Global sea level rise and upper ocean heat storage estimates from TOPEX/POSEIDON satellite altimetry

Three years of altimeter data from the TOPEX/POSEIDON satellite were analyzed to estimate the rate of mean sea level rise and changes in upper ocean heat storage. The average rate of sea level rise based on TOPEX altimetry is +0.6 mm/yr over 1993-1995. An empirical orthogonal function (EOF) decomposition of the global SSH data revealed dominant modes of variability having annual, interannual, and semiannual timescales. The annual modes capture the hemispheric-scale changes in steric height due to seasonal heating variations, while the interannual modes show oscillations in the tropical Pacific consistent with recent El Nino/La Nina events. The contribution of each EOF mode to global sea level rise was assessed, and most of the rise in mean sea level is represented by a single interannual mode, demonstrating that a long-term rise in mean sea level cannot be isolated from interannual variability in a data set which spans only three years.; TOPEX altimetry was also used to predict heat storage in the upper ocean. Monthly climatological fields of temperature and salinity were used to compute linear regression coefficients relating dynamic height and heat storage. These coefficients were then used with the TOPEX altimetry to create maps of heat storage in the ocean. Changes in global upper ocean heat storage were investigated as a possible contributing factor to the rise in mean sea level. Comparisons of TOPEX heat storage estimates with in situ XBT data were made, and the two data sets were found to be well correlated. Differences between TOPEX and XBT heat storage values were used to assess the stability of the TOPEX altimeter range measurements and to estimate the contribution of upper ocean heating to mean sea level rise.