Relation Between the Large-Scale Atmospheric Variability and Ocean Circulation in the Nordic Seas

Abstract:

The large-scale atmospheric variability and its impact on the ocean circulation in the Nordic (Greenland, Norwegian, and Iceland) Seas are analyzed. The winter mean atmospheric circulation over the region is dominated by strong cyclonic winds. Analysis of the ocean surface wind fields over the Nordic Seas estimated from wind measurements by the NASA Quik Scatterometer (QuikSCAT) demonstrates substantial interannual variability of cyclonic wind stress. Large-scale variability in the surface winds impacts ocean circulation through several mechanisms, such as Ekman pumping and Ekman transport resulting in upwelling in the central Greenland Sea, downwelling along the coasts, generation of coastal waves, modification of coastal and open ocean currents, etc. Our particular interest is impact of the large-scale cyclonic winds on the East Greenland Current. It is speculated that besides direct impact through the northerly winds along eastern Greenland coast, cyclonic winds affect the East Greenland Current by modifying the Sverdrup balance. In this presentation, climatology and statistics of the ocean surface wind fields over the Nordic Seas derived from the NASA QuikSCAT and Cross-Calibrated Multi-Platform surface wind data (CCMP) are presented. Ocean response to the large-scale atmospheric variability is investigated from numerical experiments with the fully coupled 1/12° resolution HYbrid Coordinate Ocean Model (HYCOM) and CICE sea ice model of the Arctic Ocean. Preliminary analysis of the model data shows that maximum and minimum values of the wind-driven Sverdrup transport correlate with variations in the southward volume flux of the East Greenland Current with a one month lead. Variability of freshwater content and relation between freshwater fluxes in the East Greenland Current and the large-scale winds are furhter analyzed.