Scientists have for the first time quantified how the Greenland Ice Sheet reacted to a warm period 8,000-5,000 years ago, providing vital clues to the future of the ice sheet.
Back then temperatures were 2-4 degrees Celsius warmer than they are in the present, researchers noted.
For the new study, scientists spent six summers coring lakes in the ice free land surrounding the ice sheet.
The lakes act as a valuable archive as they store glacial melt-water sediments in periods where the ice is advanced. That way is possible to study and precisely date periods in time when the ice was smaller than present.
"It has been hard work getting all these lake cores home, but it has definitely been worth the effort. Finally we are able to describe the ice sheet's response to earlier warm periods," said Dr Nicolaj Krog Larsen of Aarhus University, Denmark.
The size of the Greenland Ice Sheet has varied since the Ice Age ended 11,500 years ago, and scientists have long sought to investigate the response to the warmest period 8,000-5,000 years ago where the temperatures were 2-4 degrees Celsius warmer than they are in the present.
"The glaciers always leave evidence about their presence in the landscape. So far the problem has just been that the evidence is removed by new glacial advances," said Professor Kurt Kjaer, from the Natural History Museum of Denmark.
"That is why it is unique that we are now able to quantify the mass loss during past warming by combining the lake sediment records with state-of-the-art modelling," said Kjaer.
Their results show that the ice had its smallest extent exactly during the warming 8,000-5,000 years ago - with that knowledge in hand they were able to review all available ice sheet models and choose the ones that best reproduced the reality of the past warming.
The best models show that during this period the ice sheet was losing mass at a rate of 100 Gigaton per year for several thousand years, and delivered the equivalent of 16 cm of global sea-level rise when temperatures were 2-4 degrees Celsius warmer.
The study was published in the journal Geology.
