Life in world's driest desert seen as sign of potential life on Mars

For the first time, researchers have seen life rebounding in the world's driest desert, demonstrating that it could also be lurking in the soils of Mars.

Hyperarid core of the Atacama Desert [Credit: Dirk Schulze-Makuch]

Led by Washington State University planetary scientist Dirk Schulze-Makuch, an international team studied the driest corner of South America's Atacama Desert, where decades pass without any rain.

Scientists have long wondered whether microbes in the soil of this hyperarid environment, the most similar place on Earth to the Martian surface, are permanent residents or merely dying vestiges of life, blown in by the weather.

In a new study published in the Proceedings of the National Academy of Sciences, Schulze-Makuch and his collaborators reveal that even the hyper-arid Atacama Desert can provide a habitable environment for microorganisms.

The researchers found that specialized bacteria are able to live in the soil, going dormant for decades, without water and then reactivating and reproducing when it rains.

"It has always fascinated me to go to the places where people don't think anything could possibly survive and discover that life has somehow found a way to make it work," Schulze-Makuch said. "Jurassic Park references aside, our research tell us that if life can persist in Earth's driest environment there is a good chance it could be hanging in there on Mars in a similar fashion."

The dry limit of life

When Schulze-Makuch and his collaborators went to the Atacama for the first time in 2015 to study how organisms survive in the soil of Earth's driest environment, the craziest of things happened. It rained.

After the extremely rare shower, the researchers detected an explosion of biological activity in the Atacama soil.

These are the surfaces of Mars and the Atacama Desert [Credit: NASA (left) / Alessandro Airo, TU Berlin (right)]

They used sterilized spoons and other delicate instrumentation to scoop soil samples from various depths and then performed genomic analyses to identify the different microbial communities that were reproducing in the samples. The researchers found several indigenous species of microbial life that had adapted to live in the harsh environment.

The researchers returned to the Atacama in 2016 and 2017 to follow up on their initial sampling and found that the same microbial communities in the soil were gradually reverting to a dormant state as the moisture went away.

"In the past researchers have found dying organisms near the surface and remnants of DNA but this is really the first time that anyone has been able to identify a persistent form of life living in the soil of the Atacama Desert," Schulze-Makuch said. "We believe these microbial communities can lay dormant for hundreds or even thousands of years in conditions very similar to what you would find on a planet like Mars and then come back to life when it rains."

Implications for life on Mars

While life in the driest regions of Earth is tough, the Martian surface is an even harsher environment.

It is akin to a drier and much colder version of the Atacama Desert. However it wasn't always this way.

Billions of years ago, Mars had small oceans and lakes where early lifeforms may have thrived. As the planet dried up and grew colder, these organisms could have evolved many of the adaptations lifeforms in the Atacama soil use to survive on Earth, Schulze-Makuch said.

"We know there is water frozen in the Martian soil and recent research strongly suggests nightly snowfalls and other increased moisture events near the surface," he said. "If life ever evolved on Mars, our research suggests it could have found a subsurface niche beneath today's severely hyper-arid surface."

Next Steps

On March 15, Schulze-Makuch is returning to the Atacama for two weeks to investigate how the Atacama's native inhabitants have adapted to survive. He said his research team also would like to look for lifeforms in the Don Juan Pond in Antarctica, a very shallow lake that is so salty it remains liquid even at temperatures as low as -58 degrees Fahrenheit.

"There are only a few places left on Earth to go looking for new lifeforms that survive in the kind of environments you would find on Mars," Schulze-Makuch said. "Our goal is to understand how they are able to do it so we will know what to look for on the Martian surface."

Author: Will Ferguson | Source: Washington State University [February 26, 2018]

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First evidence of surprising ocean warming around Galápagos corals

The ocean around the Galápagos Islands has been warming since the 1970s, according to a new analysis of the natural temperature archives stored in coral reefs.

Diane Thompson (left), Roberto Pépolas (center) and Alexander Tudhope (right) use a hydraulic drill to take a core
from a Porites lobata coral head near Wolf Island in the Galápagos [Credit: Jenifer Suarez, Cole lab]

The finding surprised the University of Arizona-led research team, because the sparse instrumental records for sea surface temperature for that part of the eastern tropical Pacific Ocean did not show warming.

"People didn't know that the Galápagos or eastern Pacific was warming. People theorized or suggested it was cooling," said lead author Gloria Jimenez, a UA doctoral candidate in geosciences.

Scientists thought strong upwelling of colder deep waters spared the region from the warming seen in other parts of the Pacific, she said.

"My colleagues and I show that the ocean around the northern Galápagos Islands is warming and has been since the 1970s," Jimenez said. The research is part of her doctoral work.

Jimenez studied cores taken from coral heads in the uninhabited northern part of Galápagos National Park. The cores represented the years 1940 to 2010. Corals lay down seasonal growth layers that serve as a natural archive of ocean temperatures.

Her analysis revealed that from 1979 to 2010, regional ocean temperatures increased almost 0.4 degrees F (0.2 degrees C) per decade -- about 1.1 degrees F (0.6 degrees C) overall.

The very strong El Niño of 1982-83 temporarily warmed the surrounding ocean so much that most of the corals in the southern part of the Galápagos died, said co-author Julia Cole, who collected the coral cores while she was a faculty member at the UA.

She is concerned about ocean warming around the northern Galápagos and parts of the eastern tropical Pacific.

"Warming in this area is particularly disturbing, because it's the only place that reefs have persisted in the Galápagos. This suggests those reefs are more vulnerable than we thought," said Cole, who is now a professor of earth and environmental sciences at the University of Michigan.

Cores collected in 2010 from a Porites lobate coral near Wolf Island in Galapagos Islands. The core,
now broken into three pieces, is 3.5 inches (8.9 cm) in diameter [Credit: Julia Cole © 2010]

The research paper, "Northern Galápagos corals reveal twentieth century warming in the eastern tropical Pacific," by Jimenez, Cole and their co-authors, Diane M. Thompson of Boston University in Massachusetts and Alexander W. Tudhope of the University of Edinburgh in the UK, is published in Geophysical Research Letters.

The National Science Foundation, the UK Natural Environment Research Council and the Philanthropic Education Organization Fellowship funded the research.

For 30 years, Cole, a paleoclimatologist, has been studying climate change and the El Niño/ La Niña climate cycle.

In 1989 she went to the Galápagos hoping to use the natural climate archives stored in corals to develop a long-term record of El Niño, but found that none of the large, old corals others reported had survived the intense warming of the 1982-83 El Niño.

"We went from site to site -- and they were all gone," Cole said. "One of my co-workers said, 'There used to be corals here, and now all I see is sand.'"

Years later, she heard large corals were still alive near Wolf Island in the remote northern part of the Galápagos archipelago, so in 2010 she followed up on the tip with a team that included co-authors Tudhope and Thompson, then a UA graduate student.

The team members dove to the reef and took several cores from large, blobby dome-shaped Porites lobata corals using an underwater hydraulic drill powered by vegetable oil. The three-and-a-half-inch (8.9 cm) diameter cores ranged from two to three feet long and had annual bands 0.4 to 0.8 inches (1-2 cm) wide. Each core showed damage from when the coral stopped growing during the 1982-83 El Niño and then started growing again.

Jimenez used chemical analysis to tease temperature information out of two of those coral cores.

After removing two cores from this Porites lobata coral colony near Wolf Island in the Galápagos, the University of
Arizona-led team of researchers plugged the drill holes. The cement plugs help the coral grow over the holes
and keep out animals out of the holes [Credit: Diane Thompson © 2010]

Coral skeletons are made mostly of calcium carbonate. However, corals sometimes substitute the element strontium for the calcium. Corals substitute more strontium when the water is cold and less when the water is warm, so the strontium/calcium ratio of a bit of skeleton can reveal what the water temperature was when that piece of skeleton formed.

Jimenez used a little drill bit to take a tiny sample every millimeter for the length of each core. She took 10 to 20 samples from each annual band of each core and analyzed the samples for the strontium/calcium ratio using atomic emission spectrometry.

She then used that information to create a continuous record of the region's ocean temperature from 1940 to 2010.

Because the El Niño/ La Niña climate cycle generates large fluctuations in ocean temperatures around the Galápagos and in the eastern tropical Pacific, long-term changes can be hard to spot.

Jimenez wanted to determine whether the region's ocean temperature changed significantly from 1940 to 2010. Therefore she analyzed her Galápagos coral temperature chronologies alongside published coral temperature chronologies from islands farther north and west and instrumental sea surface temperature records from the southern Galápagos town of Puerto Ayora and the Peruvian coastal town of Puerto Chicama.

Jimenez said her research convinces her that the ocean around the Galápagos and much of the eastern tropical Pacific is warming. She's concerned about the effect of warming seas.

"The Galápagos National Park has been designated a World Heritage Site because it's a special and unique place," Jimenez said. "Losing the corals would be an enormous blow to the underwater biodiversity."

Jimenez's next project involves analyzing an eight-foot-long Galápagos coral core she collected in 2015 that goes back to about 1850.

Author: Mari N. Jensen | Source: University of Arizona [February 21, 2018]

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New study brings Antarctic ice loss into sharper focus

A NASA study based on an innovative technique for crunching torrents of satellite data provides the clearest picture yet of changes in Antarctic ice flow into the ocean. The findings confirm accelerating ice losses from the West Antarctic Ice Sheet and reveal surprisingly steady rates of flow from its much larger neighbor to the east.

The flow of Antarctic ice, derived from feature tracking of Landsat imagery
[Credit: NASA Earth Observatory]

The computer-vision technique crunched data from hundreds of thousands of NASA-U.S. Geological Survey Landsat satellite images to produce a high-precision picture of changes in ice-sheet motion.

The new work provides a baseline for future measurement of Antarctic ice changes and can be used to validate numerical ice sheet models that are necessary to make projections of sea level. It also opens the door to faster processing of massive amounts of data.

“We’re entering a new age,” said the study’s lead author, cryospheric researcher Alex Gardner of NASA’s Jet Propulsion Laboratory in Pasadena, California. “When I began working on this project three years ago, there was a single map of ice sheet flow that was made using data collected over 10 years, and it was revolutionary when it was published back in 2011. Now we can map ice flow over nearly the entire continent, every year. With these new data, we can begin to unravel the mechanisms by which the ice flow is speeding up or slowing down in response to changing environmental conditions.”

The innovative approach by Gardner and his international team of scientists largely confirms earlier findings, though with a few unexpected twists.

Among the most significant: a previously unmeasured acceleration of glacier flow into Antarctica’s Getz Ice Shelf, on the southwestern part of the continent -- likely a result of ice-shelf thinning.

Speeding up in the west, steady flow in the east

The research, published in the The Cryosphere, also identified the fastest speed-up of Antarctic glaciers during the seven-year study period. The glaciers feeding Marguerite Bay, on the western Antarctic Peninsula, increased their rate of flow by 1,300 to 2,600 feet (400 to 800 meters) per year, probably in response to ocean warming.

Perhaps the research team’s biggest discovery, however, was the steady flow of the East Antarctic Ice Sheet. During the study period, from 2008 to 2015, the sheet had essentially no change in its rate of ice discharge -- ice flow into the ocean. While previous research inferred a high level of stability for the ice sheet based on measurements of volume and gravitational change, the lack of any significant change in ice discharge had never been measured directly.

The study also confirmed that the flow of West Antarctica’s Thwaites and Pine Island glaciers into the ocean continues to accelerate, though the rate of acceleration is slowing.

In all, the study found an overall ice discharge for the Antarctic continent of 1,929 gigatons per year in 2015, with an uncertainty of plus or minus 40 gigatons. That represents an increase of 36 gigatons per year, plus or minus 15, since 2008. A gigaton is one billion tons.

The study found that ice flow from West Antarctica -- the Amundsen Sea sector, the Getz Ice Shelf and Marguerite Bay on the western Antarctic Peninsula -- accounted for 89 percent of the increase.

Computer vision

The science team developed software that processed hundreds of thousands of pairs of images of Antarctic glacier movement from Landsats 7 and 8, captured from 2013 to 2015.

These were compared to earlier radar satellite measurements of ice flow to reveal changes since 2008.

“We’re applying computer vision techniques that allow us to rapidly search for matching features between two images, revealing complex patterns of surface motion,” Gardner said.

Instead of researchers comparing small sets of very high-quality images from a limited region to look for subtle changes, the novelty of the new software is that it can track features across hundreds of thousands of images per year -- even those of varying quality or obscured by clouds -- over an entire continent.

“We can now automatically generate maps of ice flow annually -- a whole year -- to see what the whole continent is doing,” Gardner said.

The new Antarctic baseline should help ice sheet modelers better estimate the continent’s contribution to future sea level rise.

“We’ll be able to use this information to target field campaigns, and understand the processes causing these changes,” Gardner said. “Over the next decade, all this is going to lead to rapid improvement in our knowledge of how ice sheets respond to changes in ocean and atmospheric conditions, knowledge that will ultimately help to inform projections of sea level change.”

Author: Pat Brennan | Source: NASA [February 21, 2018]

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Land use change has warmed Earth's surface

Natural ecosystems play a crucial role in helping combat climate change, air pollution and soil erosion. A new study by a team of researchers from the Joint Research Centre, the European Commission's science and knowledge service, sheds light on another, less well-known aspect of how these ecosystems, and forests in particular, can protect our planet against global warming.

Changes to the way land is used is having a knock-on effect on temperatures
[Credit: European Commission Joint Research Centre]

The research team used satellite data to analyse changes in global vegetation cover from 2000 to 2015 and link these to changes in the surface energy balance. Modifying the vegetation cover alters the surface properties - such as the amount of heat dissipated by water evaporation and the level of radiation reflected back into space - which has a knock-on effect on local surface temperature. Their analysis reveals how recent land cover changes have ultimately made the planet warmer.

"We knew that forests have a role in regulating surface temperatures and that deforestation affects the climate, but this is the first global data-driven assessment that has enabled us to systematically map the biophysical mechanisms behind these processes", explains Gregory Duveiller, lead author of the study.

The study also looked beyond deforestation, analysing changes between different types of vegetation, from evergreen forests to savannas, shrublands, grasslands, croplands and wetlands. However, they found that the removal of tropical evergreen forest for agricultural expansion is the vegetation cover transition most responsible for local increases in surface temperature.

From a greenhouse gas perspective, the cutting of forests might only affect the global climate in the mid-to-long term. However, the scientists point out that local communities living in areas where the trees are cut will immediately be exposed to rising temperatures.

The findings are published in Nature Communications.

Source: European Commission Joint Research Centre [February 20, 2018]

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A theory of physics explains the fragmentation of tropical forests

Tropical forests around the world play a key role in the global carbon cycle and harbour more than half of the species worldwide. However, increases in land use during the past decades caused unprecedented losses of tropical forest. Scientists at the Helmholtz Centre for Environmental Research (UFZ) have adapted a method from physics to mathematically describe the fragmentation of tropical forests. In the scientific journal Nature, they explain how this allows to model and understand the fragmentation of forests on a global scale. They found that forest fragmentation in all three continents is close to a critical point beyond which fragment number will strongly increase. This will have severe consequences for biodiversity and carbon storage.

The aerial photo shows forest fragments of the Brazilian Atlantic rainforest in Northeastern Brazil (Mata Atlantica),
surrounded by sugar cane plantations [Credit: Mateus Dantas de Paula]

In order to analyse global patterns of forest fragmentation, a UFZ research group led by Prof. Andreas Huth used remote sensing data that quantify forest cover in the tropics in an extremely high resolution of 30 meters, resulting in more than 130 million forest fragments. To their surprise they found that the fragment sizes followed on all three continents similar frequency distributions. For example, the number of forest fragments smaller than 10,000 hectares is rather similar in all three regions: 11.2 percent in Central and South America, 9.9 percent in Africa and 9.2 percent in Southeast Asia. "This is surprising because land use noticeably differs from continent to continent," says Dr. Franziska Taubert, mathematician in Huth's team and first author of the study. For instance, very large forest areas are transformed into agricultural land in the Amazon region. By contrast, in the forests of Southeast Asia, often economically attractive tree species are taken from the forest.

When searching for explanations for the identical fragmentation patterns, the UFZ modellers found their answer in physics. "The fragment size distribution follows a power law with almost identical exponents on all three continents," says biophysicist Andreas Huth. Such power laws are known from other natural phenomena such as forest fires, landslides and earthquakes. The breakthrough of their study is the ability to derive the observed power laws from percolation theory. "This theory states that in a certain phase of deforestation the forest landscape exhibits fractal, self-similar structures, i.e. structures that can be found again and again on different levels," explains Huth. "In physics, this is also referred to as the critical point or phase transition, which for example also occurs during the transition of water from a liquid to gaseous state," added co-author Dr. Thorsten Wiegand from UFZ. A particularly fascinating aspect of the percolation theory is that this universal size distribution is, at the critical point, independent of the small-scale mechanisms that led to fragmentation. This explains why all three continents show similar large-scale fragmentation patterns.

The UFZ team compared the remote sensing data of the three topical regions with several predictions of percolation theory. In support of their hypothesis they found agreement not only for the fragment size distribution, but also for two other important indicators - the fractal dimension and the length distribution of fragment edges. "This physical theory allows us to describe deforestation processes in the tropics," concludes Dr. Rico Fischer, co-author of the study. And that's not all: this approach can also be used to predict how fragmentation of tropical forests will advance over the next decades. "Particularly near the critical point, dramatic effects are to be expected even in the case of relatively minor deforestation," adds Taubert.

Using scenarios that assume different clearing and reforestation rates, the scientists modelled how many forest fragments can be expected by 2050. For example, if deforestation continues in the Central and South American tropics at the current rate, the number of fragments will increase 33-fold and their mean size will decrease from 17 ha to 0.25 ha. The fragmentation trend can only be stopped by slowing down deforestation and reforesting more areas than deforesting, which currently is a rather unlikely option. Future satellite missions, such as Tandem-L, are of great importance for the timely and reliable detection of these trends.

Advanced fragmentation of tropical forests will have severe consequences for biodiversity and carbon storage. On the one hand, biodiversity suffers because numerous rare animal species depend on large forest patches. For example, the jaguar needs around 10,000 hectares of contiguous forest to survive. On the other hand, the increasing fragmentation of forests also has a negative impact on climate. A UFZ team of scientists led by Andreas Huth described in Nature Communications in spring of last year that fragmentation of once connected tropical forest areas could increase carbon emissions worldwide by another third, as many trees die and less carbon dioxide is stored in the edge of forest fragments.

Source: Helmholtz-Centre for Environmental Research - UfZ [February 14, 2018]

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Projecting the impacts of climate change

How might climate change affect the acidification of the world's oceans or air quality in China and India in the coming decades, and what climate policies could be effective in minimizing such impacts? To answer such questions, decision makers routinely rely on science-based projections of physical and economic impacts of climate change on selected regions and economic sectors. But the projections they obtain may not be as reliable or useful as they appear: Today's gold standard for climate impact assessments—model intercomparison projects (MIPs)—fall short in many ways.

Air pollution in Bangladesh and Northern India [Credit: Jacques Descloitres,
MODIS Rapid Response Team, NASA/GSFC]

MIPs, which use detailed climate and impact models to assess environmental and economic effects of different climate-change scenarios, require international coordination among multiple research groups, and use a rigid modeling structure with a fixed set of climate-change scenarios. This highly dispersed, inflexible modeling approach makes it difficult to produce consistent and timely climate impact assessments under changing economic and environmental policies. In addition, MIPs focus on a single economic sector at a time and do not represent feedbacks among sectors, thus degrading their ability to produce accurate projections of climate impacts and meaningful comparisons of those impacts across multiple sectors.

To overcome these drawbacks, researchers at the MIT Joint Program on the Science and Policy of Global Change propose an alternative method that only a handful of other groups are now pursuing: a self-consistent modeling framework to assess climate impacts across multiple regions and sectors. They describe the Joint Program's implementation of this method and provide illustrative examples in a new study published in Nature Communications.

The Joint Program method is essentially a next-generation Integrated Assessment Model (IAM). IAMs typically come in two forms—either as simple climate models coupled with algorithms that translate increases in average global surface temperature into environmental and economic damages known as the social cost of carbon; or as more detailed Earth-system models with continually improving representation of physical impacts, coupled with economic models. The Joint Program IAM integrates a geospatially resolved physical representation of climate impacts into a coupled human and Earth system modeling framework.

Developed over the past 26 years, the MIT Integrated Global System Modeling (IGSM) framework allows researchers to custom-design climate-change scenarios and assess climate impacts under those scenarios. For a given climate change scenario, they can use the framework to analyze the chain of physical changes at the regional and sectoral levels, and then estimate economic impacts at those levels.

"The IGSM framework makes it possible to do multisectoral climate impact assessment within a single modeling framework within a single group," says Erwan Monier, lead author of the study and a principal research scientist at the Joint Program. "It's responsive to changes in environmental policies, internally consistent, and much more flexible than multimodel international exercises."

In the study, Monier and his co-authors applied the IGSM framework to assess climate impacts under different climate-change scenarios—"Paris Forever," a scenario in which Paris Agreement pledges are carried out through 2030, and then maintained at that level through 2100; and "2C," a scenario with a global carbon tax-driven emissions reduction policy designed to cap global warming at 2 degrees Celsius by 2100. The assessments show that "Paris Forever" would lead to a wide range of projected climate impacts around the world, evidenced by different levels of ocean acidification, air quality, water scarcity, and agricultural productivity in different regions. The "2C" scenario, however, would mitigate a substantial portion of these impacts. The researchers also explored additional scenarios developed by Shell International regarding the potential development of low-carbon energy technologies.

"These examples showcase the responsiveness, consistency and multisectoral capability of our approach, which we believe represents a promising direction for the climate impact modeling community," says Sergey Paltsev, a co-author of the study and deputy director of the MIT Joint Program, as well as a senior research scientist at the MIT Energy Initiative and the MIT Center for Energy and Environmental Policy Research. "Unlike traditional IAMs and MIPs, the improved coupled human-Earth system models like the IGSM framework enable researchers to design new emissions scenarios in a matter of months rather than years, avoid inconsistencies among different model components and scenarios, and analyze multiple sectors all at once."

Author: Mark Dwortzan | Source: Massachusetts Institute of Technology [February 14, 2018]

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Twenty-five years of satellite data confirm rising sea levels

Global sea level rise is not cruising along at a steady 3 mm per year, it's accelerating a little every year, like a driver merging onto a highway, according to a powerful new assessment led by CIRES Fellow Steve Nerem. He and his colleagues harnessed 25 years of satellite data to calculate that the rate is increasing by about 0.08 mm/year every year -- which could mean an annual rate of sea level rise of 10 mm/year, or even more, by 2100.

A family of sea-level-measuring satellites [Credit: NASA]

"This acceleration, driven mainly by accelerated melting in Greenland and Antarctica, has the potential to double the total sea level rise by 2100 as compared to projections that assume a constant rate -- to more than 60 cm instead of about 30." said Nerem, who is also a professor of Aerospace Engineering Sciences at the University of Colorado Boulder. "And this is almost certainly a conservative estimate," he added. "Our extrapolation assumes that sea level continues to change in the future as it has over the last 25 years. Given the large changes we are seeing in the ice sheets today, that's not likely."

If the oceans continue to change at this pace, sea level will rise 65cm (26 inches) by 2100 -- enough to cause significant problems for coastal cities, according to the new assessment by Nerem and several colleagues from CU Boulder, the University of South Florida, NASA Goddard Space Flight Center, Old Dominion University, and the National Center for Atmospheric Research. The team, driven to understand and better predict Earth's response to a warming world, published their work in the journal Proceedings of the National Academy of Sciences.

Rising concentrations of greenhouse gases in Earth's atmosphere increase the temperature of air and water, which causes sea level to rise in two ways. First, warmer water expands, and this "thermal expansion" of the oceans has contributed about half of the 7 cm of global mean sea level rise we've seen over the last 25 years, Nerem said. Second, melting land ice flows into the ocean, also increasing sea level across the globe.

The satellite record (blue line) was adjusted first to remove the effects of the 1991 Pinatubo eruption (red line)
and then to remove the influence of El Niño and La Niña (green line) [Credit: Nerem et al./PNAS]

These increases were measured using satellite altimeter measurements since 1992, including the U.S./European TOPEX/Poseidon, Jason-1, Jason-2, and Jason-3 satellite missions. But detecting acceleration is challenging, even in such a long record. Episodes like volcanic eruptions can create variability: the eruption of Mount Pinatubo in 1991 decreased global mean sea level just before the Topex/Poseidon satellite launch, for example. In addition, global sea level can fluctuate due to climate patterns such as El Niños and La Niñas (the opposing phases of the El Niño Southern Oscillation, or ENSO) which influence ocean temperature and global precipitation patterns.

So Nerem and his team used climate models to account for the volcanic effects and other datasets to determine the ENSO effects, ultimately uncovering the underlying sea-level rate and acceleration over the last quarter century. They also used data from the GRACE satellite gravity mission to determine that the acceleration is largely being driven by melting ice in Greenland and Antarctica.

The team also used tide gauge data to assess potential errors in the altimeter estimate. "The tide gauge measurements are essential for determining the uncertainty in the GMSL (global mean sea level) acceleration estimate," said co-author Gary Mitchum, USF College of Marine Science. "They provide the only assessments of the satellite instruments from the ground." Others have used tide gauge data to measure GMSL acceleration, but scientists have struggled to pull out other important details from tide-gauge data, such as changes in the last couple of decades due to more active ice sheet melt.

"This study highlights the important role that can be played by satellite records in validating climate model projections," said co-author John Fasullo, a climate scientist at the National Center for Atmospheric Research. "It also demonstrates the importance of climate models in interpreting satellite records, such as in our work where they allow us to estimate the background effects of the 1991 eruption of Mount Pinatubo on global sea level."

Although this research is impactful, the authors consider their findings to be just a first step. The 25-year record is just long enough to provide an initial detection of acceleration -- the results will become more robust as the Jason-3 and subsequent altimetry satellites lengthen the time series.

Ultimately, the research is important because it provides a data-driven assessment of how sea level has been changing, and this assessment largely agrees with projections using independent methods. Future research will focus on refining the results in this study with longer time series, and extending the results to regional sea level, so they can better predict what will happen in your backyard.

Source: University of Colorado at Boulder [February 13, 2018]

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First scientific expedition to newly exposed Antarctic ecosystem

A team of scientists, led by British Antarctic Survey (BAS), heads to Antarctica this week (14 February) to investigate a mysterious marine ecosystem that's been hidden beneath an Antarctic ice shelf for up to 120,000 years.

Larsen C ice shelf [Credit: NASA/Nathan Kurtz]

The iceberg known as A68, which is four times of London, calved off from the Larsen Ice Shelf in July 2017. The scientists will travel by ship to collect samples from the newly exposed seabed, which covers an area of around 5,818 km2. It is an urgent mission. The ecosystem that's likely been hidden beneath the ice for thousands of years may change as sunlight starts to alter the surface layers of the sea.

The international team, from nine research institutes, leaves Stanley in the Falkland Islands on 21 February to spend 3 weeks in February-March 2018 on board the BAS research ship RRS James Clark Ross. Satellite monitoring is critical for the ship to navigate through the ice-infested waters to reach this remote location.

Marine biologist Dr Katrin Linse from British Antarctic Survey is leading the mission. She says: "The calving of A68 provides us with a unique opportunity study marine life as it responds to a dramatic environmental change. It's important we get there quickly before the undersea environment changes as sunlight enters the water and new species begin to colonise. We've put together a team with a wide range of scientific skills so that we can collect as much information as possible in a short time. It's very exciting."

The team will investigate the area previously under the ice shelf by collecting seafloor animals, microbes, plankton, sediments and water samples using a range of equipment including video cameras and a special sledge pulled along the seafloor to collect tiny animals. They will also record any marine mammals and birds that might have moved into the area. Their findings will provide a picture of what life under the ice shelf was like so changes to the ecosystem can be tracked.

This newly exposed marine area is the first to benefit from an international agreement made in 2016 by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). This agreement designates Special Areas for Scientific Study in newly exposed marine areas following the collapse or retreat of ice shelves across the Antarctic Peninsula region. The agreement came following a European Union proposal to CCAMLR, led by British Antarctic Survey (BAS) scientists.

Professor David Vaughan, Science Director at BAS says: "The calving of A68 offers a new and unprecedented opportunity to establish an interdisciplinary scientific research programme in this climate sensitive region. Now is the time to address fundamental questions about the sustainability of polar continental shelves under climate change.

We need to be bold on this one. Larsen C is a long way south and there's lots of sea ice in the area, but this is important science, so we will try our best to get the team where they need to be."

Prof. Dr. Angelika Brandt from the Marine Zoology department is on board representing the Senckenberg Research Institute and Natural History Museum. During and after the Larsen-C expedition Brandt and collaborators will focus on biodiversity and assemblage structure assessment of the epi- and suprabenthic peracarid crustaceans and their respective colonisation in this newly developed benthic ecosystem.

While the team mobilises for the expedition, glaciologists and remote sensing specialists continue to monitor the movement of the Larsen C Ice Shelf. In December 2017, a team from University of Leeds worked on the remaining ice shelf to investigate changes in ice structure after the calving event, to be able to predict shelf stability in the future.

Source: Senckenberg Research Institute and Natural History Museum [February 13, 2018]

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