Circulation in the Western Chukchi Sea and its Role in the Ecosystem

Pacific water flowing northward through Bering Strait has profound impacts on the physical state and ecosystem of the Western Arctic Ocean. The cold, dense water fluxed northward in winter and spring ventilates the upper halocline and provides nutrients that fuel primary production and impact the carbon cycle.The warm water penetrating northward in summer melts the seasonal ice and is contributing to the decline of the perennial ice pack. As such, it is crucial that we understand the pathways, modifications, and dynamics of the Pacific water as it penetrates the Arctic domain. Over the last decade, the Russian-American Long-Term Census of the Arctic (RUSALCA) program has provided an unprecedented physical-biological data set in the western Chukchi Sea, where historically there has been a dearth of data. Three broad shipboard surveys were carried out in summer 2004, 2009, and 2012. This proposal seeks support to process the 2012 hydrographic/velocity data and make them available to the RUSALCA PIs, and to carry out two synthesis activities using the shipboard data in conjunction with other complimentary data sets. The first project investigates the circulation, dynamics, and water mass transformation that occurs in Herald Canyon, which is a critical choke point through which Pacific Water communicates with the deep basin. The second project addresses the flow pathways and chemical properties in the western Chukchi Sea, with special emphasis on the Wrangel Island region which supplies water to both the head and mouth of Herald Canyon. The repeat surveys, including an additional data set collected in 2008, allows investigation of the seasonal versus interannual variability of the system. The overall goal is to elucidate the relative roles of topography, atmospheric forcing, and upstream influence (Bering Strait) in dictating the circulation and modification of the Pacific-origin water entering the Russian Arctic, and explore various ecosystem impacts. Two foreign guest students, including one from the P.P. Shirshov Institute of Oceanology, will work on the project as part of their PhD theses.