Short-term variations in ice dynamics during the spring and summer period on Storglaciären, Kebnekaise, Sweden.

Abstract: Two Differential GPS (DGPS) stations were set up on Storglaciären in the upper and lower part of the ablation area to study short term variations of Storglaciären’s motion. The study period lasted from April to July 2009 and the DGPS logged data every second. Station 14, was situated over an overdeepening in the subglacial bedrock topography in the upper part of the ablation area, and was functioning the whole study period. Station 7, situated in the lower part of the ablation area, only lasted for nine days and only overlapped five days with station 14. There was a clear lag in ice motion between the two stations which indicates longitudinal coupling between the upper and the lower part of the ablation area. Station 14 pushed from up-glacier during the first acceleration event at the 24th of April and when the velocity decreased station 7 pulled from down-glacier.  The total movement of the DGPS station was 26 m during the study period. The velocity was well correlated to the external changes in temperature and precipitation. It appears to be eleven days lag in response time from April to middle of May, but after mid May the glacier responded directly to melt acts such as temperature changes and precipitation events. The delay most likely depended on the hydrological system was not entirely evolved during early spring. During the summer the system evolves which makes the glacier to respond directly to external changes. There were four major acceleration events during the study period and after the accelerations the velocity went back to the same low state as before. These cannot be interpreted as spring events as spring events should lead to an increase in the overall velocity. The temperature fluctuated during the whole study period which affects the melting rate and input and development of the hydrological system. To get a clear spring event a marked and substantial onset of melt season is needed.