Abstract
Abstract. The H218O stable isotope was previously introduced in the three coupled components of the earth system model iLOVECLIM: atmosphere, ocean and vegetation. The results of a long (5000 yr) pre-industrial equilibrium simulation are presented and evaluated against measurement of H218O abundance in present-day water for the atmospheric and oceanic components. For the atmosphere, it is found that the model reproduces the observed spatial distribution and relationships to climate variables with some merit, though limitations following our approach are highlighted. Indeed, we obtain the main gradients with a robust representation of the Rayleigh distillation but caveats appear in Antarctica and around the Mediterranean region due to model limitation. For the oceanic component, the agreement between the modelled and observed distribution of water δ18O is found to be very good. Mean ocean surface latitudinal gradients are faithfully reproduced as well as the mark of the main intermediate and deep water masses. This opens large prospects for the applications in palaeoclimatic context.
Highlights
Water isotopes can be used as important tracers of the hydrological cycle
We present results of a 5000 yr equilibrium run under fixed pre-industrial boundary conditions that was used already in the first part of this study to verify the implementation of the water isotopic scheme
Results are presented centred around the mean for Global Network for Isotopes in Precipitation (GNIP) stations and for the closest model data point (Fig. 5)
Summary
During phase transitions of water, such as evaporation or condensation processes, an isotopic fractionation occurs (Craig and Gordon, 1965, for example). This fractionation results from small chemical and physical differences between the main isotopic form of the water molecule (H216O, H218O). The oxygen isotopic composition of seawater is a tracer for regional freshwater balance and water mass exchange (Ostlund and Hut, 1984; Jacobs et al, 1985). As the fluxes of freshwater affect the concentration of both the oxygen isotopic composition of seawater and salinity, important regional correlation between these two parameters can be observed in most of the ocean (Craig and Gordon, 1965; LeGrande and Schmidt, 2006). Because oxygen isotope signals are preserved in an important range of records (marine and continental carbonates, ice) they are widely used as palaeoclimate proxies
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