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Climate of the Past An interactive open-access journal of the European Geosciences Union
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Volume 14, issue 11 | Copyright

Special issue: Paleoclimate Modelling Intercomparison Project phase 4 (PMIP4)...

Clim. Past, 14, 1565-1581, 2018
https://doi.org/10.5194/cp-14-1565-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 01 Nov 2018

Research article | 01 Nov 2018

Effect of high dust amount on surface temperature during the Last Glacial Maximum: a modelling study using MIROC-ESM

Rumi Ohgaito1, Ayako Abe-Ouchi2,1, Ryouta O'ishi2, Toshihiko Takemura3, Akinori Ito1, Tomohiro Hajima1, Shingo Watanabe1, and Michio Kawamiya1 Rumi Ohgaito et al.
  • 1Japan Agency for Marine-Earth Science and Technology, Yokohama, 236-0001, Japan
  • 2Atmosphere Ocean Research Institute, University of Tokyo, Kashiwa, Chiba 277-8564, Japan
  • 3Research Institute for Applied Mechanics, Kyushu University, Fukuoka, 816-8580, Japan

Abstract. The effect of aerosols is one of many uncertain factors in projections of future climate. However, the behaviour of mineral dust aerosols (dust) can be investigated within the context of past climate change. The Last Glacial Maximum (LGM) is known to have had enhanced dust deposition in comparison with the present, especially over polar regions. Using the Model for Interdisciplinary Research on Climate Earth System Model (MIROC-ESM), we conducted a standard LGM experiment following the protocol of the Paleoclimate Modelling Intercomparison Project phase 3 and sensitivity experiments. We imposed glaciogenic dust on the standard LGM experiment and investigated the impacts of glaciogenic dust and non-glaciogenic dust on the LGM climate. Global mean radiative perturbations by glaciogenic and non-glaciogenic dust were both negative, consistent with previous studies. However, glaciogenic dust behaved differently in specific regions; e.g. it resulted in less cooling over the polar regions. One of the major reasons for reduced cooling is the ageing of snow or ice, which results in albedo reduction via high dust deposition, especially near sources of high glaciogenic dust emission. Although the net radiative perturbations in the lee of high glaciogenic dust provenances are negative, warming by the ageing of snow overcomes this radiative perturbation in the Northern Hemisphere. In contrast, the radiative perturbation due to high dust loading in the troposphere acts to warm the surface in areas surrounding Antarctica, primarily via the longwave aerosol–cloud interaction of dust, and it is likely the result of the greenhouse effect attributable to the enhanced cloud fraction in the upper troposphere. Although our analysis focused mainly on the results of experiments using the atmospheric part of the MIROC-ESM, we also conducted full MIROC-ESM experiments for an initial examination of the effect of glaciogenic dust on the oceanic general circulation module. A long-term trend of enhanced warming was observed in the Northern Hemisphere with increased glaciogenic dust; however, the level of warming around Antarctica remained almost unchanged, even after extended coupling with the ocean.

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The behaviour of dust in terms of climate can be investigated using past climate. The Last Glacial Maximum (LGM; 21000 years before present) is known to be dustier. We investigated the impact of plausible dust distribution on the climate of the LGM using an Earth system model and found that the higher dust load results in less cooling over the polar regions. The main finding is that radiative perturbation by the high dust loading does not necessarily cool the surface surrounding Antarctica.
The behaviour of dust in terms of climate can be investigated using past climate. The Last...
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