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Free keywords:
deglaciation; glacial geomorphology; digital elevation model;
ELA depression; tropical glaciers; Andes; last glaciation;
Holocene; Little Ice Age
Tropical south-america; age calibration; andes; climate;
altiplano; glacier; bolivia; paleoclimate; retreat
Abstract:
Moraine chronology is combined with digital topography to model deglacial rates of paleoglacier volumes in both the Huancane Valley on the west side of the Quelccaya Ice Cap and the Upismayo Valley on the northwest side of the Cordillera Vilcanota. The fastest rates of deglaciation (39 x 10(-5) to 114 x 10(-5) km(3) yr(-1) and 112 x 10(-5) to 247 x 10(-5) km(3) yr(-1) for each valley, respectively) were calculated for the most recent paleoglaciers, corresponding to the last few centuries. These results are consistent with observations in the Venezuelan Andes showing high rates of deglaciation since the Little Ice Age. These rates also fall within the range of 20th century rates of deglaciation measured on the Quelccaya Ice Cap (29 x 10(-5) to 220 x 10(-5) km(3) yr(-1), Brecher and Thompson, 1993; Thompson, 2000). These results imply that rates of deglaciation may fluctuate significantly over time and that high rates of deglaciation may not be exclusive to the late 20th century. Equilibrium line altitude (ELA) depressions for the ice volumes of the last glaciation modeled here were computed as 230 in for the Quelccaya Ice Cap and 170 in for the Cordillera Vilcanota. Maximum ELA depressions are lower than previously published: <500 in for the Cordillera Vilcanota and <400 in for the Quelccaya Ice Cap. These lower values could imply a topographic control over paleoglacier extent. (C) 2002 University of Washington.
