欧-亚-非大陆季风:超级大陆与超级季风的雏形

European-Asian-African continent:An early form of supercontinent and supermonsoon

欧洲-亚洲-非洲大陆聚集在一起,占地球陆地面积的一半以上(约56%),整体上可以近似看作是超级大陆的"雏形";相应地,广泛分布的亚洲-非洲季风-干旱气候系统也可以近似为超级季风-干旱系统的"雏形"。对这一巨大气候体系的研究不仅本身有十分重要的理论和实际意义,同时也能够为研究潘基亚超级大陆-超级季风系统及其演化提供现代或第四纪的"相似型"。晚更新世-全新世地质记录和气候模拟结果表明亚洲-非洲夏季风气候变化主要响应北半球夏季太阳辐射变化;南北半球季风变化在岁差尺度上的相位关系近于相反;西风环流影响下的中亚干旱-半干旱区气候变化在岁差尺度上与亚洲季风也接近同相位变化;亚洲-非洲季风-干旱气候系统的这些变化在岁差尺度上领先于全球冰量的变化。总体上,似乎可以提出这样一种假说:受到地球轨道偏心率幅度调谐的太阳辐射在岁差尺度的周期波动可能是季风-干旱气候在轨道尺度上的主导"韵律",包括潘基亚超级大陆季风气候在轨道尺度上的变化。第四纪欧洲-亚洲-非洲"超级大陆"及其季风-干旱系统本质上与潘基亚超级大陆的季风-干旱系统有着一定程度的相似性,因此研究前者是理解后者(所谓将今论古)的重要途径之一,对解译深时"碎片"化的地质记录有实际意义。

The assembled European,Asian and African continents,accounting more than half(ca.56%)of the Earth's landmass,and the corresponding Afro-Asian monsoon-dry-region system may be viewed as the early forms of super-continent and supermonsoon-arid-zone system.A comprehensive understanding of the vast Afro-Asian monsoon-dry region system is important from both theoretical and socioeconomic standpoints.Additionally,this understanding may also provide an important"analog"to probe the climate variations in the Pangean supermonsoon-arid-zone system across the low to middle latitude of the Pangean supercontinent and its change in the context of the continental breakup.Myriad empirical records and modeling results show that Afro-Asian monsoon variations broadly follow the summer insolation changes,manifesting significant precession cycles with a nearly anti-phase relation between Northern and Southern Hemisphere.Furthermore,the orbital-scale climate variations of the Afro-Asian monsoon and the accompanied large atmospheric circulation in the Asian Westerly arid-zone are approximately in-phase at the precession band.The Afro-Asian monsoon-arid Westerlies climate variations also lead the global ice volume change at the precession band.We suggest that the dominant orbital rhythm is eccentricity-modulated precession cycles in monsoon-arid-zone systems including the Pangean supermonsoon-arid-zone system.Regarding climatic dynamics,it appears that the Afro-Asian monsoon-arid-zone system has substantial similarity with the monsoon-arid-zone systems companied with the continent evolution at different stages during the Pangean supercontinent breakup.As such,it is critical to understand the Quaternary climate dynamics of the Afro-Asian monsoon-arid-zone system,which may provide key insight into the similar climate systems in deep time when the climate records are largely fragmented.