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Abstract:
Potential future impacts on sea ice and other climate variables from changing freshwater outflow from the Antarctic ice sheets and ice shelves were examined in this study. Fully-coupled model experiments were run using ramped freshwater, including latent heat effects, under historical and RCP8.5 greenhouse gas forcings. Specifically, three climate model scenarios in CCSM4.0 for 1980-2100 (FWIncr, FWConst, FWOff) and one idealized experiment for 1850-1950 (FWIncrHist) were run and compared with a control. We chose to run from base years of 1850 for pre-industrial conditions and 1980 for a year we assumed the Antarctic ice sheet was in mass balance. We then increased freshwater fluxes to give the approximate equivalent of 3 m of sea level rise over a 150 year period. For FWIncrHist, sea ice area continued to increase over the 100 year period. For FWIncr, sea ice area increased for approximately 78 years, when it began to decrease. Two shorter branched runs (FWConst, and FWOff) were carried out to test the persistence of the effects, one where the additional fresh water and latent heat effects were switched off and the other where the freshwater was held constant at the point where sea ice area behaviour “turned around”. This was to separate out the effects of greenhouse gas forcing on the ramped freshwater and latent heat effects over long time periods. The persistence of the effects on sea ice area were relatively short, with a return to control conditions in less than a decade when freshwater was switched off.
