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A key Antarctic glacier just lost a huge piece of ice — the latest sign of its worrying retreat.
Pine Island glacier is capable of driving 1.7 feet of sea level rise.
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A key Antarctic glacier just lost a huge piece of ice — the latest sign of its worrying retreat
By Chris Mooney September 25 at 11:12 AM Follow chriscmooney
The Pine Island Glacier calves 100 square miles of ice. (Stef Lhermitte)
This story has been updated.
An enormous Antarctic glacier has given up an iceberg over 100 square miles in size, the second time in two years it has lost such a large piece in a process that has scientists wondering whether its behavior is changing for the worse.
The Pine Island Glacier is one of the largest in West Antarctica, a region that is currently Antarctica’s biggest ice loser. Pine Island, which loses an extraordinary 45 billion tons of ice to the ocean each year (– equivalent to 1 millimeter of global sea level rise every eight years — is 25 miles wide where its floating front touches the sea, and rests on the seafloor in waters more than a half-mile deep. The single glacier alone contains 1.7 feet of potential global sea level rise and is thought to be in a process of unstable, ongoing retreat.
[Scientists just showed what it truly means when a huge Antarctic glacier is unstable]
That’s why scientists are watching it closely, and on Saturday, Stef Lhermitte, a satellite observation specialist at Delft University of Technology in the Netherlands, posted a satellite image showing that Pine Island had “calved,” or broken off a piece of ice about 103 square miles in area. (For comparison, Manhattan is 22.83 square miles in size.) The rectangular piece of ice then appears to have lost some of its shape immediately as smaller pieces splintered off.
“It’s the fifth large calving event since 2000,” Lhermitte said. “This one and 2015, they were much further inland than the previous ones. So there has been a retreat of the calving front, specifically between 2011 and 2015.”
It is the 5th large calving event since 2000, and today’s event is similar to 2015 when a 580km2 iceberg calved https://t.co/QXEzyX0X3q 3/n
— Stef Lhermitte (@StefLhermitte) September 23, 2017
The Washington Post confirmed the break with researchers at NASA and with another team of scientists studying Pine Island, Seongsu Jeong and Ian Howat of Ohio State University. They published a paper last year finding that Pine Island Glacier has developed a troubling new way of losing ice, with rifts forming in the center of its floating ice shelf from beneath, rather than at the sides, the traditional manner. They suspect this is a function of warmer ocean waters reaching the base of the glacier and weakening it.
“We predicted that the rifting would result in more frequent calving, which is what’s happening here,” Howat said by email. “If new rifts continue to form progressively inland, the significance to ice shelf retreat would be high.”
Last fall, NASA’s Operation IceBridge mission snapped a photo of the rift in Pine Island Glacier that would lead to the latest calving event.
Large rift near the Pine Island Glacier tongue, West Antarctica, as seen during an IceBridge flight on Nov. 4, 2016. (NASA/Nathan Kurtz)
And the drama may not be over. According to Ohio State glaciologist Ian Howat, the current break could precipitate additional, smaller breaks soon.
“A series of thin cracks was visible in the center of the ice shelf about 3 km inland of the current break in March 2017,” he said by email. “We don’t have any more recent data to see what its status is. But this means that we would expect another calving event very soon.” Something similar happened following the 2015 break — it was followed by another smaller event that Howat at the time likened to an “aftershock.”
The current ice loss event is nowhere near the size of the much-publicized loss of an enormous ice island from the Larsen C ice shelf earlier this year. However, in terms of sea level rise, changes at the Pine Island Glacier are far more consequential.
The current break was in the glacier’s floating ice shelf, which extends out over a deep ocean cavity. Further inland, the floating portion of the glacier ends and the ice slopes down and touches the seafloor at a vulnerable point called the “grounding line.” Changes in the temperature of waters reaching the grounding line in recent decades are widely believed to be the reason that Pine Island Glacier has been thinning and losing so much ice.
The glacier is feared to be in a process of unstable, runaway retreat. The grounding line has been moving inland, and as it retreats, the seafloor bed dips downward, meaning that the ocean becomes even deeper and the ice becomes even thicker. Thus, further retreat should increase the rate of outward flow and lead to even more ice loss.
The current loss is actually relatively small compared with prior events at Pine Island — a 2013 break released an iceberg 252 square miles in area, for instance, and the 2015 break was 225 square miles in size.
Moreover, the simple fact that large glaciers occasionally break off pieces in calving events is not news. It’s normal behavior, said Knut Christianson, a glaciologist at the University of Washington in Seattle who studies Pine Island.
“However, the mode of calving of Pine Island Glacier appears to be shifting,” Christianson said by email. That the latest rift originated in the center of the ice shelf, rather than at one of its sides, suggests that it developed far inland at the grounding line as a result of the warm ocean hitting the base of the glacier, he said.
“This results in smaller but more-frequent calving events,” he continued. “The persistence and net effect of this shift in calving behavior has yet to be determined as it has only occurred during the past two years, but it clearly merits continued observation.”
The overall result of recent changes, according to Lhermitte, is that the floating ice shelf of Pine Island Glacier has retracted inward considerably — although the 2015 and 2017 breaks did occur at around the same location.
Lhermitte created this animation to show the retreat:
Compared with the state of affairs in 2013, “the Pine Island Glacier (PIG) front position has now retreated about 20 km further into Pine Island Bay, especially at its eastern side,” said Christopher Shuman, a researcher at the Joint Center for Earth Systems Technology, a NASA and University of Maryland Baltimore County center.
“The PIG front is now substantially farther inland since it began retreating from a much more seaward position,” said Shuman by email. In other words, steady retreat of the glacier has visibly changed the Antarctic coastline.
Further retraction would only increase alarm about the state of the glacier, because floating ice shelves play a key stabilizing role, holding back the outward flow of ice. Pine Island’s ice is already flowing outward at a quite rapid 2.5 miles per year.
The immediate loss of ice from the shelf doesn’t raise sea level because that ice was already afloat — but any further increase of Pine Island’s overall flow would indeed have that effect.
“We are very worried about what might happen to Pine Island glacier in relation to sea level rise,” Lhermitte said.
Read more at Energy & Environment:
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Mammoth Antarctic iceberg is on the move, while the ice shelf it left behind grieves its loss.
The Delaware-sized iceberg that calved off the Larsen C Ice Shelf in Antarctica sometime between July 10 and July 12 is drifting farther from its former home, while breaking into smaller pieces.
The Delaware-sized iceberg that calved off the Larsen C Ice Shelf in Antarctica sometime between July 10 and July 12 is drifting farther from its former home, while breaking into smaller pieces.
More importantly, new cracks are appearing in the ice shelf that could portend the creation of additional icebergs and the possible destabilization of larger parts of the ice sheet, which holds back land-based ice from flowing into the sea and raising sea levels.
Satellite imagery from the Landsat 8 satellite as well as the the camera aboard the European Space Agency's (ESA) Sentinel-1 satellite are helping scientists keep tabs on the gargantuan iceberg despite the shroud of darkness during the Antarctic winter season.
Images released by NASA and the ESA show the iceberg's evolution and the beginnings of how the ice shelf is responding to losing such a large piece of itself.
According to NASA, the main iceberg, known as A-68A, continues to move northward, away from the Larsen C Ice Shelf. Meanwhile, it has already lost several small chunks.
Recent satellite photos also show three small icebergs forming to the north of where the main iceberg had been attached to the ice shelf.
If it seems like we're paying unusually close attention to this one particular iceberg, despite the multitude of other icebergs and glaciers that exist worldwide, well, it's because we are. To some extent, we're keeping a close eye on the iceberg because we can. Technology, in the form of advanced satellites, is enabling us to do this in ways that were never before possible.
But there's another reason why scientists have their sights set on the Larsen C Ice Shelf. The ice shelf is located in the Antarctic Peninsula, which is one of the most rapidly warming areas of the globe, and two of its neighbors, Larsen A and Larsen B, have already collapsed due in part to human-caused climate change.
Because of that, there is tremendous scientific interest in seeing how Larsen C responds to losing about 12 percent of its area in a single, trillion-ton iceberg. While the iceberg calving event itself is not likely caused specifically by climate change, it nevertheless threatens to speed up the already quickening pace of ice melt in the region due in large part to global warming.
Scientists have watched since 2014 as a fissure in the ice carved out a slice of the Larsen C Ice Shelf as if someone were taking a giant X-Acto Knife to the ice. That fissure finally set free the approximately 2,400-square-mile iceberg, which has since shrunk slightly in area as pieces have broken off.
Researchers affiliated with a U.K.-based initiative, known as Project MIDAS, report that a new rift appears to be developing in the ice shelf that could extend to a higher elevation point, known as the Bawden Ice Rise.
That area is considered to be "a crucial point" for stabilizing the ice shelf, and if it were to be weakened in some way it could speed the breakup of the shelf.
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Despite summer snow, Greenland is still melting.
Make no mistake, Greenland is still melting, dumping water into the ocean and causing global sea levels to steadily rise.
Recent summers on the vast, white expanse of the Greenland ice sheet have featured some spectacular ice melt, including an alarming period in 2012 when nearly the whole surface showed signs of melt. But this summer has instead seen several bouts of snow, staving off a big summer melt. So what gives?
While it may seem contradictory, those snows are actually something Greenland may see more of with global warming, as the atmosphere becomes primed to dump more heavy precipitation. And while that snow may insulate the ice sheet against major melt this year, focusing on one summer risks missing the forest for the trees. Because make no mistake, Greenland is still melting, dumping water into the ocean and causing global sea levels to steadily rise.
“We’re still pumping a lot of ice” out to sea, Marco Tedesco, who studies Greenland at Columbia University’s Lamont-Doherty Earth Observatory, said.
As Arctic temperatures rise at about double the rate of the planet as a whole, Greenland’s surface has been melting at a steady clip, contributing about 30 percent of the foot of global sea level rise since 1900. And summer is prime melt season, when the sun’s rays beat down on the ice, causing meltwater to pool on the surface and drain down through the ice sheet and out to sea.
Those rising seas will slowly inundate coastal cities; many already see more so-called sunny day flooding, impeding traffic and flooding basements. The surging waters pushed ashore by hurricanes and other storms is also getting higher and causing more costly damage.
Several recent summers have seen particularly stark ice loss: At the peak of the 2012 melt season, about 97 percent of the ice sheet surface was melting — that melt season alone contributed 1 millimeter of global sea level rise. Last year, the melt season started two months early thanks to high temperatures across parts of the island.
But this year has been noticeably different. It all started in October, when big snowstorms “really loaded Greenland up,” Jason Box, a glaciologist at the Geological Survey of Denmark and Greenland, said. “That really preconditioned this year for low melt because it thermally insulates the darker ice below.”
Essentially, it takes a lot more solar energy to get rid of that layer of bright, white snow, which reflects more solar rays back to space than darker layers of ice or meltwater.
While there were some bouts of melting earlier in the summer, the weather has since shifted. In recent weeks, summer snows have topped up that already unusually high snow load. Right now, the ice sheet’s surface has about 1.2 times the amount of mass than normal; at the same point in 2012, it had 1.2 times less than normal, Box said.
Also inhibiting summer melt this year is the unusually southerly position of the jet stream, caused by a climate pattern called the North Atlantic Oscillation. “That’s keeping Greenland relatively cold,” Box said.
While snowy weather may seem at odds with a warming world, Greenland could actually see more of it as temperatures rise. A warmer atmosphere can hold more moisture, which means that when storms pass through, they drop more precipitation. When temperatures are below freezing, as they are for much of Greenland through most of the year, that means more snowfall. (Rain has been falling at the expense of snow in the lower third of the island as temperatures rise above freezing, though.)
Previous research by Box using ice cores — long cylinders drilled out of the ice sheet that let scientists sample hundreds of years of ice layers — showed that in the past, snowfall has increased over the ice sheet as temperatures have risen.
For the first decade or so of this century, there were more clear skies over Greenland, and so increased melt. But atmospheric patterns seem to have flipped around in recent years, and Tedesco and others are still working on figuring out how changing atmospheric patterns might be influencing snowfall and melt on the ice sheet to better predict how it will progress with future warming.
This year’s excess snowfall doesn’t mean that melt isn’t still happening, though. Melt has already picked back up since the last summer snow earlier this month, Box said. In fact, he expects that that snow will now be a layer of slush he’ll have to trudge through when he arrives on the ice sheet this week to check on a network of weather stations.
The snow could, however, balance out the year’s melt, Box said, with the ice sheet ending up with no net loss of ice for the year — the first year that will have happened in two decades.
One year without a net loss also doesn’t buck the long-term trend of Greenland losing ice, both from surface melt and from ocean waters eating away at glaciers that flow out to sea.
The increase in snowfall “is about four or five times smaller than the increase in surface melting,” Box said. So “the Greenland ice sheet is losing mass overall.”
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Solve Antarctica’s sea-ice puzzle.
We need to know whether crucial interactions and feedbacks between the atmosphere, ocean and sea ice are missing from global climate models, and to what extent human influences are implicated.
John Turner and Josefino Comiso call for a coordinated push to crack the baffling rise and fall of sea ice around Antarctica.
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Antarctica's disappearing sea ice, from its peak in August 2016 to a record low on March 3, 2017.
Different stories are unfolding at the two poles of our planet. In the Arctic, more than half of the summer sea ice has disappeared since the late 1970s1. The steady decline is what global climate models predict for a warming world2. Meanwhile, in Antarctic waters, sea-ice cover has been stable, and even increasing, for decades3. Record maxima were recorded in 2012, 2013 and 2014 (ref. 4).
So it came as a surprise to scientists when on 1 March 2017, Antarctic sea-ice cover shrank to a historic low. Its extent was the smallest observed since satellite monitoring began in 1978 (see ‘Poles apart’) — at about 2 million square kilometres, or 27% below the mean annual minimum.
Researchers are struggling to understand these stark differences5. Why do Antarctica’s marked regional and seasonal patterns of sea-ice change differ from the more uniform decline seen around most of the Arctic? Why has Antarctica managed to keep its sea ice until now? Is the 2017 Antarctic decline a brief anomaly or the start of a longer-term shift6, 7? Is sea-ice cover more variable than we thought? Pressingly, why do even the most highly-rated climate models have Antarctic sea ice decreasing rather than increasing in recent decades? We need to know whether crucial interactions and feedbacks between the atmosphere, ocean and sea ice are missing from the models, and to what extent human influences are implicated6.
What happens in the Antarctic affects the whole planet. The Southern Ocean has a key role in global ocean circulation; a frozen sea surface alters the exchange of heat and gases, including carbon dioxide, between ocean and atmosphere. Sea ice reflects sunlight and influences weather systems, the formation of clouds and precipitation patterns. These in turn affect the mass of the Antarctic ice sheet and its contribution to sea-level rise. Sea ice is also crucial to marine ecosystems. A wide range of organisms, including krill, penguins, seals and whales, depend on its seasonal advance and retreat.
Mario Tama/Getty
Sea ice off the coast of West Antarctica starts to melt, as seen from NASA's Operation IceBridge aircraft in October 2016.
It is therefore imperative that researchers understand the fate of Antarctic sea ice, especially in places where its area and thickness are changing, and why. This requires bringing together understandings of the drivers behind the movement of the ice (through drift and deformation) as well as those that control its growth and melt (thermodynamics). Such knowledge underpins climate models; these need to better represent the complex interactions between sea ice and the atmosphere, ocean and ice sheet. What’s required now is a focused and coordinated international effort across the scientific disciplines that observe and model global climate and the polar regions.
Limited records
Satellites provide the best spatial information on sea ice around Antarctica. Regular observations reveal how ice cover varies over days, years and decades8. Weather, especially storms with high winds, has a daily influence, as well as a seasonal one. Longer-term changes are driven by larger patterns in the temperature and circulation of the atmosphere and oceans.
But near-continuous satellite observations only reach back about four decades. Longer records are essential to link sea-ice changes to trends in climate. Information from ships’ logbooks, coastal stations, whale-catch records, early satellite imagery and chemical analyses of ice cores hint that sea-ice coverage might have been up to 25% greater in the 1940s to 1960s6.
Source: US National Snow and Ice Data Center
Collecting more ice cores and historical records, and synthesizing the information they contain, could reveal local trends. These would help to identify which climatic factors drive Antarctic sea-ice changes6. For instance, in 2017, the area most depleted of sea ice was south of the Eastern Pacific Ocean. This region has strong links to the climate of the tropics, including the El Niño–Southern Oscillation, suggesting that sea ice is sensitive to conditions far from the poles.
Another issue is how the balance between dynamics and thermodynamics drives the advance and retreat of ice. The thickness and volume of ice depend on many factors, including the flow of heat from the ocean to the atmosphere and to the ice. Sea ice influences the saltiness of the ocean. As the ocean freezes, salt enters the water; as the ice melts, fresh water returns to the sea. Such processes are difficult to measure precisely, having uncertainties to within 50–100% of the signal. And they are hard to model.
“Sea-ice coverage might have been up to 25% greater in the 1940s to 1960s.”
Satellite altimeters can measure the distance between the surfaces of the sea ice and ocean accurately, and this distance can be used to calculate the ice thickness. But it is hard to interpret these data without knowing how much snow is on the ice, its density and whether the snow’s weight pushes the ice surface below sea level (as is often the case). Calibrating and validating satellite data are crucial, as is developing algorithms to merge and analyse information from a variety of sources.
Ice, ocean and air must be sampled at appropriate intervals over a wide enough area to establish how they interact. Research ice-breaker cruises are essential for collecting in situ observations; one such was the US PIPERS (Polynyas, Ice Production and seasonal Evolution in the Ross Sea) campaign in 2017. But ships travel only along narrow routes and for a short time, typically 1–3 months.
Increasingly, autonomous instruments and vehicles — underwater, on-ice and airborne — are providing data throughout the year and from inaccessible or dangerous regions. These robotic systems are giving revolutionary new information and insights into the formation, evolution, thickness and melting of sea ice. Sensors mounted on marine mammals (such as elephant seals), or on floats and gliders, also beam back data on temperature, salinity and other physical and biogeochemical parameters. But to operate continuously, these instruments need to be robust enough to withstand the harsh Antarctic marine environment.
Improve models
Current climate models struggle to simulate the seasonal and regional variability seen in Antarctic sea ice. Most models have biases, even in basic features such as the size and spatial patterns of the annual cycle of Antarctic sea-ice growth and retreat, or the amount of heat input to the ice from the ocean. The models fail to simulate even gross changes2, such as those driven by tropical influences on regional winds9. Because ice and climate are closely coupled, even small errors multiply quickly.
Paul Nicklen/NGC
Leopard seals live, hunt and breed among the pack ice in Antarctic waters.
Features that need to be modelled more accurately include the belt of strong westerly winds that rings Antarctica, and the Amundsen Sea Low — a stormy area southwest of the Antarctic Peninsula. Models disagree, for example, on whether persistent westerly winds should increase or decrease sea-ice coverage around Antarctica. Simulations of clouds and precipitation are also inadequate. These cannot currently reproduce the correct amounts of snowfall or sea surface temperature of the Southern Ocean (the latter is widely overestimated by the models).
Climate models must also include the mixing of waters by surface winds and the impact of waves on the formation and break-up of sea ice. Precipitation and meltwater from ice sheets and icebergs influence the vertical structure of the ocean and how it holds heat, which also affects the growth and decay of sea ice. Researchers need to develop models of the atmosphere–ocean–sea-ice environment at high spatial resolution.
Connect research
Explaining the recent variability in Antarctic sea ice, and improving projections of its future in a changing climate, requires projects that bridge many disciplines. For example, the research communities involved in ice-core analysis, historical data rescue and climate modelling need to collaborate to track sea-ice variability over timescales longer than the satellite record.
“Because ice and climate are closely coupled, even small errors multiply quickly.”
Some gaps in our knowledge can be filled through nationally funded research. More demanding cross-disciplinary work must be supported through international collaboration. Leading the way are organizations such as the Scientific Committee on Antarctic Research, the Scientific Committee on Oceanic Research, the World Climate Research Programme’s Climate and Cryosphere project and the Past Global Changes project. But essential work remains to be done, including: more detailed model comparisons and assessments; more research cruises; and the continuity and enhancement of satellite observing programmes relevant to sea ice. These organizations should partner with funding agencies to make that happen.
Better representations of the Southern Ocean and its sea ice must now be a priority for modelling centres, which have been focused on simulating the loss of Arctic sea ice. Such models will be crucial to the next assessment of the Intergovernmental Panel on Climate Change, which is due around 2020–21. A good example of the collaborative projects needed is the Great Antarctic Climate Hack (see go.nature.com/2ttpzcd). This brings together diverse communities with an interest in Antarctic climate to assess the performance of models.
Nature 547, 275–277 (20 July 2017) doi:10.1038/547275a
A list of co-signatories can be found in the Supplementary Information.
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'Catastrophic collapse' of West Antarctic ice sheet could raise global sea levels by three metres, warns scientist.
The break-up of the Ross Ice Shelf, which is about the size of France, could have serious consequences for the planet.
Climate change and the hole in the ozone layer could cause “a catastrophic collapse” of the vast amount of ice on West Antarctica, raising sea levels by 3.3 metres, a leading scientists has warned.
Following the calving of one of the largest icebergs ever known – about a quarter the size of Wales and weighing a trillion tonnes – Professor Nancy Bertler, of the Antarctic Research Centre at Victoria University of Wellington, said global warming and the hole in the ozone layer had caused the sudden break-up of “numerous ice shelves” in the region “some of which have been shown to have existed for 10,000 years or more”.
While these do not add to sea levels, their removal can significantly increase the speed of land ice flowing into the sea.
And that process, Professor Bertler warned, could have serious effects on the planet.
Sea level rise of more than three metres would dramatically alter the coastline of many parts of the world, according to an interactive map developed by Alex Tingle which enables people to see the effects of up to a 60-metre increase.
Large swathes of the Netherlands would disappear and significant chunks of the east coast of the UK would also be affected, particularly around the Wash, with Peterborough and Cambridge finding themselves near to the sea.
Professor Bertler said in a statement: “The Antarctic Peninsula is one of the fastest warming regions on Earth. Part of this warming comes from direct temperature increases in the atmosphere due to higher greenhouse gas concentrations and partly this is an indirect effect of ozone-destroying CFCs [chemicals].”
She said the changes had caused warmer and drier westerly winds to shift south towards Antarctica, increasing the temperature.
“This has led to a strong warming of the Antarctic Peninsula which in turn causes the catastrophic collapse of numerous ice shelves, some of which have been shown to have existed for 10,000 years or more,” she said.
“As these ice shelves collapse, they don’t add to sea level rise (ice shelves are the floating tongue of an ice sheet).
“But with the ice shelves removed, the grounded ice sheet behind them – accelerate into the ocean – and that causes sea level to rise.
“The ice sitting behind Larsen B Ice Shelf, which collapsed in 2002, has sped up eight-fold.
“Most amazingly, those glaciers are still galloping towards the ocean – some 15 years after the first collapse of Larsen B.”
Fortunately the Antarctic Peninsula “doesn’t hold that much ice”.
“If all of it were to slip into the ocean – it would raise sea level by less than 50cm (still a lot of course),” Professor Bertler said.
But if the Ross Ice Shelf, which at about the size of France is the largest on the planet, starts to break up, that would be a bigger problem.
“If those same processes destabilise the Ross Ice Shelf, this could lead to a catastrophic collapse of West Antarctica, adding about 3.3m of sea level rise from West Antarctica alone,” said Professor Bertler, who is leading a project to work out how long it might take for the Ross Ice Shelf to break up.
“Currently, we know little about the how healthy or not the Ross Ice Shelf is but scientists are hurrying to learn more.”
She added that the Ross shelf had been found to be “very sensitive in the past and capable of rapid change”.
Previous research has shown the last time carbon dioxide levels were as high as they are now “West Antarctica, Greenland, and some parts of East Antarctica collapsed, raising sea level by 10 to 20 metres”, she said.
Estimates of how long it would take for such vast ice sheets to collapse run into hundreds of years. One recent study suggested the Thwaites glacier, a linchpin of the West Antarctic ice sheet, could take between 200 to 1,000 years to melt.
However Dr Natalie Robinson, a marine physicist at New Zealand’s National Institute of Water and Atmospheric Research, said the new iceberg, which removed about 12 per cent of the ice from the Larsen C Ice Shelf, was “a ‘normal’, if relatively large, calving event” and “very different from the collapse of its neighbouring ice shelves”.
“There appears to be no evidence that the Larsen C has been subject to the surface melt that led to the rapid and very dramatic collapse of Larsen B,” she said.
“The fact that the Larsen C is able to calve such an enormous, contiguous piece of ice, is more indicative of it being in pretty good health, rather than the opposite.”
And she added that the glaciers that feed into the Larsen C Ice Shelf “only have the potential to contribute one centimetre to global sea level”.
The greatest risk from the giant berg, Dr Robinson said, was the potential danger to shipping, particularly if the giant berg splits into numerous smaller ones which would be harder to track.
And she added: “Some people are keeping an eye on a crack that will create the next iceberg from the front of the Ross Ice Shelf. But this may take 10 years or more.”
Professor Christina Hulbe, an Antarctic researcher at the University of Otago, said also said global warming may not have played a role in the creating of the new iceberg.
“We can't say exactly what influence climate change had on the Larsen C event,” she said.
She added that the Antarctic Peninsula “used to be the fastest warming place on the planet but right now it appears to be cooling”.
“Scientists who study processes in the atmosphere and climate have determined that this is due a change in storms over the Weddell Sea, which is itself due to changes in the atmosphere farther north. Put another way, the recent trend is part of the natural variation around the Peninsula.”
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These images show just how big the Larsen C iceberg is.
To help create a more helpful visual frame of reference, Climate Central has created a series of images showing the ice next to familiar places.
By Brian Kahn
Follow @blkahn
Published: July 12th, 2017
The Larsen C ice shelf has calved an iceberg after months of waiting and watching.
With an area the size of Delaware and a volume of 277 cubic miles, its measurements boggle the mind. Even written comparisons don’t fully convey the hulking hunk of ice currently adrift in the Weddell Sea. After all, can you really imagine 463 million Olympic-sized pools, let alone all those pools filled with ice.
To help create a more helpful visual frame of reference, Climate Central has created a series of images showing the ice next to familiar places. There are a few things to consider as you view these.
First, this is an idealized ice ball. The real iceberg is obviously not uniform and its shape will change as it drifts and melts.
Second, while some of the images show it near coastal locations like New York, that doesn’t mean it will inundate these areas as it melts. It broke off from a floating ice shelf, making its contribution to sea level rise minimal. Gavin Schmidt, a climate scientist at NASA, calculated that it would lead to 0.1 millimeters of sea level rise as it melts.
With those considerations in mind, see what the Larsen C iceberg, technically dubbed iceberg A68, looks like in settings you may be more familiar with than the Weddell Sea.
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Trillion-ton, Delaware-size iceberg breaks off Antarctica's Larsen C ice shelf.
Ice shelves act as giant buffers slowing the flow of land ice toward the ocean. While this break was driven by natural processes, it reflects concerns in the region.
Ice shelves act as giant buffers slowing the flow of land ice toward the ocean. While this break was driven by natural processes, it reflects concerns in the region.
Sabrina Shankman
BY SABRINA SHANKMAN
FOLLOW @SHANKMAN
JUL 12, 2017
“Although this is a natural event, and we’re not aware of any link to human-induced climate change, this puts the ice shelf in a very vulnerable position,” said glaciologist Martin O’Leary. Credit: NASA/John Sonntag
Like a driver facing a crack in a windshield, scientists have been watching a rift growing across a giant ice shelf in Western Antarctica for years, waiting for the day that it would break. This week, a trillion-ton expanse of ice nearly the size of Delaware broke off into the ocean.
"This event will fundamentally change the landscape of the Antarctic Peninsula," scientists involved in Project Midas, which studies the impact of melting on ice shelf dynamics and stability, wrote on its website. The group announced early this morning that satellite data had confirmed the break.
The break that sliced off about 10 percent of the Larsen C Ice Shelf was driven by natural processes, and it isn't going to raise sea level on its own because the ice shelf was already floating on the water. But it can't be viewed in isolation.
Credit: Climate Signals/Climate Nexus
Though it will be years before scientists understand the impacts of the break, what remains of the Larsen C shelf will be drastically altered, and climate change could play a part in driving what happens next.
Antarctica's ice shelves are facing other forces as global temperatures rise. Warmer water has been detected closer to the edges of Antarctica in recent years, and that can accelerate the melting of ice shelves from below. Likewise, warmer air can increase surface melting from above.
The ice shelves act as giant buffers, slowing the flow of glaciers from the frozen land behind them. When an ice shelf disappears, the land-based glacier ice it held back can flow faster into the ocean, directly contributing to sea level rise. After the smaller Larsen B Ice Shelf, just up the peninsula, quickly broke apart over the span of a few weeks in 2002, studies found that the flow of glaciers behind it accelerated sharply.
"Although this is a natural event, and we're not aware of any link to human-induced climate change, this puts the ice shelf in a very vulnerable position," said Martin O'Leary, a glaciologist at Swansea Universit, said as the Midas project announced that the ice shelf had broken. "This is the furthest back that the ice front has been in recorded history. We're going to be watching very carefully for signs that the rest of the shelf is becoming unstable."
Ice shelves of Antarctica. Credit: Ted Scambos/National Snow and Ice Data Center
Jonathan Kingslake, an assistant professor at Columbia University's Lamont-Doherty Earth Observatory, also raised concerns about the stability of the ice shelf and other Antarctic ice shelves amid changes underway in the region. "More broadly, warming on the Antarctic Peninsula is linked to human activity and probably triggered the collapse of two more northerly ice shelves," he said.
For a closer look at the mechanics of ice shelves and some of the risks their breakup creates, here are more sources.
The European Space Agency used satellite data to calculate the new giant iceberg's vital statistics. The results: the area that broke off is about 190 meter thick (623 feet), 6,000 square kilometers (2,300 square miles) at the surface, and contains about 1,155 cubic kilometers of ice, or about 1 trillion tons. "Icebergs calve from Antarctica all the time, but because this one is particularly large, its path across the ocean needs to be monitored as it could pose a hazard to maritime traffic," the ESA said.
The New York Times and The Guardian go into more detail and provide maps and images of how ice shelves hold back the ice on Antarctica, land ice that would raise sea level as glaciers and ice streams flowed more quickly to the ocean. The land upstream from Larsen C is estimated to hold enough ice to raise sea level by 10 centimeters. The National Snow and Ice Data Center and the Antarctic Glaciers website further explain the mechanics and importance of ice shelves and the impacts on neighboring land ice when they break apart.
Changes in the ice and water temperatures around Antarctica also affect wildlife and ecology, both on land and in the ocean. The Long-Term Ecological Project based at Palmer Station, Antarctica, has been tracking climate changes in the West Antarctic Peninsula for over 25 years. A series of reports last year looked at the changing ecology and biology of the region. CBS talked to some of the scientists about the impact of the changing climate on penguins and other life this year.
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