Sediment resuspension over a continental shelf during Hurricanes Edouard and Hortense

The present comprehensive physical and optical measurements have captured sediment resuspension associated with two hurricanes, Edouard and Hortense, that passed over the Coastal Mixing and Optics study site in the fall of 1996. Sediment resuspension associated with Hurricane Edouard was forced by combined current and wave processes. Combined current-wave bottom shear stresses exceeded 3.5 dyn cm, well above the shear stress for the observed resuspension, which was determined to be 0.8 dyn cm. Hortense sediment resuspension, however, was caused primarily by waves with little or no contribution from subtidal plus tidal currents; combined current-wave bottom shear stress reached 2 dyn cm. Beam attenuation data reveal that bottom sediments were resuspended from ;70 m depth to more than 30 m up into the water column during both hurricanes. The relaxation of sediments to pre-Edouard conditions occurred at about the same time at all depths, indicating advection and transport by subtidal currents. Analyses of optical data reveal that the resuspended sediments consisted mainly of detritus and relict pigments from the ocean bottom.