Tracing Atlantic water transit times in the Arctic Ocean: Coupling reprocessing-derived ²³⁶U and colored dissolved organic matter to distinguish different pathways

Author(s)

Gang Lin, Jixin Qiao, Paul A. Dodd, Rafael Gonçalves-Araujo, Mats A. Granskog, Peter Steier, Colin A. Stedmon

Abstract

The Fram Strait is a key region for investigating the exchange of Atlantic water with the Arctic Ocean. Uranium-236 (236U) from the two European nuclear reprocessing plants (NRPs) at La Hague and Sellafield provides a unique fingerprint in Atlantic water which can be used for studying its circulation patterns in the Arctic Ocean. And NRPs-derived 236U (236UNRPs) can be identified by its 233U/236U signature. In this study, we use colored dissolved organic matter (CDOM) absorption to constrain the selection of three Atlantic branch waters that carried different inputs of 236UNRPs in Fram Strait. This can potentially provide better estimates of transit times of Atlantic waters in the Arctic Ocean. High CDOM levels (a350≥0.35 m−1) in Fram Strait reflect the passage of Atlantic water transported to the Arctic by the Norwegian Coastal Current (NCC) and its extension and subsequently along the Siberian continental slope and shelf where the Ob, Yenisei and Lena rivers supply terrestrial organic matter with significantly high CDOM content. Conversely, low CDOM water represents Atlantic water that has remained off the shelf. Based on CDOM absorption, potential temperature (Θ), potential density (σΘ) and 236U concentration, the path of a given body of Atlantic water could be inferred and an appropriate NRPs input function constrained so that transit times could be estimated. Our results indicate that Arctic High CDOM Water (a350≥0.35 m−1) sourced from the NCC and Barents Sea Branch Water (BSBW) in the Barents Sea Opening has an average of 7–27 yrs transit time in the upper ∼200 m of the western shelf of the Fram Strait. Atlantic Low CDOM Water (a3502 °C) sourced from the Fram Strait Branch Water (FSBW) has a short pathway from the eastern Fram Strait. Arctic Low CDOM / High 236U Water (a350

Organisation(s)

Isotope Physics

External organisation(s)

Technical University of Denmark (DTU), Norwegian Polar Institute

Journal

Earth and Planetary Science Letters

Volume

622

No. of pages

13

ISSN

0012-821X

DOI

https://doi.org/10.1016/j.epsl.2023.118415

Publication date

11-2023

Peer reviewed

Yes

Austrian Fields of Science 2012

103014 Nuclear physics, 104020 Radiochemistry, 105904 Environmental research

Keywords

ASJC Scopus subject areas

Geophysics, Geochemistry and Petrology, Space and Planetary Science, Earth and Planetary Sciences (miscellaneous)

Portal url

https://ucris.univie.ac.at/portal/en/publications/tracing-atlantic-water-transit-times-in-the-arctic-ocean-coupling-reprocessingderived-236u-and-colored-dissolved-organic-matter-to-distinguish-different-pathways(a1be8ca6-0294-435a-b007-2989c908e269).html