A pond full of decaying oak leaves soon turns as brown as tea. Eventually, much of that rotting organic matter is released into the atmosphere as carbon dioxide. Now, a new study could improve scientists’ ability to track such emissions by improving how satellites detect dissolved organic carbon (DOC) in freshwater.
Worldwide, inland waters such as rivers and lakes release about 1 billion tons of carbon as carbon dioxide (CO2) each year. By comparison, humans burning fossil fuels produced 9 billion tons of carbon as CO2 in 2010, about 20 times the weight of the world’s population at the time. Most of the emissions from freshwater bodies are produced by bacteria, which eat dissolved, microscopic specks of organic matter, digest them, and release greenhouse gas as a waste product.
Scientists are keen to track DOC using satellite imaging. Current methods use a colored component of dissolved organic matter (DOM). This metric, CDOM, can be used as a proxy because it can be visualized from space. However, it’s not clear how accurate this method is across different types of ecosystems, like pine forests and cornfields. In the new study, Li et al. ran a mesocosm experiment—an outdoor experimental system that studies the natural environment under controlled conditions—in parallel with sampling from 14 river outlets to see how reliable the ratio of DOC to CDOM really was.
The mesocosm experiment was conducted on Beaver Island, Lake Michigan. First, the authors filled six tanks with 500 gallons of clean lake water each and then put different types of leaf litter—corn, pine needles, and red maple—in mesh bags and tossed them into the tanks. They let the bags soak for 11 days, sampling the water for DOC and CDOM levels each day. To get a range of samples from the natural environment, the team also visited 14 river mouths across the Connecticut and Chippewa river watersheds. These were located in agricultural, deciduous, evergreen, and mixed ecosystems, in which different types of leaf litter found their way into the water.
Different types of leaf litter of the same biomass produced varying levels of DOC: Red maple leaves produced twice as much organic matter as the corn leaves did, for example. However, the ratio between DOC and CDOM for each type of vegetation litter stayed the same, increasing at a linear rate.
The finding fits with past studies showing that satellite CDOM measurements provide a reliable estimate of DOC, but only when a single type of vegetation dominates the watershed. In the Yukon River, where pine forests dominate, for example, the CDOM/DOM ratio remains steady as DOC increases. The method has not worked as well when used across large watersheds that include many different types of vegetation. The results of the new study indicate that scientists need to include the density and biomass of different types of vegetation in their models, according to the authors. (Journal of Geophysical Research: Biogeosciences, https://doi.org/10.1002/2017JG004179, 2018)
One year ago this month, climate researchers met at a workshop in Boulder, Colo., to fix a big glitch in the second version of the Community Earth System Model (CESM), a computer program that scientists around the world use to simulate Earth’s complex climate system. Last July, Eos reported on that glitch and the befuddlement it had caused the model’s developers.
Now, a year later, at the same annual CESM workshop, held this week again in Boulder, the team behind the model’s development has released the promised second version: CESM2. The new version offers a slew of new features that will help modelers explore the climate in far greater detail than CESM1 ever could.
“You’re driving this car, and you know it doesn’t work as well as it could.”The glitch, however, meant that the ride to this new version was not exactly smooth. Jean-François Lamarque, an atmospheric chemist at the National Center for Atmospheric Research (NCAR) who was the chief scientist behind CESM a year ago, likened the glitch to having car trouble: “You’re driving this car, and you know it doesn’t work as well as it could,” he said. Fixing it, he added, would take a great deal of work.
Fixing the Glitch
Lamarque and his team had hoped that CESM2 would debut in August of last year, but their CESM2 car kept sputtering. The issue arose when the program ran climate simulations and returned results that did not match those seen in reality—a problem if the main aim of the model is to mimic Earth’s actual climate.
“We spent 4–5 months really digging into the model.”Specifically, in CESM2 simulations, there was a stretch of about 2 decades in the middle of the 20th century that showed global temperatures minutely falling by 0.3°C or 0.4°C, despite real-world observations pointing toward a steady rise in global temperatures over the same 20-year period. This contrary trend occurred when the model calculated how sulfate aerosols changed the properties of clouds, a phenomenon known as the “aerosol indirect effect.” When sufficiently strong, this effect can cause cooling on a global scale.
To fix the glitch, a team of about 10 climate experts assembled soon after last year’s workshop to reexamine emissions data sets and to tinker with the model. “We spent 4–5 months really digging into the model,” Lamarque said.
The researchers thoroughly reviewed how the model captured cloud-aerosol interactions and compared their parameterizations against current knowledge from observations and high-resolution simulations. Through that scrutiny, they identified several problems with their real-world emissions data. They reported these problems to the data suppliers, who then gave them a new, corrected version of the data. This work revealed that “our initial choice of parameters could, and should, be modified to reduce the strength of the aerosol indirect effect,” Lamarque explained.
Despite their efforts, the contrary trend still crops up in CESM2. “But it’s much, much reduced from last year,” Lamarque said, adding that it will take many more years of work “by very smart people” to untangle what is really going on under the model’s hood. The cloud-aerosol mechanism currently outputs a temperature drop of about 0.1°C, effectively curtailing the glitch by more than half.
“We went from a standard car to a car with more features.”Despite that lingering glitch, CESM2 boasts several never-before-seen features. “We went from a standard car to a car with more features,” Lamarque said. These features “include quite substantial improvements in the representation of the physics that they are using,” added Gokhan Danabasoglu, an ocean and climate modeler at NCAR who is the current chief scientist behind CESM.
One of those new features is a capability that will allow users to model the behavior of Greenland’s ice sheet in greater detail. “You can have prognostic evolution of the Greenland ice sheet,” Danabasoglu said. This means that when the model runs, the parts of the ice sheet abutting the ocean melt at a relatively faster clip than ice farther inland, a process that more closely matches reality. This mechanism, Danabasoglu explained, is rather new among today’s climate models.
This week at the workshop in Boulder, researchers from around the world discussed the new features. One attendee, Gretchen Keppel-Aleks, an atmospheric scientist at the University of Michigan, described some of the features that she thinks will help advance her own research into the ways elements like carbon and nitrogen cycle through the environment.
“The new representation of carbon–nitrogen cycling in CESM2 will likely yield more robust projections for how terrestrial carbon cycling will change in the future,” she said. Such projections should help reduce one of the largest uncertainties for our future climate: how much anthropogenic carbon dioxide will remain in the atmosphere over time. This, she said, means that CESM2 offers a “much more sophisticated framework compared to CESM1.”
Climate researchers, it seems, are liking their new wheels.
A full list of features new to CESM2 can be found on NCAR’s website.
—Lucas Joel (email: email@example.com), Freelance Journalist
One of the most tell-tale signs of climate change is the retreat of Arctic sea ice. The decline has been especially rapid in the most recent couple of decades, and long gone are the times when thick sea ice covered most of the Arctic Ocean even in summer. This thick old sea ice has now been largely replaced with thinner and younger sea ice.
The dynamics of the younger and thinner sea ice now covering the Arctic Ocean requires new understanding of key processes that drive sea ice changeThe recent rapid decline has not been well reproduced in climate models in part because most of our fundamental understanding of Arctic sea ice stems from observations done in an era with thick old ice. We believe that the dynamics of the younger and thinner sea ice now covering the Arctic Ocean is different and requires new understanding of key processes that drive sea ice change, for this to be better reproduced by climate models.
The well-known Norwegian polar explorer and scientist, Fridtjof Nansen, drifted across the Arctic Ocean in his custom-made ship the “Fram” in 1893-1896 and revolutionized our knowledge of the north polar region. Tellingly, a similar drift conducted during the International Polar Year in 2006/7/8, took roughly half as long, as ice drift speed has increased.
In the spirit of Nansen our research group designed a scientific campaign, the Norwegian young sea ICE cruise (N-ICE2015), in drifting sea ice in the Arctic Ocean, between Svalbard and the North Pole, in order to observe the functioning of a thinner sea ice pack.
Ice floes breaking up in response to storms made it sometimes challenging to work on the sea ice. Thick snow has also accumulated on the ice floes, accumulated during several storms prior to when this photo was taken. Credit: Tor Ivan Karlsen / Norwegian Polar Institute
For this we used the ice-strengthened research vessel “Lance” as our base, conducting scientific observations from the nearby ice floes while drifting with the ice.
N-ICE2015 took place in the winter and spring of 2015, and we battled fierce winter storms, rapid ice drift, break-up of ice floes and the occasional curious polar bear that wanted to sniff our equipment.
All this, while working on sea ice only three to five feet thick, that has become the norm in this region.
Many of the results of our research campaign are now published in a joint special issue of JGR: Oceans, JGR: Atmospheres and JGR: Biogeosciences. Together, this collection provides a comprehensive examination of how the now thinner sea ice responds to forcing from atmosphere (winds, precipitation and air temperatures), and how this in turn affects the ice pack (growth, drift and deformation), affects the mixing in the ocean below and eventually influences the marine ecosystem. In a coupled system all these processes are interlinked and affect each other, creating complex feedbacks.
Multiple papers in the special issue show significant effects from short-lived but fierce storms. These frequently pass through this region. Storms bring high wind speeds, warm air and moisture to a place that is otherwise cold, dry and stable. Although short-lived (only a couple of days) storms create such intense dynamics that, for example, the air sea exchange of carbon dioxide on seasonal time scales is governed by multiple short-lived storms. Storms accumulate a deep snow pack that insulates the ice from the cold atmosphere and the ice grows thinner. The thinner ice pack is also weaker and more easily responds to wind forcing, affecting ice drift, which in turn can transfer more energy to the ocean below and allow the mixing of heat in the ocean to melt the underside of the sea ice, even in midst of winter. At most intense these processes are during or directly after storms.
Results from this experiment can serve as a guide for what to focus on in the next generation of models.These fundamental processes typically occur on very short time scales but, more importantly, also act on very small scales (order of meters rather than kilometers), much smaller than at what typical climate models can resolve processes. These need to be carefully represented in models to make realistic predictions of Arctic sea ice in the future. Results from this experiment can serve as a guide for what to focus on in the next generation of models.
—Mats A. Granskog, Norwegian Polar Institute; email: firstname.lastname@example.org
The current strategy to protect human lives and property during wildfires is to focus on the fire itself but this is only part of the impact on human health. Inhaling fine particulates in the smoke generated by wildfires causes significant and sometimes severe health impacts, especially for vulnerable populations such as children, the elderly, and those with pre-existing conditions. We are currently hampered in our ability to monitor this public health threat because we have so few air quality monitors—satellite sensors typically lack the spatial resolution to provide community-level protections.
Gupta et al.  capitalize on the revolution in the development of low cost particulate monitors to validate on-the-ground measurements with satellite proxies for fine particulates during the 2017 wine country fire in Northern California. They reveal the ability of the ground-level sensor array to identify particulate matter hotspots, and to track the movement of these hotspots as the fire evolved. They also revealed some of the limitations in both ground level monitors, namely relatively low data quality and instrumental variations, and satellite proxy measurements, namely the proxy calibration to actual particulate matter concentration at ground level. Even with these limitations, the sheer density of individual measurements can balance out instrumental bias and provide a critical new tool to protect human health during wildfire or other smoke events in areas without current monitoring capabilities.
Gupta, P., Doraiswamy, P., Levy, R., Pikelnaya, O., Maibach, J., Feenstra, B., et al. . Impact of California fires on local and regional air quality: The role of a low‐cost sensor network and satellite observations. GeoHealth, 2. https://doi.org/10.1029/2018GH000136
Despite recent congressional appropriations that reversed many of the Trump administration’s efforts to reduce science funding for current fiscal year 2018, a new report raises an alarm about what it says are the administration’s attacks on climate research and funding for it.
Ernest Moniz (right), who served as secretary of energy in the Obama administration, speaks about climate science research and threats to funding with John Podesta, founder and director of the Center for American Progress. Credit: Constance Torian/Center for American Progress
“The Trump administration’s budget proposals and explicit attacks on science, scientists, and scientific norms indicate their intent is to undermine not just individual programs, but the entire scientific process, and in so doing to cast doubt upon the severity of the climate challenge facing the United States and the world,” according to the report, titled “Burning the Data: Attacks on Climate and Energy Data and Research.” The Center for American Progress (CAP), a left-leaning think tank based in Washington, D. C., issued the report on 14 June.
The report cautions that even though Congress passed legislation in March to maintain or increase science funding for a number of federal agencies, political appointees have broad discretion to reprogram funding away from climate change–related activities, leave funds unspent, and make policy changes to alter how science is used in federal decision-making, among other measures.
Funding cuts or shifts in spending could create gaps in data for U.S. and international climate studies, according to the report. It notes “the critical importance of the federal budget process to building and maintaining the foundation of domestic and international climate and energy research.”“There is a lack of transparency in the budgeting process that will make this an extraordinary challenge for Congress and those compelled to protect the data necessary to protect the planet.”
Appropriating the Dollars “Isn’t Enough”
“Simply appropriating the dollars just isn’t enough,” said Christy Goldfuss, CAP’s senior vice president for energy and environmental policy, at a 14 June briefing to discuss the report.
“There is a lack of transparency in the budgeting process that will make this an extraordinary challenge for Congress and those compelled to protect the data necessary to protect the planet,” she said.
A Call for Vigilance Beyond the Appropriations Process
Ernest Moniz, who served as secretary of energy during the Obama administration, said at the event that “a state of vigilance is required beyond the appropriations process” and that “international concerns already have been expressed about what is going to happen if the United States creates data gaps” in climate studies.“The things that should be completely noncontroversial are the underlying data to understanding what’s happening to the Earth system.”
“The things that should be completely noncontroversial are the underlying data to understanding what’s happening to the Earth system,” said Moniz, now a principal with the Washington, D. C.–based Energy Futures Initiative. And yet, he explained, it is concerning that those underlying data could be in jeopardy.
“It doesn’t matter if you choose the frankly completely unsupportable decision about questioning the need to respond to global warming in a policy sense,” Moniz said. “No matter where you stand on that, it is completely illogical to not want to see those data continue, unless, frankly, you don’t have a pursuit for the truth and for the necessary responses at the heart of what you are doing.”
Comprehensive Earth system models (ESMs) and climate models are the main tools available for quantitative projections of future climate change and likely physical outcomes. However, diagnosing Southern Hemisphere model performance is difficult because of the spatial sparseness of field data and remaining uncertainties in reconstructions of recent real-world climate conditions. These factors limit the evaluation of ESMs and thus the reliability of their projections, especially at high spatial resolution.
The principal outcome of the workshop is a community agreement on an ensemble of metrics.To address this need, scientists from more than 17 countries, including 29 early-career scientists, gathered last October at the Scripps Institution of Oceanography for the #GreatAntarcticClimateHack, a workshop funded by the Scientific Committee on Antarctic Research’s Antarctic Climate Change in the 21st Century (AntClim21) initiative. Attendees’ intent was to decide on metrics to evaluate ESMs to improve the next generation of Intergovernmental Panel on Climate Change projections for Antarctica and the Southern Ocean. Participants included leading experts in oceanography, glaciology, atmospheric research, aquatic biogeochemistry, and biology working on past reconstructions, modern observations, and future projections.
The principal outcome of the workshop is a community agreement on an ensemble of metrics. These metrics were produced and prioritized using a bottom-up approach that allowed contributors from different disciplines to identify key aspects of model evaluation that are most important for their area of science. At the workshop, in-depth sessions were conducted on the atmosphere, ocean, sea ice, ice sheets, paleoreconstructions, ecosystems, and biogeochemistry. Discussions finalizing diagnostic tools for implementing the range of metrics are ongoing.
Key multidisciplinary insights that emerged from the workshop include the following:
Ocean subpolar gyres around Antarctica influence key aspects of coupled systems. For example, these gyres transport water masses to the Antarctic coastline, where they can interact with the ice sheets. The gyres are also critical for the dispersal of nutrients, the transport of sea ice, and the vertical mixing of water masses. Penguins that rely on these gyres for their seasonal migration will help researchers evaluate the representation of such gyres because it is now possible to outfit the penguins with global location–sensing (GLS) biologgers, which use solar cues to determine location.Sea ice connects many disciplines through its interaction with the atmosphere, ocean, and ecosystems.
Ice-ocean interactions at the grounding line (where a glacier on land extends into the water, becoming a floating ice shelf) are a principal challenge for determining ice mass loss from marine-based ice sheets. Emerging integration of grounding line behavior in coupled ice sheet models and the recent successes in drilling projects to access water masses near the grounding line provide unprecedented opportunities to assess model performance and refine Antarctic contributions to sea level rise.
Sea ice connects many disciplines through its interaction with the atmosphere (winds), ocean (temperature and currents), and ecosystems (nutrients and light). Including new data metrics, such as those from GLS tags attached to penguins and the deployment of under-ice Argo floats, provides exciting new constraints to improve model performance.
Penguins, like these near the Collins Glacier on King George Island, Antarctica, provide one of several sources of metrics to help improve Earth system models and climate models for the Southern Hemisphere. Credit: Alia Lauren Khan
In the upcoming World Climate Research Programme’s Climate Model Intercomparison Project Phase 6 (CMIP6), routine benchmarking and evaluation will be a key advance on previous CMIP exercises. Meeting participants agreed that the Earth System Model Evaluation Tool (ESMValTool) will play a valuable contributing role in CMIP. ESMValTool aims to facilitate the evaluation of comprehensive ESMs, raise the standard for model evaluation, and facilitate participation in, and analysis of, CMIP6 and related initiatives. Subsets of the metrics discussed at the workshop are being developed for implementation as part of an Antarctic and Southern Ocean contribution to ESMValTool.
More details can be found at the workshop’s website.
—Alia L. Khan (email: email@example.com; @AliaLaurenKhan), National Snow and Ice Data Center, Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder; Thomas J. Bracegirdle, British Antarctic Survey, Cambridge, U.K.; and Joellen L. Russell, University of Arizona, Tucson
Lakes of lava and hundreds of volcanoes dot the surface of Jupiter’s moon Io, some spewing lava dozens of kilometers into the air. Only slightly larger than our own planet’s moon, Io is the most volcanically active place in the solar system. Its thin atmosphere is made up largely of sulfur oxides. As Io orbits, neutral gas particles escape its atmosphere and collide with electrons, giving rise to a donut-shaped cloud of ionized particles around Jupiter, known as the Io plasma torus.
Exactly how those neutral gases escape Io’s atmosphere is not well understood, however. Previous studies have shown that most atomic oxygen and sulfur escape Io’s atmosphere by colliding with energetic particles, such as torus ions, which bump the particles out of the atmosphere in a process known as atomic sputtering. Some of the particles escape from Io’s gravity and form clouds of neutral sulfur and oxygen. Here Koga et al. provide new insights into the role of the neutral cloud in the Io plasma torus.
The team took advantage of data collected by Japan’s Hisaki satellite, which launched in 2013 and became the first space telescope to observe planets like Mars and Jupiter from Earth’s orbit. The researchers used spectrographic data from the Extreme Ultraviolet Spectroscope for Exospheric Dynamic (EXCEED) instrument aboard the satellite to measure atomic emissions at 130.4 nanometers around Io’s orbit. The measurements were collected over 35 days between November and December 2014, a relatively calm volcanic period for the moon.
The authors found that Io’s oxygen cloud has two distinct regions: a dense area that spreads inside Io’s orbit, called the “banana cloud,” and a more diffuse region, which spreads all the way out to 7.6 Jovian radii (RJ). The team plugged the satellite observations into an emissions model to estimate the atomic oxygen number density. They found more oxygen inside Io’s orbit than previously thought, with a peak density of 80 atoms per cubic centimeter at a distance of 5.7 RJ. The team also calculated a source rate of 410 kilograms per second, which is consistent with previous estimates.
This study provides the first good look at Io’s neutral cloud, which has historically been too dim to measure. Neutral particles from Io’s atmosphere are one of the primary sources for charged particles in Jupiter’s massive magnetosphere. Ultimately, the authors note, a better understanding of the neutral cloud will provide important insights into the gas giant’s magnetosphere. (Journal of Geophysical Research: Space Physics, https://doi.org/10.1029/2018JA025328, 2018)
On 1 May, the National Academy of Sciences elected 84 new members and 21 foreign associates, several of whom are members of the Earth and space science community. Newly elected members and their affiliations at the time of election are as follows: David Bercovici, Frederick W. Beinecke Professor of Geology and Geophysics at Yale University in New Haven, Conn.; Kristie A. Boering, professor of chemistry and of Earth and planetary science at University of California, Berkeley; James F. Kasting, Evan Pugh Professor in the Department of Geosciences at Pennsylvania State University, University Park; Michael Manga, professor of Earth and planetary sciences at University of California, Berkeley; Eric J. Rignot, Donald Bren Professor of Earth System Science at University of California, Irvine; Diana Harrison Wall, senior research scientist in the Natural Resource Ecology Laboratory and professor of biology and director of the School of Global Environmental Sustainability, Colorado State University, Fort Collins; and Cathy L. Whitlock, professor of Earth sciences at Montana State University in Bozeman and fellow of the Montana Institute on Ecosystems.
Explosive volcanic eruptions that shot jets of hot ash, rock and gas skyward are the likely source of a mysterious Martian rock formation, a new study finds. The new finding could add to scientists’ understanding of Mars’s interior and its past potential for habitability, according to the study’s authors.
The Medusae Fossae Formation is a massive, unusual deposit of soft rock near Mars’s equator, with undulating hills and abrupt mesas. Scientists first observed the Medusae Fossae with NASA’s Mariner spacecraft in the 1960s but were perplexed as to how it formed.
Now, new research suggests the formation was deposited during explosive volcanic eruptions on the Red Planet more than 3 billion years ago. The formation is about one-fifth as large as the continental United States and 100 times more massive than the largest explosive volcanic deposit on Earth, making it the largest known explosive volcanic deposit in the solar system, according to the study’s authors.
“This is a massive deposit, not only on a Martian scale, but also in terms of the solar system, because we do not know of any other deposit that is like this,” said Lujendra Ojha, a planetary scientist at Johns Hopkins University in Baltimore and lead author of the new study published in the Journal of Geophysical Research: Planets, a journal of the American Geophysical Union.
This graphic shows the relative size of the Medusae Fossae Formation compared to Fish Canyon Tuff, the largest explosive volcanic deposit on Earth. The Medusae Fossae has an area of about 2 million square kilometers, which is roughly one-fifth the size of the continental United States. Fish Canyon Tuff, when it was deposited, covered an area of about 30,000 square kilometers, roughly the size of the state of Maryland. Credit: AGU.
Formation of the Medusae Fossae would have marked a pivotal point in Mars’s history, according to the study’s authors. The eruptions that created the deposit could have spewed massive amounts of climate-altering gases into Mars’s atmosphere and ejected enough water to cover Mars in a global ocean more than 9 centimeters (4 inches) thick, Ojha said.
Greenhouse gases exhaled during the eruptions that spawned the Medusae Fossae could have warmed Mars’s surface enough for water to remain liquid at its surface, but toxic volcanic gases like hydrogen sulfide and sulfur dioxide would have altered the chemistry of Mars’s surface and atmosphere. Both processes would have affected Mars’s potential for habitability, Ojha said.
Determining the Source of the Rock
The Medusae Fossae Formation consists of hills and mounds of sedimentary rock straddling Mars’s equator. Sedimentary rock forms when rock dust and debris accumulate on a planet’s surface and cement over time. Scientists have known about the Medusae Fossae for decades, but were unsure whether wind, water, ice or volcanic eruptions deposited rock debris in that location.
A global geographic map of Mars, with the location of the Medusae Fossae Formation circled in red. Click image for larger version. Credit: MazzyBor, CC BY-SA 4.0 via Wikimedia Commons
Previous radar measurements of Mars’s surface suggested the Medusae Fossae had an unusual composition, but scientists were unable to determine whether it was made of highly porous rock or a mixture of rock and ice. In the new study, Ojha and a colleague used gravity data from various Mars orbiter spacecraft to measure the Medusae Fossae’s density for the first time. They found the rock is unusually porous: it’s about two-thirds as dense as the rest of the Martian crust. They also used radar and gravity data in combination to show the Medusae Fossae’s density cannot be explained by the presence of ice, which is much less dense than rock.
Because the rock is so porous, it had to have been deposited by explosive volcanic eruptions, according to the researchers. Volcanoes erupt in part because gases like carbon dioxide and water vapor dissolved in magma force the molten rock to rise to the surface. Magma containing lots of gas explodes skyward, shooting jets of ash and rock into the atmosphere.
A 13-kilometer (8-mile) diameter crater being infilled by the Medusae Fossae Formation. Credit: High Resolution Stereo Camera/European Space Agency.
Ash from these explosions plummets to the ground and streams downhill. After enough time has passed, the ash cements into rock, and Ojha suspects this is what formed the Medusae Fossae. As much as half of the soft rock originally deposited during the eruptions has eroded away, leaving behind the hills and valleys seen in the Medusae Fossae today.
Understanding Mars’s Interior
The new findings suggest the Martian interior is more complex than scientists originally thought, according to Ojha. Scientists know Mars has some water and carbon dioxide in its crust that allow explosive volcanic eruptions to happen on its surface, but the planet’s interior would have needed massive amounts of volatile gases—substances that become gas at low temperatures— to create a deposit of this size, he said.
“If you were to distribute the Medusae Fossae globally, it would make a 9.7-meter (32-foot) thick layer.” Ojha said. “Given the sheer magnitude of this deposit, it really is incredible because it implies that the magma was not only rich in volatiles and also that it had to be volatile-rich for long periods of time.”
The new study shows the promise of gravity surveys in interpreting Mars’s rock record, according to Kevin Lewis, a planetary scientist at Johns Hopkins University and co-author of the new study. “Future gravity surveys could help distinguish between ice, sediments and igneous rocks in the upper crust of the planet,” Lewis said.
The Gravity Recovery and Climate Experiment (GRACE) satellite mission has proved very useful for tracking fluctuations in terrestrial water storage, but suffers from very low spatial resolution, meaning only broad fluctuations across hundreds of kilometers can be detected. Karegar et al.  present a hybrid inverse modeling approach that combines GRACE data with local GPS measurements of vertical ground surface displacements and a high-resolution hydrologic model. Combining these three independent data sources within two mathematical approaches, each component based on different assumptions and principles, the authors bridge scales and produce more precise estimates of terrestrial water mass variations. This multi-faced inversion approach can provide better constraints on water cycle processes, inform improved hydrologic modeling and contribute to climate monitoring efforts.
Citation: Karegar, M. A., Dixon, T. H., Kusche, J., & Chambers, D. P. . A new hybrid method for estimating hydrologically induced vertical deformation from GRACE and a hydrological model: An example from Central North America. Journal of Advances in Modeling Earth Systems, 10. https://doi.org/10.1029/2017MS001181