Determining seasonal displacements of Earth’s crust in South America using observations from space-borne geodetic sensors and surface-loading models

Abstract

There are small pieces of evidence, suggesting that South America's hydrological cycle is changing, which impacts its water availability and, consequently, the Earth's surface due to its elastic response to the surface mass loading/ unloading. Therefore, we analyzed 3 to 15 years of vertical crustal displacements (VCDs) due to mass loadings using 292 Global Positioning System (GPS) stations in South America, which are essential for studies related to tectonic phenomena, for example. Thus, we investigated whether the intra-annual variabilities of the displacements could be reduced using modeled VCDs and inverted displacements from Gravity Recovery and Climate Experiment (GRACE) harmonic solutions (Release 06). The modeled VCDs come from the combination of nontidal atmospheric and ocean loadings with the hydrological loadings from the land-surface model (GLDAS) and reanalysis (MERRA). We found that the highest amplitudes of VCDs of the annual signals are concentrated mainly over the Amazon Rainforest and Brazilian Highlands. However, the results also show different behavior throughout other physiographic provinces of South America, which shows low water capabilities as "sensed" by GRACE and described by the GLDAS and MERRA models. Accordingly, when we disregard the stations over the Andes Mountains and Patagonia in the analysis, the highest reduction in the variability of GPS-observed VCDs is achieved while using GRACE (79% of the sites), MERRA (75% of the sites), and GLDAS (74% of the sites). For these stations, the amplitudes (and phases) of the annual signals depicted by the geodetic sensors generally agree, while those from GLDAS and MERRA explain only approximately 50% of the deformation. However, in the southwest region of South America (between the latitude bands of − 40° to − 30°), GPS annual signals, which reached up to 11 mm, are much larger than those from GRACE and the models due to the existence of lakes that are not resolved in global analysis. These inconsistencies between GPS-observed VCDs and those derived from GRACE and the other models require further investigation, specifically for Chile.

The Assessment of Hydrologic- and Flood-Induced Land Deformation in Data-Sparse Regions Using GRACE/GRACE-FO Data Assimilation

“…Estimating land deformation from land surface or hydrology models can be alternatively considered [5,25,26], particularly to achieve higher spatial resolution than GRACE or improved data availability under an absent gravity data's scenario. Models implement sophisticated physics to represent the water cycle, which can provide an accurate TWS estimate comparable with GRACE results [21].…”

“…Models implement sophisticated physics to represent the water cycle, which can provide an accurate TWS estimate comparable with GRACE results [21]. However, despite the overall positive impacts, model estimates commonly suffer from severe uncertainties associated with, e.g., inadequate physics representation, ineffective model configuration, or inaccurate metrological forcing [27], leading likely to inaccurate or underestimated TWS [25,28]. GRACE data assimilation (DA) can be used to improve model TWS estimates [27].…”

Data Adaptive Analysis on Vertical Surface Deformation Derived from Daily ITSG-Grace2018 Model

“…Actually, the daily or weekly GNSS coordinate time series are common. Therefore, the general practice is averaging daily or weekly GNSS time series to monthly to keep consistent with the monthly gravity field [ 8 , 9 , 10 ]. In fact, the reduction of temporal resolution would affect the signal extraction and its accuracy [ 11 ].…”

“…For monitoring deformation, the combination of geophysical models is another good option in addition to GRACE. The geophysical models satisfy the demand of higher temporal and spatial resolution and many studies have highlighted the feasibility of analyzing the mass loading on GNSS coordinate time series [ 10 , 13 ]. However, the contribution they can explain is generally lower than that which is GRACE-derived.…”

Sistemas Geodésicos de Referência: Rumo ao GGRS/GGRF

“…Um aspecto notável é o de que as variações temporais da latitude e longitude no ITRS são aspectos bem dominados e estabelecidos em modelos globais e regionais de velocidades, enquanto as variações nas altitudes são tópicos de vanguarda nas pesquisas em Geodésia. Nesse aspecto, destacam-se algumas pesquisas globais com participações brasileiras de Montecino et al (2017), Ferreira et al (2019) e Brassarote (2020).…”