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Advances in Atmospheric Sciences

, Volume 25, Issue 5, pp 805–814 | Cite as

Diagnosing ocean tracer transport from Sellafield and Dounreay by equivalent diffusion and age

  • Steinar OrreEmail author
  • Yongqi Gao
  • Helge Drange
  • Eric Deleersnijder
Article

Abstract

A simple approach for estimating the equivalent diffusion for diagnosing tracer transport is proposed. Two different expressions are derived; one is based directly on an analytical solution of the two-dimensional advection-diffusion equation, the other uses the variance of the tracer distribution. To illustrate some features of the equivalent diffusion and possible applications thereof, idealized releases of passive tracers from the nuclear fuel reprocessing plants at Sellafield in the Irish Sea and Dounreay on the northern coast of Scotland have been simulated with a regional isopycnic co-ordinate Ocean General Circulation Model. Both continuous and pulse releases are considered; the former being representative of the actual historical discharges from the reprocessing plants, the latter resembling an accidental scenario. Age tracers are included to calculate the mean time elapsed since the tracers left their source regions. It is found that in the Nordic Seas the age of tracers from Dounreay is approximately 2 years younger than the age from Sellafield. Although tracers from both sources eventually end up along the same transport routes, significant qualitative differences regarding the dispersion properties are found. It is argued that one single parameter, the equivalent horizontal diffusion, which is estimated to be in the range of 20–56 m2 s−1 from Sellafield and 170–485 m2 s−1 from Dounreay, determines these differences.

Key words

equivalent diffusion passive tracers age tracers sellafield dounreay 

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Copyright information

© Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag GmbH 2008

Authors and Affiliations

  • Steinar Orre
    • 1
    • 2
    Email author
  • Yongqi Gao
    • 1
    • 2
    • 3
  • Helge Drange
    • 1
    • 2
    • 3
    • 4
  • Eric Deleersnijder
    • 5
  1. 1.Nansen Environmental and Remote Sensing CenterBergenNorway
  2. 2.Bjerknes Centre for Climate ResearchBergenNorway
  3. 3.Nansen-Zhu International Research Centre, Institute of Atmospheric Physics (IAP)Chinese Academy of Sciences (CAS)BeijingChina
  4. 4.Geophysical InstituteUniversity of BergenBergenNorway
  5. 5.Centre for Systems Engineering and Applied Mechanics (CESAME), Louvain School of EngineeringUniversite catholique de LouvainLouvain-la-NeuveBelgium

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