The Geoid and Ocean Cieculation

This chapter describes the relationship between the ocean circulation and the geoid, reviews the methods commonly used for determining the circulation using classical oceanographic techniques and satellite altimetry, and discusses the latest techniques for simultaneously estimating the circulation and the geoid. While conceptually the determination of the ocean circulation using satellite altimetry is simple, the influence of errors in the determination of the satellite position, errors in the model for the geoid, and errors in the environmental corrections make the task of accurately measuring the ocean circulation quite difficult. Presently, errors in the best available geoid models are larger than the ocean circulation signal for roughly degrees 15 and higher, except in some local areas, such as the Gulf Stream, where the geoid is better known from surface measurements. The measurement of the ocean circulation has been one of the principal goals of physical oceanographers for many years.