Figure 7: Currents in the Kuroshio region in layers 1-4 in March during year 2 after initialization.The model is a 4.5 layer model of the Pacific Ocean. Horizontal resolution is 1/4°× 1/4°. Maximum vector length corresponds to currents of 0.3m/s for layer 1-2 and 0.15m/s for layer 3-4. Fat vectors are currents larger than these limits. Only every 9th vectors is shown.
The deeper layers have no forcing except along the open boundaries where relaxation toward temperature and salinity annual mean observations are used for all layers. The method used along the open boundaries combines a radiation scheme and the flow relaxation scheme (Jensen, 1998). Currents in the Kuroshio region (Fig. 7) show large variability as in the previous model. Eddies in the Kuroshio Extension region are baroclinically unstable, typically with northward transport of warm water in layer I just east of a southward transport of cold water in layer 2.
Intense waves and eddies are also found in the subtropical frontal zone near 20｡?. Figure 8 shows the temperature field associated with the currents in Fig. 7. Eddies dominate below the thermocline in that region. Typical scales are 1000km. The 2.5 layer simulation has much less activity in this region, but it is not clear whether the increased eddy activity is due to the higher vertical resolution or inclusion of thermodynamics.
The model circulation has the expected structure of the tropical current systems: The North Equatorial Current from 10｡? to 20｡?, the Equatorial Counter Current from 4｡? to 10｡?, the South EquatorialCurrent from about 20｡? to 4｡?, interrupted by a South Equatorial Counter Current near 10｡?. The Equatorial Under Current is deep in the western Pacific, where it is present in layer 3 (centered about 290m), and shoals to the surface in the Eastern Pacific.
