George Halliwell, Linda Smith, Zulema Garraffo, Xiaobiao Xu, and Eric Chassignet, RSMAS
The Price-Yang (PY) Mediterranean overflow model is implemented in the HYbrid Coordinate Ocean Model (HYCOM) to provide boundary conditions in the Gulf of Cadiz that inject Mediterranean overflow water into the interior North Atlantic in coarse resolution simulations. HYCOM provides the required upper-ocean temperature and salinity profile of the adjacent Atlantic, and then the PY model determines the temperature, salinity, density, central depth, and zonal transport of the injected water. PY model parameters characterize the topographic structure of the Straits of Gibraltar and the adjacent coastal region, and also include the integrated surface heat and mass flux over the Mediterranean Sea. In HYCOM, the PY model injects the overflow water into the two isopycnic layers with target densities that bracket the density of the overflow water using a procedure that preserves these target densities. The PY boundary condition performs similarly in two-degree and 1/3-degree Atlantic basin simulations, but differences in advection/diffusion cause relatively more northward spreading of the high salinity water in the low-resolution run and relatively more westward spreading in the eddy-admitting run. Some PY parameters had to be modified to improve the realism of injected overflow water properties compared to climatology. PY model performance compares favorably to climatological relaxation while the latter two mixing schemes have a tendency for the overflow water to penetrate too deep.