Effect of the Mesoscale on Southern Ocean Water Mass Structure and Properties - Assessment Based on a Suite of Model Simulations of Varying Resolution.

The Southern Ocean is crucial in taking up excess heat and anthropogenic carbon. At the same time, it is an ocean region which is typically poorly simulated by models used for climate projections. One major source of uncertainty is the representation of the effects of ocean mesoscale processes, which are subgrid scale in current climate simulations. This project examines a suite of three simulations carried out with the same coupled climate model but varying spatial resolutions of the ocean: it consists of a coarse 1º-resolution where eddy effects are parameterized, a modest-eddying 0.25º-simulation lacking an eddy parameterization, and an actively-eddying 0.1º-simulation. Differences between the simulations are analyzed in a water mass framework, which is a "natural" approach given that water masses are inherently linked to ocean circulation and are sensitive to changes of their formation processes. The questions that will be examined are: first if the mesoscale processes in the Southern Ocean act to thin intermediate waters and second if they add zonal structure to the water masses. We will further examine the skill of the coarse resolution ocean model to reproduce these hypothesized effects of the mesoscale with a state-of-the-art parameterization.