Determination of evaluation of the altimetric mean level of the Western Mediterranean from the Jason-1 data: Comparison with analysis of tidal gauge measurements

Abstract

The sea surface topography, which is directly linked to the shape of the geoid and to oceanic effects, is only measurable thanks to the spatial and temporal resolution of satellite altimetry. The contributions of satellite altimetry study in the Mediterranean have been considerable. The first maps of the marine geoid, with relative accuracy of one to two decimetres depending on the methods used, have contributed greatly to the understanding of geophysical phenomena. Subsequently, thanks to reductions in orbital errors, improvements in gravitational models, and to the development of pseudo-geometrical orbit computations, the accuracy of determination of the absolute mean sea level has improved from several meters to a few centimetres. The study presented here aims to determine seasonal variations in mean sea level in the Western Mediterranean basin by analysis of Jason-1 data corrected of different perturbations like the geophysical phenomena, the ocean wave influence, the inverse barometer effect, and the orbit error. The analysis of altimetric data Jason-1 allowed us to observe a strong amplitude of variations of the average level in the Western Mediterranean basin, of the order of 20 cm, with a characteristic period of one year. The comparison of the variation of the average height sea level at the harbour of Algiers obtained from analysis of altimetric data Jason-1 and from the harmonic analysis of tidal gauge measurements, showed almost identical results.