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Ice flow at a location in the equilibrium zone of the west-central Greenland Ice Sheet accelerates above the midwinter average rate during periods of summer melting. The near coincidence of the ice acceleration with the duration of surface melting, followed by deceleration after the melting ceases, indicates that glacial sliding is enhanced by rapid migration of surface meltwater to the ice-bedrock interface. Interannual variations in the ice acceleration are correlated with variations in the intensity of the surface melting, with larger increases accompanying higher amounts of summer melting. The indicated coupling between surface melting and ice-sheet flow provides a mechanism for rapid, large-scale, dynamic responses of ice sheets to climate warming. [ABSTRACT FROM AUTHOR]

The article explores whether spruce grew in southern Greenland during the Pleistocene period and thus provided evidence that the ice sheet was sufficiently reduced to allow for regional development of boreal forests. It says that there is independent evidence to prove that spruce lived in Greenland in the mid-Pleistocene. Meanwhile, it cites pollen data suggesting that the Greenland ice sheet was much smaller during previous warm periods. It predicts that the Arctic region will likely become warmer than it was during the Pleistocene period and will remain warmer for thousands of years if greenhouse gas concentrations continue to increase over the next century.