SCIENTISTS in Scotland, Wales and Norway are using the rapid decline of ancient ice sheets to help them predict the impact of modern-day climate change.
Ice sheets are massive land-based reservoirs of frozen water and, for the first time, researchers at the universities of Stirling and Tromsø in Norway have reconstructed in detail the evolution of the last sheet that covered Iceland about 20,000 years ago. Their study shows the greatest changes happened when temperatures in the Northern Hemisphere rose by around 3°C in just 500 years.
The maximum rate of ice loss in Iceland at that time was on the same scale seen in West Antarctica and Greenland today, providing worrying evidence of how climate change can alter ice sheets dramatically, leading to rapid rise in sea level.
Dr Tom Bradwell, from Stirling’s Faculty of Natural Sciences, said: “The new modelling experiments, driven by climate data from Greenland ice cores, replicate ice sheet behaviour over the last 35,000 years, showing when it melted the fastest and how it behaved.
“We found that, at certain times, the Icelandic ice sheet retreated at an exceptionally fast rate – more than double the present-day rate of ice loss from the much larger West Antarctic ice sheet – causing global sea level to rise significantly.”
These model experiments, published in Earth-Science Reviews, give an unprecedented view of how the Icelandic ice sheet rapidly reduced in size and volume between 21,000 and 18,000 years ago, mainly through icebergs breaking away from its marine margins. It then collapsed 14,000 years ago, this time abruptly, in response to rapid climate warming.
The Icelandic ice sheet reached a maximum size of 562,000 sq km (216,989 sq m) – an area about the size of France. During its collapse the ice sheet melted rapidly over much of its surface area, decreasing in size by almost two-thirds in only 750 years.
This large volume of ice melting caused a 46cm (18ins) rise in global sea levels – or more than 1mm every two years for over seven centuries – and is equivalent to the ice losses currently being experienced in Greenland. When compared to the length of time it took the Icelandic ice sheet to grow to its full size – approximately 10,000 years – this rate of change is all the more remarkable.
These events put present-day rates of ice sheet change in a new perspective. However, until recently, much of the data needed to reconstruct and model their shape, size and flow existed unseen below sea level.
“By using data from the geological record to constrain model reconstructions of rapid ice sheet change thousands of years ago, we can better predict how contemporary ice sheets will probably react in the future and the serious impact they have on sea level rise,” said Dr Henry Patton, from UiT, the Arctic University of Norway.
The research is part of a collaboration between scientists in the universities of Tromsø, Aberystwyth and Stirling to understand ice sheet evolution.
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