Insolation and CO2 Impacts on the Spatial Differences of the MIS-9 and MIS-11 Climate Between Monsoonal China and Central Asia

On the Chinese Loess Plateau, the development of the paleosol S3 that was formed during the MIS-9 interglacial is weaker than some other paleosol units such as the S4 soil that was formed during the MIS-11 interglacial, suggesting relatively drier climate condition during MIS-9. By contrast, in Tajikistan of southern central Asia, the S3 is the most developed soil over the past 800 ka, indicating relatively warm and humid climate conditions. The difference in the paleosol formation and the MIS-9 climate between monsoonal China and central Asia is intriguing. In this study, we combine loess records from monsoonal China and central Asia as well as climate simulation results to understand the spatial difference of the MIS-9 climate in particular in comparison with the climate of MIS-11. Our results show that under the combined effects of greenhouse gases (GHGs) and insolation, the simulated effective moisture conditions between northern China and southern central Asia are consistent with the loess records. Insolation leads to much more annual mean precipitation than GHG during MIS-9 in southern central Asia, explaining a much wetter MIS-9 there. By contrast, both insolation and GHG lead to more annual mean precipitation and evaporation during MIS-9 in northern China, leading only to a slight difference in the effective moisture between MIS-9 and MIS-11. In addition, compared to MIS-11, the higher insolation and GHG concentration during MIS-9 generate an anomalous atmospheric circulation pattern similar to negative phase of North Atlantic Oscillation, favoring precipitation increase in southern central Asia.

Automated summary

In this study, loess records and climate simulation results were used to compare the climate differences between MIS-9 and MIS-11 in China and central Asia. The results showed that MIS-9 was relatively wetter in southern central Asia due to higher insolation and that both insolation and greenhouse gases contributed to slightly higher precipitation and evaporation in northern China during MIS-9 compared to MIS-11. Additionally, the higher insolation and greenhouse gas concentration during MIS-9 generated an anomalous atmospheric circulation pattern similar to the negative phase of the North Atlantic Oscillation, favoring precipitation increase in southern central Asia.