A ∼12 Myr Miocene Record of East Asian Monsoon Variability From the South China Sea
A ∼12 Myr Miocene Record of East Asian Monsoon Variability From the South China Sea
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DOI：
10.1029/2021pa004267
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发表时间：
2021-07-01
影响因子：
3.5
通讯作者：
Heslop, David
中科院分区：
文献类型：
--
作者：
Holbourn, Ann;Kuhnt, Wolfgang;Heslop, David
东亚季风的长期演变以及在不断变化的气候边界条件下控制其变率的过程仍然是个谜。在这里，我们将新发布的高分辨率浮游和底栖有孔虫同位素数据与源自海洋钻探计划站点 1146（南海）漫反射光谱的化学风化代理记录相结合，以重建大约 17 至 5 Ma 之间夏季风的演变。我们的记录显示，在中新世气候最适宜期，东南亚普遍存在温暖湿润的热带气候，这表明热带雨带因温室气体强迫而向北扩张。相比之下，在中新世中期气候转变期间，季风季节性随着南极冰川扩张和全球变冷而增强。大约12.7和10.9 Ma之间夏季季风的大幅减弱支持了碳酸盐崩溃期间风化作用和河流输入的营养物和碱度的减少导致了深海碳酸盐的消耗。中新世晚期季风环流的强化和生物泵的加强促进了生物爆发期间的碳埋藏、大气二氧化碳的减少和气候变冷。这些结果强调了东亚季风在中新世中晚期的动态演变。当地日照强迫和南半球冰量的变化影响纬度温度梯度、蒸发-水分收支和热带对流的强度，对季风的发展发挥着重要的控制作用。
The long-term evolution of the East Asian Monsoon and the processes controlling its variability under changing climate boundary conditions remain enigmatic. Here, we integrate new and published high-resolution planktic and benthic foraminiferal isotope data with proxy records for chemical weathering derived from diffuse reflectance spectroscopy at Ocean Drilling Program Site 1146 (South China Sea) to reconstruct the evolution of the summer monsoon between similar to 17 and 5 Ma. Our records show that an overall warm and humid tropical climate prevailed over southeastern Asia during the Miocene Climatic Optimum, suggesting northward expansion of the tropical rain belt in response to greenhouse gas forcing. By contrast, monsoon seasonality increased during the middle Miocene Climatic Transition in tandem with Antarctic glacial expansion and global cooling. Substantial weakening of the summer monsoon between similar to 12.7 and 10.9 Ma supports that decreased weathering and riverine input of nutrients and alkalinity contributed to carbonate depletion in the deep ocean during the Carbonate Crash. Intensification of monsoonal circulation and strengthening of the biological pump through the late Miocene promoted carbon burial, drawdown of atmospheric CO2, and climate cooling during the Biogenic Bloom. These results underscore the dynamic evolution of the East Asian Monsoon throughout the middle to late Miocene. Variations in local insolation forcing and in Southern Hemisphere ice volume, influencing the latitudinal thermal gradient, evaporation-moisture budgets, and the strength of the tropical convection, exerted major controls on the development of the monsoon.