Holocene glacier fluctuations on the northern flank of Cordillera Darwin, southernmost South America

摘要

Records of past variability afford context for evaluating present-day glacier behavior and for testing hypotheses of climate change. Here, we use 69 radiocarbon dates of wood and other organic materials in association with glacial deposits to document the behavior of Ventisqueros Marinelli and Brooks in Cordillera Darwin over the past similar to 17,000 years. Recession from the last glacial maximum was early, with most occurring prior to 17,000 yr BP. Any glacial resurgence during the Antarctic Cold Reversal must have terminated within the bounds of Holocene ice fluctuations. By early Holocene time, Ventisquero Marinelli had retreated such that it was no more extensive than it was in AD 1992. We identify several subsequent glacier readvances, but also note long periods of restricted ice extent, particularly in the mid-Holocene. There were times when Holocene glaciers must have been smaller than at present. Our new record from Marinelli shows similarities to other reconstructions of Holocene glacier variation from southern South America, such as at Mt. Sarmiento and the South Patagonian Icefield, suggesting an underlying climate signal. The overall implication is of substantial early Holocene deglaciation followed by repeated advances interspersed with periods of recession when ice extent was smaller than at present. This general pattern of glacier behavior appears to differ from that of New Zealand's Southern Alps and points to the value of a geographic spread of datasets to elucidate the pattern of Southern Hemisphere climate during the Holocene. (C) 2019 Elsevier Ltd. All rights reserved.