Teleconnection Pattern influence on sea wave climate in the Bay of Biscay

Gonéri Le Cozannet (1) , Sophie Lecacheux (1) , Etienne Delvallée (1) , Nicolas Desramaut (1) , Carlos Oliveros (1) , Rodrigo Pedreros (1)

1 BRGM - Bureau de Recherches Géologiques et Minières (BRGM)

The potential modification of hydrodynamic factors such as waves is a source of concern for many coastal communities because of its potential impact on shoreline evolution. In the northern Atlantic, swell is created by storm winds that cross the Atlantic following west-east tracks. These tracks are shifted more southward or northward depending on the season and on recurring large scale atmospheric pressure anomalies, also called teleconnection patterns. This study investigates the trends of sea wave patterns in the Bay of Biscay and relates their interannual variability to teleconnection patterns. Sea wave parameter time series from the ERA-40 reanalysis from the ECMWF show a satisfying correlation with an in-situ buoy of Meteo-France during the time period they overlap. Using a K-Means algorithm, data from this 44-year long time series were clustered into a few sea state modes, each of them corresponding to an observable sea state associated with an averaged value for wave height, period and direction. This analysis shows that most of the increase in annual mean sea wave height since the 1970's is due to the fact that the relative frequency of occurrence of persistent observable sea states is evolving over the time: from 1970 to 2001, the data indicate that energetic north-west swell become more frequent than low energy intermediate sea states. Moreover, anomalies of the relative frequency of occurrence of observable sea states are related to large scale recurring pressure anomalies: principally the Northern Atlantic Oscillation (NAO), but also (during winters) the East Atlantic pattern (EA), as well other teleconnection patterns of the northern hemisphere (NOAA data).

Domains: Earth Sciences

Gonéri Le Cozannet, Sophie Lecacheux, Etienne Delvallée, Nicolas Desramaut, Carlos Oliveros, et al.. Teleconnection Pattern influence on sea wave climate in the Bay of Biscay. Journal of Climate, 2011, 24, p. 641-652. ⟨10.1175/2010JCLI3589.1⟩. ⟨hal-00640021⟩