. Acknowledgments, Etudes Spatiales (CNES) for the financial support. The study benefited from data made available by Ag^ encia Nacional de Aguas (ANA) and by the European Space Agency (ESA) under the form of Geophysical Data Records (GDRs) The multimission database of GDRs is maintained by the Centre de Topographie des Oc eans et de l'Hydrosphère (CTOH) at LEGOS. The authors also thank G, Cochonneau (IRD) and M. C. Gennero (IRD) for their help in data acquisition and processing and three anonymous reviewers for their valuable comments

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