The behavior of CO2 in coastal seas has been less extensively studied than in open oceans. In this study, we examined the spatial characteristics of pCO2 (partial pressure of CO2 in seawater) based on measurements taken from the Seto Inland Sea, with a focus on regional characteristics. Across all regions, pCO2 levels were lower in spring than in summer, with an average difference exceeding 100 µatm, suggesting sea temperature-related influences. During summer, pCO2 characteristics varied between the strait and non-strait regions. In Osaka Bay, pCO2 was consistently lower during both seasons, likely due to considerable CO2 uptake driven by high primary production. In most straits, summer pCO2 levels were higher than in adjacent non-strait regions, with an average difference of approximately 64 µatm. This suggests that high-pCO2 water masses, formed through organic matter decomposition in the lower stratified layers flowed horizontally into nearby straits and were subsequently transported to the surface through vertical mixing. In spring, CO2 was absorbed across all regions, whereas in summer, most regions of the Seto Inland Sea experienced CO2 emission. The interconnected structure between the straits and Bay-Nada areas contributes to seasonal variations in CO2 absorption and emission.
Fujita M., Hayashi M., Yamashita E. & Hirokawa S., 2024. Spatial characteristics of the partial pressure of carbon dioxide in seawater in the Seto Inland Sea and surrounding waters. Oceanography in Japan 33: 77-87. Article.
