Global warming impact on low frequency acoustic propagation in Pacific Ocean equatorial surface ducts: a potential paradox.

A typical Pacific Ocean pH profile has a value of 8.1 at the surface decreasing to 7.7 at the axis of the SOFAR channel (400m). Absorption in seawater of low frequency sound is pH dependent, so that the low frequencies that are contained in a surface duct will be absorbed at twice the rate of those in the SOFAR channel. Global warming is producing ocean acidification which is reducing the pH, hence the low frequency sound absorption, and this will first impact the surface duct. But global warming is also predicted to increase the rainfall and as these equatorial surface ducts are produced from monsoon conditions, the suface duct would be deepened and thus expand the low frequencies contained in it, which would now be absorped at a higher rate than in the SOFAR channel. This is just a first look into one aspect of what may prove to be a multifaceted and complex interaction of global warming on acoustic propagation conditions in the ocean.