The importance of coastal altimetry retracking and detiding: a case study around the Great Barrier Reef, Australia

Abstract

A new approach for improving the accuracy of altimetry-derived sea level anomalies (SLAs) near the coast is presented. Estimation of SLAs is optimized using optimal waveform retracking through a fuzzy multiple retracking system and the most appropriate detiding method. With the retracking system, fuzzy-retracked SLAs become available within 5 km of the coast; meanwhile it becomes more important to use pointwise tide modelling rather than state-of-the-art global tidal models, as the latter leave residual ocean tide signals in retracked SLAs. These improvements are demonstrated for Jason-2 waveforms in the area of the Great Barrier Reef, Australia. Comparing the retrieved SLAs with in situ tide gauge data from Townsville and Bundaberg stations showed that the SLAs from this study generally outperform those from conventional methods, demonstrating that adequate waveform retracking and detiding are equally important in bringing altimetry SLAs closer to the coast.

Acknowledgements

The first author (Idris) is supported by the Australian Endeavour International Postgraduate Research Scholarship, The University of Newcastle Research Scholarship, and The University of Technology Malaysia Scholarship. We would like to acknowledge the Archiving, Validating, and Interpretation of Satellite Oceanography (AVISO) data team for kindly providing Jason-2 data. The Inge Lehmann foundation granted the visit of Andersen to the University of Newcastle. We thank Yongchun Cheng (Technical University of Denmark) for his help with part of the computations of the response method. We also thank the anonymous reviewers and editor for their comments on this article.