Historical Retreat of Alpine Glaciers in the Ahklun Mountains, Western Alaska

The Ahklun Mountains support the only extant glaciers in southwestern Alaska north of the Alaska Peninsula. The glaciers were originally mapped by the U.S. Geological Survey using photogrammetry methods based on 1972–1973 aerial photos. We surveyed for presence or absence of the glaciers by fixed-wing aircraft in 2006. Of 109 glaciers originally mapped, 10 (9%) had disappeared. Using aerial imagery of a subset of 76 glaciers at three time steps between 1957 and 2009, we determined the average rate of areal loss was 45% over 52 y. At this rate, it is likely that all Ahklun Mountain glaciers will be extinguished by the end of the current century.