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Satellite Geodesy Methods for Studying Changes in Polar Ice Mass and Terrestrial Water Storage

Lai, Yen-Ru
http://orcid.org/0000-0002-5010-839X
http://rave.ohiolink.edu/etdc/view?acc_num=osu1701268169289035

Abstract Details

2023, Doctor of Philosophy, Ohio State University, Civil Engineering.
Satellite gravimetry (Gravity Recovery and Climate Experiment (GRACE)) detects spatiotemporal gravity variations resulting from mass changes in the cryosphere and hydrosphere. However, it is confronted with challenges, such as limited spatial resolution (approximately 330 km) and signal leakage at the ocean–land interface. This study employs alternative satellite geodesy methods providing higher spatial resolution than typical methods. Accordingly, they enable more detailed analysis for exploring mass changes in the Greenland Ice Sheet (GrIS) and fluctuations in terrestrial water storage (TWS) across the United States. In the context of ice melting studies, satellite radar and laser altimetry deliver precise measurements of surface elevation changes (SECs) with spatial resolutions ranging from a few hundred meters to several kilometers. This enables a thorough investigation of variations in individual glaciers. Additionally, the continuous Ku-band radar altimetry missions allow for the generation of SEC time series dating back to 1992. However, the previous methods are incapable of incorporating data contributions from neighboring grids, potentially introducing biases or artificial signals. To resolve this problem, an innovative Kalman filter integration method is developed. The resulting monthly SEC product offers unprecedented accuracy. Furthermore, a stochastic filter is employed to estimate time-dependent rates instead of relying on constant rates over specific periods. Complex patterns of acceleration and deceleration in SEC have been observed across various ocean-terminating glaciers. Notably, the GrIS did not experience significant mass loss from 1995 to 2000. However, before 2000, the melting of GrIS began to accelerate, with the most severe melting occurring from 2011 to 2013, especially along the western Greenland coastal areas. Subsequently, ice melting gradually decelerated until 2017; however, it accelerated again in 2019–2020. Presently, the GrIS is undergoing a deceleration phase in its ice loss. Changes in TWS lead to elastic deformations in Earth’s crust. These deformations can be precisely detected using the global navigation satellite system (GNSS) technique. In the geophysical inversion process utilizing the GNSS positioning time series to derive TWS estimates, regularization techniques are essential to deal with the ill-posed problem. Although regularization enhances stability, it also introduces biases into estimates. Additionally, the non-uniform distribution of GNSS stations results in spatially varying biases. In this study, a statistical method known as the generalized cross-validation (GCV) method is explored to determine the regularization parameter instead of relying on empirical choices. Two classical regularization methods whose potential biases are examined are employed: second-order Tikhonov regularization and truncated singular value decomposition (TSVD). Through a simulation study conducted over the USA, the GCV criteria are observed to produce TWS estimates approximating the optimal values at different noise levels for both regularization methods. However, in real-world cases, the TSVD-GCV solutions exhibit severe local unsmoothed patterns, which may be influenced by local high-frequency signals or possibly contaminated by data noise in candidates with high K values. In the watersheds defined by the United States Geological Survey, the TWS seasonal amplitudes obtained by GNSS inversion align with the hydrologic model. In contrast, the GRACE mascon products exhibit amplitudes exceeding those from the model and GNSS estimates by approximately 100 Gt.
Lei Wang (Advisor)
Gil Bohrer (Committee Member)
Michael Bevis (Committee Member)
180 p.
Civil Engineering
Satellite Geodesy, Ice Mass Change, and Terrestrial Water Storage Change

Recommended Citations

Citations

  • Lai, Y.-R. (2023). Satellite Geodesy Methods for Studying Changes in Polar Ice Mass and Terrestrial Water Storage [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1701268169289035

    APA Style (7th edition)

  • Lai, Yen-Ru. Satellite Geodesy Methods for Studying Changes in Polar Ice Mass and Terrestrial Water Storage. 2023. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1701268169289035.

    MLA Style (8th edition)

  • Lai, Yen-Ru. "Satellite Geodesy Methods for Studying Changes in Polar Ice Mass and Terrestrial Water Storage." Doctoral dissertation, Ohio State University, 2023. http://rave.ohiolink.edu/etdc/view?acc_num=osu1701268169289035

    Chicago Manual of Style (17th edition)

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© 2023, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.
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