Abstract
This study investigated the interaction with water masses from the distribution of Iodine-129, Cesium-134, and Cesium-137 in the eastern area off Cape Shiriya, Aomori prefecture. Iodine-129, Cesium-134, and Cesium-137 concentrations in water samples collected in July 2012 were 13.7-30.2 nBq/L, N.D.-5.45 mBq/L, and 0.79-9.44 mBq/L, respectively. Concentrations of these radionuclides at the 25.5-26.7 isopycnal (σt) increased above the environmental levels before the Fukushima Daiichi nuclear accident, and their increase depended on a formation process of water masses. It is considered that concentrations at the 25.9-26.0 σt were increased by mixing the Tsugaru Warm Current Water System with near-surface water in the Oyashio region, but concentrations at the 26.4 σt were increased by mixing the Tsugaru Warm Current Water System with the Kuroshio-Oyashio mixed water.
