Ocean mixing versus gas-exchange in Antarctic Shelf Waters near 150°E

Keir, RS, Michel RL, Weiss RF.  1992.  Ocean mixing versus gas-exchange in Antarctic Shelf Waters near 150°E. Deep-Sea Research Part a-Oceanographic Research Papers. 39:97-119.

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atlantic, c-14, radiocarbon, rates, seawater, weddell sea


In February 1985, chlorofluoromethanes (CFMs), tritium and radiocarbon were measured in Antarctic continental shelf waters near 150-degrees-E. These distributions are used to evaluate (1) the transport of Warm Deep Water (WDW) and Antarctic Surface Water onto the shelf, and (2) the gas exchange rates across the sea surface. The time varying response of these tracers to atmospheric forcing is simulated with a box model of the water masses in this region. In the model, horizontal mixing of surface waters strongly affects the shelf radiocarbon level, but the CFMs and tritium are not affected. The observed low tritium concentrations (< 0.2 TU) in the shelf waters provide a lower limit to the transport of tritium deficient Warm Deep Water into the region, which is equivalent to a vertical flux of about 75 m y-1. This implies a maximum residence time of WDW in the basin of about 8 years. The transport of subsurface water out of the basin at the shelf break is estimated to be approximately 0.2 to 0.4 x 10(6) m3 s-1. The average annual CFM piston velocity for gas exchange is estimated to be about 200 m y-1.