Short-term Weather Extremes, Not Gradual Warming, Determine Greenland Ice Sheet Flow
10.12.2010 - Water & Oceans, Ice & Snow, Arctic
A new study by the University of British Columbia (Canada) and published in the journal Nature, suggests that sudden changes in the volume of meltwater contribute more towards the acceleration of ice loss from the Greenland Ice Sheet than the gradual warming that has been taking place in the Arctic.
Prior to this new study, the predominating belief had been that that meltwater from the surface of the ice sheet seeped down to the bedrock, where it would act as a lubricant between the outlet glaciers and the bedrock beneath, allowing the glacier to move to lower altitudes, where it would melt further.
However, Dr. Christian Schoof from UBC’s Department of Earth and Ocean Sciences and his colleagues observed that during heavy rainfall, higher water pressure is needed for drainage along the base of the ice. They created computer models that account for the complex fluid dynamics, and found that a steady supply of meltwater was well accommodated and drained through water channels that form under the glacier. However they noticed that existing channels cannot accomodate sudden water fluxes caused by short term extremes such as massive rain storms or the draining of a surface lake. According to Dr. Schoof, this allows the water to pool and lubricate the bottom of the glaciers, accelerating ice loss.
While a steady rise in temperatures and short-term extreme weather conditions have been attributed to global climate change, this study suggests that “Greenland Ice Sheet flow might not be accelerated by increased melting after all," said Schoof. The finding “certainly doesn’t mitigate the issue of global warming, but it does mean that we need to expand our understanding of what’s behind the massive ice loss we’re worried about.”