FY 1979

Processes affecting the distribution and transport of suspended matter in the northeast Gulf of Alaska

Feely, R.A., E.T. Baker, J.D. Schumacher, G.J. Massoth, and W.M. Landing

Deep-Sea Res., 26(4a), 445–464, doi: 10.1016/0198-0149(79)90057-8 (1979)

The seasonal distributions of suspended particulate matter in the northeast Gulf of Alaska were studied and compared with local currents during 1975-76. East of Kayak Island, the circulation patterns were dominated by the influence of the Alaska current, which contacts the continental shelf east of Icy Bay and flows westward along the shelf edge. Suspended material from the coastal streams that drain the Bering, Guyot, and Malaspina glaciers was carried westward along the coastline and deposited in near-shore environments. Time series measurements near the shelf edge indicated that tidal and storm-induced bottom currents caused bottom sediments to be resuspended with significant onshore transport occurring during storm events. Over the region between Kayak Island, Middleton Island, and the Copper River Delta circulation responded to local forcing by wind and river discharge in nearshore waters and to the Alaska Current at the shelf edge. Two quasipermanent gyres dominated the circulation in this area. The inner gyre was cyclonic and caused suspended matter from the Copper River to be transported to the west along the coast, with part of the terrigenous material passing into Prince William Sound from either side of Hinchinbrook Island and the remainder carried to the southwest along the southern coast of Montague Island. The outer gyre was anticyclonic and in conjunction with coastal flow diverted by Kayak Island caused terrigenous material from either side of the island to be transported offshore past the edge of the outer shelf in the near-surface waters. In near-bottom waters, offshore transport of resuspended sediments appeared to be associated with downslope movement of cold, dense, near-shore water, which forms during winter and augments wind-driven downwelling. These episodic processes are expected to occur frequently if not regularly. Therefore, on geologic time scales they might represent significant mechanisms for transporting terrigenous material offshore.