Abstract
Aircraft laser‐altimeter surveys in 1993 and 1998 over Kangerdlugssuaq Glacier in east Greenland reveal thinning, over the 5‐year interim, of several meters for all surveyed areas within 70 km of the seaward ice front, rising to 50 meters in the final 5 km. Such rapid thinning is best explained by increased discharge velocities and associated creep thinning, most probably caused by enhanced lubrication of the glacier bed. The calving ice front over the past decade has occupied approximately the same location as in 1966. Velocity estimates for 1995/96 are about the same as those for 1966 and 1988, but significantly less than for 1999, suggesting that major thinning began after 1995.
Highlights
Introduction contributedto the observedthinningAssuminga positive degree-da(yPDD) ablationfactorof 8mmof water/PDDforAspartofa NASAsurveoyftheGreenlaincdesheebty ice or 3 mm of water/PDD for snow (Braithewaite, 1995), the airbornelaseraltimete(rKrabillet al., 1999), repeast urface- increasein averagesummertemperaturecorrespondsto a elevationprofilesalong the final 80 km of the surfaceloweringof about25 cm/yrfor eitherice or snow,orKangerdlugssGulacqieirn eastGreenlan(Fdigure1)were obtainedon 23 June,1993and15and19 July,1998
KangerdlugssuaqGlacier has high ice velocities most probably associated with basal sliding
Thicknessand velocity to be constantacrossthe width, and Followingour observationsof suchrapid thinning,we with the equivalent1993 thicknessof 510 m, the glacierthen obtained SPOT multi-spectral 30-m resolution images dischargedabout 13 cu km of ice per year into the ocean acquiredon April 14, and June 12, 1999, and determined glacier velocities by correlating reflectance properties betweenthe two images(Scamboset al., 1992). This is the same methodused by Dwyer (1995) to estimatethe 1988 velocities from Landsat data
Summary
Introduction contributedto the observedthinningAssuminga positive degree-da(yPDD) ablationfactorof 8mmof water/PDDforAspartofa NASAsurveoyftheGreenlaincdesheebty ice or 3 mm of water/PDD for snow (Braithewaite, 1995), the airbornelaseraltimete(rKrabillet al., 1999), repeast urface- increasein averagesummertemperaturecorrespondsto a elevationprofilesalong the final 80 km of the surfaceloweringof about25 cm/yrfor eitherice or snow,orKangerdlugssGulacqieirn eastGreenlan(Fdigure1)were obtainedon 23 June,1993and15and19 July,1998. KangerdlugssuaqGlacier has high ice velocities most probably associated with basal sliding. Some glaciers periodicallysurge,with long,comparativelyquiescenpt eriods when ice velocities are low and the ice slowly thickens, interspersebdy brief surgeswhenice velocitiesincreaseby a factor of 10 or more and the ice rapidly thins
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