Analysis of sound propagation in the front region off the east of Tsugaru straits

Abstract

Off the east of Tsugaru straits, located in the north of the main-island, there are three big water masses. One is the Oyashio (Kuril current) that is a cold water mass. Other water masses are the warm water masses: the Tsugaru warm current, and Kurosio extension. And, the Tsugaru warm eddy is made from the Tsugaru warm current on the Oyashio. Therefore, the front is generated in the region to which those water masses bound. The temperature structure changes rapidly in that region. In addition, the bottom depth is changed too. Then, bi-directional sound propagation is analyzed on the line of a right-angled direction to the front that Tsugaru warm eddy is bounded to the Oyashio. It is considered about the sound propagation of 220 km that passes the front from the Tsugaru warm eddy to the Oyashio cold water mass, and the opposite path. In the front region, the sound propagation is changed, and suffers the impact of the bottom at the same time. Therefore, the propagation configuration is different in the bi-directional propagation. The transmission loss in the Tsugaru warm eddy was large when the sound source crosses the front from the Oyashio.