IMPROVED DETERMINATION OF GLOBAL MEAN SEA-LEVEL VARIATIONS USING TOPEX POSEIDON ALTIMETER DATA/

The TOPEX/POSEIDON satellite altimeter mission has measured sea level on a global basis over the last 4 years at 10 day intervals. After cor recting for a recently discovered error in the measurements, the estim ated rate of global mean sea level change over this time period is -0. 2 mm/year. Comparisons to tide gauge sea levels measured in spatial an d temporal proximity to the satellite measurements suggest there is a residual drift in the satellite measurement system of -2.3 +/- 1.2 mm/ year, the origin of which is presently unknown. Application of this ra te correction yields a ''calibrated'' estimate of +2.1 +/- 1.3 mm/year for the rate of sea level rise, which agrees statistically with tide gauge observations of sea level change over the last 50 years. Since t he contribution of interannual and decadal mean sea level variations c annot presently be isolated, a longer time series is required before l ong-term climate change signals can be detected. in addition, an impro ved understanding of the T/P measurement system performance with time is needed.