Mean sea level and sea surface variability of northwest pacific ocean and eastern China seas from Geosat altimetry

Abstract

Collinear analysis technique is widely used for determining sea surface variability with Geosat altimeter data from its Exact Repeat Mission (ERM). But most of the researches have been only on global scale or in oceans deeper than 2000 m. In shallow shelf waters this method is hampered by the inaccuracy of ocean tide data supplied with Geosat Geophysical Data Records (GDRs). This work uses a modified collinear analysis technique characterized by simultaneous separation of mean sea level and ocean tide with the least squares method, to compute sea surface variability in the Northwest Pacific Ocean and eastern China Seas. The mean sea level map obtained contains not only bathymetric but also dynamic features such as amphidromes, indicating considerable improvement over previous works. Our sea surface variability maps show clearly the main current system, the well-known Zhejiang coastal upwelling, and a northern East China Sea meso-scale eddy in good agreement with satellite sea surface temperature (SST) observation and historical in situ measurement. These all suggest that meaningful and reliable oceanographic results can still be achieved in shallow shelf waters from Geosat altimetry as long as proper data processing techniques are applied.