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Finding Natural Solutions to Man-Made Problems in River Deltas

Fri, 04/03/2020 - 13:34

River deltas are dynamic systems, fed by sediment flows and shaped by tides and wave action over long timescales. They’ve long proved fertile ground for human civilization. Many of the world’s biggest cities are located on river deltas, where easy access to marine transport, fishing, and coastal soils gives them an economic boost. But human activities and climate change have led to the instability of deltas around the globe, threatening the ecosystem services they provide. Reservoirs and demand for sand, for example, have left many deltas starved of sediment: The Nile Delta, the Mississippi Delta, and the Yellow River Delta are all experiencing shoreline erosion as sea level rise, land subsidence, and dwindling sediment supply interact.

Coastal communities have a vested interest in promoting delta resilience, but there’s growing understanding that our conventional and inflexible strategies for managing deltas—including storm surge barriers and river embankments—are unsustainable in the face of climate change. Managers are turning to nature-based solutions, but those solutions require deep knowledge of stable delta behavior. There is almost no place on Earth left undisturbed by human activities, which makes modeling and predicting modern delta behavior all the more challenging. It’s critical to develop natural solutions to contest the challenges deltas face.

Here Hoitink et al. synthesize recent research on river deltas to identify the ways that human activities interact with natural processes to create instability and discuss the tools that researchers can use to better understand those processes and render deltas resilient. The study area spanned the globe, using the best-studied delta systems, such as the Mississippi in the United States, the Rhine-Meuse in the Netherlands, and the Yellow River of China, to inform about process evolution of deltas.

The team identified four main processes revealing delta instability that relate to both natural dynamics and human activities: riverbank failure, channel incision and siltation, river avulsions, and a shift to hyperturbidity. These processes take place over a wide range of spatial and temporal scales. Riverbank failure, or a dredging-induced hyperconcentration of suspended sediment, can occur over relatively short timescales (years to decades), whereas channel bed erosion and the formation of a new deltaic landscape may require centuries.

The authors call for the development and improvement of a host of analysis tools to better understand these complex processes, including numerical modeling, network and dynamic system theory, and direct and continuous observations. Empirical data sets on the behavior of past and present river delta systems can help inform predictions of delta behavior in the future.

The major challenges that remain, according to the authors, are determining the annual sediment balance, predicting the impacts of dwindling sediment supply and sea level rise, and combining approaches to monitoring and modeling river deltas to optimize our understanding of river delta resilience in our rapidly changing world. (Journal of Geophysical Research: Earth Surface, https://doi.org/10.1029/2019JF005201, 2020)

—Kate Wheeling, Science Writer

This Week: From EPA Enforcement to Underwater Eruptions

Fri, 04/03/2020 - 13:33

EPA Suspends Enforcement of Environmental Laws Amid Coronavirus. In case you missed the news: The U.S. Environmental Protection Agency (EPA) is no longer telling companies they must adhere to environmental laws. The temporary policy has no end date, and as Rebecca Beitsch reports for The Hill, it came after calls from industries to relax environmental goals amid coronavirus uncertainty. —Jenessa Duncombe, Staff Writer


A Decade of Science Since Deepwater Horizon.

Ten years ago, the worst oil spill in recorded history happened in the Gulf of Mexico, but from that tragedy also came enormous funding and support for science. Our April issue of Eos is dedicated to those who worked under pressure to stop the spill and who came together afterward to build huge support networks, like the Gulf Research Project and the Gulf of Mexico Research Initiative, to create a scientific movement. —Heather Goss, Editor in Chief



Coronavirus Lockdowns Have Changed the Way Earth Moves. Yet another way COVID-19 is affecting science, but this time it’s good. The drop in traffic—by foot, car, bus, train, and truck—is giving seismologists a clearer picture of the subtle movements of the Earth. The reduction of anthropogenic seismic noise is boosting the sensitivity of instruments designed to locate earthquake aftershocks and study the crashing of ocean waves. —Kimberly Cartier, Staff Writer


Satellite Sleuthing Detects Underwater Eruptions.

This satellite imagery shows the sea surface on 6 August 2019 following the eruption of Volcano F. UTC = coordinated universal time; Bft 5 = Beaufort scale category 5 winds, corresponding to 29–38 kilometers per hour. Credit: European Space Agency, Copernicus Sentinel-2, modified by Philipp Brandl

Underwater volcanoes may be out of sight, but just like their terrestrial kin, they can still be extremely hazardous, releasing plumes of gas and floating debris and sometimes triggering landslides and tsunamis. Tracking underwater eruptions is tricky because it’s difficult to monitor what we can’t readily see or reach. This piece highlights research into the (initially unknown) volcanic origins of a vast raft of floating pumice ejected during an eruption last summer in the South Pacific Ocean and discusses how combining remote sensing and other emerging methods with existing techniques like seismic monitoring could give us a better handle on these submarine hazards. —Timothy Oleson, Science Editor


Coronavirus Concerns Force Arctic Mission to Cancel Research Flights. The reach of COVID-19 stretches everywhere, including to the R/V Polarstern, which has been locked in Arctic sea ice. The Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition now faces questions about how to rotate scientists on and off the ship and keep the virus from making its way on board. Some research has already been canceled. —Tshawna Byerly, Copy Editor


Armageddon at 10,000 BCE.

The Paleolithic settlement of Abu Hureyra, in what is now Syria, may have been destroyed by the airburst of an impacting comet about 12,800 years ago. Credit: Jennifer Rice, CometResearchGroup.org

Do you need a better recommendation than that headline? —Caryl-Sue, Managing Editor


Keppel-Aleks, Swann, and Xu Receive 2019 Global Environmental Change Early Career Award

Fri, 04/03/2020 - 13:25
Citation for Gretchen Keppel-Aleks Gretchen Keppel-Aleks

Dr. Keppel-Aleks is a rising leader in the carbon cycle community. Her research uniquely combines observational and modeling tools to increase understanding of the effects of climate variability on the carbon cycle. She has made notable contributions to our understanding of the role of the terrestrial land sink in a very short period of time and has linked a range of disciplines that represent the Global Environmental Change community.

To provide constraints from atmosphere and space-based observations, Dr. Keppel-Aleks has integrated remote sensing and ground-based observations to understand the flux of carbon from the terrestrial biosphere, including remote sensing data sets (such as NASA’s Orbiting Carbon Observatory (OCO-2)) and solar-induced chlorophyll fluorescence (SIF). In addition, Keppel-Aleks is part of a team to develop and deploy tower-based spectrometer systems to connect satellite-derived SIF and ecosystem models. Her research combines a suite of various and disparate observations and tools to improve our understanding of the terrestrial carbon sink. Further, Keppel-Aleks has linked this observational framework with that of the Earth system modeling community to improve our understanding of climate-driven variations in the global carbon cycle, using modeling tools such as the Community Earth System model.

Dr. Keppel-Aleks has already taken on several leadership positions in the field, including her participation on the OCO-2 science team, as a coauthor on the U.S. State of the Carbon Cycle Report (SOCCR-2), as a cochair for the Biogeochemistry Working Group for the National Center for Atmospheric Research Community Earth System model, and as a member of the Department of Energy’s International Land Model Benchmarking (ILAMB) team. Her nominators also cite her excellent mentoring of students in the community, and I have seen this firsthand at Michigan. Dr. Keppel-Aleks has developed a diverse group and provides the support to produce excellent science in her research team.

Dr. Keppel-Aleks is an outstanding young scientist who has developed a deep and broad approach to address one of the greatest environmental conundrums of this generation.

—Allison Steiner, University of Michigan, Ann Arbor



Thank you, Allison, for your kind words. It is humbling to have been nominated by a colleague who inspires me with her interdisciplinary research approach and with her commitment to forging a more equitable and inclusive scientific community. Both of these facets—interdisciplinarity and inclusivity—are necessary to confront the scientific and social challenges posed by climate change. The research that falls under the AGU Global Environmental Change section addresses the most pressing scientific questions faced by my generation, and it is an honor to receive this section award.

This award is a reminder of how privileged I am to engage in interesting and thought-provoking work each day. Much of the joy in doing science stems from the opportunity to collaborate with and learn from other scientists. This award reflects the outstanding mentorship from which I have benefited over the course of my career. I especially acknowledge senior scientists who have taught me how to think creatively and deeply about the Earth system and the tools we use to understand it, especially Scott Doney, Jim Randerson, Tapio Schneider, Geoffrey Toon, and Paul Wennberg. It has been a pleasure to have friends from my graduate and postdoctoral programs turn into collaborators and sounding boards, especially Dan Feldman, Tim Merlis, Brendan Rogers, Rebecca Washenfelder, and Debra Wunch. This award also affirms the efforts of the next generation of scientists whom I have been fortunate to teach and advise at the University of Michigan.

Finally, I want to thank my family, especially Aaron Wolf, for their support. On the days that I am not optimistic that human civilization is up to the challenge, the people I love keep me going.

—Gretchen Keppel-Aleks, University of Michigan, Ann Arbor


Citation for Abigail L. S. Swann Abigail L. S. Swann

Abigail L. S. Swann is being recognized with the Global Environmental Change Early Career Award for her innovative, interdisciplinary research coupling vegetation and the atmosphere. Dr. Swann has appointments in the Department of Atmospheric Sciences and the Department of Biology at the University of Washington. Her contributions lie within three overlapping areas: (1) She focuses on an obvious but amazingly overlooked set of processes: how vegetation change affects climate, both locally and elsewhere, subsequently affecting vegetation elsewhere—termed an “ecoclimate teleconnection.” (2) She possesses an extremely rare skill set enabling her to run Earth system models focusing on the atmosphere as well as running relevant linked ecological models. (3) She is rapidly, creatively demonstrating the relevance of ecoclimate teleconnections for a variety of vegetation response types, at a variety of spatial scales, and for a variety of applied problems.

Dr. Swann evaluated the consequences of afforestation (adding forests) to Northern Hemisphere grasslands, a commonly discussed carbon sequestration strategy, and showed that such vegetation change could alter the position of the Intertropical Convergence Zone. Dr. Swann also focused on the converse of regional-scale afforestation—regional-scale loss of tree cover from die-off or deforestation. Her simulations reveal important cross-hemisphere impacts of tree loss from western North America or the Amazon Basin.

The potential importance of ecoclimate teleconnections is profound. On the basis of the Paris Agreement, there is now an attempt to move toward globally coordinated carbon management. Dr. Swann’s work reveals how forest changes in one continent (e.g., either increasing or decreasing forest area) could affect another. Consequently, carbon gains in one area could have a negative impact on the productivity and associated carbon dynamics in another. This has profound implications for carbon management.

Abby is making enormous contributions to science, and I am extremely privileged to have had opportunities to collaborate with her.

—David D. Breshears, University of Arizona, Tucson



I am honored to receive the Global Environmental Change Early Career Award. Thank you, Dave, for nominating me and for your kind words. Collaborating with you has been a productive, educational, and thoroughly enjoyable experience.

I am lucky to have had the opportunity to work with many people who have broadened my scientific and academic thinking and helped me to tackle problems at the boundaries between traditional academic disciplines. I am grateful for my colleagues and collaborators who have provided both formal and informal mentorship. Inez Fung has played the central role in teaching me how to do science and be a scientist, serving as a mentor since I was an undergraduate. Becky Alexander, Cecilia Bitz, Gordon Bonan, Dave Breshears, Emily Fischer, Charlie Koven, Jim Randerson, Scott Saleska, and LuAnne Thompson have all provided critical support in science and beyond. I am so appreciative to have had the opportunity to work with graduate students and postdocs Greg Quetin, Marlies Kovenock, Marysa Laguë, Elizabeth Garcia, Jennifer Hsiao, Claire Zarakas, and Greta Shum. My peer support group of women scientists at the University of Washington has been invaluable in helping me through the day-to-day challenges of research and academia. I also owe a huge debt of gratitude to my partner and our two children for their love and support.

Finally, I am happy to join Gretchen Keppel-Aleks in the 2019 cohort for this early-career award; however, I strongly believe that as a community we can and must do more to increase nominations of and awards to women and scientists from underrepresented groups for all honors, but especially for early-career awards. In failing to represent all members of our community in awards and honors, we perpetuate a history of unequal opportunities for success in our field.

—Abigail L. S. Swann, University of Washington, Seattle


Citation for Yangyang Xu Yangyang Xu

Yangyang Xu’s research has provided vital insights into major issues related to both the science of climate change and the mitigation of climate change. While still a graduate student, Xu led and completed a multi-institutional study on hydrofluorocarbon (HFC) forcing and its mitigation potential for 21st-century projected trends. This had a major impact on U.S. policy toward eliminating HFCs in refrigeration and helped provide the scientific basis for the Kigali Amendment to the Montreal Protocol.

Xu was also one of the first to show that black carbon heating contributed as much as half of the observed large warming over the elevated regions of the Himalayan–Tibetan region. A series of model-based investigations by Xu and his students and collaborators have shown aerosols from industrial activities to be an important influence on changes observed in the past few decades. These studies consistently demonstrate a more significant impact than was previously suspected for changes in precipitation extremes, latitudinal temperature gradient, drought indices, and snow cover.

In view of his significant contributions to our understanding of the physical mechanisms of climate change, their impacts, and their implications for national and international climate policies, Yangyang Xu is a highly deserving recipient of the 2019 Global Environmental Change Early Career Award.

—V. Ramanathan, Scripps Institution of Oceanography, University of California, San Diego, La Jolla



I deeply appreciate Ram for the nomination and a few of my colleagues at Texas A&M University for starting the process. I benefited greatly from the kind support and inspiration since I started working with Ram 10 years ago at the Scripps Institution of Oceanography. Ram has supplied me a flexible environment in which to explore various research topics and, more important, led me to do society-relevant climate research, which has become my main aspiration today. Through Ram, I had the chance to work with researchers in a multidisciplinary setting and have learned so much from them, especially David Victor (School of Global Policy and Strategy, University of California, San Diego) and Durwood Zaelke (Institute for Governance and Sustainable Development).

My gratitude needs to be extended to many scientists at the National Center for Atmospheric Research, where I worked for several years as a visiting student, postdoc fellow, and project scientist. The too-long-to-complete list particularly includes Warren Washington, Jean-François Lamarque, Jerry Meehl, Aixue Hu, Claudia Tebaldi, Simone Tilmes, Mary Barth, and Rajesh Kumar. The career mentoring and research advice from them continue to drive my research forward.

Since moving to Texas A&M, I have received tremendous support from many colleagues in the department as well as at the university, especially Andy Dessler, Ping Yang, Jerry North, Ken Bowman, John Nielsen-Gammon, Sarah Brooks, R. Saravanan, and Bruce McCarl. It has been a very productive and enjoyable 3 years in Aggieland.

Last and most important, I thank my family, especially my wife, Xiaoshan Gao, for her continuous sacrifice to support my (flexible) work schedule.

I’m honored by this award from the AGU Global Environmental Change section, and it will provide encouragement to my future research. Further motivation comes from the grand challenge imposed by the unprecedented rate of global and environmental change, to which I plan to devote my career. I hope the younger generations, my pre-K son and newborn daughter included, can testify (in 2100?) that we tried our best.

—Yangyang Xu, Texas A&M University, College Station

Calvin Receives 2019 Piers J. Sellers Global Environmental Change Mid-Career Award

Fri, 04/03/2020 - 13:25
Citation Katherine Calvin

Dr. Katherine Calvin has made outstanding research contributions in the area of global environmental change. Dr. Calvin’s research focuses on the interactions between human socioeconomic activity and Earth system changes. She has worked extensively in developing international scenarios for climate change research and is a leading expert in integrated assessment modeling, combining quantitative and coding expertise with broad training across Earth sciences, socioeconomics, and land use change.

Dr. Calvin’s scientific findings have been used and cited by all three working groups of the Intergovernmental Panel on Climate Change (IPCC). Her expertise has led to international recognition and community involvement as a contributing author to the IPCC Working Group III Fifth Assessment Report (AR5), lead author for the Working Group III AR6, and the coordinating lead author for the IPCC Special Report on Climate Change and Land. The IPCC reports span sectors and national boundaries to provide the scientific information and basis for understanding climate change and its impacts on natural and human systems and for informing pathways to mitigate and adapt to those changes. Kate’s diverse background and skills make her an ideal person to lead these efforts. Dr. Calvin is also the biogeochemistry group lead for the Department of Energy’s Energy Exascale Earth System Model (E3SM), coordinating model development and interacting with the other modeling groups to ensure seamless coupling and performance. With her outstanding career thus far, we look forward to the next decade of exceptional research from Dr. Calvin.

—Corinne Hartin and Ben Bond-Lamberty, Pacific Northwest National Laboratory, College Park, Md.



I am humbled and honored to receive the Piers J. Sellers Global Environmental Change Mid-Career Award this year. I had the pleasure of hearing Piers Sellers talk a few times and always found his stories of carbon and space travel inspiring. I’m also honored to be the third awardee, following the amazing Jim Randerson and Markus Reichstein. Thank you, Corinne, for nominating me!

Several people have helped mentor me and shaped my career. First, I’d like to thank my Ph.D. advisor, John Weyant, for introducing me to climate change and teaching me how to do research. The breadth of John’s knowledge and the encouragement he provides his students had a tremendous influence on me, in terms of both my field of study and the way I engage with others. Next, I’d like to thank Jae Edmonds and Leon Clarke for hiring me and teaching me about integrated assessment. The opportunities Jae and Leon gave me as an early-career researcher, from coordinating model intercomparison projects to working on next-generation emissions scenarios, helped me hone my technical skills and introduced me to leadership. I’d like to thank Tony Janetos for teaching me about land and the Earth system and steering me toward more interdisciplinary research; I will always be grateful for the chats I had with him on agriculture and the Global Change Assessment Model, and sports. Last, I’d like to thank all of the colleagues, collaborators, and coauthors with whom I’ve interacted over the years. I couldn’t have done the research I have, and certainly wouldn’t have enjoyed it as much, without them. I hope that I can provide as much to the Global Environmental Change community as it has provided to me.

—Katherine Calvin, Pacific Northwest National Laboratory, College Park, Md.

Leung Receives 2019 Bert Bolin Global Environmental Change Award

Thu, 04/02/2020 - 12:35
Citation L. Ruby Leung

Dr. Lai-Yung (Ruby) Leung has been a real force advancing the science and modeling frontiers of environmental change. She is an influential researcher and an outstanding community leader. She has pioneered modeling of regional and global climate change using innovative approaches to represent such fine-scale processes as orographic precipitation and mountain snowpack and to integrate natural and human system processes in Earth system models. Using models and observations, her research has advanced understanding of the water cycle and its interactions with anthropogenic forcings. She has demonstrated exemplary leadership in advancing community research in extreme weather and climate through field campaigns, data analysis, and modeling of such phenomena as atmospheric rivers, mesoscale convective systems, tropical cyclones, extreme precipitation, and floods and droughts. In addition to organizing workshops for U.S. climate agencies to identify gaps and priorities in climate and hydrological research, she has been serving as the chief scientist for the U.S. Department of Energy’s Energy Exascale Earth System Model (E3SM). This activity pushes the cutting edge of high-resolution climate modeling and develops unique capabilities to represent human–Earth system interactions. In sum, she exemplifies the spirit of Bolin’s legacy by advancing both science and modeling to address environmental change problems of high societal impacts.

—Rong Fu, University of California, Los Angeles



It is an honor for me to be selected for the Bert Bolin Award and Lecture of the AGU Global Environmental Change section. I am grateful for the nomination and for the committee’s selecting me for the award. I have been fascinated by water for its life-supporting function, the beauty it creates in our environment, and its mysterious ways in connecting the various parts of the Earth system. Hence, water weaves through my journey as a scientist from modeling orographic clouds and precipitation and snowpack in mountainous areas, to collecting data from a research aircraft flying through atmospheric rivers, to modeling storms and land and river processes, to exploring the mechanisms of how precipitation may respond to warming and other human perturbations. I have been blessed with many opportunities to collaborate with wonderful colleagues in my institution and scientists across the community sharing the same passion about water in its various forms in the Earth system. I thank them for being an inspiration and for sharing their ideas and expertise. I am also grateful to the U.S. Department of Energy’s Biological and Environmental Research program for its foresight and continued support of cutting-edge Earth system research and its user facilities enabling the research. Through national and international efforts, we now have an explosion of data from different observing systems and computational models capable of simulating clouds in their glorious details or connecting human and Earth system processes, providing data and tools to test our understanding and predict Earth system evolution. Continued advances in understanding and predicting regional and global environmental change will equip us with powerful knowledge to improve societal resilience to extremes and variability and change.

—L. Ruby Leung, Pacific Northwest National Laboratory, Richland, Wash.

New Classification System for Lakes Forecasts a Warming Trend

Thu, 04/02/2020 - 12:32

Elevated water levels and flooding around the Great Lakes have generated recent debate about the role of global warming, but researchers have known for years that lake temperatures are rising. To illustrate how lakes are changing, scientists have created a lake thermal classification system and noted that a significant proportion of lakes could be reclassified as warmer types as global temperatures rise.

Changing Thermal Classifications

Temperature plays a key role in lake ecology and affects phenomena such as species distribution and organism growth rate. But although there are lake classification systems for characteristics such as trophic state, which measures biological activity, there has been no temperature-based system.

“The thermal classification allows any lake in the world to be allocated to a thermal type. This will allow the responses of lakes with similar thermal characteristics to be compared or lakes with different characteristics to be contrasted.”Writing in Nature Communications, researchers have proposed a classification of lakes into nine thermal regions based on surface water temperatures. Corresponding roughly with latitude, the nine regions are, from north to south, northern frigid, northern cool, northern temperate, northern warm, northern hot, tropical hot, southern hot, southern warm, and southern temperate.

“The thermal classification allows any lake in the world to be allocated to a thermal type,” said Stephen Maberly, a limnologist and ecophysiologist at the UK Centre for Ecology & Hydrology who was the lead author of the study. “This will allow the responses of lakes with similar thermal characteristics to be compared or lakes with different characteristics to be contrasted. For example, the growing interest in effects of warming could be described for lakes from different thermal regions. It will also help work at one particular site to be contextualized at a global scale.”

Maberly and collaborators from U.K. universities in Dundee, Glasgow, Reading, and Stirling, as well as the Dundalk Institute of Technology in Ireland, used satellite data from over 700 lakes around the world collected twice a month for more than 16 years. They performed a statistical analysis of the data and established a classification system, which they applied to all areas of the world with a lake model.

Researchers studied data from 700 lakes around the world to create the new classification system. Credit: Maberly et al., 2020, https://doi.org/10.1038/s41467-020-15108-z, CC BY 4.0

Researchers applied different future climate scenarios to project how the distribution of the thermal regions could change. They found that 12%, 27%, and 66% of lakes would be reclassified to a lower-latitude thermal region under scenarios of low, medium, and high greenhouse gas concentrations, respectively. Under the last scenario, the number of northern frigid lakes will drop by 79%, whereas northern temperate and northern warm lakes will increase by 166% and 228%, respectively.

Warmer surfaces can generate a host of direct and indirect effects on lakes. These effects range from impacts on species (including fish such as salmon, trout, and arctic char that require cool water) to changes in ice cover, which may affect how people use lakes.

“Indirect effects will be linked to changes in the critical physical structure of lakes where typically, in summer warm surface water is less dense and floats on top of cooler, more dense water at depth—so-called stratification,” said Maberly. “This creates two very different environments with consequences for algal growth, deoxygenation at depth, and cycling of nutrients within the lake. Warming will increase the strength and duration of stratification, promoting development of cyanobacterial (blue-green algal) blooms, especially in nutrient-rich lakes and promoting deoxygenation at depth.”

Teasing Out the Effects of Warming

Although lakes can act as sentinels of change, they are the result of complex forces at play that make determining the effects of climate change very difficult, said John D. Lenters, an honorary fellow at the University of Wisconsin–Madison’s Center for Limnology who was not involved in the study. He called the work a robust and intensive analysis of lake surface water temperature (LSWT) data and model output but said it fails to make the case for the merits of its new approach over climate or air temperature classifications.

“There wasn’t anything that was all that surprising in the results, e.g., LSWT varies according to (mostly) latitude and elevation,” said Lenters. “And so why not just classify LSWT according to these and other more easy-to-relate-to geographic and/or climatic variables? I would think that would be of more interest to readers.”

Meanwhile, Maberly and his collaborators plan to expand their lake temperature modeling work to analyze other global aspects of future temperature in lakes. They also want to widen their analysis from temperature to other variables that can be detected with satellites.

“Ultimately, by bringing different global data sets together for lakes and their catchments we hope to define different lake biomes and the variables that control them,” said Maberly.

—Tim Hornyak (@robotopia), Science Writer

Reforestation as a Local Cooling Mechanism

Thu, 04/02/2020 - 12:28

Temperate forests have a reputation as crucial global carbon sinks. In fact, research suggests that American forests alone suck up the equivalent to 14% of annual carbon dioxide emissions in the United States. And after decades of net global forest loss, reestablishing forests worldwide is viewed as a viable option for mitigating the effects of climate change.

Beyond the carbon sequestration potential of reforestation, in many parts of the world, forests offer the added benefit of reducing surface temperatures by drawing water from the atmosphere and increasing heat transfer away from the surface. At a local level, restoring forests may help alleviate the effects of climate warming.

There is a distinction, however, between surface temperature and air temperature, and the science remains unclear as to whether reforestation also successfully lowers the air temperature. Whereas surface temperature is measured only at the surface, air temperature changes with height and may be influenced by changes in wind patterns caused by the forest canopy.

In a new study, Novick and Katul describe a novel approach to investigating both surface and air temperature on the basis of flux tower observations. The method accounts for canopy effects and uses tower measurements to estimate multiple metrics that link surface and air temperature. The research was conducted using data from three AmeriFlux sites in the Duke Forest in North Carolina. The researchers compared observations from colocated grassland, pine forest, and hardwood forest ecosystems, which represent the three phases of ecological succession in the region.

The study found that although air cooling from forests is not as significant as cooling on the surface, forest canopies still reduce air temperature near the surface by 0.5°C–1°C over a year. During the growing season, the warmest time of the year, forests reduce daytime near-surface air temperatures by 2°C–3°C. However, the effect was minimal at night.

By focusing on air and surface temperature, the study offers a more complete picture of how forests regulate temperature and cool landscapes than previous studies. The results should help communities better understand the benefits of reforestation and its upside as a climate mitigation tool. (Journal of Geophysical Research: Biogeosciences, https://doi.org/10.1029/2019JG005543, 2020)

—Aaron Sidder, Freelance Writer

Chinese Swamp Core Reveals 47,000 Years of Monsoon History

Thu, 04/02/2020 - 12:27

Every summer, one third of the world’s population receives rainfall from the East Asian monsoon. Variations in monsoon behavior can pose flood or drought risk, so understanding how it has changed over time could help clarify future risks. Wei et al. now provide new insights into 47,000 years of East Asian monsoon history.

The new research addresses a lack of long-term, high-resolution data on past monsoon variability from southern China. To help fill this gap, the researchers collected an 8.6-meter-long sediment core from Dahu Swamp in the Nanling Mountains of southern China; the region’s topography makes it particularly sensitive to shifts in monsoon rainfall patterns.

The research team took samples of material every 2 centimeters along the length of the core and analyzed each sample’s magnetic properties to produce snapshots of mineral composition in the swamp at different time periods. These snapshots provided clues to the hydrologic and climatic processes in play when the materials were deposited.

Findings from the mineral-magnetic analysis enabled the scientists to reconstruct patterns of fluctuation between relatively wet and dry periods in the region over the past 47,000 years. These monsoonal rainfall patterns are consistent with data from northern China and are in line with past climate changes resulting from gradual shifts in Earth’s orbit and orientation.

The results also add to mounting evidence against a traditional view that climate processes at high latitudes were the primary driver of paleoclimate monsoon trends. The new findings suggest that tropical climate patterns associated with the El Niño–Southern Oscillation have played an important role in driving long-term monsoon rainfall patterns.

This research could help refine climate models and improve predictions of future shifts in monsoon rainfall patterns as climate change progresses. (Paleoceanography and Paleoclimatology, https://doi.org/10.1029/2019PA003796, 2020)

—Sarah Stanley, Freelance Writer

Floating Patches of Soil Nutrients in Soil Help Explain Arctic Thawing

Thu, 04/02/2020 - 12:25

The Arctic is warming at a rate that outstrips any other region of the planet, and the rapidly thawing permafrost houses an estimated 1,400 gigatons of carbon, which is nearly triple the total amount of carbon circulating in the atmosphere. Understanding soil dynamics and their feedbacks is vital to understanding how Earth’s climate will change in the future.

To understand what will happen as permafrost continues to thaw, scientists look to Arctic environments where the soils already undergo regular freeze-thaw cycles. About a quarter of the Arctic is made up of High Arctic polar deserts. In these regions, the soil thaws in the summer as temperatures average in the single digits on the Celsius scale. During this time, polar desert plants—mostly mosses, algae, lichens, and small shrubs—and soil microbes come out of hibernation and perform all the chemistries of life that cycle carbon and nitrogen through the environment.

The freeze-thaw cycle also produces unique physics within the soil itself, creating frost boils, which churn nutrients vertically through the ground. In some instances, this process can create nutrient-rich soil layers called diapirs. Diapirism can occur in viscous soils and is expected to increase with soil moisture caused by permafrost thaw in a warming climate. Scientists have previously observed that some plants, especially Salix arctica, preferentially target diapirs with their roots, making the soils a potential nutrient source for greenhouse gas production. However, the biological processes at play in diapirs are still quite poorly understood.

Here Ota et al. compare the soil in frost boils with diapirs to the soil in frost boils without diapirs. The study took place in two different types of polar deserts near Alexandra Fjord, Ellesmere Island, Nunavut, Canada, during July and August of 2013. Diapirs were 29% richer in nitrogen. The scientists also found that diapirism increased the concentration of low-quality carbon—carbon contained in molecules that are challenging to microbial decomposition. Although the lower-quality carbon reduced microbial activity, the researchers confirmed that Salix arctica does increase its root density in diapirs, a finding they say suggests a mutualistic relationship between the plant and the microbe, with both benefiting from diapirism overall.

The researchers also found an abundance of polysaccharides in the frost boils that contained diapirs. Polysaccharides are sugar molecules common in both plant and microbial chemistry. What’s interesting about the presence of polysaccharides is that they make the soil more viscous, which should make it more prone to diapirism. One hypothesis the researchers have is that the plants or the microbes (or both) are secreting these sugars into the ground to promote diapirism.

This complex interplay between soil physics, plant, and microbes—what the scientists call “geomorphologic-plant-microbe interactions”—might even explain why only 30% of the frost boils in the study region contained diapirs in the first place. Because these nutrient-rich soil layers are a hotbed for Arctic greenhouse gas production, understanding how they form could greatly improve our knowledge of just how quickly the planet warms and the Arctic thaws. (Journal of Geophysical Research: Biogeosciences, https://doi.org/10.1029/2019JG005263, 2020)

—David Shultz, Science Writer

Fresh Approaches to Protecting Human Health from Pollution

Thu, 04/02/2020 - 11:30

Historical and current pollution from numerous sources causes disease and death throughout the world. To reduce the impact of this pollution on human health, comprehensive and cost-effective methods are needed to identify these sources.

Filippelli et al. [2020] give an excellent overview of new ways to identify and reduce pollution-related health burdens. These new approaches include low-cost monitoring of air pollution using satellite reflectance data to measure metal contamination of soils and incorporating citizen science for data collection.

The paper stresses the need for policy makers and scientists to work together to protect human health into the 21st century. The case studies provided show how pollution science can be combined with real applications for global communities to safeguard human health.

Citation: Filippelli, G., Anenberg, S., Taylor, M., van Geen, A., & Khreis, H. [2020]. New approaches to identifying and reducing the global burden of disease from pollution. GeoHealth, 4, e2018GH000167. https://doi.org/10.1029/2018GH000167

—Karen Hudson-Edwards, Editor, GeoHealth

During a Pandemic, Is Oceangoing Research Safe?

Wed, 04/01/2020 - 17:43

Oceanographer Rainer Lohmann from the University of Rhode Island was on a research cruise near Barbados when the coronavirus spread rapidly into a pandemic.

“When we left, everything was normal.”“When we left, everything was normal,” Lohmann said, speaking by phone while his ship, the R/V Endeavor, waited to dock in the city of Praia in Cape Verde on 17 March. “Now what we’re hearing and seeing is that we’re coming back to a country where we have to fight for toilet paper, where there are no hand sanitizers left, and you can’t go out to restaurants.”

The Endeavor left the Caribbean island of Barbados in late February and set off toward Cape Verde near West Africa, collecting sediment cores as it went. Lohmann and his team were investigating whether ocean sediments thousands of meters below the surface contained traces of atmospheric black carbon. After traversing much of the Atlantic Ocean, they had all the samples they needed and planned to fly home via Europe in mid-March.

But they faced a problem: The United States had just imposed strict travel restrictions through Europe. They needed a new way home.

Past Plans Scrapped…

Scientists around the world are scrambling to adjust to a rapidly changing environment. Researchers are shuttering their labs, switching to remote observing on telescopes, and learning to present their work virtually. A confirmed case of coronavirus disease 2019 (COVID-19) among the aircraft team of the Arctic expedition Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) quarantined about 20 of its members. Universities around the world have closed, some for months.

“It’s just one domino falling after the other, and you realize that you’re just in the middle of this geopolitical crisis.”Research teams and oceangoing scientists who work in the field, often in remote locations, are facing new questions about how to conduct science safely. The organization that coordinates oceanographic research vessels across 59 academic institutions, University-National Oceanographic Laboratory System (UNOLS), paused operations on its vessels for 30 days on 13 March. This week, the group extended the pause until July.

R/V Endeavor, one of the UNOLS fleet, is one of the few vessels that were midvoyage when the situation worsened. Endeavor barely made it to Cape Verde before its ports closed to ships, Lohmann said. Their flights through Europe blocked, he and five other scientists who live in the United States decided to stay on board the ship as it travels back to its homeport in Rhode Island. Two scientists on the cruise from Spain departed at Cape Verde to catch one of the few remaining flights back home.

“It’s just one domino falling after the other, and you realize that you’re just in the middle of this geopolitical crisis,” Lohmann said.

…And Future Plans Dashed

UNOLS chair Craig Lee said that the group postponed cruises partly because it’s not known how expeditions can mitigate the risks of transmission of COVID-19 while at sea. “In the U.S. it is clear that the peak of the outbreak and any beginnings of a reduction or flattening of ‘the curve’ are still weeks away, and are based on successful social distancing efforts,” UNOLS wrote in a statement.

Social isolation and physical distancing are “difficult to impossible” on a ship.But on a ship, social isolation and physical distancing are “difficult to impossible,” said Lee. Crew, technicians, and scientists may come from many locations for the same cruise, making it challenging to limit geographic risk. Putting a group in small quarters runs a higher risk of transmission, especially since testing participants for COVID-19 before the cruise isn’t possible, according to Lee. While each cruise has at least one person trained in emergency medicine and significant medical supplies, ships have “far short of an ICU [intensive care unit],” said Lee, and it could take days to get to port.

Oceanographer Jonathan Fram at Oregon State University had a local cruise scheduled in late March to replace equipment in a long-term array installed off the coast. “We have a parking lot full of wonderful moorings, clean and ready to go,” he said. Usually, the team services the array every 6 months to monitor, among other things, ocean acidification and low-oxygen conditions that can be harmful to marine life.

Their cruise is now canceled, and Fram is concerned about their equipment left at sea. The moorings will “go dark” after a while, he said, and the autonomous, torpedo-shaped underwater vehicles (gliders) that traverse the array will run out of batteries in May.

“Our hope, at least, is that we can find a way forward for some of the more local endeavors.”Pushing back the cruise means that the team will miss recording data during the coastal ocean’s transition from winter to spring, when ocean upwelling brings nutrient-rich waters along the Pacific Coast. “It’s important to get a measure of that transition. And we’re not going to be able to do that as well this year,” Fram said.

Local cruises like Fram’s may get some respite, according to UNOLS leadership.

“Our hope, at least, is that we can find a way forward for some of the more local endeavors,” Lee said. “And again, it depends on how things evolve.” UNOLS is working with federal agencies to roll out guidelines in the coming days to help operators assess risks. Cancelations can be particularly hard on students and early-career scientists who have a “short, but critical, phase of their research careers,” said Lee.

As for the R/V Endeavor on its international cruise, Lohmann said that the crew took precautions to limit any transmission risk while in port in Cape Verde. Food was handed over the raised platform connecting the ship to the dock, people did not leave the ship if they intended to get back on, and no new passengers joined for the voyage home. During their 2-week journey back, those on board are taking their temperatures daily and using disposable cutlery and dishware. Lohmann hopes that their transit time will count toward any required quarantine when they get back to Rhode Island.

“We couldn’t foresee that those 3 days were going to make the difference for most of us.”Until then, Lohmann said, the people on board are playing cards, watching movies, and joking around. “We realized that we will face social distancing once home and will long for group activities.”

Lohmann said the expedition was laid over for 3 days in Barbados at the start of the cruise, meaning they missed the window to catch flights back to the United States. “We couldn’t foresee that those 3 days were going to make the difference for most of us,” Lohmann said.

—Jenessa Duncombe (@jrdscience), Staff Writer

La Violencia Aumenta con el Cambio Climático

Wed, 04/01/2020 - 11:56

This is an authorized translation of an Eos article. Esta es una traducción al español autorizada de un artículo de Eos.

El cambio climático y la degradación ambiental están incrementando la violencia contra las mujeres y obstaculizando el cumplimiento de los objetivos de desarrollo sostenible, según un nuevo informe publicado por la Unión Internacional para la Conservación de la Naturaleza (UICN). El empeoramiento de las condiciones en todo el mundo podría conducir a un incremento de la violencia en medida que los recursos naturales comiencen a escasear.

Los más vulnerables a menudo se ven afectados de manera desproporcionada por problemas ambientales: un informe del grupo de investigación Lancet Countdown encontró que los niños y las mujeres embarazadas sufrirán el aumento de las temperaturas y la contaminación del aire en las próximas décadas; las comunidades afroamericanas están más expuestas a la contaminación del aire; y las personas de color, particularmente los nativos americanos, están más expuestos a los incendios forestales.

En el último reporte, los investigadores estudiaron los vínculos entre los problemas ambientales (incluida la deforestación, la minería ilegal, los desastres relacionados con el clima, la sequía y el cambio climático) y los casos de violencia de género. Las personas de cualquier género pueden experimentar violencia, incluyendo violencia doméstica, agresión sexual, prostitución forzada y otros actos de abuso. Debido a las normas sociales y culturales, las mujeres y las minorías de género suelen estar en mayor riesgo.

Combinando información de investigaciones publicadas en revistas arbitradas, informes organizacionales, artículos de noticias, casos de estudio y la encuesta de la UICN, los autores encontraron estrechos vínculos entre el empeoramiento de los factores de estrés ambientales y un aumento en la violencia de género.

“La precedencia, la vulnerabilidad, la probabilidad y las tasas reales de violencia ya están aumentando claramente en algunos contextos”, dijo Cate Owren, gerente senior de en UICN y autora principal del informe. “Estamos en una trayectoria peligrosa”.

La Violencia Como Control

Las estrictas normas y reglas de género, así como las leyes, limitan a quienes tienen acceso a los recursos, como las mujeres agricultoras que no pueden vender alimentos en el mercado debido a su género. La violencia, dijo Owren, “se usa de manera generalizada como una herramienta para negociar el poder, para mantener el desequilibrio de poder y mantener intacta la desigualdad”. El informe estima que una de cada tres mujeres experimenta violencia de género en su vida.

En un caso de estudio en Vanuatu, la violencia de pareja aumentó en un 300% después de dos ciclones tropicales. Owrens señaló que la violencia doméstica también aumentó en Australia después de varios años de sequía, y en general, el informe describe cómo aumenta la violencia de pareja cuando los hombres intentan controlar recursos limitados bajo las presiones y amenazas ambientales.

Las tensiones por la escasez de recursos también pueden reforzar las desigualdades de género, como las familias que fuerzan a sus hijas a casarse a una edad temprana. Ntoya Sande, una mujer que se casó a los 13 años en la aldea de Kachaso, Malawi, dijo en el informe que antes de su matrimonio, las tierras de su familia habían sufrido inundaciones. “Me enviaron a casarme por la escasez de comida en la casa. De lo contrario, habrían esperado.” Malawi ahora enumera el matrimonio infantil como un riesgo mayor en su documento de 2015 acerca de evaluación de necesidades posteriores al desastre.

Un estado de derecho débil puede llevar a las autoridades a hacer la vista gorda ante el abuso. La minería ilegal, la pesca, la tala y otras prácticas pueden conducir a la explotación sexual. El informe señala que en África oriental y meridional, los vendedores de pescado exigen sexo a las mujeres a cambio de los peces, y se estima que 1,000 hombres y niños, la mayoría de los cuales tenían 14 años o menos, fueron traficados solo en 2015 en la industria pesquera ilegal cerca de Indonesia.

“Necesitamos Abrir los Ojos”

Dado que el cambio climático acelerará los desastres como sequías, eventos meteorológicos extremos y otras consecuencias, los autores del informe advierten que estas situaciones conducirán a mayores tasas de violencia. “Concluimos que esta es una trayectoria muy preocupante”, dijo Owren.

Los defensores del medio ambiente corren un riesgo particular. Según la investigación publicada el año pasado, los activistas en la línea de defensa de la tierra y los recursos naturales son cada vez más asesinados, y las mujeres, en particular las indígenas, enfrentan amenazas crecientes, como se describe en el último informe.

Las organizaciones que abordan los impactos ambientales deben considerar cómo sus esfuerzos impactan la violencia de género; de lo contrario, las soluciones pueden hacer más daño que bien, según el informe. Las personas LGBTQ+ pueden enfrentar amenazas en los centros de evacuación después de un desastre o encontrar problemas con los esfuerzos de ayuda cuando los documentos oficiales no coinciden con su identidad o presentación de género.

La planificación de la gestión del riesgo de desastres debe mitigar estos desafíos, según Owren. “Tenemos que abrir los ojos”, dijo. “Esperamos que esta publicación contribuya como … un verdadero llamado a la acción”.

—Jenessa Duncombe, escritora de Eos

This translation was made possible by a partnership with Planeteando. Esta traducción fue posible gracias a una asociación con Planeteando. Traducción de Luis David Coazozon García.

Florida Coastlines Respond to Sea Level Rise

Wed, 04/01/2020 - 11:56

Sea level rise is one of climate change’s hallmarks. Rising seas threaten coastal populations and can damage coastal ecosystems. Some ecosystems, though, appear to be building themselves up as the water rolls in.

In coastal mangroves and marshes, dead plant matter like leaves and roots does not decompose as it does in drier environments. Instead, it is “buried” in the wet ground. For some of these coastal wetlands, the burial rates seem to be increasing.

Breithaupt et al. noticed this pattern. They took soil core samples from different coastal systems in southwestern Florida to determine whether this trend was genuine or merely an illusion arising from the most common methods used.

The scientists compared several measures, focusing primarily on the degradation of different types of organic carbon and the different tools used to quantify sediment accumulation rates. They determined that the apparent increase was not an artifact of a particular method or an illusion caused by old carbon washing away or degrading over time.

Further examination confirmed that the additional carbon was not merely washed into the study areas from other parts of the coastline or deposited by major storms. Local factors, such as the type of vegetation and the availability of nutrients, played a larger role in the carbon burial increase.

The scientists surmised that sea level rise may drive the increasing accumulation of soil carbon. Longer flood periods encourage mangrove and marsh vegetation to expand their belowground systems, producing and storing more carbon there. Rising sea levels may also allow more space for carbon to be buried and preserved.

This means these coastal areas are both responding well to sea level rise and pulling more carbon from the atmosphere. In the past 120 or so years, organic carbon burial rates have increased by factors of 1.4–6.2 in marshes and mangroves, with mangroves having the greatest gains. As a result, stored carbon stocks have increased by about 4–8 kilograms per square meter in the past century in these study areas.

However, rising sea levels still pose a threat to these systems. Rapid, heavy sediment deposits from hurricanes can smother and kill mangrove trees and other vegetation. Further, the waters are rising faster over time. Though these ecosystems are handling the change now, it remains to be seen how high sea level rise rates can go before adverse effects threaten to drown them.

This dynamic relationship between coastal ecosystems and the sea is an important factor both in carbon estimates and in predicting the effects of sea level rise. As the climate continues to change, more research is needed to estimate how widespread this phenomenon is and to inform coastal decision-making about the best ways to manage ecosystem responses. (Journal of Geophysical Research: Biogeosciences, https://doi.org/10.1029/2019JG005349, 2020)

—Elizabeth Thompson, Science Writer

Microbial Mechanisms Change with the Seasons

Wed, 04/01/2020 - 11:55

Poets and philosophers have long walked ocean shores and marveled at the meeting of solid land and rolling waves. Rarely, if ever, have they acknowledged the microbes beneath their feet that depend on this dynamic intersection of sand and sea.

As the tide and waves surge in, water soaks into the sand. Microbes living in the sand capture particles and dissolved components in the seawater, like organic matter and oxygen, that are necessary for them to grow and survive. As the tide flows out, it carries out their by-products.

Ahrens et al. investigated this phenomenon on the tidally influenced high-energy beach of a barrier island off northwestern Germany. They found that over the course of a year, changes in factors such as seawater composition and temperature altered the way microbes could process incoming organic matter.

In cold seasons, microbes are less active, and seawater can hold more dissolved oxygen. This allows oxygen to penetrate deep into the sand of the shore, and microbes use the oxygen in aerobic pathways to break down organic matter. Furthermore, in areas saturated with oxygen, the microbes convert ammonium (NH4+) to nitrate (NO3−) and then use the nitrate to run other reactions to break down organic material. In warm seasons, microbes are more active, and these oxygen-rich zones don’t penetrate as deep—so active microbes use the oxygen close to the surface. This leaves more of the microbes in the sand to pursue anoxic pathways, converting manganese and iron minerals from a particle to a dissolved form. These dissolved elements may then partly be released into seawater, along with ammonium as a by-product.

Because of these seasonal changes, the shore of this beach is a sink for dissolved inorganic nitrogen forms in cold seasons, which reduces the coastal nitrogen stock. In warm seasons, the beach turns into a source for ammonium, supplying dissolved nitrogen to algae. Dissolved manganese, and probably iron, is released year-round, but in the warmer seasons their output is more significant.

These results come from one beach, but similar high-energy beaches exist throughout the world. As scientists make global estimates about ocean and especially coastal water changes, they must take into account these tiny microbes and their substantial role. (Journal of Geophysical Research: Biogeosciences, https://doi.org/10.1029/2019JG005399, 2020)

—Elizabeth Thompson, Science Writer

Flechtner Receives 2019 Ivan I. Mueller Award for Distinguished Service and Leadership

Wed, 04/01/2020 - 11:53
Citation Frank Flechtner

It is a privilege and a distinct pleasure to write this citation for Frank Flechtner, winner of the 2019 Ivan I. Mueller Award for Distinguished Service and Leadership.

Throughout his distinguished career, Frank has personified the spirit of the Mueller Award. Even with his first project in 1988, the German Precise Range and Range-Rate Equipment (PRARE) satellite tracking system, he had a remarkable end-to-end impact, spanning deployment fieldwork, development of the master control segment, the processing and archiving facility, satellite altimetric software development, and user training and education workshops. In the 2000s, Frank was among the dedicated group working on a series of space missions during the very successful Decade of Geopotential Field Research. He served as project manager for the German gravity and magnetics mission Challenging Minisatellite Payload (CHAMP), and took responsibility for major Gravity Recovery and Climate Experiment (GRACE) subsystems and its mission operations and the science data system in Germany. Since 2009, he served as the co–principal investigator for the GRACE mission. From this time until the end of the GRACE mission in 2017, he ensured the continued operation of the GRACE extended mission by marshalling resources for continued ground operations and science data analysis in the German mission segments. Since 2010, Frank has been instrumental in making possible the GRACE Follow-On mission, with GFZ in the lead role for managing the German contributions to this joint U.S./German space mission. His unflagging efforts for advocacy and promotion of the mission among the sponsors were key to ensuring continuity of geodetic measurements of the global mass change.

Frank’s selfless commitment to geodesy is evident from how he has nurtured the growth of his research group at GFZ and led its collaborations worldwide in space missions, instrument development, and applied sciences research. Frank has displayed exemplary leadership of numerous research and development initiatives, promotion of scientific conferences and sessions, and mentorship of students and scientists at the Technical University of Berlin and GFZ.

—Srinivas Bettadpur, Center for Space Research, University of Texas at Austin



I am honored and proud to receive the 2019 Ivan I. Mueller Award for Distinguished Service and Leadership. Thanks, Srinivas, for your wonderful citation, and everyone involved in this nomination, especially Byron Tapley and Chris Reigber, the principal investigator and initial co–principal investigator of GRACE, for always being inspiring role models for me.

Since I started working on the GRACE project in 1998, unbelievable progress has been made analyzing and applying mass transport data. Although the “E” in GRACE Follow-On still stands for “Experiment,” operational services such as the U.S. Drought Monitor meanwhile rely on the integration of total water storage data (besides other observations). In Europe, the Horizon 2020 program has recently funded a project to develop a Global Gravity-based Groundwater Product, which is managed by my institute and significantly based on GRACE/GRACE-FO mission data.

The accuracy of monthly mass transport data could be continuously improved by the joint U.S./German Science Data System since 2002 throughout several reprocessings. In parallel, the new International Combination Service for Time-variable Gravity Field Solutions (COST-G) under the umbrella of the International Association of Geodesy’s International Gravity Field Service will provide consolidated monthly global gravity models by combining solutions or normal equations from various international analysis centers, a service well known from the International Earth Rotation and Reference Systems Service (IERS) or International GNSS Service (IGS). Both will further help using gravity mission data for numerous applications in such Earth system sciences as hydrology, oceanography, glaciology, or geophysics.

I am grateful that I could support the development and operation of this unique measurement system within my career, which brought me scientific inspiration and many new friends. I am proud to be part of the GRACE family! Last but not least, I would like to thank all my colleagues in the United States and Germany who supported me on this path, as well as my family for their endless patience and support throughout these years.

—Frank Flechtner, Helmholtz Centre Potsdam – GFZ German Research Centre for Geosciences, Potsdam

Grandin Receives 2019 John Wahr Early Career Award

Wed, 04/01/2020 - 11:52
Citation Raphaël Grandin

Raphaël Grandin obtained a master of science degree in executive engineering at École des Mines de Paris and a Ph.D. at Institut de Physique du Globe de Paris (IPGP). He held a position of teaching assistant at University of Paris, was a postdoctoral fellow at École Normale Supérieure de Paris, and is now an associate professor at University of Paris and IPGP.

Raphaël studied a variety of geophysical problems related to seismology, rifting and magmatic processes, and earthquake source models using space-based geodesy. It is with innovative advances in the methods and applications of interferometric synthetic aperture radar (InSAR) that his scientific contributions stand out.

His early work on the Ethiopian rifting episode of 2005–2009 provided an unprecedented account of the entire sequence of events, placing constraints on tectonic stress, magmatic pressure, and the time-dependent migration of magma between deep and shallow reservoirs. In the Himalaya, he used innovative data correction methods to extract the uplift velocity profile across the range, highlighting the stepwise migration of crustal ramps to the mountain front.

What characterizes Raphaël’s work is a combination of fine observations and the development of innovative physical interpretations of the processes behind those observations. This is exemplified in the study of recent earthquakes, from both tectonic (Nepal, 2015; Chile, 2012) and man-made (Oklahoma, 2016) origins.

Raphaël is also a dedicated mentor and teacher. He contributed to the development of community InSAR software and serves as scientific advisor for the Centre National de la Recherche Scientifique (CNRS) Solid Earth Data Center in France. He received citations for excellence in refereeing from the editors of two AGU journals in 2013 and 2014 and of Earth, Planets and Space in 2015.

We are thrilled to see Raphaël’s achievements recognized by the 2019 John Wahr Early Career Award.

—Marie-Pierre Doin, Institut des Sciences de la Terre, Université Grenoble Alpes, Grenoble, France; and Gilles Peltzer, University of California, Los Angeles


Receiving the 2019 John Wahr Early Career Award is a great honor for me. I knew nearly nothing about geology until the age of 20, as I was entering the French grandes écoles system. Just as I was about to embrace an engineering career in industry, joining the Institut de Physique du Globe de Paris as an intern totally changed my perspectives about scientific research. I owe a lot to my professor, Pascal Podvin, and to my mentor, Geoffrey C. P. King, who encouraged me to pursue this direction, recognizing that I had suddenly become passionate about earthquakes and volcanoes.

This nomination also rewards collaborative efforts to expand the development and application of InSAR. I am extremely grateful to Jean-Bernard de Chabalier and Anne Socquet for introducing me to InSAR in 2007. I have been lucky to benefit from data generously provided by space agencies (in particular, the European Space Agency) and from open-source software developed by pioneers in the field (especially ROI_PAC and its expansion through NSBAS). I am thankful to Marie-Pierre Doin and Gilles Peltzer for sharing their deep understanding of InSAR ever since.

Space geodesy is about to enter a new stage of development, with the launch of next-generation SAR systems and swarms of small SAR satellites. The free and open data policy adopted by international space agencies will continue to boost the development of nascent research directions. Easy access to imagery is equally important to facilitate collaboration with local authorities in charge of volcano surveillance and earthquake hazard mitigation and, eventually, to benefit threatened populations.

Just as others did for me, I wish to be able to take my share in supporting and inspiring the next generation of young researchers, to make the best of these new opportunities.

—Raphaël Grandin, Institut de Physique du Globe de Paris, Université de Paris, Paris, France

How Climate Science Is Expanding the Scale of Ecological Research

Tue, 03/31/2020 - 11:38

Researchers have long known about climate dipoles: a synchronized seesaw in patterns of temperature and precipitation across vast distances. El Niño years, for example, tend to bring rainy weather to the southern United States and drought in the Pacific Northwest. Now, researchers believe that there are ecological dipoles as well: contrasting effects of climate dipoles on populations of plants or animals separated by thousands of kilometers.

In a new study, published in Trends in Ecology and Evolution, researchers suggest that ecologists can use tools from climate science to study how climate variability manifests as ecological signals at continental scales.

“It’s basically treating the biological observations of, say, birds and plants in the same way that climatologists treat observations of temperature and rainfall.”“Climate scientists have a whole suite of tools by which they’re able to look at things like variability and changes over space and time, and now we can take those same approaches and think about how we can capture those dynamics for ecological responses,” said Benjamin Zuckerberg, an associate professor at the University of Wisconsin—Madison and lead author on the new study. “It’s basically treating the biological observations of, say, birds and plants in the same way that climatologists treat observations of temperature and rainfall.”

Ecologists have long known that plants and animals respond to regional changes in climate—even climate shifts that correspond with climate dipoles. Scientists tracking migratory songbirds, for example, have found that when a positive North Atlantic Oscillation brings warmer weather to the United States, migrants arrive earlier in the spring.

Some of the strongest evidence so far that climate dipoles correlate with ecological ones comes from marine species, according to the study authors. The phase of the Indian Ocean Dipole (IOD), a shift in sea surface temperatures nicknamed the “Indian Niño” that impacts the position of the northern boundary of cold, Antarctic waters, correlates with the breeding success of king penguins, for example. Penguin populations tend to fall when warm water associated with a positive IOD pushes the boundary (where penguins’ prey tends to congregate) away from their colonies, forcing penguins to travel farther and deeper for food.

The Rise of Citizen Science

Until recently, however, ecologists couldn’t always see what was happening at the other end of the climate seesaw. That’s because, historically, ecological data have been collected and analyzed at smaller spatial scales than climate and weather data, according to Zuckerberg.

“We’re able to collect ecological data at a scale that now rivals what meteorologists and climatologists have been working with for the last 50 years or more.”“We tend to collect data for a few species, on a few acres of land, over a few years to answer very specific questions in ecology,” he said. “But we’re opening up now, in the sense that we’re able to collect ecological data at a scale that now rivals what meteorologists and climatologists have been working with for the last 50 years or more.”

Zuckerberg credits citizen scientists with providing ecologists with the troves of data necessary to study the connections between climate variability and populations at continental scales. He points to platforms such as the USA National Phenology Network, which tracks seasonal changes in plants and animals with help from thousands of amateur naturalists, and Cornell University’s eBird platform, one of the largest citizen science projects in the world. The platform has collected more than half a billion bird observations by birdwatchers from around the world, which the Cornell Lab of Ornithology used to create migration maps for more than 600 species of birds in the Western Hemisphere. Both platforms make all the data collected available to researchers, resource managers, educators, and, of course, the public.

Now that researchers can tap into that data and use tools that have been honed by climate researchers, Zuckerberg said, they can begin to think about ecological synchronicity in populations that are separated by thousands of kilometers.

Climate Change Complicates Forecasts

“The key advancement here is a conceptual one: this idea of ecological dipoles,” said Kevin Rose, an assistant professor at the Rensselaer Polytechnic Institute in Troy, N.Y., who was not involved in the study. “This paper sets the stage: Here’s what an ecological dipole is; here’s how we quantify it.”

That’s what Zuckerberg and his colleagues plan to do next: test their hypothesis in future studies by looking at the relationships between bird migration, seed production, and climate variability.

Forecasting ecological dipoles, or the lack thereof, is a critical tool for conservationists and resource managers. If distant populations are synchronized, entire species may be vulnerable to disease outbreaks, pests, or extreme weather such as flooding or drought. If they’re not synchronized, managers can focus resources on the populations at the vulnerable end of the dipole. Understanding how populations will respond to shifts in climate is all the more important in the era of climate change.

Take the king penguins: As ocean waters have warmed over the past few decades, some 900,000 king penguins have disappeared from Île aux Cochons, a volcanic island sitting between Antarctica and Madagascar that’s home to the largest aggregation of the birds. Researchers predict that if the warming trend continues, the king penguin population could be cut in half by the end of the century.

Climate change is also influencing the magnitude, predictability, and even the location of climate dipoles. “A warming world will definitely alter these climate dipoles in the future. Some of these fairly regular and predictable changes in the climate system, like El Niño and the North Atlantic Oscillation, are becoming more variable, strengthening in their magnitude, and in some cases, are shifting,” Zuckerberg said. “Thinking about how species are going to respond to that shifting variability is one of the big challenges that we have going forward.”

—Kate Wheeling (@katewheeling), Science Writer

How Mars’s Magnetic Field Let Its Atmosphere Slip Away

Tue, 03/31/2020 - 11:37

Four and a half billion years ago, Mars boasted a thick atmosphere and abundant surface water—conditions that could have hosted life. But today, only wisps of that atmosphere are left, clinging thinly to the planet.

How did so much Martian air slip into space? One major factor is thought to be the loss of the planet’s magnetic dynamo—the engine in its liquid core that powered its global magnetic field, which mysteriously shut down around 4 billion years ago. Left behind was only a feeble remnant of that field, emanating from the planet’s weakly magnetized crust. Conventional wisdom holds that a planetary magnetic field acts as a shield, protecting the atmosphere from being blown into space by the Sun’s solar wind and radiation (which would have been even stronger when the Sun was younger).

Now Sakata et al. report simulations that add a new wrinkle: A weak magnetic field, like at Mars after its dynamo shut down, may actually bleed its atmosphere faster than no magnetic field at all.

Using magnetohydrodynamic models, the authors explored how varying the strength of Mars’s magnetic field affected the loss of atmospheric ions like oxygen and carbon dioxide into space. As expected, a strong magnetic field that could easily withstand the pressure of the solar wind was able to guard its atmospheric ions. With no magnetic field, the Sun stripped those ions away up to 100 times faster.

But the highest rate of atmospheric ion loss was with a weak magnetic field—6 times faster than with no magnetic field at all. The team found the reason was the magnetic field lines, which guide the motion of charged particles, were easily blown back by the solar wind, creating a path for these ions to escape into space above Mars’s nightside. This means that instead of providing a small measure of protection, Mars’s remnant magnetic field could actually have sped the planet’s transformation into the cold, barren world it is today.

Understanding how planetary magnetic fields can protect against stellar activity is also important to the search for life in other solar systems. Red dwarfs, the most common type of star in the universe, blast their planets with strong stellar winds and extreme ultraviolet radiation. Whether those planets have managed to retain their atmospheres like Earth or have lost them to space like Mars could have a major impact on how common life is in the universe. (Journal of Geophysical Research: Space Physics, https://doi.org/10.1029/2019JA026945, 2020)

—Mark Zastrow, Science Writer

Satellite Sleuthing Detects Underwater Eruptions

Tue, 03/31/2020 - 11:36

In August 2019, news media reported a new pumice raft floating in the territorial waters of the South Pacific island kingdom of Tonga. This visible evidence of an underwater volcanic eruption was borne out by seismic measurements, but conditions were less than ideal for using seismic sensors to precisely locate the source of the eruption. My colleagues and I eventually traced the source of the pumice raft to a submarine volcano referred to as “Volcano F” using a combination of satellite and seismic data (Figure 1), demonstrating remote sensing’s potential for locating and monitoring underwater volcanoes [Brandl et al., 2020].

Fig. 1. The drift of the pumice raft between 8 and 14 August 2019 following the 6–8 August eruption at Volcano F. Dots represent locations of pumice on the sea surface and other observations reported by the ROAM catamaran.

Volcanoes that breach the sea surface often provide clues to impending eruptions, and the events during and after eruptions demonstrate the hazards that marine volcanoes can pose to communities nearby. For example, after several months of growth, a large sector of the south flank of Anak Krakatau, a volcanic island situated in the Sunda Strait of Indonesia, suddenly collapsed into the sea on 22 December 2018. The resulting tsunami killed more than 430 people in nearby coastal areas of Java and Sumatra; it also injured 14,000 people and displaced 33,000. This cascade of events was not totally unexpected because the part of the island above water was clearly visible and was being monitored [Walter et al., 2019].

Unlike events above the sea surface, landslides, earthquakes, volcanic eruptions, and other geological events below sea level are seldom observed as they are happening, but they can also wreak havoc on vulnerable coastal communities. Despite the hazards they pose, assessing the natural hazard risk and mitigating the aftereffects of submarine events remain major challenges. In many cases, the events themselves are hidden beneath the water, and only their direct aftermaths are visible. Recent advances, especially in remote sensing techniques, may enable scientists to identify potential underwater hazards and areas at risk in the near future.

The Challenge of Underwater Eruptions

When cascading natural disasters occur underwater, they might not be evident until they are well under way.Landslides and earthquakes are particularly hazardous when they occur not as isolated events but as parts of cascading natural disasters. When these events occur underwater, the disaster might not be evident until it is well under way. Landslides can be directly located only if they are associated with seismicity or are not exclusively submarine. And although global seismic networks can precisely locate earthquakes, determining the details of fault motion, which can influence whether quakes trigger subsequent hazards like tsunamis, requires knowledge of the local seafloor geology and tectonic structure.

Mapping the seafloor for potential hazards will remain challenging because water rapidly absorbs the electromagnetic waves used in satellite remote sensing methods used to map land surfaces. In most cases, submarine volcanic activity thus stays obscured from our eyes. This is especially true if an eruption is effusive rather than explosive or if an eruption does not breach the sea surface to produce a detectable volcanic gas plume in the atmosphere.

Scientists currently rely on in situ methods to track floating pumice rafts, but improved Earth observation from space, coupled with automated image analysis and artificial intelligence, could further enable tracking.Visible eruptions from submerged volcanoes are the exceptions. These include silicic eruptions at island arcs, which are often explosive and eventually eject matter into the air. They also include eruptions of pumice, a highly porous, low-density abrasive volcanic rock that can float on the sea surface [Carey et al., 2018]. Large volumes of pumice can aggregate into rafts that drift with the wind, waves, and currents and that present hazards for ships. But these rafts also provide clues to recent submarine eruptions.

Scientists currently rely on in situ methods to track floating pumice rafts, but improved Earth observation from space, coupled with automated image analysis and artificial intelligence, could further enable tracking, ultimately allowing us to trace them back to their volcanic sources if weather permits.

Sourcing the Tonga Pumice Raft

During the August 2019 eruption that produced the pumice raft near Tonga, two stations of the global seismic network located far out in the Pacific Ocean on the islands of Niue and Rarotonga recorded T phases, low-frequency sound waves related to submarine volcanic eruptions. Under ideal conditions, such seismoacoustic signals can be transmitted over very long distances because they couple into a specific layer of the ocean water column, the sound fixing and ranging (SOFAR) channel, which acts as a guide for sound waves. Sound waves reach their minimum speed within the SOFAR channel, and these low-frequency sound waves may travel thousands of kilometers before dissipating. T phases from the 2011 submarine eruption of the Monowai volcanic system, for example, were transmitted in the SOFAR channel over more than 15,000 kilometers.

However, under less favorable conditions, seismoacoustic signal transmission may be more limited. The Tonga Ridge is one example of where such unfavorable conditions prevail because the ridge sits in shallow water and breaches the surface in some places, thus blocking seismoacoustic signal transmissions in some directions. During the August 2019 eruption, it was not possible to use triangulation to define the precise location of the source because only two stations recorded the relevant T phases. This difficulty clearly emphasizes the need for increased sensitivity of the global seismic network in this part of the world, which is particularly important with respect to submarine natural hazards.

Seismoacoustic signals may be directly linked to an active submarine eruption, but seismic precursor events may also hint at increasing activity within a volcanic system. In the case of the 6–8 August eruption of Volcano F, eight earthquakes of magnitude 3.9–4.7 were detected in the vicinity of the volcano in the days and hours prior to the eruption. However, given the tremendous amount of seismic activity in this area and the related mass of data under normal conditions, events of this scale usually trigger interest only when followed by a larger and more significant geohazard.

Thus, submarine volcanic eruptions may go unnoticed unless boats and ships report encountering pumice rafts or surveillance flights report visual observations of eruption plumes. In this respect, recent advances in the quality, quantity (e.g., daily coverage), and availability (e.g., the open-source data of the European Union’s Copernicus program) of satellite observations have greatly improved our ability to visually detect ongoing volcanic eruptions and their immediate aftermaths, thus representing an important addition to monitoring capabilities. Satellite data may include, among other things, visual observation of the sea surface and spectral detection of volcanic gases or temperature variations in the atmosphere.

This satellite imagery shows the sea surface on 6 August 2019 following the eruption of Volcano F. Abbreviations are UTC, coordinated universal time; Bft 5, Beaufort scale category 5 winds, corresponding to 29–38 kilometers per hour. Credit: European Space Agency, Copernicus Sentinel-2, modified by Philipp Brandl

The European Space Agency’s (ESA) Sentinel-2 satellite, for example, captured a plume of discolored convecting water, volcanic gas, and vapor about 1.2 kilometers wide coming from the shallow submarine eruption of Volcano F. By combining data from Sentinel-2, available through Copernicus, and from NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) system, we tracked the daily dispersal and drift of the related pumice raft.

Gathering Data from Many Sources

Because these satellite techniques are restricted to studying the sea surface, we may still miss many volcanic eruptions in the deep sea. Only hydroacoustic techniques deployed from ships or autonomous underwater vehicles (AUVs) are capable of surveying the ocean floor at needed resolutions, so increased marine research focused on rapid response to submarine eruptions and landslides could strengthen our ability to predict potential natural hazards in the deep sea.

Ship-based multibeam mapping of submarine volcanoes can help constrain eruption dynamics and volume and monitor morphological changes of volcanic edifices during or after an eruption.Ship-based multibeam mapping (which can achieve resolutions down to about 15 meters) of submarine volcanoes can help constrain eruption dynamics and volume and monitor morphological changes of volcanic edifices during or after an eruption. And developments in robotic technology for seafloor mapping, such as unmanned surface vehicles and improved AUVs, which could extend resolution to less than 1 meter, may soon lead to significant advancements in our marine remote sensing capabilities. But currently, the limited coverage of these techniques—less than about 30% of the ocean floor has been mapped by ship-based multibeam sonar—means that only a few areas exist where repeated multibeam surveys allow us to analyze changes in bathymetry over time.

Several segments of the East Pacific Rise, of the Galápagos Spreading Center, and of the Juan de Fuca Rise are examples of areas where detailed bathymetric maps have been used to monitor volcanic activity. In the southwestern Pacific, well-mapped areas include arc volcanoes such as those in the Tofua-Kermadec Arc, the Monowai Volcanic Center, the Havre and Brothers volcanoes, and West Mata. Repeated phases of growth and partial collapse of the edifice of the Monowai arc volcano have been well monitored [Watts et al., 2012]. However, this level of monitoring has been possible only through repeated bathymetric surveys (1978, 1986, 1998, 2004, 2007, and 2011) that together integrate to an important time series.

During a cruise in 2018, my colleagues and I “accidentally” mapped the flanks of Volcano F (it was not the focus of our cruise). By combining our data with preexisting data from an Australian cruise, we created a combined bathymetric map (Figure 2) that could serve as a basis for future changes in bathymetry due to volcanic activity [Brandl et al., 2020].

Fig. 2. Composite bathymetry of Volcano F from ship-based multibeam data collected by R/V Sonne cruise SO267 and R/V Southern Surveyor cruise SS2004/11.

At present, the risk potential of cascading events in the submarine realm is poorly understood, mainly because of the lack of data and monitoring. Studies like those described above would be of great value in assessing the risks of cascading natural disasters elsewhere—for example, at the many arc volcanoes whose edifices are composed of poorly consolidated volcaniclastic material rather than of solid masses of rock. Volcanic growth can lead to a buildup of material that if followed by partial sector collapse, can trigger a tsunami—this was the case at Anak Krakatau in 2018.

Emerging technologies such as artificial intelligence and machine learning could fill an important gap. Proactive automated processing of data from global seismic networks could help to identify clusters of increased seismicity that could be precursors to volcanic eruptions. The locations and timing of these clusters could then be used to pick out features in hydrophone data from the same times and places that correlate with submarine eruptions. Earth and computer scientists are currently developing techniques for automated image analysis and data processing as well as the use of artificial intelligence for pattern recognition and the proper identification of submarine volcanic eruptions.

Moving Beyond Accidental Discovery

Currently, submarine eruptions from island arc volcanoes and mid-ocean ridges are observed mainly by accident or when their eruption products breach the sea surface. Thus, we likely never see a significant proportion of submarine volcanic eruptions. And we lack the ability to monitor submarine volcanic activity on a global scale, which limits our ability to assess risks related to underwater volcanic eruptions, sector collapses, and cascading events.

Compiling existing data and collecting new data related to submarine volcanic activity in a dedicated open-access database should help researchers estimate risk potentials as the first step toward forecasting natural hazards.Remote sensing techniques that collect data from space and at sea may provide us with more powerful tools to detect and monitor this volcanic activity and to project associated risks in remote areas. Recent advances in data processing may also greatly improve capabilities in this field. And compiling existing data and collecting new data related to submarine volcanic activity in a dedicated open-access database should help researchers estimate risk potentials as the first step toward forecasting natural hazards.

The experience with the 2019 eruption of Volcano F shows how important the integration of open-source and interdisciplinary remote sensing data is for the monitoring and management of natural hazards.

Trees Are Watching Us and Our Actions

Tue, 03/31/2020 - 11:30

The annual growth of trees through photosynthesis is demarcated in seasonal growth rings put on in their stems. Rind width and composition provide clues about the conditions under which that individual grew. These “tree rings” have been used for decades to reconstruct past climates and extreme events. However, there is more to the story.

Scanlon et al. [2020] discover that the concentration of mercury in decadal increments can be used to reconstruct atmospheric mercury in a set of trees in Virginia, USA. Using concentration observations, the researchers found that mercury concentrations in tree rings peaked in the 1930s–1950s while global atmospheric mercury continued to rise. Mercury stable isotopes reveal that this local peak was linked to a local pollution source, most likely from a nearby industrial plant that manufactured the synthetic fabric rayon.

This study is the first attempt to analyze and interpret mercury isotopes in tree rings. The findings open the doors to new analytical approaches to tease out the stories hidden in tree rings about the history of human industrial activity and its impact on the biosphere.

Citation: Scanlon, T. M., Riscassi, A. L., Demers, J. D., Camper, T. D., Lee, T. R., & Druckenbrod, D. L. [2020]. Mercury accumulation in tree rings: Observed trends in quantity and isotopic composition in Shenandoah National Park, Virginia. Journal of Geophysical Research: Biogeosciences, 125, e2019JG005445. https://doi.org/10.1029/2019JG005445

—Ankur Rashmikant Desai, Editor, JGR: Biogeosciences

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