Collaborative Research: Using a weather model and geologic data to test tectonic mechanisms in an intercontinental setting: The Altai Mountains of Central Asia

山脉的高度和形状对我们周围的世界有着深远的影响。山脉拥有各种各样的生态栖息地，提供生命所需的大量水和营养，提供社会所需的关键矿物质，并影响气候和天气模式。山脉的大小和形状反映了下面的固体地球过程，这些过程负责地壳如何变形、地震和相关的自然灾害。尽管它们很重要，但恢复山脉的历史仍然异常困难，包括它们的高度和形状的变化如何与大气相互作用，从而驱动气候和天气。该项目旨在将大气和地球科学的新进展应用到中亚的一项自然实验中，在那里，过去5000万年来阿尔泰山脉的高度和形状被认为促成了大气环流和气候的重大变化。阿尔泰山脉是亚洲的主要山脉之一，它极大地改变了区域气候和生态系统，并产生了一些有史以来最大的大陆内地震。本研究将使用一种新的天气模型来预测大气环流和气候的变化，以响应阿尔泰的大小、高度和生长历史。这些模型预测将根据从阿尔泰地区的沉积物中收集的现场和实验室数据进行测量。利用保存在沉积物中的岩石磁性数据，以及凿入山脉的河道的陡峭程度，主要研究人员将能够建立一个与阿尔泰山脉的开始和生长历史相一致的年龄模型。这种跨学科的方法将由美国多所大学组成的多元化团队进行，其中包括职业生涯早期的教授、研究生和本科生，以及天文学和地球物理研究所的蒙古同事。该项目将培养3名跨学科地球科学博士研究生、3名早期科学家和1名本科生，并建立国际交流机会。这项研究的结果将提高对固体地球和大气过程之间耦合的理解，并有助于解决社会挑战，例如建立对气候变化和地震相关自然灾害的抵抗力。山地地形反映了构造、动力和地表过程之间的复杂耦合，影响着气候演化、海洋和陆地生物地球化学，甚至生物多样性的发展。不幸的是，经常用于重建过去地形的气候代用物本身依赖于各种其他因素。因此，限制造成山脉高度的构造和/或动力过程仍然非常困难。该项目将利用大气科学的新进展来理解地形的增长，而不仅仅是地形降雨的简单上坡模式。该项目的重点是中亚北部的阿尔泰山脉，这是一个鲜为人知的中亚造山带的新生代复兴，上升超过4公里，投下大量的雨影，并与一些有记录以来最大的大陆内地震有关。人们将阿尔泰隆起归因于印度和欧亚大陆碰撞产生的远场应力传播，或地幔柱、俯冲板块或岩石圈分层的动力支撑。每一种隆升机制都预测了一种独特的岩石隆升和区域气候变化的时空格局，这是基于这些隆升机制如何以及何时改变了阿尔泰的高度、形状和方向。现有数据相互矛盾；沉积、地貌和热年代学数据表明，构造隆升始于古近纪，而来自上风和背风盆地的古气候数据表明，直到中新世晚期才出现明显的气候变化，当时蒙古西部出现了大量干旱化。该项目的重点是利用河流地形的反演和背风盆地古气候的稳定和块状同位素新记录收集新的空间分辨岩石隆升数据。蒙古西部地区的岩石隆起和气候变化的年龄模型将受到基于磁地层学和旋回地层学的邻近同变形盆地沉积物年龄模型的限制。天气研究和预报模型将用于预测不同的阿尔泰地形历史对气候的影响。综合起来，这些数据集可以检验那些试图解释新生代阿尔泰隆起的理论。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The height and shape of mountain ranges exert a profound influence on the world around us. Mountains host a variety of ecological habitats, provide much of the water and nutrients necessary for life, the critical minerals needed for society, and influence climate and weather patterns. The size and shape of mountains reflect the underlying solid Earth processes responsible for how the crust deforms, for earthquakes, and for related natural hazards. Despite their importance, it remains exceptionally difficult to recover the history of mountains including how changes in their height and shape interact with the atmosphere to drive climate and weather. This project seeks to apply new advances in the atmospheric and geosciences to a natural experiment in central Asia where the height and shape of the Altai Mountains over the past 50 million years are thought to have precipitated a major change in atmospheric circulation and in climate. The Altai are one of the major ranges in Asia that substantially modify regional climate and ecosystems and spawn some of the largest intracontinental earthquakes ever recorded. This research will use a novel weather model to predict changes in atmospheric circulation and climate in response to the size, height, and growth history of the Altai. These model predictions will be measured against field and laboratory data gleaned from the sediments shed from the Altai. Using rock magnetic data preserved in the sediments, and the steepness of river channels carved into the mountains, the principal investigators will be able to construct an age model consistent with the onset and growth history of the Altai range. This interdisciplinary approach will be pursued by a multi-university, diverse team in the U.S. that includes early-career professors, graduate students and undergraduates in collaboration with Mongolian colleagues at the Institute for Astronomy and Geophysics. The project will train three PhD students, three early-career scientists, and one undergraduate in inter-disciplinary geosciences and build international exchange opportunities. The results of this research will improve understanding of the coupling among solid Earth and atmospheric processes and contribute to addressing societal challenges, such as building resistance to climate change and to earthquake-related natural hazards. Mountain topography reflects complex couplings among tectonic, dynamic, and surficial processes and influences climatic evolution, marine and terrestrial biogeochemistry, and even the development of biodiversity. Unfortunately, the climatic proxies which are so often used to reconstruct past topography are themselves dependent upon a variety of other factors. Consequently, constraining the tectonic and/or dynamic processes that are responsible for the height of mountains remains exceptionally difficult. This project will leverage novel advances in the atmospheric sciences to understand topographic growth beyond the simple upslope model of orographic rainout. The project focuses on the Altai Mountains of northern Central Asia, a poorly understood Cenozoic rejuvenation of the Central Asia Orogenic Belt that rises more than 4 kilometers, casts a substantial rain shadow, and is associated with some of the largest intracontinental earthquakes on record. Altai uplift has been variously attributed to far-field stress propagation from the collision of India and Eurasia or to dynamic support from a mantle plume, a subducting slab, or lithospheric delamination. Each of these uplift mechanisms predict a unique spatial and temporal pattern of rock uplift and of regional climate change, based upon how and when these uplift mechanisms modified the height, shape, and orientation of the Altai. Existing data are contradictory; sedimentary, geomorphic, and thermochronologic data indicate that tectonic uplift began in the Paleogene, whereas paleoclimate data from both windward and leeward basins suggest no clear climatic change until the late Miocene, when there appears to be substantial aridification in western Mongolia. The project focuses on collecting new spatially-resolved rock uplift data using inversions of fluvial topography and new stable and clumped isotope records of paleoclimate from leeside basins. The age model for both rock uplift and of climatic change across western Mongolia will be constrained by magneto- and cyclostratigraphic-based age models of adjacent, syn-deformational basin sediments. The Weather Research and Forecasting model will be used to predict the climate impact of distinct Altai topographic histories. Combined, these data sets permit tests of the theories that seek to explain Cenozoic Altai uplift.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.