A six-grid, two-way coupled Mediterranean Sea and North Atlantic ocean model: results and interpretations

A multiple-grid, two-way coupled Mediterranean Sea and North Atlantic (MEDiNA) Ocean model is presented. The model uses six grids with resolution varying from 1/24$^{\circ}$ in the Strait of Gibraltar to 1/4$^{\circ}$ in the central North Atlantic Ocean. The flexible multiple-grid coupling approach produces nearly seamless flow patterns across the nested boundaries and facilitates realistic modeling of multi-scale processes that couple deep ocean and coastal dynamics. The method is efficient and provides high resolution where it is needed most. The shortcircuited Arctic Ocean is parameterized by: an artificial continental shelf along the northern and northeastern boundary; restoring to climatology at high latitudes; nudging the total longitudinal volume flow north of Iceland toward a specified value; and a specified freshwater source along the northern boundary. The open equatorial boundary condition includes a slow nudging toward a quasi-Neummann condition. Results from all six grids are shown, including the Gulf of Mexico Loop Current with big warm-core eddy shedding and realistic Gulf Stream meanders that pinch off cold/warm-core eddies. These results compare well with observation and show significant advantages of our multiple-grid approach in modeling multi-scale ocean dynamics.