Midlatitude moisture transport in simulations of paleoclimates

Over its long geologic history, Earth's climate has spanned a wide range of states including ones hotter and others colder than our contemporary one. Simulations of these various paleoclimates using general circulation models offer a useful dataset to test climate theories across a wider expanse of climate states than is available from observations of the past century alone. Recent work by Pauluis et al. (2008) showed that when the midlatitude circulation of our present-day atmosphere is analyzed on moist isentropes, the total mass transport is 2 to 3 times larger than it is when analyzed on dry isentropes, underscoring a strong role for poleward and upward transport of moisture in the midlatitude storm tracks. In this work, I extend this analysis to simulations of the Last Glacial Maximum and to hot climates with high levels of carbon dioxide such as the early Eocene epoch using daily output from T170 simulations with NCAR's CCSM. The climate variability of moisture transport by large-scale eddies and slantwise convective motions in the midlatitude atmosphere are analyzed using a diagnostic of slantwise convective neutrality.