Ice rafting of fine-grained sediment, a sorting and transport mechanism, Beaufort Sea, Alaska.

The presence of turbid, sediment-rich fast ice in the Arctic is a major factor affecting transport of fine-grained sediment. Observers have documented the widespread, sporadic occurrence of sediment- rich fast ice in both the Beaufort and Bering Seas. The occurrence of sediment in only the upper part of the seasonal fast ice indicates that sediment-rich ice forms early during ice growth. The most likely mechanism requires resuspension of nearshore bottom sediment during storms, accompanied by formation of frazil ice and subsequent lateral advection before the fast ice is stabilized. We estimate that the sediment incorporated in the Beaufort ice canopy formed a significant proportion of the seasonal influx of terrigenous fine-grained sediment. The dominance of fine-grained sediment suggests that in the Arctic and sub-Arctic these size fractions may be ice rafted in greater volumes than the coarse fraction of traditionally recognized ice-rafted sediment. -from Authors