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

University Of Montana, Missoula MT

Investigators

Abstract

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.