Dense water production and downslope flow off Cape Darnley, Antarctica, reproduced by a realistic numerical model

Abstract:

The ability of the Massachusetts Institute of Technology general circulation model (MITgcm) to reproduce dense water production in Antarctica and its downslope outflow through a complex topography is evaluated through a series of simulations at different horizontal and vertical resolutions. The study domain is the region off Cape Darnley in East Antarctica, where intense sea ice production from March to October leads to the formation of Dense Shelf Water, previously observed to outflow periodically as a downslope current. Our experiments are based on a hydrostatic parameterization, using a coupled ocean-ice-atmosphere model for realistic forcing and sea ice production. Different vertical and horizontal resolutions are used to evaluate the relative importance of the model vertical grid and of the topography on the production of dense water and its outflow, and the model output is compared with mooring observation data for evaluation purposes. Increasing the horizontal resolution leads to a start of the outflow and a periodicity more consistent with the observations, whereas variations of the vertical resolution leads to no evident improvement. Runs at high horizontal resolution yield very satisfactory results, suggesting that a horizontal resolution of 2km is sufficient to reproduce the main characteristics of the DSW and its downslope flow. However, a resolution of 1km is needed to reproduce the finest details of the flow.