Presentation Information
[20a-A310-2]Iodine isotopes track the iodine cycling in the Beaufort, Chukchi, and Bering Seas
〇(P)Yuanzhi Qi1, Qiuyu Yang1, Takeyasu Yamagata1, Hisao Nagai1,2, Yuichiro Kumamoto3 (1.The Univ. of Tokyo, 2.Nihon Univ., 3.JAMSTEC)
Keywords:
Iodine-129,Speciation analysis,Arctic Ocean
In this study, we present our observations regarding the concentrations of different iodine isotopes (127I and 129I) encompassing total iodine (TI), iodide, and iodate in seawater samples. Two depth profiles were collected in the Beaufort Sea, along with an additional collection of 15 surface seawater samples obtained from the Beaufort, Chukchi, and Bering Seas between 12 August and 6 October 2022. At different ocean depths, the distribution of iodine is controlled by a variety of water masses, such as Pacific water, Atlantic water, and freshwater. In the surface ocean, the salinity and iodine speciation analysis results can clearly distinguish the Beaufort Sea from the other two seas, and in different sea areas, the isotopic characteristics of different iodine species were significantly correlated with salinity. Considering the three large rivers (Mackenzie, Yukon, and Kuskokwim) injected into the study area, we can reasonably speculate that rivers are the key factors affecting the iodine circulation and distribution in the surface ocean of this region. The Arctic intermediate water contained iodine isotopic signatures consistent with those of the North Atlantic. The upper ocean was dominated by the net reduction from iodate to iodide due to the biological activities of phytoplankton, while the net oxidation from iodide to iodate is mainly in the intermediate and deep ocean. Simulation of iodine cycling based on isotopic signatures of different iodine species revealed the presence of the reduction process from iodate to iodide and the iodide input from sediments to seawater in Arctic intermediate water. Our study indicates that iodine-129 can provide essential and detailed information for the iodine cycling study.