New study sheds light on Antarctic ice sheet response during past warm period
- Antarctic ice sheet retreat 3 million years ago caused sea levels to rise by up to 13 meters
- Scientists develop alternative approach to detect how ice sheets respond to past climate change
- With additional loss of Greenland ice sheet, total sea level rise during the Pliocene period was as high as 20 metres
Melting ice sheets 3 million years ago caused global sea levels to rise by up to 20 meters above current levels, according to new research by geographers at the University of Sheffield.
The study, led by Dr Ed Gasson from the University’s Department of Geography and colleagues from the University of Massachusetts in Amherst, has revealed what happened to ice sheets in Antarctica the last time the level of CO2 in our atmosphere was as high as it is today.
Currently, the level of CO2 in the world’s atmosphere is as high as it was 3 million years ago, during the Pliocene period. The Sheffield based researchers have calculated how much the Antarctic ice sheets retreated with this level of CO2 in the atmosphere. In addition to increased CO2 this retreat was caused by changes in the Earth’s orbit, which caused sea levels to rise by up to 13 meters.
Scientists have previously detected how ice sheets responded to changing climate by measuring past sea levels, which is typically achieved by measuring past shore lines. However, the 3 million year time interval between the Pliocene and today may have affected the elevation of Pliocene beaches, making reconstruction of past sea levels difficult.
Now, this study takes an alternative approach. The research used measured changes in the oxygen isotope composition of small calcareous organisms, known as forams, which are found in ocean sediments. Their oxygen isotope composition is a recorder of past ocean temperature and the volume of ice sheets found in regions such as Antarctica.
Although simple calibrations can be used to determine ice sheet volumes from oxygen isotopes, there are added complications that this research has tried to understand.
Most previous studies have assumed that the oxygen isotope composition of ice sheets does not change over time, however the Sheffield research team have highlighted that this is not the case. The study simulated changes in ice sheet oxygen isotope composition using computer simulations, which revealed new estimates of how much sea levels increased 3 million years ago.
These new estimates can now help researchers predict how the world’s ice sheets may react to future changes to our climate.
Dr Ed Gasson, who led an international research team from the University of Sheffield, said: “For a long time we’ve been trying to constrain how high sea levels were during the Pliocene. This study is one more piece of evidence of how sensitive the ice sheets are to rising temperatures.”
The study was conducted with researchers from the University of Massachusetts and Pennsylvania State University. It is published today in the journal Geology.
It further adds to the University of Sheffield’s contribution to global efforts to combat climate change while giving its geography students access to the latest innovations in teaching and research.
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