[M-IS01_29PM1] Land-ocean linkages in East Asian marginal seas

[MIS01-01] 東アジアモンスーンの進化と変動そしてヒマラヤ－チベットの隆起との関連性

*多田 隆治¹ (1.東京大学大学院理学系研究科)

キーワード：モンスーン, ヒマラヤーチベット, テクトニクス-気候リンケージ, 東アジア, 日本海, 偏西風ジェット

Monsoon is climatic phenomenon driven by heat capacity contrast between the continent and ocean, so every continent has its own monsoon system. Asian Monsoon is by far the largest monsoon system on the globe. Although it is regional phenomenon, it exerts significant influence on the global climate. The extremely large size of Asian Monsoon system is considered as having been caused by the presence of Himalaya and Tibetan Plateau (HTP). The large size and high altitude of HTP resulted in higher temperature at ca. 5000 m altitude compared to the surrounding area during summer that resulted in ascending air and development of low pressure cell over the plateau. Topographic effect could be also important to enhance summer monsoon. Large size of Asian continent enhanced cooling over continent during winter, resulted in development of high pressure cell known as Siberian High. HTP plays a role of topographic barrier that keeps Siberian High stronger and stable. Consequently, presence of HTP could have been playing a crucial role to strengthen Asian Monsoon. If correct, uplift of HTP could have resulted in intensification of Asian Monsoon. Climatic simulations can be used to test the hypothesis that uplift of HTP has intensified Asian Monsoon if uplift history of HTP is known well. However, timings, modes, and magnitudes of HTP uplift have been poorly understood until recently. Situation is rapidly improved recently due to accumulation of thermo-chronological data from the various parts of HTP. Namely, collision of Indian Subcontinent against Eurasian Continent approximately at 40 Ma caused the 1st phase of Tibetan uplift that raised southern Tibet close to the present height by 35 Ma. From 25 Ma to 15 Ma, Main Central Thrust (MCT) and South Detachment System (STDS) in frontal Himalaya were activated and lower crust was extruded and eroded extensively. Approximately at 15 Ma, these fault system ceased their movements and east-west extension started in Tibet. From 15 Ma to 10Ma is the 2nd phase when Tibetan Plateau grew southeastward and possibly also northward. The 3rd phase of uplift started from approximately 5 Ma when northwestern Tibet, TienShan and Altai Mountains uplifted. Using this uplifting history of HTP as a boundary condition, it is possible to estimate what kind of paleoclimatic changes are expected in response to these 3 uplift phases based on climate simulation results. In this presentation, I will review a recent progress in researches on tectonics-climate linkage as HTP uplift and Asian Monsoon evolution as an example.