Improving the Coastal Mean Dynamic Topography by Geodetic Combination of Tide Gauge and Satellite Altimetry

Abstract

The ocean mean dynamic topography (MDT) is the surface representation of the ocean circulation. The MDT may be determined by the ocean approach, which involves temporal averaging of numerical ocean circulation model information, or by the geodetic approach, wherein the MDT is derived using the ellipsoidal height of the mean sea surface (MSS), or mean sea level (MSL) minus the geoid as the geoid. The ellipsoidal height of the MSS might be estimated either by satellite or coastal tide gauges by connecting the tide gauge datum to the Earth-centred reference frame. In this article we present a novel approach to improve the coastal MDT, where the solution is based on both satellite altimetry and tide gauge data using new set of 302 tide gauges with ellipsoidal heights through the SONEL network. The approach was evaluated for the Northeast Atlantic coast where a dense network of GNSS-surveyed tide gauges is available. The typical misfit between tide gauge and satellite or oceanographic MDT was found to be around 9 cm. This misfit was found to be mainly due to small scale geoid errors. Similarly, we found, that a single tide gauge places only weak constraints on the coastal dynamic topography.

Keywords:

• Mean dynamic topography
• satellite altimetry
• tide gauge

Acknowledgements

The authors are thankful to Phil Woodworth for valuable suggestions. The authors acknowledge the support to the ESA STSE GOCE ++ DYCOT project via ESA contract No 4000114331//15/NL/FF/gp. They also acknowledge the SONEL (http://www.sonel.org) and RENAG (http://webrenag.unice.fr) services for providing GPS data and geodetic ties at tide gauges. Hongyang Lin, Mick Filmer, Marc Véronneau are warmly thanked for providing geodetic ties respectively in Japan and USA, Australia and Canada.

Disclosure statement

No potential conflict of interest was reported by the authors.