ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

1pAO8. Large-scale circulation and variability in the northwest Atlantic as determined by long-range reciprocal acoustic transmissions.

David B. Chester

Peter F. Worcester

Bruce D. Cornuelle

Scripps Inst. of Oceanogr., Univ. of California at San Diego, La Jolla, CA 92093

Brian D. Dushaw

Univ. of Washington, Seattle, WA 98105

Reciprocal acoustic transmissions are analyzed to determine the general circulation of the region between Bermuda and Puerto Rico. Six tomographic transceivers were moored from March 1991 to March 1992 in the region centered at 25(degrees)N, 66(degrees)W during the Acoustic Mid-Ocean Dynamics Experiment (AMODE). Large-scale range averages (over 300 to 700 km sections) of temperature and velocity and large-scale areal averages of relative vorticity have been estimated through inversion of tomographic travel time data. The barotropic and first baroclinic mode are well resolved by the acoustic sampling, with poorer resolution of the second baroclinic mode. The 300-day mean circulation of the region indicates a band of westward flow of a few cm/s in the surface and thermocline waters. An active and resolvable mesoscale eddy field is present, with variability typically dominated by motions with spatial scales of 100--200 km, and with a general westward drift of mesoscale eddy features. The tomographic observations have been combined with a quasi-geostrophic numerical ocean model to further investigate eddy kinematics in the region. The model is used both to evaluate the evolution of the barotropic and baroclinic flow field, and to illustrate the utility of tomographic data for constraining a quasi-geostrophic model. [Work supported by ONR.]