Sea level rise this century may be greater than previously thought, posing risks to hundreds of millions of people who live close to the world's oceans, concludes a new study of ice loss from glaciers and ice caps. The researchers say that in the near future, the giant Greenland and Antarctic ice sheets will contribute less to sea level rise than glaciers and ice caps.
Scientists with the University of Colorado-Boulder's Institute of Arctic and Alpine Research, INSTAAR, and the Russian Academy of Sciences conclude that glaciers and ice caps now contribute about 60 percent of the ice melting into the oceans and the rate has been accelerating over the past decade.
"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," says lead author Emeritus Professor Mark Meier. "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, he says.
Alaska's Columbia Glacier, now discharging about two cubic miles of ice into Prince William Sound every year, is a good example says study co-author Robert Anderson. The Columbia Glacier has thinned up to 1,300 feet in places. It has shrunk by about nine miles since 1980 and is expected to shrink by another nine miles in the next two decades.
The team estimates the 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 does not include the expansion of warming ocean water, which could potentially double those numbers.
A one foot rise in sea level rise typically causes a shoreline retreat of 100 feet or more, and about 100 million people now live within about three feet of the world's shorelines.
The glaciers and ice caps are presently contributing about 100 cubic miles of ice annually to sea level rise - a volume nearly equal to the water in Lake Erie. This volume is rising by about three cubic miles per year, the study shows.