On the Ekman divergence in an oceanic jet

When a steady wind stress acts on the rapidly northward-moving Gulf Stream, an intense Ekman divergence is produced at the axis of the Stream. This is primarily due to the fact that, at the axis, the effective Coriolis parameter, the sum of the earth's rotation and the shear of the Stream, changes by three-fold in a distance of 15 km. The magnitude of this divergence, when the wind is southerly, is two orders of magnitude larger than that in the regions outside the jet and results in intense upwelling.