Vertical deformation and residual altimeter systematic errors around continental Australia inferred from a Kalman-based approach

Abstract

We further developed a space–time Kalman approach to investigate time-fixed and time-variable signals in vertical land motion (VLM) and residual altimeter systematic errors around the Australian coast, through combining multi-mission absolute sea-level (ASL), relative sea-level from tide gauges (TGs) and Global Positioning System (GPS) height time series. Our results confirmed coastal subsidence in broad agreement with GPS velocities and unexplained by glacial isostatic adjustment alone. VLM determined at individual TGs differs from spatially interpolated GPS velocities by up to ~ 1.5 mm/year, yielding a ~ 40% reduction in RMSE of geographic ASL variability at TGs around Australia. Our mission-specific altimeter error estimates are small but significant (typically within ~ ± 0.5–1.0 mm/year), with negligible effect on the average ASL rate. Our circum-Australia ASL rate is higher than previous results, suggesting an acceleration in the ~ 27-year time series. Analysis of the time-variability of altimeter errors confirmed stability for most missions except for Jason-2 with an anomaly reaching ~ 2.8 mm/year in the first ~ 3.5 years of operation, supported by analysis from the Bass Strait altimeter validation facility. Data predominantly from the reference missions and located well off narrow shelf regions was shown to bias results by as much as ~ 0.5 mm/year and highlights that residual oceanographic signals remain a fundamental limitation. Incorporating non-reference-mission measurements well on the shelf helped to mitigate this effect. Comparing stacked nonlinear VLM estimates and altimeter systematic errors with the El Niño-Southern Oscillation shows weak correlation and suggests our approach improves the ability to explore nonlinear localized signals and is suitable for other regional- and global-scale studies.

An Ellipsoidal Plate Motion Model of the Indo‐Australian Tectonic Plate

“…In Table 3, there is a mean geodetic vertical velocity (“Up”) of −0.811 mm/year which is consistent with the results presented by Rezvani et al. (2022) and Riddell et al. (2020), where the mean rate of subsidence is reasonably spatially coherent and cannot be explained by Glacial Isostatic Adjustment alone.…”

“…In Table 3, there is a mean geodetic vertical velocity ("Up") of 0.811 mm/year which is consistent with the results presented by Rezvani et al (2022) and Riddell et al (2020), where the mean rate of subsidence is reasonably spatially coherent and cannot be explained by Glacial Isostatic Adjustment alone. These mean velocities have variations across the high-quality data points of ±10.388 mm/year in the East direction, ±4.265 mm/ year in the North direction and ±0.446 mm/year in the Up direction.…”

Non‐Linear Vertical Land Motion of Coastal Chile and the Antarctic Peninsula Inferred From Combining Satellite Altimetry, Tide Gauge and GPS Data

“…We note that our findings will be partially influenced by the adverse effect of residual oceanography (including residual tides not captured using our approach) between the measurement locations of the altimeters and TGs (e. g., Nerem & Mitchum, 2002;Rezvani et al, 2022), the impact of inadequately edited data to account for sea-ice contamination (e.g., this is the likely driver for the anomalous spike in the estimated VLM time series at ROTH TG around 2016-2017 shown in Figure 5), and datum instability of gauge records below our detection resolution (e.g., Rezvani et al, 2021). The residual oceanographic signals are less likely to impact the estimation of coseismic signals, but more likely to influence the estimates of site-specific VLM at some level.…”

“…In some cases, TGs provide an additional observation type that could potentially assist in constraining the estimates of rheological structure, yet they are poorly utilized by the solid-Earth community. We have advanced the approach of Rezvani et al (2021Rezvani et al ( , 2022 to create a flexible framework with the capability to quantify abrupt co-seismic jumps and substantial changes in coastal VLM by combining the available geodetic data sets from multi-mission satellite altimeters, long-running TGs, and GPS stations since the early 1990s. These developments allow the retrieval of vertical motion series of the Earth's surface that vary significantly in time, such as those associated with viscoelastic deformation due to earthquakes or changes in surface loading.…”

“…Within the procedure, we assimilated the absolute sealevel records from multi-mission altimeters and the relative sea-level measurements from tide gauges, and made use of altimeter tandem/dual crossovers, and GPS height series dating back to ∼1992. As a significant advance from our previous work (Rezvani et al, 2021(Rezvani et al, , 2022, this flexible framework provides an opportunity to examine highly non-linear signals of vertical land motion at TG locations, including inter-seismic, co-seismic, and postseismic deformation, along with rapid unloading of the solid-Earth due to ice mass loss. Through an iterative datadriven scheme, we gradually separated highly-correlated unknowns within a multi-step solution strategy, and accounted for the time-correlated noise at individual measuring locations and spatiotemporal covariances within each set of the observational series.…”