Abstract
ABSTRACTA comprehensive mid-20th century inventory of glaciers and perennial snowfields (G&PS) was compiled for the American West, west of the 100° meridian. The inventory was derived from U.S. Geological Survey 1:24,000 topographic maps based on aerial photographs acquired during 35 years, 1955–1990, of which the first 20 years or more was a cool period with little glacier change. The mapped features were filtered for those greater than 0.01 km2. Results show that 5036 G&PS (672 km2, 14 km3) populate eight states, of which about 1276 (554 km2, 12 km3) are glaciers. Uncertainty is estimated at ±9% for area and ±20% for volume. Two populations of G&PS were identified based on air temperature and precipitation. The larger is found in a maritime climate of the Pacific Northwest, characterized by warm winter air temperatures and high winter precipitation (~2100 mm). The other population is continental in climate, characterized by cold winter air temperatures, relatively low winter precipitation (~880 mm), and located at higher elevations elsewhere. The G&PS in the Pacific Northwest, especially in the Olympic Mountains, are particularly vulnerable to warming winter air temperatures that will change the phase of winter precipitation from snow to rain, further accelerating glacier shrinkage in the future. Comparison with a recent inventory suggests that the total G&PS area in the American West may have decreased by as much as 39% since the mid-20th century.
Highlights
Glaciers are an important feature of the landscape
Two populations of glaciers and perennial snowfields (G&PS) were identified based on air temperature and precipitation.The larger is found in a maritime climate of the Pacific Northwest, characterized by warm winter air temperatures and high winter precipitation (~2100 mm)
Comparison between the digital outlines and the digital raster images of the paper maps revealed 1243 errors, including missing features, poorly digitized or partly digitized outlines, nonglacial features miscoded as glaciers, spurious splits such that a single glacier is split into two parts as if they were separate features, and different glaciers joined into a single feature.The most frequent error was missing features (600), closely followed by errors in glacier perimeter (511).We corrected all errors to conform to the representation on the hard copy maps, and the final data set, derived from the 1:24,000 topographic maps, is referred to as 24K
Summary
Glaciers are an important feature of the landscape. In temperate zones they are agents of erosion and deposition and modify the landscape in dramatic ways (Kleman, 1994; Benn and Evans, 2010;Thomson et al, 2010). Smaller glaciers have less ability to buffer seasonal runoff variations, and watersheds become more subject to drought (Hall and Fagre, 2003; Moore et al, 2009).The loss of resident ice on the landscape is a major contribution to sea level rise (Meier, 1984; Radić et al, 2014). Glacier inventories provide a snapshot of ice cover across a landscape and have been valuable tools for assessing glacier contribution to sea level change (RadiĆ and Hock, 2010; Pfeffer et al, 2014), to regional hydrology (Yao et al, 2007; Moore et al, 2009), and for assessing high alpine erosion (Mitchell and Montgomery, 2006; Barr and Spagnolo, 2014). Despite a vigorous history of studies on individual glaciers (e.g., Armstrong, 1989; Rasmussen, 2009) and their glacial geology (Davis, 1988; Bowerman and Clark, 2011; Osborn et al, 2012), this region has not been subject to a rigorous glacial inventory
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
