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The long-term sea-level commitment from Antarctica

par Ann Kristin, Klose;Coulon, Violaine ;Pattyn, Frank ;Winkelmann, Ricarda
Référence EGU General Assembly 2022 (23-27 May 2022: Vienna, Austria & Online)
Publication Non publié, 2022-05-26

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Résumé :

With a sea-level rise potential of 58 m sea-level equivalent, the future evolution of the Antarctic IceSheet under progressing warming is of importance for coastal communities, ecosystems and theglobal economy. Short-term projections of the sea-level contribution from Antarctica in the recentice sheet model intercomparison ISMIP6 range from a slight mass gain (-7.8 cm) to a mass loss ofup to 30.0 cm sea-level equivalent at the end of the century under Representative ConcentrationPathway 8.5 (Seroussi et al., 2020, Edwards et al., 2021). However, due to high inertia of thesystem, the ice sheet response to perturbations in its climatic boundary conditions are ratherslow. Consequences of potentially triggered unstable ice loss due to positive feedbackmechanisms may therefore play out over long timescales (on the order of millennia). Projectionsof the committed sea-level change at a given point in time, that is the sea-level change whicharises by fixing the climatic boundary conditions and letting the ice sheet evolve over severalmillennia, might differ substantially from the sea-level change expected at that point in time(Winkelmann et al., 2022).Previous assessments of the long-term contribution to sea-level rise from the Antarctic Ice Sheethave been primarily restricted to a single model and have rarely explored the full range of intraand inter-model parameter uncertainties. Here, we determine the long-term, multi-millennial sealevel contribution from mass balance changes of the Antarctic Ice Sheet by means of two ice sheetmodels, the Parallel Ice Sheet Model (PISM) and the fast Elementary Thermomechanical Ice Sheet(f.ETISh) model. More specifically, we assess the response of the Antarctic Ice Sheet to atmosphericand oceanic forcing conditions derived from state-of-the-art climate model projections availablefrom the sixth phase of the Coupled Model Intercomparison Project (CMIP6) under the SharedSocioeconomic Pathways SSP5-8.5 and SSP1-2.6 available until the year 2300. The sea-levelcommitment from the Antarctic Ice Sheet is quantified by branching off at regular intervals in timeand running the ice sheet models for several millennia under fixed climate conditions. Keyuncertainties related to ice dynamics as well as to interactions with the bed, atmosphere andocean are taken into account in an ensemble approach.