The African monsoon during the early Eocene from the DeepMIP simulations
The African monsoon during the early Eocene from the DeepMIP simulations
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DeepMIP 模拟中始新世早期的非洲季风
DOI：
10.1002/essoar.10510285.1
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Williams C
中科院分区：
文献类型：
--
作者：
Williams C
始新世早期（约5600 - 4800万年前）的特征是高二氧化碳估计值（1200-2500 ppmv）和全球气温升高（比现代高约10至16°C）。然而，在始新世早期的水文循环的反应是不受约束的，特别是在数据覆盖稀疏的地区（如非洲）。在这里，我们提出了一个研究非洲水文气候在始新世早期，模拟国家的最先进的气候模型在深时间模型相互比较项目（DeepMIP）的合奏。DeepMIP工业前模拟和现代观测之间的比较表明，模型偏差是模型和地理依赖的，但是这些偏差在模型集合平均值中有所减少。始新世的模拟和工业化前的比较表明，有没有明显的润湿或干燥的趋势，CO2的增加。结果表明，在模型中的陆地海洋面具（相对于现代）的变化可能是负责模拟的降水量增加到非洲北部的始新世，而它很可能是在模型中的植被的变化是负责模拟区域的干燥赤道始新世非洲。随着CO2的增加，赤道非洲和西非的降水量增加，北方非洲的干旱也随之增加。也有重要的动力学变化，有证据表明，反气旋低层环流被取代增加西南气流在高CO2水平。最后，使用新编制的定量气候估计从古植物学代理数据的模型数据比较表明，在较低水平的CO2的重建稍微更适合。
The early Eocene (~56-48 million years ago) is characterised by high CO2 estimates (1200-2500 ppmv) and elevated global temperatures (~10 to 16°C higher than modern). However, the response of the hydrological cycle during the early Eocene is poorly constrained, especially in regions with sparse data coverage (e.g. Africa). Here we present a study of African hydroclimate during the early Eocene, as simulated by an ensemble of state-of-the-art climate models in the Deep-time Model Intercomparison Project (DeepMIP). A comparison between the DeepMIP pre-industrial simulations and modern observations suggests that model biases are model- and geographically dependent, however these biases are reduced in the model ensemble mean. A comparison between the Eocene simulations and the pre-industrial suggests that there is no obvious wetting or drying trend as the CO2 increases. The results suggest that changes to the land sea mask (relative to modern) in the models may be responsible for the simulated increases in precipitation to the north of Eocene Africa, whereas it is likely that changes in vegetation in the models are responsible for the simulated region of drying over equatorial Eocene Africa. There is an increase in precipitation over equatorial and West Africa and associated drying over northern Africa as CO2 rises. There are also important dynamical changes, with evidence that anticyclonic low-level circulation is replaced by increased south-westerly flow at high CO2 levels. Lastly, a model-data comparison using newly-compiled quantitative climate estimates from palaeobotanical proxy data suggests a marginally better fit with the reconstructions at lower levels of CO2.