Abstract
Abstract. A new 18O stable water isotope scheme is developed for three components of the iLOVECLIM coupled climate model: atmospheric, oceanic and land surface. The equations required to reproduce the fractionation of stable water isotopes in the simplified atmospheric model ECBilt are developed consistently with the moisture scheme. Simplifications in the processes are made to account for the simplified vertical structure including only one moist layer. Implementation of these equations together with a passive tracer scheme for the ocean and a equilibrium fractionation scheme for the land surface leads to the closure of the (isotopic-) water budget in our climate system. Following the implementation, verification of the existence of usual δ18O to climatic relationships are performed for the Rayleigh distillation, the Dansgaard relationship and the δ18O –salinity relationship. Advantages and caveats of the approach taken are outlined. The isotopic fields simulated are shown to reproduce most expected oxygen-18–climate relationships with the notable exception of the isotopic composition in Antarctica.
Highlights
Water isotopes are widely used tracers of the hydrological cycle
The iLOVECLIM model is a code fork of the LOVECLIM1.2 climate model extensively described in Goosse et al (2010)
As precipitation falls on land surface, the water and water isotopes are added to the bucket water model
Summary
Water isotopes are widely used tracers of the hydrological cycle. With fractionation occurring at phase changes (evaporation, condensation, freezing, e.g. Craig and Gordon, 1965) and through diffusive processes at smaller scale, water isotopes are faithful recorders of the complex processes at work within the hydrological cycle. Craig and Gordon, 1965) and through diffusive processes at smaller scale, water isotopes are faithful recorders of the complex processes at work within the hydrological cycle. They have been used for decades in the field of palaeoclimate research to infer climatic conditions from the ice-cores (Dansgaard, 1964; Dansgaard et al, 199T3;hEePICCArycoomsmpuhnietyremembers, 2004; North Greenland Ice Core Project members, 2004) or from oceanic sediment cores (Emiliani, 1955, for example) but may be used at much smaller timescale and spatial scale to link climate variability and water isotope compositions (Kurita et al, 2011) or even to infer the mixing properties within rain events (Risi et al, 2010a). From a climatic modelling perspective, the inclusion of water isotopes enable a thorough evaluation of the hydrological cycle in climate models, against precipitation amount or evaporation amount observations, and on the actual transport of water through the atmospheric model. In the two companion manuscripts, we present the model validation and evaluation, at first from the perspective of δ18O in water from present-day observations (Roche and Caley, 2013) and second with a palaeoperspective against late Holocene carbonate proxy data (Caley and Roche, 2013)
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