Combining T/P altimetric data with hydrographic data to estimate the mean dynamic topography of the North Atlantic and improve the geoid

摘要

The mean dynamic topography of the surface ofthe North Atlantic is estimated using an inverse model of the ocean circulationconstrained by hydrographic and altimetric observations. In the North Atlantic,altimetric observations have no significant impact on the topography estimatebecause of the limited precision of available geoid height models. They have asignificant impact, however, when uncertainties in the density field areincreased to simulate interpolation errors in regions where hydrographic dataare scarce. This result, which moderates the conclusion drawn by Ganachaud andco-workers of no significant contribution of altimetric observations to thedetermination of the large-scale steady circulation, reflects the simple ideathat altimetric data are most useful near the surface of the ocean and in areaswhere the hydrography is poorly determined. One application of the presentinverse estimate of the mean dynamic topography is to compute a geoid heightcorrection over the North Atlantic which reduces the uncertainty in the geoidheight expanded to spherical harmonic 40 down to a level of about 5 cm.Key words. Oceanography: general (climate andinterannual variability) · Oceanography: physical (general circulation; remotesensing)