Using coherent ambient sound to probe the ocean

Abstract

Climate change is rapidly changing our oceans at faster time scales than have previously happened in 's history. Robust, full ocean observing systems are required for us to understand these changes and their consequences on the entire system. This work presents continued progress in the development of technologies that can utilize sound in the ocean as a tool to observe oceanographic variables, such as temperature. Coherent sound in the ocean contains information about the environment that it propagates in, and it is possible to use measured sound propagation to extract this information. Specifically, the sound speed of water is almost fully determined by the temperature of the water and measuring the sound speed of the ocean can result in robust measurements of ocean temperature. This work explores two methods of measuring acoustic propagation for the ultimate goal of oceanographic observations. The first utilizes coherent ambient sound, such as wind generated surface noise, to estimate sound propagation, and it is shown that these acoustic measurements can be utilized to estimate water column temperature. The second method uses a transmitted low frequency signal that is received across ocean basins. It is shown that this source can be received by various single hydrophones and has the potential to be used for future observations of ocean temperature.