GAIA Antartica Research Center, University of Magallanes, Punta Arenas, Chile;
Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen OE, Denmark.
Proc Natl Acad Sci U S A. 2018 Feb 27;115(9):2026-2031. doi: 10.1073/pnas.1708174115. Epub 2018 Feb 12.
Mineral dust aerosols cool Earth directly by scattering incoming solar radiation and indirectly by affecting clouds and biogeochemical cycles. Recent Earth history has featured quasi-100,000-y, glacial-interglacial climate cycles with lower/higher temperatures and greenhouse gas concentrations during glacials/interglacials. Global average, glacial maxima dust levels were more than 3 times higher than during interglacials, thereby contributing to glacial cooling. However, the timing, strength, and overall role of dust-climate feedbacks over these cycles remain unclear. Here we use dust deposition data and temperature reconstructions from ice sheet, ocean sediment, and land archives to construct dust-climate relationships. Although absolute dust deposition rates vary greatly among these archives, they all exhibit striking, nonlinear increases toward coldest glacial conditions. From these relationships and reconstructed temperature time series, we diagnose glacial-interglacial time series of dust radiative forcing and iron fertilization of ocean biota, and use these time series to force Earth system model simulations. The results of these simulations show that dust-climate feedbacks, perhaps set off by orbital forcing, push the system in and out of extreme cold conditions such as glacial maxima. Without these dust effects, glacial temperature and atmospheric CO concentrations would have been much more stable at higher, intermediate glacial levels. The structure of residual anomalies over the glacial-interglacial climate cycles after subtraction of dust effects provides constraints for the strength and timing of other processes governing these cycles.
矿物质粉尘气溶胶通过散射入射太阳辐射直接冷却地球，也通过影响云和气溶胶生物地球化学循环间接冷却地球。最近的地球历史具有准 10 万年的冰川-间冰期气候循环，冰川期和间冰期的温度和温室气体浓度较低/较高。全球平均而言，冰川期的粉尘水平比间冰期高出 3 倍以上，从而导致了冰川期的冷却。然而，这些周期中粉尘-气候反馈的时间、强度和总体作用仍不清楚。在这里，我们使用来自冰盖、海洋沉积物和陆地档案的粉尘沉积数据和温度重建来构建粉尘-气候关系。尽管这些档案中的绝对粉尘沉积速率差异很大，但它们都表现出向最冷冰川条件的显著非线性增加。从这些关系和重建的温度时间序列中，我们诊断了冰川-间冰期粉尘辐射强迫和海洋生物铁肥化的时间序列，并使用这些时间序列来驱动地球系统模型模拟。这些模拟的结果表明，粉尘-气候反馈（可能是由轨道强迫引发的）将系统推向和推出极端寒冷条件，如冰川期最大值。如果没有这些粉尘效应，冰川温度和大气 CO 浓度在较高的中间冰川水平下将更加稳定。在扣除粉尘效应后，残留异常在冰川-间冰期气候循环中的结构为控制这些循环的其他过程的强度和时间提供了约束。
