Lacustrine ice-margin dynamics in west Greenland

There has been a progressive increase in the number and area of ice-marginal lakes along the western margin of the Greenland Ice Sheet (GrIS) since the late 1980s. Ice-marginal lake formation and growth have been widely associated with accelerated rates of mass loss and terminus recession at alpine glaciers, yet their impacts on the GrIS have remained unquantified. This thesis therefore investigated the influence of ice-marginal lakes on ice-margin dynamics in west Greenland at multiple spatial and temporal scales, using both established remote sensing techniques and the novel integration of time-lapse photography with Structure-from-Motion and Multi-View Stereo. A regional-decadal scale analysis of ice-margin change along a ~5000 km length of the GrIS revealed that lake-terminating ice-margins receded faster than their terrestrial counterparts between 1987 and 2015. In addition, the rate of recession at lake-terminating ice-margins accelerated over the study period and increasingly outpaced recession at terrestrial ice-margins. Altitude, latitude, lake area and the length of the lake – ice-margin interface were also identified as significant controls on rates of lake-terminating ice-margin recession. Local-seasonal scale ice-margin dynamics were investigated using the first continuous year-round volumetric record of calving at a lacustrine ice-margin. These data highlighted two distinct calving regimes; with melt-undercutting driving high calving rates under ice-free lake conditions, and force imbalances at the ice-cliff driving low calving rates when the lake was frozen. These results are important because they demonstrate that ice-marginal lakes are key regulators of ice-margin dynamics at the GrIS. The quantitative data derived through this study provide an empirical foundation upon which modelling efforts can incorporate the influence of ice-marginal processes. This is particularly pertinent given that rates of mass loss and recession at lake-terminating margins of the GrIS are likely to accelerate in coming decades in response to continued ice-marginal lake expansion and a lengthening melt season.