State-of-the-art Vertical Land Movement Corrections from GPS for Sea-level Studies

GPS data reanalysis are common nowadays when aiming at the highest consistency of the estimated products for the whole data period. The University of La Rochelle Consortium (ULR) has carried out several GPS data reanalysis campaigns with an increasing tracking network, an improving processing strategy and the best available models. The objective of this effort is to correct for long-term vertical land movement (VLM) at tide gauges (TG) through the estimation of accurate GPS vertical velocities at co-located stations (GPS@TG), for long-term sea-level change studies. In this presentation we show the geodetic results of the last velocity field estimated at ULR (named ULR5) which includes 407 GPS stations, from which 292 are GPS@TG. This represents the largest ever estimated GPS@TG velocity field. The GPS data processing strategy, the terrestrial frame definition and the velocity estimation procedures are described. The quality of the estimated velocities are shown through the repeatability of the station positions and the stability of the terrestrial frame definition, both at the mm level, and the precision of the velocity field at the sub-mm/yr level, including the analysis of the time-correlated noise content of the position time series. This high-quality velocity field will be used to correct for VLM at worldwide TGs in order to explore long-term temporal and spatial sea-level variability.