Abstract
In general, enclosed coastal seas are more liable to eutrophicate owing to the reduced exchange of water. This study investigates the relationship between the water exchange index (Damping Ratio) and the enclosed index. The enclosed index is a measure of the degree of encloser in sea regions. The differences between the enclosed index values in sea regions where anoxic water masses occur and those in sea regions of nonoccurrence are also investigated. The results of the analysis indicate the sea regions which are subject to entrophication based on bay topography generally have an enclosed index value of 1.0 or greater. However, in selecting the sea regions it is thought to be necessary to also give consideration to other characteristics of sea regions such as the existence of eddies, thermocline intensity, submarine topography (existence of caldron) and so on. And, regional differences of the occurrence sea regions of anoxic water masses in Japan seem to be related to a finding which many enclosed coastal seas exist rather the southern district than the northern one of Japan.
