Ancient DNA samples recovered from the bottom of a two-kilometre thick ice sheet in Greenland has shown that the island was much warmer at some point during the last Ice Age than previously believed.
The DNA came from the trees, plants and insects of a boreal forest estimated to be between 450,000 and 900,000 years old. Previously, the youngest evidence of a boreal forest in Greenland was from 2.4 million years ago.
'These findings allow us to make a more accurate environmental reconstruction of the time period from which these samples were taken, and what we've learned is that this part of the world was significantly warmer than most people thought,' said Martin Sharp, a glaciologist at the University of Alberta and a co-author of the paper appearing in the journal Science.
Sharp said the sample suggested that the temperature of the southern Greenland boreal forests 450,000 to 900,000 years ago was probably between 10C in summer and -17C in winter.
The reduced glacier cover in that region also meant the global ocean was probably between one and two metres higher during that time compared to current levels, he said. Harp said the silty ice found underneath the huge Greenland glacier created a perfect, natural 'freezer' to preserve the prehistoric DNA.
Scientists have, in the past, found older organic matter, but they have not found any uncontaminated DNA that is as old or older than the Greenland samples.