Simulation of the interannual and seasonal variability of the overflow transport through the Denmark Strait

The character of the water exchange in the Denmark Strait for the period of 1958-2006 is studied based on the results of the numerical experiments using the model of the ocean circulation developed at the Institute of Numerical Mathematics of the Russian Academy of Sciences with a resolution of 0.25 degrees in latitude and longitude with 27 vertical levels. The calculations were performed for the North Atlantic area from 30A degrees S, including the Arctic Ocean and the Bering Sea. The width of the Denmark Strait at 66A degrees N is about 650 km, and the depth is approximately 550 m. The fields of the temperature, salinity, and density and the components of the current velocities were simulated. In this period, the average overflow of dense waters with the conventional potential density sigma(0) > 27.80 to the North Atlantic through the Denmark Strait was 1.86 +/- 0.96 Sv, and, for the nearbottom and intermediate waters with sigma(0) > 27.50, it was 3.84 +/- 1.31 Sv. The maximum values of the overflow transport through the strait were recorded in 1962, 1972, 1983, 1990, and 2000. Exactly these years showed the highest values of the North Atlantic oscillation (NAO) index. This fact confirms the domination of the decadal variability of the hydrogeological processes in the North Atlantic. The model section of the current velocity through the strait showed the occurrence of at least four well marked jets that vertically occupy the entire sectional area from the surface to the bottom. The two jets divided by a northward jet at the strait's middle move southward along the Greenland slope. The northward current along Iceland is also identified. This structure of the currents is also supported by the analysis of the observed variability of the absolute topography of the ocean's surface.