[A-CC26] Ice cores and paleoenvironmental modeling

[ACC26-P06] Transient simulations of the last deglaciation using MIROC AOGCM and time evolving ice-topography

*Tristan Vadsaria¹, Takashi Obase¹, Ayako Abe-Ouchi¹, Sam Sherriff-Tadano ^2,1, Wing-Le Chan¹ (1.Atmosphere and Ocean Research Institute, The University of Tokyo, Japan, 2.School of Earth and Environment, The University of Leeds, Leeds, UK)

Keywords:Last deglaciation, Transient experiments, Hosing experiments, PMIP protocol

The last deglaciation (from 21 to 9 ka BP, also called T1) is the transition from the last glacial maximum (LGM) to the present interglacial. From the LGM, the increase in global temperature rise was about +4°C to +6°C and the Atlantic Meridional Overturning Circulation was largely affected. Previous transient simulations were performed at the University of Tokyo, using transient greenhouse gases (GHC) and orbital parameters with LGM ice sheet topography and bathymetry throughout the simulation (Obase & Abe-Ouchi., 2019). The previous study shows that abrupt AMOC increase, associated with the Bolling-Allerod (BA, about 14.7 to 14.2 ka BP) event, can be caused by gradual warming induced by orbital and greenhouse gases forcing without meltwater addition, and, that different hosing transient experiments using meltwater reconstruction affect the BA event timing.

The aim of the current study is to realize similar transient experiment using time-evolving ice-sheet according to recent reconstruction (ICE-5G, Peltier et al., 2015). To date, several simulations using this protocol and the same model as Obase & Abe-Ouchi. (2019), have been performed with sensitivity to freshwater discharge after 16 ka BP (when northern ice-sheet retreat is accelerated) and ocean bathymetry.

To equivalent freshwater forcing – i.e., 0.04 Sv applied uniformly between 50 and 70°N after 16 ka (“control” run in Obase & Abe-Ouchi., 2019) – the retreat of the northern ice sheet induces warming in the ice sheet margins especially over northern America Abrupt warming occurred simultaneously (about 15.5 ka) in hosing experiments (time-evolving ice-sheet vs fixed ice-sheet). This timing is delayed when greater meltwater is applied (0.05Sv) inducing a Greenland warming in good agreement with temperature proxies, in term of timing (14.5 ka) and amplitude (about +10°C within 500 years).