Sea level along the world's coastlines can be measured by a network of virtual altimetry stations

For nearly 30 years, space-based radar altimetry has been routinely measuring changes in sea level at global and regional scales. But this technique designed for the open ocean does not provide reliable sea level data within 20 km to the coast, mostly due to land contamination within the radar echo in the vicinity of the coast. This problem can now be overcome through dedicated reprocessing, allowing the retrieval of valid sea level data in the 0-20 km band from the coast, and then the access to novel information on sea level change in the world coastal zones. Here we present sea level anomalies and associated coastal sea level trends at 756 altimetry-based virtual coastal stations located along the coasts of North and South America, Northeast Atlantic, Mediterranean Sea, Africa, North Indian Ocean, Asia and Australia. This new dataset, derived from the reprocessing of high-resolution (300 m) along-track altimetry data from the Jason-1, 2 and 3 missions from January 2002 to December 2019, allows the analysis of the decadal evolution of coastal sea level and fills the coastal gap where sparse sea level information is currently available. Sea level trends at decadal timescales within 20 km of the world's coastlines can be determined for the period 2002 to 2019 through dedicated reprocessing of high-resolution along-track altimetry data.

Automated summary

Space-based radar altimetry has been used for nearly 30 years to measure changes in sea level, but it is not reliable within 20 km of the coastline. By reprocessing high-resolution data, this problem can be overcome and more accurate sea level information can be obtained, filling the data gap in coastal areas.