Collaborative Research: As above so below: Quantifying the role of simultaneous LLSVPs and continents on Earth's cooling history using numerical simulations of mantle convection

合作研究：如上所述，如下：使用地幔对流数值模拟来量化同时发生的 LLSVP 和大陆对地球冷却历史的作用

• 批准号: 2310325
• 负责人: Catherine Cooper
• 金额: $ 17.34万
• 依托单位: Washington State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-07-01 至 2026-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2310325&HistoricalAwards=false
• 关键词: Collaborative; Research; above; so; below

Earth’s cooling rate affects many processes necessary for a dynamic, living world, from plate tectonics to generation of the planet’s magnetic field. Understanding the establishment, evolution, and continued functioning of such processes requires knowledge of the planet’s thermal history, but much of that history remains unconstrained in part because several controlling mechanisms have yet to be quantified. As such, this award aims to study how Earth’s cooling rate may be altered through variable insulation of the planet’s interior by continents along the surface and large, continent-sized piles of anomalous material (Large Low Shear Velocity Provinces; LLSVPs) covering portions of the outer core. Previous studies separately examined the insulating effects of continents and LLSVPs, but none focused on the potentially counteracting effects of simultaneous insulating bodies: continents are predicted to increase the mantle’s internal temperature while LLSVPs decrease it. This study will quantify the resulting dynamic and thermal effects of such bodies and the implications for the Earth’s cooling history, plate tectonics, and magnetic field. Furthermore, both continents and LLSVPs act as chemical reservoirs that isolate critical elements from participating in global cycling for potentially long portions of Earth’s history. However, the formation and evolution of LLSVPs is still actively debated. This study will identify their likely thermal and chemical fingerprints as an additional means of testing their potential formation timing and duration. In addition to scientific advances, this project will expand educational opportunities centered on the deep Earth through an interdisciplinary game development program that will produce a new, widely distributed, educationally focused video game designed to combat several geoscience misconceptions while supporting a diverse, interdisciplinary group of ten undergraduate student developers. Finally, this award supports two graduate students and a post-doctoral scholar at two rural, land-grant universities, Washington State University and University of Idaho. This award supports a novel study that will systematically evaluate how simultaneous surface and basal insulating bodies in Earth’s mantle (continents + LLSVPs) jointly alter the thermal evolution and internal mantle dynamics of the Earth. Two-dimensional spherical numerical simulations will be used to quantify the impacts of simulated LLSVP and continental materials in models of increasing rheological, thermal, and temporal complexity to address three research objectives: (1) isolate the fundamental processes governing interactions of surface (continent) and basal (LLSVP) insulators, (2) quantify the influence of complex rheology and internal heating on the basal and surface insulator convective system, and (3) examine impacts of time-evolving basal and surface insulators through Earth’s history. Numerical simulations of the Earth’s mantle subject to surface (continent) and basal (LLSVP) insulators will be conducted using the highly parallel finite-element code ASPECT (Advanced Solver for Problems in Earth’s ConvecTion). Simulations will be solved in parallel across ~32-256 computational cores on University of Idaho’s Falcon supercomputer (33k cores, 1.17 Petaflop) or Washington State University’s Kamiak high performance computer cluster. For each of the ~200 planned simulations, the conservation equations will be discretized across a dynamically refined grid of ~2 million finite elements with enhanced element resolution near strong thermal and compositional gradients, allowing an accurate quantification of heat transfer through the model system.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.

地球的冷却速度影响着动态的生命世界所必需的许多过程，从板块构造到地球磁场的产生，了解这些过程的建立、演化和持续运作需要了解地球的热历史，但其中大部分历史。仍然不受限制，部分原因是一些控制机制尚未量化。因此，该奖项旨在研究如何通过沿地表的大陆和大型大陆堆对地球内部的可变隔热来改变地球的冷却速率。覆盖外核部分的异常材料（大低剪切速度省；LLSVP）先前的研究分别检查了大陆和 LLSVP 的绝缘效应，但没有关注同时绝缘体的潜在抵消效应：预计大陆会增加地幔的内部温度，而 LLSVP 会降低地幔的内部温度。这项研究将量化这些物体所产生的动力和热效应，以及对地球冷却历史、板块构造的影响。此外，大陆和 LLSVP 都充当化学储存库，在地球历史的很长一段时间内将关键元素与参与全球循环隔离开来。然而，LLSVP 的形成和演化仍然存在激烈的争论，这项研究将确定它们的可能性。热指纹和化学指纹作为测试其潜在形成时间和持续时间的额外手段除了科学进步之外，该项目还将通过跨学科游戏开发计划扩大以地球深处为中心的教育机会，该计划将产生一种新的、广泛分布的、具有教育意义的游戏。聚焦视频该游戏旨在消除一些地球科学误解，同时支持由十名本科生开发者组成的多元化跨学科小组。最后，该奖项支持两所农村赠地大学（华盛顿州立大学和爱达荷大学）的两名研究生和一名博士后学者。该奖项支持一项新颖的研究，该研究将最终评估地幔中的同步表面和基底绝缘体（大陆+ LLSVP）如何共同改变地球的热演化和内部地幔动力学的二维球形数值模拟。量化模拟 LLSVP 和大陆材料在流变、热和时间复杂性不断增加的模型中的影响，以实现三个研究目标：(1) 分离控制表面（大陆）和基底 (LLSVP) 绝缘体相互作用的基本过程，(2 ) ) 量化复杂流变学和内部加热对基底和表面绝缘体对流系统的影响，以及 (3) 通过地球历史的数值模拟检查随时间演化的基底和表面绝缘体的影响。受表面（大陆）和基底（LLSVP）绝缘体影响的地球地幔将使用高度并行的有限元代码 ASPECT（地球对流问题的高级求解器）进行模拟，将在约 32-256 个计算核心上并行求解。爱达荷大学的 Falcon 超级计算机（33k 核，1.17 Petaflop）或华盛顿州立大学的 Kamiak 高性能计算机对于约 200 个计划模拟中的每一个，守恒方程将在约 200 万个有限元的动态细化网格中离散化，并在强热和成分梯度附近增强单元分辨率，从而可以准确量化通过模型系统的传热。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。