Velocity structure, flow instability and mass flux on a large Arctic ice cap from satellite radar interferometry

被引:48
作者
Dowdeswell, JA [1 ]
Unwin, B
Nuttall, AM
Wingham, DJ
机构
[1] Univ Bristol, Bristol Glaciol Ctr, Sch Geog Sci, Bristol BS8 1SS, Avon, England
[2] UCL, Mullard Space Sci Lab, Dorking RH5 6NT, Surrey, England
基金
英国自然环境研究理事会;
关键词
satellite measurements; interferometry; Svalbard; ice caps; ice movement; unsteady flow; mass movements; velocity structure;
D O I
10.1016/S0012-821X(99)00034-5
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
Satellite radar interferometry allows calculation of the ice-surface velocity distribution throughout the largest ice cap in the Eurasian Arctic: Austfonna in eastern Svalbard. Data on ice-cap velocity structure show strong spatial variations observed in unprecedented detail. Ice-cap drainage basins have clearly defined fast-flowing units with marked shear margins at the surface, associated with troughs in the subglacial bedrock identified from 60 MHz ice-penetrating radar. Interferometric measurements show that the velocity structure in most ice-cap drainage basins remained stable over a 2-year period. Unexpectedly, however; in the basin where surface velocities were the highest on the ice cap, at 140 m yr(-1) in winter 1992, the flow rate had halved by winter 1994. A time series of visible-band Landsat imagery shows that this basin was relatively inactive between 1973 and 1991, but had a distinctly disturbed surface in 1993. This flow instability was initiated after summer 1991 and is likely to be a glacier surge or mini-surge, demonstrating the increasing diversity of motion events revealed by radar interferometry. Mass flux through this basin, calculated using ice velocity and thickness data, was 0.1 km(3) yr(-1) in 1992, an increase of up to two orders of magnitude over that prior to flow instability. Calculated balance velocity is an order of magnitude less than the interferometrically derived velocity, implying that the flow rates observed for the fast-flowing unit cannot be sustained under the present climate. (C) 1999 Elsevier Science B.V. All rights reserved.
引用
收藏
页码:131 / 140
页数:10
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