The role of driving forces in sediment transport processes in an upwelling-driven continental shelf

Abstract

Sediment transport in the continental shelf regions affects many interdisciplinary problems, including ecological and social issues. Understanding the underlying processes influencing sediment transport is essential for coastal management, distribution of nutrients, pollutants and abundance of benthic flora and fauna, which can impact the entire food chain in the marine ecosystem. The present work aims to enhance our understanding of the spatial and temporal variability of sediment transport in the upwelling affected continental shelves. A state-of-the-art 3D oceanic numerical model CROCO (v1.0) was used to simulate the suspended sediment transport on NW Iberian Peninsula continental shelf, considering an entire annual cycle from November 2008 to December 2009. The sediment transport patterns were influenced by the seasonality of the shelf current and wave dynamics. While low sediment movement was observed during spring and summer, considerable transport could be seen from mid-autumn and winter, associated with storms. The shelf circulation, mainly driven in response to atmospheric forcing, determined the transport direction, while wave energy regulated the re-suspended sediment mass. Storm-driven upwelling and downwelling events predominantly promoted sediment transport southward and northward through the bottom boundary layer, respectively. The morphological features of the shelf and the frontal dynamics between the oceanic and fresh water in the mid-and inner shelf, modulated by upwelling and downwelling, shaped the suspended sediment transport across and along the water column. In the northern region of the study area, the simulated shelf-scale near-bottom eddies induced transport pathways to the open ocean.