The effect of thermohaline steps on range‐dependent acoustic propagation near the northeast coast of South America using high resolution data

Abstract

The effects of large thermohaline steps on acoustic transmission loss (TL) for a range‐independent sound velocity profile (SVP) near the northeast coast of South America were reported [Chin‐Bing and King, J. Acoust. Soc. Am. Suppl. 1 76, S84 (1984)] using a high resolution SVP (in depth), a discrete standard depth SVP, and a depth thinned SVP. The thermohaline step structure created adjacent regions of near isovelocity connected by a high gradient small transition region; this “step” structured SVP affected the TL even at low frequencies. The study is now extended to include recent experimental high resolution range‐dependent thermohaline data. Range‐dependent TL comparisons are made using SVPs obtained from (1) the high resolution data, (2) an oceanographic forecast model, (3) discrete standard depths, and (4) a depth thinned profile. This range‐dependent study supports the basic finding from the range‐independent study—TL structure can be adversely affected by failing to include the detailed SVP step structure. Furthermore, oceanographic forecasts models that provide SVPs need a high degree of accuracy in regions where these vertical anomalies exist.