[AOS09-P04] Investigation of the relationship between salinity and stable oxygen isotope of surface seawater based on high resolution δ18O mapping in Tsushima warm current area and the Sea of Japan
Keywords:the Sea of Japan, seawater, stable oxygen isotope, salinity, Tsushima warm current
Seawater samples used for the study were sampled at more than 100 stations by using a bucket or a pump on the ship, from 2015 to 2017, in the East China Sea and the Sea of Japan (30 - 43 degrees north latitude: 124 - 140 degrees east longitude).
For the analysis, δ18Osw and δDsw were determined by using a cavity ring-down spectroscopy stable isotope ratio analyzer (CRDS: Picarro L2130-i) and a customized continuous-flow stable isotope ratio analytical system (Headspace CO2 equilibrium method: MICAL3c + IsoPrime). Salinity was measured using a sensor calibrated with Autosal or Autosal.
The relation of δ18Osw-salinity obtained in this study was roughly in agreement with the previous studies on the Tsushima warm current area. The slope of the relational expression was slightly different between the East China Sea and the Tsushima Strait. Furthermore, as a result of detailed comparison in the eastern part of Tsushima Strait, intercepts of relational expression were different between the middle of the Sea of Japan, Tsushima Strait and Toyama Bay. These results indicate that there will be the possibility that the δ18Osw-salinity relationship differs among each sea areas. In this study, we will also discuss the d18Osw data of seawater sampled after the autumn of 2017 for each area.
Hereafter, we plan to proceed with seawater sampling for δ18Osw with high temporal-spatial resolution (e.g. vertical sampling in water column and seasonal sampling) in the East China Sea - the Sea of Japan to detect the characteristics of δ18Osw variations. The findings obtained are expected to bring us important information to discuss related studies, for example, elucidation of migration history of fish based on δ18Osw analysis of fish otoliths, and formation process of Japan Sea proper water.