Annual cycle in mean sea level from Topex–Poseidon and ERS-1: inference on the global hydrological cycle

Abstract

Using satellite altimetry time series from Topex–Poseidon and ERS-1 to estimate the annual variation of the global mean sea level, we study the global hydrological cycle at the annual frequency. The observed annual sea level signal is first corrected for steric effects and further compared to the annual change in atmospheric water vapor content and soil moisture of continents. The altimetry-derived global mean sea level variation corrected for steric effects, i.e., due to annual ocean mass change amounts to 9.5 mm with a maximum in mid-September. This observation is consistent with the signal estimated from atmospheric and continental data. Accounting for the variations of water mass stored in the superficial soil layers and in the atmosphere, one can get a reasonable phase agreement with satellite observations, with an amplitude difference of only 2.5 mm. This difference may result from uncertainties of the soil moisture estimate, or from neglecting the water storage variations in other reservoirs, such as the rivers, the underground or the ice sheets.