[M-IS18] 古気候・古海洋変動

[MIS18-08] Effect of Climatic Precession on Dansgaard-Oeschger-like oscillations

*國吉 優太¹、阿部 彩子¹、シェリフ多田野 サム¹、陳 永利¹、齋藤 冬樹² (1.東京大学、2.海洋研究開発機構)

キーワード：古気候、気候変動、大西洋子午面循環、海氷、大気海洋結合モデル、氷期

Using the climate model MIROC4m, we simulate self-sustained oscillations of millennial-scale periodicity in the climate and Atlantic meridional overturning circulation under glacial conditions. We show two cases of extreme climatic precession and examine the mechanism of these oscillations. When the climatic precession corresponds to strong (weak) boreal seasonality, the period of the oscillation is about 1,500 (3,000) years. During the stadial, hot (cool) summer conditions in the Northern Hemisphere contribute to thin (thick) sea ice, which covers the deep convection sites, triggering early (late) abrupt climate change. During the interstadial, as sea ice is thin (thick), cold deep-water forms and cools the subsurface quickly (slowly), which influences the stratification of the North Atlantic Ocean. We show that the oscillations are explained by the internal feedbacks of the atmosphere-sea ice-ocean system, especially subsurface ocean temperature change and salt advection feedback with a positive feedback between the subpolar gyre and deep convection.