Wind-forced upwelling in Barrow Canyon: Transport of Pacific and Atlantic water masses

Barrow Canyon, situated at the shelfbreak in the eastern Chukchi Sea, is a major outflow point of Pacific water to the interior Arctic Ocean. The head of the canyon is also one of the regions of highest measured primary productivity, as well as benthic diversity, in the Western Arctic. Here we use mooring measurements collected at the head of the canyon from August 2002 to September 2004, and wind data from the nearby Pt. Barrow weather station, to investigate the occurrence of upwelling. In the mean, the near-bottom currents are down-canyon. However, upwelling occurs in all seasons, with the strongest events (at times exceeding 100 cm/s up-canyon flow) between October and March, i.e. during the autumn/winter storm season. Statistically, the current lags the wind by 12 hours, while the temperature and salinity respond 24-48 hours after the peak winds. A total of 55 events were identified over the course of the 2-year record. Surprisingly, most of the upwelled water was of Pacific-origin drawn from the basin. There was strong seasonality: Pacific summer water was upwelled in late-summer and fall, while Pacific winter water was upwelled in winter and spring. There were exceptions, however, when Atlantic water or hypersaline Pacific winter water was fluxed into the canyon. The conditions under which these latter events occurred are investigated. Our results imply that much of the wind-forced upwelling in Barrow Canyon transports nutrient-rich winter water to the head of the canyon, perhaps contributing to the enhanced primary productivity and benthic diversity observed there.