Time slice simulation for LIA and MCA with stable water isotopes and comparison with modern situation

Abstract:

The last millennia are suitable to understand the variability arising from external forcings and internal climate variability. Numerous studies reconstructed global and/or Northern Hemisphere temperature variability and agree well with the simulation for the period. When comparing the spatial distributions of simulated and reconstructed field, however, there are some discrepancies, which stem from the uncertainties of forcings, reconstructions and GCMs. To validate the model we directly compare the simulated isotopes with that of climate proxies in this study. For that purpose we implemented stable water isotopes (HDO, and H₂¹⁸O) into MIROC5A, which consists of atmospheric and land surface components of MIROC5 developed jointly by University of Tokyo, NIES, and JAMSTEC. The implementation manner of isotopes is based on the previous version of isotope enabled MIROC [Kurita et al., 2011] for its atmospheric component and on iso-MATSIRO [Yoshimura et al., 2006] for its land surface component. Using the model, time slice experiments for warm climate anomaly (WCA; 950-1250) and little ice age (LIA; 1450-1850) were conducted. The simulations were forced by simulated sea surface temperature and sea ice from the last millennium experiments of CMIP5-PMIP3. For the other boundary conditions (e.g. orbital parameters, concentrations of GHGs, solar irradiance, etc.), we follow the protocol of CMIP5-PMIP3. Both simulations are 30 years long with a spin-up of one year. At the presentation, the comparison results of simulated isotopes with that of proxies are presented.