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Seasonal inflow of warm water onto the southern Weddell Sea continental shelf, Antarctica
Import of warm waters onto the Antarctic continental shelf has a major influence on the heat and salt budget of the coastal ocean, and is a potential heat source for ice-shelf basal melt. Summertime observations indicate a southward flow of modified Warm Deep Water (MWDW) on the eastern side of Filchner Depression. However, the lack of wintertime observations has meant that it has not yet been possible to establish whether the inflow exhibits a significant seasonality.
This paper describes the seasonality of the flow of MWDW onto the Filchner continental shelf using data from 19 Weddell seals (Leptonychotes weddellii) tagged with miniaturized conductivity-temperature-depth sensors in February 2011. During the following eight, months the instruments yielded about 9,000 temperature-salinity profiles from a previously undersampled area. The data show a pronounced decrease in warm water inflow from summer to winter, further supported by an almost three-year long time series from a shelf-break mooring. The reduced wintertime inflow seems to be related to seasonal changes in wind forcing; stronger easterly winds during winter drives the off-shelf core of MWDW downward below the shelf break.
Intrusions of warm water and its sensitivity to winds imply that the oceanographic regime of the southern Weddell Sea is susceptible to change on a variety of timescales. The potential impact on Filchner-Ronne Ice Shelf, and on the production of water masses of global importance, indicates the need for sustained monitoring of shelf-slope exchanges in the southern Weddell Sea.
M. Arthun, K. W. Nicholls, K. Makinson, L. Boehme, M. A. Fedak
Geophysical Research Letters, doi: 10.1029/2012GL052856, 2012