Sound absorption in sea water by a third chemical relaxation

Evidence is presented for a third chemical relaxation producing sound absorption in the ocean. After accounting for sound absorption in the Atlantic and Pacific due to boric acid, magnesium sulfate, and water, there appears to be a third relaxation at 3 kHz (possibly higher) with αλ_max=0.26×10⁻⁵ at 4°. The existence of this relaxation was determined by using the Fisher–Simmons equation for sound absorption based on Simmon’s laboratory work. For the Pacific data, the boric acid contribution was reduced to 0.44 that of the Atlantic. The third relaxation was deduced initially from the shot data of Morris (50–400 Hz) and the cw data of Lovett (750, 1500, and 3000 Hz) in the Pacific Ocean at about 30° N. The third relaxation is consistent with the Atlantic Ocean data of Thorp. The new relaxation may be the one predicted by Garland, Patel, and Atkinson for MgHCO₃ for which αλ_max=0.58×10⁻⁶ at 9 kHz at 25°.