Numerical study of winter water formation in the Chukchi Sea : Roles and impacts of coastal polynyas

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Winter water formation is examined in the Chukchi Sea for the winters of 1992-2006 using a primitive equation ocean model forced by NCEP wind and surface salinity flux derived from SSM/I thin ice thickness estimates. The model is also forced by an external inflow of 0.8 Sv through the Bering Strait. The model successfully reproduces the oceanic circulation on the Chukchi shelf, thus providing numerous insights into behaviors of salt-enriched water produced on the shelf. The experiments show that under northeasterly winds, northward throughflow across Barrow Canyon is reduced. This results in salinity buildup under freezing conditions and ultimately in greater enhancement of salinity of the waters carried into the Arctic Basin. The flow and salinity enhancement of the flow through Herald Canyon is less extreme but more steady than through Barrow Canyon. Together with moored salinity in the Bering Strait, the model results estimate the actual salinity to be 32.9 ± 0.8 psu and 32.7 ± 0.3 psu, respectively, for waters moving through the Barrow and Herald Canyons. Both estimates are less than 33.1 psu that is typically observed for the cold halostad layer in the Canada Basin, suggesting the importance of diapycnal mixing with saltier Atlantic origin water.
2011-07-28