Since the 1990s, the Greenland ice sheet has been losing about 100 billion tonnes of ice a year, a process that most scientists agree is accelerating. ‘The conventional view has been that meltwater permeates the ice from the surface and pools under the base of the ice sheet,’ said Christian Schoof, the study’s author. ‘This water then serves as a lubricant between the glacier and the earth underneath it, allowing the glacier to shift to lower, warmer altitudes where more melt would occur.’ 

However, when Schoof modelled the complex fluid dynamics that occur at the interface of glacier and bedrock, he found that a steady supply of meltwater is well accommodated and drained through water channels that form under the glacier.

‘Sudden water input caused by short term extremes – such as massive rain storms or the draining of a surface lake – however, can’t easily be accommodated by existing channels. This allows it to pool and lubricate the bottom of the glaciers and accelerate ice loss,’ he said.

February 2011