Land-atmosphere coupling during the last glacial maximum: an Australian perspective

Larsen, JR; Nanson, GC; Cendón, DI

Land-atmosphere coupling during the last glacial maximum: an Australian perspective

Date

2011-07-21

Authors

Larsen, JR

Nanson, GC

Cendón, DI

Publisher

International Union For Quaternary Research (INQUA)

Abstract

The last glacial climate experienced extreme variability, however during the peak of the glacial conditions, the last glacial maximum (LGM), many areas of the Southern Hemisphere do not appear to experience corresponding minima in temperature and precipitation. This presents a considerable conundrum for our understanding of glacial climates, and more specifically for the land-atmosphere energy balance. In an effort to gain further insight, we examine potential scenarios for the water budget on the Australian continent during the LGM, and compare these with a variety of direct and proxy evidence for temperature, evaporation, and precipitation. Current research suggests some areas of Australia were wetter than expected during the LGM, however many researchers have also suggested precipitation in most areas was lower than the present. Thus in order to rectify the water balance, lower global surface air temperatures have been used to infer correspondingly lower evaporation rates. We examine both the theoretical and the palaeoclimatic evidence for lower evaporation, and find that in many cases, the relationship between lower temperature and evaporation is not straightforward. If the global hydrological cycle was slowed by lower global temperatures, then reduced overall actual evaporation could potentially increase atmospheric capacity depending on the vapour pressure deficit. Furthermore, atmospheric demand strongly depends on whether the environment is water limited or energy limited, and since much of the Australian continent is water limited, we expect actual evaporation to be much more sensitive to other external forcings such as wind speed and solar irradiance than temperature. These results have significant implications for the continental water balance, and alterative scenarios for precipitation, runoff, evaporation, vegetation and atmospheric feedback are proposed.

Keywords

Glaciers, Climates, Southern Hemisphere, Atmospheric precipitations, Australia, Ambient temperature, Energy, Water

Citation

Larsen J., Nanson G., & Cendón D. I. (2011). Land-atmosphere coupling during the last glacial maximum: an Australian perspective. Paper presented at the 18th International Union for Quaternary Research Congress, Berne, Switzerland, 21st-27th July 2011.