ABSTRACT

Large areas of first-year sea ice containing disseminated loads of silt- and clay-sized materials are common off the northern coast of Alaska. Sand and coaser material is also found in this ice in the form of distinct masses of sediment-laden ice. Sediment is entrained into the sea-ice cover during fall storms when frazil, or small discs of ice in suspension, is actively forming in the supercooled water column. At this time, sea ice is unconsolidated and very mobile, making long-range ice rafting possible. Sediment-rich ice may be advected off the shelf and, upon melting, deposit material in the deep Arctic basin. The amount of sediment incorporated into the ice cover varies considerably from year to year, depending on the location and severity of storms accompanying freezeup. In 1978 the seasonal ice cover in an area off northern Alaska carried 16 times as much sediment as the total annual suspended sediment input from adjacent coastal rivers. Sea-ice sediment transport is important in the overall sediment budget in northern polar regions, particularly the transport of fine-grained material, but entrainment mechanisms are poorly understood.