Seasonal Variation of the Beaufort Shelfbreak Jet and its Relationship to Arctic Cetacean Occurrence

Peigen Lin, Xiamen University, Xiamen, China; Woods Hole Oceanographic institution, Physical Oceanography, Woods Hole, MA, United States, Robert S Pickart, Woods Hole Oceanographic Institution, Woods Hole, MA, United States and Kathleen Stafford, Applied Physics Laboratory University of Washington, Seattle, WA, United States
Abstract:
The Beaufort shelfbreak jet transports Pacific-origin water eastward and is an integral part of the exchange of heat, freshwater, and nutrients between the shelf and the basin in the Pacific Arctic. Using mooring data together with atmospheric reanalysis fields and satellite ice concentration data from 2008 to 2012, we quantify the seasonal variations of the shelfbreak jet and explore connections to the occurrences of bowhead and beluga whales. The volume transport, which peaks in the summer, can be decomposed into a wind-driven part and a background component. The two main atmospheric centers of action, the Aleutian Low and Beaufort High, primarily dictate the wind-forced component, although a more accurate prediction of this component is obtained when considering the ice thickness. Using the mooring timeseries we define an upwelling index that reveals enhanced wind-driven upwelling in June and October, which is modulated by the presence of pack ice. The seasonal presence of Arctic cetaceans is quantified using nearby passive acoustic mooring data. Bowhead whale calls are frequently observed during times of upwelling and hence are present in greater numbers during June and October. By contrast, beluga call occurrence is highest during July when there is more nutrient-rich winter water present in the shelfbreak current and the ice cover is decreasing.
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