Transport of ice shelf basal meltwater around Antarctica

Ice streams flowing from the Antarctic continent come in contact with the ocean where they cross the grounding line and begin to float as ice shelves. Oceanic melting of the base of these ice shelves is now thought to be the most significant cause of mass loss for the Antarctic ice sheet. The flux of basal meltwater out from under the ice shelves has been proposed to impact important processes such as Antarctic Bottom Water formation, Southern Ocean sea ice extent, and the delivery of a significant fraction of the limiting micro-nutrient dissolved iron to the euphotic zone in the extremely productive coastal Antarctic waters.

We study generation of and subsequent pathways for basal meltwater with a circum-Antarctic ocean/sea-ice/ice shelf ROMS model. The model was initially run with 10 km horizontal grid spacing, but reducing this to 5 km increases the total ice shelf melt by ~20% and improves the simulation of basal melt in several locations, especially "warm-water" shelves in the Amundsen and Bellingshausen Seas. Eight independent simulated tracers are used to examine regional differences in the spread of meltwater. Separate tracer release simulations were performed to study seasonal changes in meltwater fluxes. The results confirm the previously reported idea that transport of meltwater from the Amundsen ice shelves to the Ross Sea is significant, and there are several other locations on the Antarctic continental shelf where most of the ice shelf water is not of local origin. Meltwater from ice shelves in the Amundsen and Bellingshausen Seas is readily transported into the wider Southern Ocean due to the proximity of the Antarctic Circumpolar Current to the continental shelf. There is strong seasonal variability in the production of meltwater and the consequences of this on the subsequent lateral and vertical dispersion, including supply to the euphotic zone during the growth season, are described.