ELSEVIER Geomorphology 21 (1998) 207-216 Topographic context of glaciers and perennial snowfields, Glacier National Park, Montana Thomas R. Allen * Department of Political Science and Geography, Old Dominion University, Norfolk, VA 23529-0088, USA Received 17 October 1996; revised 14 May 1997; accepted 28 May 1997 Abstract Equilibrium-line all:itudes (ELAs) of modern glaciers in the northern Rocky Mountains are known to correspond with regional climate, but sl:rong subregional gradients such as across the Continental Divide in Glacier National Park, Montana, also exert topoclimatic influences on the ELA. This study analyzed the relationships between glacier and snowfield morphology, ELA, and surrounding topography. Glaciers and perennial snowfields were mapped using multitemporal satellite data from the; Landsat Thematic Mapper and aerial photography within an integrated Geographic Information System (GIS). Relationships between glacier morphology and ELA were investigated using discriminant analysis. Four morphological categories of perennial snow and ice patches were identified: cirque glacier, niche glacier, ice cap, and snowfield. ELA was derived from overlaid glacier boundaries and Digital Elevation Models (DEMs) within the GIS. DEMs provided topographic variables and models of solar radiation and wind exposure/shelteredness. Regression analysis showed the effects of exposure on snow accumulation, the strong influence of local topography through upslope zone morphology such as cirque backwalls, and the tendency for glaciers with high ELAs to exhibit compactness in morphology. Results highlight the relatively compact shape and larger area of glaciers adjacent to the Continental Divide. Discriminant analysis correctly predicted the type of glacier morphology in more than half the observations using factored variables of glacier shape, elevation range, and upslope area. © 1998 Elsevier Science B.V. Keywords: equilibrium-line altitudes (ELA); Glacier National Park; geomorphometry; topoclimate 1. Introduction Glacier response to climate change has been a focus of wide-ranging research efforts across the natural sciences. Over time, the availability of re- motely sensed imagery becomes an even greater resource for investigating the temporal dynamics of climatically sensitiw~ features such as glaciers. Rec- * Corresponding author. Tel.: +1 757 6833846; E-mail: tra100f@ hamlet.bal.odu.edu ognized as relatively sensitive to climate change, alpine glaciers are increasingly monitored for poten- tial responses to regional greenhouse gas-induced changes. Warren (1991) illustrated that besides pri- mary climate forcing, topographic factors also influ- ence glacier fluctuations in tidewater, lake calving, and land-terminating glaciers in Greenland. Further, in north Norway the pattern of recent glacier reces- sion was linked to the nature of topographic modifi- cation of climate (Gellatly et al., 1986). As such topoclimatic relationships are more precisely de- fined, the analysis may advantageously incorporate 0169-555X/98/$19.00 ¢~ 1998 Elsevier Science B.V. All rights reserved. PII S0169-555X(97)00059-7