Low frequency ocean circulation around New Zealand from model winds and the Island Rule

The Island Rule allows the ocean transport around an island to be determined from wind stress, in a simplified dynamic model. Consequently the transport in the Western Boundary Current (WBC) can be derived from the difference between the Island Transport and the Sverdrup transport to the east. This method has been applied to New Zealand using monthly ECMWF model wind stress data. Preliminary results show encouragingly robust and realistic values with a degree of correlation with ENSO events. However exact validation of the model is difficult because of the effect of the observed meso-scale eddies in the East Auckland Current system, which forms the WBC off the northeast coast of New Zealand. Some comparisons between model and ocean transports, derived from both oceanographic data and Topex/Poseidon altimetry, will be presented.