Date of Award

Spring 1-1-2012

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Geological Sciences

First Advisor

Robert S. Anderson

Second Advisor

Holly Barnard

Third Advisor

Gregory Tucker

Abstract

The two largest glaciers in Yosemite National Park, Lyell and Maclure Glaciers at the head of Lyell Canyon, have dramatically receded over the last century. Their ice is thinning, and volume shrinking. The loss of these glaciers could significantly alter the hydrology of the Tuolumne River and downstream ecosystems, greatly impacting not only hydrology, but the geomorphology, biology and resource management of this alpine landscape. Addressing quantitatively how glaciers will respond to future climate change demands that we understand how small alpine glaciers have responded to climate change since the Little Ice Age. I combine dendrochronology, lake level measurements, climate reconstructions, instrumental records, historical and aerial photography, and measurements of glacier position to constrain both the local meteorology and the glacier response to it. Using a master tree ring chronology developed from 70 lodgepole pines (Pinus contorta) in the nearby valley, I develop a local climate history that extends back through the Little Ice Age. Comparison with other weather records and their proxies suggests that the tree ring width history records most faithfully the history of snowfall, and hence is a proxy for the winter balance of these glaciers. Using a 1D glacier model, and the winter balance record suggested by the dendrology, I can reproduce the glacier extent histories of both glaciers. Model results indicate that their present volumes are less than 5% of volumes in the peak of the Little Ice Age. The work done in this project allows us to understand how glaciers have responded to changes in localized climate in the past, their health in the present, and consider what we might expect heading into the future.

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