Tidal motions and tidally induced fluxes through La Linea submarine canyon, western Alboran Sea

Detailed observations from two mooring lines deployed in La Linea submarine canyon, western Alboran Sea, are presented. This is a narrow canyon in the sense that its width is always less than the internal radius of deformatio n. Tidal currents within the canyon are polarized in the along-canyon direc tion according to its narrow nature. They have considerable amplitude (valu es of around 0.5 m/s are often observed) and are forced by the internal pre ssure gradients associated with the baroclinic tide that is generated in th e surroundings. Subsequent amplification of onshore baroclinic currents wit hin the canyon accounts for the large amplitude observed. Cross-shelf excha nge through the canyon due to tidal motions is different from zero despite the close to zero mean of tidal currents. The explanation is based on the a symmetry of water properties flowing up-canyon and down-canyon (some sort o f tidal rectification). Regarding the energy flux, the canyon seems to be a n adequate conduit to carry energy to the shore. Estimations made from our observations indicate that energy input onto the shelf per unit length para llel to the shore at the canyon head is enough to maintain mixing on the sh elf at intermediate depths.