Journal of Climate, 19, 5008-5033, doi:10.1175/2008JCLI2104.1
Global-scale energy and freshwater balance in glacial climate: A comparison of three PMIP2 LGM simulations
S. Murakami, R. Ohgaito (Frontier Research Center for Global Change, JAMSTEC, Yokohama, Japan) A. Abe-Ouchi (Center for Climate System Research, University of Tokyo, Kashiwa, and Frontier Research Center for Global Change, JAMSTEC, Yokohama, Japan), M. Crucifix (Institut d’Astronomie et de Géophysique Georges Lemaître, Université catholique de Louvain, Louvain-La-Neuve, Belgium) and B. L. Otto-Bliesner (National Center for Atmospheric Research, Boulder, CO, U.S.A.)
Figure 1. Geographical maps of (top) vertically integrated northward DSE flux transported by transient eddies, (middle) rms 250-hPa height anomaly from the annual mean climatology, and (bottom) synoptic-scale waves using the MIROC for the (left) CTL and (right) LGM simulations. Contour intervals are 0.05 × 108 W m-1, 30 m, and 30 m, respectively. High resolution figure
Three coupled atmosphere–ocean general circulation model (AOGCM) simulations of the Last Glacial Maximum (LGM: about 21 000 yr before present), conducted under the protocol of the second phase of the Paleoclimate Modelling Intercomparison Project (PMIP2), have been analyzed from a viewpoint of large-scale energy and freshwater balance. Atmospheric latent heat (LH) transport decreases at most latitudes due to reduced water vapor content in the lower troposphere, and dry static energy (DSE) transport in northern midlatitudes increases and changes the intensity contrast between the Pacific and Atlantic regions due to enhanced stationary waves over the North American ice sheets. In low latitudes, even with an intensified Hadley circulation in the Northern Hemisphere (NH), reduced DSE transport by the mean zonal circulation as well as a reduced equatorward LH transport is observed. The oceanic heat transport at NH midlatitudes increases owing to intensified subpolar gyres, and the Atlantic heat transport at low latitudes increases in all models whether or not meridional overturning circulation (MOC) intensifies. As a result, total poleward energy transport at the LGM increases in NH mid- and low latitudes in all models. Oceanic freshwater transport decreases, compensating for the response of the atmospheric water vapor transport. These responses in the atmosphere and ocean make the northern North Atlantic Ocean cold and relatively fresh, and the Southern Ocean relatively warm and saline. This is a common and robust feature in all models. The resultant ocean densities and ocean MOC response, however, show model dependency.
Murakami, S., R. Ohgaito, A. Abe-Ouchi, M. Crucifix & B.L. Otto-Bliesner. 2008: Global-scale energy and freshwater balance in glacial climate: A comparison of three PMIP2 LGM simulations. Journal of Climate, 19, 5008-5033, doi:10.1175/2008JCLI2104.1.