FULLY REPROCESSED ERS-1 ALTIMETER DATA FROM 1992 TO 1995 - FEASIBILITY OF THE DETECTION OF LONG-TERM SEA-LEVEL CHANGE

Global mean sea level observations are necessary to answer the urgent questions about climate changes and their impact on socio-economy, At GeoForschungsZentrum/Geman Processing and Archiving Facility ERS altim eter data is used to systematically generate geophysical products such as sea surface topography, high-resolution geoid and short-and long-p eriod sea surface height models. On the basis of this experience, full y reprocessed ERS-1 altimeter data is used to generated a time series of monthly sea surface height models from April 1992 to April 1995. Th e reprocessing consists of improved satellite ephemerides, merging of Grenoble tidal model, and application of range corrections due ro timi ng errors. With the new data set the TOPEX/POSEIDON prelaunch accuracy requirements are fulfilled. The 3-year time series is taken to estima te the rate of change of global mean sea level. A careful treatment of seasonal effects is considered. A masking of continents, sea ice, and suspect sea surface heights is chosen that is common for all sea surf ace height models. The obtained rate of change is compared to external results from tide gauge records and TOPEX/POSEIDON data. The relation of sea level changes and sea surface temperature variations is examin ed by means of global monthly sea surface temperature maps. Both globa l wind speed and wave height maps are investigated and correlated with sea surface heights and sea surface temperatures in order to find oth er indicators of climate variations. The obtained rate of changes of t he various global maps is compared to an atmospheric CO2 anomaly recor d, which is highly correlated to El Nino events. The relatively short period of 3 years, however, does not allow definite conclusions with r espect to possible long-term climate changes.