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The Antarctic ice cap. Credit: Stephen Hudson / Wikipedia
New research on Antarctic marine sediment layers indicates that the East Antarctic Ice Sheet (EAIS) has receded for long, warm periods in the past, while temperatures were forecast for this century .
The international research team, led by Dr. David Wilson of Imperial College London, used evidence from the ancient period of Earth's history, the late Pleistocene, to explain how the SEIA could react to a warming climate.
Scientists had already drawn a lot of attention to the Western Antarctic ice sheet, which relies mainly on land below sea level, and is now contributing most of the melting ice of Antarctica.
The EAIS, by contrast, relies mainly on land located above sea level. It is the largest ice cap on the planet, about 60 times the area of the United Kingdom. It contains about half of the freshwater of the Earth, but it is assumed that it is less sensitive to global warming.
However, the new data, published today in Nature, suggest that the warming of 2 ° C in Antarctica, if it were to last a few millennia, would lead to a melting in an area of the AAIS below sea level. This has implications for the rise of the level of the sea and the threat of global warming for human civilization.
Dr. Wilson of Imperial's Department of Earth Sciences and Engineering said, "The study of ice cap behavior in the geological past can inform us of future changes. can understand the answer of EAIS to future warming. "
The researchers studied the Wilkes Subglacial Basin, one of the three main areas where EAIS is located on land below sea level. If all the ice in this basin were to melt, the from the sea could increase by four meters.
The glaciers, which come from ice caps, crush rocks on the continent, then transport these sediments to the nearby Southern Ocean, leaving behind a trace of erosion through the ice cap.
To understand how warming has affected the ice cover in the past, the team chemically analyzed layers of ocean bottom sediments from the Wilkes subglacial basin. They were collected during an expedition of the integrated ocean drilling program.
The researchers studied the sediment layers that had settled on the seabed during four previous warm intervals that occurred between (interglacial) glaciations over the past 450,000 years. They found chemical "fingerprints" in sediments that revealed changes in erosion as the ice sheet progressed and retreated.
The results show that:
- The icecap had declined relative to its current size during some interglacial glaciations, while temperatures were only two degrees higher than the pre-industrial period.
- The most extreme changes in the ice cap occurred during two interglacial periods, 125,000 and 400,000 years ago, when the global sea level was between six and 13 meters higher than today. hui.
- Ice loss due to EAIS probably contributed significantly to the sea level rise in the past.
Dr. Wilson said, "What we have learned is that even a modest warming of only two degrees, if it is maintained for a few thousand years, is enough to cause ice floes in the water. East Antarctica in some of its lowlands.
"With current global temperatures already one step ahead of pre – industrial levels, future ice loss seems inevitable if we fail to reduce carbon emissions.
Explore more:
Much of East Antarctica has remained frozen for 8 million years
More information:
Ice loss from the East Antarctic Ice Sheet during late Pleistocene interglacials, Nature (2018). DOI: 10.1038 / s41586-018-0501-8, https://www.nature.com/articles/s41586-018-0501-8
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