Mass Balance of West Gulkana Glacier

Annual and longer-term mass-balance calculations provide a means to relate glacier behavior to climate. Selected representative glaciers are monitored for this purpose. West Gulkana Glacier, in the eastern Alaska Range, was among the glaciers mapped during the 1957-58 International Geophysical Year. It was remapped in 1986, after which twenty-nine-year mass balance was calculated. Annual budgets were also calculated for 1985-86 and 1986-87 glacier years. The three-decade record shows steady retreat and mass loss in the glacier's transitional marine-continental climate zone. West Gulkana Glacier is regionally representative of small, low-elevation valley systems. Caution must be exercised in relating its climatic responses to glaciers situated above 1,800 m. A principal objective of the 1957-58 International Geophysical Year was to establish baseline data that could be used later in interpreting environmental trends. An important contribution by American scientists to the effort was the mapping of nine small alpine glaciers that were deemed to be representative of various geographical zones in Washington State and Alaska. The glaciers, which were mapped at the 1:10,000 scale and a 5-m contour interval, stretched from Blue Glacier on the Olympic Peninsula in Washington to Lemon Creek Glacier in southeastern Alaska to six others located poleward from the Gulf of Alaska to McCall Glacier in the Brooks Range. One of the glaciers, West Gulkana, was intended to provide an index to glacierized terrain lying in the eastern Alaska Range, astride the divide between the Delta-Tanana lowlands to the north and the Copper River basin to the south (Fig. 1). Three were probably paramount in the choice of the representative glaciers: inclusion of different glacier-climate regions, the prevailing wisdom that small glaciers were the best medium for understanding relationships between glacier regimen and climate (Heusser and Marcus 1964), and accessibility. Although the representativeness of the small glaciers and, to a lesser extent, the selection of geographical zones may be debated, the existing maps provide a base for subsequent studies. Indeed, at the time of the original * This research was made possible in part by financial support from the American Geographical Society, Arizona State University, and the following U.S. agencies: Army Research Office, Army Cold Region Research and Engineering Laboratory, Northern Warfare Training Center and Cold Regions Test Center, Defense Mapping School, and the U.S. Military Academy. W. O. Field, L. R. Mayo, W. Strauss, H. Brecher, and B. Trapido are thanked for their contributions to the research and its presentation. * DR. CHAMBERS is a visiting lecturer in geography at the University of California, Davis, California 95616. DR. MARCUS is a professor of geography at Arizona State University, Tempe, Arizona 85287. DR. THOMPSON is a permanent associate professor at the U.S. Military Academy, West Point, New York 10996. This content downloaded from 207.46.13.103 on Thu, 20 Oct 2016 04:00:02 UTC All use subject to http://about.jstor.org/terms WEST GULKANA GLACIER FIG. 1-Regional setting of West Gulkana Glacier, Alaska. mapping, it was anticipated that continuing surveys, if carried on over a sufficient period of time, would give the history of wastage and accumulation, and the pattern of variation would provide the basis for more satisfactory and more accurate interpretation of the response of these glaciers to meteorological and other factors (AGS 1960, 3). From 1986 to 1987, the first such efforts were made in Alaska, when a team of scientists remapped West Gulkana Glacier and determined its massbalance changes. This article summarizes the findings of this survey and reports on the inferences that the data permit for three decades of regional climate. West Gulkana Glacier is located in the eastern Alaska Range, only 8 km east of the Richardson Highway and Isabel Pass. It is one of three glaciers that drain the watershed of Phelan Creek and eventually feed into the Delta River; the other two are Gulkana and College glaciers. Some 4 km in length, West Gulkana Glacier flows southward from 2,100 m elevation to 1,325 m; it is well entrenched below 1,800 m (Fig. 2). It attained its maximum postPleistocene advance during the Little Ice Age, circa 1830 (Fig. 3). Neighboring 71 This content downloaded from 207.46.13.103 on Thu, 20 Oct 2016 04:00:02 UTC All use subject to http://about.jstor.org/terms THE GEOGRAPHICAL REVIEW FIG. 2-West Gulkana Glacier 1986. This black-and-white map is a reduced version of the multicolor 1:10,000 original. Copies of the original map may be obtained from the Department of Geography, Arizona State University, Tempe, Arizona 85287, for a period of two years after the publication date of this issue of the Geographical Review. Gulkana Glacier had been the focus of intensive studies by University of Alaska glaciologists in the 1960s (Mayo and Pewe 1963; Rutter 1965), and its regimen has since been monitored by the United States Geological Survey. West Gulkana Glacier, however, has not been investigated, except by aerial photographs, since the 1957-58 mapping project. 72 This content downloaded from 207.46.13.103 on Thu, 20 Oct 2016 04:00:02 UTC All use subject to http://about.jstor.org/terms