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Volume 11, issue 3
Ocean Sci., 11, 323–342, 2015
https://doi.org/10.5194/os-11-323-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ocean Sci., 11, 323–342, 2015
https://doi.org/10.5194/os-11-323-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 12 May 2015

Research article | 12 May 2015

Modelling of the anthropogenic tritium transient and its decay product helium-3 in the Mediterranean Sea using a high-resolution regional model

M. Ayache1, J.-C. Dutay1, P. Jean-Baptiste1, K. Beranger2, T. Arsouze2, J. Beuvier3,4, J. Palmieri1, B. Le-vu1, and W. Roether5 M. Ayache et al.
  • 1Laboratoire des Sciences du Climat et de l'Environnement (LSCE), IPSL, CEA/UVSQ/CNRS, Orme des Merisiers, Gif-Sur-Yvette, France
  • 2ENSTA ParisTech, Palaiseau, France
  • 3Mercator-Océan, Ramonville Saint-Agne, France
  • 4CNRM-GAME (Météo-France, CNRS), Toulouse, France
  • 5Institut fur Umweltphysik, University of Bremen, Bremen, Germany

Abstract. This numerical study provides the first simulation of the anthropogenic tritium invasion and its decay product helium-3 (3He) in the Mediterranean Sea. The simulation covers the entire tritium (3H) transient generated by the atmospheric nuclear weapons tests performed in the 1950s and early 1960s and is run till 2011. Tritium, helium-3 and their derived age estimates are particularly suitable for studying intermediate and deep-water ventilation and spreading of water masses at intermediate/deep levels. The simulation is made using a high-resolution regional model NEMO (Nucleus for European Modelling of the Ocean), in a regional configuration for the Mediterranean Sea called MED12, forced at the surface with prescribed tritium evolution derived from observations.

The simulation is compared to measurements of tritium and helium-3 performed along large-scale transects in the Mediterranean Sea during the last few decades on cruises of R/V Meteor: M5/6, M31/1, M44/4, M51/2, M84/3, and R/V Poseidon: 234. The results show that the input function used for the tritium generates a realistic distribution of the main hydrographic features of the Mediterranean Sea circulation. In the eastern basin, the results highlight the weak formation of Adriatic Deep Water in the model, which explains its weak contribution to the Eastern Mediterranean Deep Water (EMDW) in the Ionian sub-basin. It produces a realistic representation of the Eastern Mediterranean Transient (EMT) signal, simulating a deep-water formation in the Aegean sub-basin at the beginning of 1993, with a realistic timing of deep-water renewal in the eastern basin.

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The anthropogenic tritium invasion, and its decay product helium-3, was simulated for the first time in the Mediterranean Sea, using a high-resolution regional model (NEMO-MED12). The simulation covers the entire tritium (3H) transient generated by the atmospheric nuclear weapons tests performed in the 1950s and early 1960s and run until 2011. The model correctly simulates the main features of the thermohaline circulation in the Mediterranean Sea, with a realistic time compared to observations.
The anthropogenic tritium invasion, and its decay product helium-3, was simulated for the first...
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