The warming period, known as Marine Isotope Stage 11, resulted in a sea-level rise of about six to 13 metres above present levels. To find out how much of that rise could be attributed to Greenland, a team of researchers examined sediment cores collected off the island’s coast. By sampling the chemistry of glacial stream sediment on the island, they were able to ‘fingerprint’ the sediments coming from different parts of Greenland. Because the sediments are only deposited when there’s enough ice to erode the terrain, the absence of deposits in the sediment suggests the absence of ice.

The analysis suggested that the deglaciation in southern Greenland would have accounted for between four and six metres of global sea-level rise. ‘The climate 400,000 years ago wasn’t that different to what we see today, or at least what is predicted for the end of the century,’ said one of the study authors, Anders Carlson of Oregon State University. ‘The forcing was different, but what is important is that the region crossed the threshold, allowing the southern portion of the ice sheet to all but disappear. This may give us a better sense of what may happen in the future as temperatures continue to rise.’

This story was published in the August 2014 edition of Geographical Magazine