Near-bottom suspended sediment variability caused by storms and near-inertial internal waves on the Ebro mid continental shelf (NW Mediterranean)

Abstract

Near-bottom currents and suspended sediment concentrations (SSC) recorded on the Ebro continental shelf at 60 m depth during the transition between fair and stormy weather have revealed some of the major processes controlling the sediment re-suspension and transport at mid shelf depths in this NW Mediterranean area. Storm waves were the main contributor to the transport of sediment, although they only resuspended surface sediments during extreme wave conditions ( H s >4.5 m and T s >11 s ). During the recording period, the net suspended sediment flux along the shelf was one order of magnitude higher than the net suspended sediment flux across the shelf, and the resultant transport was towards the SW and seaward. Fluctuations of the near-bottom SSC during fair weather showed a periodicity around 17 h, and were related to the occurrence of near-inertial internal waves caused by wind pulses during storm events. The energy propagation of these internal waves reached critical angles at the mid and outer shelf, which could favor the development and maintenance of the bottom nepheloid layer on the Ebro continental shelf, as well as, on other Mediterranean continental shelves.