EGU21-8662
https://doi.org/10.5194/egusphere-egu21-8662
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Annual variability of the long-lived anthropogenic radionuclides 129I and 236U in the Fram Strait and their use as water mass composition tracers

Anne-Marie Wefing1,2, Núria Casacuberta1,3, Marcus Christl1, Michael Karcher4,5, and Paul A. Dodd6
Anne-Marie Wefing et al.
  • 1Laboratory of Ion Beam Physics, ETH Zürich, Zürich, Switzerland (awefing@phys.ethz.ch)
  • 2Environmental Physics, Institute of Biogeochemistry and Pollutant Dynamics, ETH Zürich, Switzerland
  • 3Inorganic Environmental Geochemistry, Institute of Biogeochemistry and Pollutant Dynamics, ETH Zürich, Switzerland
  • 4Alfred Wegener Institut, Helmholtz Zentrum für Polar- und Meeresforschung, Bremerhaven, Germany
  • 5Ocean Atmosphere Systems GmbH, O.A.Sys, Hamburg, Germany
  • 6Norwegian Polar Institute, Tromsø, Norway

Anthropogenic chemical tracers are powerful tools to study pathways, water mass provenance and mixing processes in the ocean. Releases of the long-lived anthropogenic radionuclides 129I and 236U from European nuclear reprocessing plants label Atlantic Water entering the Arctic Ocean with a distinct signal that can be used to track pathways and timescales of Atlantic Water circulation in the Arctic Ocean and Fram Strait. Apart from their application as transient tracers, the difference in anthropogenic radionuclide concentrations between Atlantic- and Pacific-origin water provides an instrument to distinguish the interface between both water masses. In contrast to classically used water mass tracers such as nitrate-phosphate (N:P) ratios, the two radionuclides are considered to behave conservatively in seawater and are not affected by biogeochemical processes occurring in particular in the broad shelf regions of the Arctic Ocean.

Here we present a time-series of 129I and 236U data across the Fram Strait, collected in 2016 (as part of the GEOTRACES program) and in 2018 and 2019 (by the Norwegian Polar Institute). While the overall spatial distribution of both radionuclides was similar among the three sampling years, significant differences were observed in the upper water column of the EGC, especially between 2016 and 2018. This study is the first attempt to investigate the potential of 129I and 236U as water mass composition tracers in the East Greenland Current (EGC). We discuss how the 129I - 236U tracer pair can be applied to estimate fractions of Atlantic and Pacific Water, especially considering their time-dependent input into the Arctic Ocean.

How to cite: Wefing, A.-M., Casacuberta, N., Christl, M., Karcher, M., and Dodd, P. A.: Annual variability of the long-lived anthropogenic radionuclides 129I and 236U in the Fram Strait and their use as water mass composition tracers, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8662, https://doi.org/10.5194/egusphere-egu21-8662, 2021.

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