Influence of LGM boundary conditions on the global water isotope distribution in an atmospheric general circulation model

T. Tharammal, A. Paul, U. Merkel, D. Noone
2012 Climate of the Past Discussions  
A series of experiments was conducted using a water isotope tracers-enabled atmospheric general circulation model (Community Atmosphere Model version 3.0, CAM3.0-Iso), by changing the individual boundary conditions (greenhouse gases, ice sheet albedo and topography, sea-surface temperature) each at a time to Last Glacial 5 Maximum (LGM) values. In addition, a combined simulation with all the boundary conditions being set to LGM values was carried out. A pre-industrial (PI) simulation with
more » ... mulation with boundary conditions taken according to the PMIP2 (Paleoclimate Modelling Intercomparison Project) protocol was performed as the control experiment. The experiments were designed in order to analyze the temporal and spatial variations of the oxygen iso-10 topic composition of precipitation (δ 18 O precip ) in response to individual climate factors. The change in topography (due to the change in land-ice cover) played a significant role in reducing the surface temperature and δ 18 O precip over North America. Exposed shelf areas and the ice sheet albedo reduced the Northern Hemisphere surface temperature and δ 18 O precip further. A global mean cooling of 4.1 • C was simulated with 15 combined LGM boundary conditions compared to the control simulation, which was in agreement with previous experiments using the fully coupled Community Climate System Model (CCSM3). Large reductions in δ 18 O precip over the LGM ice sheets were highly correlated with the temperature decrease over them. The SST and ice sheet topography changes were found to be responsible for most of the changes in the climate 20 and hence the δ 18 O precip distribution among the simulations. Jensen et al., 1998) and Antarctica (Stenni et al., 2001). During the LGM, a large 1320 CPD
doi:10.5194/cpd-8-1319-2012 fatcat:6e7imkobrnepvlhpr7p46ujtr4