Subinertial Currents

Ocean surface currents at AGL site exhibit strong variability in response to different processes that superimpose at all time-scales. The tide causes a rhythmic rotation with a dominant semidiurnal frequency, strong winds trigger surface flows and after their relaxation the Coriolis force cause rotary currents with the period of local pendulum day (about 17 hours at the AGL latitude). Seasonality in winds, dominant from the northeast in summer and from the southwest in winter, is rflected as seasonality on the currents. Also there exist a slope current that develops in late autumn to early winter carrying waters of southern origin to the Bay of Biscay.

The usual treatment of current records consists of separating short-term oscillations of the scale of the tide or less from the slowly varying background flow (subtidal). Followinf figures provide the realtime currents together with the long-term average (monthly climatology) of subtidal flow.