Modelling the water isotopes distribution in the Mediterranean Sea using a high-resolution oceanic model (NEMO-MED12-watiso-v1.0): Evaluation of model results against in-situ observations

Abstract

Abstract. Stable water isotopes (δ18Osw and δD) have been successfully implemented for the first time in a high-resolution model of the Mediterranean Sea (NEMO-MED12). In this numerical study, model results are compared with available in-situ observations to evaluate the model performance about the present-day distribution of stable water isotopes and their relationship with salinity on a sub-basin-scale. There is good agreement between the modelled and observed distributions of δ18Osw in the surface water. The model successfully simulates the observed east-west gradient of 18Osw characterising surface, intermediate and deep waters. The results also show good agreement between the simulated δD and the in-situ data. The δD shows a strong linear relationship with δ18Osw (r2 = 0.98) and salinity (r2 = 0.94) for the whole Mediterranean Sea. Moreover, the modelled relationships between δ18Osw and salinity agree well with observations, with a weaker slope in the eastern basin than in the western basin. We investigate the relationship of the isotopic signature of the CaCO3 shell (δ18Oc) with temperature and the influence of seasonality. Our results suggest a more quantitative use of δ18O records, combining reconstruction with modelling approaches.