New TOPEX sea state bias models and their effect on global mean sea level

During the calibration of the Jason‐1 altimeter, it was discovered that the Jason‐TOPEX sea surface height (SSH) residuals contained a trend correlated with significant wave height (SWH), indicating an error in the sea state bias (SSB) model for one or both of the altimeters. After updating the SSB model for Jason the trend remained, which pointed to an error in the TOPEX model. Since two different TOPEX altimeters (TOPEX_A and TOPEX_B) have operated during the mission, we estimated new SSB models using data from each one. The estimated SSB model for TOPEX_B is significantly different than the model provided with the data, which was estimated using only TOPEX_A data. Replacing the SSB model on TOPEX with the new TOPEX_A and TOPEX_B models not only removes the correlation with SWH in the Jason‐TOPEX SSH residuals, it also removes most of a bias between TOPEX_A and TOPEX_B that has been observed in tide gauge calibrations. The magnitude of the change between TOPEX_A SSH and TOPEX_B SSH is of the order of 10 mm globally, with TOPEX_B SSH increasing when the new SSB model is applied. The application of this improved model will increase the rate of observed global mean sea level rise from 1.7 mm/year when the original TOPEX data are used to 2.8 mm/year when the updated SSB models are applied.