quaternary Article Climate on the Blanca Massif, Sangre de Cristo Mountains, Colorado, USA, during the Last Glacial Maximum Keith A. Brugger 1,* , Eric M. Leonard 2, Kurt A. Refsnider 3 and Peter Dolan 4 1 Geology Discipline, University of Minnesota, Morris, MN 56267, USA 2 Department of Geology, Colorado College, Colorado Springs, CO 80903, USA;
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[email protected] Abstract: Temperature-index modeling is used to determine the magnitude of temperature de- pression on the Blanca Massif, Colorado, required to maintain steady-state mass balances of nine reconstructed glaciers at their extent during the Last Glacial Maximum (LGM). The mean temperature depression thus determined is ~8.6 +0.7/−0.9 ◦C where the uncertainties account for those inherent in the glacier reconstructions, in model parameters (e.g., melt factors), and possible modest changes in LGM precipitation. Associated equilibrium-line altitudes (ELAs) exhibit a statistically significant directional dependency being lower toward the north and east. Under the assumption that regional temperature change was uniform, required changes in precipitation vary systematically—also exhibit- ing a directional dependency coinciding with that in ELAs—and indicate increases (over modern) occurred on the eastern side of the massif while decreases occurred on the western side. This disparity represents a strengthening of a precipitation asymmetry, particularly winter precipitation, which Citation: Brugger, K.A.; Leonard, E.M.; Refsnider, K.A.; Dolan, P.