The mass balance of McCall Glacier, Brooks Range, Alaska, USA; its regional relevance and implications for climate change in the Arctic

McCall Glacier has the only long-term mass-balance record in Arctic Alaska. Average annual balances over the periods 1958-72 and 1972-93 were -15 and -33 cm, respectively; recent annual balances; (1993-96) are about -60 cm, and the mass-balance gradient has increased. For an Arctic glacier, with its low mass-exchange rate, this marks a significant negative trend. Recently acquired elevation profiles of McCall Glacier and ten other glaciers within a 30 km radius were compared with topographic maps made in 1956 or 1973. Most of these glaciers had average annual mass balances between -25 and -33 cm, while McCall Glacier averaged -28 cm for 1956-93, indicating that it is representative of the region. In contrast, changes in terminus position for the different glaciers vary markedly. Thus, mass-balance trends in this region cannot be estimated from fractional length changes at time-scales of a few decades. We developed a simple degree-day/accumulation mass-balance model for McCall Glacier. The model was tested using precipitation and radiosonde temperatures from weather stations at Inuvik, Canada, and Barrow Kaktovik and Fairbanks, Alaska, and was calibrated with the measured balances. The Inuvik data reproduce all measured mass balances of McCall Glacier well and also reproduce the long-term trend towards more negative balances. Data from the other stations do not produce satisfactory model results. We speculate that the Arctic Front, oriented east-west in this region, causes the differences in model results.