CAREER: Deformation by surface loading from ocean tides and continental water on a 3-D Earth

海洋、大气层和陆地上的流体循环，由于表面压力的变化，导致地球的形状在时间尺度上变形。变形的模式取决于流体的重量和分布以及地球内部的结构特性。因此，对地球表面反复循环的加载和卸载引起的地球变形的观测和模型可以揭示重要的地球系统过程，包括地幔动力学，水循环和气候变化。对于众所周知的负载，如海洋潮汐，调查表面负载可以放置关键的限制，允许模型的密度结构和力学行为的地壳和地幔，这可以推进地幔对流过程的理解，驱动板块构造和表面灾害。此外，跟踪负荷引起的地球变形可以量化各大洲淡水储存的变化，这有助于干旱监测和水资源管理。该项目旨在推进观测和计算方法，以分析地球在地表水和空气的重量下如何变形。最近的研究表明，包括全球定位系统在内的最新卫星定位系统的观测精度现在可能超过目前通常假定地球结构为球对称的地球变形模型的预测能力。因此，该项目的一个主要目标将是利用计算技术和地球物理软件的新进展来调查地球结构的三维（3-D）变化的影响（即，地形、由于自转引起的极地变平和内部结构的横向变化）对载荷引起的地球变形的影响。通过使地表负荷的预测模型更加准确，并通过以更广泛的科学界可以更容易使用的方式包装计算工具，该项目旨在完善现有的地球结构模型，改善对各大洲淡水储量的估计，并促进推动地球物理学创新的合作努力。随着计算方法变得越来越复杂，支持和提高早期职业科学家计算素养的资源对于劳动力发展和持续创新将变得越来越重要。该项目将产生一系列的计算短期课程，可以交付给学生，博士后学者和更广泛的科学界在灵活的格式。该项目还将促进研究生-本科生指导和专业发展计划，并产生开放的教育资源。该项目的一个主要目标是量化固体地球结构的三维变化，包括地形和材料特性的内部对比，对海洋潮汐负荷和大陆水负荷引起的表面位移的影响。该项目将分析全球导航卫星系统（GNSS）的数据产品，并开发模型来预测三维地球对表面加载和卸载周期的反应。研究产品将包括：（1）灵敏度和分辨率分析，对使用全球导航卫星系统限制三维地球结构的能力进行量化;（2）对三维地球结构对估算海洋潮汐负荷和大陆水储存量的影响进行量化评估;（3）根据全球导航卫星系统数据对负荷潮汐进行经验性估算;（4）开放源码软件工具，便利潮汐分析和地球结构大地测量数据反演;以及（5）通过GNSS观测负荷潮汐约束的地球结构的精细模型。该奖项反映了NSF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。

Circulations of fluids in the oceans, in the atmosphere, and over land cause the shape of the Earth to deform on time scales due to changes in surface pressure. The pattern of deformation depends on the weight and distribution of the fluids as well as on the structural properties of Earth’s interior. Thus, observations and models of Earth deformation caused by repeated cycles of surface loading and unloading can shed light on important Earth-system processes, including mantle dynamics, the water cycle, and changes in climate. For well-known loads, such as the ocean tides, investigations of surface loading can place key constraints on allowable models for the density structure and mechanical behavior of Earth’s crust and mantle, which can advance understanding of mantle convective processes that drive plate tectonics and surface hazards. Furthermore, tracking load-induced Earth deformation allows for the quantification of changes in freshwater storage over the continents, which can aid in drought monitoring and water-resource management. This project aims to advance both observational and computational methods for analyzing how the Earth deforms under the weight of water and air at the surface. Recent studies suggest that the observational precision of state-of-the-art satellite positioning systems, including the Global Positioning System (GPS), may now exceed the predictive capabilities of current Earth-deformation models that commonly assume spherically symmetric Earth structure. Thus, a major objective of this project will be to leverage new advances in computational technologies and geophysical software to investigate the impacts of three-dimensional (3-D) variations in Earth structure (i.e., topography, polar flattening due to rotation, and lateral variations in internal structure) on load-induced Earth deformation. By making predictive models of surface loading more accurate, and by packaging computational tools in a way that the broader scientific community can use with greater ease, this project aims to refine existing models of Earth structure, improve estimates of freshwater storage over the continents, and promote collaborative efforts that drive innovation in geophysics. With computational methods becoming more sophisticated, resources that support and enhance the computational literacy of early-career scientists will become ever more critical to workforce development and sustained innovation. This project will produce a series of computational short courses that can be delivered to students, postdoctoral scholars, and the broader scientific community in flexible formats. This project will also facilitate graduate-undergraduate mentoring and professional-development programs as well as generate open educational resources. A primary objective of this project is to quantify the influence of 3-D variations in solid-Earth structure, including topography and internal contrasts in material properties, on surface displacements caused by ocean tidal loading and continental water loading. This project will analyze data products from Global Navigation Satellite Systems (GNSS) and develop models to predict the response of a 3-D Earth to cycles of surface loading and unloading. Research products will include: (1) sensitivity and resolution analyses that quantify the ability to constrain 3-D Earth structure using GNSS; (2) quantitative assessments of the impacts of 3-D Earth structure on estimates of ocean tidal loading and continental water storage; (3) empirical estimates of load tides from GNSS data; (4) open-source software tools that facilitate tidal analysis and the inversion of geodetic data for Earth structure; and (5) refined models for Earth structure constrained by GNSS observations of load tides.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.