Research - Category I: Hydrology, Climatology & Hydraulics

Mount Shasta's Glaciers: An Endangered Resource?
(Funded 2002-2003)

Principal Investigator: Slawek Tulaczyk
Department of Earth Sciences
UC Santa Cruz
(831) 459-5207
tulaczyk@es.ucsc.edu

Executive Summary:
The objective of this study is to assess the stability of Mt. Shasta's glacier system through temporal analysis of ice volume and modeling of their possible response to climate warming. Mount Shasta holds the largest total volume of ice in the state, with an equivalent water volume sufficient to cover ~100 square miles with ~2 feet of water. Mount Shasta has a relatively warm climate for such a tall mountain, placing the current elevation of the snow equilibrium line very close to the summit and making the mass balance of the Shasta glaciers extremely sensitive to small changes in temperature and precipitation. This sensitivity has expressed itself in the past through rapid fluctuations in glacier size that appear to be related to short-term climate variability. As an example of this sensitivity, a drought lasting from 1917-1935 coincided with the loss of over half of Mount Shasta's ice volume, resulting in a massive mudflow five miles long and ten feet deep. The health of the Mt. Shasta glacier system could be endangered when faced with decadal scale climate warming trends. The latest climate models predict that northern California will warm by several degrees Celsius over the next century. If this prediction holds true, it is feasible that we may see a significant shrinkage or even a complete extinction of this glacier system in the next several decades.

Seasonal melt of Mt. Shasta glaciers represents a significant dry season and drought period water source to north central California and deterioration of those glaciers could have a significant practical impact on the water supply for the region. Glacial meltwater decreases seasonal variability in mountain runoff, a feature that is particularly important during drought years. Seasonal drainage of Mt. Shasta supplies water into three major northern California river systems and represents the primary water source for three communities situated at the base of the mountain. Water runoff from Mt. Shasta also helps to determine hydrological conditions in the aquatic environments around the mountain, which include many rare endemic, and at least one endangered, species. A large decrease in glacier meltwater runoff during dry periods may put a significant additional hydrological stress on the aquatic habitats around Mt Shasta.

Given the practical and environmental significance of the Mt. Shasta glaciers, it is critical that we determine the present-day health of this system and develop a quantitative model that will serve to predict its future response to changing climatic conditions. We will deliver both of these products by conducting a comprehensive physical survey of the glaciers. The results of this survey will be correlated with historical records of glacier size and corresponding climate to create a numerical model that will be used to assess the effect global warming will have on the Mt. Shasta glaciers. The results of this model will have direct implications for water planning and policy in the region.