Gas Bubbles as Oceanographic Tracers

Abstract Air bubbles can be used as oceanographic tracers that indicate the strength of a downwelling current by which they are subducted. In a tidal front in the Fraser Estuary, British Columbia, Canada, vertical currents of up to 0.70 m s−1 subduct bubbles to depths of more than 160 m. Echo sounder measurements are compared with simultaneous ADCP current measurements and are interpreted with a bubble model by S. A. Thorpe, yielding an estimate of the vertical current that carries the bubbles to the depth of measurement.