Evidence of sediment resuspension by island trapped waves

Six months of current and acoustic backscatter data from an acoustic Doppler current profiler (ADCP) moored in the shelf off Mallorca (Balearic Islands, Mediterranean Sea) were analyzed. The presence of island trapped waves (ITWs) was determined by correspondence of energetic subinertial peaks in the alongshore current spectra with theoretical wave modes. Although currents in this area averaged 0.06 m/s and rarely exceeded 0.5 m/s, an intense episode with currents larger than 1 m/s was observed between March 8 and 11, 2007. Our analysis demonstrates that ITWs generated by local wind forcing were responsible for such currents, causing significant sediment resuspension on those days. It is suggested that even moderate wind pulses can induce important resuspension along the shelf by generating ITWs. This could be an overlooked mechanism of coupling between atmospheric and shelf circulation with significant implications for sediment dynamics and biogeochemical cycles.