Columbia Glacier Photogrammetry

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ABSTRACTPfefferOPP-01-21399This proposal is being recommended as a Small Grant for Exploratory Research (SGER) to document to continuing retreat of the Columbia Glacier, Alaska by rapid calving . The Glacier is presently retreating at a rate of approximately 1.67 kilometers (Km) per year. This rapid retreat has been accompanied by flow speeds up to 34 meters (m) per day, making it now the world's fastest-moving glacier. Since 1982, the glacier terminus has retreated more than 12 Km since the mid-eighteenth century and thinned seaward (10-15 kilometers) by approximately 200 m.Significant changes may be occurring in the glacier's pattern and speed of retreat during the next nine months as the glacier terminus passes through a gap which confines its flow. The activities over the next few months may provide important clues about the longer-term fate of Columbia Glacier as the retreat progresses up the channel where the glacier bed lies below sea-level. Recent calculations suggest that, depending on whether flow speeds continue at their present fast rate or decline moderately, the portion of the glacier grounded below sea level (the lowermost 25 km, with an ice volume of ca. 8 x 1010 m3) will be removed by flotation or calving within 5 to 20 years.The Principal Investigators are continuing their analysis of photogrammetric data from 1999 and 2000, and will submit a proposal to OPP/ANS in September 2001. However, the present terminus position and newly calculated subglacial topography may mean that that the glacier is at a critical state in its retreat, and that significant events may occur before the end of 2001. The funds will allow them to continue the aerial photography through 2001 when important changes may occur as the terminus enters deeper water and passes a major lateral constriction.