Application of TOPEX Altimetry for Solid Earth Deformation Studies

Abstract

This study demonstrates the use of satellite radar altimetry to detect solid Earth deformation signals such as Glacial Isostatic Adjustment (GIA). Our study region covers moderately flat land surfaces seasonally covered by snow/ice/vegetation. The maximum solid Earth uplift of ~10 mm yr -1 is primarily due to the incomplete glacial isostatic rebound that occurs around Hudson Bay, North America. We use decadal (1992 -2002) surface height measurements from TOPEX/POSEIDON radar altimetry to generate height changes time series for 12 selected locations in the study region. Due to the seasonally varying surface characteristics, we first perform radar waveform shape classification and have found that most of the waveforms are quasi-diffuse during winter/spring and specular during summer/fall. As a result, we used the NASA β-retracker for the quasidiffuse waveforms and the Offset Center of Gravity or the threshold retracker for the specular waveforms, to generate the surface height time series. The TOPEX height change time series exhibit coherent seasonal signals (higher amplitude during the winter and lower amplitude during the summer), and the estimated deformation rates agree qualitatively well with GPS vertical velocities, and with altimeter/tide gauge combined vertical velocities around the Great Lakes. The TOPEX observations also agree well with various GIA model predictions, especially with the ICE-5G (VM2) model with differences at 0.2 ± 1.4 mm yr -1 , indicating that TOPEX has indeed observed solid Earth deformation signals manifested as crustal uplift over the former Laurentide Ice Sheet region.

Time-varying land subsidence detected by radar altimetry: California, Taiwan and north China

“…Here we adopted a modified, enhanced version of the repeat-track method 32 33 34 for the space and time reduction of raw height measurements from TP, J1, J2 and EN. For EN, we also estimated parameters that account for the effects of backscatter and the slopes of the leading and trailing edges 32 35 .…”

High-resolution datasets for lake level changes in the Qinghai-Tibetan Plateau from 2002 to 2021 using multi-altimeter data

“…The waveforms for inland water bodies are easily contaminated or even submerged by signals from land, hence it is difficult to obtain the distance from the altimeter to the nadir points. Accordingly, the retracking correction plays an important role in 120 removing the contamination by land signals when radar altimetry data are applied to inland water bodies (Martin et al, 1983;Lee et al, 2008). In this study, the automatic multiscale-based peak detection retracker (AMPDR) (Chen et al, 2020), which is suitable for different altimetry and different situations to derive reliable water levels, was used on the altimeter data product.…”

Geodetic Constraints on the Qinghai-Tibetan Plateau Present-Day Geophysical Processes

“…Satellite radar altimetry measurements, originally designed to observe deep-ocean sea level and circulation, have been used to detect solid Earth deformation, e.g., the Laurentian GIA, with an accuracy of several mm yr -1 (Lee et al 2008a(Lee et al , 2008b. The limitation of this technique is that the radar echo loses lock if the terrain is mountainous.…”

“…2 is a schematic which summarizes the active competing geophysical and climatic processes taking place over the Tibetan Plateau, along with plausible contemporary space geodetic techniques, which could provide constraints and thus potentially separate some of these processes. In this study, we present an assessment of the magnitudes of these processes and their possible detections or constraints using multiple satellite geodetic techniques in addition to GPS, namely radar altimetry from TOPEX/ POSEIDON measuring solid Earth deformation which has been demonstrated over the land region of Hudson Bay observing glacial isostatic adjustment (Lee et al 2008a), and space gravimetry from the Gravity Recovery and Climate Experiment (GRACE) twin-satellites (Tapley et al 2004). The former is sensitive only to surface changes, whereas the latter is sensitive to both surface and subsurface changes.…”