NO GLACIAL BUZZSAW AT GLACIER NATIONAL PARK, MONTANA, USA

For some mountain ranges such as the Cascades and the Alps, the altitude of peaks appear to be limited to a certain height above the glacial equilibrium line altitudes (ELAs). This phenomenon, called the “glacial buzzsaw,” exists because glacial erosion is thought to be highly effective above the ELA. To test for this phenomenon at Glacier National Park, Wyoming, USA (GNP), we used an integrated Geographic Information System (GIS) to identify 96 cirques, bowl-shaped landforms created by glacial erosion, to use as proxies for past glacial ELAs. We then compared cirque locations and elevations with precipitation, geology, and current glacial extent to determine whether glaciers are limiting peak altitudes. The presence of a buzzsaw is indicated by a negative correlation between cirque altitude and precipitation. We find the opposite relationship at GNP. Furthermore, the position of cirques do not correlate with altitudes of modern glaciers or peaks, indicating that other environmental factors such as wind or underlying bedrock geology may be altering the expected locations of glaciers. 51% of the cirques are located on NE (downwind) sides of ridges, indicating that windblown snow may override local precipitation as a control on ELA. An equation which models snow accumulation zones was compared against actual glacial extent to observe the effects of wind-blown snow on ELAs. The model predicted glaciers to be present at locations where they are currently not. Geology does not appear to have an affect on cirque altitude. These results show that not all glaciated mountain ranges are clearly limited in height by glacial erosion. Factors such as wind-blown snow can affect glacial mechanics in such a way to make the resulting landforms (e.g., cirque and peak altitudes) not follow expected trends.