CSEDI Collaborative Research: Joint seismic-geodynamic constraints on deep Earth structure - Implications for mantle convection and Earth rotation

GSTDTAP

项目编号	1903108
	CSEDI Collaborative Research: Joint seismic-geodynamic constraints on deep Earth structure - Implications for mantle convection and Earth rotation
	Alessandro Forte (Principal Investigator)
主持机构	University of Florida
项目开始年	2019
	2019-06-15
项目结束日期	2022-05-31
资助机构	US-NSF
项目类别	Standard Grant
项目经费	326167(USD)
国家	美国
语种	英语
英文摘要	The Earth's gravity field, which is precisely mapped by orbiting satellites, has 'bumps and valleys' where the field is stronger and weaker. The variation of this field on the very longest wavelengths describes the elliptical shape of the Earth. This elliptical figure is important because it determines the location of the axis of rotation that passes through the Earth's center and also controls changes in inclination of the Earth relative to the sun, owing to the gravitational 'pull' from the moon, the sun, and other planets. The Earth, in effect, behaves as a spinning top that can oscillate and wobble in complex ways. These changes in axial rotation and inclination affect how much solar energy ('insolation') is received at different latitudes on Earth, especially in the polar regions, and therefore has a major impact on climate and how it changes over long time intervals. A major problem in geophysics is to determine how the elliptical form of the Earth is generated by forces deep inside our planet. These forces also drive the horizontal motions of Earth's tectonic plates and the geological 'drift' of continents, as well as vertically pushing and pulling the continents and oceans up and down over time. Despite more than thirty years of progress by geophysicists who map lateral changes in Earth structure deep inside our planet using seismic waves, and similar progress by computational geophysicists who use these maps to model the internal forces needed to explain the motions of tectonic plates and the 'bumps' in Earth's gravity field, there remains a difficulty in properly accounting for the flattening of the elliptical figure of the Earth that is seen by satellites. The principal investigators (PIs) in this proposal will directly tackle this outstanding challenge by using both earthquake and gravity data, and data describing the topography of the Earth and the movements of tectonic plates, to obtain new maps of Earth's internal structure and new determinations of the forces that can explain all these data simultaneously. The outcome of this work will allow the PIs to specifically tackle the current challenge of accounting for Earth's long-term elliptical figure, how it changes with time, and how it influences high-latitude insolation and hence climate over long times. Powerful computer resources will be deployed to carry out this study over the next three years, employing a collaborative team of researchers from the Universities of Texas and Florida. This work will provide opportunities for training new graduate students who will learn state-of-the-art techniques in computer modelling and will develop advanced expertise in the geophysical sciences. The results of this work will be shared with a broad community of scientists, students and the general public with web-based platforms, communications in conferences and workshop, and in outreach activities. Key questions regarding the large-scale structure and dynamics of the mantle remain outstanding, despite three decades of progress in global seismic imaging of Earth's interior. There are longstanding difficulties in satisfactorily accounting for the very longest wavelength anomalies in Earth's gravity field, which are related to Earth's elliptical figure, with significant implications for Earth's time-dependent rotational dynamics. Questions concerning heterogeneity in the transition zone and the nature of "large low shear velocity provinces" (LLSVP) in the lower mantle, also continue to be elusive. These uncertainties regarding anomalous mantle structures directly impact our understanding of the global-scale dynamics of the Earth. To address the questions, the principal investigators propose a multidisciplinary effort to derive a new generation of tomography models that match a wide suite of surface data related to present-day structure and convective flow in the mantle, and can also constrain the time-dependent evolution of the mantle throughout the Cenozoic. To pursue these objectives the PIs will: (i) jointly invert global seismic and convection-related data with greatly improved coverage of 3-D mantle structure, incorporating geodynamic responses to lateral viscosity variations and topography on the discontinuities at the top and bottom of the transition zone; (ii) apply data assimilation methods to the new joint tomography models to reconstruct the Cenozoic evolution of 3-D mantle structure; (iii) calculate corresponding changes of Earth's moment of inertia, to be used in reconstructions of true polar wander and Milankovitch orbital cycles that are implicated in long-term climate variations. It is anticipated these new joint tomography models will provide improved constraints on the impact of transition-zone heterogeneity on convective mass and heat transport across this key region and on the spatial distribution of anomalous density structures within the LLSVP. This work will also contribute to resolving a longstanding difficulty concerning the origin of Earth's anomalous elliptical figure and the implications for the phase and amplitude of Milankovitch climate cycles in the geological past. 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.
文献类型	项目
条目标识符	http://119.78.100.173/C666/handle/2XK7JSWQ/213482
专题	环境与发展全球科技态势
推荐引用方式 GB/T 7714	Alessandro Forte .CSEDI Collaborative Research: Joint seismic-geodynamic constraints on deep Earth structure - Implications for mantle convection and Earth rotation.2019.