DEVELOPMENT OF THE ISOTOPE VERSION OF THE FULLY COUPLED CLIMATE MODEL MIROC6-ISO

Abstract

 Stable water isotopes (H216O, H218O and HD16O) are proxies of climate processes occurring in the water cycle, the latter having a crucial role in the Earth’s climate system. For example, water isotopes measured in polar ice cores and Asian speleothems are commonly used to reconstruct past temperature changes in the poles or to study the past dynamics of monsoons, respectively. In this study, we present the ongoing development and first results, for the preindustrial period, of a newly developed isotope-enabled version of the fully coupled Earth System Model MIROC6, called hereafter MIROC6-iso. Our preliminary results are in rather good agreement with isotope observations in precipitation and surface sea water. Some improvements are expected in Antarctica thanks to the coming implementation of water isotopes in the sea ice module of MIROC6-iso. The modeled isotope distribution in the first 1500 meters of the ocean goes also in the right direction compared to observations. For the deeper part, more spin-up time is necessary to reach a quasi-equilibrium state.

 Considering the applications using isotope-enabled fully coupled climate models from Europe and the United States for paleoclimate reconstruction, there is a pressing need for Japan to develop such a state-of-the-art model, too. Additionally, it paves the way for the future refinement and development of MIROC6-iso, while also serving as an important point of reference for subsequent analysis of the climate, hydrological cycle, and paleoclimate reconstruction using MIROC6-iso.