Potential impact of global warming on sound propagation in monsoon induced surface mixed layers

Abstract

Acoustic surface ducts in mixed layers can be an important mode of sonar propagation. The precipitation from monsoons seasonally create mixed surface layers near the equator in every major ocean. Although not as robust as mixed layers that occur at higher latitudes, they may provide the best examples of the possible global warming impact on sound propagation. This would include acoustic duct propagation properties such as attenuation, surface loss, cutoff frequency, and ambient noise. This is just a first attempt, based on preliminary estimates, to evaluate possible change. To be considered are direct effects such as ocean acidification and warming water; the seasonal impact on monsoons, like greater precipitation and duration; and finally individual transient events such as storm intensity and number (including typhoons). Given the usual monsoon variability, it may be challenging to sort out changes, but monsoon duct acoustics may be a promising new area for investigators.