1.2.2 Ocean gyres

Baroclinic instability is a ubiquitous process in the ocean, as well as the atmosphere. Ocean eddies play an important role in modifying the hydrographic structure and current systems of the oceans. Coarse resolution models of the oceans cannot resolve the eddy field and yield rather broad, diffusive patterns of ocean currents. But if the resolution of our models is increased until the baroclinic instability process is resolved, numerical solutions of a different and much more realistic kind, can be obtained.

Figure 1.6 shows the surface temperature and velocity field obtained from MITgcm run at horizontal resolution on a grid in which the pole has been rotated by 90 on to the equator (to avoid the converging of meridian in northern latitudes). 21 vertical levels are used in the vertical with a `lopped cell' representation of topography. The development and propagation of anomalously warm and cold eddies can be clearly seen in the Gulf Stream region. The transport of warm water northward by the mean flow of the Gulf Stream is also clearly visible.

Figure 1.6: Instantaneous temperature map from a simulation of the North Atlantic. The figure shows the temperature in the second layer (37.5m deep).

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