CoAuthors

John Wahr (University of Colorado, USA); Brian Beckley (SGT, Inc., USA)

We evaluate errors in the pole tide model that is currently adopted by most users of satellite altimeter sea surface height measurements and identify possible improvements to that model. Of the various geophysical models that are typically applied as corrections to these measurements, those for the pole tide and luni-solar body tide have not been revised since the launch of TOPEX/Poseidon more than two decades ago. We describe two improvements to the pole tide model for satellite altimeter measurements. Firstly, we recommend an approach that improves the model for the response of the oceans by including the effects of self-gravitation, loading, and mass conservation. Our recommended approach also specifically includes the previously ignored displacement of the solid Earth due to the load of the ocean response, and includes the effects of geocenter motion. Altogether, this improvement amplifies the modeled geocentric pole tide by 15%, or up to 2 mm of sea surface height displacement. We validate this improvement using two decades of satellite altimeter measurements. Secondly, we recommend that the altimetry pole tide model exclude geocentric sea surface displacements resulting from the long-term drift in polar motion. The response to this particular component of polar motion requires a more rigorous approach than is used by conventional models. We show that erroneously including the response to this component of polar motion in the pole tide model impacts interpretation of regional sea level rise by +/- 0.25 mm/year.