Water Circulation and Marine Environment in the Antarctic Traced by Speciation of ¹²⁹I and ¹²⁷I

Emissions of anthropogenic ¹²⁹I from human nuclear activities are now detected in the surface water of the Antarctic seas. Surface seawater samples from the Drake Passage, Bellingshausen, Amundsen, and Ross Seas were analyzed for total ¹²⁹I and ¹²⁷I, as well as for iodide and iodate of these two isotopes. The variability of ¹²⁷I and ¹²⁹I concentrations and their species (¹²⁷I⁻/¹²⁷IO₃ ⁻, ¹²⁹I⁻/¹²⁹IO₃ ⁻) suggest limited environmental impact where ((1.15–3.15) × 10⁶ atoms/L for ¹²⁹I concentration and (0.61–1.98) × 10⁻¹¹ for ¹²⁹I/¹²⁷I atomic ratios are the lowest ones compared to the other oceans. The iodine distribution patterns provide useful information on surface water transport and mixing that are vital for better understanding of the Southern Oceans effects on the global climate change. The results indicate multiple spatial interactions between the Antarctic Circumpolar Current (ACC) and Antarctic Peninsula Coastal Current (APCC). These interactions happen in restricted circulation pathways that may partly relate to glacial melting and icebergs transport. Biological activity during the warm season should be one of the key factors controlling the reduction of iodate in the coastal water in the Antarctic.