Sea State Bias Variability in Satellite Altimetry Data.

Sea State Bias (SSB) contributes to global mean sea level variability and it needs cm-level range adjustment due to the instrumental drift over time. To investigate its variations and correct the global and regional sea level trend precisely, we calculate the temporal and spatial variability of the SSB correction in TOPEX, Jason-1, Jason-2 and Jason-3 missions, separately, as well as in the combined missions over the period 1993-2017. The long-term trend in global mean operational 2D non-parametric SSB correction is about -0.03 +/- 0.03 mm/yr, which accounts for 1% of current global mean sea level change rate during 1993-2016. This correction contributes to sea level change rates of -1.27 +/- 0.21 mm/yr and -0.26 +/- 0.13 mm/yr in TOPEX-A and Jason-2 missions, respectively. The global mean SSB varies up to 7-10 mm during the very strong ENSO events in 1997-1998 and 2015-2016. Furthermore, the TOPEX SSB trend, which is consistent with recently reported sea level trend drift during 1993-1998, may leak into the determined global sea level trend in the period. Moreover, the Jason-1/2 zonal SSB variability is highly correlated with the significant wave height (SWH). On zonal average, SSB correction causes about 1% uncertainty in mean sea level trend. At high SWH regions, the uncertainties grow to 2-4% near the 50 degrees N and 60 degrees S bands. This should be considered in the study of regional sea level variability.