Glaciers, ice caps, not Greenland, Antarctica to dominate sea level rise this century

Ice loss from glaciers and ice caps, rather than from the massive Greenland and Antarctic ice sheets is expected to cause more global sea rise during this century, according to a new study by an international team of researchers from the University of Colorado at Boulder and the Russian Academy of Sciences.

Washington, July 20 : Ice loss from glaciers and ice caps, rather than from the massive Greenland and Antarctic ice sheets is expected to cause more global sea rise during this century, according to a new study by an international team of researchers from the University of Colorado at Boulder and the Russian Academy of Sciences.

The researchers used satellite, aircraft and ground-based data from glaciers, ice caps, the Greenland ice sheet, the West Antarctic ice sheet and the East Antarctic ice sheet to calculate present and future rates of ice loss.

Findings revealed that glaciers and ice caps are currently contributing about 60 percent of the world's ice to the oceans and that the rate has been markedly accelerating in the past decade.

"The contribution is presently about 100 cubic miles of ice annually -- a volume nearly equal to the water in Lake Erie -- and is rising by about three cubic miles per year. In contrast, Greenland is now contributing about 28 percent of the total global sea rise from ice loss and Antarctica is contributing about 12 percent," said Emeritus Professor Mark Meier of CU-Boulder's Institute of Arctic and Alpine Research, and lead author of the study.

Greenland is not expected to catch up to glaciers and ice caps in terms of sea level rise contributions until the end of the century, he said.

According to the study, the accelerating contribution of glaciers and ice caps is due in part to rapid changes in the flow of tidewater glaciers that discharge icebergs directly into the ocean.

"Many tidewater glaciers are undergoing rapid thinning, stretching and retreat, which causes them to speed up and deliver increased amounts of ice into the world's oceans," said CU-Boulder geology Professor Robert Anderson, co-author of the study.

"Water controls how rapidly glaciers slide along their beds. When a glacier with its "toe in the water" thins, a larger fraction of its weight is supported by water and it slides faster and calves more ice into the ocean at the glacier terminus. While this is a dynamic, complex process and does not seem to be a direct result of climate warming, it is likely that climate acts as a trigger to set off this dramatic response," he said.

The researchers said their study estimated that accelerating melt of glaciers and ice caps could add from four inches to 9.5 inches of additional sea level rise globally by 2100.

This however, did not include the expansion of warming ocean water, which could potentially double those numbers, they said.

"At the very least, our projections indicate that future sea-level rise may be larger than anticipated, and that the component due to glaciers and ice caps will continue to be substantial," the study said.

"One reason for this study is the widely held view that the Greenland and Antarctic ice sheets will be the principal causes of sea-level rise. But we show that it is the glaciers and ice caps, not the two large ice sheets, that will be the big players in sea rise for at least the next few generations," said Prof. said Meier.

Co-authors include CU-Boulder INSTAAR researchers Mark Dyurgerov, Ursula Rick, Shad O'Neel, Tad Pfeffer, Robert Anderson and Suzanne Anderson, and Andrey Glazovsky from the Russian Academy of Sciences.

The study appears in the July 19 issue of Science Express.

ANI