The IAS2024 coastal sea level dataset and first evaluations

Abstract. A new dedicated coastal sea level dataset called the International Altimetry Service 2024 (IAS2024, https://doi.org/10.5281/zenodo.13208305, Peng et al., 2024c) has been presented to monitor sea level changes along the world’s coastlines. One of the reasons for generating this dataset is the quality of coastal altimeter data has been greatly improved with advanced coastal reprocessing strategies. In this study, the Seamless Combination of Multiple Retrackers (SCMR) strategy is adopted to obtain the reprocessed Jason data for January 2002 and April 2022. The evaluation results show that the data availability of the IAS2024 dataset over global coastal oceans is much higher than that of the European Space Agency Climate Change Initiative version 2.3 (ESA CCI v2.3) dataset. The closure of trend differences (0.16 ± 3.98 mm yr⁻¹) between IAS2024 and Permanent Service for Mean Sea Level (PSMSL) tide gauge data is observed at the global scale, which further demonstrates the good performance of the IAS2024 dataset in monitoring the coastal sea level changes. The altimeter-based virtual stations have been built with the IAS2024 dataset over 0−10 km, 5−15 km and 10−20 km coastal strips, which will contribute to the analysis of coastal sea levels for the ocean community and the risk management for the policy makers. Our study also points out that no obvious variations exist in linear sea level trends from offshore to the coast in most coastal zones. In addition, the vertical land motion (VLM) estimates from the combination of coastal altimeter data with tide gauge records agree well with the University of La Rochelle 7a (ULR7a) Global Navigation Satellite System (GNSS) solution (0.09 ± 2.22 mm yr⁻¹), suggesting that altimeter-derived VLM estimates can be an independent data source to validate the GNSS solutions.