Effects of Subgrid-Scale Mixing Parameterizations on Simulated Distributions of Natural14C, Temperature, and Salinity in a Three-Dimensional Ocean General Circulation Model

Abstract

Abstract The effects of parameterizations of subgrid-scale mixing on simulated distributions of natural 14C, temperature, and salinity in a three-dimensional ocean general circulation model are examined. The parameterizations studied are 1) the Gent–McWilliams parameterization of lateral transport of tracers by isopycnal eddies; 2) horizontal mixing; 3) a parameterization of vertical mixing in which the amount of mixing depends on the local vertical density gradient; and 4) prescribed vertical mixing. The authors perform and analyze four ocean GCM simulations that use different combinations of these parameterizations. It is confirmed that the Gent–McWilliams parameterization largely eliminates the tendency of GFDL-based models to overestimate temperatures in the thermocline. However, in the authors’ simulations with the Gent–McWilliams parameterization the deep ocean is too cold, in places by more than 3 degrees. Our results are the first known to assess the effects of the Gent–McWilliams parameterization...