New Details of Glacier Melt Could Mean Better Sea Level Rise Forecasts

New understanding of how melting ice during the summer affects glacier movement could help increase the accuracy of sea level rise predictions, according to a report published in Proceedings of the National Academy of Sciences.

Researchers from the Universities of Edinburgh, Sheffield, Aberdeen Tasmania and Newcastle examined the effects of ice melt on the Greenland Ice Sheet during 2012 when an exceptionally warm summer triggered unprecedented levels of melting.

Ice gradually flows from the center of the ice sheet toward the margins, where it ultimately melts or breaks off into the ocean in a process called calving. Knowing how fast this movement occurs, the researchers stress, is vital for accurately predicting the ice sheet's contribution to sea level rise.

During the summer, ice on the surface melts, draining to the bed of the ice sheet and initially causing water pressure at the base to rise. As this happens, the steady march of the glacier speeds up, at times moving as much as twice as fast in the summer when compared to the winter, according to the study's findings.

Even at these rates, the researchers found that fast summer ice flow is cancelled out by winter's slow speeds due to large drainage channels created beneath the ice by meltwater, which help to lower the water pressure and, in turn, reduce the sliding speed.

Based on this, the researchers argue that movement in the parts of the ice sheet that terminate on land are insensitive to surface melt rates.

As Professor Peter Nienow of the University of Edinburgh's School of GeoSciences points out, while the record summer melt failed to increase ice motion, hotter summers still mean an increase in the speed at which ice sheets.

"Furthermore," he added. "it is important that we continue to investigate how glaciers that end in the ocean are responding to climate change."