Observing an immediate ice stream response to calving with terrestrial radar interferometry at Sermeq Kujalleq in Kangia, Greenland

Sermeq Kujalleq in Kangia (hereafter SKK, also known as Jakobshavn Isbræ), Greenland, is among the most extensively studied glaciers worldwide, mainly due to its recent retreat associated with fast flow and high ice discharge. However, substantial gaps remain in understanding its short-term ice dynamics, as glacier responses to abrupt changes occurring within hours to minutes require high-rate field measurements that are challenging to acquire. Here, we present high-resolution terrestrial radar observations revealing a stepwise acceleration of SKK ice stream immediately following a large calving event. This response was observed up to 10 km from the glacier terminus, representing one of the longest immediate calving responses reported in Greenland to date. Additionally, we detected large instantaneous deformations in the highly crevassed shear margins, further supporting the notion of a strong lateral and longitudinal coupling of the ice stream. Using a simplified theoretical framework, we present the loss of lateral drag due to calving as a key component in the genesis of such a widespread calving response.