Locally Modified Winds Regulate Circulation in a Semi-Enclosed Shelf Sea

Abstract

Wind driven circulation in the North Sea is revisited with a specific focus on locally modified winds and their impacts. We show for the first time that local extrema of the wind stress curl (WSC), generated by orography and ocean-atmosphere interactions, help regulate circulation in the northern North Sea. While calculated transports are strongly coupled with wind stress, which itself is driven by large-scale forcing, transports through the Norwegian Trench have higher correlations with the WSC field due to local extrema. Such WSC extrema regulate the eddy activity around the Norwegian Trench. We conclude that orography and ocean-atmosphere interaction are two important mechanisms contributing to the generation of the WSC extrema around the Norwegian coast. Ocean-atmosphere interaction is considered a potential mechanism developing the WSC extrema. Our results show that local winds are more important than previously documented, with important implications for regional circulation likely to result from future changes to local surface gradients, such as may arise from changing meteorological or hydro-climatic forcing. These are additional impacts on North Sea circulation that may not be accounted for from changes in wind stress alone.