SENSITIVITY OF ALPINE GLACIERS TO CLIMATE CHANGE AND PREDICTIONS OF THE DEMISE OF WYOMING’S GLACIERS

Alpine glaciers across the globe are rapidly receding in apparent response to the pronounced warming of the last century. In the U.S., for example, the number of glaciers in Glacier National Park decreased from 150 to 37 over the last 150 years and some scientists predict that the remaining glaciers will disappear completely by the 2030. Glacial sensitivity to climate change is however, significantly dependent on glacier size, so determining the response to a prescribed change in climate is not always straightforward. Sensitivity to warming, for example, might decrease if the accumulation area retreats further and further into areas where insolation is severely limited by surrounding topography, and the sensible heat flux becomes an increasingly larger part of the energy flux associated with melting. To demonstrate the varying sensitivity of glaciers as they change size, we use a 2-D, in-the-plane glacier model that combines transient ice flow calculations with energy-balance derived computation of the spatially distributed accumulation / ablation rate. Using examples from the northern Rockies to the Sierra Nevada, we demonstrate how the model can be used to estimate paleoclimatic conditions associated with small-scale (since the Little Ice Age) to large-scale (since the last glacial maximum) changes in glacial extent and illustrate how it can provide insight as to what seemingly second-order climatic parameters must be included to accurately model the existing snow and glacier distribution. Finally, using estimates of changes in temperature and precipitation that will likely occur in the northern Rockies during this century, we illustrate how the demise of the extant glaciers in Grand Teton National Park and the Wind River Range, Wyoming might progress.