed by flood events.”When the riverbed fails, the turbulent water fills with sediment. That churning water can spread toxins widely. After Germany’s Elbe river flooded in 2002, for example, hexachlorocyclohexane concentrations in fish were 20 times higher than they were before the floods. In another example from 2017, Hurricane Harvey flooded or damaged at least 13 Superfund sites in the United States and sent cancer-causing compounds flowing into Galveston Bay in Texas.

“Little pockets of contamination are really easily dispersed by flood events,” Brinkmann said.

The location of these little pockets is uncertain, complicating the problem. Urban areas and agricultural hot spots are obvious starting points for research and remediation, “but we just can’t pinpoint all of them,” said Crawford. “Maybe a farmer in the ’60s was spraying DDT. We don’t have records of that.”

Other questions remain unanswered. How bioavailable are reintroduced chemicals? How toxic are chemicals after decades bound to sediments? What is the economic risk of inaction? “A lot of this hasn’t been studied,” noted Crawford.

The recent paper doesn’t attempt to answer questions about the presence and release of riverbed toxins but tries, rather, to spur interdisciplinary research on the growing threat.

Involving the Community

Interdisciplinary research is essential for such a complex problem. As evidence, the paper’s 16 authors include a mix of toxicologists, economists, microbiologists, chemists, and engineers.

“To really accomplish this, particularly at the scale [at which] it needs to be done, you can’t have grad students collect every sample. You really need to engage the public.”But it’s important that the research expands beyond academia, too. “To really accomplish this, particularly at the scale [at which] it needs to be done, you can’t have grad students collect every sample,” said Ashaki Rouff, an environmental geochemist at Rutgers University–Newark who was not involved in the research. “You really need to engage the public.”

That often means collaborating with marginalized communities. “Issues of climate change and contamination and pollution disproportionately affect communities of color and low-income communities,” Rouff added. Getting residents involved in the research “is a way to empower those vulnerable communities and get them more agency in the environmental health of their community.”

“It’s really important to work with community-based organizations for this type of work, especially in these types of marginalized communities,” agreed Vanessa Parks, an associate sociologist with RAND Corporation who was not involved in the research. Residents of at-risk regions are well aware of the threat next door; excluding them from the conversation can increase the frustration and psychological burden of living near a contaminated site.

“Working with communities and having open dialogue about the risks and about environmental monitoring can help engender trust,” Parks said.

Ticking Time Bombs Get Louder

While the paper is a call for transdisciplinary action, Crawford and Brinkmann and their colleagues have already facilitated a research network to address the issue. They brought together at RWTH Aachen University in Germany graduate students from multiple disciplines (engineering, economics, ecotoxicology, and more) to research different angles of flood risk and contaminant mobilization. They published an open-access article on their efforts in 2017.

“I really hope to move forward working in an interdisciplinary manner,” said Crawford. “I hope we train this next generation of scientists to be able to communicate across different disciplines.”

It takes only one fast moving flood to rip up buried toxins and contaminate an entire area. As the climate warms and storms intensify, the ticking time bombs of polluted river sediments are only getting louder.

—J. Besl (@J_Besl), Science Writer

AGU sections recognize outstanding work within their fields by annually hosting numerous awards and lectures. Individuals are selected as section honorees on the basis of meritorious work or service toward the advancement and promotion of discovery and solution science. Each one of you made tremendous personal sacrifices and selflessly dedicated yourselves to advancing Earth and space sciences. Your discoveries and solutions are simply remarkable.

We hope you take some time to celebrate your well-deserved recognition. We also know that for each one of you there is a group of people who were invaluable to your success. We greatly appreciate the efforts of those mentors, supportive colleagues, friends, and loved ones.

2021 awardees details:

23 AGU sections gave 78 awards/honors

• 5 awards are for students/postdocs • 28 winners are early-career scientists (up to 10 years post-Ph.D.) • 17 winners are midcareer (10–20 years post-Ph.D.) • 18 winners are senior scientists (experienced and an established leader) • 9 awards are given to honorees in the midcareer or senior career stage • 1 award is given to all career stages • 30 awards are for named lectureships, offered by AGU sections to recognize distinguished scientists with proven leadership in their fields of science

The 30 named lectureships offer unique opportunities to highlight the remarkable accomplishments of the awardees. AGU inaugurated the Bowie Lectures in 1989 to commemorate the 50th presentation of the William Bowie Medal, which is named for AGU’s first president and is the highest honor given by the organization. This year’s Bowie Lectures have an asterisk by their names in the list below. Please add these named lectures to your calendars for #AGU21.

Finally, we are grateful to the nominators, nomination supporters, section leaders, and selection committees for selecting these deserving colleagues. Your volunteer hours are invaluable to our community.

Again, congratulations to the 2021 section awardees and named lecturers!

—Susan Lozier, President, AGU; and LaToya Myles (honors@agu.org), Chair, Honors and Recognition Committee, AGU

 

Atmospheric and Space Electricity Section

Benjamin Franklin Lecture Donald R. MacGorman, Cooperative Institute for Mesoscale Meteorological Studies  

Atmospheric Sciences Section

Atmospheric Sciences Ascent Award Benjamin John Murray, University of Leeds Kerri Pratt, University of Michigan Nicole Riemer, University of Illinois at Urbana-Champaign Isla Simpson, National Center for Atmospheric Research

James R. Holton Award Marysa M. Laguë, Coldwater Lab, University of Saskatchewan

Yoram J. Kaufman Outstanding Research and Unselfish Cooperation Award Oleg Dubovik, University of Lille 1

Jacob Bjerknes Lecture* Joyce Penner, University of Michigan

Jule Gregory Charney Lecture* Wayne H. Schubert, Colorado State University

Future Horizons in Climate Science: Turco Lectureship Yuan Wang, California Institute of Technology  

Biogeosciences Section

Thomas Hilker Early Career Award for Excellence in Biogeosciences Jennifer B. Glass, Georgia Institute of Technology

Sulzman Award for Excellence in Education and Mentoring Susan Natali, Woodwell Climate Research Center

William S. and Carelyn Y. Reeburgh Lecture Edward J. Brook, Oregon State University  

Cryosphere Sciences Section

Cryosphere Early Career Award Brooke Medley, NASA Goddard Space Flight Center

John F. Nye Lecture Andrew Fowler, University of Limerick  

Earth and Planetary Surface Processes Section

G. K. Gilbert Award in Surface Processes David C. Mohrig, University of Texas at Austin

Luna B. Leopold Early Career Award Mathieu G. A. Lapôtre, Stanford University

Marguerite T. Williams Award Nicole M. Gasparini, Tulane University

Robert Sharp Lecture Mathieu G. A. Lapôtre, Stanford University  

Earth and Space Science Informatics Section

Greg Leptoukh Lecture Charles S. Zender, University of California, Irvine  

Education Section

Dorothy LaLonde Stout Education Lecture Emily H. G. Cooperdock, University of Southern California  

Geodesy Section

John Wahr Early Career Award Lin Liu, Chinese University of Hong Kong Surendra Adhikari, Jet Propulsion Laboratory, California Institute of Technology

William Bowie Lecture* Glenn A. Milne, University of Ottawa  

Geomagnetism, Paleomagnetism, and Electromagnetism Section

William Gilbert Award Richard J. Blakely, U.S. Geological Survey

Edward Bullard Lecture* Barbara Maher, Lancaster University  

Global Environmental Change Section

Bert Bolin Global Environmental Change Award and Lecture Thomas L. Delworth, Geophysical Fluid Dynamics Laboratory, NOAA

Global Environmental Change Early Career Award Alexandra G. Konings, Stanford University Bin Zhao, Tsinghua University Kimberly A. Novick, Indiana University Bloomington

Piers J. Sellers Global Environmental Change Mid-Career Award Charles D. Koven, Lawrence Berkeley National Laboratory

Stephen Schneider Lecture Alan Robock, Rutgers University

Tyndall History of Global Environmental Change Lecture Michael D. Dettinger, Scripps Institution of Oceanography  

Hydrology Section

Hydrologic Sciences Early Career Award Laura E. Condon, University of Arizona Adrian Adam Harpold, University of Nevada, Reno Scott Jasechko, University of California, Santa Barbara Pamela L. Sullivan, Oregon State University

Hydrologic Sciences Award Jiri Simunek, University of California, Riverside

Walter Langbein Lecture* John W. Pomeroy, University of Saskatchewan

Paul A. Witherspoon Lecture Junguo Liu, Southern University of Science and Technology  

Mineral and Rock Physics Section

Mineral and Rock Physics Early Career Award Takayuki Ishii, Center for High Pressure Science and Technology Advanced Research

Mineral and Rock Physics Graduate Research Award Kosuke Yabe, Earthquake Research Institute, University of Tokyo

John C. Jamieson Student Paper Award Mingda Lv, Argonne National Laboratory  

Natural Hazards Section

Natural Hazards Section Award for Graduate Research Leah Salditch, Northwestern University

Natural Hazards Early Career Award Chia-Ying Lee, Columbia University Daniel Wright, University of Wisconsin–Madison

Gilbert F. White Distinguished Award and Lecture Gerald E. Galloway, University of Maryland  

Near-Surface Geophysics Section

Near-Surface Geophysics Early Career Achievement Award Ryan Smith, Missouri University of Science and Technology  

Nonlinear Geophysics Section

Ed Lorenz Lecture Valerio Lucarini, University of Reading  

Ocean Sciences Section

Ocean Sciences Early Career Award Malte Jansen, University of Chicago

Ocean Sciences Award Alistair Adcroft, Princeton University and Geophysical Fluid Dynamics Laboratory, NOAA

Rachel Carson Lecture Andrea G. Grottoli, Ohio State University

Harald Sverdrup Lecture Verena Tunnicliffe, University of Victoria  

Paleoceanography and Paleoclimatology Section

Willi Dansgaard Award Aradhna Tripati, University of California, Los Angeles

Harry Elderfield Student Paper Award Jordan T. Abell, University of Arizona

Nanne Weber Early Career Award Clara L. Blättler, University of Chicago  

Planetary Sciences Section

Ronald Greeley Early Career Award in Planetary Sciences Timothy A. Goudge, University of Texas at Austin

Fred Whipple Award and Lecture Paul Schenk, Lunar and Planetary Institute

Eugene Shoemaker Lecture* Athena Coustenis, Laboratoire d’Etudes Spatiales et d’Instrumentation en Astrophysique, Paris Observatory, Centre National de la Recherche Scientifique, Paris Sciences et Lettres University  

Seismology Section

Keiiti Aki Early Career Award Yihe Huang, University of Michigan

Beno Gutenberg Lecture* Gregory C. Beroza, Stanford University  

Space Physics and Aeronomy Section

Eugene Parker Lecture* James A. Klimchuk, NASA Goddard Space Flight Center

Fred L. Scarf Award Luisa Capannolo, Boston University

Space Physics and Aeronomy Richard Carrington Education and Public Outreach Award Keith M. Groves, Institute for Scientific Research, Boston College Elizabeth MacDonald, NASA Goddard Space Flight Center

Sunanda and Santimay Basu International Early Career Award in Sun-Earth Systems Science Chao Yue, Peking University

William B. Hanson Lecture* Jonathan J. Makela, University of Illinois at Urbana-Champaign

James Van Allen Lecture* Mei-Ching Hannah Fok, NASA Goddard Space Flight Center  

Study of the Earth’s Deep Interior Section

Study of the Earth’s Deep Interior Section Award for Graduate Research Mingda Lv, Argonne National Laboratory  

Tectonophysics Section

Jason Morgan Early Career Award Juliane Dannberg, University of Florida

Francis Birch Lecture* Taras Gerya, ETH Zurich  

Volcanology, Geochemistry, and Petrology Section

Hisashi Kuno Award Ming Tang, Peking University

Norman L. Bowen Award and Lecture Catherine Chauvel, Institut de Physique du Globe de Paris George W. Bergantz, University of Washington

Reginald Daly Lecture* Anat Shahar, Carnegie Institution for Science  

Joint Award: Geodesy, Seismology, and Tectonophysics Sections

Paul G. Silver Award for Outstanding Scientific Service Richard W. Allmendinger, Cornell University  

Joint Lecture: Biogeosciences and Planetary Sciences Sections

Carl Sagan Lecture Sarah Stewart Johnson, Georgetown University  

Joint Lecture: Paleoceanography and Paleoclimatology and Ocean Sciences Sections

Cesare Emiliani Lecture Baerbel Hoenisch, Lamont-Doherty Earth Observatory, Columbia University

This is an authorized translation of an Eos article. Esta es una traducción al español autorizada de un artículo de Eos. Una traducción de este artículo (Chino mandarín) fue realizado por Wiley. 本文由Wiley提供翻译稿。

Los proyectos de geoingeniería centrados en reducir las emisiones de gases de efecto invernadero como la plantación de árboles a gran escala, la eliminación de carbono y el almacenamiento de carbono pueden mitigar el cambio climático, pero no sin la adopción generalizada de automóviles eléctricos, según un nuevo estudio.

La nueva investigación muestra que las decisiones individuales desempeñarán un papel importante para ayudar al mundo a cumplir los objetivos globales establecidos por el Acuerdo de París, que apuntan a reducir radicalmente las emisiones de gases de efecto invernadero para 2050.

“Necesitamos hacer estos recortes de emisiones, y la acción individual puede ser una parte importante de eso”, dijo Emily Murray, estudiante de licenciatura en astrofísica de la Universidad de Princeton y autora principal del estudio, publicado en Earth’s Future.

Murray y su supervisora, la profesora de Princeton Andrea DiGiorgio, querían evaluar cómo una acción individual (reducir las emisiones de dióxido de carbono de los vehículos privados alimentados con gasolina), cuando se adopta a escala global, puede tener un efecto comparable a los efectos de los proyectos de geoingeniería.

Murray y DiGiorgio realizaron un meta-análisis de la literatura disponible que examina los impactos generales proyectados de la adopción generalizada de vehículos eléctricos. Calcularon la cantidad de emisiones de carbono que se reducirían al reemplazar los vehículos que queman combustibles fósiles por automóviles eléctricos, teniendo en cuenta la carga adicional que estos vehículos imponen a las centrales eléctricas y las emisiones que liberan.

Los investigadores encontraron que el método más simple de remoción de carbono, la forestación, era la técnica de geoingeniería más efectiva.

Luego, los investigadores examinaron varios métodos de geoingeniería para eliminar el dióxido de carbono de la atmósfera. Estos incluyeron plantar árboles, una técnica llamada meteorización mejorada que utiliza minerales naturales o creados artificialmente para absorber carbono, y técnicas de eliminación directa de dióxido de carbono que implican succionar carbono del aire. También analizaron el uso del consumo de bioenergía combinado con la captura y almacenamiento de carbono y el biocarbón, que almacena carbono en forma de carbón vegetal.

Murray y DiGiorgio calcularon la cantidad de carbono que eliminarían estas técnicas si se desplegaran al máximo para el año 2050. Descubrieron que el método más simple de eliminación de carbono, la forestación, era la técnica de geoingeniería más eficaz en ese período de tiempo.

Sin embargo, la adopción de automóviles eléctricos no se quedó atrás de la forestación como estrategia de mitigación de carbono. Si todos los vehículos de combustibles fósiles fueran reemplazados por Teslas y otros autos eléctricos para el 2034, el impacto sería más efectivo para reducir las emisiones de carbono que los dos métodos menos efectivos de eliminación de carbono combinados: la meteorización mejorada y el biocarbón.

Murray dijo que es poco probable que todas las técnicas de geoingeniería estudiadas en el documento se implementen a gran escala, con la mejor tecnología. Pero incluso si lo fueran, no mitigarían todas las emisiones de carbono.

Continuó diciendo que la adopción de autos eléctricos es una estrategia de mitigación climática más realista, como ya está sucediendo, mientras que algunas de las técnicas de geoingeniería recién se están implementando. (Earth’s Future, https://doi.org/10.1029/2020EF001734, 2021)

—Joshua Rapp Learn (@JoshuaLearn1), Escritor de ciencia

This translation was made possible by a partnership with Planeteando. Esta traducción fue posible gracias a una asociación con Planeteando.

The climate in the tropical Pacific can be fickle. Alexey Fedorov can attest; when he began his career in climate dynamics in 1997, it was the strongest El Niño year on record. The climatic changes contributed to both massive flooding and droughts worldwide. The expectation at the time was that future El Niño events would become even stronger, but El Niño has been relatively quiet since then.

The eastern tropical Pacific (ETP) stretches from the southern tip of the Baja California Peninsula to northern Peru. Credit: Gabriela Agurto, Karla Belén Jaramillo, Jenny Antonia Rodríguez, and Elizabeth Andrade, CC BY-SA 4.0

Because El Niño is one temporary extreme of the natural oscillation in tropical Pacific water temperatures and atmospheric circulation, scientists have tried to predict how climate change will affect the average conditions in the tropics and, in turn, the extremes. Climate models have projected long-term warming of the eastern tropical Pacific Ocean—a region that stretches from the southern tip of the Baja California Peninsula to northern Peru—and weakening of the atmospheric circulation above it, both of which are characteristics of El Niño. But throughout the satellite era, researchers have observed an opposite trend.

“It’s one thing if the models get the trend right but the magnitude off. But when they are the opposite, it’s not great,” said Ulla Heede, a Ph.D. student at Yale University.

In a paper published in July in Nature Climate Change, Heede and Fedorov, now a professor of ocean and atmospheric sciences at Yale, showed that a combination of atmospheric aerosols and a thermostat-like mechanism might be keeping the eastern tropical Pacific cooler than expected. They also said the effect is temporary.

Investigating an “Ocean Thermostat”

An important feature of the tropical Pacific is the zonal atmospheric airflow called the Walker circulation. “In simple terms, it’s the trade winds,” said Fedorov. The trade winds blow warm surface water west, causing an upwelling of cold water in the eastern tropical Pacific and an east-west temperature gradient. The temperature gradient and Walker circulation are tightly linked.

“Over the past 30 years or so, if you look at the trends, you can see a very dramatic strengthening of the Walker circulation,” Fedorov said. “And this is not what the models predict.”

Researchers have thought the discrepancy between models and the observed strengthening might be due to natural climate variability or a built-in ocean thermostat that regulates the eastern tropical Pacific temperature. The latter could occur because the upwelled cold water in the eastern Pacific takes longer to warm relative to the warm surface waters in the western Pacific, which would strengthen the temperature gradient and corresponding Walker circulation.

Heede and Fedorov used 40 models from the Coupled Model Intercomparison Project Phase 6 to see whether the described ocean thermostat regulates eastern tropical Pacific temperature. When they simulated an abrupt carbon dioxide (CO2) increase in the atmosphere, they found that several models exhibited the ocean thermostat. “If [the models] had an ocean thermostat, they tended to have less eastern Pacific warming and less slowdown of the tropical circulation,” Heede said.

But when they ran simulations using the realistic historical emissions, the projections differed from the abrupt-CO2 simulation. The ocean thermostat might be contributing to the Pacific’s response to CO2, but something else in the emissions was having an impact.

Are Aerosols Responsible?

Because emissions consist of both greenhouse gases and aerosols, Heede thought aerosols could be to blame. Anthropogenic aerosols are harmful pollutants emitted as by-products of combustion that can have a cooling effect because they scatter solar radiation away from Earth’s surface. Aerosols dissipate from the atmosphere faster than greenhouse gases, which can last for centuries, so they tend to have the most potent effects close to where they’re produced. The far-reaching impacts of aerosols, likely acting through ocean and atmospheric circulation, are not as well understood. “I have to be honest,” Fedorov said. “Before Ulla started looking at aerosols, I didn’t think about it, because in the tropical Pacific you rarely think about aerosols’ dynamical role.”

“The aerosols, on average, tend to cancel out the warming that would otherwise have happened in the equatorial region.”With 12 models, the researchers could isolate the effects of greenhouse gases and aerosols. Greenhouse gas–only simulations projected warming in the Pacific similar to the abrupt-CO2 simulation, whereas aerosol-only simulations projected cooling. When mixed, “the aerosols, on average, tend to cancel out the warming that would otherwise have happened in the equatorial region,” Heede said.

Like Fedorov, Aaron Levine, a research scientist at the Cooperative Institute for Climate, Ocean, and Ecosystem Studies at the University of Washington who was not involved in the study, was surprised to see aerosols affecting the tropical Pacific. “I don’t see a lot of them in the Pacific,” said Levine, “but they’re strong in the Atlantic.”

Levine expects that the impact in the Pacific might be related to its connections to other oceans, particularly the Atlantic, and future studies should expand on this research by including global data from the models. “The paper really focused on the tropics,” he said.

“It’s Not Going to Stay Forever”

“I think [aerosols are] another piece of the puzzle in terms of understanding future projections of El Niño and how El Niño is going to change.”Although the models responded to aerosols differently, most of them projected eventual eastern tropical Pacific warming over several decades. “Where I think our paper really has something interesting to say is looking into the future,” Heede said. “No matter whether it was aerosols or the ocean thermostat that’s previously canceled out the warming, it’s not going to stay forever.”

As countries worldwide enact clean-air policies, the aerosols in the atmosphere will diminish, and so will their cooling effect. Without aerosols, warming could lead to more extreme weather events and warming of the planet.

“I think [aerosols are] another piece of the puzzle in terms of understanding future projections of El Niño and how El Niño is going to change,” said Levine.

—Andrew Chapman (@Andrew7Chapman), Science Writer

Stonehenge is an iconic monument that has withstood the tests of time.

Its main architecture is composed of sarsen stones, gray megaliths towering more than 6 meters tall and weighing 18 metric tons. Despite their prominence, little is known about the 52 stones that remain of the roughly 80 that were erected during the middle–third millennium BCE.

“What’s exciting about the new study is that they have…attacked Stonehenge, as it were, with all this [new technology].”But now, new technology and an unexpected stroke of luck have allowed researchers to analyze a puzzle at the heart of the site: What are these stones made of? Published in PLOS One, the study provides a comprehensive characterization of the physical and chemical makeup of Stonehenge’s sarsens.

“What’s exciting about the new study is that [researchers] have…attacked Stonehenge, as it were, with all this [new technology],” said Mike Pitts, an archaeologist and journalist who led excavations at the site in 1979 and 1980. “And they’re able to extract information at a really, really fine level in a way that was impossible until quite recently.”

Stone Surfaces and Serendipity

David Nash, a physical geographer at the University of Brighton in the United Kingdom, led the study. His team began by analyzing the surface of each sarsen over multiple night shifts and one “very early morning shift” when tourists were not around.

https://eos.org/wp-content/uploads/2021/09/new-stonehenge-geochemistry.mp4

Using a portable X-ray fluorescence spectrometer (“it looks like a big sci-fi ray gun,” Nash said), the researchers took five measurements from each of the 52 stones, making sure to hold perfectly still for 2 minutes each time. The team stood in the dark, cold night with headlamps, trying to find patches of stone without lichen cover. Save for a few security guards, there was nobody else around, Nash said. “So, yeah, it’s a bit creepy.”

The team’s measurements, careful though they might have been, could go only so deep. They could not provide information about what lies beneath the surface. And because Stonehenge is so protected by the government, they could not take any samples of the stones’ interiors.

But then serendipity struck: As his team was wrapping up the fieldwork at Stonehenge, Nash received an email from the English Heritage Trust, the nonprofit organization that manages Stonehenge and hundreds of other historic sites in Britain.

“They emailed me and said, ‘We understand that you’re doing work on the chemistry of the stones at the moment. Could you give us a ring?’” Nash said. “My immediate reaction was, ‘Oh, God, what have we done wrong?’”

English Heritage shared information about the massive 1958 restoration project at Stonehenge. The project reerected three stones at the site, including Stone 58, a large upright sarsen that had toppled in 1797. To reinforce a fissure, three cores were drilled through Stone 58 to install metal rods.

David Nash of the University of Brighton analyzes a core extracted from Stone 58 at Stonehenge. Credit: Sam Frost/English Heritage

One core was gifted to Robert Phillips, a worker at the drilling company involved in the project. (Part of a second core was later uncovered at nearby Salisbury Museum in a box labeled “Treasure Box.” The location of the third core is still unknown.) Phillips hung the core in a protective tube in his office until his retirement, and kept it through his subsequent moves to New York, Illinois, California, and, finally, Florida. As Phillips approached 90, he sought to return this important artifact and had it delivered to English Heritage in 2018.

Phillips’s Stone 58 core, whose existence was previously unknown to any of the researchers, was lent to Nash’s team, which was able to sample and examine it in detail.

“It’s the first time that we’ve been able to look inside one of the stones at Stonehenge,” Nash said.

“They just did everything imaginable with it,” said Pitts, who was not involved in the study. “I mean, it has to be the most analyzed piece of rock on Earth.”

Remarkably Pure and Incredibly Durable

Scrutinizing the cores with state-of-the-art petrographic, mineralogical, and geochemical techniques revealed a reason why the long-standing sarsen stones at Stonehenge may be so enduring.

The core was 99.7% silica—almost entirely quartz, through-and-through, which was more pure than any sarsen stone Nash had worked on. Under the microscope, its sand-sized quartz grains were tightly packed together and supporting each other. The grains were then coated in an overgrowth cement—at least 16 different growth layers that could be counted almost like tree rings—which produced an “interlocking mosaic of quartz crystals that bind the stone together,” Nash said.

Cathodoluminescence imaging of a sarsen stone reveals the outlines of sand grains (pale blue, black) and multiple layers of quartz cement (red). Credit: Trustees of the Natural History Museum

“That’s probably why the sarsens were so big and have been so durable,” Nash said. “Because it’s an incredibly well cemented stone.”

The research also indicated that the dull gray Stonehenge we see today is probably not what it looked like when it was first built.

“When the stones were originally raised, they were dressed, they were cleaned up on the outside,” Nash said. “The fresh rock would have looked a creamy white color, and it must have been amazing.”

Data about Stone 58 can be applied to most of the other sarsens and to where they originated: In a 2020 paper published in Science Advances, Nash and his colleagues found that Stone 58 is geochemically similar to and representative of 50 of the remaining 52 sarsens at Stonehenge. These sarsens share geochemical signatures with sarsens in West Woods in Wiltshire, about 25 kilometers north of Stonehenge—the stones’ most probable source.

The large sarsen stones at West Woods in Wiltshire are the probable source of most sarsens used to construct nearby Stonehenge. Credit: Katy Whitaker/Historic England/University of Reading

The new study also lays the groundwork for future research by making all the data open-access.

“We were basically being given access to an absolutely unique sample that was of national importance,” Nash said. “And what we wanted to make sure we did was analyze it using every single modern technique that we could, with the view being that for future studies of Stonehenge, if other people are doing more work…there was a big suite of data that people could use.”

“Having access to this stone, you realize that you’re really privileged to be able to do this work,” he added. “So you want to do it right because you can’t go back.”

—Richard J. Sima (@richardsima), Science Writer

The Mississippi River Delta is sinking, its coastal wetlands are disappearing, and its coastal marshes are drowning. The delta has been aggressively engineered for about 200 years, with the building of diversions (like levees or alternate channel paths) to control the flow of water. As with many deltas, those diversions are often built near the coast. But a novel approach has identified a better location: cities.

The strategies behind most river diversions are driven by economic concerns and “really ignore the natural process of the river to want to avulse at a specific place with some average frequency,” said Andrew Moodie, a postdoctoral researcher at the University of Texas at Austin. The process of avulsion, in which a river jumps its banks to flow on a steeper slope, is crucial to flooding and river dynamics. But diversions notwithstanding, that water will eventually go where it wants, which can result in flooding, loss of homes and businesses, and even loss of life.

Moodie and his colleagues’ new research, published in the Proceedings of the National Academy of Sciences of the United States of America, describes a new framework for selecting the optimal placement for river diversions. “Because of the interaction between the river wanting to do what rivers do and a society that wants to minimize damage to itself, there emerges a best location that does both of those things,” said Moodie. “It lets the river do the closest to what it wants to do, but it also minimizes the damage to the society.”

Downtown Diversions

“It’s actually easier to justify more expensive projects because you have to protect this infrastructure now or you lose so many more benefits from it.”Moodie’s framework combines two models. The first simulates river and sediment movement scenarios to predict the timing of avulsions; the second estimates the societal benefits of diversions by factoring the cost of flooding damage and the costs of diversion engineering, like buying land and construction, as well as annual revenues (from agriculture, for example).

Moodie’s framework points to urban areas as often better locations for river diversions than the rural and suburban areas where most river diversions are constructed. This finding counters a prevailing theory that cities are less sustainable and may have to be abandoned as seas continue to rise. Placing diversions closer to cities makes economic sense because losses from flooded farmland may last a season, but floods in urban areas can cause longer-term damage. “It’s actually easier to justify more expensive projects because you have to protect this infrastructure now or you lose so many more benefits from it,” he said.

The biggest challenge to implementing a new river diversion framework is involving different parties and their needs, which are diverse and sometime conflicting. Shareholders include rural, suburban, and urban residents and landowners; agricultural businesses; water engineers; municipal, state, and regional governments; environmental organizations; and local community leaders.

“River management has a complex history that we’re trying to fit into,” Moodie said. “We are geomorphologists, we’re scientists, but we recognize and want to stress the importance of contextualizing our work within the societies that it matters to.”

The Mississippi River Delta has been engineered for hundreds of years and is sinking—but a new approach to river diversions outlined by Andrew Moodie (pictured) could help protect it. Credit: Andrew Moodie

Jaap Nienhuis, an associate professor of geosciences at Utrecht University in the Netherlands who was not involved in the new research, said the study is elegant and novel. “It’s one of the first papers that tries to couple human action and also landscape dynamics for river deltas,” he said.

The framework could help river engineers and others responsible for river management by offering a discrete set of parameters, said Nienhuis. “It gives people an overview of things to consider without it getting out of hand in terms of the things you need to worry about.”

Sea Level Rise

Flooding is not, of course, a problem limited to the Mississippi Delta; it’s happening around the world because of sea level rise, storm surge increases, and human interventions, like sea walls, which can make the problems worse.

While land subsides, climate change is contributing to sea level rise. Climate change is also contributing to more frequent and violent coastal storms. Infrastructure like dams and levees protects communities from floods but interrupts sediment flow, which deltas need to form natural wetlands that protect inland regions.

“By protecting us from floods, we’ve also eliminated any natural land area gain or elevation gain in deltas,” Nienhuis said. “So we’re definitely trying to shift the focus to how can we have diversions, for example, that would make deltas gain some land and be more resilient against sea level rise.”

Sea level rise itself is a variable Nienhuis would like to see incorporated into Moodie’s framework. The current models “keep sea level constant, and [researchers] let the delta grow,” he said. “It would be interesting and I think a relatively straightforward follow-up to have sea level rise and see what that does to these findings.”

—Danielle Beurteaux (@daniellebeurt), Science Writer

A consequence of the climate emergency is the melting of glaciers around the world. Melting is revealing their internal structures in remarkable detail, as snow is removed and the surface is stripped bare. We can now see that ice structures record an intricate record of present and past glacier dynamics, a record that commonly cannot be ascertained by other means. By combining structural glaciological techniques with satellite remote sensing, the flow characteristics of large and remote ice masses, both globally and extra-terrestrially, can be determined, potentially revealing flow histories that extend over centuries to millennia. A recent article published in Reviews of Geophysics gives a synopsis of nearly two centuries’ worth of structural glaciological investigations, and highlights the major challenges yet to be tackled.

Why is it important to understand the dynamics of glaciers and ice sheets and how they are changing?

Approximately 10 percent of the Earth’s land surface is covered by ice, which has a significant influence on global climate, ocean cycles, as well as on human activities.

The behavior of glaciers and ice sheets is fundamentally changing in response to human-induced global heating.However, the behavior of glaciers and ice sheets is fundamentally changing in response to human-induced global heating. Increasing air and ocean temperatures are melting ice masses, reducing their size.

These processes are leading to the collapse of ice shelves, altering how glaciers flow, and increasing ice discharge into the ocean.

It is important to understand these dynamic changes in order to predict potential future impacts on humanity. On a global scale, such impacts include raising of sea level and changing climate and ocean cycles, while on a regional scale changes in water security are an increasing threat to mountain communities and the vast populations that live downstream.

Why is it important that glaciers be studied in four dimensions?

We need to consider the study of glacier structures as a four-dimensional exercise. We observe and map glacier structures spatially in two dimensions, in plan view, to determine the range, pattern, and inter-relationships of the different structures. The third dimension combines recording the orientation of structures at the surface with ice-penetrating radar measurements. The fourth dimension is time, which requires us to look back at historical records revealed in old photographs and satellite imagery and figure out how structural changes take place from what is visible today.

What is the structure of a typical glacier?

All glaciers, regardless of size, are composed of layers of snow that build up in the upper reaches of an ice mass, become buried, and transform into glacier ice as they are increasingly compressed by the overlying column of snow.

We refer to the initial snow layering as stratification, and this represents the ‘building blocks’ of a glacier. The majority of other structures are the result of how the glacier flows under gravity, a process that produces a complex array of structures. Firstly, where the ice deforms in a brittle manner, crevasses (V-shaped clefts in the ice) and a variety of fractures develop, which can be a major hazard for glacier travel. Secondly, ice also deforms in a ductile manner, leading to the development of a variety of folds, foliation (a layered structure commonly visible in glaciers), and a variety of lesser-known structures.

The terminus of Fountain Glacier, Bylot Island, Canadian Arctic, in which a wide range of structures are displayed, the most prominent of which are the traces of former crevasses. Credit: Michael J. Hambrey

How does our understanding of structures found in rocks help us understand the structure and behavior of ice, and vice versa?

Concepts in structural glaciology have constantly lagged behind those in geology.We consider glacier ice to be equivalent to a metamorphic rock because it deforms close to its melting point in both a brittle and ductile manner. While the study of structures in rocks has developed into a highly sophisticated, mathematically and physically based discipline, concepts in structural glaciology have constantly lagged behind those in geology.

However, if we apply structural geological principles to glaciers we can advance our understanding of glacier dynamics, notably because the same range of structures occur in both rock and ice.

Conversely, we can observe structures in glaciers forming on human timescales, reflecting the same processes that occur in rocks many kilometers below the surface of the Earth on a time scale of millions of years. This means that glacier ice deforms up to six orders of magnitude quicker than rocks in active mountain belts, and therefore a glacier can be considered as an analog of rock deformation. Consequently, glaciers can be used as natural laboratories that enable geologists to directly observe the formation and development of structures.

What does glacier structure tell us about changes on different spatial and temporal scales?

The advent of satellite remote sensing has revolutionized our understanding of inaccessible glaciers and ice sheets. However, satellite measurements only extend back for approximately half a century. As ice structures form in response to how a glacier flows, they preserve a record of glacier dynamics that covers the time that ice follows a path through the glacier system. In comparatively small valley glaciers, ice residence times can span centuries, increasing to millennia or even a few million years in the Antarctic Ice Sheet. Ice structures therefore have the potential to inform scientists about how glaciers have behaved in the past and how they have changed over time.

How might a structural approach be of use in other sub-disciplines of glaciology?

Ice structures have a fundamental, yet often overlooked, influence over many other aspects of glaciology. For example, glacier structures play a large role in the routing of meltwater through a glacier, dictating how water gets to the glacier bed, which in turn controls how quickly the glacier flows. Structures also strongly influence how debris is transported in glaciers, and this has an impact on how many glacial landforms are interpreted. Glacier structures also control the distribution of microbial life living on the surface of glaciers, and structural glaciology is a useful tool for exploring the mechanisms of glacier recession. All of these topics have a great deal of untapped potential for further study.

The corrugated surface of the valley glacier Austre Brøggerbreen in Svalbard (Norwegian High-Arctic) in summer 2013. This is a product of weathering of different ice structures, especially longitudinal foliation and the traces of former crevasse. Credit: Michael J. Hambrey

Where is further research, data gathering, or modeling needed to advance our understanding of glacier dynamics?

Modern remote sensing-based techniques have the potential for expanding the range of deformation studies over large and small ice masses.The principal challenge for structural glaciologists is to understand how ice structures develop spatially, at depth, and over time. Direct measurement of deformation in valley glaciers goes back over half a century but it is a laborious field-based process. Modern remote sensing-based techniques, such as feature-tracking and interferometry, have the potential for expanding the range of deformation studies over large and small ice masses.

Some advances have been made in replicating the formation of glacier structures in computer models, especially regarding pervasive structures such as foliation. Modeling other structures, such as fractures, has proved more elusive, but the challenge can be met using more powerful computers.

With the rapidly growing amount and quality of remote sensing data, the scope for structural studies has grown enormously. We have only scratched the surface of the potential research opportunities here, but it is clear that structural principles can then be applied to unraveling the history of many inaccessible ice masses on Earth, and even on Mars.

Scaling down to the microscopic level, there also remains the untapped potential for structural glaciology to illuminate the recently emerged field of cryospheric microbiology. These new opportunities demonstrate that there has never been a more exciting time to engage with the field of structural glaciology.

—Stephen J. A. Jennings (stephen.ja.jennings@gmail.com;  0000-0003-4255-4522), Polar-Geo-Lab, Department of Geography, Masaryk University, Czech Republic; and Michael J. Hambrey ( 0000-0003-0662-1783), Centre for Glaciology, Department of Geography and Earth Sciences, Aberystwyth University, United Kingdom

Earth’s aurorae form when charged particles from the magnetosphere strike molecules in the atmosphere, energizing or even ionizing them. As the molecules relax to the ground state, they emit a photon of visible light in a characteristic color. These colliding particles—largely electrons—are accelerated by localized electric fields parallel to the local magnetic field occurring in a region spanning several Earth radii.

Evidence of these electric fields has been provided by sounding rocket and spacecraft missions dating to as far back as the 1960s, yet no definitive formation mechanism has been accepted. To properly discriminate between a number of hypotheses, researchers need a better understanding of the spatial and temporal distribution and evolution of these fields. When the European Space Agency’s (ESA) Cluster mission lowered its perigee in 2008, these observations became possible.

Cluster consists of four identical spacecraft, flying with separations that can vary from tens of kilometers to tens of thousands. Simultaneous observations between the four craft enable space physicists to deduce the 3D structure of the electric field.

Marklund and Lindqvist collect and summarize the contributions of Cluster to our understanding of the auroral acceleration region (AAR), the area of space in which the above-described processes take place.

By collecting a large number of Cluster transits through this region, physicists have deduced that the AAR can generally be found somewhere between 1 and 4.4 Earth radii above the surface, with the bulk of the acceleration taking place in the lower third. Despite this relatively broad “statistical AAR,” the acceleration region at any given moment is usually thin; in one observation, for example, the AAR was confined to an altitude range of 0.4 Earth radius, whereas the actual layer was likely much thinner than that. The observations cannot uniquely determine the thickness of the actual layer, which could be as small as the order of 1 kilometer, the authors say. Such structures are observed to remain stable for minutes at a time.

Cluster measurements also have shed light on the connection between the observed shape of the electron acceleration potential and the underlying plasma environment. So-called S-shaped potentials arise in the presence of sharp plasma density transitions, whereas U-shaped ones are related to more diffuse boundaries. However, the dynamic nature of space plasma means that the morphology of a boundary can shift on timescales of minutes, as exemplified by a case study.

In sum, 2 decades of Cluster observations have significantly improved our understanding of the processes—both local and broad—that result in our planet’s beautiful aurorae. With the missions extended through 2022, we can expect more insight in the coming years. (Journal of Geophysical Research: Space Physics, https://doi.org/10.1029/2021JA029497, 2021)

—Morgan Rehnberg, Science Writer

This is an authorized translation of an Eos article. 本文是Eos文章的授权翻译。

路边的沟渠汇集了落在路面的雨水以及草坪或田地里的径流。尽管沟渠在景观中无处不在，但它们的潜力远远超过了雨水管道。事实上，沟渠是人类制造的低地，经常扮演着湿地的角色，有起伏的水位和大量的植被和微生物。

在这些人造景观中，微生物和植被有能力将氮从流入的水中剥离出来，将其从系统中移除。在此过程中，沟渠中脱氮可以减少过量营养物质对下游的影响，如藻华和死区。

但沟渠脱氮的效果如何呢?到目前为止，人们对其知之甚少。

在一项新的研究中，Tatariw等人比较了森林、城市和农田附近的沟渠的脱氮情况，以及在每个地方生活的微生物种类。他们观察了阿拉巴马州莫比尔湾附近的三个不同的流域，并对沿双车道公路延伸的96个不同的沟渠进行了取样。每个流域代表沿森林、已开发土地或农业用地的沟渠。

为表征这些沟渠，研究小组考察了植物生物量、水中无机氮含量和土壤特征。因为微生物太小，即使用显微镜也无法识别，所以科学家们使用16S rRNA基因来识别和分析每个样本中的不同微生物。

最后，研究人员通过采集土壤样本、加水和制作沟渠材料浆料计算出了每个样本去除硝酸盐的潜力。通过在浆料中加入稳定的氮同位素(15硝酸盐)，来观察样品中的微生物减少了多少氮。

研究发现沟渠中的微生物对硝酸盐(NO3 -)的去除潜力平均高达89%。尽管不同沟渠之间的土壤特征相似，研究小组指出，在人类活动普遍的城市和农业沟渠中，特定的微生物——如亚硝化球藻科、亚硝化索藻科、盖叶目和粘粒菌——更为丰富。

总的来说，沟渠被发现具有与湿地和河流等许多自然生态系统相类似的脱氮潜力。这项新的研究表明，路边的沟渠可能是去除环境中氮的重要区域。(Journal of Geophysical Research: Biogeosciences, https://doi.org/10.1029/2020JG006115, 2021)

-科学作家Sarah Derouin

This translation was made by Wiley. 本文翻译由Wiley提供。

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At the University of Minnesota (UMN), we are reckoning with the story we tell about geology in our state. In the 19th century, the belief in manifest destiny drove white settlers to expand rapidly into the West, leading to the widespread removal of Indigenous Peoples from their homelands, genocide, and harm to their knowledge systems and lifeways. Geological mapping played a significant role in identifying which lands were profitable for U.S. settlement through gold and other natural resource extraction. The Minnesota Geologic and Natural History Survey was founded in 1872 and restarted in 1911 as the Minnesota Geological Survey (MGS) under UMN’s Newton Horace Winchell School of Earth and Environmental Sciences. The original purpose of the survey was to economically evaluate the “mineral kingdom” of Minnesota; today, the MGS mission is to identify and support stewardship of water, land, and mineral resources. The program was named for and first led by Newton Horace Winchell—a pioneering geologist discussed in most UMN geology courses. Winchell led mapping surveys, sometimes accompanied by the U.S. military, including George Armstrong Custer, into Indigenous land that directly led to mining explorations, white settlement, and, eventually, U.S. takeover of these lands through violence and coercion.

Geologists learn about Newton Horace Winchell’s discoveries stripped from the violence that followed or made them possible.But geologists—including the ones serving at MGS today—learn about Winchell’s discoveries stripped from the violence that followed or made them possible. Although geologic mapping of the state contributed to advances in the stewardship of natural resources and public health, we must acknowledge the cost of these benefits. As two white geologists in the MGS and the UMN School of Earth and Environmental Sciences, we and our colleagues are making efforts to integrate lessons from our regional history into our policies that govern our relationships with Indigenous Peoples. Not only will this critical reflection acknowledge racist actions and the immense pain caused by them, but it also will allow the MGS to conduct ongoing work more justly, by collaborating with tribal neighbors to decide how and where MGS performs its mapping.

Geologic Mapping and Land Dispossession

First, we must look back at our history, starting with the U.S. government–funded expeditions to map west of the Mississippi River in the early 19th century. These expeditions included naturalists who described the surrounding nature and geology in works credited today for advancing the knowledge of the geography of Minnesota. These surveys inspired settlers to move to Dakota and Ojibwe homelands in what the U.S. government began calling the territory of Minnesota on the basis of the Dakota name, Mni Sóta Maḳoce.

These surveys were not the first scientific understandings of these landscapes. Indigenous Peoples have always had their own knowledge systems and sciences of Earth [see Daniel, 2019; Evans, 2020; Cartier, 2019; Reano and Ridgeway, 2015]. To the Dakota and Ojibwe, some rocks and metals such as pipestone and copper hold deep spiritual importance and animacy. Indigenous place-names and maps also reveal a rich understanding of place [see Brooks, 2018; Smith, 2018]. Generations of European and American explorers relied extensively on Ojibwe and Dakota guides to navigate the waterways and landscapes of Minnesota.

In 1837, the U.S. government began promulgating a series of treaties that forced the Dakota and Ojibwe people to cede most of their land. One concession would lead directly to another. A geological report by David Dale Owen, published in 1852, mapped the mineral potential of land ceded in the 1851 Dakota Land Cession Treaties, as well as land still held by the Dakota and Ojibwe. Owen documented, for example, unceded tracts of bedrock along the north shore of Lake Superior in the Arrowhead region of Minnesota. This report likely aided mining companies in persuading the federal government to acquire the land—which they did 2 years later in 1854.

The federal government paid pennies on the dollar to the Dakota on the value appraisals gave the land at the time, turning it into wealth that the UMN continues to benefit from today.Minnesota was granted statehood in 1858, and in 1865, the Minnesota legislature appointed Henry H. Eames as the first state geologist. Eames produced two annual reports that focused on the region north of Lake Superior, where he claimed to have found a major gold deposit. In the heady gold rush that followed, a “quasi-military organization” made up of former soldiers recently returned from the Civil War set up shop as the first gold mining company at Lake Vermilion. They settled in unceded lands where the Bois Forte Band of Chippewa resided. To avoid violence, the Bois Forte Band ceded their land surrounding the lake and were forced to accept a smaller reservation farther northwest. But the “second California,” as Eames boasted to potential financiers in New York, never materialized because Eames’s claims of gold turned out to be fraudulent. The damage was done, however, and geologic mapping and mining research around the lake turned to focus on the nearby massive iron ore deposits.

Indigenous land dispossession not only resulted from geological mapping; it actually funded some of the surveys. The Morrill Land-Grant Act handed over 145 square miles (375 square kilometers), 98% of it ceded Dakota territory, to the State of Minnesota, which later assigned the benefits of the act to the University of Minnesota in 1868. Additional lands were granted specifically to fund the Minnesota Geologic and Natural History Survey in 1873. The federal government paid pennies on the dollar to the Dakota on the value appraisals gave the land at the time, turning it into wealth that the UMN continues to benefit from today.

Our Stories of Geology

Winchell’s legacy is still discussed in modern textbooks and biographies published as recently as 2020. These works largely excuse or ignore the racism embedded in his views and the ethics of his science as being a consequence of a different time. Michi Saagiig Nishnaabeg scholar, writer, and activist Leanne Simpson points out in her book As We Have Always Done, however, that this type of thinking normalizes the white, settler perspective and erases the perspective of Indigenous Peoples. She asks, “Whose historical context and whose standards” are we evaluating history based upon? Winchell’s legacy must also be evaluated in the historical context and standards of Indigenous Peoples.

Early in his career as survey director, Winchell and other scientists accompanied George Armstrong Custer in the 1874 Black Hills Expedition, an expedition that advanced the dispossession of Lakota homelands. Sioux scholar Nick Estes explains in his book Our History Is the Future that the Black Hills—He Sapa in the Lakota language—are “the heart of everything that is” to the Lakota people and sacred to more than 50 Indigenous nations. The 1868 Treaty of Fort Laramie banned U.S. citizens from entering the Lakota reservation encompassing the Black Hills except for those employed and authorized by the U.S. government to do so. Custer’s military obtained this authorization by claiming the expedition was for reconnaissance, whereas the geologists, including Winchell, said they were looking for fossils. The expedition’s miners actually struck gold, and the rush of white settlement and U.S. land claims that followed were in clear violation of the treaty. Although Winchell himself may not have been seeking gold, he chose to participate in a military expedition on Lakota territory prominently connected with gold exploration and the drive for U.S. expansion. Yet the ethics of this research are not widely discussed, if at all, in the history of geology presented at UMN or in biographies.

Without this context, Winchell and his research appear unattached to the ongoing genocide and land dispossession of Indigenous Peoples as the U.S. expanded into the Midwest during the 19th century. Geology is not neutral within the politics of colonization, a point further developed and expanded in Kathryn Yusoff’s book A Billion Black Anthropocenes or None. How we tell the story of geology either contributes to the status quo of colonization or challenges these privileged narratives to open up the possibility for a more just future.

Opportunities for Change

In 2019, we at the UMN School of Earth and Environmental Sciences were given an opportunity to better understand our science’s history when one of the Minnesota tribal nations asked for their lands to be excluded from a MGS geologic map in progress. They believed that publicly available geologic information could jeopardize protection of their lands and that the MGS would not inform the tribe of all the potential uses of data collected. At first this request bewildered MGS geologists, who were not properly taught our discipline’s history, but then spurred movement within the organization to learn about our region’s treaties and the relationship between tribal sovereignty and geologic mapping.

These rights mean that each tribal nation can and should make its own decision on what geologic information the MGS can collect and how geologic mapping might affect its people.The MGS researchers learned that each tribal nation within the footprint of Minnesota and throughout the U.S. retains its sovereignty and, along with all Indigenous Peoples, has the right to self-determination. These rights mean that each tribal nation can and should make its own decision on what geologic information the MGS can collect and how geologic mapping might affect its people. With this knowledge, the MGS began to create its first policy for mapping and collecting data on tribal lands. We began by reaching out to the UMN senior director of American Indian Tribal Nation Relations, who advised the MGS to reach out to each tribe’s environmental resources program directors. In these meetings, MGS leadership shared its mission along with the mapping projects that would affect the tribe’s lands. Next, the tribal environmental resources directors asked their tribal government to vote on their involvement in the MGS project. Some tribes wanted updated geological maps from the MGS, whereas other tribes stated they already had the capacity to make their own maps and thus declined permission for the MGS to survey their land.

The new policy states that MGS will offer opportunities to tribes to consult on surveys and other operational activity that may affect their land, water, or other natural resources, even if that activity is not directly on their land. MGS now requires explicit permission from tribal governments to collect new data on tribal lands and will also, upon request, “gray out” tribal lands on geologic maps and related products. Although the MGS has customized its policies to honor specific requests made by the sovereign Indigenous nations in our region, we modeled them generally on policies of both the U.S. Geological Survey and the Minnesota Pollution Control Agency.

As our experience demonstrates, geologists must understand how the many discoveries in our discipline were actually made; otherwise, our work will continue to further the colonization of Indigenous Peoples. We must learn the complete history of geology’s relationship with colonization, invite reflection from Indigenous Peoples, and require our scientific community to understand and respect tribal sovereignty through our policies. This work must extend to our geoscience classrooms as we train the next generation of Earth and environmental scientists, consultants, and regulators. Students, faculty, staff, and researchers within the MGS and the UMN School of Earth and Environmental Science have raised these demands, supported by national efforts calling for this work.

The academic department within the UMN School of Earth and Environmental Sciences is also beginning to take action. The department is in the process of recommending American Indian studies courses for undergraduates and graduate students on our website and in advising meetings. Faculty and students continue to assess whether collections contain specimens that were stolen from Indigenous Peoples and are developing repatriation procedures. Indigenous Earth scientists and scholars are being invited to speak at department geology seminars as well as lunchtime justice, diversity, equity, and inclusion talks. Students and faculty are reviewing and editing department curriculum to ensure that it respectfully includes Indigenous Peoples’ histories and the colonial legacy of geoscience and geoengineering in Minnesota. Faculty and students are working with Indigenous scholars to create a land and water acknowledgment and develop policies for our department to work more ethically on Indigenous homelands. These actions are only the first steps, and we have a lot left to learn on this journey.

We still have many questions to discuss together: What should the MGS do with historical maps, data, and projects published without tribal consent? How can the MGS redress harms and incorporate the perspectives and knowledges of Indigenous Peoples?MGS geologists have embarked on composing a detailed report on their program’s past and ongoing colonial practices, which will be published on the MGS website. We also are continuing to refine our policies for geologic mapping on tribal lands. Building and maintaining respectful relationships with tribal governments will require time and accountability from the MGS, as another recent UMN-tribal collaboration has demonstrated. We still have many questions to discuss together: What should the MGS do with historical maps, data, and projects published without tribal consent? Can the MGS provide services to tribes in stewarding their land, mineral, and groundwater resources? How has the UMN geological research supported mining industries at the expense of Indigenous Peoples’ treaty rights, economic prosperity, self-determination, and access to sacred sites? How can the MGS redress harms and incorporate the perspectives and knowledges of Indigenous Peoples? Fundamentally, how can the MGS and the geological community develop and follow ethics that account for and disrupt this discipline’s entanglement in colonization?

Reimagining Our Science Together

Colonialism is ingrained within much of geology’s foundation. Geologic institutions must be forthright in recognizing the role scientists in our field have played—and continue to play—in the dispossession of Indigenous Peoples from their lands around the world and, consequently, disrupting their lifeways and knowledge systems. We also have an opportunity to make the practice of our science more just, as well as deeper and more expansive, by critically understanding our past, stopping and redressing harms, and building respectful relationships with Indigenous Peoples for an equitable exchange of knowledges. Our work at MGS and at the UMN Earth and Environmental Sciences Department is far from done, but we look forward to reimagining our science and how it can support the well-being and self-determination of Indigenous Peoples.

Acknowledgments

This paper would not have been possible without the guidance, support, and feedback from Mike Dockry (UMN forestry professor), Margaret Watkins (Grand Portage Band of Lake Superior Chippewa water quality specialist), Kari Hedin (Fond du Lac Band of Lake Superior Chippewa watershed specialist), Tony Runkel (MGS lead geologist), Hannah Jo King (UMN natural resources, sciences, and management graduate student), Crystal Ng (UMN hydrology professor), Laura Paynter (UMN public policy graduate student), Erick Moore (head of UMN Archives), the UMN American Indian and Indigenous Studies writing workshop, the UMN Institute for Advanced Studies Land-Grant/Land-Grab Fellowship cohort, the Earth and Environmental Sciences Department Unlearning Racism in Geoscience (URGE) Pods, and the Kawe Gidaa-naanaagadawendaamin Manoomin project team.

The largest alpine lake system in the world sits atop the Qinghai-Tibet Plateau, commonly known as the Tibetan Plateau, which is the highest and largest plateau in the world. Researchers know the lakes influence the transfer of heat between the land and atmosphere, affecting regional temperatures and precipitation. But little is known about the physical properties and thermal dynamics of Tibetan lakes, especially during the winter months when the lakes are covered in ice.

In a new study, Kirillin et al. looked at China’s Ngoring Lake—the largest freshwater lake (610 square kilometers) on the plateau—which is typically covered in ice from December through mid-April. The team moored temperature, pressure, and radiation loggers in one of the deepest parts of the lake in September 2015. They observed an anomalous warming trend after the lake surface froze over, as solar radiation at the surface warmed the upper water layers under the ice. Strong convective mixing left Ngoring Lake fully mixed down to its mean depth within a month of full ice cover.

In most ice-topped lakes, water temperatures typically remain below the maximum density temperature, but here the authors found that the water temperature was higher than the maximum freshwater density by the middle of the ice season, which accelerated the ice melt at the end of the winter season. As the ice broke up, water temperature dropped by nearly 1°C, releasing some 500 watts per square meter of heat into the atmosphere in just 1 or 2 days.

The study demonstrates that lakes do not lie dormant under ice. But the impacts extend beyond local lake effects; taken together, the thousands of lakes across the plateau could be heat flux hot spots after ice melt, releasing the heat absorbed from solar radiation and driving changes in temperatures, convection, and water mass flux with potential impacts at even global scales. (Geophysical Research Letters, https://doi.org/10.1029/2021GL093429, 2021)

—Kate Wheeling, Science Writer