A new study to come out of the University of British Columbia has shown that sudden changes in the amount of meltwater contributes more to the acceleration, and thus the eventual loss, of the Greenland ice sheet than the gradual increase of temperature, reversing previously thought views on the matter.
“The conventional view has been that meltwater permeates the ice from the surface and pools under the base of the ice sheet,” says Christian Schoof, an assistant professor at UBC’s Department of Earth and Ocean Sciences and 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 the new study – to be published in the most recent edition of the journal Nature – shows that the steady but slow meltwater supply that results from global warming may in fact slow down glacier flow, whereas sudden water input does more to speed up and spread the glaciers which eventually leads to more meltwater.
Schoof noted that during heavy rainfalls higher water pressure was required to force drainage along the base of the ice. Creating a complicated computer model to account for all the variables, Schoof found that a steady supply of meltwater is actually well accommodated for by water channels that form underneath the glacier.
“Sudden water input caused by short term extremes – such as massive rain storms or the draining of a surface lake – however, cannot easily be accommodated by existing channels. This allows it to pool and lubricate the bottom of the glaciers and accelerate ice loss,” says Schoof, who holds a Canada Research Chair in Global Process Modeling.
“This 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,” says Schoof.