ALTICAP: A new global satellite altimetry product for coastal applications

Abstract. Observing sea level and its variations is of great importance for many scientific, societal and economic issues. This data paper presents a new coastal high resolution Sea Level Anomaly (SLA) product, ALTICAP (ALTimetry Innovative Coastal Approach Product), derived from along track satellite altimetry. To enable as many coastal applications as possible, collocated altimetric significant wave height and wind data are also provided, as well as quality flags and the geophysical corrections applied to the SLA. Covering all ocean regions between 0 and 500 km from land, and between 66° S and 66° N, this dataset contains five years (February 2016 to July 2021) of 20 Hz altimetry measurements from the Jason-3 mission. The altimetric standards and geophysical corrections used to compute the SLA have been selected following a round robin study based on 22 of the most recent algorithms available. The processing solution adopted was a compromise between the capability of each algorithm to provide the best sea level solution over the entire strip between 0 and 200 km from the coast and a guarantee of product continuity in the future.

The comparison of ALTICAP and tide gauge SLA time series shows the ability of the ALTICAP product to capture the coastal sea level variability, with average correlation and root mean square deviation values of 0.74 and 9 cm respectively. On global average, altimetry SLA time series remain 80 % complete up to 9 km from the coast after editing. ALTICAP is the first global high resolution altimetry sea level product optimized for coastal applications and ensuring quality continuity up to the open ocean. The complete protocol followed during the round robin study (Birol et al., 2023), as well as all the results (https://www.aviso.altimetry.fr/en/data/products/sea-surface-height-products/global/altimetry-innovative-coastal-approach-product-alticap.html) and the data (LEGOS et al., 2023; doi: 10.24400/527896/a01-2023.020) are freely available online.