Abstract
Eventually, about 85% of the anthropogenic carbon dioxide emitted to the atmosphere will dissolve in the ocean (e.g., Sarmiento et al., 1992), but the rate at which this happens is limited by the rate at which deep waters are exposed to the surface. The Southern Ocean is of special importance in this respect, accounting for about 40% of the total oceanic uptake (e.g., Watson et al., 2003). We will present the results of a time- dependent trajectory algorithm used to trace the sources of the Antarctic Bottom Water, Antarctic Intermediate Water and Subantarctic Mode Water produced in the modeled Southern Ocean. The trajectory algorithm also allows us to diagnose the sources of the deep water that upwells in the Southern Ocean in the different IPCC AR4 coupled climate models simulations of the 20th century. The biogeochemically significant source waters of the Southern Ocean upwelling and water mass formation regions are critically sensitive to the simulated (and evolving) climate, and these sources and sensitivities are revealed by this technique. We will quantify the rates of Southern Ocean ventilation associated with different circulations and compare them with observations, and discuss why these rates differ so greatly between models.
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