[M-IS18] Paleoclimatology and paleoceanography

[MIS18-25] Polar amplifications in the Cretaceous with changes in atmospheric CO2 concentration and orbital parameters

*Taro Higuchi¹, Ayako Abe-Ouchi¹, Wing-Le Chan¹, Ryouta O'ishi¹, Takanori Kodama² (1.Atmospheric and Ocean Research Institute, the University of Tokyo, 2.The University of Tokyo)

Keywords:polar amplification, Cretaceous

Polar amplification is the phenomenon that external radiative forcing produces a larger change in surface temperature at high latitudes than the global average. Future climate change simulations show a polar amplification with the emission of anthropogenic greenhouse gasses and global warming. Additionally, it is known that, in times like the last interglacial, the orbital parameters different from those in the present day are attributed to a polar amplification in that time ( O'ishi et al., 2021; Otto-Bliesner et al., 2021). Also, Cretaceous proxies indicate remarkable temperature amplifications in the high-latitude and polar region (e.g., Jenkyns et al. 2004 ), resulting in small equator-to-polar temperature difference. Many previous studies have been conducted in order to elucidate the mechanism (Upchurch et al., 2015; Niezgodzki et al., 2017). In this study, we systematically investigated the responses of the polar temperatures in the Cretaceous to changes in atmospheric CO2 concentration and the orbital parameters using an atmospheric-ocean-vegetation fully coupled model MIROC4m-LPJ, and compared it with the proxy data. Additionally, we show the differences of the polar amplifications in the Cretaceous and present-day geographical conditions. Also, change of hydrological cycle is discussed.