Location of two glacier surges in West Greenland

The registration of West Greenland glaciers was completed in 1983. Around 5000 local glaciers and lobes from the Inland lce have been located. Indications of surging behaviour have been noted at a restricted number of these, and the two localities with the best documentation and most peculiar features are described below. One is an example of a 'periodic surge', while the other is essentiaIly a 'permanent surge'. The main characteristic of glacier surges is a rapid transfer of large volumes of ice from a reservoir area (usually to the snout), so that velocities are 10 to 100 times those of normal glaciers. Rates of movement of surging glaciers usually reach 1 m or more per day (Paterson, 1981). The strong movement leaves diagnostic features on the glacier surfaee in the form of chaotic crevassing or looped moraines. Local glaciers ean only provide enough ice to maintain high flow rates for a short time, and the catastrophic advances of such 'periodic surges' are often repeated with reported intervals of 20-100 years. Since some of the outlets from the Greenland Inland lce move permanently with high velocities the concept of surging has been extended to cover these cases as well, but as 'permanent surges' (Hughes, 1978; Weertman, 1983). The ice sheet here provides sufficient ice for the permanent maintenance of high flow rates.