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 correcting for a recently discovered error in the measurements, the estimated 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 and 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 rate 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 the contribution of interannual and decadal mean sea level variations cannot presently be isolated, a longer time series is required before long-term climate change signals can be detected. in addition, an improved understanding of the T/P measurement system performance with time is needed.