[AOS09-P16] From the Luzon Strait to the Tsushima Strait: Water masses and nutrient transports approached using 137Cs
Keywords:137Cs, subtropical mode water, water masses, KIW, nutrients
Data and water samples were collected during the Hakuho-Maru KH-17-5 Cruise and the Nagasaki-Maru 464 Cruise in November and July 2017, respectively. Data from the KH-17-5 Cruise was used for the study of the area around the Luzon Strait and those of the Nagasaki-maru 464 Cruise was used for the study of area around the outer shelf region of the East China Sea and the Tsushima Strait. The 137Cs active concentration was analyzed by γ-Ray spectrometry after preconcentration. The turbulence intensity was measured using TurboMAP and VMP2000.
The maximum 137Cs concentration shows the existence of the subtropical mode water (STMW) in the Luzon Strait, the ECS and the Tsushima Strait, respectively, at the similar density (25.2-25.7 kg/m3), temperature (15-17℃) and salinity (34.60-34.75). Although their depth changes from 400 m in the Luzon Strait to 150 m at the shelf edge of the ECS and 100m in the East Channel of the Tsushima Strait, they can all be identified as the KIW because of the similar density. It is noteworthy that around Luzon Strait, the distribution of 137Cs is influenced by strong vertical mixing. The percentage of nutrients transported to the Sea of Japan by KIW is estimated and this is meaningful to the ecosystem of the Sea of Japan.