CESDセミナー
共催：東京大学大気海洋研究所地球表層圏変動センター, PAGES, INQUA commission of Coastal and Marine Processes, JAMSTEC
今回はハワイ大学のAxel Timmerman教授に「地球システムモデルを用いた氷期-間氷期サイクル変動研究」について講演していただく予定です。
日時：2012年10月29日 (Mon) 16:00-17:00
場所：東京大学 大気海洋研究所（アクセス） @217号室
問い合わせ先：横山祐典（yokoyama AT aori.u-tokyo.ac.jp）
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Abstruct
Glacial cycles with timescales of 80-100 thousand years are one of the largest climate signals in the geological record of the Cenozoic. Whereas the role of orbitally-induced solar insolation changes in pace-making glacial cycles, has been recognized since more than hundred years, the detailed physical mechanisms of how insolation variations translate into the waxing and waning of massive inland ice-sheets still remain elusive. This talk will present first results from a newly developed 3-dimensional coupled ice-sheet climate model that is capable of simulating glacial cycles in response to orbital and greenhouse gas forcing. A brief summary of general ice-sheet-climate modeling issues (including mass balance, albedo, initialization, model biases and multiple equilibria) will be followed by an extensive discussion of the mechanisms that lead to the build-up of Northern Hemisphere ice-sheets and their demise. Our results support the notion that changes in boreal summer insolation and greenhouse gases are essential in triggering deglacial ice-sheet retreat in the Northern Hemisphere. The model simulations further illustrate that orbital forcing in austral spring strongly affects the Southern Hemispheric sea-ice extent, which in turn modulates the efficiency of Ekman pumping in the Southern Ocean. This process controls the upwelling of DIC-rich waters, hence contributing to the glacial variability in atmospheric CO2 concentrations. According to this scenario the dynamics of Northern Hemisphere ice-sheets is then determined by the local orbital forcing as well as by the CO2 changes -- the latter originating from orbitally-modulated processes in the Southern Hemisphere.
