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Keywords:

  • Arctic;
  • Beaufort Sea;
  • eddies;
  • resuspension;
  • shelf-basin exchange;
  • upwelling/downwelling

[1] Particle fluxes over the Beaufort continental slope (70.548°N/140.045°W; 710 m) were measured at two depths (290 and 490 m) during the fall 1992 to spring 1993 period. Sequential sediment traps recorded a peak in particle flux under heavy ice cover in midwinter. The fine-grained, highly terrigenous material was consistent in composition with bottom sediments from the shelf and upper slope. The peak occurred coincident with high current speed and isopycnal displacements characteristic of cyclonic eddies, and upwelling-downwelling (UW-DW) cycles driven by winds and drifting ice. Such phenomena may be the operative mechanisms for transporting sediments from shelf to basin in the Arctic. Available evidence favors the origin of the midwinter peak to be rainout of particles from the cyclonic eddies; we suggest that the particles were earlier entrained into the eddy when it impinged upon the upper slope. Estimates show that sediment-laden water in an eddy could sustain rainout at 250 mg m−2 d−1 for ∼120 days, so that sediment could have been transported 100–500 km with the eddy before reaching our site. Current speeds generated by wind-driven UW-DW events were insufficient to resuspend sediment on the outer shelf, and the timing of strong events was unconvincing as a link to the enhanced sediment flux over the slope 50 km to the north. Bottom current must exceed 19–36 cm s−1 depending on the sediment type to resuspend material from the seabed of the Mackenzie shelf.