Terrestrial reference frame effects on global sea level rise determination from TOPEX/Poseidon altimetric data

Over the past years, satellite altimetry has produced several significant improvements in our scientific understanding of the oceans. However, several results related to global or regional sea level changes still too often rely on the assumption that orbit errors coming from station coordinates adoption can be neglected in the total error budget. The goal of this paper is to specifically study this general assumption and to assess its limitation. In a first step, in the case of the TOPEX/Poseidon satellite, we first characterized orbital errors coming from the adoption of a specific Terrestrial Reference Frame using a Monte-Carlo-based simulation method using DORIS data. In a second step, we analyzed the effect of these systematic orbital errors on the mean sea level derived from altimeter data. From these results, we derived linear transfer functions that can be used for several purposes like error budget estimation in altimetry or local tie specifications for the implementation of new tracking stations. These simulations show that the main source of errors comes from current imprecision in the Z-axis realization of the frame. A 10 mm error in the TZ realization can create a −1.2 mm of systematic errors in the derived mean sea level due to the North-South asymmetric distribution of the oceans all over the world. Significant sea level rise could erroneously be attributed to a possible warming of the biosphere while they just come from systematic errors in the Terrestrial Reference Frame used to generate the satellite operational orbits. Finally, we assessed the accuracy of present Terrestrial Reference Frame realizations and derived a realistic error budget for this specific source of error. For the ITRF97 realization, a current precision of 3.0 mm in sea level and 0.37 mm/yr in sea level rise was obtained. These precisions should gradually improve with future Terrestrial Reference Frame realizations.