ASA 126th Meeting Denver 1993 October 4-8

2aAO1. The fine scale oceanography of the Arctic Ocean: Doppler acoustic studies.

Robert Pinkel Mark Merrifield

Marine Phys. Lab., Scripps Inst. of Oceanogr., La Jolla, CA 92093

Focus is on fine-scale studies of the upper Arctic Ocean using a variety of Doppler sonars constructed at the Marine Physical Laboratory. From two Spring experiments in the Beaufort Sea (AIWEX, 1985; LEADEX, 1992), considerable insight has been gained into the climatology of the internal wave field. The most energetic constituents of the wave field, near inertial currents, have very different amplitudes and scales than at lower latitudes. The generation of these waves below the ice and lead-covered surface is considered as a possible factor for their unique characteristics in the Arctic. In order to map the current field below an Arctic lead, a sector-scan Doppler sonar has been developed. Using beamforming techniques, the sonar resolves acoustic backscatter and current speed along 28 contiguous beams with an angular resolution of 1.5(degrees). The sonar was deployed at two leads during the LEADEX experiment. Observations were obtained from a 45(degrees) vertical fan directed normal to the lead axis. In these leads, convection associated with atmospheric cooling did not modify strongly the background velocity field. However, a clear increase in acoustic backscatter was detected just below the base of the mixed layer, possibly associated with convective processes.