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

Published on 2020-06-26T10:53:36Z (GMT) by
δ2H and δ1820 O 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 (LMWL) may have different slopes depending on their geographic situation. Monthly δ2H and δ1823 O of precipitation have been revised manuscript with corrections in blue compiled from European IAEA stations. Those data allowed the calculation of the slopes S of the δ2H–δ1825 O LMWL determined for each station. S increases with longitude δ from <i>c.</i>5 (Portugal) to <i>c.</i>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 to 6, recorded in southwest Europe, reflect mean RH (70 to 75%) and sea surface temperatures (<i>c.</i>25<sup>o</sup>C) of the Central Atlantic Ocean where the main flux of moisture is formed before being transported by the westerlies. The observed logarithmic growth of S with increasing continentality is interpreted as a temperature effect during the progressive distillation of the humid air mass over Europe. 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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Lécuyer, Christophe; Bojar, Ana-Voica; Daux, Valérie; Legendre, Serge (2020): Geographical variations in the slope of the δ2H–δ18O meteoric water line over Europe: a record of increasing continentality. Geological Society of London. Collection. https://doi.org/10.6084/m9.figshare.c.5040647.v1