Climate response over Asia/Arctic to change in orbital parameters for the last interglacial maximum

Abstract

The climate response over Asia/Arctic to the change in orbital parameters for the last interglacial maximum (LIGM) is investigated using the NCAR CCM3. After implementing LIGM orbital parameters, the insolation decreases in January and increases in July in the northern hemisphere in comparison to present values. The reduced net short-wave radiative heat fluxes in January lead to the surface cooling in low to mid latitudes of Asia, whereas a warming is obtained in northern Asia where the net short-wave radiative heat fluxes change little. The January warming in northern Asia/Arctic in the LIGM, consistent with proxy records, is mainly due to the marked increase in downward long wave heat fluxes associated with the increase in cloud and in part by the increase in the Arctic Oscillation polarity. In July, the increased insolation leads to the surface warming over most Asia, even though a slight cooling is obtained in low latitudes in spite of the increase in insolation, due to the decrease in the short-wave heat fluxes at the surface by the increase in the cloud amount. Precipitation overall increases at south and east Asia in July, due to the stronger southwest and southerly winds. The change in insolation due to the orbital parameters determines the climate change pattern in low- to mid-latitudes over Asia in the LIGM, even though the degree of climate change is much lower than suggested by proxy estimates. The results obtained in this study implies that, under the different climate background such as future global warming, the change greenhouse effect associated with cloud feedback could play an important role in determining the climate change over northern Asia/Arctic.