Historical isotope simulation using Reanalysis atmospheric data

In this paper we present a multidecadal and global three-dimensional stable water isotope data set. This is accomplished by incorporating processes of the stable water isotopes into an atmospheric general circulation model and by applying a spectral nudging technique toward Reanalysis dynamical fields. Unlike the global model simulations forced only by sea surface temperature (SST), the dynamical fields used in the simulation are never far from observation because the spectral nudging technique constrains large-scale atmospheric circulation to that of observation, and therefore the simulated isotopic fields are reasonably accurate over the entire globe for daily to interannual time scales. As a case in point, it is revealed that the current approach reproduces the Arctic Oscillation much more correctly than the simulations forced only by SST, and consequently, the monthly isotopic variability better matches observations over midlatitudes to high latitudes in the Northern Hemisphere, especially Europe. This method is of great use in providing information in regions where in situ isotope observations are not available. Such information is required for a variety of biogeochemical, hydrological, and paleoclimate studies and as boundary and initial conditions for regional isotopic simulations.