HR: 09:15h
AN: U51A-06    [Abstracts]
TI: Glacier Shrinkage and Effects on Alpine Hydrology
AU: Basagic, H
EM: basagic@pdx.edu
AF: Departments of Geology and Geography Portland State University, 1721 SW Broadway, Portland, OR 97207 United States
AU: * Fountain, A G
EM: andrew@pdx.edu
AF: Departments of Geology and Geography Portland State University, 1721 SW Broadway, Portland, OR 97207 United States
AU: Clark, D H
EM: doug.clark@wwu.edu
AF: Geology Department Western Washington University, 516 High Street, Bellingham, WA 98225 United States
AB: Alpine glaciers cover an area of about 553 km$^{2}$ in seven western states of the American West. With few exceptions, all glaciers have been shrinking over the past century and the rate of shrinkage has accelerated over the past few decades. Overall, smaller glaciers exhibit greatest shrinkage, relative to their size, compared to larger glaciers. Preliminary results from studies of glacier change in several national parks reveal the spatial pattern of glacier change. Glacier shrinkage, while contributing to global sea level change, has two important local effects. First, the net release of water from its storage in the frozen state enhances overall stream discharge. Second, the shrinking area of glaciers reduces their moderating effect on stream flow, particularly during late-summer and drought periods, and shifts peak runoff towards early summer. Consequently these alpine basins become more susceptible to future drought. In addition to these "clean" glaciers, debris-covered glaciers are probably important as well. Debris-covered glaciers melt at much slower rates than adjacent "clean" glaciers, with reduced daily variations in melt because of the insulation provided by the surface debris layer. The number and extent of debris-covered glaciers in the American west is not well known therefore their hydrological contribution is uncertain. However, if the number of debris-covered glaciers can be scaled from an inventory of those in the Rocky Mountain National Park (Achuff, 2003), the volume of debris-covered ice may be considerable. From an ecological perspective, the greatest effects are in the high alpine regions where glacier recession opens new areas for biological expansion, and where the hydrological dependence on glaciers is greatest. Lesser effects, related to suspended sediment loads, are felt well downstream (10's km) from glaciers.
DE: 1655 Water cycles (1836)
DE: 1827 Glaciology (1863)
DE: 1860 Runoff and streamflow
DE: 1863 Snow and ice (1827)
SC: Union [U]
MN: 2004 AGU Fall Meeting