[A-CC27] Ice cores and paleoenvironmental modeling

[ACC27-10] Climate modeling study on the mechanisms for millennial-scale climate variability during glacial periods

★Invited Papers

*Yuta Kuniyoshi¹, Ayako Abe-Ouchi¹, Wing-Le Chan¹, Sam Sherriff-Tadano² (1.The University of Tokyo, 2.University of The Ryukyus)

Keywords:Dansgaard-Oeschger event, Atlantic meridional overturning circulation, Atmosphere-Ocean interaction, Paleoclimate modelling

Glacial climate was dominated by millennial-scale variability, such as Dansgaard-Oeschger (DO) events which have been identified in Greenland ice core records. The millennial-scale climate change was shown to be strongly associated with abrupt changes in the Atlantic meridional overturning circulation (AMOC). Recently, several studies using coupled atmosphere-ocean model have shown the millennial timescale oscillations of the atmosphere-ocean system and proposed several intrinsic oscillators: A ‘salt oscillator’ related to sea surface salinity changes in the North Atlantic and/or a ‘deep decoupling oscillator’ which involves sea ice change and subsurface temperature change in the North Atlantic. Our research group has shown that the latter oscillator may play a more important role (Kuniyoshi et al. 2022GRL), but it is not yet clear whether the oscillations are driven purely by changes in heat and/or salinity in the ocean , or whether changes in either heat flux, water flux, or wind stress between atmosphere and ocean play a key role. Here, using the climate model, MIROC4m, we investigate the detailed role of each flux (heat, water, wind) between atmosphere and ocean in driving millennial-scale oscillations. For this purpose, we perform several sensitivity experiments in which atmosphere-ocean flux passed to the sea surface are fixed to climatology and compare the results with a full-coupled atmosphere-ocean experiment. We discuss implications on the mechanism of the DO events and the background conditions for the millennial-scale variability.