Analysis of the spatio-temporal sea level variability in extreme regions using in-situ and satellite remote sensing data: South Shetland region (Antarctica)

This thesis analyses sea level variability in the South Shetland Islands through the integration of satellite altimetry, long-term in-situ oceanographic observations, and the analysis of extreme geophysical events. The study provides new insights into the processes that drive polar coastal environments. The validation of Sentinel-3A and Sentinel-3B altimetric sea level anomaly products against tide gauge data showed that the agreement between satellite and in-situ measurements is highly sensitive to processing parameters and environmental conditions. Optimised settings, particularly the use of nine surroundig measurements to the crossover and a sea state bias correction of 5% of the significant wave height, yielded the lowest discrepancies with tide gauge records. Sea ice was identified as the main limitation for altimetry in the region, introducing data gaps and contaminating altimeter returns. These results highlight the importance of methodological refinement, including adaptive masking and improved retracking, to increase the robustness of polar altimetry. Temperature series from LIVMAR (Livingston Island) and DECMAR (Deception Island) stations revealed clear seasonal cycles modulated by local processes. Volcanic and tectonic activity, such as the 2020 Orca seamount activity, were associated with thermal anomalies, while glacier meltwater discharge was linked to earlier and more variable minima at Livingston. Three phases of thermal evolution were identified over the last decade, reflecting the combined effects of regional atmospheric variability and local geophysical forcing. In addition, the January 2022 Hunga Tonga–Hunga Ha’apai eruption generated atmospheric Lamb waves that were detected at Antarctic meteorological stations and triggered meteotsunamis at Livingston and Deception Islands. The responses at both sites highlight how atmospheric forcing generated long ocean waves that, once established, were shaped by local basin geometry in terms of amplitude and frequency. Overall, the results demonstrate that sea level variability in the South Shetland Islands is driven by the combined influence of large scale climatic factors, local volcanic and glacial processes, and extreme remote events. By integrating multiple approaches, this thesis contributes to reducing uncertainties in global sea level monitoring and to a more comprehensive understanding of sea level variability in this region of Antarctica.