Vegetation and soil feedbacks at the Last Glacial Maximum

Abstract

Vegetation feedback at the Last Glacial Maximum (LGM, about 21,000 calendar years ago) remains an unresolved question. A global atmospheric general circulation model (AGCM) is asynchronously coupled with an equilibrium terrestrial biosphere model in the present study. The coupled model is then used to investigate the influences of vegetation and soil feedbacks on the LGM climate. It is found that the simulated geographical distribution of vegetation at the LGM differs from the present pattern dramatically, and glacial vegetation cover tends to be reduced on average. Vegetation feedback alone leads to an annual surface temperature decrease of 0.31 °C over the LGM ice-free continental areas. Additional soil feedback reinforced vegetation-induced cooling over high latitude Eurasia and from the eastern Middle East eastward to the Indian Peninsula significantly. In the tropics, a terrestrial annual surface cooling of 0.45 °C is produced by vegetation and soil feedbacks. It is shown that vegetation and soil feedbacks partly reduce data-model discrepancy as produced by the AGCM alone in some regions such as Central Africa, the Indian Peninsula, South China, and North Australia.