Abstract
Environmental loading, in particular from continental water storage changes, induces geodetic station displacements up to several centimeters for the vertical components. We investigate surface deformation due to loading processes in South America using a set of 247 permanent GPS (Global Positioning System) stations for the 2003–2016 period and compare them to loading estimates from global circulation models. Unfortunately, some of the hydrological components, and in particular surface waters, may be missing in hydrological models. This is especially an issue in South America where almost half of the seasonal water storage variations are due to surface water changes, e.g., rivers and floodplains. We derive river storage variations by rerouting runoffs of global hydrology models, allowing a better agreement with the mass variations observed from GRACE (Gravity Recovery and Climate Experiment) mission. We extract coherent seasonal GPS displacements using Multichannel Singular Spectrum Analysis (M-SSA) and show that modeling the river storage induced loading effects significantly improve the agreement between observed vertical and horizontal displacements and loading models. Such an agreement has been markedly achieved in the Amazon basin. Whilst the initial models only explained half of the amplitude of GPS, the new ones compensate for these gaps and remain consistent with GRACE.
Highlights
Earth’s crustal deformations, such as tectonic plate motions, volcanism, and landslides, arise at a range of scales in space and time ranging from local to continental scale and from seconds to millions of years, respectively
We present the different results obtained concerning the annual signal for the initial loading models and the new models adding the river contribution, as well as the loading deformation time series inferred from Gravity Recovery and Climate Experiment (GRACE)
%RC1 mean values can be observed for the North and East components, which reach the values of 52.1% and 43.4% respectively, for the Amazon and 58.6% and 31.1% respectively, for the Parana. These results suggest that the portion of the annual signal in the Global Positioning System (GPS) time series is in the order of 60% for the stations located in the river basins and in the order of slightly less than 50% for the North and East components in the same zones
Summary
Earth’s crustal deformations, such as tectonic plate motions, volcanism, and landslides, arise at a range of scales in space and time ranging from local to continental scale and from seconds to millions of years, respectively. Detectable changes in the shape of the solid Earth and its gravity field arise due to the varying mass distribution of the surface fluids (oceans, atmosphere, groundwater, soil moisture, lakes, snow and ice) [1]. A secular signal (Glacial Isostatic Adjustment) is induced by the Earth’s response to past fluctuations of ice sheets, comprising large, measurable changes in sea level, 3D crustal motion, the gravity field, and Earth’s rotation [2]. Analysis of loading signal provides a better understanding of the interaction between the solid Earth and the mass redistributions at its surface linked to natural climate variability and human activities. Better understanding of these interactions is essential for Remote Sens.
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