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1 Introduction DEM GENERATION AND OCEAN TIDE MODELING OVER SULZBERGER ICE SHELF, WEST ANTARCTICA, USING SYNTHETIC APERTURE RADAR INTERFEROMETRY DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Sang-Ho Baek, B.E., M.S. ***** The Ohio State University 2006 Dissertation Committee: Approved by Professor C. K. Shum, Adviser Professor Burkhard Schaffrin Professor Doug Alsdorf Adviser Geodetic Science and Surveying Graduate Program Dr. Zhong Lu ABSTRACT The use of Synthetic Aperture Radar Interferometry (InSAR) is an effective tool for studying the ice mass balance of polar regions and its contribution to global sea level change. An accurate, high-resolution digital elevation model (DEM) referenced within a well-defined terrestrial reference frame (TRF) is an inherent requirement to facilitate the use of InSAR to conduct these studies in remote polar regions where ground control points (GCPs) are unavailable. In this study, a digital elevation model by the Sulzberger Bay, West Antarctica is determined by using twelve European Remote Sensing (ERS) -1 and ERS-2 tandem satellite mission synthetic aperture radar scenes and nineteen Ice, Cloud, and land Elevation Satellite (ICESat) laser altimetry profiles. Differential interferograms from the ERS-1/ERS-2 tandem mission SAR scenes acquired in the austral fall of 1996 are used together with four selected ICESat laser altimetry profiles in the austral fall of 2004 which provides GCPs, resulting in an improved geocentric 60-m resolution DEM over the grounded ice region. The InSAR DEM is then extended to ii include two ice tongues using ICESat profiles via Kriging. Fourteen additional ICESat profiles acquired in 2003-2004 are used to assess the accuracy of the DEM. After accounting for radar penetration depth and predicted surface changes, including effects due to ice mass balance, solid Earth tides, and glacial isostatic adjustment, in part to account for the eight-year data acquisition discrepancy, the resulting difference between the DEM and ICESat profiles is -0.55 ± 5.46 m. After removing the discrepancy between the DEM and ICESat profiles for a final combined DEM using a bicubic spline, the overall difference is 0.05 ± 1.35 m indicating excellent consistency. Accurate knowledge of the Antarctic ice sheet mass balance plays an important role on the global sea level change. Ocean tides (barotropic and baroclinic) and tidal currents cause basal melting and migration of grounding lines, which are all critical to the accurate determination of ice sheet or ice stream mass balance. Ocean tides in the Antarctic Ocean, especially underneath ice shelves or sea ice, are poorly known primarily due to lack of observations with adequate resolution and knowledge of the bathymetry and ice shelf bottom roughness. InSAR has been used to measure the ice sheet mass balance, ice topography, ice stream velocity, and the location of the grounding lines. To iii properly use InSAR measurements for ice mass balance and because of their high spatial resolution (tens of meters), knowledge of ocean tides underneath the ice shelves needs to be accurately known and with commensurate resolution. Here two-pass differential InSAR (DInSAR) technique is applied for tidal signal modeling underneath the Sulzberger ice shelf, West Antarctica. The fine resolution (60-m) Digital Elevation Model (DEM) over grounded ice and ice shelf, obtained by combining ERS-1/2 tandem InSAR and ICESat laser altimetry, has been used to correct the topography phase from interferograms, resulting in a more accurate time series of vertical deformation measurements. In this study, it is demonstrated for the first time, that observable tidal constituents can be estimated underneath an ice shelf using an InSAR time series. In particular, it is shown that the time series of observed tidal differences from InSAR agrees well with a number of global/regional ocean tide models such as NAO.99b, TPXO.6.2, GOT00.2, CATS02.01, and FES2004, with the regional model, CATS02.01, having the best agreement. The technique developed here can be applied to other ice shelf regions where tide modeling is poor in accuracy and resolution. iv Dedicated to my family v ACKNOWLEDGMENTS First of all, I want to express my deepest gratitude to Dr. C. K. Shum for his encouragement and support during my Ph. D. study. His broad knowledge and priceless direction for this study enabled me to reach the goal of the research work. He showed a good example of accepting people with open mind and his positive thinking made me to focus on my study. I would like to express my thanks to Dr. Burkhard Schaffrin for his careful review and advice for this dissertation. The same gratitude should go to Dr. Doug Alsdorf for his comments on my dissertation. His lectures helped me to understand and concrete my knowledge on InSAR principles, processing and applications. My sincere thanks also go to Dr. Zhong Lu for the fruitful discussions and practical help on InSAR processing. I appreciate the valuable discussions and help on basic InSAR processing from Oh-Ig Kwoun at EROS data center and Michael Baessler at TU Dresden, Germany. I thank my colleagues in Laboratory for Space Geodesy and Remote Sensing for their friendship and support during my study. vi This research is supported by a grant from the National Science Foundation’s Office of Polar Program (OPP-0088029). vii VITA Feb 2, 1970 ·······································Born – Naju, Korea 1988. 3 - 1992. 3 ·······························B.E. Civil Engineering, Korea Military Academy, Seoul, Korea 1994. 3 – 1996. 2······························M.S. Civil Engineering, Yonsei University, Seoul, Korea 1996. 8 – 2001. 8·······························Instructor, Department of Civil Engineering, Korea Military Academy, Seoul, Korea 2001. 8 – present ·······························Graduate Research Associate, The Ohio State University viii PUBLICATIONS 1. Shum, C., Y. Yi, S. Baek, and Y. Wang, Ross Sea Ocean tide modeling Using SAR interferometry and radar altimetry, Jekeli, C. and C. Shum (Eds.) Proc. Weikko A. Heiskanen Symposium In Geodesy: Celebrating 50 years in Geodetic Science at the Ohio State University, Ohio State University, Columbus, Ohio, October 1-5, 2002. 2. Shum, C., Y. Yi, Y. Wang, S. Baek, O. Anderson, and Z. Lu, Ross sea tide modeling using INSAR and radar altimetry, EOS Trans. AGU, Fall Meet. Suppl., Abstract, San Francisco, December 6-10, 2002. 3. Yi, Y., C. Shum, Y. Wang, S. Baek, and O. Anderson, Ocean tide modeling the Southern Ocean, Proc. IUGG2003, Sapporo, Japan, June 30-July 11, 2003. 4. Shum, C., S. Baek, A. Braun, L. Potts, M. Baessler, R. Dietrich and Z. Lu, Study of ice stream velocity, tidal dynamics and crustal deformation using ALOS PALSAR interferometry, Proc. 2nd ALOS PI Workshop & The JERS-1 PI Final Evaluation ix Meeting, Awaji Yumebutai International Conference Center, Awaji Is., Japan, January 19-23, 2004. 5. Baek, S., O. Kwoun, M. Baessler, Z. Lu, C.K. Shum and R. Dietrich, DEM Generation and Tidal Deformation Detection for Sulzberger Ice Shelf, West Antarctica Using SAR Interferometry, Proc. Institute Navigation Annual Meeting, pp. 424-430, Dayton, OH, 2004. 6. Shum, C., S. Baek, H. Lee, Z. Lu, O.-I. Kwoun and A. Braun, Tidal dynamics, ice stream velocity and DEM in the Sulzberger ice self, West Antarctica using SAR interferometry, Proc. International Symposium on Remote Sensing (ISRS) 2004, Jeju Is., Korea, October 27-29, 2004. 7. Baek, S., O. Kwoun, Z. Lu and C. Shum, DEM generation in West Antarctic using SAR interferometry and ICESat laser altimeter data, International Symposium on Remote Sensing, Jeju Is., Korea, October 27-29, 2004. 8. Shum, C., C. Jekeli, M. Bevis, D. Alsdorf, F. Schwartz, B. Schaffrin, S.-C. Han, S. Baek, K. Cheng, S. Ge, Y. Yi, M.-L. Lai, M. Schmidt, and Y. Felus, Advanced space/airborne geodetic sensors and geomathematics for environmental and climate x change research defense applications, Proc. Battelle Forum, Columbus, OH, November 28, 2005. 9. Baek, S., C. K. Shum, Y. Yi, O.-I. Kwoun, Z. Lu, and A. Braun, Sulzberger ice shelf tidal signal reconstruction using InSAR, EOS Trans. AGU, 86(52), Fall Meet. Suppl., Abstract G42A-08, San Francisco, December 5-9, 2005. 10. Baek, S., O. Kwoun, A. Braun, Z. Lu, and C.K. Shum, Digital Elevation Model of King Edward VII Peninsula, West Antarctica, from SAR Interferometry and ICESat Laser Altimetry, IEEE Geosci. Remote Sensing Lett., vol. 2, no. 4, pp. 413- 417, 2005. 11. Kwoun, O., S. Baek, H. Lee, H. Sohn, U. Han, and C.K. Shum, Topography, Vertical and Horizontal Deformation In the Sulzberger Ice Shelf, West Antarctica Using InSAR, Korean J. Remote Sensing, vol. 21, no. 1, pp. 73-81, 2005. 12. Baek, S., C.K. Shum, H. Lee, Y. Yi, O. Kwoun, Z. Lu, and A. Braun, DEM, Tide and Velocity over Sulzberger Ice Shelf, West Antarctica, Proc. Int. Geosci. Remote. Sensing Sym. 05, pp. 2726-2728, 2005. 13. Baek, S., C. Shum, O. Kwoun, and Z. Lu, Ocean tide modelling underneath Sulzberger Ice Shelf, West Antarctica using interferometric SAR, EOS Trans., AGU, xi 87(36), West. Pac. Geophys. Meeting. Suppl., Abstract G21A-06, Beijing, China, July 2006. FIELDS OF STUDY Major Field: Geodetic Science xii TABLE OF CONTENTS Page ABSTRACT ············································································································································ ii DEDICATION ········································································································································
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