Estimation of mean dynamic height from altimeter profiles and hydrography

The mean dynamic height of the ocean surface is estimated along a subsatell ite track of TOPEX/Poseidon crossing the East Auckland Current system north east of New Zealand. Repeated hydrographic surveys along the track, togethe r with surface elevation anomalies deduced from TOPEX altimeter data, enabl e four independent estimates of the mean dynamic height. From these estimat es a more stable mean is calculated in which the uncertainty is estimated a s less than 5 cm. The result can be applied as a reference profile for cali brating a long series of TOPEX passes so that cross-track geostrophic curre nts can be calculated. The scatter in the individual estimates indicates su fficient sampling variability to caution against using single hydrographic surveys as a basis for calibrating the satellite data.