Shortwave Penetration Drive Subsurface Warming and Melt on Langhovde Glacier, East Antarctica

Surface meltwater on ice shelves, together with runoff from upstream grounded ice, can pond and drain into crevasses, raising water pressure and promoting hydrofracturing. However, the timing of meltwater storage and release in coastal ablation and blue ice areas remains poorly constrained because continuous subsurface temperature records are scarce. Here we present one year of subsurface ice-temperature measurements from the blue ice area on Langhovde Glacier in coastal East Antarctica from January 2024 to January 2025, revealing persistent internal warming and a vertical temperature structure consistent with absorption of shortwave below the surface. We combine our observations with a coupled surface energy balance and firn model to isolate the effect of shortwave penetration into the surface. Simulations without subsurface shortwave absorption fail to reproduce the observed warming and its seasonal persistence, whereas including shortwave penetration substantially improves the simulated vertical temperature profile and supports an interpretation involving subsurface melt and refreezing. Observed near-surface ice temperature was ~3 °C higher than that model output. At 10 m depth, ice temperature was ~−6 °C, about 4 °C warmer than the site’s mean air temperature. These results indicate that shortwave driven subsurface heat storage is likely a key control on near surface thermal conditions in Antarctic blue ice area and may influence the seasonal opening and closure of meltwater pathways, thereby affecting the timing of runoff discharge to downstream ice shelves.