Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 8 September 2019 Peer-reviewed version available at Quaternary 2019, 2, 36; doi:10.3390/quat2040036 Brugger et al. LGM climate in the northern Sawatch Range 1 Climate during the Last Glacial Maximum in the Northern Sawatch Range, Colorado, USA 2 Keith A. Brugger1*, Chester A. Ruleman2, Marc W. Caffee3,4, and Cody C. Mason5 3 1 Geology Discipline, University of Minnesota, Morris, Morris, MN, USA 4 2 U.S. Geological Survey, Denver, CO, USA;
[email protected] 5 3 Department of Physics and Astronomy, Purdue University, West Lafayette, IN, USA 6 4 Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN, 7 USA;
[email protected] 8 5 Department of Geosciences, University of West Georgia, Carrollton, GA, USA;
[email protected] 9 * Correspondence:
[email protected] 10 Abstract: Temperature-index modeling is used to determine the magnitude of temperature depression in 11 the northern Sawatch Range required to maintain steady-state mass balances of six reconstructed glaciers 12 at their extent during the local Last Glacial Maximum (LLGM), dated at ~21 ka. Assuming no significant 13 differences in precipitation compared to modern values, mean annual temperatures in the region were on 14 average 8.8 +0.5/–0.8 °C cooler than they are today. Allowing for modest increases or decreases in 15 precipitation, required temperature depressions only differ by ± 0.2 °C . Temperature depression in the 16 northern Sawatch Range are consistent, although slightly greater, with those determined in other ranges in 17 Colorado using similar approaches.