Preprints
https://doi.org/10.5194/tc-2022-249
https://doi.org/10.5194/tc-2022-249
 
09 Jan 2023
09 Jan 2023
Status: this preprint is currently under review for the journal TC.

The evolution of future Antarctic surface melt using PISM-dEBM-simple

Julius Garbe1,2, Maria Zeitz1,2, Uta Krebs-Kanzow3, and Ricarda Winkelmann1,2 Julius Garbe et al.
  • 1Potsdam Institute for Climate Impact Research (PIK), Member of the Leibniz Association, P.O. Box 60 12 03, 14412 Potsdam, Germany
  • 2University of Potsdam, Institute of Physics and Astronomy, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany
  • 3Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany

Abstract. It is virtually certain that Antarctica's contribution to sea-level rise will increase with future warming, although competing mass balance processes hamper accurate quantification of the exact magnitudes. Today, ocean-induced melting underneath the floating ice shelves dominates mass losses, but melting at the surface will gain importance as global warming continues. Meltwater at the ice surface has crucial implications for the ice sheet's stability, as it increases the risk of hydrofracturing and ice-shelf collapse that could cause enhanced glacier outflow into the ocean. Simultaneously, positive feedbacks between the atmosphere and the ice elevation and albedo can accelerate mass losses and increase the ice sheet's sensitivity to warming. However, due to long response times it may take hundreds to thousands of years until the ice sheet fully adjusts to the environmental changes. Therefore, ice sheet model simulations must be computationally fast and capture the relevant feedbacks, including the ones at the ice–atmosphere interface.

Here we use the novel surface melt module dEBM-simple, coupled to the Parallel Ice Sheet Model (PISM), to estimate the impact of 21st-century atmospheric warming on Antarctic surface melt and long-term ice dynamics. As an enhancement compared to the widely adopted positive degree-day (PDD) scheme, dEBM-simple includes an implicit diurnal cycle and computes melt not only from the temperature, but also from the influence of solar radiation and changes in ice albedo, thus accounting for the melt–albedo feedback. We calibrate PISM-dEBM-simple to reproduce historical and present-day Antarctic surface melt rates given by the regional climate model RACMO2.3p2 and use the calibrated model to assess the range of possible future surface melt trajectories under SSP5-8.5 warming projections, extended beyond 2100 under fixed climatological conditions. Our findings reveal a substantial speed-up in ice flow associated with large-scale elevation reductions in sensitive ice-sheet regions, underscoring the critical role of self-reinforcing ice-sheet–atmosphere feedbacks on future mass losses and sea-level contribution from the Antarctic Ice Sheet on centennial to millennial timescales.

Julius Garbe et al.

Status: open (until 06 Mar 2023)

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Julius Garbe et al.

Julius Garbe et al.

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Short summary
We adopt the novel surface module dEBM-simple in the Parallel Ice Sheet Model (PISM) to investigate the impact of atmospheric warming on Antarctic surface melt and long-term ice sheet dynamics. As an enhancement compared to traditional temperature-based melt schemes, the module accounts for changes in ice surface albedo and thus the melt–albedo feedback. Our results underscore the critical role of ice–atmosphere feedbacks on the future sea-level contribution of Antarctica on long timescales.