Seafloor Topography Estimation from Gravity: Theory and Applications

142 pages

English

Découvre YouScribe en t'inscrivant gratuitement

Je m'inscris

Seafloor Topography Estimation from Gravity: Theory and Applications , livre ebook

EDP Sciences - Junjun YANG

Découvre YouScribe en t'inscrivant gratuitement

Je m'inscris

Obtenez un accès à la bibliothèque pour le consulter en ligne
En savoir plus

142 pages

English

Obtenez un accès à la bibliothèque pour le consulter en ligne
En savoir plus

A propos
Informations
Extrait

Description

Seafloor topography data are essential for a multitude of Earth science studies. Among various seafloor mapping technologies, gravity inversion is the dominant approach to achieve rapid global coverage at low resolution and to obtain the bathymetry at places covered by ice shelves, icebergs, or ice mélange. The present book systematically discusses the relationship between topography and gravity, establishes methods of inferring seafloor topography from gravity, and gives practical examples showing seafloor topography estimation from airborne gravities measured in polar expedition missions.

Preface..................................................... V

About the Author............................................ VII

CHAPTER 1

Introduction................................................. 1

1.1 Background ............................................1

1.2 Previous Studies......................................... 1

1.2.1 Global Seafloor Topography Estimation

from Altimetry-Derived Gravity ........................ 1

1.2.2 Sub-Ice-Shelf Seafloor Topography Estimation

from Airborne Gravity ............................... 5

1.3 Objective ..............................................5

CHAPTER 2

Relationship Between Topography and Gravity....................... 7

2.1 Relationship in the Frequency Domain........................ 7

2.1.1 Parker’s Theory .................................... 7

2.1.2 Forsberg’s Method ..................................10

2.1.3 Relationships of Gravity Anomaly and Gravity Gradient

to Topography ..................................... 12

2.1.4 Admittance Theory ................................. 16

2.1.5 Advantages and Limitations of Using the Gravity Gradient ... 20

2.2 Relationship in the Spatial Domain........................... 21

2.2.1 The Gravitational Gradients Due to a Right Rectangular

Prism ............................................ 22

2.2.2 The Gravity Anomalies Due to a Right Rectangular Prism... 22

2.3 Errors Associated with Gradient Inversion Techniques............. 23

2.3.1 Truncation and Resolution Errors in the Forward

Computation ...................................... 23

2.3.2 Summary of Other Error Sources .......................27

CHAPTER 3

Estimation Methodology........................................ 29

3.1 Seafloor Topography Estimation Based on Fourier Transform ....... 29

3.2 Analysis of the Nonlinear Terms............................. 30

3.2.1 Validity of the Linear Approximation.................... 30

3.2.2 Introduction to the Coherency......................... 34

3.2.3 Coherency for Finite Power Signals..................... 36

3.2.4 Radially Symmetric Coherency .........................37

3.2.5 Coherency for Signals on the Sphere..................... 38

3.3 Seafloor Topography Estimation Using Simulated Annealing........ 43

3.3.1 Introduction to the Simulated Annealing................. 43

3.3.2 Seafloor Topography Estimation from Gravity Gradients..... 45

3.3.3 Seafloor Topography Estimation from Gravity Anomalies..... 46

3.4 Difference Between Simulated Annealing and Parker’s Method ...... 47

CHAPTER 4

Numerical Experiment......................................... 49

4.1 Study Area Description.................................... 49

4.2 Estimation Using Parker’s Formulation........................ 49

4.2.1 Data Preparation ...................................49

4.2.2 Data Filtering .....................................50

4.2.3 Determination of Topography-to-Gradient Admittance Scale . . 54

4.2.4 Results and Evaluation ..............................57

4.2.5 Results After Including Shorter Wavelengths.............. 59

4.3 Estimation Using Simulated Annealing........................ 61

4.3.1 Analysis of the Forward Computation in the SA........... 61

4.3.2 Data Preparation and SA Configuration................. 63

4.3.3 Results of the Simulated Annealing..................... 65

4.3.4 Low-Pass Filtering the Estimated Seafloor Topography...... 69

4.3.5 Evaluation ........................................ 69

4.3.6 Other Tests of the Simulated Annealing Algorithm......... 71

4.4 Comparison of the Estimation Results......................... 74

4.4.1 Comparison with the SIO Topography Model.............. 74

4.4.2 Comparison Between the Two Methods ..................75

4.5 Conclusions.............................................77

CHAPTER 5

Estimation from Airborne Gravity Gradients........................ 79

5.1 Airborne Gravity Gradients and Multibeam Bathymetry........... 80

5.2 Inversion Parameters...................................... 81

5.3 Analysis and Removal of the Non-Terrain Effects................ 81

5.4 Results, Evaluation, and Discussion.......................... 84

5.5 Conclusions.............................................86

CHAPTER 6

Seafloor Topography Offshore Northeast Greenland................... 89

6.1 Introduction............................................ 89

6.2 Data and Methods .......................................90

6.2.1 Airborne Gravity ...................................90

6.2.2 Bathymetric Data .................................. 92

6.2.3 Inversion Parameters ................................92

6.3 Results and Evaluation.................................... 93

6.3.1 Accuracy Evaluation ................................93

6.3.2 Seafloor Topography ................................94

6.4 Discussion.............................................. 97

6.4.1 Topographic Steering of Ocean Currents................. 97

6.4.2 Errors Associated with Gravity Inversion Techniques........ 99

6.5 Conclusions.............................................100

CHAPTER 7

Seafloor Topography Beneath the Amery Ice Shelf, East Antarctica ....... 103

7.1 Introduction............................................ 103

7.2 Data and Methods .......................................105

7.2.1 Airborne Gravity ...................................105

7.2.2 Laser Altimeter and Ice-Penetrating Radar Data........... 105

7.2.3 Hydrographic Data .................................106

7.2.4 Inversion Parameters ................................106

7.3 Results ................................................107

7.3.1 New Bathymetric Model .............................107

7.3.2 Water Masses Arriving at the AmIS..................... 110

7.4 Discussion.............................................. 112

7.4.1 Topographic Steering of Ocean Currents................. 112

7.5 Conclusions.............................................113

References.................................................. 115

Appendix A: The Spherical Harmonics of the Gravity Anomaly.......... 125

Appendix B: Pseudo-Code for the Adaptive Simulated Annealing......... 127

Sujets

Sciences de la nature

Géologie

Earth Sciences

methods

Sciences et techniques

Geology

Science

Sciences de la Terre

Informations

Publié par	EDP Sciences
Date de parution	26 décembre 2023
Nombre de lectures	0
EAN13	9782759831975
Langue	English
Poids de l'ouvrage	12 Mo

Informations légales : prix de location à la page 1,1600€. Cette information est donnée uniquement à titre indicatif conformément à la législation en vigueur.

Extrait

Junjun YANG

Sealoor Topography Estimation from Gravity: Theory and AppLications

G E O L O G Y

ISBN : 978-2-7598-3196-8

9 782759 831968

Sealoor Topography Estimation from Gravity: Theory and AppLications

Junjun YANG

Junjun YANGis an assistant professor at China Aero Geophysical Survey and Remote Sensing Center for Natural Resources, China Geological Survey. His research interests include seafloor topography estimation, airborne gravity measurement, and geoid determination.

www.edpsciences.org

Junjun YANG

Seafloor Topography Estimation from Gravity: Theory and Applications

Printed in France

EDP Sciences–ISBN(print): 9782759831968–ISBN(ebook): 9782759831975 DOI: 10.1051/9782759831968

All rights relative to translation, adaptation and reproduction by any means whatsoever are reserved, worldwide. In accordance with the terms of paragraphs 2 and 3 of Article 41 of the French Act dated March 11, 1957,“copies or reproductions reserved strictly for private use and not intended for collective use”and, on the other hand, analyses and short quotations for example or illustrative purposes, are allowed. Otherwise,“any representation or reproduction–whether in full or in part–without the consent of the author or of his successors or assigns, is unlawful”(Article 40, paragraph 1). Any representation or reproduction, by any means whatsoever, will therefore be deemed an infringement of copyright punishable under Articles 425 and following of the French Penal Code.

The printed edition is not for sale in Chinese mainland.

Science Press, EDP Sciences, 2023

To my mother and father

Preface

Despite decades of effort, only less than 20% of the world’s seafloor topography has been measured by shipbased echo sounders, limiting our ability to understand iceocean interactions, ocean circulation, critical geophysical processes, etc. Among many techniques used by scientists eager to completely map the world’s oceans by 2030, seafloor topography estimation from gravity is the dominant method to obtain a global view of the oceans and to obtain the seafloor topography at places covered by ice shelves, icebergs, or ice mélange. The present book focuses on this topic. Chapter1provides a brief history. Chapters2and3establish seafloor topography estimation methods, serving as the theoretical basis. Chapters4and5focus on method improvements. Standard techniques rely on an approximate, linear rela tionship between topography and gravity, which is valid only if the local topography is smooth compared with the regional topography, so the estimation accuracy in very rugged areas is low. Chapter4improved current methods by removing the linear approximation and estimating the seafloor topography through a nonlinear inversion method called simulated annealing. Chapter5presented numerical experiments that estimate the seafloor topography from real airborne gravity gra dients which inherently have the potential to achieve higher spatial resolution than airborne gravity for improved inference of seafloor topography. Chapters6and7 consider the application of the improved estimation methods to airborne gravity anomalies measured in polar areas and result in new seafloor topography models in regions covered by ice shelves, places where traditional shipborne multibeam surveys are unavailable. These new seafloor topography models reveal topographic features that are not resolvable in previously published models. With these refined seafloor topography models, scientists could more accurately project the response of the marineterminating glaciers to ocean forcing and their future contribution to global mean sea level rise. This study was partially supported by grants (42006197) from the National Natural Science Foundation of China and grants from the China Postdoctoral Science Foundation.

DOI: 10.1051/9782759831968.c901 Science Press, EDP Sciences, 2023

Preface

The text assumes that the reader is fluent in the calculus. Therefore, under graduate courses in calculus are prerequisites to this text. The book may be used as a reference for glaciologists, geodesists, oceanographers, geophysicists, hydrographic surveyors, and other scientists. Numerous individuals have contributed directly or indirectly to this text, starting with my graduate advisor, Prof. Christopher Jekeli, at The Ohio State University, who introduced the research topic of inferring seafloor topography from gravity and laid the groundwork for my writing of this text. I am indebted, as well, to Prof. Michael Bevis and Prof. Burkhard Schaffrin, who carefully read an early version of the text and offered valuable suggestions. In addition, I am grateful to Prof. Liangcheng Tu, Prof. Zhicai Luo, and the Center for Gravitational Experi ments at Huazhong University of Science and Technology, for the opportunity to spend 3 years working with their faculty and students, but also to do what I wished. Finally, and most of all, my eternal gratitude goes to my wife who endured my obsession with my research and who, throughout the past 5 years, has always supported me in countless ways.

Junjun YANG Beijing, China; October 1, 2022

About

Vita

2010 2015 2017 2018–2021

2021 to present

the

Author

B.E. Land Resource Management, Henan Polytechnic University M.S. Geodetic Science, The Ohio State University Ph.D. Geodetic Science, The Ohio State University Postdoctoral Fellow, Center for Gravitational Experiments, School of Physics, Huazhong University of Science and Technology China Aero Geophysical Survey and Remote Sensing Center for Natural Resources, China Geological Survey

Selected

Publications

Yang J., Guo J., Greenbaum J. S., Cui X., Tu L., Li L.,et al. (2021) Bathymetry beneath the Amery ice shelf, East Antarctica, revealed by airborne gravity, Geophys. Res. Lett.48(24), e2021GL096215.https://doi.org/10.1029/ 2021GL096215. Yang J., Luo Z., Tu L. (2020) Ocean access to ZachariæIsstrøm glacier, northeast Greenland, revealed by OMG airborne gravity,J. Geophys. Res.: Solid Earth125(11), e2020JB020281.https://doi.org/10.1029/2020JB020281. Yang J., Luo Z., Tu L., Li S., Guo J., Fan D. (2020) On the feasibility of seafloor topography estimation from airborne gravity gradients: Performance analysis using real data,Remote Sens.12(24), 4092.https://doi.org/10. 3390/rs12244092. Yang J., Jekeli C., Liu L. (2018) Seafloor topography estimation from gravity gradients using simulated annealing,J. Geophys. Res.: Solid Earth123(8), 6958–6975.https://doi.org/10.1029/2018JB015883.