An investigation of ocean tides derived from along‐track altimetry

Abstract

With the availability of a long data record of accurate sea surface height measurements, it is now possible to estimate the ocean tide along the ground track of TOPEX/POSEIDON (T/P). This has been done from over 4.5 years of data using both response and harmonic analyses. These estimates agree well with each other, and with other gridded models over both long and short wavelengths in deep water, for those tidal components whose alias frequencies are separable by the Rayleigh criterion. Comparisons of along‐track (AT) estimates to current tide models show shorter wavelength features not present in dynamical and empirical global models. AT estimates follow the general trends of empirical models far from sharp topographical changes, but near sharp changes, they tend to follow dynamical model results. Error estimates show that the T/P data are not significantly worse in shallow water than in deep water, suggesting that there is accurate information about tides in shallow water in the T/P data. Tides at crossover locations are improved by computing estimates with both ascending and descending track data. Possible techniques to improve AT tidal estimates between crossover points are discussed. AT tidal estimation can be useful for studying local regions where resolution is more important than regular spacing, for studying tidal interactions over sharp topography, and for extending tidal models from deep to shallow waters through assimilation into a dynamical model.