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

Near-bottom currents and suspended sediment concentrations (SSC) recorded o n the Ebro continental shelf at 60 m depth during the transition between fa ir and stormy weather have revealed some of the major processes controlling the sediment resuspension and transport at mid shelf depths in this NW Med iterranean area. Storm waves were the main contributor to the transport of sediment, although they only resuspended surface sediments during extreme w ave conditions (H-s > 4.5 m and T-s > 11 s). During the recording period, t he net suspended sediment flux along the shelf was one order of magnitude h igher than the net suspended sediment flux across the shelf, and the result ant transport was towards the SW and seaward. Fluctuations of the near-bott om SSC during fair weather showed a periodicity around 17 h, and were relat ed 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 developm ent and maintenance of the bottom nepheloid layer on the Ebro continental s helf, as well as, on other Mediterranean continental shelves. (C) 2001 Else vier Science B.V. All rights reserved.