Regional Characteristics for Interpreting Inverted Echo Sounder (IES) Observations

Abstract

Changes in round-trip acoustc travel time (τ) measured between a bottom moored inverted echo sounder and the sea surface can be interpreted as changes in dynamic height (D) with suitable calibration information. The τ, D, and isotherm and isopycnal depths (Z) have been calculated using hydrographic (CTD) data from three regions: the Norwegian Current, the Sargasso Sea and the eastern Gulf Stream. Regressions of D and Z on τ were performed. The slope for the Norwegian Current is − 1.70 ± 0.01 [dyn cm (m s)⁻¹], for the Sargasso Sea − 3.89 ± 0.16 [dyn cm (m s)⁻¹] and for the Gulf Stream − 3.13 ± 0.07 [dyn cm (m s)⁻¹]. The quasi-random scatter about regression curves is found to be primarily the result of variability in the seasonal thermocline, where present.