Low‐frequency sound attenuation in the Labrador Sea‐Baffin Bay region

A series of long range propagation runs were analyzed to determine attenuation coefficients for the frequency range 25–1000 Hz. Above 200 Hz, the dominant cause of attenuation was boron absorption; below 200 Hz, the attenuation was independent of frequency indicating a scattering mechanism as the cause. In the Labrador Basin, absorption was close to that predicted by the Thorp formula; in the Davis Strait and Baffin Bay, it was significantly higher (1.3–1.5 Thorp). This increase, corresponding to higher pH values, can be attributed to two possible causes, the influence of the oxygen‐rich Labrador current and the higher pH values encountered as the sound channel axis shallows. The frequency independent component was similar in the Labrador Sea and Davis Strait but lower in Baffin Bay confirming results reported earlier [R. H. Mellen et al., J. Acoust. Soc. Am. 57, 1201–1202(L) (1975)] and suggesting less scattering in Baffin Bay. (Work supported by NUSC)