Greenland Jakobshavn Glacier
March 12, 2014

Greenland Ice Is Discharging At Fast Rate: NASA

Lee Rannals for - Your Universe Online

New data obtained by NASA's Operation IceBridge program is shedding new light on how ice sheets in Greenland are changing.

Scientists used satellite observations and ice thickness measurements made by Operation IceBridge to determine the rate at which ice flows through Greenland’s glaciers into the ocean. The findings have shown how glacier flow is affecting the Greenland Ice Sheet and that this process is being dominated by a small number of glaciers.

Ice sheets grow as snow accumulates and gets compacted into ice, but they lose mass when ice and snow at the surface melts and runs off. When this warm up takes place, ice also discharges into the ocean. Scientists calculate the difference between yearly snowfall on an ice sheet and the sum of melting and discharge and label the total as “mass budget.” Ideally, this mass budget would balance out year over year, but for years the Greenland Ice Sheet has had a negative mass budget, meaning it has been losing its mass overall.

Ice discharge is controlled by ice thickness, glacier valley shape and ice velocity. Researchers in the study used data from IceBridge’s Multichannel Coherent Radar Depth Sounder (MCoRDS) to determine ice thickness and sub-glacial terrain. They also used images from satellites like Landsat and Terra to calculate the ice velocity.

"Glacier discharge may vary considerably between years," Ellyn Enderlin, glaciologist at the University of Maine, Orono, Maine and the study's lead author of the paper published in Geophysical Research Letters, said in a statement. "Annual changes in speed and thickness must be taken into account."

The researchers were able to calculate each glacier’s contribution to Greenland’s mass loss and the total volume of ice being discharged from the Greenland Ice Sheet. They found that of the 178 glaciers studied, 15 accounted for more than three-quarters of ice discharged since 2000, and four accounted for about half.

The team also found that the size of these basins did not correlate with glacier discharge rate, which shuffled up the order of Greenland’s largest glaciers.

NASA’s IceBridge study proved to be a valuable source of intel for the researchers studying the ice sheet.

"IceBridge has collected so much data on elevation and thickness that we can now do analysis down to the individual glacier level and do it for the entire ice sheet," Michael Studinger, IceBridge project scientist at NASA's Goddard Space Flight Center, said in a statement. "We can now quantify contributions from the different processes that contribute to ice loss."