Assessment of geoid models offshore Western Australia using in-situ measurements

In Western Australia, coastal dynamics are influenced by a major ocean boundary current system, the Leeuwin Current, which is characterised by mesoscale features. To fully understand the Leeuwin Current using satellite altimeter measurements, we must have a precise (1-2 cm) and full-spatial-scale (100 km) geoid model. This paper focuses on a comparison between two mean dynamic ocean topography models derived from independent hydrographic climatologies, and an altimeter-observed mean sea surface referenced to recently released geoid models offshore of Western Australia (20S to 45S, 108E to 130E). The geoid models used include combined global geopotential models from the GRACE satellite mission and AUSGeoid98. The estimated mean dynamic ocean topography models are compared with independent dynamic ocean topography from CSIRO's Atlas of Regional Seas (CARS) climatology. The results show that the EIGEN GL04C and GGM02C EGM96 global geopotential models to degree and order 360 give the best comparisons against CARS in the Leeuwin Current region, suggesting that they should be used in the future for computing ocean transport, surface current velocities, and dynamic topography, and be used as a reference field for future computations of regional marine geoid models.