Two million-year-old ice cores provide first direct observations of an ancient climate

By: Thomas Schmitt Attorney on November 21, 2019 / comment : 0 Antarctic, Climate Change, Earth Science, Palaeoclimate, Palaeontology

Princeton University-led researchers have extracted 2 million-year-old ice cores from Antarctica that provide the first direct observations of Earth's climate at a time when the furred early ancestors of modern humans still roamed.

Princeton University-led researchers have extracted 2 million-year-old ice cores from Antarctica -- the oldest yet recovered -- that provide the first direct observations of prehistoric atmospheric conditions and temperatures. They used data from the ice cores to answer long-held questions about how our current colder, longer glacial cycle emerged [Credit: Sean Mackay, Boston University]

Gas bubbles trapped in the cores -- which are the oldest yet recovered -- contain pristine samples of carbon dioxide, methane and other gases that serve as "snapshots" of prehistoric atmospheric conditions and temperatures, the researchers recently reported in the journal Nature. The cores were collected in the remote Allan Hills of Antarctica.

First author Yuzhen Yan, who received his Ph.D. in geosciences from Princeton in 2019, explained that because ice flows and compresses over time, continual ice cores only extend back to 800,000 years ago. The cores he and his co-authors retrieved are like scenes collected from a very long movie that do not show the whole film, but convey the overall plot.

"You don't get a sense of how things changed continually, but you get an idea of big changes over time," said Yan, whose graduate research on ice cores supported by a 2016 Walbridge Fund Graduate Award for Environmental Research from the Princeton Environmental Institute (PEI) was a basis for the current work.

The ice cores reported in Nature are the latest to come out of the research group of senior author John Higgins, a Princeton associate professor of geosciences, PEI associated faculty and Yan's doctoral co-adviser. A previous team led by Higgins recovered a 1 million-year-old ice core from the Allan Hills, which was the oldest ice core ever recorded by scientists when it was reported in the journal Proceedings of the National Academy of Sciences in 2015. The cores were dated by measuring isotopes of the gas argon trapped in bubbles in the ice, a technique developed by co-author Michael Bender, Princeton professor of geosciences, emeritus, and PEI associated faculty.

Gas bubbles trapped in the cores contain pristine samples of carbon dioxide, methane and other gases that serve  as 'snapshots' of the ancient climate. Because ice flows and compresses over time, the cores the researchers retrieved are like scenes collected from a very long movie that do not show the whole film, but convey the overall plot [Credit: Sean Mackay, Boston University]

"The ability to measure atmospheric composition directly is one of the biggest advantages of ice cores," Yan said. "That's why people spend years and years in the most isolated places getting them."

In the latest publication, the researchers use data from the ice cores to answer long-held questions about how our current glacial cycle emerged. Up until roughly 1.2 million years ago, Earth's ice ages consisted of thinner, smaller glaciers that came and went every 40,000 years on average.

Then, after what is known as the Mid-Pleistocene Transition, there emerged our current world characterized by colder and longer glacial cycles of 100,000 years. The two periods are known as the 40k and 100k world, respectively.

Some existing theories have stated that the 100k world -- which includes the last ice age that ended 11,700 years ago -- came about because of a long-term decline in atmospheric carbon dioxide, Yan said. But the researchers found that this was not the case -- average carbon dioxide was relatively steady through the 40k and 100k worlds. While the lowest temperatures and carbon dioxide levels of the 40k world were greater than the low points of the 100k world, the highest levels of both ages were similar.

"It could be the case that after the Mid-Pleistocene Transition, something occurred that lowered global glacial temperatures and atmospheric carbon dioxide values," Yan said. "This is the first time we have direct access to these greenhouse gas measurements. The ice core also opens up an array of new measurement possibilities that can give us insights into the 40k world when glacial cycles were very different from what we have today."

The researchers collected the 2 million-year-old ice cores in the remote Allan Hills, where high winds help create  the environmental conditions that draw ancient ice toward the surface. They found that although a long-term decline in atmospheric carbon dioxide did not directly lead to today's colder glacial cycle, temperature and global ice volume nonetheless tracked carbon dioxide closely [Credit: Sean Mackay, Boston University]

Although a long-term decline in average atmospheric carbon dioxide may not have directly led to the 100k world, the researchers nonetheless observed a correlation between carbon dioxide and global temperature, Bender said.

"To say that carbon dioxide is not a factor would be completely wrong," Bender said. "During the 40,000- and 100,0000-year glacial-interglacial cycles, temperature and global ice volume tracks carbon dioxide rather closely. Carbon dioxide changes are required to get from the cooler glacial temperatures to the warmer interglacial temperatures."

The amount of carbon dioxide now in the atmosphere tops 400 parts-per-million (ppm), which is nearly 100 ppm higher than the highest levels of the 40k world, Yan said.

"We're seeing carbon dioxide levels not seen in 2 million years," Yan said. "While our data suggest that long-term carbon dioxide decline was not the decisive factor in the Mid-Pleistocene Transition, it does not mean that carbon dioxide does not have the capability to bring about global-scale changes.

"We're in a different situation now -- carbon dioxide is the major player in our current world," he said. "If we want to look into the geologic past for an analogy of what's going on in our world today, we need to go beyond 2 million years to find it."

Author: Morgan Kelly | Source: Princeton University [November 21, 2019]

Unless warming is slowed, emperor penguins will be marching towards extinction

By: Thomas Schmitt Attorney on November 07, 2019 / comment : 0 Antarctic, Climate Change, Ecosystems, Endangered Species, Natural Heritage, Wildlife

Emperor penguins are some of the most striking and charismatic animals on Earth, but a new study from the Woods Hole Oceanographic Institution (WHOI) has found that a warming climate may render them extinct by the end of this century. The study, which was part of an international collaboration between scientists, published in the journal Global Change Biology.

The fate of emperor penguins is largely tied to sea ice, making them particulary vulnerable to warming [Credit: Stephanie Jenouvrier, Woods Hole Oceanographic Institution]

"If global climate keeps warming at the current rate, we expect emperor penguins in Antarctica to experience an 86 percent decline by the year 2100," says Stephanie Jenouvrier, a seabird ecologist at WHOI and lead author on the paper. "At that point, it is very unlikely for them to bounce back."

The fate of the penguins is largely tied to the fate of sea ice, which the animals use as a home base for breeding and molting, she notes. Emperor penguins tend to build their colonies on ice with extremely specific conditions -- it must be locked in to the shoreline of the Antarctic continent, but close enough to open seawater to give the birds access to food for themselves and their young. As climate warms, however, that sea ice will gradually disappear, robbing the birds of their habitat, food sources, and ability to hatch chicks.

Jenouvrier and her team conducted the study by combining two existing computer models. The first, a global climate model created by the National Center for Atmospheric Research (NCAR), offered projections of where and when sea ice would form under different climate scenarios. The second, a model of the penguin population itself, calculated how colonies might react to changes in that ice habitat.


"We've been developing that penguin model for 10 years," says Jenouvrier. "It can give a very detailed account of how sea ice affects the life cycle of emperor penguins, their reproduction, and their mortality. When we feed the results of the NCAR climate model into it, we can start to see how different global temperature targets may affect the emperor penguin population as a whole."

The researchers ran the model on three different scenarios: a future where global temperature increases by only 1.5 degrees Celsius (the goal set out by the Paris climate accord), one where temperatures increase by 2 degrees Celsius, and one where no action is taken to reduce climate change, causing to a temperature increase of 5 to 6 degrees Celsius.

Under the 1.5 degree scenario, the study found that only 5 percent of sea ice would be lost by 2100, causing a 19 percent drop in the number of penguin colonies. If the planet warms by 2 degrees, however, those numbers increase dramatically: the loss of sea ice nearly triples, and more than a third of existing colonies disappear. The 'business as usual' scenario is even more dire, Jenouvrier adds, with an almost complete loss of the colonies ensured.

"Under that scenario, the penguins will effectively be marching towards extinction over the next century," she says.

Source: Woods Hole Oceanographic Institution [November 07, 2019]

Antarctica likely to drive rapid sea-level rise under climate change

By: Thomas Schmitt Attorney on November 06, 2019 / comment : 0 Antarctic, Climate Change, Earth Science, Natural Heritage, Oceans

Scientists from The Australian National University (ANU) have shown that ice melt from Antarctica drives rapid and high sea-level rise, offering a forewarning of what to expect under human-driven climate change.

Melting ice on the coast of Adelie Land in East Antarctica [Credit: Pauline Askin/Reuters]

The researchers examined historical and new data from the ‘last interglacial’, which took place 125,000 to 118,000 years ago and saw sea levels rise up to 10 metres above current levels.

Interglacials are periods of warmer global temperatures that can last thousands of years.

The study, published in Nature Communications, shows that sea levels rose up to three metres per century, largely driven by ice loss in the Antarctic ice sheet.

Lead author, Professor Eelco Rohling, said that the last interglacial sea-rise was due to natural climate instabilities.

“These were smaller and slower than the human-caused climate disturbance of today,” he said.

“Our study shows clearly that Antarctica, long thought a sleeping giant when it comes to sea-level rises, is in fact the key player.

“And it appears that it can change by large amounts on timescales that are highly relevant to society and in ways that would have profound effects on human infrastructure.”

The study shows for the first time by how much ice loss in the last interglacial first took place in Antarctica, followed by Greenland.

Early Antarctic ice loss was caused by Southern Ocean warming at the onset of the interglacial. Next, the meltwater from Antarctica caused changes in global ocean circulation that resulted in northern polar warming and associated Greenland ice loss.

Co-lead author, Dr Fiona Hibbert, said that in today's greenhouse-gas-driven climate change, rapid atmospheric and oceanic warming happens in both polar regions at the same time.

“This drives simultaneous ice-loss in Antarctica and Greenland,” Dr Hibbert said.

“But, what’s vital to remember is that today’s climatic disturbance is greater and develops faster than that of the last interglacial.

“As a result, rates of sea-level rise may develop over the next several centuries that are even higher than those found for the interglacial we have studied.”

Source: Australian National University [November 06, 2019]

Revealing interior temperature of Antarctic ice sheet

By: Thomas Schmitt Attorney on November 05, 2019 / comment : 0 Antarctic, Climate Change, Earth Science, Environment, Natural Heritage

As ESA's SMOS satellite celebrates 10 years in orbit, yet another result has been added to its list of successes. This remarkable satellite mission has shown that it can be used to measure how the temperature of the Antarctic ice sheet changes with depth—and it's much warmer deep down.

ESA’s SMOS mission has been used to show how the temperature of the Antarctic ice sheet changes with depth. The image shows how the ice is colder (blue) at the surface but warmer (red) at the base. Temperature is one of the things that determines how ice flows and slides over the bedrock beneath. In turn, this flow affects the temperature profile through strain heating – so it’s a complicated process. Temperature information is also fundamental for understanding the presence of aquifers inside or at the bottom part of ice sheets. This can be relevant for indicating the presence of sub-glacial lakes, for example, which in turn influence ice-sheet dynamics [Credit: European Space Agency]

The Antarctic ice sheet is, on average, about two kilometers thick, but in some places the bedrock is almost five kilometers below the surface of this huge polar ice cap.

Most of us would probably think that the temperature of ice, no matter how thick, remains pretty much the same throughout: basically very cold

However, although the surface of the ice sheet is cold, the temperature increases with depth primarily because of the basal geothermal heating from beneath Earth's crust. In places, it is warm enough to melt the ice, which accounts for the presence of lakes and a vast hydrological network at the bedrock.

Nevertheless, there is little accurate information on exactly how temperature varies with depth other than from ice core borehole locations.

Since the massive white ice sheets that blanket Antarctica and Greenland reflect incident solar radiation back out into space, they are extremely important regulators in the climate system and, therefore, play a key role in the health of our planet.

But, ice sheets are also victims of climate change. For example, this year scientists discovered that warming ocean waters have caused the ice to thin so rapidly that a quarter of the glacier ice in West Antarctica is now unstable.

With melting ice sheets largely responsible for rising sea levels, which, in turn, threaten hundreds of millions of people around the world, it is vital that more is understood about how temperature influences ice-sheet dynamics.

Satellite data are used, in particular, to measure changes in the height of ice sheets and consequently their "mass balance," where the ice sheet ends and the floating ice shelves begin—their grounding lines, their surface temperature and how fast ice streams flow.

Temperature is one of the things that determines ice viscosity and therefore how ice sheets flow and slide over the bedrock beneath. In turn, this flow affects the ice-sheet temperature profile through strain heating – so it’s a complicated process. Information on temperature is also fundamental for understanding the presence of aquifers inside or at the bottom of ice sheets. This can be relevant for indicating the presence  of sub-glacial lakes, for example, which in turn influence ice-sheet dynamics. ESA’s SMOS satellite  mission has shown that it can be used to measure how the temperature of the Antarctic ice sheet changes with depth [Credit: IFAC]

However, temperature is one of the things that determines ice viscosity and how ice flows and slides over the bedrock beneath. In turn, ice flow affects the temperature profile through strain heating—so it's a complicated process.

Temperature information is also fundamental for understanding the presence of aquifers inside or at the bottom part of ice sheets. This can be relevant for indicating the presence of sub-glacial lakes, for example, which, in turn, influence ice-sheet dynamics.

How temperature varies according to the depth of the ice is not something that could be measured from space until now—but according to a paper published recently in Remote Sensing of Environment, SMOS is opening up new opportunities to do so.

Giovanni Macelloni from the Institute of Applied Physics Nello Carrara of the National Research Council (IFAC-CNR) in Italy, said, "We typically get ice-sheet temperature profiles from models, or from in situ measurements taken in boreholes—but these are obviously fairly sparse."

Information on temperature from space has, so far, been limited to the surface or just below the surface from thermal-infrared sensors and microwave sensors.

The researchers from IFAC-CNR and the Institute of Environmental Geosciences in France, therefore used ESA's SMOS satellite to see if there is a way of gaining this information rather than relying on models and boreholes.

"We combined SMOS' L-band passive microwave observations over Antarctica with glaciological and emission models to infer information on glaciological properties of the ice sheet at various depths, including temperature," continued Dr. Macelloni.

"With temperature playing such an important role in ice-sheet dynamics, we are happy to say that our research, when compared with models, shows a better estimation of temperature increase with depth, with the largest differences close to the bedrock.

"SMOS is clearly opening up more possibilities that we ever thought when it was launched 10 years ago."

Source: European Space Agency [November 05, 2019]

Two million-year-old ice provides snapshot of Earth's greenhouse gas history

By: Thomas Schmitt Attorney on October 30, 2019 / comment : 0 Antarctic, Climate Change, Earth Science, Palaeoclimate, Palaeontology

Two million-year old ice from Antarctica recently uncovered by a team of researchers provides a clearer picture into the connections between greenhouse gases and climate in ancient times and will help scientists understand future climate change.

Oregon State University Professor Ed Brook holding 2 million-year-old ice [Credit: Oregon State University]

In a paper published in Nature, a group of scientists used air trapped in the bubbles in ice as old as 2 million years to measure levels of the greenhouse gases carbon dioxide and methane. The group was led by John Higgins and Yuzhen Yan of Princeton University and Andrei Kurbatov of the University of Maine, and included Ed Brook at Oregon State University and Jeff Severinghaus at the University of California, San Diego.

This is the first time scientists were able to study an ice core that old. Previously, the oldest complete ice core provided data back to 800,000 years. Past studies using that core and others have shown that atmospheric carbon dioxide levels are directly linked to Antarctic and global temperature during the past 800,000 years. Prior to that, the connection between climate and carbon dioxide levels has not been as well understood. The paper published in Nature begins to change that.

During the past one million years the cycle of ice ages followed by warm periods occurred every 100,000 years. But between 2.8 million years ago and 1.2 million years ago, those cycles were shorter, about 40,000 years, and ice ages were less extreme.

The team that included Brook wanted to find out how carbon dioxide levels varied during that older time period, which until now was known only indirectly from the chemistry of sediments in the ocean and on land.

They found that the highest levels of carbon dioxide matched the levels in warm periods of more recent times. The lowest levels, however, did not reach the very low concentrations found in the ice ages of the last 800,000 years.


"One of the important results of this study is to show that carbon dioxide is linked to temperature in this earlier time period," Brook said.

This conclusion is based on studies of the chemistry of the ice, which provide an indication of temperature change in Antarctica at the same time as the carbon dioxide variations.

"That's an important baseline for understanding climate science and calibrating models that predict future change," Brook said.

The ice core with the 2 million-year-old ice comes from an area known as Allan Hills, which is about 130 miles from the U.S. Antarctic research station known as McMurdo Station. Ancient meteorites had been found on the surface in this area, leading scientists to believe there could be ancient ice in the ice sheet.

The core with the 2 million-year-old ice was drilled to a depth of 200 meters during the 2015-16 field season. It takes one to two weeks to drill and recover a core like that, and several cores were collected in the region.

The research team is on its way back to Allan Hills in the coming days for two months of additional work. They will be collecting larger quantities of the 2 million year old ice and searching for even older samples.

"We don't know the age limit in this area," Brook said "It could be much older in some places. That's why we're going back. Pushing beyond two million years would be pretty amazing".

Author: Sean Nealon | Source: Oregon State University [October 30, 2019]

300-year thinning may have predisposed Antarctic ice shelves to collapse

By: Thomas Schmitt Attorney on October 24, 2019 / comment : 0 Antarctic, Climate Change, Earth Science, Natural Heritage, Palaeoclimate

Ice shelves in the eastern Antarctic Peninsula may have been predisposed to collapse by hundreds years of thinning according to a study in Scientific Reports.

Credit: Bernhard Staehli/Shutterstock

To investigate past drivers of ice mass loss and its effect on the present, William Dickens and colleagues constructed a 6,250 year record of glacial meltwater discharge by analysing oxygen variants (isotopes) in single-celled algae preserved within a marine sediment core from the northeastern tip of the Antarctic Peninsula. Lower isotope values correspond to higher glacial discharge of fresh water.

The authors found that an increasing trend in glacial discharge occurred after the year 1400 reaching unprecedented levels after 1706. Another marked acceleration in glacial melting was observed after 1912. The findings suggest that ice shelves in this region have been thinning at an accelerating rate for approximately 300 years, which may predispose them to collapse as anthropogenic warming intensifies.

The authors suggest accelerated thinning was in part linked to shifts in the Southern Annular Mode that drove stronger westerly winds, atmospheric warming and ice shelf melting on the eastern Antarctic Peninsula, while also pulling warm water into the Weddell Gyre, potentially increasing melting on the undersides of ice shelves. Similar, more frequent shifts in the Southern Annular Mode observed more recently may reflect the dominant influence of greenhouse gas levels and ozone depletion and lead to accelerated ice mass loss in the future.

Source: Nature Publishing Group [October 24, 2019]

Ice core source discovery adds to study of volcanic activity, climate system interactions

By: Thomas Schmitt Attorney on October 10, 2019 / comment : 0 Antarctic, Climate Change, Earth Science, Geology, Palaeoclimate, Palaeontology

A new discovery by University of Maine researchers that challenges the established volcanic source of particles found in an ice core from the South Pole adds to the global record of volcanism and is relevant to several   research disciplines.

The Ice Drilling Design and Operations (IDDO) group at the University of Wisconsin-Madison designed and built the South Pole Ice Core (SPICE) drilling system, called the Intermediate Depth Drill. Based on a Danish drill called the Hans-Taunsen drill, the Intermediate Depth Drill was purpose-built for coring 1,500 meters of ice. The ice cores collected at this depth (from the South Pole) contain atmospheric gases from the past 40,000 years,  the time of transition from the last ice age to the present warm climate [Credit: T.J. Fudge]

Understanding how the Earth's volcanic activity interacts with the climate system, as well as volcanic hazard mitigation studies and reconstructions of how past volcanic events have affected human history often rely on detailed records of past volcanic eruptions. Unfortunately, in many parts of the world, historical records are sporadic, short and not well documented, according to Andrei Kurbatov, associate professor at the University of Maine School of Earth and Climate Sciences and Climate Change Institute.

In the last decade, Kurbatov and Martin Yates, electron beam laboratory manager and instructor of Earth sciences at UMaine, in collaboration with Nelia Dunbar and Nels Iverson from the New Mexico Institute of Mining and Technology, developed a method of extracting volcanic ash particles from ice core samples to measure their geochemical composition.

The new methodology provides additional means to refine the history of global volcanism captured in polar ice core records, according to Kurbatov.

Laura Hartman, a graduate student at the CCI, used the methodology while examining microscopic volcanic ash particles in ice core samples from Antarctica's South Pole. Hartman was advised by Kurbatov and Earth and Climate Sciences assistant professor Alicia Cruz-Uribe.

She found several particles from a volcanic interval that in the last three decades was attributed to a volcanic eruption from the Kuwae volcanic center in Vanuatu.

Hartman determined the geochemical signatures of the particles, that provide a unique volcanic source fingerprint, and compared the signatures with the known composition of Kuwae volcanic products.

She discovered the composition was similar to volcanic products from the South American volcano Reclus, not Kuwae.

"The discovery challenges the established volcanic source for one of the largest ice core sulfate signals from the last millennium," Kurbatov says. "The new source location will impact how climate models calculate atmospheric loading and ultimately will guide how climate models determine the impact of this volcanic event on the climate system."

The relatively young, unknown explosive volcanic eruption from Reclus volcano, located close to several national parks in South America, provides new important constraints for regional volcanic hazards assessments and air-traffic safety, Kurbatov says. The new data also question the existing paradigm on long-range transport of ultrafine volcanic particles in the atmosphere.

With funding from the National Science Foundation, Kurbatov and his team plan to continue to explore volcanic deposits in the South Pole ice core using the new methodology to further refine the global record of volcanism.

The study was published in Scientific Reports.

Source: University of Maine [October 10, 2019]

Study recommends special protection of emperor penguins

By: Thomas Schmitt Attorney on October 08, 2019 / comment : 0 Antarctic, Climate Change, Ecosystems, Endangered Species, Natural Heritage, Wildlife

In a new study published this week in the journal Biological Conservation, an international team of researchers recommends the need for additional measures to protect and conserve one of the most iconic Antarctic species - the emperor penguin (Aptenodyptes forsteri).

Emperor penguins need sea ice to breed [Credit: British Antarctic Survey]

The researchers reviewed over 150 studies on the species and its environment as well as its behaviour and character in relation to its breeding biology. Current climate change projections indicate that rising temperatures and changing wind patterns will impact negatively the sea ice on which emperor penguins breed; and some studies indicate that emperor populations will decrease by more than 50% over the current century.

The researchers therefore recommend that the IUCN status for the species be escalated to 'vulnerable'; the species is currently listed as 'near threatened' on the IUCN Red List. They conclude that improvements in climate change forecasting in relation to impacts on Antarctic wildlife would be beneficial, and recommend that the emperor penguin should be listed by the Antarctic Treaty as a Specially Protected Species.

Lead author Dr Philip Trathan, Head of Conservation Biology at British Antarctic Survey, says: "The current rate of warming in parts of the Antarctic is greater than anything in the recent glaciological record. Though emperor penguins have experienced periods of warming and cooling over their evolutionary history, the current rates of warming are unprecedented."

"Currently, we have no idea how the emperors will adjust to the loss of their primary breeding habitat - sea ice. They are not agile and climbing ashore across steep coastal land forms will be difficult. For breeding, they depend upon sea ice, and in a warming world there is a high probability that this will decrease. Without it, they will have little or no breeding habitat."

Greater protection measures will enable scientists to coordinate research into the penguins' resilience to a range of different threats and stressors.

Dr Peter Fretwell, remote sensing specialist at British Antarctic Survey and co-author says: "Some colonies of emperor penguins may not survive the coming decades, so we must work to give as much protection as we can to the species to give them the best chance."

The UK, supported by a number of other countries whose researchers have engaged in this scientific work, notified the Antarctic Treaty Consultative Meeting at its 2019 meeting, held in Prague in July, that Emperor Penguins were threatened through the loss of their breeding habitat and that further protections should be developed. A similar paper has also been submitted to this year's Commission for the Conservation of Antarctic Marine Living Resources, which meets in Hobart later this month, where the UK is also supporting a number of proposals to extend the coverage of Marine Protected Areas in the Southern Ocean.

Source: British Antarctic Survey [October 08, 2019]

Flowing Antarctic ice mapped 10 times more accurately

By: Thomas Schmitt Attorney on July 30, 2019 / comment : 0 Antarctic, Climate Change, Environment, Natural Heritage

Constructed from a quarter century's worth of satellite data, a new map of Antarctic ice velocity by glaciologists from the University of California, Irvine and NASA's Jet Propulsion Laboratory is the most precise ever created.

The new map's "more detailed representation will help improve our understanding of ice behavior under climate stress over a larger part of the continent, farther south, and will enable improved projections of sea level rise through numerical models," says Jeremie Mouginot, UCI associate researcher in Earth system science and the study's lead author [Credit: Jeremie Mouginot/UCI]

Published in a paper in the American Geophysical Union journal Geophysical Research Letters, the map is 10 times more accurate than previous renditions, covering more than 80 percent of the continent.

"By utilizing the full potential of interferometric phase signals from satellite synthetic-aperture radars, we have achieved a quantum leap in the description of ice flow in Antarctica," said lead author Jeremie Mouginot, UCI associate researcher in Earth system science. "This more detailed representation will help improve our understanding of ice behavior under climate stress over a larger part of the continent, farther south, and will enable improved projections of sea level rise through numerical models."

To chart the movement of ice sheets across the surface of the enormous land mass, the researchers combined input from six satellite missions: the Canadian Space Agency's Radarsat-1 and Radarsat-2; the European Space Agency's Earth remote sensing satellites 1 and 2 and Envisat ASAR; and the Japan Aerospace Exploration Agency's ALOS PALSAR-1.

While the data were spread across 25 years, the pace of signal gathering accelerated in the last decade as more resources were deployed in the Earth's orbit. As ice sheet science coordinator in the World Meteorological Organization's Polar Space Task Group, co-author Bernd Scheuchl, UCI associate project scientist in Earth system science, was responsible for acquiring the relevant data from the various international space agencies.

Previous mapping efforts relied heavily on "feature" and "speckle tracking" methods, which detect the subtle motion of parcels of ice on the ground over time; this approach has been proven effective in estimating ice flow speed. To measure significantly slower ice sheet movement in the vast interior regions, the UCI team augmented these techniques with synthetic-aperture radar phase interferometry, which detects the subtle motion of natural reflectors of radar signals in snow/ice independent of the size of the parcel of ice illuminated by the radar.

"The interferometric phase of SAR data measures the ice deformation signal with a precision of up to two orders of magnitude better than speckle tracking," Mouginot said. "A drawback is that it requires a lot more data, namely multiple passes at different angles over the same point on the ground—a problem that was solved by a consortium of international space agencies pointing Earth-monitoring spacecrafts to this part of the world."

The team was able to compose a map that resolves ice movement to a level of 20 centimeters (a little over half a foot) per year in speed and 5 degrees in annual flow direction for more than 70 percent of Antarctica. It's the first time that high-precision mapping of the interior areas has been accomplished.

"This product will help climate scientists achieve a number of goals, such as a better determination of the boundaries between glaciers and a thorough evaluation of regional atmospheric climate models over the entire continent," said co-author Eric Rignot, chair and Donald Bren Professor of Earth System Science at UCI and a JPL senior research scientist.

"It will also help in locating the most promising sites for ice core drilling to extract climate records and in examining the mass balance of Antarctica beyond its periphery."

He said he's looking forward to the joint NASA and Indian Space Research Organization satellite, launching in late 2021, which will be the first interferometric-mode SAR mission designed to look solely toward the South Pole. The spacecraft will provide a coast-to-coast view of Antarctica every 12 days.

"We'll be able to collect enough quality phase data over the Antarctic to generate updates to the map we just created in one or two months instead of one or two decades," Rignot said. "With this level of precision in the interior regions, we'll be able to reconstruct high-resolution spatial details in the bed topography beneath the ice through inversion techniques over far broader areas than in previous attempts—essential to improving ice sheet models and projections of sea level rise from Antarctica."

Source: University of California, Irvine [July 30, 2019]

A clearer picture of global ice sheet mass

By: Thomas Schmitt Attorney on July 09, 2019 / comment : 0 Antarctic, Climate Change, Earth Science, Environment, Natural Heritage, Oceans

Fluctuations in the masses of the world's largest ice sheets carry important consequences for future sea level rise, but understanding the complicated interplay of atmospheric conditions, snowfall input and melting processes has never been easy to measure due to the sheer size and remoteness inherent to glacial landscapes.

Credit: University of Colorado at Boulder

Much has changed for the better in the past decade, according to a new review paper co-authored by researchers at the University of Colorado Boulder, NASA, Utrecht University and Delft University of Technology and recently published in the Review of Geophysics.

The study outlines improvements in satellite imaging and remote sensing equipment that have allowed scientists to measure ice mass in greater detail than ever before.

"We've come a long way in the last 10 years from an observational perspective," said Jan Lenaerts, lead author of the research and an assistant professor in CU Boulder's Department of Atmospheric and Oceanic Sciences (ATOC). "Knowing what happens to ice sheets in terms of mass in, mass out allows us to better connect climate variations to ice mass and how much the mass has changed over time."

Ice sheets primarily gain mass from precipitation and lose it due to solid ice discharge and runoff of melt water. Precipitation and runoff, along with other surface processes, collectively determine the surface mass balance. The Antarctic Ice Sheet, the world's largest, is cold year-round with only marginal summer melting. A small increase or decrease in yearly snowfall, then, can make a considerable difference in surface mass because the addition or subtraction is compounded over a massive area.

"Snowfall is dominant over Antarctica and will stay that way for the next few decades," Lenaerts said. "And we've seen that as the atmosphere warms due to climate change, that leads to more snowfall, which somewhat mitigates the loss of ice sheet mass there. Greenland, by contrast, experiences abundant summer melt, which controls much of its present and future ice loss."


In years past, climate models would have been unable to render the subtleties of snowfall in such a remote area. Now, thanks to automated weather stations, airborne sensors and Earth-orbit satellites such as NASA's Gravity Recovery and Climate experiment (GRACE) mission, these models have been improved considerably. They produce realistic ice sheet surface mass balance, allow for greater spatial precision and account for regional variation as well as wind-driven snow redistribution--a degree of detail that would have been unheard of as recently as the early 2000s.

"If you don't have the input variable right, you start off on the wrong foot," Lenaerts said. "We've focused on snowfall because it heavily influences the ice sheet's fate. Airborne observations and satellites have been instrumental in giving a better view of all these processes."

Ground-based radar systems and ice core samples provide a useful historical archive, allowing scientists to go back in time and observe changes in the ice sheet over long periods of time. But while current technologies allow for greater spatial monitoring, they lack the ability to measure snow density, which is a crucial variable to translate these measurements into mass changes.

The biggest opportunity may lie in cosmic ray counters, which measure surface mass balance directly by measuring neutrons produced by cosmic ray collisions in Earth's atmosphere, which linger in water and can be read by a sensor. Over long periods of time, an array of these devices could theoretically provide even greater detail still.

Overall, Lenaerts said, the field of ice sheet observation has come of age in recent years, but still stands to benefit from additional resources.

"The community of researchers studying these issues is still relatively small, but it's already a global community and interest is growing," he said. "We'd like to get to a point where ice sheet mass processes are factored into global climate and Earth system models, to really show that bigger picture."

Author: Trent Knoss | Source: University of Colorado at Boulder [July 09, 2019]

Instability in Antarctic ice projected to make sea level rise rapidly

By: Thomas Schmitt Attorney on July 08, 2019 / comment : 0 Antarctic, Climate Change, Environment, Natural Heritage, Oceans

Images of vanishing Arctic ice and mountain glaciers are jarring, but their potential contributions to sea level rise are no match for Antarctica's, even if receding southern ice is less eye-catching. Now, a study says that instability hidden within Antarctic ice is likely to accelerate its flow into the ocean and push sea level up at a more rapid pace than previously expected.

Part of Thwaites Glacier crumbles into the ocean. It is part of the normal life of a glacier, but the rate of ice flow into the ocean of some Antarctic glaciers has markedly accelerated, raising concerns [Credit: NASA/OIB Jeremy Harbeck]

In the last six years, five closely observed Antarctic glaciers have doubled their rate of ice loss, according to the National Science Foundation. At least one, Thwaites Glacier, modeled for the new study, may be in danger of succumbing to this instability, a volatile process that pushes ice into the ocean fast.

How much ice the glacier will shed in coming 50 to 800 years can't exactly be projected due to unpredictable fluctuations in climate and the need for more data. But researchers at the Georgia Institute of Technology, NASA Jet Propulsion Laboratory, and the University of Washington have factored the instability into 500 ice flow simulations for Thwaites with refined calculations.

The scenarios diverged strongly from each other but together pointed to the eventual triggering of the instability, which will be described in the question and answer section below. Even if global warming were to later stop, the instability would keep pushing ice out to sea at an enormously accelerated rate over the coming centuries.

And this is if ice melt due to warming oceans does not get worse than it is today. The study went with present-day ice melt rates because the researchers were interested in the instability factor in itself.

Glacier tipping point

"If you trigger this instability, you don't need to continue to force the ice sheet by cranking up temperatures. It will keep going by itself, and that's the worry," said Alex Robel, who led the study and is an assistant professor in Georgia Tech's School of Earth and Atmospheric Sciences. "Climate variations will still be important after that tipping point because they will determine how fast the ice will move."

Thwaites Glacier's outer edge. As the glacier flows into the ocean, it becomes sea ice and drives up sea level. Thwaites Glacier ice is flowing particularly fast, and some researchers believe it may have already tipped  into instability or be near that point, though this has not yet been established [Credit: NASA/James Yungel]

"After reaching the tipping point, Thwaites Glacier could lose all of its ice in a period of 150 years. That would make for a sea level rise of about half a meter (1.64 feet)," said NASA JPL scientist Helene Seroussi, who collaborated on the study. For comparison, current sea level is 20 cm (nearly 8 inches) above pre-global warming levels and is blamed for increased coastal flooding.

The researchers published their study in the journal the Proceedings of the National Academy of Sciences. The research was funded by the National Science Foundation and NASA.

The study also showed that the instability makes forecasting more uncertain, leading to the broad spread of scenarios. This is particularly relevant to the challenge of engineering against flood dangers.

"You want to engineer critical infrastructure to be resistant against the upper bound of potential sea level scenarios a hundred years from now," Robel said. "It can mean building your water treatment plants and nuclear reactors for the absolute worst-case scenario, which could be two or three feet of sea level rise from Thwaites Glacier alone, so it's a huge difference."

Q&A

Why is Antarctic ice the big driver of sea level rise?

Arctic sea ice is already floating in water. Readers will likely remember that 90% of an iceberg's mass is underwater and that when its ice melts, the volume shrinks, resulting in no change in sea level.

Changes in the Antarctic ice sheet’s contribution to global sea level, 1992 to 2017 [Credit IMBIE (NASA/ESA)]

But when ice masses long supported by land, like mountain glaciers, melt, the water that ends up in the ocean adds to sea level. Antarctica holds the most land-supported ice, even if much of that land is seabed holding up just part of the ice's mass, while water holds up part of it. Also, Antarctica is an ice leviathan.

"There's almost eight times as much ice in the Antarctic ice sheet as there is in the Greenland ice sheet and 50 times as much as in all the mountain glaciers in the world," Robel said.

What is that 'instability' underneath the ice?

The line between where the ice sheet rests on the seafloor and where it extends over water is called the grounding line. In spots where the bedrock underneath the ice behind the grounding line slopes down, deepening as it moves inland, the instability can kick in.

On deeper beds, ice moves faster because water is giving it a little more lift. Also, warmer ocean water hollows out the bottom of the ice, adding a little more water to the ocean. More importantly, the ice above the hollow loses land contact and flows faster out to sea.

Ice melt at the grounding line contributes to seawater and thus sea levels, but the larger effect is to send more ice above it out into the water, where it also drives up sea level. When sea bottom behind the grounding line, under the ice, slopes downward going inland, it exacerbates the process, which can become unstable, perpetually pushing ice out to sea [Credit: antarcticglaciers.org]

"Once ice is past the grounding line and just over water, it's contributing to sea level because buoyancy is holding it up more than it was," Robel said. "Ice flows out into the floating ice shelf and melts or breaks off as icebergs."

"The process becomes self-perpetuating," Seroussi said, describing why it is called "instability."

How did the researchers integrate instability into sea level forecasting?

The researchers borrowed math from statistical physics that calculate what random variables do to predictability in a physical system, like ice flow, acted upon by outside forces, like temperature changes. They applied the math to simulations of possible future fates of marine glaciers like Thwaites Glacier.

They made an added surprising discovery. Normally, when climate conditions fluctuate strongly, Antarctic ice evens out the effects. Ice flow may increase but gradually, not wildly, but the instability produced the opposite effect in the simulations.

"The system didn't damp out the fluctuations, it actually amplified them. It increased the chances of rapid ice loss," Robel said.

Marine life recovery following the dinosaurs' extinction

By: Thomas Schmitt Attorney on June 19, 2019 / comment : 0 Antarctic, Dinosaurs, Fossils, Oceans, Palaeontology

A new study shows how marine life around Antarctica returned after the extinction event that wiped out the dinosaurs.

The team studied nearly 3000 fossils [Credit: Rowan Whittle]

A team led by British Antarctic Survey studied just under 3000 marine fossils collected from Antarctica to understand how life on the sea floor recovered after the Cretaceous-Paleogene (K-Pg) mass extinction 66 million years ago. They reveal it took one million years for the marine ecosystem to return to pre-extinction levels. The results are published in the journal Palaeontology.

The K-Pg extinction wiped out around 60% of the marine species around Antarctica, and 75% of species around the world. Victims of the extinction included the dinosaurs and the ammonites. It was caused by the impact of a 10 km asteroid on the Yucatan Peninsula, Mexico, and occurred during a time period when the Earth was experiencing environmental instability from a major volcanic episode. Rapid climate change, global darkness, and the collapse of food chains affected life all over the globe.

The K-Pg extinction fundamentally changed the evolutionary history of life on Earth. Most groups of animals that dominate modern ecosystems today, such as mammals, can trace the roots of their current success back to the aftermath of this extinction event.

A team of scientists from British Antarctic Survey, the University of New Mexico and the Geological Survey of Denmark & Greenland show that in Antarctica, for over 320,000 years after the extinction, only burrowing clams and snails dominated the Antarctic sea floor environment. It then took up to one million years for the number of species to recover to pre-extinction levels.

Author Dr Rowan Whittle, a palaeontologist at British Antarctic Survey says: "This study gives us further evidence of how rapid environmental change can affect the evolution of life. Our results show a clear link in the timing of animal recovery and the recovery of Earth systems."

Author Dr James Witts, a palaeontologist at University of New Mexico says: "Our discovery shows the effects of the K-Pg extinction were truly global, and that even Antarctic ecosystems, where animals were adapted to environmental changes at high latitudes like seasonal changes in light and food supply, were affected for hundreds of thousands of years after the extinction event."

Source: British Antarctic Survey [June 19, 2019]

Researchers find insights into the formation of the solar system in ancient comet dust

By: Thomas Schmitt Attorney on June 18, 2019 / comment : 0 Antarctic, Astronomy, Geology, Universe

Materials science researchers with the U.S. Naval Research Laboratory have found a remnant of ancient dust from the early stages of the solar system inside a primitive meteorite, named La Paz Icefield 02342 after the location of its discovery in Antarctica.

U.S. Naval Research Laboratory researchers Rhonda Stroud and Bradley De Gregorio found evidence of an ancient comet building block, using an advanced scanning transmission electron microscope, inside a meteorite collected in Antarctica. The finding provides insight into the formation of the solar system [Credit: US Naval Research Laboratory]

NRL scientists Rhonda Stroud and Bradley De Gregorio contributed to a paper describing the find, which is published in Nature Astronomy.

To examine these tiny grains within the larger particle, the researchers relied on a unique capability of NRL's Nanoscience Institute, which has a state-of-the-art aberration-corrected scanning transmission electron microscope that can shape its emitted electron beam to optimize image quality and resolution.

The microscope is one of only a few of its kind in the world. Along with other state-of-the art measurement and nanofabrication equipment located in the Institute, it enables NRL scientists and engineers to discover and develop new nanotechnology for the Navy and the Marine Corps.

"Having this capability at the lab is ideal," De Gregorio said. "It helps us stay on the cutting edge of science, and contributes to amazing studies like this one."

De Gregorio, a researcher with NRL's Materials Science and Technology Division, called the confluence of cosmic events that led to the finding "amazing," and "an incredible journey" for an ancient dust particle.

"This particle formed at the beginning of our solar system," he said. "[It] had to travel from the outer comet-forming regions, become embedded in asteroids forming in the interior of our system. [Then an asteroid had to] break apart in just the right way to form a meteoroid with the dust particle in it. Then the meteorite had to land on Antarctica in just the right spot to be collected by a field scientist."

The researchers validated the dust's cometary heritage from its pre-solar grains, tiny particles of primarily carbon, which have a specific isotopic chemical signature not found in material originating within our solar system, and from the presence of glassy grains containing nanoscale iron metal and sulfides, which are commonly found in other studies of comet dust.

The meteorite was collected in Antarctica during the 2002 field season of NASA's Antarctic Search for Meteorites (ANSMET) program. This work was funded by NASA's Science Mission Directorate, through grants NNX10AI63G and NNH16AC42I, and by Spanish Ministry of Science grants AYA 2011-26522 and AYA 2015-67175-P.

Source: U.S. Naval Research Lab [June 18, 2019]

The complex fate of Antarctic species in the face of a changing climate

By: Thomas Schmitt Attorney on June 17, 2019 / comment : 0 Antarctic, Climate Change, Ecosystems, Natural Heritage, Wildlife

Oxygen concentrations in both the open ocean and coastal waters have declined by 2-5% since at least the middle of the 20th century.

The four crustacean amphipod species which were the subject of the study - Paraceradocus miersi, Shraderia gracilis, Probulisca ovata and Prostebbingia brevicornis [Credit: John Spicer]

This is one of the most important changes occurring in an ocean becoming increasingly modified by human activities, with raised water temperatures, carbon dioxide content and nutrient inputs.

Through this, humans are altering the abundances and distributions of marine species but the decline in oxygen could pose a new set of threats to marine life.

Writing in Philosophical Transactions of the Royal Society B, scientists present support for the theory that marine invertebrates with larger body size are generally more sensitive to reductions in oxygen than smaller animals, and so will be more sensitive to future global climate change.

It is widely believed that the occurrence of gigantic species in polar waters is made possible by the fact that there is more oxygen dissolved in ice cold water than in the warmer waters of temperate and tropic regions.

So as our ocean warms and oxygen decreases, it has been suggested that such oxygen limitation will have a greater effect on larger than smaller marine invertebrates and fish.

The study was conducted by John Spicer, Professor of Marine Zoology at the University of Plymouth, and Dr Simon Morley, an Ecophysiologist with the British Antarctic Survey (BAS).

They investigated how a number of different sized amphipod species - found in abundance in Antarctic waters and relatives of the sandhoppers on temperate beaches) - performed when the oxygen in the water they were in was reduced.

John Spicer collecting intertidal amphipods from South Cove (Rothera Research Station, British Antarctic Survey) looking west to Ryder Bay on the Western Antarctic Peninsula [Credit: Simon Morley]

Overall, there was a reduction in performance with body size supporting the theory that larger species may well be more vulnerable because of oxygen limitation.

However, the picture is a little more complex than this with evolutionary innovation - such as the presence of oxygen binding pigments in their body fluids to enhance oxygen transport, and novel gas exchange structures in some, but not all, species - to some extent offsetting any respiratory disadvantages of large body size.

Professor Spicer, who has spent more than 30 years examining the effect of climate change on marine organisms, said: "Over the last 50 years, the oxygen in our oceans has decreased by around 2-5% and this is already having an effect on species' ability to function. Unless they adapt, many larger marine invertebrates will either shrink in size of face extinction, which would have a profoundly negative impact on the ecosystems of which they are a part. This is obviously a major cause for concern.

"Our research also shows that some species have evolved mechanisms to compensate for reductions in oxygen, and so it is not always as simple as drawing a link between size and future survival. But it would be foolhardy to pin our hopes on such 'evolutionary rescue'. Many large species will almost certainly be the first casualties of our warming, oxygen-poor ocean."

Dr Morley added: "Marine animals thrive in the Southern Ocean but life in these freezing waters has led to the evolution of many distinct characteristics. These 'strategies', which allow animals to survive in the cold, are expected to make many Antarctic marine invertebrates and fish vulnerable to the impact of climate change. Understanding these impacts will not only help us to predict the fate of marine biodiversity at the poles but will also teach us much about the mechanisms that will determine the survival of species across the world's oceans."

Author: Alan Williams | Source: University of Plymouth [June 17, 2019]

Paleontologists discover giant reptile in Antarctica

By: Thomas Schmitt Attorney on June 04, 2019 / comment : 0 Antarctic, Fossils, Palaeontology

It is the largest elasmosaurid in the world, similar in appearance to the Loch Ness monster. With a body mass that exceeded 12 tons, it doubles in size the majority of reptiles of his family known until now. According to the researchers, they would have developed a form of feeding similar to that of whales.

Credit: Agencia CTyS-UNLaM

The paleontologist José O'Gorman of the Museum of La Plata (MLP) and CONICET assured the CTyS-UNLaM Agency that "a very important specimen was extracted in the Marambio Island; It is the largest elasmosaurid in the world. "

"Due to the large size of this specimen, its rescue was carried out during successive campaigns of the Argentine Antarctic Institute and its rescue culminated in 2017", explained the main author of this study published recently in the scientific journal Cretaceous Research.

In addition, this giant reptile stands out for being the elasmosaurid closest to the extinction of dinosaurs that has been discovered on the white continent. Dr. Marcelo Reguero, researcher of the Argentine Antarctic Institute and the MLP, said that "this fossil is very close to the end of the Cretaceous, when it is estimated that a large meteorite fell and caused the disappearance of many species."

The remains of this giant reptile are in the Museum of La Plata. Part of his spine has been found, part of his anterior and posterior fins and some elements of the scapular waist. While his skull has not been found, researchers have analyzed what feeding strategy he might have had to develop such a large size.

It is estimated that the length of this reptile was between 11.2 and 12 meters. "It weighed between 10 and 13 tons, so it is well above those that were known until now, which had a mass of between five and six tons," said Dr. O'Gorman.

The elasmosaurids are part of the great family of plesiosaurs, those extinct reptiles in what possibly inspired the collective imagination to create the monster of Loch Ness.

Credit: Agencia CTyS-UNLaM

Within the elasmosaurids, this giant reptile is part of the subfamily of aristonectinos, which had a slightly shorter neck, much more robust vertebrae and a much larger skull.

"The hypothesis that could explain the great size of this new specimen, and that seems to be progressively supported by the evidence, is that the aristonectinos had a way of capturing their prey different from the rest of the elasmosaurids; We believe that, instead of capturing their prey individually, these animals opened their mouth and captured a large number of small prey at the same time, such as small crustaceans, for example, "O'Gorman said.

This type of capture is similar to the one applied by the current whales. Dr. O'Gorman said that "the whales take advantage of a roughness they have on the palate to catch the microplankton, while we consider that the aristonectinos used the battery of teeth as a kind of trap".

"It seems that evolution repeated certain patterns of development between these two groups that have no relationship," O'Gorman analyzed. And he differentiated: "Plesiosaurs are reptiles and have nothing to do with cetaceans that are mammals."

Dr. Marcelo Reguero highlighted the logistics and work that made possible the rescue of this specimen as well as other fossils in Antarctica.

In this site located towards the center of the Marambio Island, sediments of an ancient shallow marine environment are found. "There we have also found very small vertebrae of baby plesiosaurs; at that moment, there was a fairly calm sea" Reguero said. to the Agency CTyS-UNLaM.


In these deposits, flying seabirds and dinosaurs of different groups have also been found. Reguero appreciated that "whenever international congresses are held where the results of the research in Antarctica are exposed, the studies in paleontology of vertebrates carried out by the Argentine scientists are in very well positioned".

This new giant reptile specimen was discovered in 1989 and was recently completed in 2017. "The collection was carried out over many years and many teams have participated; this evidences the need for a support of the scientific activity that the Argentine Antarctic Institute has maintained over time, "said Dr. O'Gorman.

In addition to José O'Gorman and Marcelo Reguero, the researcher of the Argentine Antarctic Institute Sergio Santillana and the paleontologist Rodrigo Otero of the Laboratory of Ontogenia and Phylogeny of the University of Chile participated in this study that unveiled the world's largest elasmosaurid known so far.

Source: CTyS-UNLaM Agency [June 04, 2019]