Ice cores show that southern Greenland was once covered in lush forests, and indicate that its ice sheet may resist warmer temperatures.

Today, about 85 per cent of Greenland is covered with ice, and the rest with inhospitable Arctic tundra. But Professor Eske Willerslev - a Wellcome Trust Bioarchaeology Fellow from the University of Copenhagen - and colleagues have found that, almost one million years ago, the region was home to a verdant forest similar to that found today in many regions of Canada.

They analysed ice cores from a number of locations in Greenland, including 'Dye 3' in the south of the country. From the base of the 2-km-deep Dye 3 core, they were able to extract DNA dating back to between 450 000 and 800 000 years ago. The DNA came from trees such as alder, aspens, spruce, pine and members of the yew family (and a wide variety of other organisms including beetles, spiders, flies, butterflies and moths). As these tree species prefer temperatures of at least 10°C in summer and no colder than -17°C in winter, the results suggest that southern Greenland was much warmer at the time.

During the last interglacial period (116 000-130 000 years ago), when temperatures were thought to be 5°C warmer than today, and the global ocean probably was 1-2 m higher than it is now, the southern Greenland ice sheet persisted (probably at a thickness of 1000-1500 m), preserving the delicate ancient DNA samples in its 'natural freezer'. This suggests that Greenland's ice sheet was more stable in the face of rising temperatures than previously thought - a finding that may have implications for the current concern over global warming and the stability of the vast sheet.

External links

• Willerslev E et al. Ancient biomolecules from deep ice cores reveal a forested southern Greenland. Science 2007;317(5834):111-4.