Preprints
https://doi.org/10.5194/egusphere-2025-3558
https://doi.org/10.5194/egusphere-2025-3558
10 Oct 2025
 | 10 Oct 2025
Status: this preprint is open for discussion and under review for Natural Hazards and Earth System Sciences (NHESS).

Projections of changes in extreme storm surges for European coasts using statistical downscaling

Maialen Irazoqui Apecechea, Angélique Melet, Melisa Menendez, Hector Lobeto, and Jonathan B. Valle-Rodriguez

Abstract. Understanding future changes in extreme storm surges (ESSs) is critical for coastal risk assessment and adaptation. However, existing projections in Europe are often based on computationally expensive dynamical models, limiting ensemble sizes and thus confidence in projected changes. In this study, we develop a cost-effective statistical downscaling model (SDM) trained to replicate dynamically downscaled storm surges, enabling the generation of a pan-European ensemble of ESS projections based on 17 global climate models (GCMs) – substantially expanding previous efforts.

The SDM is trained on a storm surge hindcast and demonstrates stable skill across historical and future climates, effectively capturing projected ESSs changes given by dynamical simulations. Ensemble projections reveal robust multi-model mean (MMM) changes in the 10-year return level (RL10) of ESSs by 2100. Negative MMM changes are identified in the Mediterranean Sea (−7 %), Moroccan Atlantic coast (−10 %), and Danish Straits (−6 %), while positive changes of around +6 % are projected for the Celtic and Irish Seas, western Denmark, and the Gulf of Finland. Despite these robust signals, inter-model spread is substantial, with likely ranges (17th–83rd percentiles) extending from −25 % to +17 % across Europe, and changes of up to ±35 % in individual models. The southern North Sea and northern Baltic Sea emerge as low-confidence regions, marked by particularly strong inter-model spread. Higher return levels (e.g., 100-year) show larger changes but increased uncertainty.

Our results underscore the importance of extended ensembles in projecting ESSs in Europe and demonstrate the value of statistical models for applications that demand extensive simulations – such as climate projections based on large ensembles, multi-scenario climate analyses, and detection and attribution studies – which can complement computationally expensive traditional dynamical downscaling methods.

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Maialen Irazoqui Apecechea, Angélique Melet, Melisa Menendez, Hector Lobeto, and Jonathan B. Valle-Rodriguez

Status: open (until 21 Nov 2025)

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Maialen Irazoqui Apecechea, Angélique Melet, Melisa Menendez, Hector Lobeto, and Jonathan B. Valle-Rodriguez
Maialen Irazoqui Apecechea, Angélique Melet, Melisa Menendez, Hector Lobeto, and Jonathan B. Valle-Rodriguez
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Latest update: 10 Oct 2025
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Short summary
We applied a fast statistical model to estimate future extreme storm surges in Europe using data from 17 climate models – about twice as many as in past studies. Results show robust regional patterns – decreases in the Mediterranean and Moroccan coast, increases in the Irish Sea and Gulf of Finland – with high uncertainty in other areas. Out results increase our knowledge on future storm surge uncertainties, needed for informed coastal planning.
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