ABYSSAL CURRENTS AND ADVECTION OF RESUSPENDED SEDIMENT ALONG THE NORTHEASTERN BERMUDA RISE
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An integrated study using current meters, time-series nephelometers, and water samplers for measurements of particulate matter concentration revealed an intense nepheloid layer centered on the slopes of the Eastward Scarp-the northeastern boundary of the Bermuda Rise. These slopes also contained extensive furrows, truncated seismic reflectors, and Wisconsin-age and older surface sediments. The abyssal circulation in this region appears to be accelerated when it encounters the steep topography of the Eastward Scarp, eroding sediments, creating the erosional furrows, and moving eroded sediment upslope. Instruments on top of the Bermuda Rise recorded episodic events ("benthic storms") where particle concentrations at 25 m above the bottom increased from a background level of 60 g 1-1 to maximum of 251 g 1-1 and current velocities were nearly 20 cm s-1. Net transport of both water and entrained sediment was to the west-northwest. During the largest benthic storm water temperature decreased by 0.1C, consistent with a 300-600 m upslope transport of water and resuspended sediments from the upper slopes of the Eastward Scarp. When currents carry resuspended sediment over the rim of the Eastward Scarp to the plateau region, the current slows, depositing its sediment load. Thus the plateau is growing upwards slowly at the expense of the surrounding scarps. 1994.
