Quasi-zonal jets in 3-D Argo data of the northeast Atlantic

Time-mean zonal velocities, estimated from Argo float trajectories and density profiles, are systematically examined for quasi-zonal jets, or striations, with the use of a simple search algorithm. A comparison to altimeter data combined with an independent estimate of the mean dynamic topography shows that the jets in the 2004-2006 period examined are persistent and stationary. The jets have a typical meridional width of 100 to 200 km and a median transport of 4 Sverdrups. The jets tilt at approximately 6° from southwest to northeast in the horizontal plane, but show no significant tilt in the vertical plane. Velocities and the cross-stream width are similar for the westward and eastward jets.

Figure 1: Evidence of quasi-zonal jets in the Argo data for 2004 through 2006: (a) the map of zonal velocity at 1000 m shows many zonally elongated areas of eastward and westward velocity. Areas shaded gray are deeper than 2000 m, where no data is available. (b) A vertical cross section at 20°W of the same data shows that the alterations of positive and negative velocity are vertically coherent and reach to depths of more than 2000 m.