A glider equipped with a Conductivity Temperature Depth (CTD) and an echosounder traveled meridionally through a transect perpendicular to the coastline in the SE Bay of Biscay from September 23 to October 13, 2022. It surveyed the shelf-break, slope and open ocean areas from the surface to 200 m depth. The survey coincided with a strong 5-day storm, enabling the study of its effects on the upper water column hydrographic and hydrodynamic conditions, as well as on the small pelagics community. During the storm, surface currents were oriented towards the coast and this transport yielded the subduction of surface coastal waters in a process referred to as downwelling. After the storm, the hydrographic profiles depicted a gradual relaxation of the downwelling event, recovering the initial state after five days. This event was also monitored through a coastal upwelling index based on gap-filled high-frequency radar surface current data. The storm markedly decreased the salinity and temperature values in the upper water column, indicating the beginning of the transition regime from summer (stratified) to winter (mixed). Several of the transects covered by the glider coincided with those monitored (using trawls and acoustics) by a research vessel during the JUVENA survey, enabling comparisons for the validation of the glider observations. Moreover, the glider data before, during and after the storm are used to study the impact of the storm on small pelagic fish and vertebrate species observed at different depths in the area.

Primary Presenter: Ivan Manso-Narvarte, AZTI (imanso@azti.es)

Authors:

Ivan Manso-Narvarte, AZTI  (imanso@azti.es)

Anna Rubio, AZTI  (arubio@azti.es)

Asier Nieto, AZTI  (anieto@azti.es)

Guillermo Boyra, AZTI  (gboyra@azti.es)

Lohitzune Solabarrieta, AZTI  (lsolabarrieta@azti.es)

Irene Ruiz, AZTI  (iruiz@azti.es)

Pablo Lorente, Puertos del Estado  (plorente@puertos.es)

Jon Berregi, AZTI  (jberregi@azti.es)

Luis Cuesta, AZTI  (lcuesta@azti.es)

Beatriz Sobradillo, AZTI  (bsobradillo@azti.es)

Udane Martinez, AZTI  (umartinez@azti.es)

Ainhoa Caballero, AZTI  (acaballero@azti.es)