Abstract:
A joint acoustics and physical oceanography experiment was conducted in the winter of 1997 on the shell break and continental
slope south of New England in the Middle Atlantic Bight (figure 1). This experiment, Primer4, provided a seasonal contrast to the
previous summer Primer3 experiment and had the same goals and tasks: to study the thermohaline variability and structure of the
shelfbreak front and its effects on acoustic propagation. To accomplish the linked oceanographic and acoustic objectives of this
experiment, a combination of measurements (fig 2) were made. Seasoar hydrography, shipboard ADCP measurements, Satellite IR
sea surface temperature field observations, and AXT drops were employed to study the larger scale oceanographic fields. To study
the finer scale, which includes internal waves, a number of rapid-sampling thermistor strings and current meters, including a
moored, upward looking ADCP, were deployed. The acoustics components consisted of three 400 Hz tomography transceivers, a
224 Hz source and two hydrophone arrays. To study the geoacoustic parameters in the bottom a number of SUS charges were also
deployed. The field setup was approximately the same for both the summer 1996 and winter 1997 experiments; however the
weather conditions and the thermal structure of the mixed layer were radically different. This report is dedicated to the data from the
Winter 1997 Primer4 experiment.
