Radiative forcing of climate by ice-age atmospheric dust
Radiative forcing of climate by ice-age atmospheric dust
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DOI：
10.1007/s00382-002-0269-1
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发表时间：
2003
期刊：
影响因子：
4.6
通讯作者：
T. Claquin;A. Roelandt;Ae K E Kohfeld;A. Harrison;I. Tegen;Ae I C Prentice;Ae Y Balkanski;Ae G Bergametti;M. Hansson;Ae N Mahowald;Ae H Rodhe;Ae M Schulz
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文献类型：
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作者：
T. Claquin;A. Roelandt;Ae K E Kohfeld;A. Harrison;I. Tegen;Ae I C Prentice;Ae Y Balkanski;Ae G Bergametti;M. Hansson;Ae N Mahowald;Ae H Rodhe;Ae M Schulz
在冰河时期，全球范围内的灰尘沉积速率和推断的大气浓度都比现在高得多。根据最近的模式结果，大气尘埃含量在末次盛冰期（LGM）的大幅增加，可以解释只有在潜在的灰尘源区的增加被考虑在内。由于降水量少和大气中二氧化碳含量低对植物生长的影响，这种增加是可以预料的。在这里，Mahowald等人的模拟三维尘埃场和模拟的季节性变化的表面散射场以平行的方式导出，被用来量化由于现代（非人为）和末次冰期尘埃的平均辐射强迫。矿物学来源的尘埃的辐射特性的影响被考虑在内，是与尘埃粒子的混合状态的不确定性相关的光学特性的范围。高纬度（45°向极）的平均强迫变化（LGM减去现代）估计很小（-0.9至+0.2 W m-2），特别是与来自扩展冰盖的反射的近-20 W m-2相比。虽然冰盖上的灰尘的净效应是一个积极的强迫（变暖），大部分的模拟高纬度灰尘不是在冰盖上，但在未冰川化的地区接近扩大的沙尘源区在中亚。在热带地区，强迫的变化估计为总体负值，与低层大气（CO2）的辐射冷却效应具有类似的大幅度（-2.2至-3.2 W m-2）。因此，末次冰期尘埃最大的长期气候影响可能是热带地区的冷却。热带海洋表面温度低，低大气（CO2）和高大气粉尘负荷可能是相互加强，由于多重正反馈，包括粉尘的负辐射强迫效应。
During glacial periods, dust deposition rates and inferred atmospheric concentrations were globally much higher than present. According to recent model results, the large enhancement of atmospheric dust content at the last glacial maximum (LGM) can be explained only if increases in the potential dust source areas are taken into account. Such increases are to be expected, due to effects of low precipitation and low atmospheric (CO2) on plant growth. Here the modelled three-dimensional dust fields from Mahowald et al. and modelled seasonally varying surface-albedo fields derived in a parallel manner, are used to quantify the mean radiative forcing due to modern (non-anthropogenic) and LGM dust. The effect of mineralogical provenance on the radiative properties of the dust is taken into account, as is the range of optical properties associated with uncertainties about the mixing state of the dust particles. The high-latitude (poleward of 45°) mean change in forcing (LGM minus modern) is estimated to be small (–0.9 to +0.2 W m–2), especially when compared to nearly –20 W m–2due to reflection from the extended ice sheets. Although the net effect of dust over ice sheets is a positive forcing (warming), much of the simulated high-latitude dust was not over the ice sheets, but over unglaciated regions close to the expanded dust source region in central Asia. In the tropics the change in forcing is estimated to be overall negative, and of similarly large magnitude (–2.2 to –3.2 W m–2) to the radiative cooling effect of low atmospheric (CO2). Thus, the largest long-term climatic effect of the LGM dust is likely to have been a cooling of the tropics. Low tropical sea-surface temperatures, low atmospheric (CO2) and high atmospheric dust loading may be mutually reinforcing due to multiple positive feedbacks, including the negative radiative forcing effect of dust.