Circulation of Circumpolar Deep Water and marine environment traced by 127 I and 129 I speciation in the Amundsen Sea Polynya, Antarctica

• Published in: Journal of Environmental Radioactivity
• Main Authors: Xing, Shan, Hou, Xiaolin, Shi, Keliang, Aldahan, Ala, Possnert, Goran
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2020
• Subjects: Amundsen sea polynya; Circumpolar Deep Water; Iodine species; Iodine-129; Marine environment; /dk/atira/pure/sustainabledevelopmentgoals/life_below_water; name=SDG 14 - Life Below Water; Antarctic; The Antarctic; Amundsen Sea; Antarc*; Antarctica; Antarctica Journal; Ice Shelf; Sea ice
• Online Access: https://orbit.dtu.dk/en/publications/c2776174-8ccb-434d-8c4a-2a0fd18ab87f; https://doi.org/10.1016/j.jenvrad.2020.106424; https://backend.orbit.dtu.dk/ws/files/221497751/Manuscript_R.pdf

The long-lived anthropogenic 129 I released from human nuclear activities has been widely employed as an effective oceanographic tracer to investigate circulation of water masses in marine environment. Depth profiles of seawater collected from the Amundsen Sea Polynya, Antarctica were analyzed for total 129 I and 127 I, as well as their species of iodide and iodate. The measured 129 I concentrations ((1.15–3.43) × 10 6 atoms/L) and 129 I/ 127 I atomic ratios ((0.53–1.19) × 10 −11 ) indicate that anthropogenic 129 I has not only reached the Antarctic surface marine environment but also the deep water due to a strong vertical mixing of water masses. The Circumpolar Deep Water (CDW) flowed southward along continental shelf towards the ice shelf zone (74.25°S) at a depth of 1025 m and then migrated upward and northward to the polynya and finally to the sea ice zone (71.95°S). The maximum upwelling depth of the CDW was around 200 m in the polynya. The source of 129 I − in the polynya is predominantly the intrusion of source waters rather than the in-situ reduction of iodate by phytoplankton, implying a considerably slow reduction process of iodate to iodide in this region.