Antarctic Bottom Water sensitivity to spatio-temporal variations in Antarctic meltwater fluxes

Abstract

Ice sheet melting into the Southern Ocean can change the formation and properties of the Antarctic Bottom Water (AABW). Climate models generally mimic ice sheet melting by adding uniformly-distributed freshwater fluxes in the Southern Ocean. Uniform fluxes misrepresent the heterogeneous Antarctic ice sheet melting patterns, and could bias AABW representation in models. We use a global ocean and sea-ice model to explore whether the spatial distribution and increases in freshwater fluxes can alter AABW properties, formation, and the Antarctic sea-ice area. We find that a realistic spatially varying flux sustains AABW with higher salinities compared to simulations with uniform meltwater fluxes. Finally, we show that a ˜20% increase in ice sheet melting can trigger AABW freshening and Antarctic sea-ice expansion rates similar to those observed in the Southern Ocean since 1980, suggesting that the increasing Antarctic meltwater discharge can drive the observed AABW freshening and the Antarctic sea-ice expansion.