UNSUSTAINABLE GLACIER ABLATION AT 78° N LATITUDE, LINNE’BREEN, SVALBARD
Ablation measurements at eight centerline locations were taken for seven time intervals over the entire 2004 ablation season (mid-April to mid-September). Air temperature was continuously recorded at 30-minute intervals from 3 proximal moraine locations while standard meteorological observations were recorded at 6 km down valley. To better understand the forcing of Linnebreens mass balance, weekly ablation measurements were correlated to meteorological observations. Aerial photographs (1936, 61, 69, 90, and 95) were used to quantify the historic terminus retreat. The present terminus location was measured with differential GPS.
In 2004 the highest ablation rates occurred during late-July and early-August, corresponding to peak summer temperatures. Meteorological records from Isfjord Radio, approximately 12 km from Linnebreen, show that the summer of 2004 was 1.4°C warmer than the 1976-2004 average. A net mass balance of 1.21 m in water equivalents was measured and the entire glacier was below the seasonal ELA. Photo analysis reveals an average retreat rate of 17 m/yr since 1936 with a rate of 41 m/yr during the past 14 years.
Temperature was found to be the main agent of ablation on Linnebreen. By separate methods, estimates of Linne'breen's complete melt were calculated between 15-50 years. Continued observations will provide more data to better evaluate the forcing of negative mass balance and add to the growing evidence of climate change in the high Arctic.