Geodesyʼs Changing Shape from Space-Based Earthquake Prediction to Relativistic Measurements, Geodesists Are Creating a Dynamic Future for Their Field

VOL. 101 | NO. 1 Grand Theft Galaxy JANUARY 2020 Honors Nominations How-To Guide A Sweeping Arctic Survey

Geodesyʼs Changing Shape From space-based earthquake prediction to relativistic measurements, geodesists are creating a dynamic future for their field. AGU Bridge Program Advancing the Earth and space sciences through increased representation of Hispanics, African Americans, and Native Americans in geoscience graduate programs in the U.S.

The student application period is now open. Apply Today.

agu.org/bridge-program FROM THE EDITOR Editor in Chief Heather Goss, AGU, Washington, D.C., USA; [email protected] Editorial Manager, News and Features Editor Caryl-Sue Micalizio The Shape of the World Science Editor Timothy Oleson Senior News Writer Randy Showstack News Writer and Production Associate Kimberly M. S. Cartier s we begin year 101 here at AGU, let’s go back to the News and Production Fellow Jenessa Duncombe fundamentals. In fact, let’s start with a single stone atop a hill in Hanover, Germany. In 1818, Carl Friedrich Production & Design A Manager, Production and Operations Faith A. Ishii Gauss used this triangulation stone to create a geodetic survey Senior Production Specialist Melissa A. Tribur of the city. Today it serves as inspiration to Jakob Flury, who Editorial and Production Coordinator Liz Castenson lives about an hour’s walk from this monument to his profes- Assistant Director, Design & Branding Beth Bagley sion. Senior Graphic Designer Valerie Friedman Graphic Designer J. Henry Pereira “It’s really a new world,” Flury says in the story on p. 18 (“Einstein Says: It’s 309.7-Meter O’Clock”). “This four- Marketing dimensional reality, this curved space-time” is our post- Director, Marketing, Branding & Advertising Jessica Latterman Einstein world, and Flury is part of a new movement to cham- Assistant Director, Marketing & Advertising Liz Zipse pion relativistic geodesy. Atomic clocks are going to give us an Marketing Program Manager Angelo Bouselli Senior Specialist, Digital Marketing Nathaniel Janick entirely new perspective—down to the millimeter, perhaps— Digital Marketing Coordinator Ashwini Yelamanchili on the shape of our world. Geodesy, of course, was one of the original seven sections formed when AGU was founded Advertising in 1919, along with seismology, meteorology, terrestrial magnetism and electricity, oceanog- Display Advertising Dan Nicholas [email protected] raphy, volcanology, and geophysical chemistry. Like most fields, geodesy has evolved from Recruitment Advertising Heather Cain using simple—though revolutionary—apparatuses on the ground to sophisticated instru- [email protected] ments in low-Earth orbit. (Searching our Fall Meeting 2019 scientific program for “satellite Science Advisers AND geodesy” brings up more abstracts than one person could get through if the conference Geomagnetism, Paleomagnetism, Julie Bowles lasted a month.) and Electromagnetism On the cutting edge of space geodesy are Timothy Melbourne and his colleagues, the sub- Space Physics and Aeronomy Christina M. S. Cohen Cryosphere Ellyn Enderlin jects of our January cover story. They’re using satellite navigation systems to make real-time Study of the Earth’s Deep Interior Edward J. Garnero measurements along shifting faults. With these systems expanding and offering continuous Geodesy Brian C. Gunter telemetry, scientists are now able to see real-time ground movement within a few centime- History of Geophysics Kristine C. Harper ters. The potential to use this monitoring to calculate whether an earthquake will be magni- Planetary Sciences Sarah M. Hörst Natural Hazards Michelle Hummel tude 7 or magnitude 9 almost as soon as the ground begins to shake could offer alerts to peo- Volcanology, Geochemistry, and Petrology Emily R. Johnson ple in the region that could save their lives. Read more about this work in “Seismic Sensors in Seismology Keith D. Koper Orbit,” p. 32. Tectonophysics Jian Lin Near-Surface Geophysics Juan Lorenzo Elsewhere in the issue, we hear from scientists also interested in the effects of gravity in Earth and Space Science Informatics Kirk Martinez space. Tidal heating, write Alfred McEwen and his colleagues, is key to understanding the way Paleoceanography and Paleoclimatology Figen Mekik planets and moons form. McEwen walks us through the history of our understanding of the Mineral and Rock Physics Sébastien Merkel Ocean Sciences Jerry L. Miller Jovian system from Pierre- Simon Laplace’s resonance discovery in 1771 to Voyager 1’s 1979 Global Environmental Change Philip J. Rasch observations and up to today, as scientists eagerly await two important space missions that Education Eric M. Riggs could finally reveal answers to a litany of questions, including “Does Io Have a Magma Ocean?” Hydrology Kerstin Stahl Tectonophysics Carol A. Stein (p. 24). Atmospheric Sciences Mika Tosca Finally, it’s January: Have you submitted your nomination for AGU Union awards, medals, Nonlinear Geophysics Adrian Tuck and prizes yet? We want to hear about your peers who have made outstanding contributions Hydrology Adam S. Ward Earth and Planetary Surface Processes Andrew C. Wilcox to Earth and space science through scientific research, education, science communication, Atmospheric and Space Electricity Yoav Yair and outreach. We also want to do better in recognizing excellence through more equal repre- GeoHealth Ben Zaitchik sentation. AGU has come a long way in that respect (“AGU Makes Strides in 2019 Union Awards, Societal Impacts and Policy Sciences Mary Lou Zoback Medals, and Prizes,” p. 38), but we will continually look for ways to do better. We’re grateful to Allison Jaynes and her colleagues, who have developed and shared with us an easy to follow ©2020. AGU. All Rights Reserved. Material in this issue may be photocopied by guide, “Equal Representation in Scientific Honors Starts with Nominations,” p. 16. We urge individual scientists for research or classroom use. Permission is also granted to use short quotes, fi gures, and tables for publication in scientifi c books and you to take a look and submit your nominations at honors . agu . org by 15 March. journals. For permission for any other uses, contact the AGU Publications Offi ce. At the start of our second century together, let’s take a moment to truly assess the shape of Eos (ISSN 0096-3941) is published monthly by AGU, 2000 Florida Ave., NW, Washington, DC 20009, USA. Periodical Class postage paid at Washington, D.C., our world. and at additional mailing offi ces. POSTMASTER: Send address changes to Member Service Center, 2000 Florida Ave., NW, Washington, DC 20009, USA Member Service Center: 8:00 a.m.–6:00 p.m. Eastern time; Tel: +1-202-462-6900; Fax: +1-202-328-0566; Tel. orders in U.S.: 1-800-966-2481; [email protected]. Submit your article proposal or suggest a news story to Eos at bit.ly/Eos-proposal. Views expressed in this publication do not necessarily refl ect offi cial positions of AGU unless expressly stated. Heather Goss, Editor in Chief Christine W. McEntee, Executive Director/CEO

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24 32 Features

Cover Story 18 Einstein Says: It’s 309.7-Meter O’Clock 32 Seismic Sensors in Orbit By Bas den Hond

By Timothy I. Melbourne et al. Atomic clocks are now so accurate that Earth’s gravity can be seen to slow them down. Geodesists Navigation satellites are enabling high-precision, real- are preparing to use this relativistic effect to measure time tracking of ground displacements, supplementing elevation. traditional methods for monitoring and assessing earthquakes. 24 Does Io Have On the Cover a Magma Ocean? A continuously telemetered GNSS station in Washington state. By Alfred McEwen et al. Credit: Central Washington University Future space missions will further our knowledge of tidal heating and orbital resonances, processes thought to create spectacular volcanism and oceans of magma or water on other worlds.

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9 38

12 41 Columns

From the Editor AGU News 1 The Shape of the World 38 AGU Makes Strides in 2019 Union Awards, Medals, and Prizes News 4 Modeling How Groundwater Pumping Will Affect Research Spotlight Aquatic Ecosystems 39 Capturing Snowmelt Patterns from Cloudy 5 Sparks May Reveal the Nature of Ash Plumes Satellite Images 7 Peatlands Are Drying Out Across Europe 40 Soil Moisture Drives Great Plains Cloud Formation 8 Wanted for Grand Theft Galaxy: The Milky Way 40 The When and Where of Mesospheric Bores Revealed 9 How Do Submarine and Terrestrial Canyons Compare? 41 Earthquake Statistics Vary with Fault Size 10 New Type of Storm Spotted on Saturn 41 Atlantic Circulation Consistently Tied to Carbon Dioxide 11 Climate Change Will Make Us Sicker and Lose 42 Treating Colloids as Clusters Better Predicts Work Hours Their Behavior 12 Giant Geode Grew Slow and Steady 43 How Forest Structure Influences the Water Cycle Opinion Positions Available 13 Addressing Arctic Challenges Requires 44 Current job openings in the Earth and space sciences a Comprehensive Ocean Survey 16 Equal Representation in Scientific Honors Postcards from the Field Starts with Nominations 49 Dangling from a crane 45 meters above the forest floor, researchers collect gas exchange data from mature trees in Panama.

AmericanGeophysicalUnion @AGU_Eos company/american-geophysical-union AGUvideos americangeophysicalunion americangeophysicalunion

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Modeling How Groundwater Pumping Will Affect Aquatic Ecosystems

with surface water. But these models work at the level of individual catchment areas. “This is the first study I’ve seen that models groundwater–surface water interactions on a global scale over timescales relevant to man agement or planning,” said Audrey Sawyer, a hydrogeologist at the Ohio State University who was not involved in the study. “The results provide a great road map for identify ing areas that need higher -resolution models and more observations.” To build a global-scale hydrological model that simulates when loss of groundwater con tributions will cause streamflows to fall below levels needed to sustain aquatic life, de Graaf leaned on existing models. These included the PCRaster Global Water Balance model 2 (PCR- GLOBWEB 2; bit . ly/ water -model), developed at Utrecht University, and the U.S. Geological Sur vey’s modular hydrologic model (MODFLOW; bit . ly/ USGS -model). PCR -GLOBWEB 2 simu lates moisture storage and exchange between atmospheric, surface, and groundwater res ervoirs and accounts for water demands from agriculture, animal husbandry, household use, lmost 30% of Earth’s freshwater sup large amounts of groundwater are used for and industry. MODFLOW predicts ground ply lies hidden from view as ground irrigation, such as the upper Ganges and water status and groundwater– surface water A water. These waters, though mostly Indus basins on the Indian subcontinent. But interactions. invisible, are vital for us humans. Ground groundwater pumping has also affected river As inputs for the model, de Graaf used his water provides about half the global supply of flow in other locations, including parts of the torical data on groundwater demand and drinking water and is used to grow the major northeastern United States and Argentina. extraction from 1960 to 2010. She assumed ity of the world’s irrigated crops. Technically, groundwater is a renewable that groundwater use after 2010 would remain Groundwater is also an inextricable cog in resource, but unsustainable rates of ground mostly constant through 2100, increasing the global water cycle. In many areas, dis water extraction can deplete reserves faster only in response to irrigation needs as a result charge from groundwater replenishes than they can be replenished by rain, snow, of climate change. The model also accounted streams and rivers, helping sustain aquatic or surface waters. As groundwater levels drop, for different scenarios of climate change ecosystems. Many of these ecosystems are streams, rivers, and the aquatic ecosystems based on the Representative Concentration now under threat, according to a new study. dependent on these waters can suffer tre Pathway 8.5 scenario from the Intergovern Inge de Graaf, a hydrological environmen mendous, and sometimes irreversible, losses. mental Panel on Climate Change to simulate tal systems researcher at the University of changes in precipitation due to climate Freiburg, and colleagues simulated on a global Building a Global Groundwater Model change (bit.ly/IPCC-pathway). scale how current rates of groundwater Several existing hydrological models simulate extraction will affect surface streams and riv the flow of groundwater and its interactions Determining When Streamflow ers and the ecosystems associated with them. Hits Critical Levels “Almost 20% of the regions where ground The model incorporates a previously defined water is pumped currently suffer from a standard that to maintain healthy ecosys reduction of river flow, putting ecosystems at “We expect that by 2050 tems, groundwater extraction should not risk,” de Graaf wrote in a recent blog post. lower the natural monthly flow of a stream by “We expect that by 2050 more than half of the more than half of the more than 10% over a period of time. Streams regions with groundwater abstractions will regions with groundwater naturally ebb and rise over time, but using this not be able to maintain healthy ecosystems” standard, de Graaf calculated the low-flow (bit.ly/water-underground). abstractions will not be index, a value that represents the ground Areas already at risk include regions with able to maintain healthy water discharge needed to maintain at least relatively dry climates, such as the High the minimum natural streamflow necessary

Plains of the United States, and places where ecosystems.” to sustain aquatic life in different streams. Opposite: ADra gan iStock.com/

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Streamflows were assumed to reach critically low levels if monthly flow was 10% below the Sparks May Reveal the Nature low-flow index for more than 3 months of a year for 2 consecutive years. of Ash Plumes However, groundwater levels and stream flows can be affected by more than ground water extraction. Climate change, for exam ple, can also affect both. To distinguish between alterations to streamflow driven by climate change alone and those caused by cli mate change and groundwater pumping, de Graaf ran simulations from 1965 through 2099 that either included groundwater and surface water use by humans or were “natural runs” that excluded human activity. Flow limits reached under both conditions were excluded because they could not be attributed solely to groundwater pumping.

“Only a small drop of groundwater level will already cause these critical river flows.” Visible volcanic lightning can occur throughout an ash plume, like this bolt above Eyjafjallajökull in Iceland, in 2010. Invisible sparks may occur in the low-pressure region of standing shock waves formed in the near-vent region. Credit: Sævar Helgi Bragason, CC BY-NC-ND 2.0 (bit.ly/ccbyncnd2-0) Using results from the model, de Graaf estimates that by 2050 streamflows will be affected in the majority of watersheds world wide, sometimes even before major ground hake up a bottle of soda, open it, and flights across Europe and North America. The water loss. “Only a small drop of groundwater you’ll see a plume of explosive gas, Icelandic volcano is far from the only plume level will already cause these critical river Ssugar syrup, and flavoring spew into producer: There are about 1,500 active volca flows,” de Graaf wrote. “Moreover, the the air. The culprit? Gases and ejecta suddenly noes around the world. impact of groundwater pumping will often allowed to escape the high pressure inside the “Ash can damage turbines of planes and become noticeable after years or decades. bottle. also affect visibility,” said Jens von der Lin This means that we cannot detect the future Scale up this experiment, add some molten den, a physicist at Lawrence Livermore impact of groundwater pumping on rivers rock, and you have a pressure release that National Laboratory and lead author of the from the current levels of groundwater shoots gases, ash, and lava into the sky. Ash new research. “It’s very hazardous for com decline. It really behaves like a ticking time plumes can drift through the atmosphere, mercial aviation to fly through areas that may bomb.” spreading volcanic shards far from their have ash.” Results from de Graaf and her team’s source. He explained that because of the danger research were published in Nature (bit .ly/ Although volcanic eruptions can’t be pre there’s interest in understanding how much groundwater-pumping). dicted, a group of scientists is trying to fore ash is ejected and where weather patterns The global scale of the model makes it “a cast the characteristics of ash released in the might carry it. great starting point for identifying water dark plume of debris. At the American Phys sheds and regions where we need more sur ical Society’s annual meeting last October, face water and groundwater data and higher- researchers presented a way to relate radio resolution models,” Sawyer said. But the frequency measurements of volcanic near- It wasn’t just the different scale of the model also means that “we need vent discharges to the ash that’s ejected. to follow up with observations and more Their work can be used in volcano moni shape of Mach disks that refined models relevant to the scale of land toring, especially when it comes to volcanic caught the researchers’ eye. use planning and ecosystem processes.” hazards. They observed sparks near Atmospheric Ash the volcanic vent, outlining By Adityarup Chakravorty (chakravo@ gmail The 2010 Eyjafjallajökull volcanic eruption

Opposite: ADra gan iStock.com/ .com), Science Writer disrupted air travel for 6 days, grounding the shock wave surface.

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“We could potentially use nic vent. And although shock waves often propagate outward and move, the waves lightning observations as a move in such a way that a standing shock proxy for the duration of wave, or Mach disk, forms. Researchers created a model, simulation, and experiment of volcanic sparks and shock waves during an ash venting, or perhaps the Lightning and Ash eruption. (a) The model showing the standing shock density or size distribution Corrado Cimarelli, one of the group’s collab wave surface, or Mach disk, is indicated in red. The orators, had previously noticed in laboratory sparks occur within the low- pressure region inside the of ash particles.” experiments that discharges occur below a Mach disk boundary. (b) In this simulation of the gas flat surface formed by a Mach disk. The team outflow speeds, speeds drop at the shock surface, pil- modeled how ash might affect the Mach disk ing up gas and increasing pressure. (c) In the experi- and compared the results with the shock tube ment, sparks form below the Mach disk surface while experiments. upper sparks mark out the shock surface. Credit: Jens Von der Linden and his colleagues want to They found that the amount and type of von der Linden et al. (a and b); Clare Kimblin and Ian make better early predictions of ash content ash had different effects on the Mach disk. McKenna, Special Technology Laboratory, Mission after an eruption. To do this, they decided to “You still get a shock surface, but it’s thinner Support and Test Services (c) use a scaled-down lab-created version of a and at a lower height,” said von der Linden. volcanic eruption: shock tube experiments “The concept of a standing shock wave ejecting ash into a large expansion chamber isn’t new, but doing modeling to see how ash where discharges occur. affects the shock is new,” said Sonja Behnke, Behnke said that “lightning observations “[Researchers] have a high-pressure tube a remote sensing scientist at Los Alamos may be able to quantify the height, width, and that they fill with gas, a high-pressure gas, National Laboratory who was not involved in lifetime of a standing shock wave,” all of and they can also put ash, particles, or glass the study. “Jens is the only one I know of which are useful for volcano monitoring. beads in it,” explained von der Linden. During doing this work.” a simulated eruption, the gas and particles But it wasn’t just the different shape of Measuring Mach Disks burst from the tube into a lower-pressure Mach disks that caught the researchers’ eye. “The near-vent region of a volcano is very expansion chamber. They observed sparks near the volcanic vent, hard to diagnose,” said von der Linden. “It’s The setup mimics what happens in a vol outlining the shock wave surface. Although very hot, rocks are flying through there—it’s canic eruption. “It’s like a rock conduit; ini the sparks look like lightning bolts we see in very hard to access it.” He noted that pairing tially, there was a rock blocking the high- the sky, they might not be the type of light his team’s modeling work with antenna field pressure gases that were building up in a ning we’re familiar with. monitoring could triangulate where the spark volcano,” he said. Suddenly that rock bursts, “We’ve never actually seen the near-vent signals are coming from. and “the gas and ash of the volcano are mov discharge [in nature], this nonlightning Behnke agreed that much more work will ing up this rock conduit, where it expands discharge, because it’s probably not bright need to be done to tease out the details of vol into the atmosphere.” enough and the plume is too dark to canic ash in shock waves. “It isn’t clear what This sudden change in pressure from high look through,” said von der Linden. “But the difference might be between the labora to low creates a shock wave above the volca we know from the radio frequency signa- tory sparks and what we see in an eruption,” tures that it exists she said. and it’s very dif- “It will be critical to compare the modeling ferent from light work to field observations of volcanic light ning, because the ning,” Behnke noted. “Laboratories are very [sparks] only have different than nature.” high-frequency Understanding the characteristics of ash is components.” important in aviation, said von der Linden. He Behnke said that stressed that their method “isn’t predicting vent discharges are ruptures, but it’s predicting right when erup very small electri- tion occurs.” cal discharges, or “This work is showing that in the future, sparks, that occur we could potentially use lightning observa at a volcano’s vent tions as a proxy for the duration of ash vent at the same time as ing, or perhaps the density or size distribution an explosive erup of ash particles,” said Behnke. tion. “They aren’t She added that the approach could be very lightning - “used by volcano observatories to model the like,” she added, plume from an eruption and better forecast “because they are ash hazards.” very small—maybe a few meters, but we don’t know for By Sarah Derouin (@Sarah_Derouin), Science sure.” Writer

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Peatlands Are Drying Out Across Europe

eatlands are some of the world’s largest reservoirs of soil carbon, but new Presearch finds that in Europe they are drying out, putting them at risk of turning from carbon sinks to carbon sources. These wetlands are vitally important for carbon storage, holding roughly 30% of global soil carbon, despite covering only around 3% of Earth’s surface. It is their saturated sur face conditions that make peatlands such effective carbon stores. When peat mosses die, they sink into this wet environment, and the low-oxygen, often acidic conditions pre vent microbes that decompose plant litter elsewhere from working effectively. Instead of breaking down, the dead mosses slowly build up, trapping underground the carbon dioxide that they sucked out of the atmo sphere during photosynthesis. Most European peatlands, like this one in Ireland, are drier now than they have been in hundreds of years. But a new study suggests that in Europe, Credit: iStock.com/w-ings peatland water tables are falling. In the jour nal Nature Geoscience (bit. ly/drier -peatlands), researchers from almost 30 institutions report that 60% of the 31 peatlands they stud Sixty percent of the peatlands is moving away from natural base ied were drier between 1800 and 2000 than at lines, according to the study authors, with any point in the past 600 years. And 40% were peatlands studied were the change linked to climate change and drier than they had been for 1,000 years, drier between 1800 and human activities, such as cutting, drainage, whereas 24% were drier than they had been burning, and grazing. However, Morris said, for 2,000 years. 2000 than at any point in “We think this is driven principally by warm the past 600 years. ing.” From Sink to Source? Zicheng Yu, a paleoecologist at Lehigh Uni This finding is concerning because if peat versity in Bethlehem, Pa., believes the study lands dry out, microbial activity could is impressive and important, as “it shows increase and shift them from carbon sinks to consistent continent-wide change in hydro carbon sources, with global consequences for bas from cores taken from peatlands with logical conditions on peatlands.” climate change. different environmental conditions allowed But Yu questions the idea that as water “If we allow peatlands to dry out, as they the researchers to determine the water tables tables drop, these peatlands will release more appear to be doing, then the carbon stocks that of the past. carbon, because even though the idea is they have built up over the last 10,000 to Morris said that across Europe, there are sound in theory, there are currently no long- 12,000 years might be at risk,” explained Paul three distinct regions where, historically, the term data from these sites showing that this Morris, an ecohydrologist at the University of peatlands have behaved differently: Great happens. Instead, drying could simply lead to Leeds in the United Kingdom. Britain and Ireland, Scandinavia and the a change in the plant community to species To reconstruct the historic water levels of Baltic states, and continental Europe. But that prefer a lower water table but “may still Europe’s peatlands, Morris and his col recently, that has changed. “In the sequestrate carbon at the same rate,” he leagues turned to testate amoe- last 200 to 300 years, the con explained. bas. These single-celled, soil- sistent change that we see Indeed, another recent study found that dwelling creatures have very between all of these three peat moss species have different tolerances specific tolerances for how regions is that everything for warming and drying and that species wet their environment can is getting dry,” Morris composition could change as conditions shift, be. Comparing fossil amoe said. “Almost all of our helping some peatlands hold on to their car sites are getting drier. bon (bit.ly/peatland-carbon). It’s the only time when A useful next step would be assessing how The tiny shells of amoebas simi- the record starts to agree carbon sequestration changes in these peat lar to this one helped researchers across the whole conti lands as they dry, Yu said. measure the environmental quality nent.” of European peat bogs. Credit: The findings suggest that Picturepest, CC BY 2.0 (bit.ly/ccby2-0) the wetness of many European By Michael Allen, Science Writer

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Wanted for Grand Theft Galaxy: The Milky Way

Magellanic Cloud, Jahn said. Galaxies similar to the Milky Way have only about double the number of such satellites, even though the Milky Way is 10 times larger than the LMC.

Cosmological Questions “Some of the most interesting outstanding questions in cosmology and structural forma tion are small-scale cosmological questions,” Jahn said. One such question is how to resolve the missing-satellites problem, the discrepancy between the high number of satellite galaxies predicted by simulations to orbit the Milky Way and the lower number of satellites observed. By looking at satellite galaxies of the Large Magellanic Cloud, the recent study explores similar questions from “one step A visualization of the study’s simulations, with dark matter shown at center (in white) and a galaxy similar to the down,” Jahn said. Large Magellanic Cloud (along with stars and gas) shown at bottom right. Also pictured are multiple companion “This study is a very nice update from pre galaxies. Credit: Ethan Jahn, University of California, Riverside vious work that looked at the abundance of satellites around LMC-mass galaxies using just dark -matter-only simulations,” said Ekta Patel, a fellow at the University of Cali n a case that’s outside the jurisdictions of fornia, Riverside and the lead author on the fornia, Berkeley’s Miller Institute for Basic earthly courts, the Milky Way has been study. Research in Science. She wasn’t involved with Iaccused of stealing from one of its closest Eight additional dwarfs appear to have a the study. neighbors and satellite galaxies, the Large history of orbiting the Large Magellanic “Since the FIRE simulations encompass a Magellanic Cloud (LMC). Instead of taking Cloud, but additional work is needed to con fully hydrodynamical model, these results cars or garden gnomes, however, the Milky firm these possible relationships, researchers provide a rigorous study of the subhalos and Way likely stole several small galaxies. noted. corresponding galaxies that survive when In a study published in Monthly Notices of baryons are added. This reduces some of the the Royal Astronomical Society, researchers Gaia Data and FIRE Simulations uncertainty that can arise when neglecting assert that two classical dwarf galaxies— The researchers’ calculations are based on baryonic processes such as feedback, the Carina and Fornax—are “consistent with the publicly available proper motions data from effect of reionization, gas hydrodynamics, LMC system by our calculations of angular the European Space Agency’s Gaia mission, and tidal effects from the disk of the host gal momenta” (bit.ly/LMC-galaxies). In addi Jahn said. Gaia collected the most accurate axy,” Patel added. tion, the team’s analysis bolsters the findings position and velocity data of any satellite to She’s currently working “to confirm of previous studies indicating that several date—“state-of-the-art data,” he added. whether the satellites suggested to be satel ultrafaint dwarf galaxies show signs of pre The researchers compared these data with lites of the LMC in this study have orbital his vious associations with the Large Magellanic “a sample of five cosmological zoom-in sim tories that are suggestive of true satellites…. Cloud. ulations of LMC-mass host galaxy systems” This work looks mainly at the orbital poles of In total, there are seven small galaxies cur from the Feedback in Realistic Environments such galaxies only today and compares the rently associated with the Milky Way, includ (FIRE) project. FIRE’s zoom-in approach real abundances to the abundances of satel ing the Small Magellanic Cloud, that enables researchers to create high-resolution lites in simulations of the LMC. I think my researchers have confirmed once orbited the galaxy formation simulations that can grap study will be complementary and not com Large Magellanic Cloud. Remarkably, until ple with complex physical effects that elude petitive since it uses a different approach, but recent years, the Small Magellanic Cloud was other simulations, Jahn said. we are targeting a similar question.” the only known satellite of its larger counter FIRE simulations predicted the presence of Jahn plans to use new simulations to part, according to Ethan Jahn, a graduate stu between 5 and 10 luminous satellite galaxies explore additional questions about satellites dent of astronomy at the University of Cali orbiting hosts with the mass of the Large of the Large Magellanic Cloud, such as how they form and under what conditions they stop forming stars.

u Read the full stories and the latest news at Eos.org By Rachel Crowell (@writesRCrowell), Science Writer

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How Do Submarine and Terrestrial Canyons Compare?

ecause Earth’s land and submarine Researchers used open- degree committee.) “Hopefully, this kind of canyons look similar, researchers have approach will further convince the global Btraditionally surmised that they source multibeam sonar research community of the importance of formed through similar processes. Evaluating data, along with acquiring more high-resolution bathyme that assumption has proven difficult, how tries from more submarine systems.” ever, due largely to lack of data. “Scientists topographic data, to have more high-resolution imagery of the compare canyons on land Looking Ahead surface of Mars than of Earth’s ocean floor,” The recent work “gives us the ability to effec according to a recent statement released by and underwater. tively fingerprint different drainage sites,” Stanford University announcing new research including extraterrestrial sites, Dobbs said. on the subject. This type of fingerprinting could serve as a Stephen Dobbs, a Ph.D. candidate in geo proxy for studying how the canyons, chan logical sciences at Stanford, explained the nels, and other features found on Mars’s shortage of high-resolution imagery and data On land, significant changes in canyon landscape formed. for submarine canyons. Whereas orbiting shape are often triggered by large flood events New insights about canyon formation are satellites can readily collect high-resolution or landslides. Under water, the processes that also useful back on Earth, of course. topographic data of Mars, similar satellites form canyons may be periodic landslides from “The full exploration of concavity factor for can collect bathymetric data for Earth’s extreme steepness, seismic activity, or large a large subset of canyons yields another oceans on only about a kilometer scale of res winter storms that funnel sediment from the important difference between terrestrial and olution. Laborious and expensive processes shallow continental shelf, researchers marine systems,” Smith said. “It’s very requiring the use of ships and autonomous explained in a statement. exciting to see this particular detail come into underwater vehicles must often be used to “I think this study does a very nice job of focus, and [I] hope more people get involved image the seafloor, he added. concisely testing and expanding the quanti with the overall inquiry about marine incision As detailed in a new study published in tative approach to submarine channel net in the future. To me, marine geomorphology Geology, Dobbs and his collaborators used works. I’m pleased that these questions are is as exciting, or even perhaps more so, [as] open-source multibeam sonar data, along becoming more tractable and am intrigued the exploration of Mars.” with topographic data, to compare land and by the results,” said Michael Elliot Smith, an underwater canyons (bit. ly/land -underwater associate professor at Northern Arizona Uni -canyons). The study came out of a student- versity in Flagstaff. (Smith wasn’t involved By Rachel Crowell (@writesRCrowell), Science run seminar directed by George Hilley, a tec in this study but was on Dobbs’s master’s Writer tonic geomorphologist, and Tim McHargue, a deepwater sedimentologist and marine geol ogist, both also at Stanford.

Deciphering Differences “The qualitative resemblance between ter restrial and submarine channels has led to instinctive assumptions about the similarity of the processes that form them,” said Charles Paull, a senior scientist at the Mon terey Bay Aquarium Research Institute in Cal ifornia. Paull was not involved in the new study. However, the study’s results tell a different story. “The paper shows for the first time that there are fundamental differences between the processes that form [terrestrial and sub marine canyons],” Paull noted. In the new study, researchers compared the channel concavity and steepness indices of 23 terrestrial and 29 submarine catchments. Overall, the concavity indices were lower for submarine canyons than for those found on land. In addition, the tributaries in submarine formations were steeper than their associated main stem, but land-based tributaries and The dark area, nicknamed the “Tongue of the Ocean,” is part of the Great Bahama submarine canyon. Credit: main stems were similarly steep. Earth Science and Remote Sensing Unit, NASA Johnson Space Center

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New Type of Storm Spotted on Saturn

colored stripe near the north pole. The band persists today, even though the last storm disappeared in October 2018. “This is something entirely new,” said Agustin Sánchez-Lavega, a planetary scien tist at University of the Basque Country in Spain. He is the lead author of a study pub lished in Nature Astronomy describing the event (bit.ly/Saturn-storm). Sánchez-Lavega highlights the contribu tion of amateur astronomers to this discov ery. His university hosts a website called Planetary Virtual Observatory and Laboratory, where amateurs can contribute their plane tary observations for research purposes (bit In 2018, a new type of storm appeared on the surface of Saturn. The first storm (above) appeared as a white .ly/amateur-astronomers). blemish near the north pole of the planet, growing to a size of 2,000 kilometers across in just a few days. A sec- In this case, the first indication that some ond storm appeared about 2 months later. Credit: NASA/ESA thing was happening in Saturn’s atmosphere came from an image captured by an amateur astronomer in Brazil. “As soon as I saw it, I knew it could be interesting, and we issued an f we look past Saturn’s rings, we see that the pair. Each storm appeared slightly to the alert for our community of amateur astrono the planet’s surface has few distinctive north of the preceding one. mers observing the gas giants,” explained Ifeatures. Most of the planet is made of The storms moved at different speeds, Sánchez-Lavega. “This is very important hydrogen, helium, and such trace elements probably under the influence of the local because, thanks to them, we have daily images as ammonia, methane, and water, which cre winds at their respective latitudes. This showing how the storm system has evolved.” ate the planet’s visible bands and clouds. caused several close encounters. Every time Sánchez-Lavega and his team also gath Occasionally, however, Saturn’s surface they got close, the storms seemed to disrupt ered observations from the Hubble Space lights up a bit with bright white spots. These each other, causing them to sprout filaments Telescope and the 2.2-meter telescope in are storms, formed when water clouds in the that filled with dark and bright orbs, probably Calar Alto, Spain. They were also able to use inner layers of the atmosphere—200 kilome eddies that offered a brief glimpse at the images from Cassini, which crashed onto Sat ters below the visible surface—heat up and lower layers of the atmosphere below the urn in September 2017 but had imaged the rise, much like a summer storm anywhere on clouds. The first storm to appear was the lon cyclonic vortex where the first storm origi Earth but on a larger scale. gest lived, lasting for 214 days and reaching a nated. “This is a very unusual spot for a storm Until recently, researchers had observed maximum size of 4,000 kilometers across. to originate,” Sánchez-Lavega explained. just two types of Saturnian storms. The small These interactions eventually altered an The team members also used computer sim ones, typically 2,000 kilometers in diameter, entire latitudinal band, turning it into a light- ulations to gauge the energy needed to gener look like irregular bright clouds and last for a few days. The really big ones are known as great white spots. These are monster storms, up to 20,000 kilometers across—large enough to cover the entire Earth—that can persist for several months. But in 2018, a new type of storm appeared on the surface of the ringed planet. Rather than a giant spot, four medium-sized storms appeared in sequence at slightly different lat itudes near the north pole.

Identifying Midsized Storms The first storm appeared on 29 March as a white blemish near the north pole of the planet, growing to a size of 2,000 kilometers across in just a few days. It stood alone, trav eling westward at a speed of 220 kilometers A computer simulation (seen here) of the interactions between storms 1 and 2 helped scientists identify and per hour, until 25 May, when a second spot model the movement of the new type of Saturnian storm. Credit: E. García-Melendo/M. Soria/Universitat appeared. In August, two more storms joined Politècnica de Catalunya

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ate the storms. They concluded that these were intermediate storms also in terms of energy, Climate Change Will Make Us Sicker requiring about 10 times more energy to form than a typical small storm but around 100 and Lose Work Hours times less energy than great white spots. limate change has medical experts 3. Soot and small particles from burning Another Piece of the Saturnian Puzzle worried about our health, according coal and oil are killing people. Air pollution Still, the team doesn’t know much about the Cto a recent report from the Lancet from burning fossil fuels is causing thousands mechanism that powers these and other Countdown, an interdisciplinary group of of premature deaths in the United States storms on Saturn. Questions like why they 34 academic institutions and United Nations every year. Burning fossil fuels releases fine appear at certain latitudes, why they’ve been agencies. Authors include climate scientists, particles (smaller than 2.5 micrometers in observed only in the northern hemisphere, or doctors, economists, and other experts (bit diameter) that can lead to a whole host of why the great white spots seem to appear .ly/Lancet-Countdown). health problems, including asthma and birth roughly every 60 years are open to debate. Heat and air pollution are some of the worst complications. Black and Latinx people are hit “What this tells us is that there is a certain offenders, according to the report. Rapidly harder by air pollution compared with the dynamic that occurs below the upper clouds reducing greenhouse gas emissions will be the general population, despite contributing the that we see, known as the weather layer. This only way to lower health risks in the long run. least to the problem. In 2016, 64,200 people dynamic must happen at the base of the water The report issued results for countries died prematurely in the United States from cloud, 200 kilometers below the surface,” across the world, and it gives the United air pollution. Sánchez-Lavega said. States a dismal diagnosis: People will face 4. Children will face a lifetime of health higher exposure risk to Zika virus from longer risks from climate change. Children born mosquito seasons and a widening habitat; today will face far greater negative impacts on they’ll have an elevated risk of diarrheal ill their health than those of earlier generations, nesses and water contamination from wors and children of color will be the most affected. “Discovering a third type of ening floods, and they’ll witness disasters From birth complications in the womb to storm on Saturn will add that could cause anxiety and post-traumatic heat-related illness in infancy and young stress. These are just a few examples of the adulthood, children will face health impacts yet another piece to the wide-ranging consequences to health from at each stage of development that can affect puzzle of Saturn’s intricate climate change. them throughout their lives. As the authors Here are four major takeaways from the write in the report, “without significant weather system.” report for public health in the United States: intervention, this new era [of climate change] 1. Worker productivity is dropping will come to define the health of an entire because of soaring temperatures. Hotter generation.” days are only growing more frequent: Since “Saturn’s atmosphere is a complex, the turn of the century, we’ve experienced dynamic environment with its own seasons 18 of 19 of the hottest years on record. Scorch and cycles, much like weather cycles on Earth ing temperatures are now limiting the num but spanning decades rather than years,” said ber of hours people can work outside in agri Fine particles can lead to a Cassini project scientist Linda Spilker, who culture and industry. Last year alone, the host of health problems. wasn’t involved in the study. “Discovering a United States lost 64.7 million potential labor third type of storm on Saturn will add yet hours from extreme heat. Mississippi, Ala another piece to the puzzle of Saturn’s intri bama, and Louisiana are some of the U.S. cate weather system.” states most at risk of losing productivity hours According to Sánchez-Lavega, now that the and have some of the highest rates of poverty. Paths Forward Cassini mission is over, this is a good time to 2. Older adults are more and more at risk Limiting carbon emissions will be crucial to go back to the lab and focus on refining the from heat waves. By 2030, all members of the curtailing inequality and reducing future computer models of Saturn’s atmosphere. baby boomer generation will be over the age health care costs. “We hope that the James Webb Space Tele of 65. This aging population will be more at The United States has a way to go to meet scope will allow us to see in the infrared how risk of falling sick or dying from increased suggested emissions cutbacks. Last year, the these storms and other phenomena occur, temperatures because they may lack the abil country’s carbon dioxide emissions rose by characterizing the chemical composition so ity to seek shelter from the heat or have pre more than 3%. But some states have already we can feed it into the models,” Sánchez- existing health issues that heat could exacer begun to take action: Ten states and the Dis Lavega said. “Our future research will focus bate. Heat zaps our ability to think, leads to trict of Columbia rolled out plans for 100% [on understanding] the thermodynamic cycle dehydration and complications for people on clean or renewable electricity, and even more of water in Saturn using observations from certain medications, and in the most severe have enacted low -emissions standards for advanced telescopes like the James Webb.” cases can cause heatstroke and heart failure. vehicles. Heat wave exposures have been increasing in recent years and—like many other health By Javier Barbuzano (@javibarbuzano), Science effects from climate change—hurt commu By Jenessa Duncombe (@jrdscience), Staff Writer nities that are already vulnerable. Writer

EARTH & SPACE SCIENCE NEWS // Eos.org 11 D 12 with theteamwrote, hydrothermal systems, gypsumgiant crystals inactive attachedareto -García the originofthese crystals wasexhausted,” origins“thehydrothermalbecause system in them. the rockbehind andaresoclearpure size in youcansee to2 meters crystalsareup Itsgypsum Spain. Almería, in mine aformersilver Rica, Mina 1999in in wasdiscovered geode The Pulpí Rare in Size and Clarity A researcherstandsinsidethePulpígeode. Credit:HectorGarrido Giant Grew Geode Slow and Steady up (bit Pulpí of geode thegiant crystalsinside gypsum slow and steady process grewthe meters, the largest [geode] in theworld.” in [geode] thelargest meters, rock lined with crystals. Butits size is 11 cubic cavity-shape anegg “anovoid, geode is the in Universidad Granadade Spain.inThePulpí Juan Manuel clear. crystal the crystalsandmadethemliterally ripened fromthousandsofyearsago tuations It’s taken a while to figure out the geode’s tofigureIt’s takenawhile outthegeode’s A recent study in Geologyproposed that a “Giant crystals are scarce,” said coauthor Eos NEWS enough to fit several people inside. severalpeople tofit enough southeastgeodelarge ofSpainsitsa eep in an abandoned mine in the Ruiz said. Most areas that have grown areasthathave Most said. Ruiz grown

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Addressing Arctic Challenges Requires a Comprehensive Ocean Survey

inventory of Arctic observations is scattered, fractured, and incomplete. In response to the need for a more complete data set, an international team of scientists with expertise in Arctic Ocean physical, carbon, and ecological systems gathered in 2015. At the inaugural Synoptic Arctic Survey (SAS) workshop at the Norwegian Embassy in Washington, D.C. (bit.ly/SAS -workshops), this team explored how to coordinate a pan–Arctic Ocean research effort using icebreakers and research ships. This vision is scheduled to become a reality in 2020 and 2021, with a coordinated multinational campaign to gather ocean data in the Arctic.

A Pan-Arctic Approach The inertia of the climate system and the long atmospheric residence time of CO2 released by human activities drive the long-term transformation of the Arctic environment. A rapidly growing number of changes highlights the resulting challenges and conse- In this 2007 photo, the Swedish icebreaker Oden (left) runs a seismic cable in the wake of the Russian nuclear- quences: freshening surface waters, season- powered icebreaker 50 Let Pobedy, which is plowing through heavy ice north of Greenland. The Synoptic Arctic ally altered light penetration into the ocean Survey team plans to launch a coordinated multinational campaign using icebreaker ships to gather data in the surface, dwindling sea ice coverage, increased Arctic Ocean beginning in 2020. Credit: Leif Anderson energy and carbon exchange between the ocean and the atmosphere, ocean acidification, changes in planktonic and sympagic (sea ice–dwelling) communities that modify the ince the International Polar Year Science-capable icebreakers, the backbone biological carbon pump, altered migration (which actually lasted from 2007 to of polar marine science, have a long history patterns of fish, and northward range expan- S2010), two truths about the changing of gathering the data necessary for answering sion of species. Arctic have emerged. First, the ongoing rapid such questions. These ships typically follow Because existing Arctic Ocean studies show transformation of the Arctic environment will national priorities or research initiatives and inherently large interannual variability in the continue for decades, regardless of future traverse selected areas of the Arctic Ocean, properties they characterize, and because global carbon dioxide (CO2) emission levels. obtaining full-depth ocean data that cannot there are sparse baseline data on which to Second, the scientific challenges and conse- be collected in any other way. Historic expe- draw, the scientists at the 2015 workshop quences arising from this transformation are ditions explored previously unsurveyed loca- concluded that a synoptic Arctic survey of too large to be addressed by a single country tions, but these expeditions were isolated marine physical, carbon, and ecological sys- alone and too complex to be properly under- regionally and temporally. Consequently, the tems is critically needed. The word synoptic, stood through single-discipline research meaning “seen together,” denotes a broad approaches. approach that integrates information from These observations are interconnected and many sources. constitute a new reality for the Arctic [e.g., Since 2015, the SAS group has held succes- Moore and Grebmeier, 2018] that is far from A coordinated, sive international workshops in Japan, Rus- understood and that presents challenges to multinational pan- Arctic sia, Sweden, and the United States. And in stakeholders and decision-makers alike. June 2018, the group published a comprehen- Expanding fisheries, exploration, shipping, Ocean research effort using sive, peer-reviewed science plan that includes and tourism all must be managed well. But icebreakers and research information about the ships involved, pro- how do we best manage such enterprises posed cruise tracks, and the measurements to when the environments in which they oper- ships is scheduled to be made (bit.ly/SAS-science-plan). National ate change faster than we can observe and become a reality in 2020 teams have been established, and proposals understand with the present levels of com- have been submitted or funded. In October mitment? and 2021. 2018, an SAS Scientific Steering Committee

EARTH & SPACE SCIENCE NEWS // Eos.org 13 OPINION

was established at a meeting at Woods Hole the efforts making up this campaign will all Facilitating Arctic Science Oceanographic Institution. take place during the same season and year and Education The SAS group consensus is that our (mostly in the summer and fall of 2020 but The SAS science plan builds on one over understanding of the Arctic Ocean will be with some in the summer and fall of 2021). arching question: What are the present state greatly advanced through a pan-Arctic, mul- This approach will allow for a synoptic view and major ongoing transformations of the tination, multiship campaign based on of the changes occurring in the Arctic Ocean Arctic marine system? The plan also poses updated sampling and analytical protocols and provide integrated data sets to advance nine supporting questions, three each in the and strategically selected ship tracks. Ideally, model development and prediction. focal areas of the SAS: physical oceanography, marine ecosystems, and the carbon cycle and ocean acidification. Addressing these nine questions, which illustrate the interconnected nature of Arctic Ocean systems, will provide input toward the overarching question.

The effort to answer these and other scientific questions will benefit our understanding of how the Arctic Ocean operates and will also help foster the next generation of Arctic researchers.

With respect to fundamental drivers of ocean processes, including ocean circulation and the distributions of sea ice and water masses, we are looking to address the following: What are the present states of the heat and freshwater budgets in the Arctic Ocean? How are water mass circulation patterns responding to changes in forcing, and how are water mass sources responding? And to what degree does ice cover hamper light and gas exchange between the ocean and the atmosphere and thereby influence biological production and carbon cycling? These questions connect intimately to others about how Arctic marine ecosystems are shifting. For example, how do primary

Fig. 1. Shown at top are the observed trends from 1997 to 2017 in annual mean air–sea CO2 flux (left; grams of production and the flow of energy and bio- carbon per square meter per year; positive values represent fluxes into the ocean) [ Yasunaka et al., 2018] and mass between various levels of a food chain 2 the correlation (r ) between CO2 flux and number of ice-free days per year (right; higher values correspond to vary across different regions of the Arctic more correlation between open ocean days and CO2 flux). Observed sea ice concentrations are from the Ocean? How will new species invade parts of National Snow and Ice Data Center [Cavalieri et al., 1996]. The corresponding projections for the period 2020– the Arctic Ocean when hydrographic condi- 2049 in the middle diagrams are based on the Community Earth System Model large ensemble [ Kay et al., 2015] tions change, and will native species be under the Intergovernmental Panel on Climate Change’s Representative Concentration Pathway 8.5 emission wiped out? scenario (average of 10 ensemble members). At bottom are projected trends, extending to 2080, for area- Ongoing environmental changes are also

integrated CO2 fluxes (left) and sea ice–free days (right) north of 80°N. The bold curves are the ensemble means, affecting the carbon cycle in the Arctic Ocean, and the thin curves represent individual ensemble members. An ice-free area is defined as having sea ice cover- the ocean’s contribution to sustaining the age of less than 15%. global CO2 ocean reservoir, and the rate of

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ocean acidification. Disappearing perennial Ultimately, we must know sea ice is enabling a stronger flux of CO2 and acidification in the northern Barents and Kara how the Arctic system Seas (Figure 1), heralding changes that will functions to assess risks occur over the entire Arctic Ocean under unabated global warming [Harada, 2016]. and to develop policies The effort to answer these and other scien- that allow effective tific questions will benefit our understanding of how the Arctic Ocean operates and will also management. help foster the next generation of Arctic researchers. The SAS will provide opportunities for early-career scientists to participate in the field effort, learn from their peers, and which will provide a baseline for future com- participate in subsequent workshops during parisons—as well as echograms from acous- the data synthesis period. In its efforts to tic surveys that help illuminate plankton and facilitate education, it will also create new fish distributions. constellations of collaboration, a critical aspect of the needs of a new Arctic. International Polar Leadership SAS will not specifically address other The challenge of understanding the changing important aspects related to Arctic change, Arctic belongs to all countries. Various recent In heavy sea ice conditions, a powerful icebreaker such as socioeconomic questions. However, efforts have underscored a growing commit- becomes a necessity. This aerial view shows the we foresee that new discoveries and better ment to enhance international collaboration. smaller Swedish icebreaker Oden following the Rus- scientific understanding of the Arctic Ocean For example, China, Japan, and South Korea sian nuclear-powered icebreaker 50 Let Pobedy. will influence policy and decision-making at held a high-level dialogue about the Arctic in Credit: Leif Anderson national and international levels. 2017 [Ministry of Foreign Affairs of the People’s Republic of China, 2017]. Also in 2017, the eight A Data Set Built to Last nations of the Arctic Council signed an agree- Yasunaka, S., et al. (2018), Arctic Ocean CO2 uptake: An improved It is of utmost importance that measurement to enhance scientific cooperation (bit multi-year estimate of the air-sea CO2 flux incorporating chlorophyll- a concentrations, Biogeociences, 15, 1,643–1,661, ments made today will still be useful as .ly/Arctic-Council-agreement). This agree- https://doi . org/ 10 . 5194/ bg-15 - 1643 - 2018. trusted benchmarks 100 years into the future. ment entered into force in May 2018, and Thus, the SAS will adopt proven methods with although it must be rigorously tested before established accuracies that rely on ship- it can be hailed as a success, it may provide a By Øyvind Paasche (oyvind.paasche@uib based, in situ, high-quality measurements to useful framework to stimulate and facilitate .no), Are Olsen, and Marius Årthun, Bjerknes quantify a wide range of ocean physical, car- collaboration among polar researchers from Centre for Climate Research, University of Ber- bon, and ecosystem characteristics. different countries. gen, Bergen, Norway; Leif G. Anderson and SAS will also benefit, however, from ocean Ultimately, we must know how the Arctic Sten-Åke Wängberg, University of Gothenburg, observing systems that are currently being system functions to assess risks and to Gothenburg, Sweden; Carin J. Ashjian, Woods revolutionized with the development of develop policies that allow effective manage- Hole Oceanographic Institution, Woods Hole, autonomous, high-tech platforms and sen- ment. Providing this knowledge is the utmost Mass.; Jacqueline M. Grebmeier, University sors (e.g., sea ice-going Argo floats) and that motivation for SAS, because it will testify to of Maryland, College Park; Takashi Kikuchi, are transforming our understanding of how the value of international collaboration and Shigeto Nishino, and Sayaka Yasunaka, Japan the ocean works and evolves in concert with of furthering our scientific understanding of Agency for Marine- Earth Science and Technol- a changing climate. Thus, the data generated the Arctic Ocean. ogy, Yokosuka; Sung- Ho Kang and Kyoung-Ho will also provide a unique and valuable vali- Cho, Korea Polar Research Institute, Incheon; dation for new technologies. References Kumiko Azetsu- Scott, William J. Williams, Salinity, temperature, oxygen, nutrients, Cavalieri, D. J., et al. (1996), Sea ice concentrations from Nimbus-7 and Eddy Carmack, Department of Fisheries SMMR and DMSP SSM/I-SSMIS passive microwave data, Natl. and carbon chemistry are key determinants Snow and Ice Data Cent., Boulder, Colo., https://doi . org/ 10 . 5067/ and Oceans, Dartmouth, N.S., Canada; Sinhué of ecosystem structure and function, and 8GQ8LZQVL0VL. Torres- Valdés, Alfred Wegener Institute for observing these core ocean characteristics Harada, N. (2016), Potential catastrophic reduction of sea ice in Polar and Marine Research, Bremerhaven, Ger- the western Arctic Ocean: Its impact on biogeochemical cycles will allow us to gauge ecosystem connectivity and marine ecosystems, Global Planet. Change, 136, 1–17, many; Toby Tyrrell, University of Southampton, across the Arctic Ocean. The coordinated pat- https://doi . org/ 10 . 1016/ j.gloplacha . 2015.11.005. Southampton, U.K.; Karen Edelvang, National Kay, J. E., et al. (2015), The Community Earth System Model tern of ship tracks spanning the entire Arctic (CESM) Large Ensemble Project: A community resource for Institute of Aquatic Resources (DTU Aqua), Ocean planned by SAS also offers a unique studying climate change in the presence of internal climate Technical University of Denmark, Kongens variability, Bull. Am. Meteorol. Soc., 96, 1,333–1,349, https://doi opportunity to collect novel data types. One .org/ 10.1175/ BAMS-D-13 - 00255.1. Lyngby; Jianfeng He, Polar Research Institute of such novel data source, environmental DNA, Ministry of Foreign Affairs of the People’s Republic of China China, Shanghai Shi; and Heidi Marie Kassens, is extracted from environmental samples (2017), The Second Trilateral High- Level Dialogue on the GEOMAR Helmholtz Centre for Ocean Research Arctic: Joint statement, www. fmprc . gov . cn/ mfa _ eng/ wjbxw/ (e.g., seawater) and contains information P020170614645306549315 . pdf. Kiel, Kiel, Germany about multiple organisms. Other novel Moore, S. E., and J. M. Grebmeier (2018), The Distributed Biolog- ical Observatory: Linking physics to biology in the Pacific Arctic u approaches will include a reference collection region, Arctic, 71, suppl. 1, 1–7, https://journalhosting . ucalgary . ca/ Read the full story at bit.ly/Eos-ocean of biodiversity data across the Arctic Ocean— index . php/ arctic/ article/ view/ 67644. -survey

EARTH & SPACE SCIENCE NEWS // Eos.org 15 OPINION

Equal Representation in Scientific Honors Starts with Nominations

The work culminated in six nomination packages for individuals from underrepresented groups—and it worked. Three of our nominees were honored with one AGU fellowship, one AGU medal, and one American Meteorological Society fellowship. Here we’ll share our experience, and perhaps it will inspire you to organize a nomination task force in your community to help to increase the diversity of honors and award winners at AGU and throughout the scientific community.

Divide and Conquer In our task force, we approached the nomination process by dividing and conquering. One person from the group volunteered to be a “shadow nominator” for a candidate—the person who put the whole package together. The shadow nominator was responsible for contacting senior and lauded members of our field for nomination and support letters, putting together the nominee’s curriculum vitae Awardees and colleagues gather for the AGU Honors Banquet at Fall Meeting 2018 in Washington, D.C. Credit: (CV) and bibliography, and submitting the Event Photography of North America Corporation package. We then invited a main nominator, usually a senior colleague, either in or outside the task force, to write the overarching nomination letter and support the shadow nomi- epresentation throughout the science, tion Task Force within AGU’s Space Physics nator as they assembled the package. The technology, engineering, and mathe- and Aeronomy (SPA) section. It was straight- weekly telecon hours were spent suggesting, Rmatics (STEM) disciplines still does not forward to start up: MacDonald and others strategizing, and discussing potential candi- mirror that of society at large. Furthermore, created a Google form sign-up that she and dates for nomination, whom we listed in a we now know that when underrepresented SPA leaders publicized at AGU’s Fall Meeting shared Google Sheet along with relevant individuals are employed in a STEM field, and on the mailing lists for our field. She information such as h -index, notes on signif- especially in academia, the very fact of being scheduled a series of telecons for the group icant contributions to the field, and sugges- the lone or one of a few diverse members cre- that continued through the winter and into tions for nominator and letter writers. ates an additional “invisible burden” of han- early spring—nominations for AGU Honors In our effort to create the best nomination dling tasks that often go less recognized when are due each year in March. Our primary packages possible, we reached out to mem- being considered for awards and honors motivation with the task force was simply to bers on our section’s Union Fellows Commit- [Rodríguez et al., 2015; Social Sciences Feminist nominate people who were not being ade- tee. During one telecon session, they gave us Network Research Interest Group, 2017]. quately included in the process and thus show an in-depth presentation on what a nomina- Because of these unseen burdens, nominating that the problem was not a lack of high- tion package looks like and how best to high- individuals from underrepresented groups for quality candidates but that they were not light the accomplishments of the nominees. those honors can sometimes be a challenge, being recognized at the nomination stage. One useful tip was to have the three sup- as their career may not result in as many of porting letter writers focus on different the obvious markers of impact and influence. themes of the nominee’s career, such that the This lack of recognition is one of many effects letters are complementary with little to no of implicit bias. overlap. We achieved this by dividing letters One way to address this underrepresenta- The work culminated in by science topic or by decades, as a career tion in honors is to deliberately seek out six nomination packages evolves over time, or by accomplishment deserving but overlooked members and put (e.g., notable publications for one, mentor- their work in front of award committees. In for individuals from ship for another, and service for the third). the fall of 2017, with this goal in mind, Liz underrepresented The main nominator then wrote a letter that MacDonald, a heliophysicist at NASA Goddard outlined the achievements noted in detail in Space Flight Center, organized the Nomina- groups—and it worked. the other letters and tied them all together

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with persuasive, enthusiastic language. We The process may sound straightforward, • Leverage best practices with the sup- learned not to be timid when asking letter but that is not meant to trivialize the amount port of your section or community’s award writers to focus on a certain topic or to change of work that all the members put in over sev- committee and find resources. We discov- their language to be more forceful. The suc- eral months. Because many male allies vol- ered many helpful AGU resources during a cessful packages from our group went unteered in our group, it wasn’t simply a case discussion with our honors committee and through several revisions of each letter. of more invisible burdens. We kept enthusi- online. Our team carefully selected the individuals asm high through our telecons, during which • Recruit a team motivated to address this whom we asked to be letter writers. You want we shared experience and advice with each issue, and encourage volunteers by turning to find close colleagues of the nominee who other. Our task force members are highly involvement into an energizing professional are themselves accomplished—ideally, pre- motivated, but in any all- volunteer group, development opportunity. Our team of about vious recipients of the award. Avoid soliciting ongoing encouragement is crucial. 30 highly motivated volunteers met weekly writers from the same institution to prevent from January to March in 1-hour telecons, any conflicts of interest, and vary the letter with about 12 people per call. This year we’ve writers by age, background, geography, and reduced that to once every 2 weeks and specialty. Gaining awareness of started the process earlier. When creating your nominee’s CV, it is • Build in multiple ways to participate, absolutely OK to ask the nominee for a copy scientists outside our direct such as encouraging early-career scientists of his or her most recent CV. There is no need networks, after all, is the to be shadow nominators and pairing them to mention the purpose unless you wish to. with more senior nominators who mentor On the one hand, nominees may be able to entire point of this process. and oversee their work. aid in identifying the right letter writers and • Make it easy for your team to collaborate adapting their CVs if they know about the on nomination packages. Our team used Goo- nomination. On the other hand, if a nomina- gle Drive to host tools. Because h-index and tion is not successful, that person may feel In addition to half our nominees receiving citations are complex, we agreed on a source unnecessary rejection. Once you have the CV, honors, we were also told that our successful for h-index across all nominations and refine and pull out a summary timeline of nomination for AGU Fellow was one of the recruited a librarian who helped create stan- positions, awards, notable contributions to strongest packages in the entire submission dardized bibliographies for each package. the field (service, science, or otherwise), evi- pool that year. This told many of us what • Embrace crowdsourcing: Gaining aware- dence of good mentorship, and any other we already knew: There are scientists in our ness of scientists outside our direct networks, activities of note. Bullet points or short tables research areas who are due an honor but have after all, is the entire point of this process. If work well to highlight metrics that will been overlooked. all you do is identify the right names, you’ve impress. For our AGU Honors nominations, To spread the workload, MacDonald passed cleared a big first hurdle that may inspire we highlighted the number of publications the chair position this nomination cycle to others to take on the work of pushing those in AGU journals, service to AGU, number of Amy Keesee, an associate professor at the names forward. invited talks, and number of students and University of New Hampshire, and the team Many of us believe diversity is the founda- postdocs mentored throughout the nomi- recruited new members. In addition to being tion from which good science flourishes. We nee’s career. Distill the CV down to the essen- rewarding, participating in the task force is a hope other sections and communities will use tials, leaving a concise profile of the breadth valuable and unique opportunity for early- these lessons from our experience to organize of the impact that the nominee has had on career scientists to network with those more a nomination task force or redouble their the field. senior. These new members also brought ongoing efforts and bring recognition equally For the bibliography, put citation numbers fresh ideas for potential nominees. This year, to the very best scientists in our fields. next to the highly cited papers and annotate we are revising last year’s unsuccessful pack- more relevant papers (for our nominees, that ages and putting together new ones to better References included noting those published in AGU jour- shine a light on the achievements of those Rodríguez, J. E., K. M. Campbell, and L. H. Pololi (2015), Address- ing disparities in academic medicine: What of the minority nals). Use boldface or italic to emphasize any who deserve to be seen. tax?, BMC Med. Educ., 15, 6, https://doi . org/ 10.1186/ s12909 - 015 annotations you have added. Don’t feel pres- -0290-9. sure to conform to a standard APA citation list Additional Tips and Key Steps Social Sciences Feminist Network Research Interest Group (2017), The burden of invisible work in academia: Social inequalities in alphabetical order. Place the publications of Our Process and time use in five university departments, Humboldt J. Soc. chronologically or in order of citation number • Before creating a task force, raise aware- Relat., 39, 228–245, www. jstor .org/ stable/ 90007882. on the basis of how the list will show the most ness of the lack of diversity in honorees with expertise and impact. your community or section, specifically with Several volunteers from our group served the appropriate awards committee, which will By Allison N. Jaynes (allison -n-jaynes@uiowa as red team reviewers. They looked over the help get some leadership buy-in regarding .edu), Department of Physics and Astronomy, nomination letters, CV, and bibliographies as the systemic issue. Convince leadership to University of Iowa, Iowa City; Elizabeth A. they were being created and again before sub- support and encourage a task force to address MacDonald, NASA Goddard Space Flight mission. The red team looked for redundancy it. Broadening and demystifying participation Center, Greenbelt, Md.; and Amy M. Keesee, between nomination letters and suggested in the awards cliques take a network, and our Department of Physics and Space Science Cen- ways in which the letter writers could refine task force serving as a proxy network of like ter, University of New Hampshire, Durham their wording to focus on different achieve- minds proved to be a powerful approach to ments. creating a new kind of power network. uRead the full story at bit.ly/Eos-honors

EARTH & SPACE SCIENCE NEWS // Eos.org 17 Einstein Says: It’s 309.7-Meter O’Clock Atomic clocks are now so accurate that Earth’s gravity can be seen to slow them down. Geodesists are preparing to use this relativistic effect to measure elevation.

By Bas den Hond

18 Eos // JANUARY 2020 t’s about an hour’s walk from where Jakob Flury lives—through his village of Völksen in Germany, up a hill called the Kalenberg—to see a monument to his profession: “A geodesy marker from Gauss, where he did his observations, his triangulations.” That would be Carl Friedrich Gauss, the famous German mathematician. “It’s just a stone, a triangulation stone, as we say,” explained Flury, a professor at Leibniz University in Hanover, Germany. “This was the benchmark. When [Gauss] did his measurements, they built a small tower so they could look over the trees, and sometimes also cleared the forest, so they could look for 100 kilometers or maybe even more. They did the angular measurements, and brought them down to the benchmark. And then the center of this stone had these very good coordinates.” It was good enough for an early-19th-century scientist, at least. Gauss was assigned to survey the Kingdom of Hanover by covering it with imaginary triangles—their vertices anchored by hilltops and church towers, their sides accurately calculated by trigonometry. ITwo hundred years later, geodesy, the science of measuring the Earth, demands more. And it has more. From orbit, taking measurements of Earth was among the first tasks entrusted to satellites. Fleets of geolocation satellites, such as GPS constellations, now allow people with a receiver to determine where they are within a few meters or, with advanced equipment, millimeters. Radio telescopes track the movement of the continental plates on which they rest, millimeter by millimeter, by staring in unison at quasars—active galactic nuclei billions of light-years away—in a process called very long baseline interferometry (VLBI). But it is not enough. That’s why Flury, with colleagues across the world, is looking to incor- porate into geodesy the most advanced theory of space—and time—available: general relativ-

EARTH & SPACE SCIENCE NEWS // Eos.org 19 Triangulation stones (trig points), like this one on a peak in the English Lake District, were the standard benchmarks of geodesy for more than a century. Credit: iStock .com/ DaveBolton

ity. He gave a talk on the future of the new called the rigorous but imaginary experi- approach, relativistic geodesy, at the Inter- ments that led him to groundbreaking dis- national Union of Geodesy and Geophysics coveries about space and time. His special (IUGG) General Assembly in Montreal, Can- theory of relativity predicted that twin sib- ada, in July 2019. lings would no longer be the same age if one of them made a very fast trip into space and “We Are in This back. And his general theory of relativity Four- Dimensional Reality” predicted that twin clocks would not keep Even though he’s been working at relativis- time at the same clip if one of them were tic geodesy for years, it never ceases to fas- nearer to an attracting—or rather, a space- cinate Flury: “It’s really a new world, a new time-bending—mass. awareness. Here we are, in this four- Innovation has caught up to imagination. dimensional reality, the curved space-time. Atomic clocks have gotten so good, measur- It’s not just Euclidean space that we’re living time in such small increments and with ing in. Time is the fourth coordinate, and such stability, that the gravitational slowing it’s where the irregularities due to gravity of time can actually be observed between come in. We are now at the level at which clocks at familiar terrestrial height differ- this starts to be not purely theoretical any- ences. The best clock so far, constructed at more.” the National Institute of Standards and Suppose Gauss in 1819 had installed a Technology (NIST) in the United States, uses clock next to his triangulation stone on the light emitted by ytterbium atoms stimu- Kalenberg, a clock that kept perfect time. lated by laser light. The light’s wavelength, Suppose he sent an identical clock to the or frequency, is so stable that this clock port city of Bremerhaven, 161 kilometers loses or gains only 1.4 × 10-18 of a second per north and 309.7 meters down, at sea level. second, which would add up to an error of By now, after 200 years, these clocks would less than 1 second over the age of the uni- disagree. The clock on the water’s edge verse. would be ever so slightly behind, by about Equally important, methods have been 0.002 second. But it would not be wrong. It devised to transport time signals produced would just be keeping time in a different by multiple atomic clocks across long dis- kind of space, closer to the center of the tances over glass fiber links to compare Earth, which is to say, deeper in its gravity them in one place. well. In physical terms, the clock would These developments will soon put general exist at a lower gravitational potential. relativity into the geodetic tool kit. If two This used to be a Gedankenexperiment, or identical clocks are out of sync, you have in “thought experiment,” as Albert Einstein fact a direct measurement of the difference

20 Eos // JANUARY 2020 in their local gravity fields. And this differ- Atomic clocks ence is essential for any correct description of their difference in elevation. have gotten so “We say that our satellites are now our church towers,” Flury said. “And in the good, measuring future, the church towers could be the atoms in these devices.” time in such small

Struggle of Geometry and Gravity increments and with Even in the days when actual church towers such stability, that and surveying equipment were the only tools of the trade for geodesists, the geode- the gravitational sists were taking gravity into account when- ever they wanted to determine the elevation slowing of time can of some place. If you wanted to know the height of a hill compared to where you were, actually be observed the standard approach was (and often still is) to aim a leveling instrument horizontally at commonplace at a measuring rod somewhat farther up the hill. You record the height and repeat the terrestrial height process from that location until you are at differences. the top. Each time, you know the instrument is horizontal only because a spirit level says so. That’s where gravity comes in, and it is essential to the interpretation of the measurement. For depending on where you are on Earth, leveling approach to go where you want. and the distribution of mass within it, Errors accumulate with distance. If you go “straight down,” which is by definition in through the U.S. this way from the East the direction of Earth’s attraction, may not Coast to the West Coast, you have an error be in the direction you’d expect. of 1 or 2 meters. And it takes a long time to This, among other factors, makes spirit resolve where those errors come from, what leveling problematic when done over large are the right values.” distances, said Jürgen Müller, also a profes- The history of geodesy is the story of this sor at Leibniz University who gave a sepa- struggle between geometry as the eye sees it rate talk on relativistic geodesy at the IUGG and gravity as the body feels it. The outcome General Assembly in Montreal. “You start at has been that two surfaces are in use to rep- sea level, at the tide gauge, and you use the resent the shape of Earth. One is the reference ellipsoid, a flattened sphere that is essentially an improved version of the classical spherical globe found in libraries and classrooms. It serves the same function: to point out locations by latitude and longitude. It’s more accurate than a sphere because Earth happens to be slightly flattened, a result of the competing forces of gravity and rotation. Isaac Newton already noted in his Philosophiae Naturalis Principia Mathematica that a rotating planet that was completely fluid would have an ellipsoid as its equilibrium surface. In addition to latitude and longitude, GPS measurements provide height in relation to this ellipsoid. However, to make sense, these heights have to be recalculated to refer to a more physically meaningful shape The National Institute of Standards and Technology’s Yb Lattice Clock, above, of Earth: the geoid. The geoid is a surface of uses light emitted by ytterbium atoms stimulated by laser light. This clock loses or constant gravitational potential—the gains on the order of 10-18 of a second per second, or not quite 1 second over the energy that would be required to lift 1 kilo- age of the universe. Credit: NIST gram from the center of Earth to that level.

EARTH & SPACE SCIENCE NEWS // Eos.org 21 The geoid hugs the ellipsoid but has hills and valleys, because mass is not equally dis- The history of tributed in Earth’s core, mantle, ocean, crust, and atmosphere. geodesy is the The geoid ideally would correspond to sea level. Imagine the ocean without tides, cur- story of the rents, or winds and somehow extending under the continents. Measuring heights struggle between with respect to the geoid guarantees that you won’t calculate water flowing sponta- geometry as the neously between places at equal elevations, or even uphill, which is possible when eye sees it and heights are calculated using the ellipsoid. Ideally, heights with respect to the geoid gravity as the body (dynamic heights) are expressed not in meters but in joules per kilogram (units of feels it. energy per unit of mass) to account for the varying strength of Earth’s gravity at different heights.

From Decimeters to Millimeters the Earth itself is wobbling and deforming and Beyond in many different ways,” Flury explained. For mapmaking, the ellipsoid is the surface To deal with that, geodesy uses a combi- to use, but there is a constant need to keep nation of techniques to construct an Inter- track of where everything is. “Nothing on national Terrestrial Reference Frame (bit.ly/ Earth is fixed; everything is moving, [and] itrf-site) that works well enough for practi- cal applications. “It has a couple of hundred very accurate benchmarks, in a nice global distribution,” Flury said. “So in the coordinate frame, every point has some move- a ment, but as a set, geodesists can very well define the frame.” To add the height of any location to such maps, it is necessary to recalculate the height that GPS provides as the distance to wherever the geoid is in that place, above or b below the ellipsoid. That’s where gravity measurements come in. Until now, such measurements have been performed for the large-scale undula- tions of the geoid by satellites, such as those c of the Gravity Recovery and Climate Experi- ment (GRACE), Gravity Field and Steady- State Ocean Circulation Explorer (GOCE), and the current GRACE Follow-On missions. Local measurements are performed from airplanes and on the ground with gravime- d ters, instruments that measure the gravitational acceleration of objects that are falling or bobbing up and down on springs. But to Satellites, such as those of the GRACE Follow-On mission (a collaboration between get at the gravitational potential, these NASA and the German Research Centre for Geosciences) are essential to geode- measurements of gravity’s strength have to sists measuring Earth’s gravity. (a) When both spacecraft are over the ocean, the be combined with much less precise distance between them is relatively constant. (b) When the leading spacecraft assumptions about the complete mass dis- encounters land, the land’s higher gravity pulls it away from the trailing spacecraft, tribution underfoot. Clocks are a promising which is still over water. (c) Once the second satellite also encounters the land, it addition to this arsenal, because they allow too is pulled toward the higher mass and consequently toward the leading space- a direct measurement of the gravitational craft. (d) When both spacecraft are over water again, the trailing spacecraft is potential itself. slowed by land before returning to its original distance behind the leading space- For now, Flury and Müller are validating craft. Credit: NASA the approach with strontium clocks, which

22 Eos // JANUARY 2020 have an accuracy of 2–3 × 10-17, which corre- sponds to decimeter-level accuracy in height. Recently, transportable strontium clocks have become available, enabling measurements of the gravity potential anywhere a small trailer can be hauled. Trans- porting clock signals over glass fiber connections and via satellites, researchers envisage creating networks of clocks, measuring gravity in real time for geodetic and geophysical purposes. For many of these applications, technology still has to advance quite a bit. “When you talk to the clock people, at this point they can establish heights at the decimeter level,” Flury said. This includes the uncertainty introduced by the communication link between the clocks that are being compared. “There are some who can show very solid error budgets that make clear they are at the centimeter level. There are those at NIST who can show a path forward toward milli- Gravity is determined by mass. Earth’s mass is not distributed equally, and it also meters. There is even theoretical work on a changes over time. This visualization of a gravity model (geoid) was created with thorium clock that could be orders of magni- data from the Gravity Recovery and Climate Experiment (GRACE, a collaboration tude better. But this is fiction at this point.” between NASA and the German Aerospace Center) and shows variations in Earth’s gravity field. Red shows areas where gravity is relatively strong, and blue reveals areas where gravity is weaker. Credit: NASA/JPL/Center for Space “We would say, Research, University of Texas at Austin ‘This frequency, of this clock on the According to Müller, one consequence of the use of frequencies as stand-ins for Moon, is our new height could be that the official reference height reference.’” height goes from sea level to a place completely off the planet. “You need a reference point. But we could have that by putting a clock on the surface of the Moon, as a well- controlled outside reference frequency. This Moving “Sea Level” to the Moon would change the whole concept of our Centimeter accuracy would put relativistic height reference frames. We would say, geodesy on par with GPS measurements, ‘This frequency, of this clock on the Moon, and with carefully corrected spirit leveling is our new height reference.’” over distances of tens of kilometers. With Even then, geodesy wouldn’t have quite a millimeter accuracies, clock-based height steady foothold. The Moon isn’t completely measurements could be used for much more rigid either; it deforms regularly due to its than maps and civil engineering projects. tidal attraction to Earth, and even the influ- “One of the most important things will be ence of the Sun and the other planets in our time variations of the gravity,” Flury said. solar system will need to be taken into “Take a volcano: All those processes going account. on inside lead to tiny variations of the grav- “But you have good models of the Moon,” ity. You could actually observe tectonics. Müller said optimistically. “It’s just an idea; Even now with GPS we can see the uplift of we have to see what we can gain.” some mountain chains, but this would be a new way to observe that. Coastal subsidence Author Information or uplift processes can be pretty complex Bas den Hond (bas@ stellarstories .com), and not so easy to monitor—take the Gulf Science Writer Coast, for example, New Orleans. Millimeter precision would be a wonderful tool to mon- u Read the full story at bit.ly/Eos itor coasts.” -Einstein

EARTH & SPACE SCIENCE NEWS // Eos.org 23 24 Eos // JANUARY 2020 DOES O HAVE A MAGMA OCEAN?

Future space missions will further our knowledge of tidal heating and orbital resonances, processes thought to create spectacular volcanism and oceans of magma or water on other worlds.

By Alfred McEwen, Katherine de Kleer, and Ryan Park

Jupiter and its moon Io are featured in this collage of images taken by the New Horizons spacecraft as it flew by in 2007. Credit: NASA/JHU APL/SWRI/Goddard Space Flight Center

EARTH & SPACE SCIENCE NEWS // Eos.org 25 he evolution and habitability of Earth and lites within such orbital resonances exert periodic other worlds are largely products of how gravitational influences on each other that serve to much these worlds are warmed by their maintain noncircular orbits (orbits with nonzero eccen- parent stars, by the decay of radioactive ele- tricities), which drive tidal heating. Simultaneously, tidal ments in their interiors, and by other exter- dissipation and heating within orbiting satellites damp nal and internal processes. the orbital eccentricity excited by mean-motion reso- TOf these processes, tidal heating caused by gravita- nances, move orbits inward, and power tectonism and tional interactions among nearby stars, planets, and potential volcanic activity. Without resonances, contin- moons is key to the way that many worlds across our ued tidal energy dissipation would eventually lead to cir- solar system and beyond have developed. Jupiter’s cular orbits that would minimize tidal heating. intensely heated moon Io, for example, experiences For as much as we know, there remain fundamental voluminous lava eruptions like those associated with gaps in our understanding of tidal heating. At a Keck mass extinctions on ancient Earth, courtesy of tidal Institute for Space Studies workshop [de Kleer et al., 2019] heating. Meanwhile, less intense tidal heating of icy in October 2018, participants discussed the current state worlds sometimes maintains subsurface oceans— of knowledge about tidal heating as well as how future thought to be the case on Saturn’s moon Enceladus and spacecraft missions to select solar system targets could elsewhere—greatly expanding the habitable zones help address these gaps (see bit.ly/Keck-workshop). around stars. Tidal heating results from the changing gravitational JUPITER AND THE GALILEAN SATELLITES attraction between a parent planet and a close-in moon Each time Ganymede orbits Jupiter once, Europa com- that revolves around that planet in a noncircular orbit. pletes two orbits, and Io completes four orbits. This 1:2:4 (The same goes for planets in close noncircular orbits resonance was discovered by Pierre-Simon Laplace in around parent stars.) Because its orbit is not circular, the 1771, but its significance was realized only 200 years later distance between such a moon and its parent planet var- when Peale et al. [1979] published their prediction that ies depending on where it is in its orbit, which means it the resonance would lead to tidal heating and melting of experiences stronger or weaker gravitational attraction Io, just before the Voyager 1 mission discovered Io’s to its parent body at different times. These tightening active volcanism. The periodic alignment of these three and relaxing responses of the gravitational attraction large moons results in forced eccentric orbits, so the change the orbiting moon’s shape over the course of shapes of these moons periodically change as they orbit each orbit and generate friction and heat internally as massive Jupiter, with the most intense deformation and rock, ice, and viscous magma are pushed and pulled. heating occurring at innermost Io. Meanwhile, tidal (The same process causes Earth’s ocean tides, although heating of Europa (and of Saturn’s moon Enceladus) the reshaping of the ocean generates relatively little heat maintains a subsurface ocean that’s below a relatively because of water’s low viscosity.) thin ice shell and in contact with the moon’s silicate The magnitude and phase of a moon’s tidally induced core, providing key ingredients for habitability. deformation depend on its interior structure. Bodies Although Peale et al. [1979] predicted the presence of a with continuous liquid regions below the surface, such as thin lithosphere over a magma ocean on Io, Voyager 1 a subsurface water or magma ocean, are expected to revealed mountains more than 10 kilometers high (Fig- show larger tidal responses and ure 1). This suggests that Io has a thick, cold lithosphere perhaps distinctive rotational formed by rapid volcanic resurfacing and subsidence of parameters compared with crustal layers. The idea of a magma ocean inside Io gen- bodies without these large fluid erally lost favor in subsequent studies, until Khurana regions. Tidal deformation is et al. [2011] presented evidence from Galileo mission data thus central to understanding a of an induced magnetic signature from Io. Induced sig- moon’s energy budget and natures from Europa, Ganymede, and Callisto (another probing its internal structure. of Jupiter’s moons that with Io, Europa, and Ganymede, The dissipation of tidal makes up what are known as the Galilean satellites) had energy (or the conversion of previously been interpreted as being caused by salty orbital energy into heat) within oceans, which are electrically conducting—and molten a parent planet causes the silicates are also electrically conducting. Considerable planet’s moons to migrate out- debate persists about whether Io has a magma ocean. ward. This process frequently The Jovian system provides the greatest potential for Fig. 1. Haemus Mons, seen here in an image taken drives the satellites into what advances in our understanding of tidal heating in the by Voyager 1, is a mountain near the south pole of are called mean-motion reso- next few decades. This is because NASA’s Europa Clipper Io. The mountain is about 100 kilometers wide × 200 nances with each other, in and the European Space Agency’s Jupiter Icy Moons kilometers long and rises 10 kilometers above the which their orbital periods— Explorer (JUICE) will provide in-depth studies of Europa surrounding plains, comparable to Mount Everest, the time it takes a satellite to and Ganymede in the 2030s, and the Juno mission orbit- which rises roughly 9 kilometers above sea level. complete a revolution around ing Jupiter may have close encounters with the Galilean The bright material is sulfur dioxide frost. Credit: its parent—are related by inte- satellites in an extended mission. However, our under- NASA/JPL/U.S. Geological Survey ger ratios. The multiple satel- standing of this system will continue to be limited unless

26 Eos // JANUARY 2020 Fig. 2. The Jovian and Saturnian systems. The top of each diagram shows the orbital architecture of the system, with the host planet and orbits to scale. Relevant mean- motion resonances are identified in red. The bottom of each diagram shows the moons to scale with one another.P indicates the rotational period, which for all the moons is equal to the orbital period, as they are tidally locked with their host planet. Credit: James Tuttle Keane/Keck Institute for Space Studies

there is also a dedicated mission with close encounters of discovered that Enceladus and Titan are ocean worlds, Io. The easily observed heat flow on Io (at least 20 times hosting large bodies of liquid water beneath icy crusts. greater than that on Earth) from hundreds of continually Precise measurements of the Saturnian moon orbits, erupting volcanoes makes it the ideal target for further largely based on Cassini radio tracking during close investigation and key to understanding the Laplace reso- encounters, have revealed outward migration rates much nance and tidal heating. faster than expected. But extrapolating the Cassini migration measurement backward in time while using ADVANCES FROM THE SATURNIAN SYSTEM the conventional assumption of a constant tidal dissipa- As discovered by Hermann Struve in 1890, the Saturnian tion parameter Q, which measures a body’s response to system contains two pairs of satellites that each display tidal distortion, implies that the Saturnian moons, 1:2 orbital resonance (Figure 2): Tethys-Mimas and impossibly, would have been inside Saturn in far less time Dione-Enceladus. More recently, the Cassini mission than the lifetime of the solar system. To resolve this con-

EARTH & SPACE SCIENCE NEWS // Eos.org 27 Tidal deformation is central to understanding a tradiction, Fuller et al. [2016] with spectroscopy, their bright flux in the infrared spec- proposed a new theory for tid- trum, and their preferential occurrence in short orbital moon’s energy ally excited systems that periods. The latter point means that they can be describes how orbital migra- observed relatively often as they frequently transit their budget and probing tions could accelerate over time. parent stars, resulting in a periodic slight dimming of The theory is based on the the starlight. its internal structure. idea that the internal structures of gas giant planets can evolve DIRECTIONS IN TIDAL HEATING RESEARCH on timescales comparable to The Keck Institute of Space Studies workshop identified their ages, causing the frequen- five key questions to drive future research and explora- cies of a planetary oscillation mode (i.e., the planet’s tion. vibrations) to gradually change. This evolution enables 1. What do volcanic eruptions tell us about plane- “resonance locking,” in which a planetary oscillation tary interiors? Active eruptions in the outer solar sys- mode stays nearly resonant with the forcing created by a tem are found on Io and Enceladus, and there are moon’s orbital period, producing outward migration of suggestions of such activity on Europa and on Neptune’s the moon that occurs over a timescale comparable to the large moon Triton. Volcanism is especially important for age of the solar system. This model predicts similar the study of planetary interiors, as it provides samples migration timescales but different Q values for each from depth and shows that there is sufficient internal moon. Among other results, this hypothesis explains the energy to melt the interior. Eruption styles place present-day heat flux of Enceladus without requiring it important constraints on the density and stress distri- to have formed recently, a point relevant to its current bution in the subsurface. And for tidally heated bodies, habitability and a source of debate among researchers. the properties of the erupted material can place strong constraints on the temperature and viscosity structure of OBSERVING TIDALLY HEATED EXOPLANETS a planet with depth, which is critical information for Beyond our solar system, tidal heating of exoplanets and modeling the distribution and extent of tidal dissipation. their satellites significantly enlarges the total habitable 2. How is tidal dissipation partitioned between volume in the galaxy. And as exoplanets continue to be solid and liquid materials? Tidal energy can be dissi- confirmed, researchers are increasingly studying the pated as heat in both the solid and liquid regions of a process in distant star systems. For example, seven body. The dissipation response of planetary materials roughly Earth-sized planets orbit close to TRAPPIST-1 depends on their microstructural characteristics, such as (Figure 3), a low-mass star about 40 light-years from us, grain size and melt distribution, as well as on the time with periods of a few Earth days and with nonzero eccen- scales of forcing. If forcing occurs at high frequency, tricities. Barr et al. [2018] concluded that two of these planetary materials respond via instantaneous elastic planets undergo sufficient tidal heating to support deformation. If forcing occurs at very low frequency, in a magma oceans and the other five could maintain water quasi steady state manner, materials respond with per- oceans. manent viscous deformation. Between these ends of the Highly volcanic exoplanets are considered high- spectrum, on timescales most relevant to tidal flexing of priority targets for future investigations because they planetary materials, the response is anelastic, with a likely exhibit diverse compositions and volcanic erup- time lag between an applied stress and the resulting tion styles. They are also relatively easy to characterize deformation. because of how readily volcanic gases can be studied Decades of experimental studies have focused on seismic wave attenuation here on Earth. However, seismic waves have much smaller stress amplitudes and much higher frequencies than tidal forcing, so the type of forcing relevant to tidally heated worlds remains poorly explored experimentally. For instance, it is not clear under what conditions tidal stress could alter existing grain sizes and/or melt distributions within the material being stressed. 3. Does Io have a magma ocean? To understand Io’s dynamics, such as where tidal heating occurs in the interior, we need to better understand its interior structure. Observations collected during close spacecraft flybys can determine whether Io has a magma ocean or another melt distribution (Table 1 and Figure 4). One means to study this is from magnetic measurements. Such measurements would be similar to the magnetic field mea- Fig. 3. The TRAPPIST-1 system includes seven known Earth-sized planets. Intense tidal heating surements made by the Galileo spacecraft near Io but of the innermost planets is likely. The projected habitable zone is shaded in green for the with better data on Io’s plasma environment (which is a TRAPPIST-1 system, and the solar system is shown for comparison. Credit: NASA/JPL-Caltech major source of noise), flybys optimized to the best times

28 Eos // JANUARY 2020 Table 1. Testing Models for Tidal Heating and Melt Distribution in Io

TIDAL k LIBRATION MAGNETIC MODEL 2 MAJOR LAVA HEAT FLOW OR h2 AMPLITUDE INDUCTION

I low small weak high- more polar temperature basaltic

II low small weak basaltic more equatorial

III high large strong very high equatorial or temperature uniform ultramafic

IV low small strong very high equatorial or temperature uniform ultramafic

Fig. 4. Four scenarios for the distribution of heating and melt in Io. Credit: Chuck Carter and James Tuttle Keane/Keck Institute for Space Studies rium or whether tidal migration and heating rates and volcanic activity vary over time. The orbital evolution of the system can be determined from observing the positions of the Galilean satellites and places for measuring variations in the magnetic over time. A way of verifying that the system is in equi- field, and new laboratory measurements of electrical librium is to measure the rate of change of the semima- conductivities of relevant planetary materials. jor axis for the three moons in the Laplace resonance. If A second method to investigate Io’s interior is with the system is in equilibrium, the tidal migration times- gravity science, in which the variables k2 and h2 (Table 1), cale must be identical for all three moons. Stability of the called Love numbers, express how a body’s gravitational Laplace resonance implies a specific equilibrium potential responds on a tidal timescale and its radial sur- between energy exchanges in the whole Jovian system face deformation, respectively. Each of these variables and has implications for its past and future evolution. alone can confirm or reject the hypothesis of a liquid 5. Can stable isotopes inform our understanding of layer decoupled from the lithosphere because their val- the long-term evolution of tidal heating? We lack ues are roughly 5 times larger for a liquid than a solid knowledge about the long-term evolution of tidally body. Although k2 can be measured through radio science heated systems, in part because their geologic activity (every spacecraft carries a radio telecommunication sys- destroys the older geologic record. Isotopic ratios, which tem capable of this), the measurement of h2 requires an preserve long-term records of processes, provide a altimeter or high-resolution camera as well as good potential window into these histories. If processes like knowledge of the spacecraft’s position in orbit and ori- volcanic eruptions and volatile loss lead to the preferen- entation. tial loss of certain isotopes from a moon or planet, sig- Libration amplitude provides an independent test for nificant fractionation of a species may occur over the age a detached lithosphere. The orbit of Io is eccentric, which of the solar system. However, to draw robust conclu- causes its orbital speed to vary as it goes around Jupiter. sions, we must understand the current and past pro- Its rotational speed, on the other hand, is nearly uni- cesses that affect the fractionation of these species form. Therefore, as seen from Jupiter, Io appears to wob- (Figure 5), as well as the primordial isotopic ratios from ble backward and forward, as the Moon does from the the body of interest. Measurements of isotopic mass vantage of Earth. Longitudinal libration arises in Io’s ratios—in, for example, the atmospheres and volcanic orbit because of the torque applied by Jupiter on Io’s plumes of moons or planets of interest—in combination static tidal and rotational bulge while it is misaligned with a better understanding of these fractionation pro- with the direction toward Jupiter. If there is a continuous cesses can inform long-term evolution. liquid layer within Io and the overlying lithosphere is rigid (as is thought to be needed to support tall moun- MISSIONS TO THE MOONS tains), libration amplitudes greater than 500 meters are Both the Europa Clipper and JUICE are currently in devel- expected—a scale easily measurable with repeat images opment and are expected to arrive at Jupiter in the late taken by a spacecraft. 2020s or early 2030s. One of the most important mea- 4. Is Jupiter’s Laplace system in equilibrium? The surements made during these missions could be preci- Io-Europa-Ganymede system is a complex tidal engine sion ranging during close flybys to detect changes in the that powers Io’s extreme volcanism and warms Europa’s orbits of Europa, Ganymede, and Callisto, which would water ocean. Ultimately, Jupiter’s rotational energy is provide a key constraint on equilibrium of the Jovian sys- converted into a combination of gravitational potential tem if we can acquire comparable measurements of Io. energy (in the orbits of the satellites) and heat via dissi- JUICE will be the first spacecraft to orbit a satellite (Gany- pation in both the planet and its satellites. However, we mede), providing excellent gravity, topography, magnetic do not know whether this system is currently in equilib- induction, and mass spectrometry measurements.

EARTH & SPACE SCIENCE NEWS // Eos.org 29 Fig. 5. Many potential sources, sinks, and transport processes affect chemical and isotopic species at Io. Credit: Keck Institute for Space Studies

The Dragonfly mission to Titan includes a seismome- determine neutral compositions and measure stable ter and electrodes on the landing skids to sense electric isotopes in Io’s atmosphere and plumes to address fields that may probe the depth to Titan’s interior water question 5. ocean. Potential Europa and Enceladus landers could also host seismometers. The ice giants Uranus and Neptune ACKNOWLEDGMENTS may also finally get a dedicated mission in the next We thank Michelle Judd and others at the Keck Institute decade. The Uranian system for Space Studies and all participants in the tidal heating contains six medium-sized study. Part of the research was carried out at the Jet Pro- moons and may provide pulsion Laboratory, California Institute of Technology, If there is a another test of the resonance under a contract with NASA. locking hypothesis suggested continuous liquid by Fuller et al. [2016], and Nep- REFERENCES tune’s active moon Triton is Barr, A. C., V. Dobos, and L. L. Kiss (2018), Interior structures and tidal heating in the TRAPPIST-1 planets, Astron. Astrophys., 613, A37, https://doi . org/ 10 . 1051/ 0004 - 6361/ layer within Io another strong candidate to 201731992. host an ocean. de Kleer, K., et al. (2019), Tidal heating: Lessons from Io and the Jovian system, final and the overlying The most promising avenue report, Keck Inst. for Space Studies, Pasadena, Calif., kiss . caltech . edu/ final _ reports/ to address the five key ques- Tidal _ Heating _ final _ report .pdf. tions noted at the Keck Insti- Fuller, J., J. Luan, and E. Quataert (2016), Resonance locking as the source of rapid lithosphere is rigid, tidal migration in the Jupiter and Saturn moon systems, Mon. Not. R. Astron. Soc., tute of Space Studies workshop 458(4), 3,867–3,879, https://doi . org/ 10.1093/ mnras/ stw609. libration amplitudes is a new spacecraft mission Khurana, K. K., et al. (2011), Evidence of a global magma ocean in Io’s interior, Sci- that would make multiple close ence, 332(6034), 1,186–1,189, https://doi . org/ 10.1126/ science . 1201425. could be easily flybys of Io [McEwen et al., McEwen, A. S., et al. (2019), The Io Volcano Observer (IVO): Follow the heat!, Lunar 2019], combined with labora- Planet. Sci. Conf., 50, Abstract 1316, http://archive . space . unibe . ch/ staff/ wurz/ McEwen _ LPSC _ 1316 .pdf. tory experiments and Earth- measurable with Peale, S. J., P. Cassen, and R. T. Reynolds (1979), Melting of Io by tidal dissipation, based telescopic observations. Science, 203(4383), 892–894, https://doi . org/ 10.1126/ science . 203 . 4383 . 892. repeat images taken An Io mission could characterize volcanic processes to AUTHOR INFORMATION by a spacecraft. address question 1, test interior Alfred McEwen (mcewen@lpl.arizona.edu), University models via geophysical mea- of Arizona, Tucson; Katherine de Kleer, California Insti- surements coupled with labo- tute of Technology, Pasadena; and Ryan Park, NASA Jet ratory experiments and theory Propulsion Laboratory, California Institute of Technology, to address questions 2 and 3, measure the rate of Io’s Pasadena orbital migration to determine whether the Laplace resonance is in equilibrium to address question 4, and u Read the full story at bit . ly/ Eos - Io - magma

30 Eos // JANUARY 2020 Recognize a Colleague Nominations Are Now Open for All 2020 Union and Section Honors

agu.org/nominations 32 Eos // JANUARY 2020 SEISMIC SENSORS IN ORBIT

Navigation satellites are enabling high-precision, real-time tracking of ground displacements, supplementing traditional methods for monitoring and assessing earthquakes.

By Timothy I. Melbourne, Diego Melgar, Brendan W. Crowell, and Walter M. Szeliga

The magnitude 7.1 strike-slip earthquake that occurred in the Mojave Desert near Ridgecrest, Calif., on 5 July 2019 caused the ground surface to rupture. Nearby Global Navigation Satellite Systems (GNSS) stations recorded up to 70 centimeters of offset within 30 seconds of the fault rupture. Credit: U.S. Geological Survey

EARTH & SPACE SCIENCE NEWS // Eos.org 33 IMAGINE IT’S 3:00 A.M. along the Pacific Northwest coast—it’s dark outside and most people are asleep indoors rather than alert and going about their day. Suddenly, multiple seismometers along the coast of Washington state are triggered as seismic waves emanate from a seconds-old earthquake. These initial detections are followed rapidly by subsequent triggering of a dozen more instruments spread out both to the north, toward Seattle, and to the south, toward Portland, Ore. Across the region, as the ground begins to shake and windows rattle or objects fall from shelves, many people wake from sleep—while others are slower to sense the potential danger. Within a few seconds of the seismometers being triggered, computers running long-practiced seismic location and magnitude algorithms estimate the source of the shaking: a magnitude 7.0 earthquake 60 kilometers off the Washington coast at a depth roughly consistent with the Cascadia Subduction Zone (CSZ) interface, along which one tectonic plate scrapes—and occasionally lurches—past another as it descends toward Earth’s interior. The CSZ is a well-studied fault known in the past to have produced both magnitude 9 earthquakes and large tsunamis—the last one in 1700. The initial information provided by seismometers is important in alerting not only scientists but also emergency response per- sonnel and the public to the potentially hazardous seismic activity. But whether these early incoming seismic waves truly represent a magnitude 7 event, whose caus- ative fault ruptured for 15–20 seconds, or whether instead they reflect ongoing fault slip that could last minutes and spread hundreds of kilometers along the fault—representing a magnitude 8 or even 9 earthquake— is very difficult to discern in real time using only local seismometers. It’s a vital distinction: Although a magnitude 7 quake on the CSZ could certainly cause damage, a magnitude 8 or 9 quake—poten-

A continuously telemetered GNSS station located on the Olympic Peninsula of Washington state. Deter- mining the real-time positions of hundreds of stations like this one to accuracies of a few centimeters within a global reference frame opens a new pipeline of analysis tools to monitor and mitigate risk from the seismic and tsunami hazards of the Casca- dia Subduction Zone and other fault systems around the globe. Credit: Central Washington University

34 Eos // JANUARY 2020 tially releasing hundreds of times more dozen or so GNSS stations spread along a rupture duration itself (roughly 10 seconds), energy—would shake a vastly larger region roughly 30-kilometer span of the coast another 10 or so seconds as seismic waves and could produce devastating tsunamis that might reasonably move a few tens of centi- and displacements propagated from the would inundate long stretches of coastline. meters within half a minute, whereas a fault rupture to nearby GNSS stations, and Some communities must evacuate for miles magnitude 8 event—or a magnitude 9 “full another few seconds for surface waves and to get out of the potential inundation zone, rip” along the entire subduction zone, from other crustal reverberations to dissipate meaning that every second counts. The abil- California to British Columbia—would move sufficiently such that coseismic offsets ity to characterize earthquake slip and loca- hundreds of Cascadia GNSS stations many could be cleanly estimated. Latency between tion accurately within a minute or two of a meters. Ground offset at some might exceed the time of data acquisition in the Mojave fault rupturing controls how effective early 10 meters, depending on location, but the Desert to their arrival and processing for warnings are and could thus mean the differ- timing of the offsets along the coast deter- position at Central Washington University ence between life and death for tens of thou- mined with GNSS would track the rupture was less than 1.5 seconds, a fraction of the sands of people living today along the Pacific itself. fault rupture time itself. Comparison of the Northwest coast. coseismic ground deformation estimated Enter GPS or, more generally, Global within 30 seconds of the event with that Navigation Satellite Systems (GNSS). These Although a determined several days later, using systems comprise constellations of Earth- improved GNSS orbital estimates and a lon- orbiting satellites whose signals are magnitude 7 quake ger data window, shows that the real-time recorded by receivers on the ground and offsets were accurate to within 10% of the used to determine the receivers’ precise on the Cascadia postprocessed “true” offsets estimated locations through time. GPS is the U.S. sys- from daily positions [Melgar et al., 2019]. tem, but several countries, or groups of Subduction Zone Much of the discrepancy may be attributable countries, also operate independent GNSS to rapid fault creep in the hours after the constellations, including Russia’s could certainly earthquake. GLONASS and the European Union’s Gali- leo system, among others. Prominently cause damage, a A VITAL ADDITION used for navigational purposes, GNSS FOR HAZARDS MONITORING ground receivers, which in recent years magnitude 8 or 9 This new ability to accurately gauge the have proliferated by the thousands around position of GNSS receivers within 1–2 sec- the world, now offer useful tools for rapidly quake would shake onds from anywhere on Earth has opened a and accurately characterizing large earth- new analysis pipeline that remedies known quakes—supplementing traditional seis- a vastly larger region challenges for our existing arsenal of moni- mic detection networks—as well as many and could produce toring tools. Receiver position data streams, other natural hazards. coupled to existing geophysical algorithms, devastating tsunamis allow earthquake magnitudes to be quickly AN INITIAL DEMONSTRATION ascertained via simple displacement scaling Large earthquakes both strongly shake and that would inundate relationships [Crowell et al., 2013]. Detailed deform the region around the source fault to information about fault orientation and slip extents that GNSS can easily resolve (Fig- long stretches of extent and distribution can also be mapped ure 1). With the expansion of GNSS net- nearly in real time as a fault ruptures [Min- works and continuous telemetry, seismic coastline. son et al., 2014]. These capabilities may monitoring based on GNSS measurements prove particularly useful for earthquake has come online over the past few years, early warning systems: GNSS can be incor- using continuously gathered position data The July 2019 strike-slip earthquake porated into these systems to rapidly con- from more than a thousand ground stations, sequence in the Eastern California Shear strain earthquake magnitude, which deter- a number that is steadily growing. Station Zone near Ridgecrest in the eastern Mojave mines the areal extent over which warnings positions are computed in a global reference Desert provided the first real-world demon- are issued for a given shaking intensity frame at an accuracy of a few centimeters stration of the capability of GNSS-based [Ruhl et al., 2017]. within 1–2 seconds of data acquisition in the seismic monitoring. The newly developed GNSS will never replace seismometers for field. In the United States, these data are fed GNSS monitoring systems included a dozen immediate earthquake identifications into U.S. Geological Survey (USGS) and GNSS stations from the National Science because of its vastly lower sensitivity to National Oceanic and Atmospheric Admin- Foundation–supported Network of the small ground displacements. But for large istration (NOAA) centers charged with gen- Americas (NOTA) located near the fault rup- earthquakes, GNSS will likely guide the erating and issuing earthquake and tsunami ture. Data from these stations indicated that issuance of rapid-fire revised warnings as a early warnings. the magnitude 7.1 main shock on 5 July rupture continues to grow throughout and In the scenario above, GNSS-based moni- caused coseismic offsets of up to 70 centi- beyond the timing of initial, seismometer- toring would provide an immediate discrim- meters in under 30 seconds of the initiation based characterization [Murray et al., 2019]. inant of earthquake size based on the of fault slip. Deformation measured using GNSS is also amount of displacement along the coast of Further analysis of the data showed that useful in characterizing tsunamis produced Washington state. Were it a magnitude 7, a those 30 seconds encompassed the fault by earthquakes, 80% of which in the past

EARTH & SPACE SCIENCE NEWS // Eos.org 35 century were excited either by direct seismic 6 3 uplift or subsidence of the ocean floor along 5 thrust and extensional faults [Kong et al., 2015] or by undersea landslides, such as in 4 2 Tohoku, Mw 9.1 Maule, Mw 8.8 the 2018 Palu, Indonesia, earthquake 0918, 100.4 km SJAV, 102.8 km 3 (A. Williamson et al., Coseismic or land- slide? The source of the 2018 Palu tsunami, 2 1 EarthArXiv, https://doi.org/10.31223/osf.io/ Displacement (m) Displacement (m) 1 fnz9j). Rough estimates of tsunami height may be computed nearly simultaneously 0 0 0 25 50 75 100 125 150 0 25 50 75 100 125 150 with fault slip by combining equations Time (s) Time (s) describing known hydrodynamic behavior 50 50 with seafloor uplift determined from GNSS offsets [Melgar et al., 2016]. Although GNSS

40 Iquique, Mw 8.1 El Mayor, Mw 7.2 40 won’t capture landslides or other offshore IQQE, 102.1 km CRRS, 100.0 km processes for which on-land GNSS has little 30 30 resolution, the rapidity of the method in characterizing tsunami excitation, com- 20 20 pared with the 10–20 minutes required by

Displacement (cm) Displacement (cm) global tide gauge and seismic networks and 10 10 by NOAA’s tsunami-specific Deep-Ocean 0 0 Assessment and Reporting of Tsunamis 0 25 50 75 100 125 150 0 25 50 75 100 125 150 (DART) buoy system, offers a dramatic Time (s) Time (s) potential improvement in response time for Fig. 1. Examples of GNSS three-dimensional displacement recorded roughly 100 kilometers from the hypocenters local tsunamis that can inundate coastlines of the 2011 magnitude 9.1 Tohoku earthquake in Japan, the 2010 magnitude 8.8 Maule earthquake in Chile, the within 5–15 minutes of an earthquake. 2014 magnitude 8.1 Iquique earthquake in Chile, and the 2010 magnitude 7.2 El Mayor-Cucapah earthquake in Natural hazards monitoring using GNSS Mexico. Static displacements accrue over timescales that mimic the evolution of faulting and become discernible isn’t limited to just solid Earth processes. as dynamic displacements dissipate. Note the dramatic increase in permanent offsets for the largest events, Other measurable quantities, such as tropo- increasing from about 5 centimeters for El Mayor to over 4 meters for Tohoku. The data are freely available from spheric water content, are estimated in real Ruhl et al. [2019]. time with GNSS and are now being used to Read it first on Articles are published on Eos.org before Watching Earth’s Interconnected Systems at Work they appear in the magazine. bit.ly/Eos-Earth-system Visit Eos.org daily for the latest Drones Capture Iceland’s Shrinking Glaciers news and perspectives. bit.ly/Eos-shrinking-glaciers Manure Happens: The Environmental Toll of Livestock Antibiotics bit.ly/Eos-livestock-antibiotics We Have Broken Nature into More Than 990,000 Little Pieces bit.ly/Eos-fragmenting-habitat Exposing Los Angeles’s Shaky Geologic Underbelly bit.ly/Eos-seismic-network Explaining the Missing Energy in Mars’s Electrons bit.ly/Eos-Mars-energy

36 Eos // JANUARY 2020 constrain short-term weather forecasts. for hazard reduction. The Sendai Framework ACKNOWLEDGMENTS Likewise, real-time estimates of iono- for Disaster Risk Reduction, administered Development of global GNSS seismic analy- spheric electron content from GNSS can by the United Nations Office for Disaster sis is supported by NASA-ESI grants NNX- help identify ionospheric storms (space Risk Reduction, promotes open data for 14AQ40G and 80NSSC19K0359 and USGS weather) and in mapping tsunami-excited hazard mitigation [International Union of Cooperative Agreements G17AC00344 and gravity waves in the ionosphere to provide a Geodesy and Geophysics, 2015], while profes- G19AC00264 to Central Washington Uni- more direct measurement of the propagat- sional organizations, such as the Interna- versity. Data from the Network of the ing tsunami as it crosses oceanic basins. tional Union of Geodesy and Geophysics, Americas are provided by the Geodetic promote their use for tsunami hazard miti- Facility for the Advancement of Geoscience A FUTURE OF UNIMAGINABLE POTENTIAL gation [LaBrecque et al., 2019]. (GAGE), operated by UNAVCO Inc., with Many resources beyond the rapid prolifera- support from the National Science Founda- tion of GNSS networks themselves have tion and NASA under NSF Cooperative contributed to making global GNSS hazards Agreement EAR-1724794. monitoring a reality. Unlike seismic sensors For large that measure ground accelerations or veloc- REFERENCES ities directly, GNSS positioning relies on earthquakes, GNSS Crowell, B. W., et al. (2013), Earthquake magnitude scaling using seismogeodetic data, Geophys. Res. Lett., 40(23), 6,089–6,094, high-accuracy corrections to the orbits and https:// doi . org/ 10.1002/ 2013GL058391. clocks broadcast by satellites. These correc- will likely guide the International Union of Geodesy and Geophysics (2015), Resolution tions are derived from continuous analyses 4: Real-time GNSS augmentation of the tsunami early warning system, iugg . org/ resolutions/ IUGGResolutions2015 . pdf. of global networks of ground stations. Simi- issuance of rapid- fire Kong, L. S. L., et al. (2015), Pacific Tsunami Warning System: A larly, declining costs of continuous teleme- Half-Century of Protecting the Pacific 1965–2015, 188 pp., Int. try have facilitated multiconstellation GNSS revised warnings as Tsunami Inf. Cent., Honolulu, Hawaii, unesdoc . unesco . org/ ark:/ 48223/ pf0000233564. processing, using the vast investments in a rupture continues LaBrecque, J., J. B. Rundle, and G. W. Bawden (2019), Global nav- international satellite constellations to fur- igation satellite system enhancement for tsunami early warning ther improve the precision and reliability of systems, in Global Assessment Report on Disaster Risk Reduc- to grow throughout tion, U.N. Off. for Disaster Risk Reduct., Geneva, Switzerland, real-time GNSS measurements of ground unisdr . org/ files/ 66779 _ flabrequeglobalnavigationsatellites . pdf. displacements. and beyond the Melgar, D., et al. (2016), Local tsunami warnings: Perspectives In the future, few large earthquakes in from recent large events, Geophys. Res. Lett., 43(3), 1,109–1,117, https:// doi . org/ 10.1002/ 2015GL067100. the western United States will escape nearly timing of initial, Melgar, D., et al. (2019), Real-time high-rate GNSS displacements: instantaneous measurement by real-time Performance demonstration during the 2019 Ridgecrest, CA GNSS. Throughout the seismically active seismometer-based earthquakes, Seismol. Res. Lett., in press. Minson, S. E., et al. (2014), Real-time inversions for finite fault slip Americas, from Alaska to Patagonia, models and rupture geometry based on high-rate GPS data, numerous GNSS networks in addition to characterization. J. Geophys. Res. Solid Earth, 119(4), 3,201–3,231, https:// doi . org/ NOTA now operate, leaving big earthquakes 10.1002/ 2013JB010622. Murray, J. R., et al. (2018), Development of a geodetic component without many places to hide. Mexico oper- for the U.S. West Coast Earthquake Early Warning System, ates several GNSS networks, as do Central The future holds unimaginable potential. Seismol. Res. Lett., 89(6), 2,322–2,336, https:// doi . org/ 10.1785/ 0220180162. and South American nations from Nicaragua In addition to expanding GNSS networks, Murray, J. R., et al. (2019), Regional Global Navigation Satellite to Chile. Around the Pacific Rim, Japan, New modern smartphones by the billions are System networks for crustal deformation monitoring, Seismol. Zealand, Australia, and Indonesia all oper- ubiquitous sensing platforms with real- Res. Lett., https:// doi . org/ 10.1785/ 0220190113. ate networks that together comprise thou- time telemetry that increasingly make Ruhl, C. J., et al. (2017), The value of real-time GNSS to earthquake early warning, Geophys. Res. Lett., 44(16), 8,311–8,319, sands of ground stations. many of the same GNSS measurements that https:// doi . org/ 10.1002/ 2017GL074502. In North America, nearly all GNSS net- dedicated GNSS receivers do. Crowdsourc- Ruhl, C. J., et al. (2019), A global database of strong- motion works have open data-sharing policies ing, while not yet widely implemented, is displacement GNSS recordings and an example application to PGD scaling, Seismol. Res. Lett., 90(1), 271–279, https:// doi . org/ [Murray et al., 2018]. But a global system for one path forward that could use tens of mil- 10.1785/ 0220180177. hazard mitigation can be effective only if lions of phones, coupled to machine learn- real-time data are shared among a wider set ing methods, to help fill in gaps in ground AUTHOR INFORMATION of networks and nations. The biggest displacement measurements between tra- Timothy I. Melbourne (tim@ geology . cwu . edu), remaining impediment to expanding a ditional sensors. Pacific Northwest Geodetic Array, Department global system is increasing the networks The potential of GNSS as an important of Geological Sciences, Central Washington whose data are available for monitoring. supplement to existing methods for real- University, Ellensburg; Diego Melgar, Depart- GNSS networks are expensive to deploy and time hazards monitoring has long been ment of Geological Sciences, University maintain. Many networks are built in whole touted. However, a full real-world test and of Oregon, Eugene; Brendan W. Crowell, or in part for land surveying and operate in a demonstration of this capability did not Department of Earth and Space Sciences, Uni- cost-recovery mode that generates revenue occur until the recent Ridgecrest earth- versity of Washington, Seattle; and Walter M. by selling data or derived positioning cor- quake sequence. Analyses are ongoing, but Szeliga, Pacific Northwest Geodetic Array, rections through subscriptions. At the cur- so far the conclusion is that the technique Department of Geological Sciences, Central rent time, just under 3,000 stations are performed exactly as expected—which is to Washington University, Ellensburg publicly available for hazards monitoring, say, it worked exceedingly well. GNSS- but efforts are under way to create interna- based hazards monitoring has indeed u Read the full story at bit.ly/Eos tional data sharing agreements specifically arrived. -seismic-sensors

EARTH & SPACE SCIENCE NEWS // Eos.org 37 E 38 Prizes and AGU Makes Strides in Union 2019 Awards, Medals, - Com theHonorsandRecognition year, Last AGU community. representative of the scientists within the fraction a quite prizes over thepast 5 years, nearly 30%ofthe Union awards, medals, and have women recipients, onaverage, received, the2019 payingoff.Including workis this tosaythat for2019.Weareproud pool tion nominathedeepening - in engagedactively plan to address this issue. The AGU Council multitiered acollaborative, efforts developed who spearheadour honors andrecognition thevolunteers concern, tothis Responding pool. andaskewednomination bias ofimplicit Teamobservedindicators ership - Lead for2018.TheCouncil awards packages Leadership Teamwhen itreviewed the concernraisedwas lastyear bytheCouncil underrepresentedamongawardees. This womenhavestage andotherfactors, been career controllingshownwhenhasthatfor awardhonorees ofpast analysis demographic scientists60,000 from 130-plus countries, impact. andsustained outreach, communication, education, research, tific - scien through sciences and space Earth the to contributions significant their for ognized arerec Theseindividuals andprizes. awards, Thisshift theresultseveralisoffactors. Although AGU represents more than Eos AGU NEWS AGU conferring on them the Union medals, medals, Union the them on conferring distinguished groupofscientistsby AGU honorsa Meeting, ach yearatFall

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Opposite: iStock.com/Rawpixel Opposite: iStock.com/Rawpixel M tions. Heresnowblankets EastGrosVentre Butte, justwestofJackson,inthebasin.Credit:Lori CC BY 2.0 Iverson,USFWS, ( Using dailysatelliteimagesofsnowcoverintheUpperSnake RiverBasininWyoming, researchersdevelopedasnowmeltmodelthatcouldhelpimprovestreamflowpredic- Capturing Snowmelt Patterns from Cloudy Satellite Images resulting model efficiently removes cloud The analysis. component known asprincipal method adatacompression using images Terra satellite. The authors combined the ( Spectroradiometer tured Imaging bytheModerateResolution square- ofthe images satellite ofdaily researchers drewon17 years fromyeartoyear.To pattern same spatial the theapproach, develop the observation that snowmeltinagivenregion tends tofollowthe snowmeltmonitoring. forreal-time them unsuitable delaysthatmake time andcomewith thesemethodsarecomplex ever, How- remains. wheresnowhasmeltedandit ery andtodiscern - imag andsubtract cloudcoverfromsatellite allow scientiststoidentify clouds often obscure images captured from space. Existing methods images. satellite snowmeltfromdaily eling paper, new a In released. be will water much how and when of predictions aid The new method addresses the cloud cover problem by leveraging Satellite imageseasily revealsnowmelt patterns oncleardays, but Woodruff and mod- Quallspresentanovelstrategyforefficiently kilometer Upper Snake RiverBasin in Wyoming that werecap- drinking water. Accurately modeling snowmelt in real time can water.Accurately can realtime drinking snowmeltin modeling providefresh water forvariety a ofuses, such asirrigation and any regionsaround the world rely onmountain snowmeltto MODIS) aboard NASA’s MODIS) aboardNASA’s 8,894- u Read the full stories and the latest news at Eos.org at news latest the and stories full the Read 2019) https:// melt. (Water Resources Research, ing researchers’ ability to model streamflows that result from snow- improvingrepresentations ofsnow coverinclimate models and boost as suchapplications,potential variety of a hasIt patterns. snowmelt remotely mapping snow cover that takesadvantage of consistent yearly snow telemetry( cess,documentedas byon-the-ground measurements captured by and duration - timing thepro in well asshifts ofthemelting as umes, lessare efficient. Thenewmodel accommodates different snowvol- accuracy similar methodsachieve developed but Previously cover. cloud accuracy, 85%–98% 95% with with patterns images evenforsatellite snow showedthatthemodelreproduces testing years.This additional bypixel. cover pixel cover from satellite images, allowing researchersmap to daily snow The authors note that to their knowledge, this is the first means of meansof thefirst is this knowledge, The authorsnotethattotheir testedsatelliteTheteammodelimagesthefrombyapplying to two it —Sarah Stanley,—Sarah SNOTEL) instruments. SNOTEL) Science Writer EARTH &SPACE SCIENCENEWS RESEARCH SPOTLIGHTRESEARCH bit.ly/ ccby2-0) doi . org/ 10.1029/ 2018WR024546, 2018WR024546,

E os.org

39 - RESEARCH SPOTLIGHT

The When and Where of Mesospheric Bores Revealed

espite the ambiguous homonym, mesospheric bores are any- thing but boring. Occurring in the mesosphere (50–85 kilome- Dters above Earth’s surface), the bores are a type of gravity wave disturbance that propagates through air, sometimes creating rippling patterns in high- altitude clouds that can be seen with the naked eye. The exact cause of the phenomenon is still under investigation, but previous theoretical and modeling studies have suggested that a “ducting region”—formed by a temperature inversion layer, wind shear, or both—combined with an existing gravity wave can produce the telltale ripples of a mesospheric bore as the wave is channeled through the thin “duct” layer. In a new study, Hozumi et al. move beyond theoretical considerations and present the first large-scale statistical analysis of mesospheric bores captured in satellite imagery. The data set, recorded by the Visi- ble and Near Infrared Spectral Imager on board the International Space Station, contains 306 bore events captured over 3 years, from Septem- New research shows that soil moisture plays a critical role in the formation of ber 2012 to August 2015. Although the researchers didn’t try to parse in cumulus clouds over the southern Great Plains. Credit: annca, Pixabay license detail how the bores form, the work provides a lot of new information about when and where they form, which may help reveal their under- lying mechanics. Mesospheric bores were most prevalent during the equinox seasons (fall and spring) and tended to form at equatorial latitudes. During win- Soil Moisture Drives Great ter, they were more likely to form at midlatitudes. Regardless of time of year, the bores typically propagated from the winter toward the sum- Plains Cloud Formation mer hemisphere. The authors note that this geographic and temporal distribution owering cumulus clouds often loom over the southern Great traces regions of the mesosphere that host two atmospheric tides Plains of the United States, particularly when warm, moist air with large temperature variations, a phenomenon that likely lends Trises from the soil during summer months. New research that itself to the thermal ducting theorized as a necessity for bore formation. tracked cumulus cloud formation over the course of a day demonstrates In addition, the authors posit that because the bores tend to originate that much of the complex variation in the clouds derives from local in the winter high latitudes, the polar night jet—a strong westerly variations in soil moisture, combined with pockets of cold air in the wind that develops near the edge of the polar night—may be respon- atmosphere. sible for creating the gravity waves required for the bores’ formation. Fast et al. used observational data from Oklahoma and Kansas col- ( Journal of Geophysical Research: Space Physics, https://doi. org/ 10.1029/ lected on 30 August 2016 through the Holistic Interactions of Shallow 2019JA026635, 2019) —David Shultz, Science Writer Clouds, Aerosols, and Land-Ecosystems (HI-SCALE) campaign, which studied interactions between land, vegetation, and the atmosphere. During the morning, rainless, shallow clouds formed over southeastern Oklahoma, then spread northwest into southern Kansas. By early after- noon, what had been a fairly uniform field of clouds became more complex—some regions became cloudless, whereas others saw bigger, rain- laden clouds form. The team attempted to re-create those patterns in a computer simulation, using an algorithm that tracks thousands of individual cumulus clouds at once. The researchers could faithfully represent the HI-SCALE observational data in the model only by including detailed soil moisture data from across the region. Later in the day, after about 1:00 p.m., regions of colder air surrounded by warm air, called cold In this illustration, the Visible and Near Infrared Spectral Imager aboard the Inter- pools, also played an important role, they found. The new study sug- national Space Station captures observations of airglow (green), a faint emission gests that to accurately predict how clouds will behave, climate of Earth’s atmosphere that is modulated by atmospheric waves in the mesosphere, and weather models must account for soil conditions. ( Journal of while a digital single-lens reflex camera captures background imagery. Information Advances in Modeling Earth Systems (JAMES), https://doi.org/10.1029/ about mesospheric bores is derived from the airglow observations. Credit: ISS- 2019MS001727, 2019) —Emily Underwood, Science Writer IMAP mission team

40 Eos // JANUARY 2020 RESEARCH SPOTLIGHT

Earthquake Statistics Vary with Fault Size

any natural and human-made phe- earthquakes and slow aseismic slip, or creep, nomena obey power law distribu- and compared the results with records of Mtions. In one of the most well-known earthquakes observed in nature. examples, a power law distribution describes The research revealed that although small how small earthquakes occur much more fre- seismic sources can produce identical and quently than large, potentially destructive periodic earthquakes, tremors on large faults ones. exhibit different traits, including the power Generally, the power law distribution in law distributions observed in nature. For earthquake moment holds when considering bigger faults, the rupture lengths of earth- seismic events over time on multiple faults. quakes may span several orders of magni- However, scientists still puzzle over the dis- tude and cluster in time instead of spacing tribution of rupture sizes along individual out more evenly, as they do on small seismic faults. Exceptions to the power law statistics sources. On the basis of straightforward have been observed in rare sequences known physical concepts related to fault strain and as repeating earthquakes. Instead of many the energy released during fracture forma- New research proposes an explanation for why small events and a few large ones, these tion, the study showed that the transition large faults, like the San Andreas in California, seen sequences are characterized by periodic between these types of behavior is controlled here bisecting the Carrizo Plain, typically experience earthquakes of fixed size, raising various by the ratio of a fault’s size to a length earthquakes that cluster in time and have a range of questions for researchers. Why do these related to the earthquake nucleation dimen- magnitudes—with many small events and a few sequences depart from the otherwise ubiqui- sion. large ones—whereas earthquake sequences on tous power law statistics of earthquake sizes? In essence, the study demonstrated that smaller seismic sources are sometimes character- And what distributions can we expect to occur simple, isolated faults do not necessarily pro- ized by periodic earthquakes of fixed size. Credit: on faults large enough to produce destructive duce regular and periodic earthquakes, espe- John Wiley, CC BY 3.0 (bit.ly/ccby3-0) earthquakes? cially when the faults are relatively large. In a new theoretical study, Cattania The conclusions offer insights into seismic explored the factors controlling earthquake hazard analysis. Although the simplified statistics on a single isolated fault. The author model used in the study may not adequately cases. (Geophysical Research Letters, https://doi used a two-dimensional earthquake cycle represent individual faults found in nature, .org/ 10.1029/ 2019GL083628, 2019) —Aaron model of a simple fault experiencing both the theory can be extended to more realistic Sidder, Science Writer

Atlantic Circulation Consistently Tied to Carbon Dioxide

s temperatures and atmospheric remained consistent over the past 800,000 compositions on Earth have varied years. A considerably over the past million or To create the record, the scientists used so years, the Northern Hemisphere has samples from a sediment core from Ocean experienced large-scale advances and Drilling Program Site 983, which is located off retreats of continental ice sheets at intervals the southwestern coast of Iceland. They made of between 80,000 and 120,000 years. (Cur- counts of ice-rafted terrestrial material, such rently, the planet is in an interglacial as quartz grains, as well as of Neogloboqua period—when ice sheets are smaller—that drina pachyderma, a planktic foraminifer that These photomicrographs show typical subpolar (left) began about 10,000 years ago.) These thrives in polar regions, in successive layers and polar (right) foraminiferal assemblages. The planetary-scale freeze-thaw cycles have of the core. polar assemblage is dominated by a single species, pronounced effects on nearly every aspect of The authors used changes in the presence Neogloboquadrina pachyderma, and is also full of Earth’s climate. of N. pachyderma and the ice-rafted material ice-rafted material, mostly quartz and volcanic In a new study, Barker et al. present a record as proxies for surface ocean conditions and grains. Individual shells are approximately 0.3–0.5 of North Atlantic sea surface conditions and the movement of sea ice to infer patterns of millimeter across. Credit: S. Barker argue that the relationship between the ocean circulation. This information served as Atlantic Meridional Overturning Circulation an indicator of whether conditions in past (AMOC)—the pattern of mixing between sur- intervals were polar or subpolar at Site 983. face and deep waters in the North Atlantic— Because the AMOC is believed to be the main authors believe they can infer a picture of and millennial- scale changes in atmospheric driver of millennial-scale changes in surface millennial-scale changes in the Atlantic’s carbon dioxide (CO2) concentrations has conditions (polar versus subpolar), the large-scale overturning circulation.

EARTH & SPACE SCIENCE NEWS // Eos.org 41 RESEARCH SPOTLIGHT

In summary, they report that anomalously in tandem for the past 800,000 years. Broadly viously observed at the onset of past intergla- cold and icy surface conditions recorded in the speaking, CO2 levels rise when Atlantic circu- cial periods were, more likely, part of the core correspond to past periods of weakened lation is weak and fall when it’s strong. deglacial process. This scenario would mean AMOC, whereas warmer conditions corre- The authors also say their results show that that researchers have potentially overesti- spond to stronger AMOC. it might take thousands of years for the plan- mated the trend of CO2 change during some The team then compared this new record of et’s climate to reequilibrate during deglacia- past interglacial periods. (Paleoceanography Atlantic Ocean variability with atmospheric tion after each glacial period ends (and before and Paleoclimatology, https://doi. org/10 . 1029/ CO2 changes over the same period, which the subsequent interglacial begins). If that’s 2019PA003661, 2019) —David Shultz, Science revealed that the two variables have fluctuated the case, big spikes in atmospheric CO2 pre- Writer

Treating Colloids as Clusters Better Predicts Their Behavior

n nature, the mobilization of tiny particles—such as mineral fragments or Imicrobes—from rock surfaces or other porous materials to which they’re adhered has important environmental and engineering implications, both negative and positive. Mobilized and dispersed in groundwater, the particles, or colloids, can assist in the transport of contaminants such as radionuclides and metals, the transfer of viruses and bac- teria, or the removal of pollutants from contaminated sites. So accurate predictions of potential colloid mobilization in the environment, achieved through modeling, are vitally important. Previous models describing the fate and transport of colloidal particles have consistently assumed that in saturated media, colloids detach as individual, uniformly sized particles—an assumption that contradicts substantial evidence that particles tend to cluster together. In a new study, Chequer et al. take a more realistic approach to colloidal modeling that for the first time, accounts for this evidence. In the inset of this illustration, tiny particles called colloids (e.g., yellow and orange circles) are mobilized from the sur- The team performed laboratory and mod- faces of larger grains (tan). This mobilization has important environmental and engineering implications, for exam- eling experiments that examined the mobi- ple in the removal of pollutants from contaminated sites (main image). Credit: L. Chequer, University of Adelaide lization of both single and clumped particles of latex and clay deposited onto two media: sand grains and glass beads. By varying the flow velocity, pH, and ionic strength of the clustered colloidal particles (compared with Because all current models of colloid mobilizing water, the researchers observed single particles), the clusters’ mobilization is detachment use single-particle calculations, the specific conditions under which the col- not accurately predicted with standard calcu- the new study represents an important first loid particles detached. The results indicated lations, which consider only single particles. step toward creating more realistic models of that in the lab experiments, mobilization of They contend that the ease with which col- colloid mobilization in porous media. As such, particle clusters occurred at critical water loids are mobilized ultimately depends on two this research has the potential to substan- velocities much higher than those predicted factors: the size of single particles and how tially improve the accuracy of future studies by standard theory for the detachment of sin- favorable conditions were for the initial depo- of contaminant fate and transport, as well as gle colloids. sition of clusters. These factors collectively cleanups of environmentally compromised The authors concluded that because of control whether colloidal particles deposit sites. (Water Resources Research, https://doi stronger attractive van der Waals forces acting onto a surface individually or in aggregate, as .org/10.1029/2018WR024504, 2019) —Terri between the sand grains or glass beads and well as the strength of the attachment. Cook, Science Writer

42 Eos // JANUARY 2020 RESEARCH SPOTLIGHT

An instrument tower stands at the University of Michigan Biological Station, where researchers measured stable isotopic signals in water vapor amid two plots of forest to study how disturbances in forest structure influence water transport from the land to the atmosphere. Credit: Richard Fiorella

How Forest Structure Influences the Water Cycle

orests are a critical cog in the global tion in Northern Lower Michigan: an undis- The results revealed that the disturbed water cycle: Trees pull water from the turbed control site dominated by bigtooth canopy was both drier and warmer than the F ground and release it into the atmo- aspen and paper birch and a site where undisturbed control site. The control site also sphere as vapor through pores in their leaves researchers in 2008 had purposefully killed exhibited a more stratified isotopic profile, in a process called transpiration, which can aspen and birches, giving this disturbed site suggesting less vertical mixing of the air in drive temperatures and rainfall across the a much more open canopy than the control. the forests, whereas the more open canopy globe. Forests are also dynamic ecosystems, The arrangement of trees within a forest appeared to encourage more mixing. The dif- with both natural events, such as pest infes- influences the amount of light and heat that ferences between the two sites were most tations and droughts, and anthropogenic reaches the ground, affecting not just tran- prominent in the summer and spring. activities like logging potentially causing dra- spiration but also other processes like evap- The study demonstrates that forest canopy matic changes in forest structure. Despite the oration and entrainment—the process by can regulate the rate at which moisture and important roles forests play, the relationship which air above the canopy is mixed into energy are returned to the atmosphere at a between forest structure and the global water the canopy. These processes also contribute local scale, which can in turn influence water cycle is not well understood. to the amount of water vapor that reaches the retention and the makeup of forest ecosys- To help fill gaps in our understanding of this atmosphere. tems. The results provide important context relationship, Aron et al. compared two forest Taking advantage of the fact that each of for researchers interested in modeling how sites in Michigan to find out how disturbances these processes results in distinct isotopic forest ecology and water cycles will evolve as in forest structure can influence water trans- signals in water vapor, the researchers mea- climate change progresses. ( Journal of Geo port from the land surface to the atmosphere. sured stable water isotopes at six heights in physical Research: Biogeosciences, https://doi The team selected two adjacent field sites the two forest sites during the spring, sum- .org/10.1029/2019JG005118, 2019) —Kate at the University of Michigan Biological Sta- mer, and fall of 2016. Wheeling, Science Writer

EARTH & SPACE SCIENCE NEWS // Eos.org 43 POSITIONS AVAILABLE The Career Center (findajob.agu.org) is AGU’s main resource for recruitment advertising. Atmospheric Sciences scope and impact EAPS. These posi- spatial scales – from submesoscale/ AGU offers online and tions are a central component of a mesoscale fronts and eddies to printed recruitment Assistant Professor of Earth, Atmo- large-scale interdisciplinary hiring regional, basin, and global scale cir- advertising in Eos spheric, and Planetary Sciences, effort across key strategic areas in the culations – impacts the cycling of Purdue University. The Department College, including mathematical and ocean tracers with an emphasis on to reinforce your of Earth, Atmospheric and Planetary computational foundations, quantum the Southern Ocean carbon cycle. online job visibility Sciences (EAPS), within the College computation, and data science, and Individuals will join a vigorous and your brand. Visit of Science at Purdue University, aligns with the new campus-wide interdisciplinary research group under invites applications for a tenure-track key strategic priority declared by the direction of Emeritus Professor employers.agu.org for faculty position in large-scale geo- Purdue’s Board of Trustees including Jorge Sarmiento at Princeton Univer- more information. physical fluid dynamics at the rank of the Integrative Data Science Initiative sity and in close collaboration with Assistant Professor to begin in the (see https://www.purdue.edu/data Dr. Stephen Griffies at NOAA/GFDL. 2020- 21 academic year. -science/). Purdue itself is one of The researcher will be able to take Qualifications: Candidates must the nation’s leading land- grant uni- advantage of a wide range of related Packages are available have completed their PhD in Atmo- versities, with an enrollment of over research at Princeton University and for positions that are spheric Science or related field at the 41,000 students primarily focused NOAA/GFDL, as well as external col- time of employment. Within EAPS and on STEM subjects. For more informa- laborators at the member institutions • SIMPLE TO RECRUIT Purdue, candidates will find support- tion, see https://www.purdue.edu/ of the Southern Ocean Carbon and Cli- ive colleagues and a diverse and purduemoves/initiatives/stem/index mate Observations and Modeling ◆◆ online packages to access our vibrant academic community, with .php. (SOCCOM) project sponsored by NSF Career Center audience ample opportunities for professional Application Procedure: Interested Polar Programs. Available resources ◆◆ 30-day and 60-day options and personal growth. applicants should apply at https:// include state- of-the-science ocean available The successful candidate should be career8.successfactors.com/sfcareer/ physics and biogeo chemistry models able to develop a vigorous, externally jobreqcareer?jobId=7960&company and observational data sets of South- ◆◆ prices range $475–$1,215 funded, internationally recognized =purdueuniv&username=, and sub- ern Ocean biogeochemistry with theoretical, experimental, and/or mit: 1) a curriculum vitae, 2) a research unprecedented temporal and spatial • CHALLENGING TO observational research program that statement, 3) a teaching statement, coverage. RECRUIT pursues novel integrative approaches and 4) complete contact information Candidates must have received a to study geophysical fluid interactions for at least 3 references. Ph.D. in the earth sciences, applied ◆◆ online and print packages across global- to-regional scales and Purdue University’s Department of math, or the physical, biological, or to access the wider AGU to develop a complementary teach- Earth, Atmospheric, and Planetary chemical sciences within three years community ing portfolio. Possible areas of study Sciences is committed to advancing of the starting date for the appoint- ◆◆ 30-day and 60-day options may include: planetary-scale modes diversity in all areas of faculty effort, ment. Rigorous training in oceanic available of climate variability, coupled ocean/ including: scholarship, instruction, sciences is preferred along with very atmosphere/cryosphere interactions, and engagement. Candidates should strong dynamical, modeling, and ◆◆ prices range $795–$2,691 stratosphere/troposphere interac- address at least one of these three quantitative skills. Postdoctoral tions, weather- climate interactions, areas in their cover letter, indicating appointments are initially for one year • DIFFICULT TO RECRUIT and predictability in weather and sea- their past experiences, current inter- with the renewal for subsequent years ◆◆ our most powerful packages sonal forecasts. ests or activities, and/or future goals based on satisfactory performance and for maximum multimedia The candidate’s program is to promote a climate that values continued funding. A competitive sal- exposure to the AGU expected to complement existing diversity and inclusion. ary is offered commensurate with community research within the department and Review of applications will begin experience and qualifications. teaching needs at the undergraduate January 6, 2020 and continue until the Applicants are asked to submit a ◆◆ 30-day and 60-day options and graduate levels. The potential to position is filled. Questions related to cover letter, vitae, a publication list, available develop interdisciplinary, collabora- this position should be sent to Mat- a statement of research experience ◆◆ prices range $2,245–$5,841 tive research that cuts across specialty thew Huber (eaps-faculty-search@ and interests, and names of at least areas within the department, the Col- purdue.edu). A background check will 3 references. Applicants should apply lege of Science, and Purdue’s research be required for employment in this online to https://www.princeton • FREE TO RECRUIT community is desirable. EAPS has position. Purdue University is an .edu/acad-positions/position/14501. ◆◆ these packages apply only to experienced growth in recent years, ADVANCE institution. Review of applications will begin as student and graduate student with 10 new faculty hires in the last Purdue University is an EOE/AA soon as they are received and continue roles, and all bookings are three years, and we anticipate further employer. All individuals, including until the position is filled. This posi- subject to AGU approval growth in future years. One particular minorities, women, individuals with tion is subject to the University’s area of emphasis will be in the area of disabilities, and veterans are encour- background check policy. ◆◆ eligible roles include student data sciences. We expect synergies aged to apply. Princeton University is an equal fellowships, internships, between this position and the other opportunity/affirmative action assistantships, and hires. In particular, the successful Biogeosciences employer and all qualified applicants scholarships candidate will have multiple opportu- will receive consideration for employ- nities to join transdisciplinary efforts Research at the intersection of ment without regard to age, race, in areas such as natural hazards risk ocean physics and biogeochemistry color, religion, sex, sexual orientation, Eos is published monthly. prediction, fusion of modeling and in the Program in Atmospheric and gender identity or expression, national Deadlines for ads in each issue are data science, and the food-energy- Oceanic Sciences (AOS) at Princeton origin, disability status, protected vet- published at sites. agu.org/media-kits/ water nexus. University. The AOS ocean biogeo- eran status, or any other characteristic eos-advertising-deadlines/. The College: EAPS is part of the chemistry group seeks energetic and protected by law. College of Science, which comprises enthusiastic postdoctoral researchers Eos accepts employment and the physical, computing and life sci- to participate in process-oriented Geochemistry open position advertisements ences at Purdue. It is the second- studies using theory, modeling, and from governments, individuals, organizations, and academic largest college at Purdue with over 350 observations to develop understand- Director, Center for Isotope Geo- institutions. We reserve the right to faculty and more than 6000 students. ing at the intersection of ocean phys- chemistry at Boston College accept or reject ads at our discretion. With multiple commitments of signif- ics and biogeochemistry. This effort Boston College Introduction icant investment and strong align- is part of a broad study of ocean cir- Founded in 1863, Boston College is Eos is not responsible for ment with Purdue leadership, the Col- culation, the global carbon cycle, and a Jesuit, Catholic university located six typographical errors. lege is committed to supporting climate change. Of particular interest miles from downtown Boston with an existing strengths and enhancing the is how ocean dynamics at a range of enrollment of 9,150 full- time under-

44 Eos // JANUARY 2020 POSITIONS AVAILABLE POSITIONS AVAILABLE

graduates and 4,420 graduate and ferred. One to three additional years of grative theme of Water throughout at least $22,000 for a nine month professional students. Ranked 31 postdoctoral experience in laboratory the Earth. In addition, Boston College appointment, and the cost of non- among national universities, Boston geochemistry or a related field is has announced the launch of the new resident tuition is covered. Funding College has 758 full- time and 1,096 highly desirable. One or more years of Schiller Institute for Integrated Sci- is renewable for 4 years if expectations FTE faculty, 2,750 non-faculty experience in managing a geochemical ence and Society. The emphasis of the are met. Other fellowships are avail- employees, an operating budget of laboratory is highly desirable. Schiller Institute is in interdisciplinary able from the Graduate School. Fur- $956 million, and an endowment in Occasional out of hours availability research surrounding Energy, Health, ther details are at http://www . geo . ua excess of $2.2 billion. required in case issues emerge with and Environment wherein our depart- .edu/. Applicants should contact Job Description instruments or users. Must be capable ment will play a major role. Dr. Geoff Tick (gtick@ua.edu) to The Director, Center for Isotope of lifting up to 50 pounds. The PhD and MS programs both express interest. Review of applica- Geochemistry oversees the daily oper- Closing Statement provide students with the tools they tions for Fall 2020 admission will ation and general oversight of the Boston College conducts back- need to perform novel research in the begin January 15, 2020. Center for Isotope Geochemistry. This ground checks as part of the hiring Earth and Environmental sciences. includes the Metal-Free Clean Room, process. Students combine course work with Program Director, Environmental Thermal Ionization Mass Spectrome- Boston College is an Affirmative advanced research under the supervi- Division, Bureau of Economic Geol- ter (TIMS), Isotope Ratio Mass Spec- Action/Equal Opportunity Employer sion of one or two faculty advisors. The ogy. The Bureau of Economic Geology trometer (IRMS), and other associated and does not discriminate on the basis program provides our graduates with (Bureau) at The University of Texas at instrumentation, with responsibilities of any legally protected category the disciplinary credibility and the Austin seeks a highly talented indi- including calibration, maintenance including disability and protected vet- interdisciplinary vision they need to vidual to serve as the Director of its and trouble-shooting, and user train- eran status. To learn more about how advance careers in academia, govern- Environmental Research Division. ing and support. In addition, the BC supports diversity and inclusion ment, and the private sector. This Responsibilities Director may be asked to help support throughout the university please visit includes a rigorous exploration of • Serve as part of a small, integrated other research equipment in the the Office for Institutional Diversity at the broader impacts of one’s thesis administrative team of Directors Department of Earth and Environ- https://www.bc.edu/offices/diversity research. • Manage and grow the Environ- mental Sciences. Boston College offers a broad and We encourage applications in any mental Division staff The Director will also be responsi- competitive range of benefits includ- of these fields to the PhD and MS pro- • Create and pursue a vision for ble for participation in strategic plan- ing depending on your job classifica- grams. For questions, please contact multidisciplinary environmental ning for the facility, and contribution tion eligibility; Prof. Ethan Baxter, Department Chair, research to the assessment of potential alter- Tuition remission for Employees Prof. Mark Behn, Director of Graduate • Work with Principal Investigators natives for instrument procurement, Tuition remission for Spouses and Studies, or any of our faculty. We also (PI’s) to develop sources of funding through regular consultation with Children who meet eligibility require- encourage prospective students to for existing and new multidisci- the Office of the Vice Provost for ments reach out directly to potential faculty plinary programs in the areas of sus- Research, and key faculty stakehold- Generous Medical, and Dental advisors whose research aligns with tainable water resources, coastal ers, including the Chair of the Depart- Insurance applicants’ research interests. For geology, natural hazards, induced and ment of Earth and Environmental Sci- Low-Cost Life Insurance more information, please see our naturally occurring earthquakes, car- ences. Eligibility for both 401K and Uni- department website or the Schiller bon sequestration, and geologic map- Financial oversight responsibilities versity Funded 403B Retirement Plans website. ping may include analysis of utilization, Paid Holidays Annually • Build relationships with federal prioritization, and calculation of cost Generous Sick, and Vacation Pay Lindahl Ph.D. Scholarships: The and state agencies, industry, and basis for services, and recharge rate Additional benefits can be found on University of Alabama, Department international groups that will ensure setting. The Director will directly www.bc.edu/employeehandbook of Geological Sciences seeks Ph.D. that new program opportunities are supervise and assist undergraduate Boston College’s Notice of Non students with specializations that understood and funded and graduate students each year from discrimination can be viewed at complement faculty research inter- • Determine major project staffing Boston College and outside institu- https://www . bc. edu/offices/ diversity/ ests. Exceptional students will receive and scheduling; coordinate with tions as they conduct research in the compliance/nondiscrim Research or Teaching Assistantships administrators and project PI’s to Center for Isotope Geochemistry. This and a Lindahl Scholarship totaling ensure that projects are on schedule, position reports to the Executive Interdisciplinary Director, Research Infrastructure, under the Office of the Vice Provost for Funded PhD and MS opportunities Research. in Earth and Envir mental Sciences For more information, please con- at Boston College. The Department tact Professor Ethan Baxter (ethan of Earth and Environmental Sciences .baxter@bc .edu), Chair of the Depart- at Boston College is recruiting moti- ment of Earth and Environmental Sci- vated PhD and MS students for the ences, or Joshua Rappoport, Executive coming academic year. Admitted PhD PLACE Director of Research Infrastructure and MS students will be provided (joshua.rappoport@bc.edu). funding through a combination of Full-Time Equivalent Hiring Range: teaching and research assistantships $82,050 to $102,550; salary commen- or university fellowships. surate with relevant experience. The department has grown to YOUR AD Review of applications will begin 12 full-time faculty in recent years December 2nd, and continue through including major investments in labo- the application deadline of December ratories and research infrastructure, 15th. all of which create graduate student Job link from BC website: https://bc opportunities in Climate and Environ- HERE .csod.com/ats/careersite/JobDetails mental Change (e.g., paleoclimatol- .aspx?id=3492&site=1 ogy, ice sheet dynamics, fluvial geo- Visit agu.org/advertise to learn more Requirements morphology, oceanography, and The Director should have at least marine biogeochemistry), Tectonics about employment advertising with AGU. five years of experience in isotope and Dynamics of Earth’s Interior (e.g., geochemistry including in a Clean isotope geochemistry and geochro- Room and with TIMS. A doctoral nology, geodynamics, structural geol- degree in Earth Science, Geochemis- ogy, petrology, and earthquake and try, Chemistry or a related field is pre- exploration seismology), and the inte-

EARTH & SPACE SCIENCE NEWS // Eos.org 45 POSITIONS AVAILABLE POSITIONS AVAILABLE

on budget, and research groups are Salary Range The Bureau’s facilities and state-of- Research Center, in support of NASA’s collaborating appropriately $180,000 + depending on qualifica- the-art equipment include more than Astrophysics Division in the Science • Represent the Bureau at confer- tions fifteen individual laboratories hosting Mission Directorate. SOFIA, a major ences and UT meetings. About the Bureau of Economic researchers investigating everything airborne astronomical observatory, Required Qualifications Geology from nanoparticles to basin-scale paves the way scientifically for the Ph.D. degree with major course Established in 1909, the Bureau of phenomena. soon-to-be launched James Webb work in the field of earth science. Min- Economic Geology in the Jackson To apply and for more information, Space Telescope, while simultane- imum of 12 years work experience in a School of Geosciences is the oldest and please go to https://utaustin.wd1 ously filling a unique scientific niche field related to the Bureau’s core areas second- largest organized research .myworkdayjobs.com/UTstaff/job/ in the mid- to far-infrared over the of environmental research, as per unit at The University of Texas at Aus- PICKLE -RESEARCH -CAMPUS/ longer term. USRA is seeking a world- responsibilities outlined above, or a tin. The Bureau functions as the State Program-Director_R_00006402 class SMO Director to provide scien- Master’s degree in the field of earth Geological Survey of Texas, and con- Inquiries: Recruiting@ beg.utexas tific, technical, and programmatic science, with 17 years work experience ducts basic and applied research .edu leadership of SOFIA Science Mission in the same related fields. Excellent around the world focusing on the Operations, and to ensure SOFIA sci- management and organizational abil- intersection of energy, the environ- Director, SOFIA. SOFIA, the Strato- ence remains at the forefront of ities. Previous experience as a suc- ment, and the economy. The Bureau spheric Observatory for Infrared astronomy, astrophysics, and plane- cessful leader of major research pro- partners with federal, state, and local Astronomy, is a NASA program to tary science. grams. Acknowledged contributions agencies, academic institutions, understand Cosmic Origins by study- Apply at: https://www.usra .edu/ in one or more aspects of environ- industry, nonprofit organizations, and ing the formation and evolution of careers mental research. Relevant education foundations to conduct high- quality planets, stars and galaxies, planets in and experience may be substituted as research and disseminate the results our solar system, and extreme cosmic Tenure-track Faculty Position in appropriate. to the scientific and engineering com- environments. It is the major airborne Tectonic Petrochronology. The Preferred Qualifications munities as well as to the broad public. astronomical observatory worldwide, Department of Geosciences at the Proven record of research and lead- The Bureau provides technical, educa- capable of making observations in the University of Arizona seeks to hire a ership, preferably related to the tional, and publicly accessible infor- far-infrared that are unique and tenure-track Assistant Professor in Bureau’s core areas of environmental mation via a myriad of media forms to impossible to obtain even with today’s petrochronology—an emerging field research. Demonstrated ability to Texas, the nation, and the world. largest, most advanced high-altitude that explores the power of minerals attract and administer external funds Talented people are the Bureau’s ground-based telescopes. SOFIA is an to serve as time capsules that yield from a variety of sources, including formula for success. Our staff of over international partnership, funded information about pressure, tempera- federal agencies, state and local gov- 250 includes scientists, engineers, jointly by NASA and the German Aero- ture, deformation, and interaction ernments, and industry. A strong economists, graduate students and space Center (DLR). The Universities with fluids during their evolution. The record of research publication and support staff, representing 27 coun- Space Research Association (USRA) appointee is expected to develop a presentations. Evidence of innovation tries, often working in integrated, manages SOFIA Science Mission Oper- high-profile, externally funded and ability to think creatively. multi-disciplinary research teams. ations (SMO) for the NASA Ames research program, teach undergrad-

NRC RESEARCH ASSOCIATESHIP PROGRAMS

The National Academy of Sciences, Engineering, and Medicine administers postdoctoral and senior research awards at participating federal laboratories and affiliated institutions at locations throughout the U.S and abroad. All research opportunities are open to U.S. citizens; some are open to U.S. permanent residents and foreign nationals.

We are actively seeking highly qualified candidates including recent doctoral recipients and senior researchers. Applicants should hold, or anticipate receiving, an earned doctorate in science or engineering. Awards are contingent upon completion of the doctoral degree. A limited number of opportunities in select fields are also available for graduate students. Degrees from universities abroad should be equivalent in training and research experience to a degree from a U.S. institution.

Application deadline dates (four annual review cycles): • February 1 • May 1 • August 1 • November 1

Awardee opportunities: • Conduct independent research in an area compatible with the interests of the sponsoring laboratory • Devote full-time effort to research and publication • Access the excellent and often unique facilities of the federal research enterprise • Collaborate with leading scientists and engineers at the sponsoring laboratories

Awardee benefits: • One-year award, renewable for up to three years • Stipend ranging from $45,000 to $83,000; may be higher based on experience • Health insurance (including dental and vision), relocation benefits, and professional travel allowance

Applicants should contact prospective Research Adviser(s) at the lab(s) prior to the application deadline to discuss their research interests and funding opportunities. For detailed program information, visit www.nas.edu/rap or e-mail [email protected].

46 Eos // JANUARY 2020 POSITIONS AVAILABLE

uate- and graduate-level courses in MC and Argus VI), and two ID-TIMS solid-Earth aspects of geology, and mass spectrometers. Additional contribute to departmental, univer- instrumentation is available from the sity, and external service. The position Kuiper Materials Imaging and Charac- is open to applicants who hold or are terization Facility, including two SEMs about to graduate with a Ph.D. The (one equipped with Raman), FIB-SEM, Department of Geosciences seeks TEM, and two EMPA instruments. faculty who promote diversity in The Department of Geosciences at research, education, and outreach, the University of Arizona features and who have interests in collabora- perennial top-ten ranked programs in tive research and curricular activities. geology, geophysics, and geochemis- This position has excellent oppor- try, and a growing emphasis in climate tunities for collaboration given exist- science and paleoclimatology. The ing strengths in igneous petrology/ University of Arizona also has top geochemistry, U-Th-Pb geochronol- planetary science, hydrology, and ogy (Arizona LaserChron Center), engineering departments with signif- noble gas geochemistry/geochronol- icant potential for collaboration. ogy (Arizona Noble Gas Laboratory), Review of applications will begin TIMS- based geochronology and January 6, 2020 and will continue until petrogenesis, and fission-track geo/ position is filled. Required application thermochronology, and in using this materials include: a (1) curriculum information to address problems in vitae; (2) statement of research inter- tectonics, sedimentary geology, land- ests and accomplishments; (3) state- scape evolution, paleoclimate, and ment of teaching interests and quali- planetary science. The successful can- fications; (4) vision statement didate will be encouraged to utilize describing how the candidate would existing infrastructure in geochemis- develop their research program, try and geochronology within the (5) statement describing the candi- Department of Geosciences, which date’s experience in working with includes a Hitachi SEM (with EDS, diverse students, diversifying a EBSD, and color CL capabilities), an department, or demonstrating success ELA- SC-ICPMS (Element2), an ELA- in increasing a sense of academic MC-ICPMS (Nu Plasma), two new inclusiveness; and (6) list of at least noble gas mass spectrometers (Helix three references (including mail and

AIR FORCE SCIENCE & TECHNOLOGY FELLOWSHIP PROGRAMS Postdoctoral and Senior Research Awards

The National Academies of Sciences, Engineering, and Medicine administers postdoctoral and senior research awards at the U.S. Air Force Research Laboratory (AFRL), the U.S. Air Force Institute of Technology (AFIT), and the U.S. Air Force Academy (USAFA) under the Air Force Science & Technology Fellowship Program (AF STFP).

We are actively seeking highly qualified candidates including recent doctoral recipients and senior researchers. Applicants must be U.S. citizens and should hold, or anticipate receiving, an earned doctorate in science or engineering. Awards are contingent upon completion of the doctoral degree.

Application deadline dates (four annual review cycles): • February 1 • May 1 • August 1 • November 1

Awardee opportunities: • Conduct independent research in an area compatible with the interests of the Air Force laboratories • Devote full-time effort to research and publication • Access the excellent and often unique Air Force research facilities • Collaborate with leading scientists and engineers

Awardee benefits: • Base stipend starting at $76,542; may be higher based on experience • Health insurance (including dental and vision), relocation benefits, and professional travel allowance

Applicants should contact prospective AFRL, AFIT, and USAFA Research Adviser(s) at the lab(s) prior to the application deadline to discuss their research interests and funding opportunities. For detailed program information, visit www.nas.edu/afstfp or e-mail [email protected].

EARTH & SPACE SCIENCE NEWS // Eos.org 47 POSITIONS AVAILABLE

email addresses and telephone num- the full position description, required The department hosts laboratory and a commitment to diversity. The bers) to: . Equal Opportunity application instructions. argon geochronology, fluid inclusion, developing and executing a clear Employer Minorities/Women/Vets/ The University of Rhode Island is an XRD, dendrochronology, electron vision during a period of expansion. Disabled. AA/EEOD employer. Women, persons microprobe/SEM, and incoming LA- The LPL Director works with local and of color, protected veterans, individ- ICP-MS and MC-ICP-MS labs. UNLV external stakeholders such as NASA Ocean Sciences uals with disabilities, and members of is a Carnegie top research status insti- and NSF to maintain and grow an other protected groups are encouraged tution, ranks among the nation’s most enriching environment conducive to Professor of Oceanography, Uni- to apply. diverse campuses, and has graduate excellence in planetary science versity of Rhode Island. The Grad- programs rated among the nation’s research, education, and exploration. uate School of Oceanography (GSO), Paleoceanography and top 100, including Geoscience. The For full position description and to University of Rhode Island (http:// Paleoclimatology Department is located in close prox- apply online, please see https://www www. gso. uri. edu) invites applications imity to several National Monuments .lpl. arizona. edu/director - department for the position of Professor of Ocean- Assistant Professor in Paleobiology/ and Parks, museum collections, as well -head. The University of Arizona is ography whose primary focus will be Paleontology, Department of Geo- as vast expanses of Public Lands that an EEO/AA employer– M/W/D/V. exploration that integrates ship- science, UNLV College of Sciences are rich in paleontological resources, based field programs, innovative [R0118966]. The Department of Geo- including the Tule Springs Fossil Beds Volcanology, Geochemistry, technology development (with science at the University of Nevada National Monument in the Las Vegas and Petrology emphasis on autonomous systems), Las Vegas invites applications for a Valley. and broad- based educational outreach full- time tenure- track faculty posi- Application materials must include Assistant Professor in Earth and activities. tion in Paleobiology/Paleontology at a cover letter, curriculum vitae, pro- Planetary Sciences. The Department Located on the water’s edge at the Assistant Professor level. The area posed research plan (three page limit), of Earth and Planetary Sciences (EPS) URI’s Narragansett Bay Campus, GSO of specialization is open but could statement of teaching philosophy and at Rutgers University-New Brunswick is the state’s center for marine studies, include the co-evolution of life and interests (two page limit), a statement invites applications for a tenure-track research and outreach. The successful environments, mass extinctions, of past or potential contributions to Assistant Professor with an expected applicant will assume a leadership role biotic responses to paleoclimate/pale- diversity (one page limit), 1–4 repre- start date of Sept. 1, 2020. Applicants as co-P.I. in the recently funded, 5 year oceanographic change, and/or geo- sentative publications, and contact must have a Ph.D. at the time of NOAA Ocean Exploration Cooperative logic influences on the origins, dis- information for at least four referees. appointment. Entry at a higher rank Institute led by GSO with its institu- tribution, and evolution of life. Review of applications will begin may be considered for extraordinary tional partners, the University of New Applicants whose research and teach- January 15, 2020 and continue until candidates with appropriate experi- Hampshire, the Woods Hole Oceano- ing interests complement existing the position is filled. Materials should ence. We seek outstanding candi- graphic Institution and the University departmental strengths are especially be addressed to Dr. Ganqing Jiang dates in the fields of mineralogy, of Southern Mississippi. The applicant encouraged to apply. The successful (Ganqing.Jiang@unlv.edu), Search petrology, geochemistry, and paleo- is expected to develop externally candidate is expected to establish a Committee Chair, and are to be sub- biology whose work relates to the funded research programs, advise vigorous externally funded research mitted online at https://www.unlv co-evolution of physical, chemical, graduate students, and teach under- program, contribute to excellence in .edu/ jobs. For assistance with the and biological systems of the Earth graduate and graduate courses. undergraduate and graduate teaching, application on-line portal, please and/or other rocky planetary bodies, The search will remain open until and participate in service activities. contact UNLV Employment Services at including: 1) large- scale planetary the position is filled. First consider- The applicant must have a Ph.D. in (702) 895- 2894 or hrsearch@ unlv processes and long-term evolution ation will be given to applications Geoscience or a related discipline from .edu. UNLV is an EEO/AA/Vet/Disabil- of minerals, geochemical reservoirs, received by January 11, 2020. Second a regionally accredited institution by ity Employer. atmospheres and oceans, and/or consideration may be given to appli- the start of the appointment, which planetary habitability, particularly of cations received by February 29, 2020. is anticipated to be August 2020. Sal- Planetary Sciences the early Earth; 2) mechanisms and Applications received subsequent to ary is competitive, contingent upon controls on planetary surface pro- the second consideration date (Febru- funding. Director/Department Head – Lunar cesses, and the history of their oper- ary 29, 2020) may not be given full The UNLV Geoscience Department & Planetary Laboratory/Planetary ation; and 3) long-term molecular, consideration. (http://geoscience . unlv. edu/) currently Sciences. Since its founding in 1960, evolutionary, and ecological relation- Visit https://jobs.uri.edu and has 21 faculty, ~240 undergraduate the Lunar and Planetary Laboratory ships between biodiversity and plan- search posting number (F00174) for students, and ~50 MS/PhD students. (LPL) at the University of Arizona etary change recorded in sedimentary (UArizona) has been at the forefront records. We encourage candidates of planetary science and solar systems whose interdisciplinary work crosses research. LPL currently leads some traditional departmental boundaries. TENURE-TRACK ASSISTANT of NASA’s highest-profile missions Faculty in EPS are expected to be PROFESSOR (GEOCHEMISTRY) and instruments and is continuously enthusiastic instructors, typically seeking future opportunities. LPL is teaching one course per semester The Department of Geosciences at Stony Brook University invites applications engaged in a broad range of research either in the undergraduate or grad- for a tenure-track Assistant Professor faculty position in low-temperature that includes theoretical, experimen- uate program. geochemistry. We seek a candidate with the potential to complement one tal, and observational investigations Applicants should submit a cover or more of the department’s current and traditional research strengths of our solar system, as well as exo letter; a 2-3 page statement of in sedimentary and isotope geochemistry, environmental geochemistry, planets and their origins. LPL inte- research accomplishments and vision; and planetary surfaces and who will be an effective teacher. Details of the grates spacecraft missions and cutting- a 1-2 page statement of teaching and department’s areas of research emphasis and current facilities may be found edge analytical facilities into its mentoring history with proposals for at www.stonybrook.edu/geosciences. Applicants should apply through research portfolio, and its teaching enhancing diversity within the AcademicJobsOnline.org at https://academicjobsonline.org/ajo/jobs/15294 and graduate program produces department and the university; a cur- (Position ID: 15294). Further details of the position and application procedure scholars who become leaders in the riculum vitae; plus names and contact should be obtained at www.stonybrook.edu/jobs/. Applications should be sent field. More information about LPL and information for at least three referees. by January 16, 2020 and questions may be directed to the Chair of the Search the Department of Planetary Sciences Submit all materials to [https://jobs Committee, Prof. Deanne Rogers ([email protected]). is available from lpl.arizona.edu. LPL .rutgers . edu/ postings/ 102136]. Review For a full position description or application procedures, visit: is searching for a new Director/ of applications begins November 30, www.stonybrook.edu/jobs (Ref. # F-10104-19-11) Department Head. The successful 2019 and will continue until the posi- candidate will have demonstrated tion is filled. Stony Brook University is an afﬁ rmative action/ excellence in planetary science Address questions to Kenneth equal opportunity employer and educator. research, strong leadership and man- Miller, search committee chair, at agement skills, teaching experience, kgm@eps.rutgers.edu

48 Eos // JANUARY 2020 POSTCARDS FROM THE FIELD

Greetings from Panama! this work will help improve our understanding of plant- atmosphere interactions and develop better land surface mod- Here is a snapshot of Hugo Cândido and me collecting gas els and stomatal regulation models in a changing environ- exchange data from mature trees at the Smithsonian Tropical ment. Research Institute’s Fort Sherman/San Lorenzo site north of This work is a collaboration between Arizona State Univer- Panama City. We used a crane to take most of our measure- sity (me and Benjamin Blonder), the University of British ments about 45 meters above the forest floor, struggling a bit Columbia (Hugo Cândido and Sean Michaletz), and the Smith- under constantly windy conditions. Although I suffered sonian Tropical Research Institute (Martijn Slot, Klaus Winter, through some vertigo due to my fear of heights, it was worth and Brett Wolfe). it to enjoy the beautiful blooming jacaranda. We took measurements from early morning until midafter- —Luiza Aparecido, Arizona State University, Tempe noon during the dry season to study the photosynthesis, transpiration, and stomatal conductance of 26 mature tropical trees Photo credit: Edwin Andrade with a portable photosynthesis system. We also collected micrometeorological data and thermal images of tree cano- pies to obtain leaf temperatures. These data will help us investigate whether tropical trees adopt different hydraulic strate- View more postcards at bit.ly/Eos-postcard gies in response to drying, warmer conditions. Findings from Register now for Oceans Sciences Meeting, the ocean science and oceans-connected community conference!

OSM 2020 “For a Resilient Planet” highlights include: Nainoa Thompson, Heidi Sosik, and Erik van Sebille plenary speakers | 5,600 worldwide ocean science & connected community experts, leaders and visionaries | 541 scientiﬁ c sessions | 18 unique ocean sciences topics

Hurry to secure the early registration discount by 8 January 2020!