[A-CC37] [EJ] Ice cores and past environmental changes

[ACC37-11] High glacial dust amount worked to warm the polar regions at the Last Glacial Maximum: a modelling study using MIROC-ESM

★Invited papers

*Rumi Ohgaito¹, Ayako Abe-Ouchi², Ryouta O'ishi², Toshihiko Takemura³, Shingo Watanabe¹, Michio Kawamiya¹ (1.Japan Agency for Marine-Earth Science and Technology, 2.Atmosphere-Ocean Research Institute, Univ. of Tokyo, 3.Research Institute for Applied Mechanics, Kyushu University)

Keywords:Dust, LGM

Aerosol and its impacts on climate is one of uncertain factors on future climate projection. One of the aerosol species, mineral dust aerosol (dust) can be investigated with the past climate changes. Especially, need of more investigation of the feedback of dust and vegetation under the different climatic condition compared to present day is repeatedly mentioned in the paleoclimate chapter of Intergovermental Panel on Climate Change 5^th Assessment Report. Last Glacial Maximum (LGM, c.a. 21,000 years before present) is known with the enhancement of dust, globally but especially over the high latitude regions from the ice core and sediment core proxy data (Winkler et al. 2008, Lamy et al. 2014). It has been difficult to reproduce dust amount over the high latitudes with General Circulation Models (GCMs) at LGM and the effect of dust on high latitudes has not been cleared. The previous works used atmospheric part of GCM or Earth System Model (ESM) (Mahowald et al. 2006, Takemura et al. 2009, Albani et al. 2012, Hopcroft et al. 2015). For the first time, using an ESM, MIROC-ESM (Watanabe et al. 2011), we tested the impact of enhanced dust on LGM climate with adding glaciogenic dust (Mahowald et al. 2006) (hereafter, called LGMglac) on a standard LGM simulation following the Paleoclimate Modelling Intercomparison Project phase 3 (PMIP3) protocol (Sueyoshi et al. 2013). The resulting deposition distribution of dust in LGMglac matched better to the latest global dust data archives (Kohfeld et al. 2013, Albani et al. 2014). The experiment LGM is the identical with the one for PMIP3. LGMglac deviated from the LGM in a spin-up stage and the corresponding period with the LGM experiment is taken for the analyses. We have found that the high LGM dust amount warms the northern high latitudes and the surrounding of the Antarctica. Sensitivity experiments using atmospheric part of MIROC-ESM suggested that both of radiative forcing and the aging of snow and ice albedo by dust are important for the LGMglac-LGM warming in the northern hemisphere. One the other hand, over the Antarctica, the positive radiative forcing at surface plays a role for the warming with additional dust but the effect on the surface temperature of the high glacial dust amount is a little at the borehole sites over the high plateau of the Antarctica.