Retreat Of Yosemite’s Small Glaciers And Implications For Downstream Hydrology
Abel, Kali M 1 ; Anderson, Robert S 2 ; Stock, Greg 3
1 University of Colorado and INSTAAR
2 University of Colorado and INSTAAR
3 National Park Service
The two largest glaciers in Yosemite National Park, Lyell and Maclure, are rapidly receding with their ice thinning and mass shrinking. The two glaciers presently provide Lyell Canyon and the Tuolumne Valley with their late season cold fresh water. Nearby catchments with similar basin areas have already lost their ice-melt source and are bone-dry during the late summer. The decline and ultimate loss of these two glaciers will significantly alter the hydrology of the headwaters of the Tuolumne River, greatly impacting the geomorphology and ecology of the region, with attendant challenges for the management of resources.
We will address the historical, current and future state of glaciers in the headwaters of the Tuolumne. We seek to explain both the spatial distribution of Little Ice Age glaciers and why present glaciers exist in some basins and not in others. We employ photographs and sketches from John Muir, G.K. Gilbert, I.C. Russell and the USGS to document former extents of the Lyell and Maclure Glaciers. To explore the hydrological impacts of the decline of the Lyell and Maclure Glaciers, we intend to construct a detailed snowmelt hydrological model designed both to reproduce and present hydrographs from their basins, and to predict how these hydrographs will change as glacial area declines yet further. The snowmelt model must honor the observation that loss of snow is highly non-uniform in the landscape and is greatly affected by shadowing from direct solar radiation. These results should provide a model of alpine hydrologic change in presently glacierized Western North America as climate warms.