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

Abstract

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.

Subglacial discharge accelerates future retreat of Denman and Scott Glaciers, East Antarctica

“…The magnitude and localized spatial distribution of the parameterized discharge melt rate enhancements are consistent with three-dimensional ocean modeling studies of the Getz (28), Pine Island (29), and Totten (30) ice shelves. For the Totten Ice Shelf, a system also located in the Aurora Subglacial Basin of East Antarctica, the formation of buoyant plumes sourced from subglacial discharge enhances near-grounding zone melt by up to 40% (30). These findings agree with the results presented here despite the highly simplified nature of the melt parameterization relative to a three-dimensional ocean circulation model.…”

“…Overall, the simulations presented here provide evidence that a complex subglacial freshwater system underlying the Denman and Scott Glacier catchments can accelerate the onset of their future retreat into the deepest continental trench on Earth. Beyond Denman Glacier, recent modeling and observational studies have inferred the presence of dynamic water systems underlying some of Antarctica's most rapidly melting glaciers [e.g., Thwaites Glacier (25), Pine Island Glacier (29), and Totten Glacier (30)]. These glaciers drain extensive subglacial basins that hold a combined sea level potential of ~5 m in ice above floatation (17) and are vulnerable to future collapse via the Marine Ice Sheet Instability (39)(40)(41).…”

“…The exponent scaling the subglacial discharge flux (q sg ) has been the focus of recent literature (22) and was found to underestimate melt rates on vertical ice cliffs in the presence of ocean stratification. However, we are focused on simulating melt rates at the near-horizontal bases of Antarctic ice shelves, where the one-third exponent has been found (22,30) to provide reasonable results under a variety of ocean and discharge forcing conditions. The melt formulation above is valid over the domain where the buoyancy from subglacial discharge dominates that from melting.…”

“…As this trench is located along Denman Glacier's ice stream, we hypothesize that this topographic setting is optimal to channelize the subglacial water system close to the grounding line, which outflows into the sub-ice shelf ocean cavity and locally enhances basal melt rates. This process has been extensively studied in application to Arctic glaciers (20)(21)(22)(23)(24); however, its application to Antarctic glaciers is limited to indirect inference (25)(26)(27) and the correspondence of locations of modeled subglacial discharge and basal melt maxima (28)(29)(30) because of inaccessibility of Antarctic grounding lines and sub-ice shelf ocean cavities. The potential of this melt enhancement process to be a prominent forcing mechanism of future retreat of Antarctic outlet glaciers has yet to be assessed in a realistic numerical ice sheet modeling framework and thus represents a major knowledge gap in modern-day glaciology.…”

The Non‐Local Impacts of Antarctic Subglacial Runoff

“…The inclusion of subglacial runoff in a three-dimensional ocean model of ice-ocean interaction is relatively new; only a handful of studies have done so (e.g., Cowton et al, 2016;Gwyther et al, 2023;Nakayama et al, 2021;Slater et al, 2015). Thus we consider the assumptions and potential limitations in our approach.…”