Remote sensing of ice cap outlet glacier fluctuations on Nordaustlandet, Svalbard

Landsat multispectral scanner images and 1:50, 000 scale aerial photographs are used to measure marginal fluctuations in 22 outlet glaciers of the Nordaustlandet ice caps, Svalbard, for all or parts of the period 1969 to 1981. Little was previously known about the behaviour of these glacier termini. Digital analysis of Landsat computer compatible tapes yielded measurement errors of less than ±150m, whereas data extracted from aerial photographs had an accuracy of ±25 m. Of the 22 glacier termini examined using aerial photographs, 15 were retreating, four were static and three were advancing. Retreat was usually in the order of hundreds of metres during the period of observation. For any outlet glacier, retreat was probably a result of either (1) glacier response to climatic wanning since the early part of the 20th century, or (2) stagnation and thinning during the quiescent period between surges. Short term iceberg calving events may also be responsible for retreat in a few cases. All observed outlet glaciers of Austfonna were static or retreating between 1969 and 1981, but analysis of Landsat imagery and aerial photographs showed that five outlet glaciers from Vestfonna and one from Vegafonna were advancing for all or part of that period. Bodleybreen advanced by a mean of 440 and a maximum of 580m a^?1 between 1976 and 1981. Bodleybreen, Søre Rijpbreen, and Palanderbreen are identified as surging, based on increases or changes in the pattern of surface crevassing. The ice streams Aldousbreen, Frazerbreen, and Idunbreen also advanced between 1976 and 1981, but surface crevasse patterns remained largely unaltered and surging is not inferred.