Rapid Wastage of Alaska Glaciers and Their Contribution to Rising Sea Level

Abstract

We have used airborne laser altimetry to estimate volume changes of 67 glaciers in Alaska from the mid-1950s to the mid-1990s. The average rate of thickness change of these glaciers was –0.52 m/year. Extrapolation to all glaciers in Alaska yields an estimated total annual volume change of –52 ± 15 km 3 /year (water equivalent), equivalent to a rise in sea level (SLE) of 0.14 ± 0.04 mm/year. Repeat measurements of 28 glaciers from the mid-1990s to 2000–2001 suggest an increased average rate of thinning, –1.8 m/year. This leads to an extrapolated annual volume loss from Alaska glaciers equal to –96 ± 35 km 3 /year, or 0.27 ± 0.10 mm/year SLE, during the past decade. These recent losses are nearly double the estimated annual loss from the entire Greenland Ice Sheet during the same time period and are much higher than previously published loss estimates for Alaska glaciers. They form the largest glaciological contribution to rising sea level yet measured.