Global monsoon in a geological perspective
Global monsoon in a geological perspective
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DOI：
10.1007/s11434-009-0169-4
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发表时间：
2009-04
影响因子：
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通讯作者：
Pinxian Wang
中科院分区：
文献类型：
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作者：
Pinxian Wang
季风现在被认为是一个全球性的系统，而不仅仅是区域性的现象。300多年来，季风一直被认为是一种巨大的陆海空风，但现在卫星和常规观测支持另一种假设，认为季风是热带辐合带（ITCZ）季节性迁移的表现，因此是全球尺度的气候系统。季风作为一种低纬度气候系统，存在于除南极洲以外的所有大陆，并贯穿了至少自显生宙以来的所有地质历史。地质记录表明，在构造时间尺度上（106- 108 a），全球季风受威尔逊旋回控制。一个“巨型大陆”产生“巨型季风”，它的崩溃导致季风强度减弱。在104- 105 a时间尺度上，全球季风表现出约20 ka的岁差周期和100 ka和400 ka的离心率周期，即轨道周期。在103 a及以下的时间尺度上，全球季风强度受太阳活动周期等因素的调制。全球季风的周期性是地球表层系统变化和人类社会环境变化的基本因素之一。全球季风的400-ka长的偏心周期被比作地球系统的“心跳”，全球季风的岁差周期是导致亚洲和非洲几个古老文化在104000年前崩溃的原因，而太阳周期导致玛雅文明在大约1000年前灭亡。因此，古气候学不仅应关注以冰盖变化为中心的高纬度过程，还应关注低纬度过程，如季风，因为后者在地质历史中比冰川作用更为常见。
Monsoon is now considered as a global system rather than regional phenomena only. For over 300 years, monsoon has been viewed as a gigantic land-sea breeze, but now satellite and conventional observations support an alternative hypothesis which considers monsoon as a manifestation of seasonal migration of the intertropical convergence zone (ITCZ) and, hence, a climate system of the global scale. As a low-latitude climate system, monsoon exists over all continents but Antarctica, and through all the geological history at least since the Phenorozoic. The time is ripe for systematical studies of monsoon variations in space and time.As evidenced by the geological records, the global monsoon is controlled by the Wilson cycle on the tectonic time scale (106–108a). A “Mega-continent” produces “Mega-monsoon”, and its breakdown leads to weakening of the monsoon intensity. On the time scales of 104-105a, the global monsoon displays the precessional cycles of ∼20 ka and eccentricity cycles of 100- and 400-ka, i.e. the orbital cycles. On the time scales of 103a and below, the global monsoon intensity is modulated by solar cycles and other factors. The cyclicity of global monsoon represents one of the fundamental factors responsible for variations in the Earth surface system as well as for the environmental changes of the human society. The 400-ka long eccentricity cycles of the global monsoon is likened to “heartbeat” of the Earth system, and the precession cycle of the global monsoon was responsible for the collapse of several Asian and African ancient cultures at ∼4000 years ago, whereas the Solar cycles led to the demise of the Maya civilization about a thousand years ago. Therefore, paleoclimatology should be focused not only on the high-latitude processes centered at ice cap variations, but also on the low-latitude processes such as monsoons, as the latter are much more common in the geological history compared to the glaciations.