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July 19th, 2007

Glaciers and ice caps to dominate sea-level rise through 21st century

Mark Meier led a team of INSTAAR and Russian scientists who found that Earth's mountain glaciers and small ice caps are contributing more to global sea-level rise than previously anticipated--more than the massive Greenland and Antarctic ice sheets combined. Co-authors include CU-Boulder INSTAAR researchers Mark Dyurgerov, Ursula Rick, Shad O'Neel, Tad Pfeffer, Robert Anderson and Suzanne Anderson, as well as Russian Academy of Sciences scientist Andrey Glazovsky. Their paper appears in both the online and print editions of Science magazine (July 19th and August 24th, respectively).

The team summarized 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. They concluded that glaciers and ice caps are currently contributing about 60 percent of the ice delivered to the world's oceans and 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. The accelerating contribution of glaciers and ice caps is due in part to increased meltwater at the ice surface. Some glaciers are also experiencing increased meltwater at the base of the ice, which can lead to faster sliding of the glaciers against their beds. This is especially the case for tidewater glaciers that discharge icebergs directly into the ocean, and their analogs, the outlet glaciers from the great ice sheets. Many tidewater glaciers are undergoing rapid thinning, stretching and retreat, which in turn causes them to speed up and deliver increased amounts of ice into the world's oceans.

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