Columbia Glacier Photogrammetry

OPP-01-21399这项建议被推荐作为探险研究(SGER)的小额拨款，以记录阿拉斯加哥伦比亚冰川通过快速崩解而持续消退的情况。冰川目前正以每年约1.67公里的速度退缩。伴随着这种快速退缩的是每天高达34米的水流速度，使它成为现在世界上移动最快的冰川。自1982年以来，自18世纪中叶以来，冰川末端已经后退了12公里以上，向海方向(10-15公里)变薄了约200米。在接下来的9个月里，随着冰川末端穿过限制其流动的缺口，冰川的退缩模式和速度可能会发生重大变化。未来几个月的活动可能会为哥伦比亚冰川的长期命运提供重要线索，因为冰川退缩将沿着冰川床位于海平面以下的海峡向上推进。最近的计算表明，根据水流速度继续保持目前的快速或适度下降，搁浅于海平面以下的冰川部分(最低的25公里，冰量约为8×1010立方米)将在5至20年内通过漂浮或崩解而消失。主要调查人员正在继续分析1999年至2000年的摄影测量数据，并将于2001年9月向OPP/ANS提交一份建议。然而，目前冰川末端的位置和新计算的冰下地形可能意味着冰川处于退缩的临界状态，2001年底之前可能会发生重大事件。这笔资金将允许他们在2001年继续进行航空摄影，届时航站楼进入更深的水域并通过一个主要的侧向收缩可能会发生重要的变化。

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.