Potential vorticity (10-10 m-1s-1) on various isopycnal surfaces. Only small values are plotted for clarity. The outcrop line for each isopycnal is plotted in white dashed line where the 100 m contour is in the blue dotted line to mark the so-called mixed later (MLD) front where sharp MLD gradient exists.

Mode waters form where the MLD front and the outcrop line intersect. In the 40-year simulation, the anomalous Sverdrup flow changes the path of these mode waters by as much as 1000 km in the zonal direction, causing large subsurface temperature variability. See Xie et al. (2000) for details.

Using this OGCM results, subsurface temperature variability on decadal timescale has been examined by Xie et al. (2000).