Global sea level change and thermal contribution

Abstract

The global long-term sea level trend is obtained from the analysis of tide gauge data and TOPEX/Poseidon data. The linear trend of global mean sea level is highly non-uniform spatially, with an average rate of 2.2 mm year−1 in T/P sea-level rise from October 1992 to September 2002. Sea level change due to temperature variation (the thermosteric sea level) is discussed. The results are compared with TOPEX/Poseidon altimeter data in the same temporal span at different spatial scales. It is indicated that the thermal effect accounts for 86% and 73% of the observed seasonal variability in the northern and southern hemispheres, respectively. The TOPEX/Poseidon observed sea level lags behind the TSL by 2 months in the zonal band of 40°–60° in both the northern and southern hemispheres. Systematic differences of about 1–2 cm between TOPEX/Poseidon observations and thermosteric sea level data are obtained. The potential causes for these differences include water exchange among the atmosphere, land, and oceans, and some possible deviations in thermosteric contribution estimates and geophysical corrections to the TOPEX/Poseidon data.