A13K-3324:
Towards a more consistent picture of isopycnal mixing in climate models

Monday, 15 December 2014
Anand Gnanadesikan1, Marie-Aude Sabine Pradal2, Inga Koszalka1 and Ryan P Abernathey3, (1)Johns Hopkins Univ-EPS, Baltimore, MD, United States, (2)Johns Hopkins Univ, Baltimore, MD, United States, (3)Columbia University of New York, Palisades, NY, United States
Abstract:
The stirring of tracers by mesoscale eddies along isopycnal surfaces is often represented in coarse-resolution models by the Redi diffusion parameter ARedi. Theoretical treatments of ARedi often assume it should scale as the eddy energy or the growth rate of mesoscale eddies,. producing a picture where it is high in boundary currents and low )of order a few hundred m2/s) in the gyre interiors. However, observational estimates suggest that ARedi should be very large (of order thousands of m2/s) in the gyre interior. We present results of recent simulations comparing a range of spatially constant values ARedi (with values of 400, 800, 1200 and 2400 m2/s) to a spatially resolved estimate based on altimetry and a zonally averaged version of the same estimate. In general, increasing the ARedi coefficient destratifies and warms the high latitudes. Relative to our control simulation, the spatially dependent coefficient is lower in the Southern Ocean, but high in the North Pacific, and so the temperature changes mirror this. We also examine the response of ocean hypoxia to these changes. In general, the zonally averaged version of the altimetry-based estimate of ARedi does not capture the full 2d representation.