Bulldozing and resuspension of shallow-shelf sediment by ice keels: Implications for Arctic sediment transport trajectories

Abstract

The orientations and termination directions of newly formed ice gouges, identified in a 5-year study of two offshore corridors in eastern Harrison Bay, Alasaka, indicate a bimodal distribution of sediment transport directions: west-southwest and southeast, due to ice-keel bulldozing. The westerly sediment transport results from the dominant westward drift of sea ice and ocean currents, whereas the southeasterly transport results from episodic fall storms with winds from the northwest. Transport associated with ice gouging occurs by bulldozing and by resuspension during the bulldozing processes. Fine-grained (< 63 μm) sediment transport may also involve transport of resuspended sediment by intensified currents found near the grounded floes, leaving behind a lag of coarser sediments. In Harrison Bay, about 6000 m 3 of sediment is reworked each year by ice gouging for every square kilometer of the seafloor between water depths of 5 and 18 m. Over 50% of this sediment is moved onshore to the southeast, whereas 35% is moved alongshore to the west. The actual distance of sediment transport is dependent upon the grain size of the seafloor sediment. Coarse-grained material (> 63 μm) is bulldozed as far as 7 m in the direction of ice movement, whereas sediment finer than 63 μm may be transported by intensified bottom currents up to 80 times this distance.