SO_SLICE: a 19-year gridded sea level anomaly dataset for the open and ice-covered Southern Ocean (2003–2021)

Abstract

Abstract. Sea Level Anomalies (SLA) in the Southern Ocean remain poorly observed due to sea ice, which hampers conventional satellite altimetry. Recent advances in lead-based retracking techniques have enabled SLA estimates within ice-covered regions. However, existing datasets are temporally limited, with most available products covering periods shorter than 10 years. Here, we present SO_SLICE (Southern Ocean Sea Level in Ice Conditions Estimate), a 25 km × 25 km gridded SLA dataset spanning ice-free and ice-covered areas of the Southern Ocean from 2003 to 2021. It is available at https://doi.org/10.5281/zenodo.17467407 (Mosneron Dupin et al., 2025). This 19-year dataset provides the longest temporal SLA coverage currently available across the whole Southern Ocean. It is produced by processing along-track measurements from four satellite missions: Envisat, CryoSat-2, SARAL/AltiKa, and Sentinel-3A. It relies on retrieving observations from openings in the sea-ice cover. The product shows continuous transitions across the sea-ice edge, with a mean formal mapping error of 1.3 cm in the subpolar Southern Ocean. The gridded fields have an effective spatial resolution of 200 km south of 65° S, mainly constrained by the input correlation length scales. SO_SLICE captures variability at periods longer than 30 d. Comparison with independent in situ observations yields mean correlation coefficients of 0.58 with tide gauges and 0.66 with bottom pressure recorders. Overall, SO_SLICE fills a key observational gap and offers new opportunities to study trends and interannual variability in sea level and ocean circulation in the Southern Ocean, particularly during sea-ice coverage.