日本地球惑星科学連合2019年大会

講演情報

[J] ポスター発表

セッション記号 M (領域外・複数領域) » M-IS ジョイント

[M-IS19] 古気候・古海洋変動

2019年5月30日(木) 15:30 〜 17:00 ポスター会場 (幕張メッセ国際展示場 8ホール)

コンビーナ:岡崎 裕典(九州大学大学院理学研究院地球惑星科学部門)、岡 顕(東京大学大気海洋研究所)、加 三千宣(愛媛大学沿岸環境科学研究センター)、長谷川 精(高知大学理工学部)

[MIS19-P19] The changes of the Kuroshio path in the Northwest Pacific since 35ka

*Haiyan Yang1Xinyu Guo1Ayako Abe-Ouchi2Yasumasa Miyazawa3Sergey Varlamov4Wing-Le Chan2 (1.Center for Marine Environmental Studies, Ehime University、2.Atmosphere and Ocean Research Institute, University of Tokyo、3.Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology、4.Application Laboratory, Japan Agency for Marine-Earth Science and Technology)

キーワード:Kurosio, Path, Evolution

Kuroshio, a strong western boundary current in the subtropical North Pacific, has strong influences on the climate of Japan and East Asia. Global sea level rises and falls when ice sheets and glaciers melt and grow. The Last Glacial Maximum (LGM, 21ka) is the most recent interval in Earth history when global ice sheets reached their maximum integrated volume. The expansion of the ice sheets at the LGM resulted in a sea-level lowering of about 130 m and a cold phase compared to present. Under the circumstance of sea level, Kuroshio did not bifurcate into the Japan Sea and form the Tsushima Current. As the sea level rises, the Tsushima Current flowed into the Japan Sea at about 10ka (Gallagher et al., 2015), and the sea-level reached the present level at 7ka~6ka (Zheng et al., 1994). However, how the Kuroshio and Tsushima Current pathway evolved in the conditions of different sea level and climate remains unclear.

In Okinawa and southern Korea, some archaeologists have found evidences of people drifting on the Kuroshio from Taiwan to northern regions. According to studies by Japanese anthropologists, the first person that set foot on Okinawa probably sailed there on bamboo rafts from Taiwan more than 30,000 years ago. However, this hypothesis needs more evidences because sailing across the Kuroshio is a difficult thing if the Kuroshio 30,000 years ago had the same surface velocity as present. Therefore, clarifying the strength and path of Kuroshio is also helpful to the understanding on human migration.

In this study, we used the model of Japan Coastal Ocean Predictability Experiment (JCOPE) to simulate the changes of the Kuroshio path under the combined influences of sea level, the air-sea heat flux, and wind stresses in five historical regimes (35ka, 30ka, LGM, 6ka, and 0ka). The meteorological and oceanic data are provided by the climate model MIROC4m (Chan et al., 2011) which is a fully coupled atmosphere-ocean general circulation model (AOGCM).