Ice shelf basal melt rate estimation in a Lagrangian framework

We present a dense record of glacier ice dynamics and ice melt rate at the boundary between grounded ice and ocean - or grounding line - of Petermann Glacier, a major outlet glacier in Northwest Greenland. The traditional view of grounding lines implemented in physical models in charge of projecting sea level rise is a fixed grounding line with zero ice melt. Instead, the satellite record reveals kilometer-size grounding line migrations - or grounding zones - during tidal cycles, with preferential intrusions of 6 km along pre-existing subglacial channels. The highest melt rates of ice are recorded within the grounding zone. Kilometer-wide grounding zone with vigorous ice-ocean interaction will make projections of sea level rise from glaciers potentially double.