| 摘要: |
| Raymo和Ruddiman提出了“青藏高原隆升—风化剥蚀—CO2浓度下降—全球气候变冷”链条模型来解释晚新生代气候变化。但目前仍存在一些悬而未决的问题，如青藏高原是否具有控制全球气候的能力？如何解释类似于现在的全球CO2浓度形成于约24 Ma？结合已有的地质证据，尝试对上述问题进行回答，首次提出用“触发器-连接器”模型来解释新生代全球CO2的浓度变化，尤其是类似于现在的全球CO2浓度形成于约24 Ma。“触发器”指全球高大的高原和山脉，尤其是青藏高原；“连接器”指亚洲季风、西风和全球大江大河。“触发器-连接器”模型的显著特点在于：从地球系统科学思维角度，将高原隆升、季风、西风和全球大江大河对全球大气CO2浓度变化的影响整合在一起，而且强调影响大气CO2浓度的范围在约24 Ma之前仅局限于局部区域，但是约24 Ma之后，在“连接器（亚洲季风、西风和全球大江大河）”的串联作用下将影响大气CO2浓度的范围由约24 Ma之前的青藏高原扩展到约24 Ma之后的亚洲以及周边的海洋区域，对全球CO2浓度变化控制力显著增强，这可能是类似于现在CO2浓度水平形成于约24 Ma的主要原因。 |
| 关键词: 青藏高原 CO2浓度 风化 触发器-连接器 |
| DOI：10.7515/JEE223005 |
| CSTR：32259.14.JEE223005 |
| 分类号: |
| 基金项目:国家自然科学基金项目（42102023）；第二次青藏高原科学考察项目（2019QZKK0707）；云南省地球系统科学重点实验室（ESS2022001）；中国科学院战略性先导科技专项（XDB40010100） |
| 英文基金项目:National Natural Science Foundation of China (42102023); The Second Tibetan Plateau Scientific Expedition and Research (2019QZKK0707); Open Fund of Yunnan Key Laboratory of Earth System Science (ESS2022001); Strategic Priority Research Program of the Chinese Academy of Sciences (XDB40010100) |
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| Global CO2 concentration change induced by “trigger-connectors” model, especially since about 24 Ma? A preliminary hypothesis |
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LI Leyi1, 2, 3, CHANG Hong1, 4*
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1. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710061, China
2. Xi’an Institute for Innovative Earth Environment Research, Xi’an 710061, China
3. Yunnan Key Laboratory of Earth System Science, Yunnan University, Kunming 650500, China
4. CAS Center for Excellence in Quaternary Science and Global Change, Xi’an 710061, China
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| Abstract: |
| Background, aim, and scope The tectonic uplift of the Cenozoic Tibetan Plateau has produced a chain effect, which is an excellent location for Earth system science research, and its uplift process, mechanism and environmental effects are the hot spot and frontier of the current research. The “Tibetan Plateau uplift—weathering—CO2 concentration—global climate change” model was put forward by Raymo and Ruddiman to interpret the Late Cenozoic climate change. However, there are still some questions suspended, such as does the weathering of the Tibetan Plateau have the ability to control the global climate? How to explain the modern-like global CO2 concentration starting at about 24 Ma? Here, a short space was taken to present a brainstorm about the above questions on account of existing geological pieces of evidence. Materials and methods In this paper, we integrate the formation and evolution of the Yangtze River and Pearl River, the origin and development of the Asian inland aridification-monsoon system, the Cenozoic tectonic uplift process of the Tibetan Plateau, and the westerly winds to discuss and analyze the relationship between the Cenozoic CO2 concentration changes and the uplift of the Tibetan Plateau and why the CO2 concentration similar to the present was formed at about 24 Ma. Results Similar correspondence of the surface uplift history of Xizang, other global mountains, and the declining CO2 concentration could support the theory Tibetan Plateau weathering influences CO2 concentration. Starting from 24 Ma, the most important character was the uplift and erosion of Xizang and Himalaya, collaborating with Ocean Iron Fertilization (OIF) together as an entity to control the atmospheric CO2 concentration because the great Asian rivers, Asian monsoons, and westerlies connected Xizang and surrounded seas together through materials transportation. Discussion Paleogeographic reconstructions from 40 Ma to 20 Ma illustrate that the main topographic change occurred in the Andes, Cordillera orogenic belt, and Xizang. We comprise a comprehensive set of evidence from independent data, which correspond temporally with the tipping point (about 24 Ma) of the atmospheric CO2 and we noticed that modern-like Asia monsoon, inland aridity, Asian great rivers, and climate zone formed at about 24 Ma and also there are tectonic activities for the Andes and Rockies. We raised the possibility that the modern-like atmospheric CO2 concentration at about 24 Ma was caused by the above geological factors. Here the rivers, monsoon, and westerlies are termed as “connectors”. In addition, these Asian rivers originated from Xizang, the monsoon, and inner Asian aridification are strongly a function of the uplift and growth of Xizang, thus, Xizang here is named as “trigger”. The distinct character of “trigger-connectors” model is that this not only takes the monsoon, westerlies, and the global great rivers into consideration but also expands the range which influences atmospheric CO2 concentration, from local points to a vast area since about 24 Ma, such as from Tibetan Plateau to Asia, including surrounded seas, after about 24 Ma. However, because the opening of the Late Oligocene—Early Miocene Antarctic periphery straits is highly coincident with the onset of modern-like global atmospheric CO2 concentration, we are forced to consider that they also had a significant impact on the reduction of atmospheric CO2 concentrations at this time. Conclusions “Trigger-connectors” was put forward to explain the Cenozoic CO2 variation, especially modern-like global CO2 concentration since about 24 Ma. Recommendations and perspectives Here we use the “trigger-connectors” model to explain the formation of modern-like CO2 concentrations starting at about 24 Ma, but there are still some problems. The most important premise for the “trigger-connectors” model is the constructed Cenozoic CO2 concentration record is reliable, which is the foundation of our hypothesis. In the future, potential improvements should focus on topographic reconstructions of Xizang and the global mountains. Here we have concentrated on Xizang in the considered timeslices but still, pay less attention to other global orogenic belts. Collaborations with geologist experts in those regions could provide valuable feedback to evaluate their potential role of them in CO2 evolution. What is more, considerable progress may be achieved with the addition and consideration of more and new geological data. |
| Key words: Tibetan Plateau CO2 concentration weathering trigger-connectors |
