Distinct Frontal Ablation Processes Drive Heterogeneous Submarine Terminus Morphology

Abstract

Calving and submarine melt drive frontal ablation and sculpt the ice face of marine-terminating glaciers. However, there are sparse observations of submarine termini, which limit estimates of spatially varying submarine melt. Here we present a detailed survey of a west Greenland glacier to reveal heterogeneity in submarine terminus morphology. We find that the majority of the terminus (~77%) is undercut, driven by calving in the upper water column and submarine melting at depth. The remaining ~23% of the terminus is overcut, driven by calving alone. We use observations of six subglacial discharge outlets, combined with a plume model, to estimate spatially varying discharge fluxes. While small discharge fluxes (<43 m3/s) feed numerous, deeply undercut outlets with subsurface plumes, ~70% of the net subglacial flux emerges at the terminus center, producing a vigorous, surface-reaching plume. This primary outlet drives large, localized seasonal retreat that exceeds calving rates at secondary outlets.