Vertical structure and temporal variability of currents over the Chukchi Sea continental slope

摘要

Observations from a single mooring site on the northern Chukchi Sea continental slope near the 1000-m isobath are presented. This site was occupied consecutively for three years (spanning September 2014-August 2017). Vertically the flow divides into three depth ranges: the upper similar to 200 m, similar to 200-similar to 850 m and near-bottom flow. In the upper similar to 200 m, the mean flow was northwestward and strongest in the summer months. During winter months, currents decreased in magnitude, and in some years even reversed in direction. Satellite-tracked drifter trajectories (drogue depth similar to 30 m) show this along-slope flow persists at least from 156 to 165 degrees W, with an average velocity of similar to 17 cm s(-1). This northwestward flowing current is the Chukchi Slope Current. From similar to 250 m to similar to 850 m, the flow reversed; this weak flow is the Arctic-wide cyclonic boundary current advecting Atlantic Water. The mean flow at similar to 900 m is weak and on an annual time scale not significantly different from 0 cm s(-1). It consists of Arctic deep water. In the upper two layers, currents vary on the scale of days to seasons, with short-term reversals common. Currents below 40 m were not significantly correlated with local winds nor wind stress curl. We hypothesize that the northwestward flowing Chukchi Slope Current is a consequence of dynamics associated with the Beaufort Gyre.