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Article Dans Une Revue The Geological Society, London, Special Publications Année : 2021

Geographic variations in the slope of the δ2H–δ18O meteoric water line over Europe: A record of increasing continentality

Résumé

δ2H and δ18O values of precipitations follow an empirical linear relationship at the global scale that is called the Global Meteoric Water Line (GMWL) and characterized by a slope of 8. However, Local Meteoric Water Lines (LMWLs) may have different slopes S depending on their geographic situation. Monthly δ2H and δ18O of precipitation have been compiled from European International Atomic Energy Agency (IAEA) stations. Those data allowed the calculation of the slopes S of the δ2H–δ18O LMWL determined for each station. S increases with longitude ϕ from c. 5 (Portugal) to c. 9 (Russia) – they are positively correlated with relative humidity (RH), negatively with temperature and positively with the mean intra-annual amplitude of temperatures, which is a proxy of continentality. Slopes of 5–6, recorded in SW Europe, reflect mean RH (70–75%) and sea surface temperatures (c. 25°C) of the Central Atlantic Ocean where the main flux of moisture is formed before being transported by the westerlies. In addition, falling water droplets within an air column with a high RH (>80%) and low temperature are expected to escape sub-cloud evaporation. Therefore, slopes with values close to 9 are considered to reflect isotopic equilibrium conditions during the condensation of water vapour in clouds.
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Dates et versions

hal-02897843 , version 1 (08-07-2021)

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Christophe Lécuyer, Ana-Voica Bojar, Valérie Daux, Serge Legendre. Geographic variations in the slope of the δ2H–δ18O meteoric water line over Europe: A record of increasing continentality. The Geological Society, London, Special Publications, 2021, 507, pp.SP507-2020-68. ⟨10.1144/SP507-2020-68⟩. ⟨hal-02897843⟩
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