Seasonal variations of outlet glacier terminus position in Greenland

Many of Greenland's marine-terminating outlet glaciers have undergone rapid retreat in the past decade, accompanied by accelerated flow and dynamic thinning. Superimposed on this pattern of retreat, these glaciers undergo seasonal variations in terminus position, corresponding roughly to wintertime advance and summertime retreat. We compiled near-daily time series of terminus position for five of Greenland's largest outlet glaciers (Daugaard Jensen, Kangerdlugssuaq and Helheim glaciers in East Greenland, and Jakobshavn Isbrae and Rink Isbrae in West Greenland) using Moderate Resolution Imaging Spectroradiometer (MOD IS) satellite imagery. There are spatial differences in the timing of the onset of seasonal retreat among all the glaciers in our study, as well as variability in terminus behavior for individual glaciers from year to year. We examine whether this spatial and temporal variability is linked to above-freezing air temperatures or high sea surface temperatures, but find no simple relationship. Instead, we hypothesize that terminus geometry (ice thickness, subglacial topography, fjord bathymetry) exerts an important control on the response of marine-terminating glaciers to climate perturbations. Models for predicting outlet glacier response to climate change need to include this complex interaction between geometry and environmental forcing.