Introduction . Most of the discharge of ice into the oceans takes place by solid ice flow via ice streams1 , 2. These are river-like zones where ice flow is significantly faster than in their surroundings, assumed to be triggered by either bedrock properties3 , 4, enhanced sliding2 , 5, and/or by deformation mechanisms leading to shear localization6. The most conspicuous one in Greenland is the Northeast Greenland Ice Stream (NEGIS; Fig.? 1a ), which exten...