[A-CC21] Ice cores and past environmental changes

[ACC21-07] Glacial climate states and abrupt climate change in MIROC AOGCM

*Ayako Abe-Ouchi^1,2,3, Wing-Le Chan¹, Rumi Ohgaito², Kenji Kawamura³, Masakazu Yoshimori⁴, Akira Oka¹, Sam Sherriff-Tadano¹ (1.Atmosphere and Ocean Research Institute, The University of Tokyo, 2.JAMSTEC, 3.NIPR, 4.Hokkaido University)

Keywords:Paleoclimate, Climate Model

Millennial climate change such as D-O cycles and AIM recorded in ice cores in both Hemispheres is knownto show a relatively higher amplitude in the middle-level of a glacial cycle than in the interglacial state or severeglacial state. Here we ran several sensitivity experiments using a coupled atmosphere and ocean GCM (MIROC4m,renamed from MIROC3.2.2) and show that the response to fresh water release to the ocean and bipolar responseis highly dependent on the background climate. The experiments were conducted with 500 years water hosingof 0.05 to 0.1 Sv (where 1 Sv is equivalent to the water flux of 10m sea level rise in 100 years) in the NorthAtlantic 50-70N under different basic states; modern climate state with the pre-industrial condition, middle glacialclimate state and full glacial condition, mainly differing in the ice sheet configuration and atmospheric amount ofGreenhouse Gases. The results under middle glacial condition show largest cooling/warming response in NorthAtlantic and a reasonable bipolar warming/cooling signal revealed in the ice core data of the both hemisphere. Wediscuss the responses under different background climates which involve the strong coupling between atmosphere,ocean and sea ice and their dependence on the configuration of ice sheet.