On the observability of internal tidal waves in remotely-sensed ocean colour data

This paper reveals bands of enhanced levels of near-surface chlorophyll in the central Bay of Biscay in remotely-sensed images from the SeaWiFS ocean colour sensor, and shows that these are most probably associated with the crests of internal tidal waves travelling away from the shelf break. We are able to explain this effect as likely to result from the uplifting of a subsurface chlorophyll maximum by the passing internal tides, to such a level as may be “seen” by the satellite sensor, and have quantified the effect with a simple model. We believe this is the first time that internal tidal waves have been reported as having a direct and observable effect in such remotely-sensed ocean colour images.