title: Reconstructing surface ocean circulation with129I time series records from corals.
abstract: The long-lived radionuclide129I (half-life: 15.7 × 106yr) is well-known as a useful environmental tracer. At present, the global129I in surface water is about 1-2 orders of magnitude higher than pre-1960 levels. Since the 1990s, anthropogenic129I produced from industrial nuclear fuels reprocessing plants has been the primary source of129I in marine surface waters of the Atlantic and around the globe. Here we present four coral129I time series records from: 1) Con Dao and 2) Xisha Islands, the South China Sea, 3) Rabaul, Papua New Guinea and 4) Guam. The Con Dao coral129I record features a sudden increase in129I in 1959. The Xisha coral shows similar peak values for129I as the Con Dao coral, punctuated by distinct low values, likely due to the upwelling in the central South China Sea. The Rabaul coral features much more gradual129I increases in the 1970s, similar to a published record from the Solomon Islands. The Guam coral129I record contains the largest measured values for any site, with two large peaks, in 1955 and 1959. Nuclear weapons testing was the primary129I source in the Western Pacific in the latter part of the 20th Century, notably from testing in the Marshall Islands. The Guam 1955 peak and Con Dao 1959 increases are likely from the 1954 Castle Bravo test, and the Operation Hardtack I test is the most likely source of the 1959 peak observed at Guam. Radiogenic iodine found in coral was carried primarily through surface ocean currents. The coral129I time series data provide a broad picture of the surface distribution and depth penetration of129I in the Pacific Ocean over the past 60 years.
authors.affiliation: NSF-Arizona AMS Laboratory, University of Arizona, Tucson, AZ 85721, USA; Department of Geosciences, University of Arizona, Tucson, AZ 85721, USA. Electronic address: cchchang@email.arizona.edu.
authors.forename: Ching-Chih
authors.initials: CC
authors.lastname: Chang
authors.affiliation: NSF-Arizona AMS Laboratory, University of Arizona, Tucson, AZ 85721, USA; Department of Oceanography, National Sun Yat-Sen University, Kaohsiung, Taiwan.
authors.forename: George S
authors.initials: GS
authors.lastname: Burr
authors.affiliation: NSF-Arizona AMS Laboratory, University of Arizona, Tucson, AZ 85721, USA; Department of Geosciences, University of Arizona, Tucson, AZ 85721, USA.
authors.forename: A J Timothy
authors.initials: AJT
authors.lastname: Jull
authors.affiliation: Department of Geosciences, University of Arizona, Tucson, AZ 85721, USA.
authors.forename: Joellen L
authors.initials: JL
authors.lastname: Russell
authors.affiliation: NSF-Arizona AMS Laboratory, University of Arizona, Tucson, AZ 85721, USA.
authors.forename: Dana
authors.initials: D
authors.lastname: Biddulph
authors.affiliation: NSF-Arizona AMS Laboratory, University of Arizona, Tucson, AZ 85721, USA.
authors.forename: Lara
authors.initials: L
authors.lastname: White
authors.affiliation: US Geological Survey Pacific Coastal & Marine Science Center, Santa Cruz, CA 95060, USA.
authors.forename: Nancy G
authors.initials: NG
authors.lastname: Prouty
authors.affiliation: Department of Geosciences, National Taiwan University, Taipei, Taiwan.
authors.forename: Yue-Gau
authors.initials: YG
authors.lastname: Chen
authors.affiliation: Department of Geosciences, National Taiwan University, Taipei, Taiwan.
authors.forename: Chuan-Chou
authors.initials: CC
authors.lastname: Shen
authors.affiliation: Shaanxi Province Key Laboratory of Accelerator Mass Spectrometry Technology and Application, Institute of Earth Environment, CAS, Xi'an 710043, China.
authors.forename: Weijian
authors.initials: W
authors.lastname: Zhou
authors.affiliation: Institute of Geology, Vietnamese Academy of Science and Technology, Hanoi, Viet Nam.
authors.forename: Doan Dinh
authors.initials: DD
authors.lastname: Lam
mesh_terms: D000818:Animals; D037421:Anthozoa / Q000737:chemistry*; D006207:Half-Life; D007457:Iodine Radioisotopes / Q000032:analysis*; D062312:Islands; D008956:Models, Chemical; D054043:Nuclear Weapons; D010140:Pacific Ocean; D011834:Radiation Monitoring; D012623:Seawater / Q000737:chemistry; D014872:Water Movements; D014875:Water Pollutants, Radioactive / Q000032:analysis*
chemical_list: D007457:Iodine Radioisotopes; D014875:Water Pollutants, Radioactive
keywords: (129)I; Coral; Ocean mixing; Radioactive tracers; Surface ocean circulation