VARIATIONS IN THE EAST AUCKLAND CURRENT FROM SATELLITE RADAR ALTIMETER DATA

We analysed satellite radar altimeter data for the New Zealand area du ring the period November 1992 to June 1994. Sea-surface height anomali es from the Topex-Poseidon and ERS-1 radar altimeter data were consist ent in locating and identifying variability within most of the recogni sed major features in the area. Near the New Zealand coast, the tidal models used in the analysis did not perform well. A considerable error in the modelled M(2) tidal component was apparent as an aliased signa l with a period of about 62 days (sampled at a 10 day orbital repeat p eriod). A correction was made to remove the error. Profiles of cross-t rack current anomalies were deduced for the East Auckland Current syst em and there was good general agreement between Topex-Poseidon and ERS -1 products, Using surface measurements along one subsatellite track, the height data were calibrated and a history of absolute cross-track currents to the north-east of North Cape was produced. This showed a s trong east-southeastward flow between 33.5 degrees S and 34 degrees S, with a return flow meandering between 32 degrees S and 33 degrees S. The strength of the current at a fixed location varied considerably, w ith a possible seasonal influence. The histories of cross-track curren t-anomaly profiles, along with current-anomaly vectors constructed for the track cross-over points, give a coherent picture of features in t he area. In particular, an anticyclonic eddy to the north-east of New Zealand is identified moving south-eastward during the spring of 1993.