Investigating the Use of Landsat-derived Sea Surface Temperatures As a Proxy for Changes in Ocean Forcing of Greenland’s Marine-Terminating Outlet Glaciers

Abstract The retreat and acceleration of Greenland’s marine-terminating glaciers are linked to enhanced submarine melting driven by ocean warming. Despite the significance of these ice-ocean interactions, observations of ice-front proximal waters remain limited due to logistical challenges. Buoyant subglacial meltwater plumes entrain deep, warm Atlantic waters during their ascent. Using a plume model, we demonstrate that when these plumes reach the surface in deep fjords (>400 m), their surface temperatures can serve as a proxy for subsurface ocean temperature variability. Here, we optimise and validate a Landsat sea surface temperature algorithm for Arctic waters using in situ measurements, with an accuracy of ∼0.4°C for Landsat 5, 7, 8 and 9. Applying this method, we analyse plume surface temperatures at Sermeq Kujalleq (Store Glacier) from 1985 to 2024 and compare Landsat-derived plume surface temperatures with plume model simulations forced by in situ measurements and four ocean reanalysis products. The Landsat-derived plume surface temperatures are of the correct magnitude and reveal trends consistent with expected interannual ocean variability. While large seasonal variability and confounding physical processes still make it difficult to isolate the subsurface signal, our 40 year record suggests that plume surface temperatures could become a useful proxy for subsurface ocean change.