Modelling processes influencing shelf edge currents, mixing, across shelf exchange, and sediment movement at the shelf edge

Abstract

Abstract A brief overview, with references to the literature for detail, of a range of physical processes which influence both along and across shelf-edge currents and mixing is presented and illustrated by results from a range of numerical models. The importance of internal tides generated both at the shelf edge and at offshore topographic features in producing local mixing is considered. The influence of shelf edge topography off the west coast of Britain and wind direction upon along shelf flow and its ‘leakage’ onto the shelf is examined. In parallel with how oceanic processes can penetrate onto the shelf, the conditions leading to the interaction of a near shore river plume with a shelf edge flow are investigated. Idealised calculations show that shelf width and location of shelf edge flow can significantly influence the generation of shelf waves and unstable eddies in the shelf edge region. The decomposition of the flow field using an Empirical Orthogonal Function approach is found to be a convenient means of understanding the contribution of both shelf waves and unstable modes. Cross shelf mixing and exchange is examined using both point models, and cross shelf models. Calculations show the limitations of a single point model and the importance of the coastline in determining cross shelf circulation. The cross shelf model is also used to examine the distribution of suspended sediment under upwelling and downwelling favourable wind conditions.