The ADCP uses the Doppler effect to measure the relative velocity between the instrument and scatterers in the ocean. The transducer emits acoustical energy out at 150 kHz in four beams. The echoes are reflected back up towards the ship and the ADCP records these return echoes. Echoes from shallow depths return sooner than the echoes from deeper depths. The ADCP sorts and averages the return echoes into separate depth bins.
Scientists determine the number of bins and size of bins based upon what they want to see.
The resulting ensemble averaged data provides the velocity of the water relative to the ship at specific depth bins. Since the ship and water are both moving, the ensemble averaged data must be processed to get to absolute velocities. By examining the absolute velocities, we have been able to identify several interesting features in the survey so far. Examination of the deeper circulation patterns suggest that deep currents enter Marguerite Bay and form 2 circulation cells. Meanders in the Antarctic Circumpolar Current on the edge of the shelf break are also identifiable.