Atlantic Water and the Chukchi Polynya

Atlantic Water (AW), with temperature > -1°C and salinity > 33.6, has been observed to upwell from deeper than 200 m in the Arctic Basin onto the Chukchi Shelf via Barrow Canyon. Most observations of AW on the Chukchi shelf have been in or near Barrow Canyon; observations of AW farther onto the shelf are rare. NOAA’s Ecosystems and Fisheries Oceanography Coordinated Investigations (EcoFOCI) program has deployed year-round moorings in the eastern Chukchi Sea since fall 2010. Data collected include currents, temperature and salinity, oxygen, chlorophyll fluorescence, nitrate, and ice draft. Despite mooring location on the shelf ~225 km from the head of Barrow Canyon, three AW events have been observed during three winters of moored observations at mooring C1 (70.8°N, 163.2°W). Two of those events occurred during the winter of 2010/2011 and one during January 2014. No events were observed during the winter of 2011/2012, a year with little polynya activity in the region. The C1 mooring was not deployed in 2012/2013. In addition to changes in temperature and salinity, the AW events are associated with southwestward winds and currents, changes in the sea-ice cover, and increased nutrient concentrations in the bottom water. The first AW event (Oct/Nov 2010) was observed near the ice edge during ice advance while the other two events were associated with polynyas. This suggests that both latent and sensible heat mechanisms may be important to the formation and maintenance of some Chukchi Sea polynyas.