Abstract
Abstract. Possible feedback effects between aeolian dust, climate and ice sheets are studied for the first time with an Earth system model of intermediate complexity over the late Pleistocene period. Correlations between climate and dust deposition records suggest that aeolian dust potentially plays an important role for the evolution of glacial cycles. Here climatic effects from the dust direct radiative forcing (DRF) caused by absorption and scattering of solar radiation are investigated. Key elements controlling the dust DRF are the atmospheric dust distribution and the absorption-scattering efficiency of dust aerosols. Effective physical parameters in the description of these elements are varied within uncertainty ranges known from available data and detailed model studies. Although the parameters can be reasonably constrained, the simulated dust DRF spans a~wide uncertainty range related to the strong nonlinearity of the Earth system. In our simulations, the dust DRF is highly localized. Medium-range parameters result in negative DRF of several watts per square metre in regions close to major dust sources and negligible values elsewhere. In the case of high absorption efficiency, the local dust DRF can reach positive values and the global mean DRF can be insignificantly small. In the case of low absorption efficiency, the dust DRF can produce a significant global cooling in glacial periods, which leads to a doubling of the maximum glacial ice volume relative to the case with small dust DRF. DRF-induced temperature and precipitation changes can either be attenuated or amplified through a feedback loop involving the dust cycle. The sensitivity experiments suggest that depending on dust optical parameters, dust DRF has the potential to either damp or reinforce glacial–interglacial climate changes.
Highlights
Mineral dust aerosols are abundant in the atmosphere and have the potential to alter the energy budget of the Earth by inducing a radiative forcing at the top of the atmosphere (TOA) via absorbing and scattering of radiation fluxes
Colour shading and line width as in Aeolian dust potentially plays an important role in understanding the Pleistocene ice ages, which is suggested by correlations between climate and dust deposition records
The present study presents transient simulations of glacial cycles using the CLIMBER-2 model, which includes models for the atmosphere, the ocean, the vegetation, the ice sheets and the aeolian dust cycle
Summary
Mineral dust aerosols are abundant in the atmosphere and have the potential to alter the energy budget of the Earth by inducing a radiative forcing at the top of the atmosphere (TOA) via absorbing and scattering of radiation fluxes. The dust radiative forcing at TOA depends on dust load and particle size distribution and varies with climate variables such as radiation fluxes, surface albedo and cloudiness. Calculations of the direct dust radiative forcing at TOA with a global climate model for LGM and present-day time slices by Claquin et al (2003) utilize the dust fields simulated by Mahowald et al (1999). These dust fields are vertically integrated and transformed to aerosol optical thickness (AOT) at a wavelength of 0.55 μm, resulting in mean AOT of 0.14 and 0.05 for LGM and modern climates, respectively.
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