Coupled Model Studies of the Tibetan Plateau Effect on the Atlantic Meridional Overturning Circulation under Different Resolutions

SHAO Xing, YANG Haijun†, LI Yang, JIANG Rui, YAO Jie, YANG Qianzi

Laboratory for Climate and Ocean-atmosphere Studies, Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing 100871; † Corresponding author, E-mail: hjyang@pku.edu.cn

Abstract The effect of Tibetan Plateau on the Atlantic Meridional Overturning Circulation (AMOC) under different resolutions is studied using the coupled Community Earth System Model (CESM1.0). Comparation of the results with and without the Tibetan Plateau tests shows that the changes of AMOC after the removal of the Tibetan Plateau are related to the resolution of the model. Under different resolutions, the changes of AMOC are inconsistent: AMOC Index decreases by 89% in the low resolution test, but only by 13% in the high resolution test. The reason for this difference is that there are significant differences in the changes of location and strength of the mixed layer subduction, which contributes to the deep water formation under different resolution test: the low resolution test is mainly located in the GIN seas, while the high resolution test is mainly located in the Labrador Sea. After removing the Tibetan Plateau, the subduction of both tests decreases, but the decrease of the low resolution test is larger than that of high resolution test. The subduction in the Labrador Sea of high resolution test decreases the most obviously, while the subduction in all sea areas decreases in the low resolution test, especially in the GIN seas. Comparation of the observed wind data and latest observational studies of deep water formation area over the North Atlantic shows that the results of low resolution coupled model are more similar to the actual observations in the seas studied in this paper. Key words Tibetan Plateau; Atlantic Meridional Overturning Circulation (AMOC); subduction; model resolution