Non-climatic control of glacier-terminus fluctuations in the Wrangell and Chugach Mountains, Alaska, U.S.A.
AbstractFluctuations of glacier termini were studied in two regions in Alaska. In the Wrangell Mountains, 15 glaciers on Mount Wrangell, an active volcano, have been monitored over the past 30 years by surveying, photogrammetry and satellite. Results, which are consistent between different methods of measurement, indicate that the termini of most glaciers were stationary or retreating slightly. However, the termini of the 30 km long Ahtna Glacier and the smaller Center and South MacKeith Glaciers began to advance in the early 1960s and have advanced steadily between 5 and 18 m a−1since then. These three glaciers flow from the active North Crater, where increased volcanic heating since 1964 has melted over 7 x 107m3of ice. We suspect that volcanic meltwater has changed the basal conditions for the three glaciers, resulting in their advance.The terminus fluctuations of six tide-water and near-tide-water glaciers in College Fjord, Prince William Sound, have been monitored since 1931 by surveying, photogrammetry and, most recently, by satellite imagery. Harvard Glacier, a 40 km long tide-water glacier, has been advancing at an average rate of nearly 20 ma−1since 1931, while the adjacent Yale Glacier has retreated at approximately 50 ma−1during the same period though, for short periods, both of these rates have been much higher. The striking contrast between the terminus behavior of Yale and Harvard Glaciers, which parallel each other in the same fiord, and are derived from the same snowfield, supports the hypothesis that their terminus behavior is largely the result of dynamic controls rather than changes in climate.
