Journal Article

Subglacial Freshwater Drainage Increases Simulated Basal Melt of the Totten Ice Shelf

Gourmelen, Noel, Gwyther, David E., Dow, Christine F., Jendersie, Stefan, Galton‐Fenzi, Benjamin K.

2023

Overview

Subglacial freshwater discharge from beneath Antarctic glaciers likely has a strong impact on ice shelf basal melting. However, the difficulty in directly observing subglacial flow highlights the importance of modeling these processes. We use an ocean model of the Totten Ice Shelf cavity into which we inject subglacial discharge derived from a hydrology model applied to Aurora Subglacial Basin. Our results show (a) discharge increases melting in the vicinity of the outflow region, which correlates with features observed in surface elevation maps and satellite‐derived melt maps, with implications for ice shelf stability; (b) the change in melting is driven by the formation of a buoyant plume rather than the addition of heat; and (c) the buoyant plume originating from subglacial discharge‐driven melting is far‐reaching. Basal melting induced by subglacial hydrology is thus important for ice shelf stability, but is absent from almost all ice‐ocean models. Plain Language Summary Grounding line subglacial discharge is the outflow of freshwater at the region where Antarctic ice shelves begin to float. This process is difficult to observe as the outflow region is typically below ice up to several kilometers thick. Using a computer model, we show how the outflow of this fresh water melts the underside of an Antarctic ice shelf. We demonstrate that the outflow leads to a strong increase in melting, which is driven not by the heat in the outflow, but rather by the low salinity water's buoyancy. This buoyancy leads to the formation of a plume that rapidly ascends the underside of the ice shelf and can carry even warmer water to the ice, leading to increased melting. Given that melting of ice shelves can destabilize the grounded ice upstream of the floating region, we show that the relationship between subglacial discharge and ice shelf melt is important for understanding the stability of Antarctic ice. Key Points Subglacial discharge has a strong local effect on melting beneath the Totten Ice Shelf Addition of buoyancy explains the change in melting Discharge has far‐reaching impacts due to the extent of the buoyant plume

• Publisher: John Wiley & Sons, Inc,Wiley
• Subject: Antarctic glaciers / Antarctic ice / Antarctic ice shelves / Antarctica / basal melting / Buoyancy / Discharge / Fresh water / Freshwater / Glaciers / Glaciohydrology / Hydrologic models / Hydrology / Ice / Ice shelves / Inland water environment / Land ice / Melting / Modelling / Ocean models / Oceans / Outflow / Salinity / sea level rise / Stability / subglacial discharge / Totten ice shelf