地球轨道对北大西洋淡水注入影响印度夏季风的调节作用:以8.2 ka和4.2 ka事件为例  

ORBITAL MODULATION OF INDIAN SUMMER MONSOON RESPONSE TO NORTH ATLANTIC FRESHWATER FORCING:CASE STUDY OF 8.2 KA AND 4.2 KA EVENTS

作　　者：王硕情 郑珮盈 张肖剑 WANG Shuoqing;ZHENG Peiying;ZHANG Xiaojian(School of Geography and Ocean Science,Nanjing University,Nanjing 210023,Jiangsu;Frontiers Science Center for Critical Earth Material Cycling,Nanjing University,Nanjing 210023,Jiangsu)

机构地区：[1]南京大学地理与海洋科学学院,江苏南京210023 [2]南京大学关键地球物质循环前沿科学中心,江苏南京210023

出　　处：《第四纪研究》2023年第4期1133-1145,共13页Quaternary Sciences

基　　金：国家自然科学基金项目(批准号:42171152和41901091);国家自然科学基金重点国际(地区)合作研究项目(批准号:41920104005);中央高校基本科研业务费专项项目(批准号:0209-14380107);南京大学关键地球物质循环前沿科学中心“科技人才团队”项目;省级大学生创新创业训练计划支持项目(批准号:202210284358Y)共同资助。

摘　　要：北大西洋淡水注入触发的千年尺度气候突变事件发生在不同地球轨道背景下,理解地球轨道参数对印度夏季风千年尺度变率特征的调节作用,对理解未来印度夏季风对北大西洋淡水注入的响应具有重要的科学意义。本研究利用通用地球系统模式CESM,探讨印度夏季风在8.2 ka B.P.和4.2 ka B.P.对相同北大西洋淡水注入的响应差异。模拟结果显示,北大西洋淡水注入使得印度夏季风强度显著减弱,其中夏季风降水变化在这两次事件中没有显著的空间差异,但变化幅度在4.2 ka B.P.要显著大于其在8.2 ka B.P.,表明地球轨道参数对印度夏季风千年尺度变率特征具有重要的调节作用。进一步分析显示,地球轨道并非通过影响温盐环流强度进行调节,而与夏季太阳辐射的高低有关。在4.2 ka B.P.时,在相同的淡水注入下,由于夏季太阳辐射较低,加剧了北大西洋的降温,同时也增强了其对下游大气的冷却作用,使得欧亚大陆南部对流层中上层大气具有更大的降温幅度,这进一步削弱了欧亚大陆南部与赤道印度洋对流层中上层大气的经向温度梯度,从而导致印度夏季风相较于8.2 ka B.P.具有更大的衰退幅度。因此,在较低夏季太阳辐射背景下,印度夏季风对北大西洋淡水注入的响应更为敏感。The Indian summer monsoon(ISM),which is the dominant factor controlling precipitation changes in South Asia,Southeast Asia,and Southwest China(5°~25°N,60°~110°E),is sensitive to the variability of the Atlantic meridional overturning circulation(AMOC)resulting from the input of the freshwater into the North Atlantic.Understanding millennial⁃scale ISM variability is critical for climate projection in ISM⁃controlled regions in the context of slowing AMOC caused by global warming.This study intends to explore the modulation of the Earth's orbital parameters in the ISM response to North Atlantic freshwater forcing based on climate simulations using the Community Earth System Model(CESM).We performed two groups of sensitivity experiments at 8.2 ka B.P.and 4.2 ka B.P.,respectively,during which the orbital parameters are significant different.In the control runs(Exp_8.2ka and Exp_4.2ka),the orbital parameters were set at the conditions of 8.2 ka B.P.and 4.2 ka B.P.,respectively.The concentrations of greenhouse gases(CO_(2),CH4,N2O)were set to the values at 8.2 ka B.P.for both the Exp_8.2ka and Exp_4.2ka,to exclude the possible effect of the greenhouse gases.In the sensitivity experiments(Exp_8.2ka_FW and Exp_4.2ka_FW),we added additional 0.2 Sv freshwater into the North Atlantic.The orbital parameters and greenhouse gases concentrations of the Exp_8.2ka_FW and Exp_4.2ka_FW were kept the same with the Exp_8.2ka and Exp_4.2ka,respectively.We compared their differences(Exp_8.2ka_FW minus Exp_8.2ka and Exp_4.2ka_FW minus Exp_4.2ka)to evaluate the effect of the Earth's orbital parameters on the ISM response to North Atlantic freshwater forcing.Simulation results reveal significantly weakened AMOC and ISM precipitation both at 8.2 ka B.P.and 4.2 ka B.P.with the freshwater forcing.There was no significant difference in the spatial pattern of precipitation changes between 8.2 ka B.P.and 4.2 ka B.P.However,ISM precipitation experienced a much greater reduction at 4.2 ka B.P.than at 8.2 ka B.P.,suggesting an important role

关 键 词：印度夏季风 淡水强迫 太阳辐射 古气候模拟 温盐环流 

分 类 号：P467[天文地球—大气科学及气象学]