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Radiosondes Measure Atmospheric Turbulence Over North America

Fri, 08/16/2019 - 11:30

Absolute measurements of turbulence in the atmosphere are difficult to obtain, and it is even harder to get large amounts of reliable observations. Ko et al. [2019] present turbulence characteristics derived from a large data set of twice-daily, high-vertical-resolution (approximately 5 meters) radiosonde balloon measurements at 68 stations over the United States, using several years of data. Analysis is based on deducing unstable thermodynamic vertical structure using the so-called “Thorpe analysis”, which is becoming widely accepted as a true measure of turbulent energy dissipation rates.

Results in this study highlight stronger turbulence and energy dissipation in the troposphere than in the stratosphere, with a strong seasonal cycle and geographic structure in troposphere statistics (see map above). These results provide novel characterization of turbulence behavior on large spatial and temporal scales, which are useful for aviation turbulence studies and for improving numerical weather prediction models.

Citation: Ko, H.‐C., Chun, H.‐Y., Wilson, R., & Geller, M. A. [2019]. Characteristics of atmospheric turbulence retrieved from high vertical‐resolution radiosonde data in the United States. Journal of Geophysical Research: Atmospheres, 124. https://doi.org/10.1029/2019JD030287

—William J. Randel, Editor, JGR: Atmospheres

Twenty-Five AGU Members Awarded the 2019 Presidential Early Career Award

Fri, 08/16/2019 - 11:04

On 2 July 2019, 25 AGU member scientists were awarded the Presidential Early Career Award for Scientists and Engineers (PECASE) by the White House Office of Science and Technology Policy. This is “the highest honor bestowed by the United States Government to outstanding scientists and engineers who are beginning their independent research careers and who show exceptional promise for leadership in science and technology.”

The diverse cohort of AGU awardees hails from across the United States and is working in a variety of Earth and space science fields, including volcanology, astrobiology, and polar science. The 2019 AGU member award recipients are as follows:

Eric Anderson, Great Lakes Environmental Research Laboratory, National Oceanic and Atmospheric Administration (NOAA)

Annemarie Baltay, Earthquake Science Center, U.S. Geological Survey (USGS)

Laura Barge, NASA Jet Propulsion Laboratory, California Institute of Technology

Whitney Behr, Department of Earth Sciences, ETH Zürich

Lynn Carter, Lunar and Planetary Laboratory, University of Arizona

Nicolas Cassar, Nicholas School of the Environment, Duke University

Matthew Dietrich, Department of Earth and Environmental Sciences, Vanderbilt University

Shawn Domagal-Goldman, Sciences and Exploration Directorate, NASA Goddard Space Flight Center

Brian Ebel, Center for Water, Earth Science and Technology, University of Colorado Boulder

Erika Hamden, Department of Astronomy and Steward Observatory, University of Arizona

Andrew Hoell, Earth System Research Laboratory, NOAA

Tara Hudiburg, College of Natural Resources, University of Idaho

Matthew Kirwan, Virginia Institute of Marine Science

Erika Marin-Spiotta, Department of Geography, University of Wisconsin–Madison

Brian McDonald, Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder

Richard Moore, NASA Airborne Science Program, NASA Langley Research Center

Maitane Olabarrieta, Coastal and Oceanographic Engineering Department, University of Florida

John Reager, NASA Jet Propulsion Laboratory, California Institute of Technology

Andrew Rollins, Earth System Research Laboratory, NOAA

Yolanda Shea, CLARREO Science Definition Team, NASA Langley Research Center

Jeffrey Snyder, School of Earth, Environment and Society, Bowling Green State University

Jenny Suckale, School of Earth, Energy, and Environmental Sciences, Stanford University

Aaron Wech, Volcano Science Center, USGS

Heather Wright, Volcano Disaster Assistance Program, Cascades Volcano Observatory, USGS

Kelly Wrighton, College of Agricultural Sciences, Colorado State University

“The PECASE is an incredible honor, but really it signifies how fortunate I am to have such an inspiring and creative group of mentors and colleagues from NOAA and beyond,” said award recipient Eric Anderson.

Awardee Lynn Carter said the award recognizes that “my work with radar remote sensing and radar technology development is valuable to the agency and a direction to keep going in the future. Receiving this award is also an inspiring reminder to persevere and to continue to help those coming up in the field achieve their goals as well.”

“On behalf of AGU, I wish to congratulate all those receiving this richly deserved award. The innovation, expertise, and dedication of these early-career scientists to advance human understanding in the Earth and space sciences is both inspiring and uplifting,” said AGU CEO/executive director Chris McEntee. “AGU looks forward to working with this diverse group of researchers as they continue to grow in their careers for years to come.”

Given once within a scientist’s career, the award is meant to help propel innovation in science and technology, elevate public awareness of and appreciation of the importance of science and engineering careers, shed light on the pivotal work of federal scientific agencies, and strengthen the convergent science connections connecting fundamental research and policy goals. Each recipient receives funding from their agency for up to 5 years to advance his or her research. This year’s recipients were honored at a ceremony in Washington, D.C., on 25 July.

—Joshua Speiser (jspeiser@agu.org), Manager of Strategic Communications, AGU

Investing in Science to Improve Climate Risk Management

Fri, 08/16/2019 - 11:03

Climate change caused by past and ongoing emissions from fossil fuel burning poses sizable risks for current and future generations through its impacts on multiple interacting sectors, including, for example, food and water supplies and public health [O’Neill et al., 2017].

The extent of these risks is subject to deep uncertainties and tipping points, suggesting the need for flexible approaches to climate adaptation. One example of a deep uncertainty in our understanding of climate is the degree to which local and regional storm surge intensities are modulated by a warming climate [Lee et al., 2017; Wong et al., 2018].

In climate risk management, these uncertainties often affect estimates of potentially damaging impacts, thus amplifying the importance of the uncertainties [Wong et al., 2017a].

Even with strong mitigation of anthropogenic climate forcing, communities will still need to adapt to impending changes resulting from historical greenhouse gas emissions.Even with strong mitigation of anthropogenic climate forcing, communities will still need to adapt to impending changes resulting from historical greenhouse gas emissions. Successful strategies require the right information, such as observations of relevant environmental indicators, or signposts, to trigger needed changes in the approach, and updated risk assessments that account for new information.

Fundamental Earth science research provides a foundation for supplying this information. Integrating research about regional- and global-scale Earth system processes into adaptation planning can help identify strategies to manage climate risks in the face of the uncertainties to ensure sustainable and resilient communities. We illustrate this point with an example of decision-making to adapt to sea level rise in Norfolk, Va.

Protecting Norfolk: A Case Study

Consider the decision of how high to build a levee to help protect Norfolk, which sits along the Elizabeth River at the south end of the Chesapeake Bay. Suppose that decision-makers seek flood defense systems to limit the chance that by the year 2070, floodwaters will overtop the levee to 1% in a given year, corresponding to an event with a 100-year return period. Planning to meet this target requires projections of sea level rise and storm surge. These projections hinge critically on assumptions about climate policies and the strength of physical feedback mechanisms governing, for example, ice sheet and storm surge dynamics [Wong et al., 2017a].

Fig. 1. Effects of deep uncertainties (about storm surge dependence on global mean temperatures) and positive feedbacks (triggering of rapid West Antarctic melting dynamics) on projected coastal flooding by 2070 modeled for Norfolk, Va. (a) Water height anomalies in 2070 (relative to 2015) plotted against return periods for four different sets of model assumptions. (b) Maximum water height of a flood event with a 100-year return period for each modeled scenario. Changing storm surge distributions are based on changes in global mean temperature. Mean sea level and global mean temperature projections were obtained using the Building blocks for Relevant Ice and Climate Knowledge (BRICK) sea level rise emulator from Wong et al. [2017b]. Storm surge models were calibrated using data from Sewells Point in Norfolk. Land subsidence estimates are from Kopp et al. [2014].According to our modeling, making seemingly reasonable assumptions about future flooding on the basis of recent historical tide gauge records alone could lead planners to suggest a levee height of roughly 2.5 meters (Figure 1, green curve). However, this choice of levee height could result in drastically higher (and arguably unacceptable) flooding risks if some of these assumptions fail. For example, if Earth’s ice sheets respond rapidly and nonlinearly to increased climate forcing (as they have likely done in the past [Wong et al., 2017a] and may be doing now [Joughin et al., 2014]) and if storm surge frequency and/or intensity increase with a warming climate (which may be consistent with existing evidence [Lee et al., 2017]), then the projected probability of floodwaters overtopping a 2.5-meter-tall levee rises to just over 5% per year (Figure 1, pink curve) in this example analysis. In other words, what might have been considered a once-in-a-century flood event would occur approximately every 19 years on average.

An alternative might be to build a levee high enough to defend against the perceived worst-case scenario. Using an example worst-case assumption established by the National Oceanic and Atmospheric Administration in the case of Norfolk might lead to construction of a levee roughly 4 meters tall [Sweet et al., 2017]. This strategy might be logistically infeasible, however, and would likely require very large investments that some might feel could be better spent elsewhere.

How can we manage trade-offs between competing concerns given the deep uncertainties in our knowledge of climate? One approach is to hedge in the short term against immediate and foreseeable risks, then adapt as new information becomes available. By analogy, if a doctor tells you that you have an increased risk of heart disease, it might be prudent to adapt your behavior initially by moderately modifying your diet and exercise habits while leaving open the option to use more intensive approaches, such as prescription medication, if your perceived risk does not decrease sufficiently in the future.

Health risks can be better managed with sustained observations (checkups, blood tests, etc.) and analyses. Similarly, climate risks can be better managed with sustained Earth observation systems and research, so that science can inform decisions. What does this mean for designing, implementing, and resourcing mission-oriented basic science?

For coastal flood risk management, several unknowns can be addressed by analyzing basic Earth science questions: (1) What are the impacts of possible future greenhouse gas emissions trajectories, including on relatively low probability but high-risk events? (2) Will the West Antarctic Ice Sheet (WAIS) collapse, and if so, on what timescale [Joughin et al., 2014]? (3) What would be the resulting contribution of WAIS collapse to local sea level changes? (4) Are there detectable changes in the frequency and severity of storm tides? (5) Are storm tracks changing as a result of climate change? (6) What regions and metropolitan areas are more likely to be affected?

Designing adaptive strategies that can react to new information from Earth science observations can drastically improve future outcomes in the event of potentially damaging flood events.Designing adaptive strategies that can react to new information from Earth science observations can drastically improve future outcomes in the event of potentially damaging flood events [U.S. Army Corps of Engineers, 2014]. Current mitigation measures can be planned with an eye toward flexibility and expandability so that the full suite of appropriate options is available in the future. As an example, while new levees are being built or existing levees heightened, it might also be prudent to build them so they could be widened and further heightened in the future. In the Norfolk example, consider again a levee designed to defend against floods with return periods shorter than 100 years as of 2070 when the levee height—2.5 meters—is based only on linear extrapolation from the historical record (Figure 1, green curve). By comparison, even under relatively conservative model assumptions, considering a consistent storm surge pattern out to 2070 but ignoring the potential for accelerated West Antarctic melting (Figure 1, orange curve), that 2.5-meter levee would protect only against floods with a 46-year average return period, less than half of the target standard.

Integrating disciplines such as Earth science, statistics, and decision analysis into adaptation planning can help identify signposts that can be used to design monitoring systems and trigger potentially needed changes in strategy [Haasnoot et al., 2013; Weatherhead et al., 2018]. A simplified and potentially effective adaptive approach at Sewells Point, near Naval Station Norfolk, might involve the following steps:

First, heighten the levee in stages over the next few decades to maintain a 100-year protection standard against well-characterized risks—say, the nonaccelerated sea level rise scenario in Figure 1 (orange curve)—with enough width built in to increase the height in the future if necessary. Second, plan for transitions between scenarios (e.g., from orange to blue to pink in Figure 1) to avoid being locked into a single approach. And if the projected levee height needed to meet the target protection standard in certain scenarios is more than what might be tolerated on the basis of cost or aesthetic objections, the possibility of using other resiliency measures—elevating houses, property buyouts, or land use changes, for example—should be left open. Third, monitor signposts, such as changes in ice sheet dynamics and trends in regional tide gauge records, for indications that the local flood risk could change. Finally, update risk assessments and mitigation strategies with this new information.

Effective Adaptation Requires Investment

Such adaptive strategies can drastically reduce risks and/or costs [Haasnoot et al., 2013; Yohe, 1991], but they do require sustained investment to realize these benefits. The example outlined above requires investments in sustained Earth observations and analysis aimed at understanding and early detection of climate change impacts. Remote sensing observation platforms provide broad-based benefits [Weatherhead et al., 2018], increasing the economic value of the gathered information. The benefits of such information are regional in the case of storm surge trends and global in relation to ice sheet observations.

Ultimately, the selection of a strategy requires balancing and compromising among diverse stakeholder perspectives and objectives.Finally, various adaptation strategies can be analyzed and compared to shed light on the trade-offs associated with choosing among the strategies (trade-offs related to costs, externalities like property values, and flood hazards, among others). Ultimately, the selection of a strategy requires balancing and compromising among diverse stakeholder perspectives and objectives. Multiobjective decision analysis can help identify strategies that best navigate the often hard trade-offs that arise [Kasprzyk et al., 2013], and careful articulation of objectives and trade-offs helps to improve the transparency of the decision-making process.

This opinion focuses on the issues of sea level rise and flooding affecting one example site. Similar plans would be required to address a wide range of other issues posed by the changing climate, which are likely to become more challenging if mitigation measures are not implemented.

Efforts to defend against climate-related risks benefit from sustained commitments to getting the right science, getting the science right, and getting the science to the decision-makers. Investments in basic Earth science observations and research enhance our ability to identify meaningful signposts for adaptation, to understand the risks associated with tipping points, and to realize the benefits of sound risk management strategies.


We thank Tony Wong, Robert Nicholas, Kelsey Ruckert, Nancy Tuana, and Robert Lempert for their contributions. This work was supported by the Penn State Center for Climate Risk Management. Any opinions, findings, conclusions, and recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the funding entity. Any errors and opinions are those of the authors. All model codes, analysis codes, data, and model output used for analysis are freely available at github.com/vsrikrish/SPSLAM and are distributed under the GNU General Public License. The data sets, software tools, and other resources on this website are provided as is, without warranty of any kind, express or implied. In no event shall the authors or copyright holders be liable for any claim, damages, or other liability in connection with the use of these resources. V.S., R.A., and K.K. conceptualized the commentary and wrote the paper; V.S. wrote the analysis codes. The authors are not aware of any competing interests.

Sinking Wastewater Triggers Deeper, Stronger Earthquakes

Fri, 08/16/2019 - 11:01

The oil and gas industry’s practice of pumping wastewater fluids underground for disposal has been implicated in the dramatic uptick in earthquakes in the central United States. Now a new study has found a correlation between the increasing depth of the earthquakes and the rate at which these fluids descend through Earth’s crust, a finding that could have implications for how such fluids are regulated.

The blue line shows the number of earthquakes in Oklahoma over magnitude 2.5 rising from dozens to hundreds a year in the mid-2000s, after underground wastewater disposal became common practice. The red arrow shows the earthquakes striking deeper over time as wastewater continues to sink into fault systems. Credit: Ryan Pollyea

Over the past decade, earthquakes in the central United States greater than magnitude 3.0 have increased dramatically because of disposal of oil field wastewater into deep geologic formations. Injecting these fluids under pressure can destabilize faults and, in some places, trigger hundreds of induced earthquakes a year over magnitude 3.0, some as large as the magnitude 5.8 quake that struck Pawnee, Okla., in 2016.

Studying the mechanisms by which injected fluids trigger earthquakes has been hampered by a lack of accessible information about the compositions of the wastewater fluids, said Ryan Pollyea, a hydrogeologist at Virginia Polytechnic Institute and State University in Blacksburg and lead author of the new study, published in Nature Communications. “So much of that data is proprietary information, held by the oil and gas companies,” he said.

To assess how the density of the fluids may influence their descent, Pollyea and colleagues turned to a database maintained by the U.S. Geological Survey that includes typical compositions of wastewater fluids. Some of these fluids have very high dissolved salt content, Pollyea said, making the fluids denser and heavier than groundwater found in fault systems.

“We developed computer models showing that oil field wastewater tends to sink when it has a higher dissolved solids concentration—and thus, higher density—than fluids deep within the Earth’s crust,” he said. As this high-density wastewater sinks, it displaces the lower-density fluids that naturally reside in the faults and increases fluid pressure, potentially triggering fault movements.“This [study] provides compelling evidence that high-density wastewater is sinking and causing earthquakes to get deeper within the study areas.”

The team also analyzed earthquake data collected across several Oklahoma counties and found that earthquakes are getting deeper at the same rate high-density wastewater sinks—by about half a kilometer a year. “This provides compelling evidence that high-density wastewater is sinking and causing earthquakes to get deeper within the study areas,” he said.

Earthquake data collected across a broad region of northern Oklahoma and southern Kansas between 2013 and 2018 have demonstrated that the overall earthquake rate has been declining since 2016. Pollyea and colleagues found that although that may be the case overall, the number of earthquakes over magnitude 4.0 is increasing in number. These larger quakes tend to strike at depths below 4 kilometers. “This is likely the result of wastewater sinking and driving up fluid pressure at greater depths,” he said.

Previous studies have not considered the role of wastewater fluid density on fault systems, said Shemin Ge, a hydrogeologist at the University of Colorado Boulder who was not involved in the new study. “In the past, we have generally thought of wastewater as just water. This study adds a new dimension: What happens when the wastewater is denser than water? How does it move through the Earth? It’s a very interesting new perspective.”

The new study also suggests that fluids pumped underground can trigger earthquakes for over a decade after pumping stops, Pollyea said, as the fluids continue to sink to depths beyond 8 kilometers. “Our models also show that high-density oil field wastewater will continue sinking and increasing fluid pressure for over a decade after disposal operations cease,” he said.“We need more cooperation and collaboration from industry if we’re going to understand how these fluids interact with the fault environment.”

Going forward, both Pollyea and Ge would like to see more transparency from oil and gas companies about the contents of wastewater fluids. “The composition of these fluids and other pertinent information should be incorporated into the permitting and regulatory process,” Pollyea said. “If more of that data was available, we could learn a lot more about the mechanisms driving these earthquakes.”

“We need more cooperation and collaboration from industry if we’re going to understand how these fluids interact with the fault environment,” Ge said. “It’s surprising how little we know about [wastewater fluids] and yet they have such a significant impact on huge regions of the country, an impact that this study shows will not immediately go away after they stop injecting.”

—Mary Caperton Morton (@theblondecoyote), Science Writer

2019 Class of AGU Fellows Announced

Thu, 08/15/2019 - 13:58

Each year since 1962, AGU has elected as Fellows members whose visionary leadership and scientific excellence have fundamentally advanced research in their respective fields. This year, 62 members will join the 2019 class of Fellows.

This honor is bestowed on only 0.1% of AGU membership in any given year.AGU Fellows are recognized for their scientific eminence in the Earth and space sciences. Their breadth of interests and the scope of their contributions are remarkable and often groundbreaking. Only 0.1% of AGU membership receives this recognition in any given year.

On behalf of AGU’s Honors and Recognition Committee, our Union Fellows Committee, our section Fellows committees, AGU leaders, and staff, we are immensely proud to present the 2019 class of AGU Fellows.

We appreciate the efforts of everyone who provided support and commitment to AGU’s Honors Program. Our dedicated AGU volunteers gave valuable time and energy as members of selection committees to elect this year’s Fellows. We also thank all the nominators and supporters who made this possible through their dedicated efforts to nominate and recognize their colleagues.

Honor and Celebrate Eminence at Fall Meeting

At this year’s Honors Tribute, to be held Wednesday, 11 December, at Fall Meeting 2019 in San Francisco, Calif., we will celebrate and honor the exceptional achievements, visionary leadership, talents, and dedication of 62 new AGU Fellows.

Please join us in congratulating our 2019 class of AGU Fellows, listed below in alphabetical order.

—Robin Bell, President, AGU; and Mary Anne Holmes (unionfellows@agu.org), Chair, Honors and Recognition Committee, AGU


Zuheir Altamimi, Institut National de l’Information Géographique et Forestière and Institut de Physique du Globe de Paris

Ronald Amundson, University of California, Berkeley

Jonathan Bamber, University of Bristol

Barbara A. Bekins, U.S. Geological Survey

Jayne Belnap, Southwest Biological Science Center, U.S. Geological Survey

Thomas S. Bianchi, University of Florida

Jean Braun, GFZ Helmholtz Centre Potsdam, and Institute of Earth and Environmental Sciences, University of Potsdam

Ximing Cai, University of Illinois at Urbana-Champaign

Ken Carslaw, University of Leeds

Benjamin F. Chao, Institute of Earth Sciences, Academia Sinica

Patrick Cordier, Université de Lille

Rosanne D’Arrigo, Lamont-Doherty Earth Observatory of Columbia University

Eric A. Davidson, Appalachian Laboratory, University of Maryland Center for Environmental Science

Gert J. de Lange, Utrecht University

Andrew Dessler, Texas A&M University

Michele K. Dougherty, Imperial College London

Joseph R. Dwyer, University of New Hampshire

James Farquhar, University of Maryland, College Park

Mei-Ching Fok, NASA Goddard Space Flight Center

Piers Forster, University of Leeds

Christian France-Lanord, CNRS Université de Lorraine

Antoinette B. Galvin, University of New Hampshire

Peter R. Gent, National Center for Atmospheric Research

Taras Gerya, ETH Zurich

Dennis Hansell, University of Miami

Ruth A. Harris , Earthquake Science Center, U.S. Geological Survey

Robert M. Hazen, Carnegie Institution for Science

Kosuke Heki, Hokkaido University

Karen Heywood, University of East Anglia

Russell Howard, United States Naval Research Laboratory

Alan G. Jones, Complete MT Solutions Inc. and Dublin Institute for Advanced Studies

Kurt O. Konhauser, University of Alberta

Sonia Kreidenweis, Colorado State University

Kitack Lee, Pohang University of Science and Technology

Zheng-Xiang Li, Curtin University

Jean Lynch-Stieglitz, Georgia Institute of Technology

Kuo-Fong Ma, National Central University and Academia Sinica

Reed Maxwell, Colorado School of Mines

John W. Meriwether, Clemson University (Emeritus) and New Jersey Institute of Technology

Son V. Nghiem, Jet Propulsion Laboratory, California Institute of Technology

Yaoling Niu, Durham University

Thomas H. Painter, Joint Institute for Regional Earth System Science and Technology, University of California, Los Angeles

Beth Parker, University of Guelph

Ann Pearson, Harvard University

Graham Pearson, University of Alberta

Lorenzo M. Polvani, Columbia University in the City of New York

Peter Reiners, University of Arizona

Yair Rosenthal, Rutgers University–New Brunswick

Osvaldo Sala, Arizona State University

Edward (Ted) Schuur, Northern Arizona University

Sybil Seitzinger, University of Victoria

Toshihiko Shimamoto, Institute of Geology, China Earthquake Administration

Adam Showman, University of Arizona

Alexander V. Sobolev, Institut des Sciences de la Terre, Université Grenoble Alpes, and Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences

Carl Steefel, Lawrence Berkeley National Laboratory

John Suppe, University of Houston

Karl E. Taylor, Lawrence Livermore National Laboratory

Meenakshi Wadhwa, Arizona State University

Michael Walter, Carnegie Institution for Science

John Wettlaufer, Yale University and Nordic Institute for Theoretical Physics

Chunmiao Zheng, Southern University of Science and Technology, Shenzhen

Tong Zhu, Peking University

Smokey Bear, Fake Volcanoes, and Other Things We’re Reading

Thu, 08/15/2019 - 12:15

Happy Birthday, Smokey! As summer camping trips end and fall fire seasons begin, it’s a good time to remember that only YOU (and I) can prevent wildfires. —Caryl-Sue, Managing Editor


Girl Scouts Emphasize STEM Education

At a briefing on Capitol Hill, Sydne Jenkins, 16, spoke about the benefits and opportunities provided by Girl Scout STEM programs. Credit: Randy Showstack

Girls just wanna have space science badges! That’s how the song goes, right? I’m so excited that @girlscouts can (officially) be explorers, adventurers, investigators, researchers, and experts in space sciences! —Kimberly Cartier, Staff Writer


The Cows That Could Help Fight Climate Change. Through no fault of their own, cattle and other livestock contribute substantially to anthropogenic greenhouse gas emissions—14.5% by one prominent estimate!—mainly in the form of methane. This is an interesting read about a variety of ways researchers are looking to decrease cattle carbon emissions, including an effort to vaccinate the animals against methane-producing gut microbes. #CattleCounteringClimateChange (Of course, another route to the same end is for us omnivores—myself included—to cut back on our beef consumption.) —Timothy Oleson, Science Editor


An Italian Volcano Turned Out to Be a Fraud. “It might sound improbable that an impostor ended up sneaking into the volcanological equivalent of the Library of Alexandria.” Janine Krippner is one of the keepers of the Smithsonian Institution’s volcano registry, and this is the story about how she discovered a fake. —Heather Goss, Editor in Chief


The Most Boring Chemical Element (paywalled)

This is one of our favorite versions of the periodic table, illustrating each element’s natural occurrence or familiar human use. Click image for larger version. Credit: Keith Enevoldsen, CC BY-SA 4.0

What is the most boring element? This Nature Chemistry comment will keep you on your toes in its takedown of the periodic table. —Jenessa Duncombe, Staff Writer


Seeking Stardust in the Snow. Fallen stardust lets us relive “local” stars going supernova over the past 20 million years. I think we need a video of that! —Liz Castenson, Editorial and Production Coordinator


Is Grass-Fed Beef Really Better for the Planet? Here’s the Science. “For the environmentally minded carnivore, meat poses a culinary conundrum.” The article doesn’t provide all the answers, but it gave me—an omnivore and a self-confessed foodie—some information to chew on. —Faith Ishii, Production Manager


Expect a Busier-Than-Normal Hurricane Season, NOAA Says. Following one of the hottest Julys on record and flood-inducing rainstorms, the United States and other Atlantic nations now face an increased possibility of a highly active hurricane season. El Niño has dissipated, and the National Oceanic and Atmospheric Administration recently put out a revised forecast. —Tshawna Byerly, Copy Editor

Microbes Spotted on Blades of Ice High in the Andes

Thu, 08/15/2019 - 12:14

The concept of blades of ice sculpted by the Sun sounds otherworldly, and it is. Such blades have been detected on Pluto and are believed to exist on Jupiter’s moon Europa. But they also form high in the Andes mountains of South America.

Now researchers have spotted microbial life on the earthly versions of these icy spires. This discovery has astrobiological implications, the science team behind it suggests: Ice might provide a toehold for life in the solar system.

“What’s This?”

Steve Schmidt, a microbial ecologist at the University of Colorado Boulder, and his colleagues didn’t set out to study penitentes, which form when sunlight strikes patches of snow, causing it to sublimate. (The features’ Spanish name refers to their resemblance to white-robed monks doing penance.) In March 2016, Schmidt and his team were hiking up Llullaillaco, a dormant stratovolcano on the border between Chile and Argentina, and paused to rest at an elevation of roughly 5,300 meters near a field of penitentes. Schmidt remembers a team member seeing pinkish red smudges on roughly meter tall penitentes and asking, “What’s this?”

The smudges looked biological, but they were also rare: Only about 0.1% of the penitentes in the field had any coloration, Schmidt said. “You could easily walk by and not see it.”

The scientists weren’t planning to sample the penitentes, but seeing the unusual color piqued their interest. They retrieved sterile spoons from their packs and, over the course of a few hours, collected five samples of the pinkish red ice from the sides of several penitentes and the “wells” between them.

Snow Algae

Back in the laboratory at the University of Colorado Boulder, the researchers analyzed the samples’ DNA.

By comparing the samples’ DNA sequences with sequences from known organisms, the scientists found a perfect match with strains of the snow algae Chlamydomonas nivalis taken from Mount Kilimanjaro, the Swiss Alps, and Antarctica. But not all of the DNA from the penitentes matched Chlamydomonas nivalis—some probably came from previously unknown species of snow algae belonging to another genus, Chloromonas, and perhaps even other unknown genera, the team concluded.

“I think it’s the first discovery of microbes on penitentes,” said Schmidt. “Nobody ever thought to look for them.” These results were published in June in Arctic, Antarctic, and Alpine Research.

Sunscreen for Algae

“It’s sort of a sunscreen for the algae.”The red coloration of the snow algae is more than just eye-catching—it likely helps protect the algae from the intense sunlight that blasts the upper reaches of Llullaillaco, said Schmidt. Red-hued pigments like carotenoids within red varieties of snow algae—such as Chlamydomonas nivalis—dissipate the Sun’s energy by radiating away heat.

“It’s sort of a sunscreen for the algae,” said Schmidt.

By reemitting the Sun’s radiation, snow algae also warm up their surroundings and melt the ice around them to create liquid water.

“You have this oasis where there’s abundant life,” said Schmidt.

John Moores, a planetary scientist at York University in Toronto, Canada, not involved in the research, agrees. “The environment within the small-scale nooks and crannies of those exposures could be more clement from an astrobiological perspective than the surface more broadly.”

Snow algae might also play a role in the formation of Llullaillaco’s penitentes, researchers suggest. Previous results have shown that snow algae can have the same effect as dusty debris on a snowy surface, absorbing more sunlight than bare snow alone.

By kick-starting sublimation, snow algae may contribute to the formation of penitentes, Schmidt and his team hypothesized. An important next step will be determining whether snow algae are present during different phases of penitente growth, the researchers concluded.

Limits of Life

Earthly penitentes harbor life, Schmidt and his team showed, but what about extraterrestrial penitentes? These features have been spotted on Pluto, where they’re composed of nitrogen and methane rather than water, and are inferred to exist on Jupiter’s moon Europa.

To help answer that question, Schmidt and his colleagues want to understand the environmental limits of microbes like snow algae. Penitentes can be found all the way up to the top of Llullaillaco, the second-highest active volcano in the world (6,739 meters). Conditions get progressively harsher near the summit, and Schmidt and his team want to return to South America to look for microbes at a range of elevations.

That’ll help answer just how much ultraviolet radiation and aridity life can handle, said Schmidt. “At what elevation can you not find them?”

—Katherine Kornei (@katherinekornei), Freelance Science Journalist

Lawsuit Challenges Trump Administration’s Emissions Rollbacks

Wed, 08/14/2019 - 21:25

On 13 August, a coalition of states and cities sued the Trump administration over new regulations on power plants that would weaken emissions restrictions proposed by the Obama administration.

The 22 states and seven cities filing suit assert that the Affordable Clean Energy (ACE) Rule put in place by the Trump administration fails to take the necessary steps to reduce greenhouse gas emissions. They argue that under the Clean Air Act, the Environmental Protection Agency (EPA) is responsible for setting limits on greenhouse gases.

The ACE Rule has much weaker regulations on national carbon emissions than the Obama administration’s Clean Power Plan. Under the ACE Rule, there is no emissions cap, individual states decide whether to lower emissions, and the rule focuses on improvements to increase efficiency at coal plants rather than transitioning to renewables or investing in carbon capture.

The new rule will decrease carbon dioxide emissions by 0.7% by 2030, according to an EPA assessment noted in a statement from New York attorney general Letitia James. The Obama-era Clean Power Plan would have reduced carbon emissions by 19%.

The new rule “is a draconian backwards step, 180 degrees in the opposite direction to where science indicates we must go.”Climate scientist Peter Kalmus at NASA’s Jet Propulsion Laboratory called the rule “obviously a protection for the fossil fuel industry” and voiced support for the lawsuit. (Kalmus did not speak on behalf of his employer.)

The ACE Rule “is a draconian, backwards step, 180 degrees in the opposite direction to where science indicates we must go,” Kalmus told Eos.

Peter de Menocal, the Dean of Science at Columbia University, also spoke in favor of the lawsuit, because aggressive emissions cuts will be needed to stay below the target warming threshold of 1.5°–2°C.

“I am hoping, praying actually, that the states prevail in their challenge of this proposed rollback,” de Menocal told Eos. “It is vitally important that we urgently and significantly accelerate emissions reductions.”

EPA Responsibility

EPA administrator Andrew Wheeler told the New York Times in June that he stands behind the new plan. “We’re on the right side of history,” he said. “It’s Congress’s role to draft statutes, not the regulatory agencies.”

Under the Clean Air Act, the EPA must use the “best system of emissions reduction” to limit greenhouse gas emissions. The EPA regulates air pollutants that risk human health, and a case heard by the Supreme Court in 2006 affirmed that carbon dioxide is included as an air pollutant.

Julie McNamara, senior energy analyst at the Union of Concerned Scientists, told Eos that limiting greenhouse gas emissions falls well within the purview of the EPA, whose mission is to protect human health and the environment. She called for the agency to take action, as human health and safety are increasingly at risk from climate change.

“It’s here, it’s happening,” McNamara said of climate change. She mentioned the recent record-breaking heat waves that swept the globe this summer.

“Right when communities across the country are reeling from the effects and its impacts are worsening and looming on the horizon,” she said, “we have our Environmental Protection Agency throwing up its hands.”

Karl R. Rábago, a professor of law at the Elisabeth Haub School of Law and executive director of the Pace Energy and Climate Center, told Eos that the lawsuit is a positive step forward.

“The administration seems bent on allowing any state to become a pollution haven,” Rábago said. “Since the current EPA won’t follow science or the law, the courts are the right next step.”

Questions on the Future of Coal

The lawsuit comes at a time when the future of coal investment is under fire. Firms in the United States have started to divest from coal projects, and there are calls for the American company AGI to rescind insurance coverage for a prominent Australian coal mine.

The ACE Rule keeps the door open for future investments of coal, which Wheeler acknowledged when the rule went into effect in June 2019.

“I don’t know who is going to invest in a new coal-fired power plant, but we’re leveling the playing field to allow that investment to occur,” said Wheeler, as reported in the New York Times.

McNamara said that future investments would be better spent replacing aging coal plants with renewables, which can be cheaper for utilities and customers alike.

“This rule would drive an investment in coal plants that are on their last legs,” she said. “That’s not building towards the future, that’s trying to hang on to a rapidly eroding past.”

Kalmus voiced concerns about human health effects of continued coal use. “There is no such thing as ‘clean coal,’” he said. “Even setting aside its climate impact, coal is by far the deadliest way to produce electricity due to its public health impact.”

Fate of Lawsuit Unclear

The ruling could have far-reaching effects on the extent that federal regulations can direct energy policy.The lawsuit, filed in the U.S. Court of Appeals in the District of Columbia Circuit, could possibly be heard before the Supreme Court. The ruling could have far-reaching effects on the extent that federal regulations can direct energy policy. The Supreme Court struck down the Clean Power Plan in 2016.

New York attorney general Letitia James (D) said in a statement that the coalition bringing the lawsuit “will fight back against this unlawful, do-nothing rule in order to protect our future from catastrophic climate change.” A group of ten public interest groups submitted a separate petition against the ACE rule on 14 August.

EPA spokesman Michael Abboud addressed the pending lawsuit in a statement reported by the Washington Post: “EPA worked diligently to ensure we produced a solid rule, that we believe will be upheld in the courts, unlike the previous Administration’s Clean Power Plan.”

—Jenessa Duncombe (@jrdscience), News Writing and Production Fellow

Scientists and Planners Face Challenge of Rising Seas

Wed, 08/14/2019 - 12:08

Coastlines across the globe are already experiencing the impacts of sea level rise. Many threatened areas have begun planning for, adapting to, and mitigating the effects of current and future sea level changes—and bearing the significant associated costs. Despite the advanced stages of preparing for sea level rise in some locations, planners often lack the comprehensive sea level information needed to make fully informed decisions. This lack of information results partly from unresolved scientific problems still under investigation and in part from the difficulty of translating science into something that is useful and actionable for decision-makers.

Much of the focus was on information flows from scientists to end users, with the goal of identifying ways to streamline and improve this process.To begin addressing these challenges, 50 members of NASA’s Sea Level Change Team (N-SLCT) met last March with a diverse set of stakeholders—35 in all—representing state and local governments as part of N-SLCT’s annual science team meeting. The meeting was held in Annapolis, Md., at the Chesapeake Bay Foundation’s Philip Merrill Environmental Center. Annapolis, a U.S. coastal city, is already feeling the effects of rising seas, including dramatic increases in high-tide flooding in recent years.

The first day of the 3-day workshop featured stakeholders offering accounts of the real-world effects of sea level rise. They described the planning processes and the scientific information that are the foundation of their plans. Much of the focus was on information flows from scientists to end users, with the goal of identifying ways to streamline and improve this process.

Scientists and stakeholders also expressed interest in identifying gaps in available scientific information. N-SLCT sought answers to more specific questions as well: How is NASA science being used for coastal planning, and who is using it? How can NASA best provide useful information as these planning efforts continue?

The science team members provided updates on the significant progress in understanding the roles that ocean, ice, and land play in coastal sea level rise.These questions and the discussions that took place on the first day of the workshop were used to inform the work of N-SLCT over the remaining 2 days of the meeting. N-SLCT focuses primarily on improving understanding of present and future regional relative sea level rise. Tackling this problem requires an interdisciplinary approach, and the team’s expertise covers the broad range of factors contributing to sea level change.

The science team members provided updates on the latest scientific results, including significant progress in understanding the roles that ocean, ice, and land play in coastal sea level rise.

On the last day of the meeting, the group considered the future direction of N-SLCT. Participants identified several “team products” that will be developed over the coming months, including a set of regional sea level hindcasts and projections covering a range of timescales. They also identified the importance of further stakeholder engagement to inform future team activities; the Annapolis workshop was viewed as a first step in this direction. Further information about the meeting and team activities can be found at the N-SLCT web portal.

The research presented at this meeting was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA.

Author Information

B. D. Hamlington (bhamling@jpl.nasa.gov), C. Boening, and H. P. Brennan, Jet Propulsion Laboratory, California Institute of Technology, Pasadena

When Does Weather Become Climate?

Wed, 08/14/2019 - 12:07

Individuals and political organizations alike often define “climate” as climate scientist John Kennedy did on Twitter: “Practically speaking: weather’s how you choose an outfit, climate’s how you choose your wardrobe.” Meanwhile, the scientific literature rarely defines climate more specifically than as the “statistics of weather.” Such vague definitions may impede policy making on climate change because politics is best at tackling well-defined problems. Without a clear definition of what climate is, local and global perspectives on climate change contrast with each other, presenting a problem in multilateral negotiations [Miller, 2004] and reducing the relevance of discussions on climate and its changes to local communities [Hulme, 2016]. The lack of a robust definition may even prevent agreement in discussions on climate change policies.

The concepts of climate and weather developed over centuries in various cultural and geographic settings [Hulme, 2016]. The resulting plurality of views implies that communication about climate involves cultural and linguistic translations [Rudiak-Gould, 2012]. We can observe such translations (or their failure) every day in the media’s reception of climate science literature and in how climate scientists adopt results from colleagues with different backgrounds.

A Classification of Convenience

Scientists’ definitions of climate have evolved with their understanding of the world.Scientists’ definitions of climate have evolved with their understanding of the world [Heymann and Achermann, 2018]. Possibly the most common current definition is that from the Intergovernmental Panel on Climate Change’s (IPCC) Fifth Assessment Report, which distinguishes between “climate in a narrow sense…as the average weather…over a period of time ranging from months to…millions of years” and “climate in a wider sense” as “the state…of the climate system.” Both senses are valid descriptions of climate. They are instances of a common template, that is, a common concept of climate. Other definitions differ from the IPCC’s in the parts of the climate system and the methods that they consider [see Conradie, 2015]. Werndl [2015] asserts, “How to define climate and climate change is nontrivial and contentious.”

The idea of climate is a classification of convenience. It is a tool that helps us deal with our ever-changing surroundings [Hulme, 2016] in colloquial, scientific, philosophical, and political contexts. Then, climate is an inherently subjective concept [Lucarini, 2002]. Any societal group, any person, any business, and any academic may have a distinct view on climate. This view depends on the specific application, the regional and temporal focus, and the person’s or group’s unique experiences. Any societal actor’s view is one of a myriad of possible instances of climate. The scientific literature on climate largely imposes a North American and European perspective (compare Rudiak-Gould [2012]). But no single instance can define climate; rather, we need a template definition for the concept.

If we accept that the view of climate as the “statistics of weather” is unclear, we may clarify this view using a more precise definition of our terms. What do these statistics of weather usually represent? What constitutes the “weather” whose statistics we want to consider? That is, we have to spell out what is climate and what is weather. Indeed, the transition between weather and climate is ambiguous, with gaps between these concepts in terms of their coverage and their temporal delineation.

Earth’s climate system includes its atmosphere, hydrosphere, cryosphere, biosphere, and lithosphere. Besides statistics, descriptions of the climate system’s behavior may employ thermodynamics and fluid dynamics, along with chemistry, electromagnetism, rheology, and plasma physics.

The idea of climate allows us to compare parts of the system in different locations, at different times, and with different sources of data. We can consider spatial scales ranging from local to global at the surface, in the upper atmosphere, or in the ocean. And we may classify climate over time periods of millions of years, three well-observed decades, or even shorter periods to highlight short-term variations. Each data point in studying climate is an uncertain, imperfect estimate. Only by considering uncertainty can we make practical use of models of climate, which are uncertain by construction.

We speak of climate change when, according to a certain criterion, we detect differences between statistics of weather for different instances of interest, such as different time periods. Conversely, “climate variability” refers to variations within the reference period for one instance. Even a gradual change of the period of interest leads to another instance of climate. Timescales of climate depend on the physical properties of the system and differ between considered systems. That is, the climate system of another celestial body has different properties than Earth’s climate system. The shortest climate timescale that signifies the transition between weather and climate has to allow defining statistics.

If these are the simplified dimensions and components of what we commonly consider climate, what defines the weather whose statistics produce the climate? And if the smallest climate timescale on Earth is monthly, what are the timescales of this weather?

States of an Atmosphere

Weather is more tangible than climate; we experience it on a day-to-day basis, and we can point to it [Hulme, 2016]. Our perceptions of weather may extend to phenomena beyond the atmosphere. If I am on a boat, wave height is a relevant part of my weather observations. But is desert dust collecting on your car part of weather? Is the transport of industrial emissions weather? Do you perceive the flooding of a field as part of weather?

The American Meteorological Society defines weather as the “state of the atmosphere” at a specific time and emphasizes the minutes-to-days scale of its variations and how these variations influence life or a celestial body.The American Meteorological Society defines weather as the “state of the atmosphere” at a specific time and emphasizes the minutes-to-days scale of its variations and how these variations influence life or a celestial body. The state of a system describes the system in all its parts of interest. Thus, weather completely describes the atmosphere in the sense that the concept of weather encompasses everything needed for a description.

Weather service forecast models distinguish between external (prescribed) properties and internal (predicted) properties. External properties are slowly varying aspects like land use and the surface temperature of the ice-free ocean that provide boundary conditions for the model run. Internal properties are generally fast-changing variables, such as the properties of snow on the surface or the land surface temperature, that directly influence or are influenced by local weather; these internal model variables may be external to the atmosphere.

External properties are necessary to describe the state of the atmosphere because they are part of weather. If climate is the “statistics of weather,” one cannot restrict weather to the atmosphere but must allow weather to extend beyond the atmosphere. For example, the biosphere, cryosphere, and hydrosphere all influence the atmosphere through fluxes of energy and moisture.

If weather on Earth takes place over minutes to days and the shortest climate timescale is monthly, we need a conceptual definition of the transition between weather and climate. The IPCC separates climate variability from the scales of “individual weather events.” This view originates in the classical scale diagrams of meteorology, which plot typical spatial scales against typical temporal scales [e.g., Orlanski, 1975].

Using this view, we can take the transition as the scale at which the predictability of weather reaches its limit [e.g., Lovejoy, 2013; E. N. Lorenz, unpublished manuscript]. In this view, the length of time over which the initial conditions dominate limits the timescales of weather. Beyond this time limit, the sum of our experiences and the resulting expectation of the typical weather describe the system more reliably than a deterministic forecast starting from our experience of the current state of the system.

Evolving Concepts

Acknowledging the inherent subjectivity in current definitions of climate may pave the way to a less contentious definition.Above I tried to clarify the temporal transition between weather and climate and to highlight which parts of a planetary system weather and climate describe. This does not fully remove the ambiguity of the classical “climate is the statistics of weather” definition. Contrasts between local, regional, and global instances of climate, its change, and its impacts [Clark, 1985] likely will become even more important with the emergence of plans for climate engineering applications. These applications require even more that discussions are specific about the climate instances of interest. Acknowledging the inherent subjectivity in current definitions of climate may pave the way to a less contentious definition.

Then again, maybe it is not possible to conclusively delineate weather and climate—at least their temporal separations and terminological dependence. The differing origins of the terms may prevent such a distinction [e.g., Edwards, 2010]. If this is the case, then there may always be the traditional term “weather” and an evolving understanding of what climate is. The colloquial view would contrast subjective expectations and experiences, whereas the Earth sciences would use weather as the concept of meteorology and climate as a description of the interplay between the various Earth system components.

However one applies the term “climate,” it was, is, and will be an evolving concept [Heymann and Achermann, 2018]. It grows as our understanding of the Earth system and of the factors influencing it and its processes—including weather—grows larger.


Comments by anonymous colleagues helped to improve the manuscript. I want to thank the referee of this article and the four anonymous referees of an earlier version as well as the editors for their valuable comments and their support of this article.

Groundwater Drawn Downward After Kumamoto Quake

Wed, 08/14/2019 - 11:30

Major earthquakes are known to affect surface water and groundwater systems; for instance, by altering spring locations, making streams disappear, or causing groundwater levels to drop temporarily or permanently. The study by Hosono et al. [2019] is unique because it provides a rare set of high frequency observations of groundwater and surface water levels before, during, and after a large earthquake.

These data reveal that a large volume of water has disappeared through crustal ruptures formed during the quake, as shown in the diagram above. Not only does this reduce water availability in the region for a whole year but it also causes surface water and shallow groundwater to mix with deeper groundwater with possible long-term negative consequences for groundwater quality.

Citation: Hosono, T., Yamada, C., Shibata, T., Tawara, Y., Wang, C.‐Y., Manga, M., et al. [2019]. Coseismic groundwater drawdown along crustal ruptures during the 2016 Mw 7.0 Kumamoto earthquake. Water Resources Research, 55. https://doi.org/10.1029/2019WR024871

—Marc F. P. Bierkens, Editor, Water Resources Research

Past Climate Sensitivity Not Always Key to the Future

Tue, 08/13/2019 - 11:19

Earth’s equilibrium climate sensitivity—a measure of how much the global average surface temperature will rise in response to a doubling of greenhouse gases in the atmosphere—is a key metric that is widely used in economic and policy assessments of global warming. In a 2013 report, the Intergovernmental Panel on Climate Change estimated that climate sensitivity is likely between 1.5°C and 4.5°C.

In numerous studies, scientists have attempted to refine estimates of this metric by characterizing climate sensitivity from the geological record during Earth’s recent past. Such research, however, has been limited by the fact that during the past 5 million years, carbon dioxide concentrations have not exceeded 560 parts per million by volume (ppmv), a level that is lower than what is projected in many scenarios representing the end of the 21st century.

To develop more relevant climate sensitivity estimates, researchers have begun investigating intervals of time more than 5 million years ago when Earth’s atmospheric carbon dioxide concentrations exceeded 1,000 ppmv. But because factors other than carbon dioxide—such as the brightness of the Sun and the configuration of the continents—can affect climate over such long timescales, it is unclear how applicable the results of these recent investigations are for forecasting Earth’s future.

In a new study, Farnsworth et al. try to more fully explore the planet’s climate sensitivity over geologic timescales by utilizing an ensemble of 19 climate model simulations to examine Earth between about 150 million and 35 million years ago. In the coupled ocean-atmosphere-vegetation simulations, the researchers varied Earth’s paleogeography and the Sun’s brightness as appropriate for each geologic interval from the Early Cretaceous to the late Eocene and incorporated atmospheric carbon dioxide concentrations set at double (560 ppmv) and quadruple (1,120 ppmv) the preindustrial level.

The results suggested that climate sensitivity during this time frame ranged from approximately 3.5°C to 5.5°C. The authors attribute the observed variation to a combination of factors, including the gradually increasing brightness of the Sun as well as changes in the arrangement of the continents, which in turn influenced ocean circulation and, because of differences in ocean surface area, the planet’s albedo.

The findings indicate that over long timescales, climate sensitivity is strongly correlated to Earth’s continental configuration, the Sun’s strength, and the background carbon dioxide concentration. This research suggests that within the context of the past 150 million years, the modern estimate of climate sensitivity is relatively low and that, ultimately, Earth’s past climate sensitivity may not provide a perfect analogue for potential future conditions. (Geophysical Research Letters, https://doi.org/10.1029/2019GL083574, 2019)

Earthquakes Shake Up Groundwater Systems

Tue, 08/13/2019 - 11:18

After an earthquake, regional stream flows will sometimes increase because of an influx of groundwater being released from aquifers. This phenomenon is well documented, but the details of the underlying mechanisms remain somewhat mysterious.

A new study looking at the effect of the 2011 Tohoku earthquake in Japan on groundwater systems in China is shedding some light on how Earth’s subsurface can be affected by large earthquakes.A new study looking at the effect of the 2011 Tohoku earthquake in Japan on groundwater systems in China is shedding some light on how Earth’s subsurface can be affected by large earthquakes.

Groundwater systems often comprise layers of permeable rock called aquifers separated by low-permeability layers called aquitards. Previous studies have analyzed the effects of earthquakes on either aquifers or aquitards, but to date, nobody has quantified the effects of earthquakes on both aquifers and aquitards in the same groundwater system, said Zheming Shi, a hydrogeologist at the China University of Geosciences in Beijing and an author of a new study published in May in Water Resources Research.

“The commonly used tidal response models can only identify either aquifer or aquitard permeability, not both at the same time,” Shi said.

Shi and colleagues took a different approach, combining a traditional tidal response model with an analysis of barometric pressure changes detected in a 2,600-meter-deep well near the Shunyi-Qianmen-Liangxiang fault zone, one of the largest fault systems in Beijing.

Scientists have been monitoring subsurface changes in this well—drilled into an aquifer in porous limestone that is capped by layers of impermeable mudstone, sandstone, and andesite—for decades as part of the country’s extensive earthquake monitoring program. By comparing barometric pressures recorded 4 months before the 11 March 2011 Tohoku quake with data collected up to a year after the event, they found that the earthquake boosted the permeability of the aquifer by a factor of 6, whereas the permeability of the aquitard doubled.

“As far as I know, this is the first time that changes in both an aquifer and an accompanying aquitard have been quantified after an earthquake,” said Michael Manga, a planetary scientist at the University of California, Berkeley, who was not involved in the new study but who coauthored a commentary about the study’s findings in June in Water Resources Research along with Steve Ingebritsen, a hydrologist with the U.S. Geological Survey. “Permeability is not usually thought of as a quantity that can change over time.”

“Permeability is not usually thought of as a quantity that can change over time,” Manga said. “When you drill a well, you measure the rate of flow and then that’s the number you use” to describe the productivity of that well.

But during an earthquake, subsurface pressure changes, and new fracture networks and shifting gases and fluids can open new pathways for groundwater movement. The new study also demonstrates that these subsurface shifts are not permanent: As the area settled after the Tohoku event, detectable changes in the well returned to preseismic levels in about 4 months, Shi and his colleagues wrote.

“This is a very clever study that’s adding a lot to this discussion of how permeability can change in space and time,” Ingebritsen said. “I think there’s growing interest in this idea that permeability is a mutable property. I’d like to see more of these kinds of studies done in other wells in other geologic settings.”

The work may also have implications for groundwater quality after an earthquake, Shi said. Increases in the aquitard’s permeability may allow pollutants to find their way into groundwater supplies.

“The aquitard is a good indicator of the aquifer’s vulnerability to pollution,” Shi said. “If an earthquake causes changes in permeability in the aquitard, groundwater may move upward or downward, thus increasing the risk of groundwater contamination.”

—Mary Caperton Morton (@theblondecoyote), Science Writer

Moon Sheds Light on Early Solar Spin

Tue, 08/13/2019 - 11:15

During its first billion years of life, the Sun may have been a relatively slowly rotating star, a discovery that may have implications for understanding why life was able to flourish on Earth, as well as increasing understanding of our nearest stellar neighbor.

The faster the Sun rotates, the more lightweight material like potassium and sodium it removes from the surface of Earth and the Moon. Measuring these particles in lunar rocks helped scientists determine how fast the early Sun rotated. Credit: NASA GSFC/Jay Friedlander

New research suggests that in the first billion years after it formed, the Sun’s slow rotation could have blasted bombs of charged particles toward Earth and its companion, the Moon, as frequently as every other day. These particles may have led to atmospheric changes that allowed life a chance to gain a foothold.

When clouds of gas and dust collapse to form stars, they start off with a spin imparted by their natal conditions. They slow down over time, making it difficult to determine the speed they were born with.

“Because the Moon had basically no atmosphere for most of its past…it does a really good job of recording history on the surface.”To find that initial solar spin and its related activity levels, a team of scientists turned their eyes to the Moon.

“Because the Moon had basically no atmosphere for most of its past…it does a really good job of recording history on the surface,” said Prabal Saxena, a researcher at the NASA Goddard Space Flight Center in Maryland. Saxena led a team that studied lunar samples to understand how the Sun behaved in its early life. The results were published in the Astrophysical Journal Letters.

From the Moon to the Sun

The Sun blasts charged particles at orbiting planets every day in the form of the solar wind. Occasionally, it ejects large collections of charged plasma known coronal mass ejections (CMEs). Earth’s atmosphere and magnetic field shield the planet, although some of the radiation still makes it through. But the Moon, with its wispy atmosphere and negligible magnetic field, takes the hits directly on its surface. CMEs have been recorded over the Moon’s 4.5-billion-year lifetime, just short of the Sun’s 4.8 billion years.

As a star rotates, its magnetic field can get twisted up, releasing CMEs from its surface. “The more active the star is, the stronger the wind and the stronger the magnetic field of the star will be,” said Louis Amard of the University of Exeter. Amard, who studies the relationship of a star’s rotation and activity, was not part of the new research.

When the charged particles reach the lunar surface, they bathe the regolith with protons and electrons, changing the chemistry and isotopic signatures of the grains on an elemental scale.

“We can gain a chemical signature of the solar wind at that particular point in time,” said Katherine Joy of the University of Manchester, who was not part of the new study. It can also record the influx of galactic cosmic rays, though to a smaller degree.

“The Moon’s surface could potentially preserve an archive of solar and wider galactic processes.”“The Moon’s surface could potentially preserve an archive of solar and wider galactic processes,” Joy said.

By studying potassium and sodium in lunar rocks, Saxena and his colleagues determined that in the first half a billion years of their lifetime, the Earth-Moon system was likely hit by an average of one CME every 2 days. The connection to stellar rotation led researchers to conclude that the Sun was likely a relatively slow rotator, though it still spun faster than it does today.

On Earth, those ejections would have lit up the sky with auroras, perhaps as far south as the equator, Saxena said. He said that other independent research has suggested that the rate of CMEs hitting Earth’s atmosphere could have led to changes in chemistry that produced some of the fundamental building blocks for life.

The new data rely on rocks taken from the surface of the Moon, but Joy said that deeper lunar samples could help reveal changes over time by allowing researchers to study lunar rocks that were covered by debris. These rocks would preserve their early chemical signatures.

“What we’d really like to do is access ancient processes,” Joy said. She hopes that future lunar missions might help make that possible. “We need to drill down deep in the moon so we can access those records,” she said.

—Nola Taylor Redd (@NolaTRedd), Freelance Science Journalist

Curiosity Monitors Rare Global Dust Storm From Mars’s Surface

Mon, 08/12/2019 - 11:30

Planet-encircling dust events (here “global dust storms”, or GDS) are quasi-regular but quite rare events on Mars, where large amounts of dust, lifted from the planet’s surface by winds, become omnipresent in the atmosphere and wrap the whole planet in a dusty haze for some months.

Such events are readily observed with ground-based telescopes and satellites in Martian orbit. However, meteorological in-situ observations of such storms that ground truth data, such as these presented by Viúdez-Moreiras et al. [2019] are exceedingly rare due to the small number of meteorological stations on the surface of Mars.

Previously, only Viking landers had measured meteorological parameters (such as temperature, pressure, wind, and radiation) on the surface during such an event in the 1970s. Spirit and Opportunity, the Mars Exploration Rovers, witnessed a GDS in 2007 with their cameras, without meteorological equipment. Last year, Curiosity’s Rover Environmental Monitoring Station (REMS) seized the opportunity to monitor the impact of a GDS on the atmosphere from a unique vantage point.

Observations by the landers and rovers from different locations at the surface give interesting insight into the local meteorology and the effect of a global dust storm in a variety of regions. This paper is part of a special issue in JGR: Planets on Studies of the 2018/Mars Year 34 Planet-Encircling Dust Storm.

Citation: Viúdez‐Moreiras, D., Newman, C. E., Torre, M., Martínez, G., Guzewich, S., Lemmon, M., et al. [2019]. Effects of the MY34/2018 global dust storm as measured by MSL REMS in Gale crater. Journal of Geophysical Research: Planets, 124. https://doi.org/10.1029/2019JE005985

—Anni Määttänen, Editor, JGR: Planets

Crystal Clocks Serve as Stopwatch for Magma Storage and Travel Times

Mon, 08/12/2019 - 11:30

Volcanic eruptions are just the tip of the iceberg: Hidden deep below ground, the preeruption behavior and movements of magma remain largely mysterious. Two new studies centered around a volcano in Iceland are shedding light on how long magma was stored deep underground and how long it took to travel to the surface before erupting, information that may be used to improve existing models of complex magmatic systems.

Geophysical monitoring methods can see only so deep beneath the surface of Earth, so to figure out what is happening deep inside a volcano, “you have to be a geological detective,” said Euan Mutch, an igneous petrologist at the University of Cambridge in the United Kingdom and lead author on both of the new studies, published in Science and Nature Geoscience.

The studies represent some of the first evidence of magmatic timescales for eruptions originating in the deep crust.Mutch and colleagues at the University of Cambridge focused on the Borgarhraun eruption of Theistareykir, a volcano in northern Iceland, which took place around 10,000 years ago. Previous studies have shown the magma that fed this eruption came directly from the Mohorovičić discontinuity (the Moho), where Earth’s crust meets its mantle, at a depth of about 24 kilometers—far deeper than geophysical methods can see clearly.

To determine how long the magma was stored at the Moho before erupting, the team used a volcanic mineral called spinel as a crystal stopwatch.

“The elements in the crystal want to be in equilibrium with the surroundings,” Mutch explained.

As the elements equilibrate by diffusing out of the spinel, the mineral’s composition changes, creating a kind of crystal clock. Using known diffusion rates for aluminum and chromium, the team was able to determine how long the minerals were stored in the melt before it erupted, in this case about a thousand years, they wrote in Science.

Mineral maps like this one show areas of concentrated aluminum in yellow and lower concentrations in red and black. The process of diffusion from high to low concentration can be used to estimate how long the crystal remained in the magma chamber before erupting. Credit: Euan J. F. Mutch

In the Nature Geoscience study, Mutch and colleagues used a similar diffusion modeling technique on olivine crystals to show that the magma ascended from the Moho to the surface in as little as 4 days, at a rate of 0.02 to 0.1 meter per second.

The two studies represent some of the first evidence of magmatic timescales for eruptions originating in the deep crust at the Moho boundary, said David Neave, a petrologist at the University of Manchester in the United Kingdom who was not involved in either of the new studies.

“A lot of progress has been made understanding timescales of shallower volcanoes, but these are the first studies to estimate how long magma is stored in the deep crust before it erupts,” Neave said. “That’s crucial new information.”

Diffusion modeling is not a new technique. The methods have been around for at least 10 years, Neave said, but Mutch and colleagues “were very clever in working out the uncertainties and arrived at much more precise estimates for these timescales than previous groups have been able to do.”

The findings also lend support to a growing body of research suggesting that magmatic systems can be much more complex than the textbook model of a volcano fed directly from a single bulbous magma chamber, said Stephen Sparks, a volcanologist at the University of Bristol in the United Kingdom who was not involved in either of the new studies.

“Their results contribute to the evidence that supports vertically extensive transcrustal magma systems,” Sparks said. The study does not introduce any fundamentally new concepts but “supports this emerging new paradigm. The paper is amongst the most thorough and convincing published so far.”

Applying the Techniques to Other Volcanoes

Whether the 1,000-year timescales for magma storage and mere days of travel to the surface are typical of other volcanoes or unique to Theistareykir is unknown, Mutch said. The next steps will be to apply the same diffusion modeling techniques to other eruptions.

Crystal clocks can be used at a variety of volcano types, not just the basaltic volcanoes found in Iceland, Neave said.

“I think this approach will prove to be widely applicable to a range of volcanic settings.”“Most volcanoes are ultimately underlain by basaltic materials, even if they’re erupting rhyolite or andesite at the surface like at the Cascades volcanoes [in the United States],” he said. “I think this approach will prove to be widely applicable to a range of volcanic settings.”

The findings may ultimately aid in developing more accurate magmatic and eruption models as well as improving volcanic hazard forecasts, Mutch said. The Nature Geoscience paper in particular showed a link between the magma’s rate of ascent and the release of carbon dioxide, which could be used to predict an impending eruption.

“At the ascent rates estimated for the Borgarhraun magma, an increase in carbon dioxide flux at the surface would only be detected at most 2 days before the eruption,” Mutch said. However, other volcanic systems may offer more lead time: “This threshold will be different for magmas with different carbon contents and that are stored at different depths before eruption.”

—Mary Caperton Morton (@theblondecoyote), Science Writer

Girl Scouts Emphasize STEM Education

Mon, 08/12/2019 - 11:29

Three years ago, when Sydne Jenkins was 13, her experience at the Girl Scouts Space Academy in Huntsville, Ala., helped fuel her interest in science. The academy “opened my eyes to the wondrous world of space,” said Jenkins, now a rising high school junior in Delaware. The experience also improved her critical thinking, communication, and problem-solving abilities, added Jenkins while speaking at a recent event on Capitol Hill.

Now Girl Scouts USA  (GSUSA) is expanding its focus on science, technology, engineering, and math (STEM) education, which includes the introduction of three new space science badges.

At a 24 July briefing on Capitol Hill, Girl Scout leaders, members of Congress, and others spoke about the importance of girls entering and staying in STEM fields.

“As the world becomes ever more reliant on technology to power our daily lives, Americans need to harness the unique insights, skills, and potential of girls in the STEM fields.”As an organization, the Girl Scouts “has a long history of engaging girls in STEM activities and encouraging them to pursue their interest in science in and out of the classroom,” said Cole Grissom, GSUSA senior manager of digital content strategy. “As the world becomes ever more reliant on technology to power our daily lives, Americans need to harness the unique insights, skills, and potential of girls in the STEM fields.”

The new badges include the Space Science Researcher, aimed to help 6th–8th graders understand the properties of light and use that knowledge to better understand the Sun, stars, and other celestial objects. The Space Science Expert badge teaches 9th and 10th graders more about light and understanding the universe and humanity’s place in it. The Space Science Master, for 11th and 12th graders, goes deeper into exploring, observing, designing, and communicating space science discoveries.

The space science badges join three others introduced in July 2018 for younger children, who have already earned nearly 68,000 Space Science Explorer, Adventurer, and Investigator badges.

All six badges are part of a collaboration called Reaching for the Stars: NASA Science for Girl Scouts, which is funded by NASA’s Science Mission Directorate and led by the SETI Institute, an organization in Mountain View, Calif., whose mission includes exploring, understanding, and explaining the origin and nature of life in the universe. That collaboration also includes the Girl Scouts Astronomy Adventure Destination at the University of Oregon and Girl Scout Astronomy Club training at NASA’s Goddard Space Flight Center in Maryland.

Empowering Girls Through STEM Education

“Women are still vastly underrepresented in STEM fields,” said SETI Institute director of education Pamela Harman. “Exposing girls to these subjects in multiple formats and at different venues is vital to ignite their curiosity and to close this gap.”

Three members of the House Committee on Science, Space, and Technology, including committee chair Eddie Bernice Johnson (D-Texas), ranking member Rep. Frank Lucas (R-Okla.), and committee member Rep. Kendra Horn (D-Okla.), who said that she is a lifelong Girl Scout, attended the hearing.

STEM “has actually allowed girls to be more prominent in these male-dominated fields and in STEM careers in general.”The Girl Scouts “empowers young women to explore, to achieve, and to understand that their potential isn’t limited by where they were born or who they are, or what their background is, but is beyond their wildest dreams, if we just give young women the tools to explore,” Horn said.

High schooler Jenkins, who has been a Girl Scout for most of her life, is an example of that empowerment.

Jenkins, who confided that she wants to become a pediatric dentist, said that although she doesn’t currently plan to go into space science for her career, her exposure to STEM education through the Girl Scouts has been important.

STEM “has actually allowed girls to be more prominent in these male-dominated fields and in STEM careers in general,” Jenkins said.

—Randy Showstack (@RandyShowstack), Staff Writer

Murders of Environmentalists Have Doubled in 15 Years

Fri, 08/09/2019 - 18:56

Environmental activists and defenders are killed at twice the rate that they were 15 years ago, according to a new study. The researchers found that more environmental defenders were murdered in countries with a weaker rule of law and where more land area was harvested.

“As consumers in wealthy countries—who are effectively outsourcing our resource consumption—we share responsibility for what’s happening.”“Environmental defenders help protect land, forests, water and other natural resources,” Nathalie Butt, lead author of the study, said in a statement. “They can be anyone—community activists, lawyers, journalists, members of social movements, [nongovernmental organization] staff, and indigenous people—anyone who resists violence.”

“As consumers in wealthy countries—who are effectively outsourcing our resource consumption—we share responsibility for what’s happening,” said Butt, who studies the ecological impacts of climate change at the University of Queensland in St. Lucia, Australia. “Businesses, investors, and national governments at both ends of the chain of violence need to be more accountable.”

Environmentalists Dying Around the World

The study, which was published in Nature Sustainability on 5 August, analyzes reports of murders of environmentalists’ deaths around the world from the international environmental organization Global Witness.

The researchers found that 1,558 people in 50 countries around the world were killed defending the environment between 2002 and 2017. “This is more than double the number of United Kingdom and Australian armed service people killed on active duty in war zones over the same period…and almost half as many as the number of U.S. soldiers killed in Iraq and Afghanistan since 2001,” the study says.

More indigenous people were killed defending their land and environment than were people of any other group.During those 15 years, the rate at which environmental activists were murdered increased from two murders per week to four per week. The death toll in Brazil, the Philippines, Colombia, and Honduras represented about 71% of all environmentalists killed during that time period.

One particularly concerning finding is that about 40% of the murders in 2015 and 2016, and about 30% of the killings in 2017, were of indigenous persons. More indigenous people were killed defending their land and environment than were people of any other group.

“This is a phenomenon seen around the world: land and environmental defenders are declared terrorists, locked up or hit with paralyzing legal attacks, for defending their rights, or simply for living on lands that are coveted by others,” stated Victoria Tauli-Corpuz, the United Nations Special Rapporteur on the rights of indigenous peoples.

Killing for Natural Resources and Getting Away with It

The researchers also gathered data from organizations that track rule of law and environment-related business sectors. They found that the mining, agribusiness, water resources, and logging sectors were tied to or suspected in the highest number of deaths. More deaths occurred in countries with higher corruption rates and a weaker rule of law.

“Corruption was the key correlate for the killings.”What’s more, murders of environmentalists were much less likely to have legal ramifications than were other murders: Homicides had an overall conviction rate of 43% in 2012, but the conviction rate was only 10% for the killings of environmentalists.

“Although conflict over natural resources is the underlying cause of the violence, spatial analyses showed corruption was the key correlate for the killings,” Butt said. “In many instances, weak rule of law means that cases in many countries are not properly investigated, and sometimes it’s the police or the authorities themselves that are responsible for the violence.”

Nathalie Butt and her team found a significant correlation between the number of environmental defenders killed in a country and the country’s levels of corruption, civil and criminal justice, fundamental rights, and government control. More environmentalists were killed (larger circles) in countries with lower rule of law (ROL) scores (lighter blue). Credit: Nathalie Butt Criminalizing Environmental Activism

Global Witness released its 2018 report on attacks against environmental defenders on 30 July. The organization found that 164 people were killed last year, an average rate of more than three per week.

“Countless more were silenced through other tactics designed to crush protest, such as arrests, death threats, lawsuits and smear campaigns,” the agency stated.

On 22 May 2018, a group of roughly 20,000 environmental protesters marched toward a Sterlite Copper mining plant in Tamil Nadu in southern India. The plant was linked to soil, water, and air pollution in the area. State police killed 13 protesters in what was the largest massacre of environmental defenders in 2018. Credit: Mksr2020, CC BY-SA 4.0

Mining and agribusiness remained the first- and second-deadliest sectors for environmentalists, but last year also saw a spike in the number of deaths related to water resources. The 2018 report was released days before unrelated reports from the World Resources Institute on global water stress and from the Intergovernmental Panel on Climate Change on vulnerabilities in the land and food sectors.

Last year, Global Witness also tracked a rise in the criminalization of activism, including in the United Kingdom and Iran, a trend that the agency says has continued so far in 2019. The organization specifically called out Brazilian president Jair Bolsonaro and U.S. president Donald Trump for agendas that promote business over the environment and for policies that strip away environmental and human rights protections.

“It is a brutal irony that while judicial systems routinely allow the killers of defenders to walk free, they are also being used to brand the activists themselves as terrorists, spies or dangerous criminals,” Alice Harrison, a senior campaigner at Global Witness, said in the statement accompanying the report. “Both tactics send a clear message to other activists: the stakes for defending their rights are punishingly high for them, their families and their communities.”

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

10 August 2019: A figure was removed from this article.

12 August 2019: A figure was inserted into this article.

July May Turn Out to Be the Hottest Month in Recorded History

Fri, 08/09/2019 - 12:58

July 2019 might have broken the record for highest monthly surface air temperature, according to a report from a European climate monitoring agency. Temperatures in Alaska, Greenland, Siberia, and Antarctica were the highest relative to a 30-year average.

“July has re-written climate history, with dozens of new temperature records at local, national and global level.”“July has re-written climate history, with dozens of new temperature records at local, national and global level,” Petteri Taalas, Secretary-General of the World Meteorological Organization, said in a statement.

The Copernicus Climate Change Service (C3S) released the report on 5 August. The report shows that by one metric, July 2019 surpassed the previous record holder for hottest month ever, July 2016, by 0.4°C.

July’s temperature record comes on the heels of reports of Antarctic sea ice extent being the lowest on record, “unprecedented” Arctic wildfires, sweeping heat waves on multiple continents, and a Greenland ice sheet losing 12.5 billion tons of water in a single day.

Arctic Highs, Very Few Lows

The C3S report is a preliminary analysis based on a monthly weather data set provided by the European Centre for Medium-Range Weather Forecasts. The data set includes measurements from satellites, ships, aircraft, and ground-based weather stations around the world. On the basis of these data, “July was about 0.56 °C degrees above average,” according to a C3S statement.

“This is close to 1.2°C above the pre-industrial level as defined by the Intergovernmental Panel on Climate Change (IPCC),” C3S officials state. The IPCC recommended a warming limit of 1.5°C above preindustrial values, averaged over 30 years, to reduce the impacts of global climate change.


Map of the surface air temperature anomaly for July 2019 relative to the July average for the period 1981–2010 for the whole globe (left) and for Europe (right). Click image to view larger version. Credit: ECMWF, Copernicus Climate Change Service

Arctic regions experienced very high temperatures in July relative to the most recent 30-year reference period (1981­–2010), in keeping with long-term global warming trends. The report highlights Alaska, Baffin Island, Ellesmere Island, Greenland, and parts of Siberia as having particularly warm temperatures. Western Europe, much of the United States, Iran, and the central Asian republics were also hotter than normal.

Antarctica experienced both the highest and lowest deviations from average air surface temperature in July. Temperatures in West Antarctica, the Antarctic Peninsula, the Ross Ice Shelf, and the Ross Sea rose to around 10°C above average. Parts of the Weddell Sea and nearby lands in East Antarctica experienced temperatures a few degrees cooler than average.

Temperatures in midwestern Canada and eastern Europe were also slightly below average. Ocean air temperatures were, overall, warmer than average despite a few areas of cooler-than-average temperatures.

On Track for a Consecutive Five Hottest Years

The temperature difference between July 2019 and July 2016 was marginal, C3S cautions, and future data may show that July 2016 is still the record holder. The agency will release a more comprehensive climate report for July later this month when data from other agencies, including some in the United States and Japan, become available.

Previous reports from C3S show that, so far, each month in 2019 has been among the top four hottest of that month on record. If the trend continues, 2015–2019 will be the five hottest years on record whether or not July 2019 comes out on top.

“This year alone, we have seen temperature records shattered from New Delhi to Anchorage, from Paris to Santiago, from Adelaide and to the Arctic Circle,” United Nations Secretary-General António Guterres said in a statement. “If we do not take action on climate change now, these extreme weather events are just the tip of the iceberg. And, indeed, the iceberg is also rapidly melting.”

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

Rivers Are a Highway for Microplastics into the Ocean

Fri, 08/09/2019 - 12:41

Microplastics seem to be everywhere these days. From remote mountaintop glaciers to human guts, tiny pieces of plastic appear in the most unexpected places.

In aquatic environments, microplastics have been a known pollutant since the 1970s, when several studies found large quantities of synthetic fibers and plastic fragments in the North Atlantic Ocean. However, little is known about how and where these particles originate. For a long time, researchers thought they were fragments from larger plastic objects that broke off at sea, but recent studies show that reality might be more complex.

The researchers looked for microplastics in surface waters, along sandy beaches near the delta, and in the sediments at the bottom of the estuary. A group of researchers from the Universitat Autònoma de Barcelona in Spain has measured the concentration of microplastics in the delta of the Ebro River, one of the largest rivers on the Iberian Peninsula. The researchers looked for microplastics in surface waters, along sandy beaches near the delta, and in the sediments at the bottom of the estuary.

Their findings confirm what other researchers have been suspecting for a while: Rivers are highways that microplastics generated inland follow to the ocean.

At a rate of 3.5 particles per cubic meter of water, the Ebro River dumps 2.2 billion pieces of microplastic into the Mediterranean Sea every year. This number is actually in the medium-low range of what’s been found in other rivers in Europe and elsewhere. In extreme cases of heavily polluted rivers near densely populated areas, such as the Pearl River delta near Guangzhou in China, researchers recently reported concentrations ranging from 379 to 7,924 pieces per cubic meter of surface water. In the Seine River near Paris, another study reported 3 to 108 particles per cubic meter in 2015.

The new study is one of the few that paints a global picture of microplastic distribution in river estuaries, which are key transition zones where fresh water and seawater meet.

“Most studies report concentration in surface water, or sediments, or in the seafront of the river, but it’s really hard to make a global diagnostic of the situation with that approach,” says Laura Simon-Sánchez, a researcher and doctoral student at the Institute of Environmental Science and Technology at the Universitat Autònoma de Barcelona and first author of the study.

Simon-Sánchez and her colleagues found that microplastics tend to accumulate in sediments at the bottom of the delta, where in the Ebro they found a mean concentration of 2,052 particles per kilogram of sediment. Prevailing currents can also transport many particles that wash ashore on beaches north of the delta. On these beaches, the team found around 400 particles per kilogram of sand. Their work was published in July in Science of the Total Environment.

“We’ve seen that bottom sediments are clearly where most plastics accumulate, but we think that storms can remobilize them and push them out to sea,” says Simon-Sánchez. “Our next goal is to try to understand for how long these plastic particles stay in each environmental matrix.”“What researchers have finally realized is that all that plastic pollution is mainly coming from land-based sources, so, of course, it makes sense to look at rivers first.”

Where Do Microplastics Come From?

Today, there aren’t many studies that can shed light on how microplastics get into rivers.

“The problem is that everybody is so concerned about microplastics and plastic pollution in marine systems that we have very little knowledge about microplastic contamination in freshwater systems,” says Martin Wagner, an environmental toxicologist at the Norwegian University of Science and Technology in Trondheim. Wagner was not involved in the Ebro River study. “What researchers have finally realized is that all that plastic pollution is mainly coming from land-based sources, so, of course, it makes sense to look at rivers first.”

Overall, 70% of the microplastics found in the Ebro River delta are synthetic fibers, followed by plastic fragments and films. Simon-Sánchez thinks that these fibers probably come from domestic and commercial laundry that wastewater treatment plants fail to remove. However, Wagner disagrees and points out that there are many diffuse sources and probably even more fibers reach the rivers through their surface than from wastewater.

Synthetic fibers like these comprised about 70% of microplastics in the Ebro River. ICTA/Simon-Sánchez

According to Wagner, it will be very hard to reduce the amount of synthetic fibers in the rivers unless more studies look into how they get there in the first place. This is one of the main challenges with microplastics because they have many diffuse sources, he says.

Even without knowing how these particles get into rivers, it’s becoming clear that rivers are not only the first transport road for plastic pollution to the ocean but also an important sink for plastic pollution.

The processes of accumulation and degradation of microplastics in river sediments are still poorly understood, and little is known about how they affect aquatic life and maybe human health.

“It might still be early to ring a big alarm bell,” Wagner says. However, he adds that in a business-as-usual scenario, “we will see a risk to aquatic environments very soon.”

—Javier Barbuzano (@javibarbuzano), Freelance Science Journalist

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