Towards a multi-product methodology for calculating the ocean monitoring indicator of SST extremes in the IBI region

The ongoing evaluation and refinement of the Copernicus Ocean Monitoring Indicators (OMIs) is essential to ensure their scientific robustness and operational relevance. This process takes place within a context of continuous advances in upstream products and the need to adapt methodologies to evolving scientific priorities and decision-making requirements. In this framework, the release of new Copernicus products and the growing demand for quantifying uncertainty in indicator results are particularly relevant. Among the operational OMIs produced by the Iberia–Biscay–Ireland (IBI) Monitoring and Forecasting Center is the Sea Surface Temperature (SST) extremes indicator, which assesses the intensity of extreme thermal events in the region. This study proposes two methodological improvements to it: first, replacing the near real-time data product currently used to compute the indicator with the recently developed Interim extension of its multi-year counterpart; and second, exploring the use of a multi-product ensemble approach that integrates regional and global model outputs with satellite-based observations to provide a first-order measure of inter-product spread. The methodology focuses on comparing the 2024 SST extremes OMI, computed using the existing approach, with outputs generated by the revised methodologies. The evaluation uses the observationally based SST extremes OMI as a reference (currently available in the Copernicus Marine catalog), and the analysis examines spatial patterns and local behaviors, highlighting consistencies and discrepancies across products. The results show that both the Interim dataset and the multi-product approach improve the robustness and consistency of the SST extremes indicator. While the Interim dataset enhances internal coherence by reducing heterogeneity in data sources, the ensemble method provides a more reliable assessment by incorporating inter-product spread information. Together, these advances strengthen the scientific maturity and operational value of SST extremes monitoring in the IBI region.