EVALUATION OF RELATIONSHIPS BETWEEN SUPRAGLACIAL STREAM DISCHARGE, ABLATION RATES, AND CLIMATE CONDITIONS AT THE MATANUSKA GLACIER, ALASKA

This study presents new data on meltwater influx in the western terminus region of the Matanuska Glacier, Alaska, as determined from surface ablation and supraglacial meltwater stream discharge measured from 22 June to 14 July 2004. The rate of ablation and the discharge for two supraglacial streams within 1 km of the ice margin in the ablation zone were monitored on the 48 km long glacier. Three ablation stakes quantified rates of ice loss daily and a pygmy meter and surface floats measured the velocity of the streams on a daily basis. A data logger near the terminus of the glacier recorded meteorological data every ten minutes to determine how these two modes of ice loss relate to different meteorological conditions. Ensminger et al. (1999) measured an average ablation rate in 1996 of 7 cm/d, with a maximum of 9 cm/d and a minimum of 1cm/d from mid-May to mid-August. During the same months of 1997, they reported a slightly higher average ablation rate of 9 cm/d, with a maximum of 12 cm/d and a minimum of 6 cm/d. In 2004, the average ablation rate was 10 cm/d during the study period, with a maximum of 15 cm/d and a minimum of 4 cm/d. Overall, ablation rates negatively correlate with humidity and positively correlate with wind speed and air temperature. Preliminary results suggest that supraglacial stream discharge positively correlates with air temperature. Total discharge from the Matanuska Glacier appears to lag behind peaks in supraglacial stream discharge and surface ablation by approximately 5 days. These results suggest that, at the time of our study, the subglacial drainage system was not fully developed and that some meltwater influx went into storage at the bed.