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Antarctic ice sheets—thinning faster

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Antarctic glacier from the melting Larsen B iceshelf. CREDIT: Shutterstock

Antarctic ice shelf [Larsen C] is thinning from above and below

Posted: 13 May 2015 05:37 AM PDT

A decade-long scientific debate about what’s causing the thinning of one of Antarctica’s largest ice shelves is settled this week with the publication of an international study in the journal The Cryosphere…. “If this vast ice shelf — which is over two and a half times the size of Wales and 10 times bigger than Larsen B — was to collapse, it would allow the tributary glaciers behind it to flow faster into the sea. This would then contribute to sea-level rise.” The Antarctic Peninsula is one of the fastest warming regions on Earth, with a temperature rise of 2.5°C over the last 50 years. The team, who continue to monitor the ice shelf closely, predict that a collapse could occur within a century, although maybe sooner and with little warning. A crack is forming in the ice which could cause it to retreat back further than previously observed. The ice shelf appears also to be detaching from a small island called Bawden Ice Rise at its northern edge. Professor David Vaughan, glaciologist and Director of Science at BAS, says: “When Larsen A and B were lost, the glaciers behind them accelerated and they are now contributing a significant fraction of the sea-level rise from the whole of Antarctica. Larsen C is bigger and if it were to be lost in the next few decades then it would actually add to the projections of sea-level rise by 2100. “We expect that sea-level rise around the world will be something in excess of 50 cm higher by 2100 than it is at present and that will cause problems for coastal and low-lying cities. Understanding and counting up these small contributions from Larsen C and all the glaciers around the world is very important if we are to project, with confidence, the rate of sea-level rise into the future.”…

 

P. R. Holland, A. Brisbourne, H. F. J. Corr, D. McGrath, K. Purdon, J. Paden, H. A. Fricker, F. S. Paolo, A. H. Fleming. Oceanic and atmospheric forcing of Larsen C Ice-Shelf thinning. The Cryosphere, 2015; 9 (3): 1005 DOI: 10.5194/tc-9-1005-2015

 

Massive Antarctic Ice Shelf [Larsen B] Will Disappear Completely In A Few Years, According To NASA

by Natasha Geiling Posted on May 15, 2015 at 1:08 pm

An Antarctic ice shelf roughly half the size of Rhode Island will disintegrate completely within the next few years, according to a NASA study released Thursday. In 2002, two-thirds of the Larsen B Ice Shelf — which had been intact for more than 10,000 years — broke up in less than six weeks. The remaining portion of the ice shelf covers about 625 square miles along the Antarctic Peninsula, extending toward the southern tip of South America. Using data collected from airborne surveys and radar, a team led by Ala Khazendar at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, found that the remaining portion of Larsen B is weakening very quickly, which is causing the shelf to become increasingly fragmented. Two of its tributary glaciers are also flowing faster and thinning more rapidly, according to NASA.

This was the first study to look comprehensively at the health of the Larsen B remnant and its tributary glaciers, and analysis of the data puts the remnant shelf’s future in question. An increasingly widening rift will eventually split along the entire shelf, the study found, shattering the remnant sheet into hundreds of icebergs that will drift away from the continent’s edge. According to Khazendar, the Larsen B remnant will completely disintegrate by 2020, allowing Antarctic glaciers to flow unimpeded into the ocean. “These are warning signs that the remnant is disintegrating,” Khazendar said in a statement to NASA. “Although it’s fascinating scientifically to have a front-row seat to watch the ice shelf becoming unstable and breaking up, it’s bad news for our planet. This ice shelf has existed for at least 10,000 years, and soon it will be gone.”

Antarctica’s ice shelves are like cliffs of ice that extend from the shelf of the continent out into the ocean. Without ice shelves to impede their movement, Antarctic glaciers flow into the ocean at much faster rates, accelerating global sea level rise. Antarctica has several ice shelves of varying size that hang over the edge of the continent — the Ross Ice Shelf, which is the largest, is about the size of France. The NASA study supports previous research suggesting that Antarctica’s ice shelves are melting at a rate much faster than previously anticipated. In March, research published in Science highlighted the accelerating loss of ice from most of Antarctica’s ice shelves. The melting was most pronounced in the West Antarctic, where losses increased by nearly 70 percent in the last decade. If all the ice that sits on the West Antarctic bedrock is allowed to flow into the ocean, global sea level could rise by nine feet — something that scientists don’t think is likely to happen, though they also aren’t sure how much grounded ice will eventually melt. That will be determined, they say, not only by how much the Earth warms, but by local conditions in Antarctica, including how wind patterns divert warm or cold water to various parts of the continent…

 

Ala Khazendara, , , Christopher P. Borstada, 1, Bernd Scheuchlb, Eric Rignotb, a, Helene Seroussia, The evolving instability of the remnant Larsen B Ice Shelf and its tributary glaciers. Earth and Planetary Science Letters

Volume 419, 1 June 2015, Pages 199–210 doi:10.1016/j.epsl.2015.03.014

 

Sudden onset of ice loss in Antarctica so large it affects Earth’s gravity field

Posted: 21 May 2015 11:39 AM PDT

Scientists have observed a sudden increase of ice loss in a previously stable region of Antarctica. The ice loss in the region is so large that it causes small changes in the gravity field of the Earth.

 

 

Antarctic glaciers thinning so fast, it’s like a switch was flipped (+video)

A new study finds that processes related to global warming are weakening several Antarctic ice shelves surprisingly quickly – causing glaciers to lose large amounts of ice.

By Pete Spotts, Staff writer May 21, 2015

A new study has recorded a sudden and rapid thinning of once-stable glaciers along the southern Antarctic Peninsula, demonstrating that significant changes in glacier mass can occur surprisingly quickly as ocean and air temperatures rise. The findings support what researchers have been seeing in other parts of Antarctica, with scientists warning last year that four key glaciers on the West Antarctic Ice Sheet appear to be on the verge of wholesale retreat with nothing to stop them. The new study points to a common cause among the glaciers it studied: Warm water is melting away the underside of the glaciers where they meet the sea floor, weakening the ice shelves that slow the glaciers’ slide the ocean. The researchers “observe a relatively strong [common] response across multiple glacier systems that clearly points to changing ocean condition as the main culprit,” says Alex Gardner, a glaciologist at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif., who was not a part of the study, in an e-mail

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