| dc.description.abstract | Antarctic sea ice production has important implications for the global Meridional Overturning Circulation. Large volumes of sea ice are produced over the Antarctic continental shelf during the winter. In some regions the associated salt rejection creates dense Shelf Water and triggers convection to the bottom layer. Multiple outflows of Shelf Water sink down the continental slope and fill the abyssal Southern Ocean
This study generates a new sea ice thickness dataset based on the National Ice Center ice charts. Compared to previous estimates, the average thickness of the new dataset is greater than the zero ice freeboard approach, lower than a radar altimetry-based snow climatology approach, and in agreement with the GIOMAS model.
Sea ice thickness is combined with sea ice motion data to calculate sea ice production in sixteen gated sectors of the Antarctic shelf. The estimated mean sea ice production in all sixteen Antarctic shelf sectors is 2849 km^3/year. Just the two most productive areas account for 63.5% of the total: Ross (1010 km^3/year) and Southern Weddell (800 km^3/year); three areas with moderate production account for another 23.5%: Prydz , Bellingshausen, and Amundsen; and the remaining 17.5% is derived from multiple low production areas. Four sectors represent net sinks of sea ice volume: West Weddell, Marguerite, Bowman, and Adelie; but combined only reduced total mean sea ice production by 5.5%.
Salinity timeseries for each shelf sector are calculated from the estimated amount of salt rejected during sea ice production and estimates of meltwater inputs from adjacent continental ice. With a local meltwater input of 91.5 Gt/year to the Ross Sea, the sea ice production indicates a winter convective period of ~200 days; however, the addition of 518 Gt/year from upstream would shorten it to ~100 days. A hypothetical meltwater input of 700 Gt/year to the Ross Sea would be sufficient to intermittently shut down local convection. In contrast, the Southern Weddell produces Shelf Water each year despite the local meltwater input of 159 Gt/year and the 241 Gt/year from upstream. About 500 Gt/year of total meltwater input to the Weddell Sea would be required to intermittently stop convection. | |
