Master thesis defense by Dora Kovacs – Københavns Universitet

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Master thesis defense by Dora Kovacs

Title: Characterizing the ice-ocean interaction at the Upernavik Glacier using in-situ and satellite observations

Abstract

Earlier observations of tide-water glaciers showed extensive glacier flow velocity accelerations in the past decades and the high flow speed is expected to characterize the upcoming years as well (Rignot et al. 2011). Combining data from satellites and time-lapse imagery, near terminus flow velocity fluctuations were analyzed at the northernmost branch of the Upernavik ice stream in north-west Greenland during August 2014. Measurements of atmospheric parameters recorded by in-situ automated weather stations were related to the observed flow speed variations and to calving events in order to find possible causes for the observations. The data revealed a strong correlation (R = 0.56) between ablation change and velocity change that is in alignment with previous reports (Van De Wal et al. 2008). The near terminus surface area grew by 0.0854 km2 between 30.07-31.08.2014. In the same time-period, calving was captured by the camera on eleven days. Days when the glacier calved were most of the time (8 days out of 11) either preceded by or occurred on the same days as faster than average flow. This agrees with previous expectations, as calving and increased flow are often in tune (e.g. Khan et al. 2013). On three occasions fast flow was observed on days immediately after days with calving events. Although, it had been concluded by others that ice front retreat and seasonal flow acceleration does not coincide (Lemos et al. 2018). Several other authors warned against oversimplification when examining the complex relationships in the context of glacier flow, warm induced surface melting, calving and their feedbacks. The driving mechanisms behind these processes are yet to be confirmed.

Keywords: glacier-ocean interaction, calving, satellite and time-lapse imagery