Preliminary Forecast of the Advance of Hubbard Glacier and Its Influence onRussell Fiord, Alaska

摘要

A slow but persistent advance of Hubbard Glacier in southeast Alaska has beenobserved since about 1895. Post and Mayo (1971) predicted that the advancing glacier would dam Russell Fiord by about 1990. After a closure, runoff from glaciers and adjacent areas causes the level in 'Russell Lake' to rise until the ice dam fails or a former overflow channel at the south end of the fiord is reached at 39.96 m altitude (Paul, 1988). Overflow on the south end of the fiord will enter the upper reaches of Old Situk Creek, a tributary to the Situk River. Overflow is expected to increase the average discharge of the Situk River by tenfold (Paul, 1988). The physical, social, and economic impacts of such a change in the flow of the Situk River prompted an evaluation of the activity of Hubbard Glacier with regard to possible closure of Russell Fiord. To address these concerns, the U.S. Geological Survey study was made in cooperation with the U.S. Department of Agriculture, Forest Service and the National Park Service. The purpose of the report is to present a description of current (1990) conditions and ongoing changes at Hubbard Glacier that are the physical basis for a forecast of possible future closures of Russell Fiord. The data needed to update these predictions and provide warnings of possible closures are also evaluated.