Clim. Past, 17, 95–110, 2021 https://doi.org/10.5194/cp-17-95-2021 © Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License. Impact of mid-glacial ice sheets on deep ocean circulation and global climate Sam Sherriff-Tadano, Ayako Abe-Ouchi, and Akira Oka Atmosphere and Ocean Research Institute, the University of Tokyo, Kashiwa, Japan Correspondence: Sam Sherriff-Tadano (
[email protected]) Received: 27 May 2020 – Discussion started: 12 June 2020 Revised: 25 September 2020 – Accepted: 10 November 2020 – Published: 12 January 2021 Abstract. This study explores the effect of southward ex- 1 Introduction pansion of Northern Hemisphere (American) mid-glacial ice sheets on the global climate and the Atlantic Meridional During the last glacial period, ice sheets evolved drasti- Overturning Circulation (AMOC) as well as the processes cally over the northern continent (Lisiecki and Raymo, 2005; by which the ice sheets modify the AMOC. For this pur- Clark et al., 2009; Grant et al., 2012; Spratt and Lisiecki, pose, simulations of Marine Isotope Stage (MIS) 3 (36 ka) 2016, Fig. 1). After the initiation of the Northern Hemisphere and 5a (80 ka) are performed with an atmosphere–ocean gen- glacial ice sheets at the end of the last interglacial, the ice eral circulation model. In the MIS3 and MIS5a simulations, sheets expanded over northern North America and northern the global average temperature decreases by 5.0 and 2.2 ◦C, Europe during the early glacial period, Marine Isotope Stage respectively, compared with the preindustrial climate sim- 5d-a (MIS5d-a, 123–71 ka; Lisiecki and Raymo, 2005), ulation.