NON-SURGING DISCHARGE OF THE HUBBARD AND TAKU GLACIERS IN ALASKA'S PANHANDLE RELATING TO SECULAR CLIMATE CHANGE AND GLOBAL WARMING

Through the 20th century, surveys were made of glaciers in the St. Elias District near Yakutat and in the Juneau Icefield District near Alaska's capital city. These reveal a complex regional pattern of simuultaneous advance and retreat. The two largest valley glaciers in these districts, respectively the Hubbard and Taku, are experiencing fast-flow normal discharge advance, without surging effects.

Details of glacier position changes from 1888 to 1913 were mapped by Tarr and Martin for the National Geographic Society. Subsequent documnetation has been rendered by the author's 1946-2003 surveys, also supported by the National Geogrphic Society. Additionally helpful are the surveys of federal agencies, including the military, the U.S. Forest Service, the U.S.G.S., and NASA's Landsat imagery. Dramatic shrinkage has characterized regimes of Guyot and Tyndall Glaciers in Icy Bay and others in Yakutat Bay. On the Juneau Icefield increasing retreat has occurred in low-level glaciers, such as the Herbert, Mendenhall and Llewellyn Glaciers. Paralleling these negative regimes has been expansion and spectacular advance of the multi-tributary Hubbard and Taku Glaciers.

These contrasting regimes reflect dynamic differences in elevation and geographic position of the prime source névés, identified by hypsometric, mass balance and surface flow lag measurements. Differences also result from natural periodicities in atmospheric warming and cooling, producing position changes in the Arctic Front. Since the 1970's there has been a notable shift in the Arctic Front and rise in the regional freezing level. On a hemispheric scale the Polar Vortex has retreated poleward. These shifts are opposed to the natural trend in soloar energy emission and can be ascribed to a super-imposed influence of Global Warming. They also correlate with warming Pacific Ocean SSTP and a pronounced recurrence of El Niño. The implication is that Alaskan coastal glaciers are uniquely sensitive indicators of world-wide climate change.