LAUSR

Abstract This study describes observations of non-tidal Superinertial Internal Waves (SIWs) for the first time in Jolucar Canyon, which is a short prototype canyon in the Alboran Sea (western Mediterranean). The analysis, based on current velocities and acoustic echo-amplitude signals, identified non-tidal SIWs and their vertical and temporal variability. Spectral analysis of the echo anomaly and the vertical component of velocity disclosed internal oscillations corresponding to a period of about 24–36 minutes (frequency band of 40–60 cpd). Power spectra Hovmoller diagrams derived from the wavelet amplitude of the echo anomaly and its vertical gradient at this frequency band showed that non-tidal SIWs were mainly found at 50 and 100 m depth, where stratification was strongest. This type of waves could be generated by the canyon walls, in the along-canyon direction. Remarkably, these submesoscale internal waves were not permanent and only observed during daytime. Based on similar observations in the Alboran Sea, it is hypothesized that this behaviour is induced by planktonic organisms, which may disrupt the water column structure during nighttime when they migrate to feed.