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.