Project: Southern Ocean Climate Process and Modeling Team

from www.us-ocb.org

Climate models are not systematically evaluated against the circulation of the Southern Ocean. This has resulted in IPCC models exhibiting huge ranges in quantities such as the transport of the Antarctic Circumpolar Current (ACC ~0 to 350 Sv; 1 Sverdrup = 106 m3 s-1) and the rate at which dense waters are transformed to light waters within the Southern Ocean (0 to16 Sv). Unfortunately, published observations of such quantities differ widely as well, making it difficult for modeling groups to know what to aim for in terms of reasonable circulation. This is worrisome because the Southern Ocean is the primary sink for anthropogenic carbon dioxide and plays a central role in the long-term control of the "natural" carbon dioxide content of the atmosphere, with Southern Ocean water mass transformation, which brings old deep water into the upper ocean, playing a disproportionate role in both of these as well as on the magnitude of global biological production. The goal of this Climate Process Team is to evaluate the impact of biases of Southern Ocean circulation on the carbon cycle and to understand the causes for the biases. This will involve: 1. developing and analyzing a wide suite of diagnostics of Southern Ocean circulation to come up with the best possible climatology for the circulation; and 2. evaluating the relative impacts of winds, buoyancy forcing, mixing, and physical and biogeochemical model formulation on those aspects of Southern Ocean ventilation and biogeochemistry most important for the carbon cycle. This will require a combination of theoretical studies and model sensitivity studies.