Deep slope currents and suspended particle fluxes in and around the Foix submarine canyon (NW Mediterranean)

Deep slope currents and particulate matter concentrations were studied on t he Barcelona continental margin in and around the Foix submarine canyon fro m May 1993 to April 1994. This year-long moored experiment revealed that ne ar-bottom slope currents are strongly influenced by the bottom topography, being oriented along isobaths and along the canyon axis. The deep slope cur rent fluctuations are controlled by the local inertial motion(18.3 h) and a lso by low-frequency oscillations at periods of 6-10 days, related to the p assage of atmospheric pressure cells. Particulate matter concentrations rec orded during the experiment do not show a clear seasonal variability, excep t outside the canyon, where significant peaks of particulate matter concent rations were recorded only during the winter-fall deployment. In addition, the temporal evolution of suspended particulate matter concentration is not linked to changes in the cross-slope or along-slope current components and did not show a clear relationship with river avenues or wave storm events. This suggests that suspended particulate matter exported from the shelf is dispersed on the slope by advective processes, which attenuate the signal of the shelf-slope sediment transfer. Mean particulate matter concentration s differed among sampling sites, but the magnitude of the mean horizontal s uspended particle flux reflects a quite similar value in the whole study ar ea, ranging from 2.53 to 4.05 mg m(-2) s(-1). These horizontal suspended pa rticle fluxes are 27 (canyon head) to 360 (open slope) times higher than th e settling particle fluxes measured at the same sampling sites, indicating that the suspended particulate transport on the Barcelona continental slope dominates over the settling particle fluxes, even inside the Foix submarin e canyon. (C) 2000 Elsevier Science Ltd. All rights reserved.