Present wave climate in the Bay of Biscay: spatiotemporal variability and trends from 1958 to 2001

Elodie Charles (1) , Déborah Idier (1) , Jérôme Thiebot (1) , Gonéri Le Cozannet (1) , Rodrigo Pedreros (1) , Fabrice Ardhuin (2) , Serge Planton (3)

1 BRGM - Bureau de Recherches Géologiques et Minières (BRGM)
2 LOS - Laboratoire d'Océanographie Spatiale
3 CNRM - Centre national de recherches météorologiques

Climate change impacts on wave conditions can increase the risk of offshore and coastal hazards. The present paper investigates wave climate multi-decadal trends and inter-annual variability in the Bay of Biscay during the past decades (1958-2001). Wave fields are computed with a wave modelling system based on the WAVEWATCH III code and forced by ERA-40 reanalysis wind fields. It provides both an extended spatiotemporal domain and a refined spatial resolution over the Bay of Biscay. The validation of the wave model is based on eleven buoys, allowing the use of computed wave fields in the analysis of mean and extreme wave height trends and variability. Wave height, period and direction are examined for a large array of wave conditions (by seasons, high percentiles of wave heights, different periods). Several trends on recent periods are identified, notably an increase of summer significant wave height, a southerly shift of autumn extreme wave direction and a northerly shift of spring extreme wave direction. Wave fields exhibit high inter-annual variability, with a normalized standard deviation of seasonal wave height greater than 15% in wintertime. The relationship with northern hemisphere teleconnection patterns is investigated at regional scale, especially along the coast. It highlights a strong correlation between local wave conditions and the North Atlantic Oscillation and the East Atlantic pattern indices. This relationship is further investigated at local scale with a new method based on bivariate diagrams, allowing the identification of the type of waves (swell, storm, intermediate waves) impacted. These results are discussed in terms of comparison with previous studies and coastal risk implications.

Domaines: Océanographie

Elodie Charles, Déborah Idier, Jérôme Thiebot, Gonéri Le Cozannet, Rodrigo Pedreros, et al.. Present wave climate in the Bay of Biscay: spatiotemporal variability and trends from 1958 to 2001. Journal of Climate, 2012, 25 (6), pp.2020-2039. ⟨10.1175/JCLI-D-11-00086.1⟩. ⟨hal-00647448⟩