2:30 PM - 2:45 PM
[MIS12-24] Analysis of factors contributing to the differences between Pliocene and present-day precipitation using an atmosphere-ocean-vegetation coupled model
Keywords:Climate Model, Paleoclimate, Pliocene
The Pliocene is known to be a warmer period and had more precipitation in Africa than present-day. Analysis of the ensemble of PMIP2 investigated that the warming of the Sahara region due to the high CO2 concentration strengthened the West Africa Monsoon (Berntell et al., 2021). It is also revealed that in the present-day geographical conditions, the precipitation in Africa changes periodically, along with the variation of orbital forcing and the resulting changes in the ice sheet (Armstrong et al., 2023). On the other hand, there are differences in geographical conditions between the Pliocene and present-day. For example, in the Pliocene, the Hudson Bay and the Bering Strait were covered by land, and the ice sheets of Greenland and West Antarctica were smaller. It is suggested that these factors other than CO2 concentration have influences on the precipitation in the North Africa and West Asia. However, the mechanisms the differences in geographical conditions influence the precipitation is not clear.
In this study, we conducted the numerical experiments conducted with MIROC-LPJ in which CO2 concentration and geographical conditions were changed to those of pre-Industrial and Pliocene separately. The result shows that larger precipitation difference was seen when the geographical conditions were changed than the CO2 concentration. Especially, summer precipitation in the region from North Africa to West Asia increased significantly. It was found that the difference in geographical conditions such as Hudson Bay has influence on the precipitation in a distant region. With the Pliocene geographical condition, it likely to be warmer on the continent of the Northern Hemisphere in summer. It is said that by the warming of the continent of the Northern Hemisphere, the difference of temperature between land and sea got larger, and the monsoon was enhanced.
In this study, we conducted the numerical experiments conducted with MIROC-LPJ in which CO2 concentration and geographical conditions were changed to those of pre-Industrial and Pliocene separately. The result shows that larger precipitation difference was seen when the geographical conditions were changed than the CO2 concentration. Especially, summer precipitation in the region from North Africa to West Asia increased significantly. It was found that the difference in geographical conditions such as Hudson Bay has influence on the precipitation in a distant region. With the Pliocene geographical condition, it likely to be warmer on the continent of the Northern Hemisphere in summer. It is said that by the warming of the continent of the Northern Hemisphere, the difference of temperature between land and sea got larger, and the monsoon was enhanced.