Ice-marginal proglacial lakes enhance outlet glacier velocities across Greenland

Ice-marginal lakes can alter glacier dynamics, typically accelerating mass loss. The number and size of lakes bordering the Greenland Ice Sheet have increased over recent decades, but their influence on the velocity of outlet glaciers remains largely unquantified. Here, we compare the longitudinal velocity profiles of 102 lake- and land-terminating glaciers across the Greenland Ice Sheet. We find that lake-terminating glaciers are 231% faster at the terminus and exhibit enhanced ice speeds up to ~3.5 km inland. Furthermore, ~44% of lake-terminating glaciers accelerate towards their termini, compared to only ~4% of land-terminating glaciers. The relationship between lake size and glacier behaviour is complex, but glaciers terminating in the largest lakes generally exhibit greater rates of down-ice acceleration than those terminating in the smallest lakes. Together, these results demonstrate that outlet glaciers respond dynamically to lakes at their termini, which should be accounted for in models of ice sheet evolution.