ASA 126th Meeting Denver 1993 October 4-8

2aAO3. Observations of acoustic scattering associated with ocean microstructure in the Arctic.

Albert J. Plueddemann

Woods Hole Oceanogr. Inst., Woods Hole, MA 02543

Laurie Padman

Oregon State Univ., Corvallis, OR

Timothy P. Stanton

Naval Postgraduate School, Monterey, CA

Jeffrey T. Sherman Robert Pinkel

Scripps Inst. of Oceanogr., La Jolla, CA

Observations from an Arctic ice camp on the Northwest flank of the Yermak Plateau indicate that under some conditions ocean microstructure may be detectable with ``standard'' acoustic instrumentation (i.e., acoustic Doppler current profilers) of moderately high frequency (150--300 kHz). The data set, collected during the Cooperative Eastern Arctic Experiment (CEAREX), includes simultaneous observations of kinetic energy dissipation rate, temperature dissipation rate, and acoustic backscatter from both 160- and 300-kHz Doppler profilers. The turbulence levels observed during CEAREX were particularly strong ((epsilon)>10[sup -7] W kg[sup -1]) and occurred in well-defined patches. Patches in the mixed layer were not associated with backscattered intensity anomalies. However, intensity anomalies of 2 to 6 dB were found to be coincident in time and space with the patches of strong turbulence in the thermocline. The acoustic intensity anomalies were intermittent, presumably because they were detectable only above a threshold that represented the background particulate scattering level. Theoretical predictions of the acoustic intensity level based on the microstructure measurements are used to support the hypothesis that the enhanced scattering levels are due to temperature microstructure rather than variations in particulate scattering.