Grant-in-Aid for Scientific Research on Priority Areas
|Research Institution||Earthquake Research Institute, University of Tokyo|
SENO Tetsuzo Earthquake Research Inst., Univ. of Tokyo, 地震研究所, 教授 (10216567)
小川 克郎 名古屋大学, 理学部, 教授 (40262844)
ITO Keisuke Faculty of Science, Kobe University, 理学部, 教授 (00030792)
ABE Ayako Climate System Center, Univ. of Tokyo, 気候システムセンター, 助手 (30272537)
HONDA Satoru Faculty of Science, Hiroshima University, 理学部, 教授 (00219239)
OGAWA Masaki Faculty of Culture, Univ. of Tokyo, 教養学部, 助教授 (30194450)
安成 哲三 筑波大学, 地球科学系, 教授 (80115956)
YAMANAKA Yasuhiro Climate System Center, Univ. of Tokyo, 気候システムセンター, 助手 (40242177)
|Project Fiscal Year
1995 – 1997
Completed(Fiscal Year 1997)
|Budget Amount *help
¥40,700,000 (Direct Cost : ¥40,700,000)
Fiscal Year 1997 : ¥4,800,000 (Direct Cost : ¥4,800,000)
Fiscal Year 1996 : ¥22,900,000 (Direct Cost : ¥22,900,000)
Fiscal Year 1995 : ¥13,000,000 (Direct Cost : ¥13,000,000)
|Keywords||earth system / multisphere interaction / mantle convection / core / surface lager / sea level / climate change / ocean circulation / 地球システム / 多圏相互作用 / マントル対流 / 中心核 / 表層圏 / 海水準 / 気候変動 / 海洋循環 / モデリング / 非線形力学系 / 進化 / ミランコビッチサイクル / イベント / 初期地球 / ウイルソンサイクル / 地球表層環境 / テクトスフェア / ミランコビッチ / P / T境界 / 自己組織化|
Earth is a complex system where surface and interior layers interact. We investigate this interaction from the viewpoint of outputs from forcing such as internal and external forcing. The internal forcing is the mantle and core activities, and the external forcing is the temporal variation of the solar radiation. In the Earth's history mantle activities cause crustal evolution, global sea level change, Wilson cycles, flushing events, and plumes with time scales of 1-0.1 Gy. This causes environmental changes such as changes of the continent distribution and continent area above sea level. Climate change is then studied as a response of environments different from the present one to the solar radiation and Milankovitch cycles.
We elucidated the temporal change of the mantle convection. During 4-2 Ga, thick residual material from extensive melting covered the Earth's surface and episodic avalanche occurred due to boundary layer instabilities. During 2-0 Ga, a thermal convection similar to
the present plate tectonics occured. Thus the A/P event around 2.0 Ga should be the transition between the two convection modes.
We studied the global sea level change which is expected to have occurred when the above tempral change of mantle convection occurred. The sea level fell gradually since 4.0 Ga until 2 Ga. Around 2 Ga, when plate tectonics began, it rose suddenly by 800 m, and since 1.3 Ga when it reached the peak, it fell gradually until present. The continent area above sea level exceeded more than 40 % of the present area during 2.8-1.9 Ga and 1.0-0 Ga. The second order sea level change was calculated by reconstructing Wilson cycles since 1.9 Ga. CO2 content in the atmosphere and surface temperature were recovered using GEOCARB model. To combine this with the climate or ocean general circulation models, we studied the response of a climate system under continent and ocean distributions different from the present ones.
We studied the evolution of the Earth system as a complex system, and found that it self-organizes into a critical state, i.e., an edge of chaos. This happens because each element of the system decides its behavior by observing himself through other elements. Less