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Numerical modeling of the Snowmass Creek paleoglacier, Colorado, and climate in the Rocky Mountains during the Bull Lake glaciation (MIS 6)

Published online by Cambridge University Press:  20 January 2017

Eric M. Leonard*
Affiliation:
Department of Geology, Colorado College, Colorado Springs, CO 80903, USA
Mitchell A. Plummer
Affiliation:
Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-2107, USA
Paul E. Carrara
Affiliation:
U.S. Geological Survey, Denver Federal Center, Box 25046, MS-980, Denver, CO 80225, USA
*
Corresponding author.E-mail address:eleonard@coloradocollege.edu (E.M. Leonard).

Abstract

Well-preserved moraines from the penultimate, or Bull Lake, glaciation of Snowmass Creek Valley in the Elk Range of Colorado (USA) present an opportunity to examine the character of the high-altitude climate in the Rocky Mountains during Marine Oxygen Isotope Stage 6. This study employs a 2-D coupled mass/energy balance and flow model to assess the magnitudes of temperature and precipitation change that could have sustained the glacier in mass-balance equilibrium at its maximum extent during the Bull Lake glaciation. Variable substrate effects on glacier flow and ice thickness make the modeling somewhat more complex than in geologically simpler settings. Model results indicate that a temperature depression of about 6.7°C compared with the present (1971–2000 AD) would have been necessary to sustain the Snowmass Creek glacier in mass-balance equilibrium during the Bull Lake glaciation, assuming no change in precipitation amount or seasonality. A 50% increase or decrease from modern precipitation would have been coupled with 5.2°C and 9.1°C Bull Lake temperature depressions respectively. Uncertainty in these modeled temperature depressions is about 1°C.

Type
Articles
Copyright
University of Washington

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