Greenland fjord processes have a depth-dependent influence on predicted submarine melt rates

Abstract. Recent ice loss from the Greenland Ice Sheet has been driven in part by the retreat of marine-terminating glaciers in response to ocean warming. Efforts to quantify ocean forcing often rely on far-field ocean properties, which differ from those adjacent to glacier termini in fjords. To quantify these differences and their significance for glacier ablation, we analyse 58 pairs of near-glacier and fjord-mouth conductivity-temperature-depth measurements from 38 fjords around Greenland collected between 2016 and 2021. Relative to fjord mouth properties, near-glacier profiles show consistent near-surface cooling, attributed to iceberg melt, and intermediate-depth warming caused by plume-driven upwelling of deeper waters. Available results from Southeast Greenland appear different, with near-glacier waters colder and fresher than fjord mouths at all depths. Our results show that while it is generally reasonable to use shelf water properties to model submarine melt at depths > 250 m (except for fjords with shallow sills), this approach will significantly overestimate melt near the surface and underestimate at mid depth, potentially influencing the predicted rate of glacier ablation.