Abstract
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.
Highlights
Several recent studies show that the Mediterranean Sea will be sensitive to climate change impacts (Giorgi, 2006; Diffenbaugh and Giorgi, 2012)
High tritium concentrations are simulated in the intermediate waters over the whole eastern Mediterranean Basin (EMed), except in the northern Levantine Basin considered as the main source of Levantine Intermediate Water (LIW), and south of France in the Gulf of Lions where the source of Western Mediterranean Deep Water (WMDW) is located
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 (NEMOMED12) at 1/12◦ of horizontal resolution (6–8 km)
Summary
Several recent studies show that the Mediterranean Sea will be sensitive to climate change impacts (Giorgi, 2006; Diffenbaugh and Giorgi, 2012). M. Ayache et al.: Modelling of the anthropogenic tritium transient forcing mechanisms, including air–sea interaction, buoyancy fluxes and lateral mass exchange, are present, as well as intermediate and deep water masses formation (POEM-group, 1992). Ayache et al.: Modelling of the anthropogenic tritium transient forcing mechanisms, including air–sea interaction, buoyancy fluxes and lateral mass exchange, are present, as well as intermediate and deep water masses formation (POEM-group, 1992) It makes an excellent laboratory test basin for studying processes that affect the global thermohaline circulation
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