Sack Lunch Seminar (SLS)

Improved Overflow Representation in Ocean Climate Models



Oceanic overflows are bottom-trapped density currents originating in semi-enclosed basins such as the Nordic seas, or on continental shelves such as the Antarctic shelf. Overflows are the source of most of the abyssal waters, and so play an important role in the large-scale ocean circulation, forming a component of the sinking branch of the thermohaline circulation. As they descend the continental slope, overflows mix vigorously with the surrounding oceanic waters, changing their density and transport significantly. These mixing processes occur on spatial scales well below the resolution of ocean climate models, with the result that deep waters and deep western boundary currents are simulated poorly. The recently completed Gravity Current Entrainment Climate Process Team was established to accelerate the development and implementation of improved representations of overflows within large-scale climate models, bringing together climate model developers with those conducting observational, numerical and laboratory process studies of overflows. Here I will describe the new overflow parameterizations which resulted from this collaboration and the impact of these new representations on the climate model simulations.