Supraglacial lakes monitoring using SAR imagery at Jakobshavn Isbræ, Greenland

Abstract

Supraglacial lakes are a common feature on the Greenland ice sheet. They are mainly found during the melt season which takes place during the summer months when there is a positive net energy flux between the atmosphere and the ice sheet surface which generates surface melt. The lakes can undergo rapid draining events through cracks and moulins causing large influxes of meltwater volumes to the ice-bedrock interface leading to enhanced basal sliding. As increased ice velocities are capable of transporting ice faster to the terminus, calving rates might increase, causing a direct impact on the mean sea level rise. The objective of this study is to monitor supraglacial lakes remotely using Sentinel- 1 SAR imagery, and to assess the influence of supraglacial lake draining events on ice speed velocity fluctuations on the Jakobshavn Isbræ, Greenland. Past studies have shown that ice front retreat is the main trigger of large fluctuations in ice velocity, however, the results here show a potential linkage between draining events and the glacier velocity fluctuations. For instance, between 1st July – 25th July, 2019 I found a speed-up of 856 m yr-1, which coincides with a total lake area decrease of 6.4 km2. I also found, in agreement with other studies, that draining events alone should not account for all velocity variability, with terminus position and mélange rigidity both acting as main drivers.