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IEECAS Utilizes Speciation of 129I and 127I to Trace Water Circulation and Marine Environment in the Antarctic
author: source: Time:2017-09-05 font< big medium small >

The Antarctica and the Southern Ocean play profound roles on the response to global climate system. The Southern Ocean currents are effective transmission channels of heat and nutrients and intensively affect the ecosystem of the Southern Ocean, and vital to trace the regional water gyres and circulations. 129I is a naturally generated isotope, but anthropogenic releases are the dominated source of 129I in the present environment. Due to uniqueness of 129I resources and the relatively long residence time of iodine (~300 ky) compared with the water turn over time (~1000 y) in the ocean, 129I is a useful tracer for investigation of ocean circulation and water mass exchange.
It is introduced by the team leader, Professor HOU Xiaolin, this study aims to understand the levels and distribution of iodine species (129I and 127I) in the surface seawater in the Antarctic sector. The results suggest that much of 129I in Antarctic surface seawater originates from fallout of atmospheric nuclear weapons tests in the Marshall Islands in 1950s through ocean currents transport along the South Pacific. In addition, the 129I released from these weapons tests (2.1-5.1 kg) is an important source of 129I in the Southern Hemisphere seawaters.
According to the concentrationof iodine isotopes, the Antarctic water system has been figured out (Fig.1). The Antarctic waters system studied in this work are mainly composed of two opposite currents of the Antarctic circumpolar current (ACC) and the Antarctic Peninsula Circulation (APCC). Level and distribution of iodine isotopes and their species have revealed that the eastward following ACC has 6 southward moving branches at the 67.96°W, 75.71°W, 113.19°W, 126.45°W, 143.1°W and 173.7°W, respectively. The eastwards moving ACC and westwards moving the APCC interact with each other through their branches in opposite directions, forming numerous discontinuous and closed and/or unclosed gyres in-between them. These interactions happen in restricted circulation pathways that may partly relate to glacial melting and iceberg transport and complicated submarine topography.

This work has been published on the Scientific Reports.

 


Fig.1 Distribution of 129I (106 atoms/L) along the transect suggested surface sea current pathways (dashed arrows). (Image by Xing, et al) 

Contact: HOU, Xiaolin, houxl@ieecas.cn, State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Cademy of Sciences, Xi’an 710061, China

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