Impacts of glacial meltwater on ocean continental shelf regimes around Antarctica

As the Antarctic ice sheet melts in response to climate change, freshwater is released into the ocean over the continental shelf, altering its hydrographic properties, stratification and circulation. This can, in turn, affect melting of Antarctic ice shelves by modifying the delivery of oceanic heat to sub-ice-shelf cavities. To study the response of the ocean to enhanced Antarctic meltwater, we use an equilibrated 1° global ocean-sea ice configuration with relatively realistic continental shelf regimes. We conduct three freshwater perturbation experiments of increasing complexity covering the period 1990-2100. Our results show that meltwater injection reduces wintertime convection around Antarctica, by strengthening vertical stratification. Consequently, Dense Shelf Water (DSW) is no longer renewed while Circumpolar Deep Water (CDW) is no longer ventilated on the shelf. CDW thus permanently intrudes onto the lower part of the continental shelf, causing warming there. However, this response depends strongly on how the meltwater perturbation is implemented: warming and CDW intrusion on the shelf are largely mitigated under a realistic forcing design, in which meltwater is distributed vertically and horizontally and the latent heat of fusion is accounted for. Under this realistic forcing, shelf bottom waters warm only slightly (+0.1°C on average in 2100), whereas coastal surface injection causes strong warming (+0.7°C). Further, DSW formation proves more resilient under more realistic forcing, but ultimately ceases under all meltwater injection scenarios considered. These results indicate that models using simplified meltwater anomaly forcing likely exaggerate both continental shelf warming and DSW decline.