 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
| . |  |
. |
 by Staff Writers London UK (SPX) Sep 21, 2018
New research on marine sediment layers from Antarctica indicates that the East Antarctic Ice Sheet (EAIS) retreated during extended warm periods in the past, when temperatures were like those predicted for this century. The international research team, led by Dr David Wilson of Imperial College London, used evidence from a previous time in Earth's history, the late Pleistocene, to inform how the EIAS might react to a warming climate. Scientists had previously focused much attention on the West Antarctic Ice Sheet, which predominantly sits on land below sea level, and contributes most of Antarctica's ice melt today. The EAIS, in contrast, mostly lies on land above sea level. It is the largest ice sheet on Earth, at around 60 times the area of the UK. It contains around half of Earth's freshwater but is assumed to be less sensitive to a warming climate. However, the new data, published in Nature, suggest that 2C warming in Antarctica, if sustained over a couple of millennia, would lead to melting in an area of the EAIS that lies below sea level. This has implications for rising global sea levels and global warming's threat to human civilisation. Dr Wilson, from Imperial's Department of Earth Science and Engineering, said: "Studying ice sheet behaviour in the geological past can inform us about future changes. By building a picture of how the ice sheet has grown and shrunk as temperatures have fluctuated, we can understand the response of the EAIS to future warming." The researchers studied the Wilkes Subglacial Basin, one of three major areas where the EAIS sits on land that lies below sea level. If all the ice in this basin were to melt, global sea level would rise by up to four metres. Glaciers, which come from ice sheets, grind up rocks on the continent, and then transport this sediment to the nearby Southern Ocean, leaving behind a record of past erosion by the ice sheet. To understand how warming affected the ice sheet in the past, the team chemically analysed layers of sediment from the ocean floor that originated from the Wilkes Subglacial Basin. They were collected during an expedition of the Integrated Ocean Drilling Program. The researchers studied sediment layers that had settled on the seafloor during four previous warm intervals that occurred between ice ages (interglacials) over the past 450,000 years. They found chemical 'fingerprints' in the sediment that revealed the changing patterns of erosion as the ice sheet advanced and retreated.
The findings show that: + The ice sheet had retreated from its current size during some of the interglacials, when temperatures were as little as two degrees warmer than pre-industrial times. + The most extreme changes in the ice sheet occurred during two interglacial periods 125,000 and 400,000 years ago, when global sea levels were between six and 13 metres higher than they are today. + Ice loss from the EAIS likely made a significant contribution to those higher sea levels in the past. Dr Wilson said: "What we have learned is that even modest warming of just two degrees, if sustained for a couple of thousand years, is enough to cause the ice sheet in East Antarctica to retreat in some of its low-lying areas. "With current global temperatures already one degree higher than during pre-industrial times, future ice loss seems inevitable if we fail to reduce carbon emissions."
Moderate warming could melt East Antarctic Ice Sheet University of Queensland scientist Dr Kevin Welsh was part of a team that used evidence from warm periods in Earth's history to see how the East Antarctic Ice Sheet might react to a warming climate. Dr Welsh said marine sediment layers indicated the ice sheet had retreated during warming in the late Pleistocene period, when temperatures were like those predicted for this century. "Antarctica is around twice the size of Australia, with ice sheets several kilometres thick and containing around half of the world's fresh water," he said. "The East Antarctic Ice Sheet covers about two thirds of the area, and because its base is largely above sea level it was generally thought to be less sensitive to warming climates than the adjacent West Antarctic Ice Sheet. "However, some areas - like the Wilkes Land Subglacial Basin, directly south of Australia - are below sea level and contain enough ice to raise global sea levels by several metres. "The evidence we have suggests that with the predicted 2C warming in Antarctica - if sustained over a couple of millennia - the sheet would start melting in these locations." Dr Welsh, from UQ's School of Earth and Environmental Sciences, said the team chemically analysed layers of sediment deposited on the Southern Ocean floor by glaciers. "We found that the most extreme changes in the ice sheet occurred during two interglacial periods 125,000 and 400,000 years ago, when global sea levels were several metres higher than they are today," he said. "These periods could be analogues for future climates and it seems likely that ice loss from the East Antarctic Ice Sheet contributed to those higher sea levels. "Ice loss contributes to rising global sea levels which are a threat to many coastal communities, and making projections requires a solid understanding of how sensitive these ice sheets are." Imperial College London researcher Dr David Wilson said the findings were extremely concerning for humanity. "With current global temperatures already one degree higher than during pre-industrial times, future ice loss seems inevitable if we fail to reduce carbon emissions," Dr Wilson said.
Even moderate warming could melt Antarctic ice sheet: study Paris (AFP) Sept 19, 2018 Moderate global temperature rises of just two degrees Celsius could still be enough to melt parts of the largest ice sheet on Earth and raise sea levels by several metres, experts warned on Wednesday. As the pace of climate change rapidly outstrips mankind's attempts to rein it in, scientists delved into the distant past of glaciers in eastern Antarctica to predict what lay in store as our planet continues to warm. Climate experts' attention has up until now focused predominantly on ice sheets ... read more
|
|||||||||||||
|
|
| The content herein, unless otherwise known to be public domain, are Copyright 1995-2024 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. General Data Protection Regulation (GDPR) Statement Our advertisers use various cookies and the like to deliver the best ad banner available at one time. All network advertising suppliers have GDPR policies (Legitimate Interest) that conform with EU regulations for data collection. By using our websites you consent to cookie based advertising. If you do not agree with this then you must stop using the websites from May 25, 2018. Privacy Statement. Additional information can be found here at About Us. |
del.icio.us
Digg
Reddit
Google
