摘要
地球气候以频繁冷暖波动为特征,在百万年时间尺度上可划分为温室期和冰室期,期间发生持续时间相对短的极热和极冷事件.大多数学者将这些温室期、冰室期以及极热和极冷事件归因于大气CO_(2)浓度变化,即地球深部碳释放和表层碳消耗之间的动态平衡.地球深部碳是CO_(2)的主要来源,通过大火成岩省、俯冲带、裂谷岩浆活动等过程释放到大气中,从而引发全球增温.但是,深部过程又可通过4种途径引发降温:(1)火山活动释放SO_(2)形成硫酸盐气溶胶,导致“火山冬天”;(2)岩浆活动峰期之后的化学风化消耗大气CO_(2),其中,镁铁质岩化学风化速率高于长英质岩,降温作用更显著;(3)火山喷发及岩浆岩化学风化释放营养元素,促进大洋初级生产力,加快碳埋藏;(4)板块运动增大陆地面积以及使大陆聚集于高温、湿润的低纬地区,增强化学风化对CO_(2)的消耗.大体上,温室和冰室气候与俯冲带大陆弧岩浆活动强度(通常用大陆弧长度和年轻碎屑锆石相对丰度指代)及低纬地区弧-陆碰撞带长度有关,如果大陆弧活跃且低纬地区弧-陆碰撞带规模小,易形成温室气候,反之则形成冰室气候.极热事件普遍由镁铁质大火成岩省的快速巨量碳释放引发;极冷事件成因较为复杂,例如低纬地区大火成岩省强烈化学风化(如前寒武纪斯图特雪球地球)和硅质大火成岩省或大规模长英质火山活动的“火山冬天”效应(如晚古生代冰期极盛期).目前,从发生时间一致和关联机制合理性这两个角度考虑,大部分极热和极冷事件的发生都可归因于大规模岩浆活动,但是岩浆活动引发的系列反馈过程以及对极热和极冷事件的触发与维持机制仍缺乏深入理解.就此而论,高精度定年、岩浆活动过程及其气候反馈的数值模拟应该是今后研究的重点.
Climate patterns on Earth fluctuate between greenhouse and icehouse states over multimillion-year timescales,interspersed with hyperthermal and extreme cooling periods that last hundreds of thousands to millions of years.Generally,the Precambrian epoch was characterized by a greenhouse climate,whereas the Phanerozoic eon oscillated between three greenhouse and three icehouse phases.The greenhouse phases were Cambrian-late Ordovician,late Silurian-late Devonian,and late Permian-early Cenozoic;the icehouse phases were the late Ordovician-late Silurian,late Devonian-late Permian,and late Cenozoic periods.During the transitions from Permian to Triassic,the mid-Cretaceous,and the Paleogene to the Neogene,intense warming expanded temperate climates to the poles,marking typical hyperthermal events.During the Neoproterozoic Sturtian and Marinoan glaciations,Earth’s surface was almost entirely sheathed in ice,a phenomenon known as a“snowball Earth”.In contrast,during the peaks of the Hirnantian glaciation,the Late Paleozoic Ice Age,and the Late Cenozoic Ice Age,ice coverage expanded to mid-and low-latitudes,representing typical extreme cooling events.Shifts in the Earth’s climate are largely influenced by changes in atmospheric carbon dioxide(CO_(2))levels,which are determined by the balance between carbon sources and sinks in the ocean-atmosphere system.The primary source of atmospheric CO_(2)is carbon reservoirs beneath the Earth’s surface,which are released into the atmosphere primarily through magmatic processes,including large igneous provinces,continental arcs,and continental rifts.Conversely,these magmatic activities can also cool the Earth’s surface in three ways:(1)By injecting sulfate aerosols,formed from sulfur dioxide(SO_(2)),into the stratosphere,triggering a“volcanic winter”;(2)through the absorption of atmospheric CO_(2)during the chemical weathering of fresh igneous rock;and(3)by enhancing marine primary productivity through the release of phosphorus and iron into the ocean,which facilitate
作者
王永达
杨石岭
沈冰
朱茂炎
陈祚伶
纪伟强
黄晓芳
孙敏敏
张师豪
Yongda Wang;Shiling Yang;Bing Shen;Maoyan Zhu;Zuoling Chen;Weiqiang Ji;Xiaofang Huang;Minmin Sun;Shihao Zhang(CAS Key Laboratory of Cenozoic Geology and Environment,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China;Key Laboratory of Orogenic Belts and Crustal Evolution,Ministry of Education,School of Earth and Space Science,Peking University,Beijing 100871,China;State Key Laboratory of Palaeobiology and Stratigraphy,Nanjing Institute of Geology and Palaeontology,Chinese Academy of Sciences,Nanjing 210008,China;State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China)
出处
《科学通报》
EI
CAS
CSCD
北大核心
2024年第2期215-229,共15页
Chinese Science Bulletin
基金
国家重点研发计划(2022YFF0800800,2022YFF0800100)
国家杰出青年科学基金(41725010)
中国科学院战略性先导科技专项(XDB26000000)
中国科学院地质与地球物理研究所自主部署项目(IGGCAS-201905)资助。
关键词
地球深部过程
温室气候
冰室气候
极热事件
极冷事件
deep Earth process
greenhouse climate
icehouse climate
hyperthermal event
extreme cooling event
