Tracing Atlantic water transit time in the subarctic and Arctic Atlantic using 99Tc-233U-236U

Gang Lin, Jixin Qiao, Peter Steier, Magnús Danielsen, Kjartan Guðnason, Hans Pauli Joensen, Colin A. Stedmon

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Abstract

The pathway and transport time of Atlantic water passing northern Europe can be traced via anthropogenic radioisotopes released from reprocessing of spent nuclear fuels at Sellafield (SF) and La Hague (LH). These reprocessing derived radioisotopes, with extremely low natural background, are source specific and unique fingerprints for Atlantic water. This study explores a new approach using 99Tc-233U-236U tracer to estimate the transit time of Atlantic water in the coast of Greenland. We isolate the reprocessing plants (RP) signal of 236U (236URP) by incorporating 233U measurements and combine this with 99Tc which solely originates from RP, to estimate the transit time of Atlantic water circulating from Sellafield to the coast of Greenland-Iceland-Faroe Islands. Both being conservative radioisotopes, the temporal variation of 99Tc/236URP ratio in Atlantic water is only influenced by their historic discharges from RP, thus 99Tc/236URP can potentially be a robust tracer to track the transport of Atlantic water in the North Atlantic-Arctic region. Based on our observation data of 99Tc-233U-236U in seawater and the proposed 99Tc/236URP tracer approach, Atlantic water transit times were estimated to be 16–22, 25 and 25 years in the coast of Greenland, Iceland and Faroe Island, respectively. Our estimates from northeast Greenland coastal waters agree with earlier results (17–22 years). Therefore, this work provides an independent approach to estimate Atlantic water transit time with which to compare estimates from ocean modelling and other radiotracer approaches.
Original languageEnglish
Pages (from-to)158276
JournalScience of the Total Environment
Volume851
DOIs
Publication statusE-pub ahead of print - 5 Sep 2022

Keywords

  • 99Tc
  • 233U
  • 236U
  • Atlantic water
  • Transit time
  • Greenland-Iceland-Faroe Islands coast

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