Sea level variations at the world coastlines over the past two decades from reprocessed satellite altimetry

In the context of the ESA Climate Change Initiative Sea Level project, we performed a complete reprocessing of high resolution (20 Hz, i.e., 350m) along-track altimetry data of the Jason-1, Jason-2 and Jason-3 missions over January 2002 to June 2021 in the world coastal zones. This reprocessing provides along-track sea level time series and associated trends from the coast to 50 km offshore over the study period. We call ‘virtual coastal stations’ the closest along-track point to the coast. This creates a new network of 1160 virtual sites well distributed along the world coastlines. We performed Empirical Orthogonal Decomposition analyses of the sea level time series at the virtual stations, globally and regionally, in order to: (1) identify the main drivers of the coastal sea level variability at interannual time scale, and (2) assess the along-coast coherence of the sea level response to the dominant drivers. The results highlight those coastlines where the EOF first mode reveals a dominant long-term coastal sea level rise They also help in identifying other regions where the coastal sea level is dominated interannual variations, highly correlated to natural climate modes. This analysis allows us to clearly separate portions of the world coastlines displaying different sea level behaviors. In regions where no tide gauge data are available (a large portion of the southern hemisphere), our results provide new information on present day sea level changes at the coast, hopefully useful for coastal adaptation.