Immediate Ice Stream and Shear Margin Response to Calving at Sermeq Kujalleq in Kangia, Greenland

Abstract

The sensitivity of Greenland outlet glaciers to short-term flow disturbances lacks observations to be well constrained in numerical models. Specifically, sudden gigaton-scale calving events regularly occurring at major Greenland outlet glaciers like Sermeq Kujalleq in Kangia (SKK; also known as Jakobshavn Isbræ) are known to perturb background ice flow in complex ways. Here, we present high-rate terrestrial radar observations and show an immediate step-wise acceleration of SKK ice stream up to 11 km from its terminus, one of the longest immediate calving responses so far reported in Greenland. Focusing on SKK's shear margins, we detected large instantaneous increases in deformation rates in its most crevassed section, which, together with the along-flow response, provide evidence for strong lateral and longitudinal coupling of the ice stream. Using a simplified theoretical framework, we show that the loss of lateral drag due to calving is a key component of such a widespread calving response.