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Abstract:
The increasing amount of fresh water entering the Southern Ocean due to mass loss from the Antarctic ice sheet and ice shelves loss has been proposed as a mechanism responsible for the lack of decline in Antarctic sea ice area, in contrast to the sea-ice loss seen in the Arctic. Though increased Antarctic ice-mass loss is expected to impact climate it is absent from almost all current coupled climate models, which typically enforce that the continent remain in perpetual mass balance. Further, previous model experiments suggest that the climate response to Antarctic mass loss depends on the model used, and that the reasons for this model dependence are not clear. We use the HadGEM3-GC3.1 model to contribute model experiments to the Southern Ocean Freshwater release model experiments Initiative (SOFIA), an international model intercomparison, in which freshwater is added to the ocean surrounding Antarctica to simulate the otherwise missing ice-sheet mass loss. This unique suite of models will allow us to evaluate HadGEM3-GC3.1, identify reasons for model discrepancies, and quantify the potential impact of the absence of increasing Antarctic ice-mass loss on Antarctic sea ice and climate. We will give an overview of the SOFIA project and present preliminary results from the “antwater” experiment outlined in the SOFIA protocol in which a constant freshwater input of 0.1 Sv is distributed evenly around Antarctica at the ocean surface under pre-industrial forcing. We will show the response of Antarctic sea ice and the local and global climate to this freshwater forcing.
