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

• Published in: Science of The Total Environment
• Main Authors: Lin, Gang, Qiao, Jixin, Steier, Peter, Danielsen, Magnús, Guðnason, Kjartan, Joensen, Hans Pauli, Stedmon, Colin A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2022
• Subjects: 99Tc; 233U; 236U; Atlantic water; Transit time; Greenland-Iceland-Faroe Islands cost; Arctic; Atlantic Arctic; Atlantic-Arctic; Faroe Islands; Greenland; Iceland; North Atlantic; Subarctic
• Online Access: https://orbit.dtu.dk/en/publications/3bb661f2-63fb-419a-a8bb-ecf471298446; https://doi.org/10.1016/j.scitotenv.2022.158276; https://backend.orbit.dtu.dk/ws/files/291780331/1_s2.0_S004896972205375X_main.pdf

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 99 Tc- 233 U- 236 U tracer to estimate the transit time of Atlantic water in the coast of Greenland. We isolate the reprocessing plants (RP) signal of 236 U ( 236 U RP ) by incorporating 233 U 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 99 Tc/ 236 U RP ratio in Atlantic water is only influenced by their historic discharges from RP, thus 99 Tc/ 236 U RP 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 99 Tc- 233 U- 236 U in seawater and the proposed 99 Tc/ 236 U RP 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.