Pathways of basal meltwater released from Antarctic ice shelves: A model study

Monday, 15 December 2014
Kazuya Kusahara, Institute of Low Temperature Science, Sapporo, Hokkaido, Japan and Hiroyasu Hasumi, Atmosphere and Ocean Research Institute, the University of Tokyo, Kashiwa, Japan
We investigate spreading pathways of basal meltwater released from all Antarctic ice shelves using a circumpolar coupled ice shelf-sea ice-ocean model that reproduces major features of the Southern Ocean circulation, including the Antarctic Circumpolar Current (ACC). Several independent virtual tracers are used to identify detailed pathways of basal meltwaters. The spreading pathways of the meltwater tracers depend on formation sites because the meltwaters are transported by local ambient ocean circulation. Meltwaters from ice shelves in the Weddell and Amundsen--Bellingshausen Seas in surface/subsurface layers are effectively advected to lower latitudes with the ACC. Although a large portion of the basal meltwaters is present in surface and subsurface layers, a part of the basal meltwaters penetrates into the bottom layer through active dense water formation along the Antarctic coastal margins. The signals at the seafloor extend along the topography, showing a horizontal distribution similar to the observed spreading of Antarctic Bottom Water. Meltwaters originating from ice shelves in the Weddell and Ross Seas and in the Indian sector significantly contribute to the bottom signals. A series of numerical experiments in which thermodynamic interaction between the ice shelf and ocean is neglected regionally demonstrates that the basal meltwater of each ice shelf impacts sea ice and/or ocean thermohaline circulation in the Southern Ocean.