Synoptic variability of Pacific-water pathways in the eastern Chukchi Sea from a one-month Saildrone survey in summer 2022

Ziyi Zhou¹, Peigen Lin¹, Robert S. Pickart², Frank Bahr², Michael Steele³
1. School of Oceanography, Shanghai Jiao Tong University, China
2. Woods Hole Oceanographic Institution, USA
3. Polar Science Center, Applied Physics Laboratory, University of Washington, USA


The inflow of Pacific water through Bering Strait is the main source of heat, freshwater, and nutrients to the western Arctic Ocean. It is generally believed that there are three main, topographically steered pathways by which Pacific water flows poleward through the Chukchi Sea: the Alaskan Coastal Current (ACC), the Central Channel (CC) branch, and the western pathway. In this study, we analyze 52 high-resolution Saildrone occupations of a section extending offshore from  Pt. Hope, AK, the so called Distributed Biological Observatory Line 3. The data were collected from 21 July 21 to 17 August 2022 and consist of surface hydrography and full water column velocity. Our observations reveal that the CC Branch is not a single coherent flow but is instead composed of two distinct cores—CC_west and CC_east—whose strength and cross-stream location vary synoptically. On average their transports are similar and both are characterized by relatively high sea surface salinity. In contrast, the ACC flows adjacent to the coast and carries the warmest and freshest water. The freshwater signal in the ACC originates from both Kotzebue Sound and the Bering Strait inflow, with their relative contributions modulated by local wind forcing. The effect of such wind forcing on the two CC branches is investigated.