Nitrate Distribution in Pacific Winter Water Along the Northern Edge of the Chukchi Sea

Abstract Nutrient‐rich, Pacific‐origin winter water (PWW) is a primary source of nitrate for the western Arctic Ocean, spurring primary production at the base of the food web. This cold water exits the Chukchi Sea shelf via Herald Canyon and Barrow Canyon, which feed the eastward‐flowing Chukchi Shelfbreak Jet (CSJ) and the westward‐flowing Chukchi Slope Current, respectively. Using historical measurements of nitrate, hydrography, and velocity between 2002 and 2023, we characterize the spatial distribution of nitrate along the northern edge of the Chukchi shelf. Our analysis reveals that the nitrate concentration of PWW increases significantly to the west. Documenting the sources of nitrate in Herald Canyon and Barrow Canyon, and following its downstream evolution in the two currents, we demonstrate that the westward increase in nitrate is primarily associated with the CSJ. Our results shed light on the physical basis for seasonal phytoplankton growth and carbon sequestration in the region.