Summertime sediment storage on the Alaskan Beaufort Shelf and implications for ice-sediment rafting and shelf erosion

Emily Eidam

Arctic coastlines are known to be rapidly eroding, but the fate of this material in the coastal ocean (and the sedimentary dynamics of Arctic continental shelves in general) is less well-constrained. This study used summertime mooring data from the Alaskan Beaufort Shelf to study sediment-transport patterns which are dominated by waves and wind-driven currents. Easterly wind events account for most of the seasonal sediment transport, and serve to focus sediment on the inner shelf. This is a key finding because it means sediment is readily available for wave-driven resuspension and sea-ice entrainment during fall storms. Sediment-ice entrainment has been previously implicated as a major mechanism for Arctic Shelf erosion--and so the summertime focusing of sediment observed in this study may actually serve to enhance shelf erosion rather than promote shelf sediment accumulation. In a pan-Arctic context, the Alaskan Beaufort shelf is somewhat similar to the Laptev Sea Shelf, where previous work has shown that sediment is also focused during the summer months (but for different reasons related to estuarine-like circulation under the Laptev plume). The Alaskan Beaufort example contrasts with previous work on the Canadian Beaufort Shelf, where dominant winds from the opposite direction (northwest) likely promote strong seaward dispersal of sediment rather than inner-shelf convergence. This study thus highlights the importance of understanding dominant wind patterns when considering seasonal and inter-annual storage, transport, and erosion of sediments from Arctic continental shelves.