IODP 355 Moratorium Proposal: Cenozoic evolution of the Asian Monsoon: tectonic-climate interactions

IODP 355 暂停提案：亚洲季风的新生代演化：构造-气候相互作用

• 批准号: NE/N005414/1
• 负责人: James Bendle
• 金额: $ 4.08万
• 依托单位: University of Birmingham
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2015
• 资助国家: 英国
• 起止时间: 2015 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FN005414%2F1
• 关键词: IODP; 355; Moratorium; Proposal; Cenozoic

The Asian Monsoon is one of the most dramatic climatic phenomena on Earth today. Almost two thirds of humanity live within regions influenced by the monsoon and the strength and variability of the annual rains are crucial to the prosperity of the region. Understanding what controls what controls the Asian monsoon and how it has changed in the past is important not only to scientists but also the general population. The intensity of the modern monsoon likely reflects the fact that the HTP is the largest mountain chain seen on Earth for more than 500 million years. This huge tectonic forcing has correspondingly made a particularly large impact on the planet's atmospheric systems. However, this proposed relationship is the basis of a long-running debate. To confirm the relationship between the HTP and the strength of the Monsoon scientists need continuous geological sequences which have recorded the relatively slow growth of the plateau and monsoon strength dating back to the collision of the Indian and Asian plates around 50 millions years ago. Such records exist in the oceans around Asia and are now being drilled by the International Ocean Discovery Programme (IODP). The onset and intensification of the monsoon allied with the tectonic evolution of the Himalayan-Tibetan Plateau (HTP) comprises perhaps the most significant processes affecting global climatic conditions during the Cenozoic, but the lack of explicit evidence for a causative relationships remains a major problem in Earth science. Demonstrating any linkage between climate and tectonics is impossible without a better understanding of when and how the monsoon developed. With this information, such developments can then be correlated, or not, to either tectonic uplift and extension, or other possible Cenozoic climate drivers. As an example, chemical weathering of the HTP and associated initiation of the monsoon has been invoked as a mechanism that draws down atmospheric CO2 , suggesting this weathering to be an integral part of the Cenozoic climate system. Studies have highlighted a significant climate change at ~8 Ma, and at ~23 Ma it has been argued these represent monsoon intensification. On the other hand, alternative models propose the retreat of shallow seas from Central Asia (Paratethys) is a crucial boundary condition influence, while other workers have argued the strengthening of the monsoon is linked to either; opening of the South China Sea, formation of the Western Pacific Warm Pool or global cooling. Resolving such paleoclimatic questions is critical to answer questions over the future response of the Monsoon to anthropogenic warming. Specifically it is necessary to deconvolve the signals of: a) Monsoon response to baseline changes in relief and extent, driven by uplift and solid Earth process from: b) Monsoon response to key periods of elevated CO2 and global warmth during the late Cenozoic, e.g. the Mid-Pliocene Warm Period (MPWP) at ca. 3.5Myr; the Middle Miocene Climatic Optimum (MMCO) at ca. 18-15 Myr and Early Eocene at ca. 48-56 Myr.

亚洲季风是当今地球上最引人注目的气候现象之一。近三分之二的人类生活在受季风影响的地区，年降雨量的强度和变化对该地区的繁荣至关重要。了解是什么控制了什么控制了亚洲季风，以及它在过去是如何变化的，这不仅对科学家很重要，对普通民众也很重要。现代季风的强度可能反映了这样一个事实，即HTP是地球上5亿多年来最大的山脉。这种巨大的构造力相应地对地球的大气系统产生了特别大的影响。然而，这种拟议中的关系是一场长期争论的基础。为了确认HTP和季风强度之间的关系，科学家们需要连续的地质序列，这些序列记录了高原相对缓慢的增长和季风强度，可以追溯到大约5000万年前印度板块和亚洲板块的碰撞。这样的记录存在于亚洲周围的海洋中，目前正在由国际海洋发现计划（IODP）进行钻探。如果不更好地了解季风的形成时间和方式，就不可能证明气候和构造之间的任何联系。有了这些信息，这样的发展就可以与构造隆起和伸展或其他可能的新生代气候驱动因素相关联或不相关。例如，HTP的化学风化和季风的相关启动被认为是一种吸收大气二氧化碳的机制，表明这种风化是新生代气候系统的一个组成部分。研究强调了~8 Ma和~23 Ma的显著气候变化，有人认为这些变化代表了季风的增强。另一方面，其他模式提出，中亚（Paratethys）的浅海退缩是一个关键的边界条件影响，而其他工作者则认为季风的加强与两者都有关；南海的开放，西太平洋暖池的形成或全球变冷。解决这些古气候问题对于回答未来季风对人为变暖的反应至关重要。具体而言，有必要对以下信号进行反褶积：a)由隆升和固体地球过程驱动的基线起伏和范围变化的季风响应；b)晚新生代CO2升高和全球变暖的关键时期的季风响应，例如约3.5Myr的中上新世暖期（MPWP）；中中新世气候最适期（MMCO）约为18-15 Myr，早始新世约为48-56 Myr。