The oxygen and carbon isotope distribution in the Mediterranean water masses |
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| Institution: | 1. School of GeoSciences, Grant Institute, University of Edinburgh, King''s Buildings, West Mains Road, Edinburgh EH9 3JW, UK;2. Geology and Mines Department, Marmara Bölgesi 32, Sokak, Lefko?a, Nicosia, Cyprus;3. Dipartimento di Ingegneria e Geologia (InGeo), Università degli Studi ‘G. d''Annunzio’ di Chieti-Pescara, Campus Universitario, via dei Vestini, 31 66100 Chieti Scalo, Italy;1. Senckenberg Biodiversity and Climate Research Centre (SBiK-F), Senckenberganlage 25, D-60325 Frankfurt am Main, Germany;2. Royal Netherlands Institute of Sea Research, P.O. Box 59, 1790 AB Den Burg, Texel, the Netherlands;3. Department of Geology and Geophysics, Bucharest University, Nicolae Balcescu 1, 010041 Bucharest, Romania;4. Department of Earth Sciences, Utrecht University, Princetonlaan 8A, 3584 CB Utrecht, the Netherlands;5. Department of Geosciences, University of Fribourg, Chemin du Musée 6, 1700 Fribourg, Switzerland;6. JURASSICA Museum, Route de Fontenais, 21, 2900 Porrentruy, Switzerland;7. Institute of Geosciences, Goethe University Frankfurt, Altenhöferallee 1, 60438 Frankfurt am Main, Germany;8. Geological Institute of Azerbaijan, H. Javid Av. 29A, AZ1143 Baku, Azerbaijan;9. CASP, West Building, Madingley Rise, Madingley Road, CB3 0UD Cambridge, United Kingdom |
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| Abstract: | The oxygen and carbon stable isotope compositions of the present-day Mediterranean waters have been measured in order to evaluate their variability, which is related to the specific climatic and hydrological conditions within the basin. The experimental equation between the δ18O value and the salinity of water, based on 300 measurements on surface, intermediate, and deep waters sampled during the VICOMED 2 and 3 cruises in the western, central and eastern Mediterranean, has a slope of 0.27, a value which is significantly lower than the slope of 0.45, as defined in the northeast Atlantic Ocean. This difference in the δ18O–salinity relationship, which occurs immediately in the Alboran basin, is basically a characteristic of the climatic regime of the Mediterranean, i.e., of an excess evaporation over fresh water input. The largest variations of these two parameters, δ18O of water and δ13C of ∑CO2, are observed in the surface waters, mostly in the western Mediterranean. This evolution mirrors the progressive eastward restriction, which separates the less-evaporated and more-productive western basins from the more-evaporated and less-productive eastern basins. The intermediate waters constitute a homogeneous layer. However, their δ18O values decrease eastward by 0.35‰ at maximum, due to progressive dilution by mixing with overlying and underlying water masses; their δ13C values decrease also eastward by 0.35‰ at maximum, due to an increasing input of nutrients issued from the regeneration of sinking organic particles. The deep waters have similar δ18O values but slightly higher δ13C values (often by less than 0.1‰) than the overlying intermediate waters, indicating generally well ventilated conditions due to active winter convection. |
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