The dependence of the ocean's MOC on mesoscale eddy diffusivities: A model study

- Mesoscale eddies modulate the strength of global overturning cells in ocean models.
- The strength and depth of the Atlantic Meridional Overturning Circulation (AMOC) cell co-vary.
- The AMOC is sensitive to the representation of eddies in the Southern Ocean.

The dependence of the depth and strength of the ocean's global meridional overturning cells (MOC) on the specification of mesoscale eddy diffusivity (K) is explored in two ocean models. The GISS and MIT ocean models are driven by the same prescribed forcing fields, configured in similar ways, spun up to equilibrium for a range of K's and the resulting MOCs mapped and documented. Scaling laws implicit in modern theories of the MOC are used to rationalize the results. In all calculations the K used in the computation of eddy-induced circulation and that used in the representation of eddy stirring along neutral surfaces, is set to the same value but is changed across experiments. We are able to connect changes in the strength and depth of the Atlantic MOC, the southern ocean upwelling MOC, and the deep cell emanating from Antarctica, to changes in K.