A bathymetry and altimetry profile across the Southwest Indian Ridge crest at 31°S latitude

During March 1983 the M/V "Marion Dufresne" obtained a bathymetry profile along more than 1500 km of a SEASAT altimeter sub-track across the Southwest Indian Ridge crest at 31°S latitude. We have used these data to estimate the thermal and elastic thickness of the oceanic lithosphere in the vicinity of the ridge and to evaluate the performance of the SEASAT altimeter. The thermal thickness appears to be in the range 72-109 km while the elastic thickness is about 2-5 km. There is a good correlation between the geoid calculated from the bathymetry and its compensation and the observed geoid derived from SEASAT data. The correlation is strongest for wavelengths greater than 45 km and poorest for shorter wavelengths. We attribute the poor resolution at short-wavelengths to instrument and oceanographic noise in the altimeter data combined with the reduced sensitivity of the geoid to bathymetric relief at very short wavelengths