Shows that humans could not have been the culprit.
Greenland was deglaciated for extended periods during the Pleistocene epoch (from 2.6 million years ago to 11,700 years ago), says a study published last week in Nature.
The findings were based on new measurements of beryllium and aluminium isotopes (10Be and 26Al) in a bedrock core taken beneath the Greenland Ice Sheet summit. Such isotopes are introduced by cosmic rays.
Greenland Ice Sheet less than 10% of its current volume
Models indicate that when this bedrock site is ice-free, any remaining ice is concentrated in the eastern Greenland highlands, with the Greenland Ice Sheet reduced to less than ten per cent of its current volume.
More than 280,000 years of ice-free conditions
The longest period of stability of the present ice sheet consistent with the new measurements is 1.1 million years, say the study’s authors. This was preceded, they believe, by more than 280,000 years of ice-free conditions.
Future simulations of the Greenland Ice Sheet should take these nearly ice-free extended periods into consideration, the authors conclude.
If the Greenland Ice Sheet should melt, the authors warn, global sea level could rise about 24.25 feet (7.4 m)1.
Note: I think the Greenland Ice Sheet is about to experience a very strong period of growth, leading to declining sea levels. In fact, I think that period of growth may have already begun.
Nature 540, 252-255 (8 Dec 2016) doi:10.1038/nature20146
Joerg M. Schaefer, Robert C. Finkel, Greg Balco, Richard B. Alley, Marc W. Caffee, Jason P. Briner, Nicolas E. Young, Anthony J. Gow & Roseanne Schwartz
Thanks to Sonya Porter for this link