thumbnail

Climatic controls of western U.S. glaciers at the last glacial maximum

Quaternary Science Reviews

By:
,
DOI: 10.1016/S0277-3791(96)00116-3

Links

Abstract

We use a nested atmospheric modeling strategy to simulate precipitation and temperature of the western United States 18,000 years ago (18 ka). The high resolution of the nested model allows us to isolate the regional structure of summer temperature and winter precipitation that is crucial to determination of the net mass balance of late-Pleistocene mountain glaciers in this region of diverse topography and climate. Modeling results suggest that climatic controls of these glaciers varied significantly over the western U.S. Glaciers in the northern Rocky Mountains existed under relatively cold July temperatures and low winter accumulation, reflecting anticyclonic, easterly wind flow off the Laurentide Ice Sheet. In contrast, glaciers that existed under relatively warmer and wetter conditions are located along the Pacific coast south of Oregon, where enhanced westerlies delivered higher precipitation than at present. Between these two groupings lie glaciers that were controlled by a mix of cold and wet conditions attributed to the convergence of cold air from the ice sheet and moisture derived from the westerlies. Sensitivity tests suggest that, for our simulated 18 ka climate, many of the glaciers exhibit a variable response to climate but were generally more sensitive to changes in temperature than to changes in precipitation, particularly those glaciers in central Idaho and the Yellowstone Plateau. Our results support arguments that temperature depression generally played a larger role in lowering equilibrium line altitudes in the western U.S. during the last glacial maximum than did increased precipitation, although the magnitude of temperature depression required for steady-state mass balance varied from 8-18??C. Only the Sierra Nevada glaciers required a substantial increase in precipitation to achieve steady-state mass balance, while glaciers in the Cascade Range existed with decreased precipitation.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Climatic controls of western U.S. glaciers at the last glacial maximum
Series title:
Quaternary Science Reviews
DOI:
10.1016/S0277-3791(96)00116-3
Volume
16
Issue:
6
Year Published:
1997
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Quaternary Science Reviews
First page:
505
Last page:
511
Number of Pages:
7