This study finds the relationship between increases in precipitable water vapor (PWV), and intens... more This study finds the relationship between increases in precipitable water vapor (PWV), and intense rainfall events in four different climatological regions of South America’s equatorial northwest: the coast, Andes valley, high mountains, and Amazon. First, the PWV was derived from tropospheric zenith delay measured by Global Navigation Satellite System (GNSS) instrumentation located near meteorological stations within the regions of interest using hourly data from the year 2014. A harmonic analysis approach through continuous wavelet cross-spectrum and coherence, as well as discrete wavelets, was used to determine a measure of the lags found between PWV and specific heavy rain events and then compared with satellite IR images and meteorological anomalies. The link between PWV peaks and rainfall was the most evident on the coast, and less discernible in the other stations possibly due to local dynamic factors. The results showed a lag of 11 h between the preceding PWV increase and an...
International audienceIn the framework of EPOS (EPOS - European Plate Observing System) project i... more International audienceIn the framework of EPOS (EPOS - European Plate Observing System) project implementation phase, an analysis center is hosted in France at Université Grenoble Alpes – CNRS.Within the work package WP10, GNSS data and product, UGA-CNRS is responsible for providing products (position time series and velocity field) generated by a processing using double difference method (via GAMIT/GLOBK software). For this purpose, we developed strategies to take up the up-scaling challenge and generate from a big data set the usual GNSS products. For computational efficiency, the massive data set was split into sub-networks and the GAMIT software launched for each sub-network independently, following the same approach than the one presented in the framework of the PBO project.The informatics resources at our disposal are composed of a management tool for batch processing on computing environments (CiGri) and an open source data management software (IRODS), installed on the high p...
International audienceIn the framework of the implementation phase of the European Plate Observin... more International audienceIn the framework of the implementation phase of the European Plate Observing System (EPOS) project, a pan-European processing center is hosted in Université Grenoble Alpes – CNRS, France. The prototype solution spans the 2005-2015 period, and includes more than 500 European cGPS stations. RInEx data and metadata from RING, NOA and Rénag cGPS networks were downloaded from archive centres (GSAC) maintained in France (CNRS-OCA), Greece (NOA) and Italy (INGV). RINEX data from the European Permanent Network (EPN) were downloaded from the EPN ftp server. Data were processed in double difference with the GAMIT/GLOBK software. The network is first split into daily sub-networks (between 8 and 14 sub-networks) using NETSEL tool included in the GAMIT/GLOBK package. The sub-networks consist in about 40 stations, with 2 overlapping stations. For each day and for each sub-network, the GAMIT processing is conducted independently on the high performance computing platform CIME...
<p>Glacier deformation velocity is typically linked to ice thicknes... more <p>Glacier deformation velocity is typically linked to ice thickness and is very sensitive to parameters of the Glen’s flow law (i.e. rate factor <em>A </em>and flow exponent <em>n</em>). Detailed observations of glacier deformation in the Greenland Ice Sheet (Ryser et al. 2014, Maier et al. 2019, 2021) reveal that the deformation profile close to the bed, where most of the deformation takes place, is not well represented by typical models and is heavily influenced by bed geometry. We present a similar study done on the ablation zone of Argentière Glacier, a temperate glacier in the french Alps. Glacier deformation was observed during 2020 with permanently installed inclinometers that record deformation at high temporal frequency. This data set is complemented with a dense network of GNSS sensors providing surface velocity. Combining the two sets of observations, we are able to reconstruct the deformation profile with depth and the sliding velocity. We show that the Shallow Ice Approximation strongly overestimates shear stress gradients at depth, such that it can lead to a wrong interpretation of deformation profiles. Instead, the use of a three-dimensional full-stokes model enables us to demonstrate that the yearly-averaged deformation profile is poorly sensitive to the flow law exponent n and instead mainly reflects an increase in the  rate factor with depth. We interpret this rate factor increase by an associated increase in water content with depth, as expected from experimental data and field observations (Duval et al., 1977, Vallon et al., 1976). We further show that internal ice deformation also exhibits seasonal variability that is concomitant with and even stronger than surface velocity changes, such that basal sliding actually has to decrease in summer (at least locally) for our observations to be consistent. These results challenge the general view that glacier seasonal variability is mainly due to seasonal variability in sliding velocity. Further work remains to be conducted in order to fully determine the cause for internal deformation seasonality, which may be explained by changes in stress distribution, in water content or to other yet unidentified factors.</p>
This dataset includes solutions processed by ISTerre for all Japanese GNSS stations. These produc... more This dataset includes solutions processed by ISTerre for all Japanese GNSS stations. These products are daily position time series (North, East and Vertical), in the ITRF14 reference frame, calculated from RINEX files using the double difference method with GAMIT software.
Continuous Global Positioning System (cGPS) time series in Guerrero, Mexico, reveal the widesprea... more Continuous Global Positioning System (cGPS) time series in Guerrero, Mexico, reveal the widespread existence of large Slow Slip Events (SSEs) at the boundary between the Cocos and North American plates. The existence of these SSEs asks the question of how seismic and aseismic slips complement each other in subduction zones. We examined the last three SSEs that occurred in 2001/2002, 2006 and 2009/2010, and their impact on the strain accumulation along the Guerrero subduction margin. We use continuous cGPS time series and InSAR images to evaluate the surface displacement during SSEs and inter-SSE periods. The slip distributions on the plate interface associated with each SSE, as well as the inter-SSE (short-term) coupling rates are evaluated by inverting these surface displacements. Our results reveal that the three analyzed SSEs have equivalent moment magnitudes of around 7.5 and their lateral extension is variable.The slip distributions for the three SSEs show that in the Guerrero ...
Velocities from 110 Continuous Global Positioning System (CGPS) stations are used to study the on... more Velocities from 110 Continuous Global Positioning System (CGPS) stations are used to study the on-going deformation of the European Alps and surroundings. The horizontal velocity field reveals that extension dominates the current tectonics of the Western Alps and Rhine graben while compression dominates the current tectonics of the Central and Eastern Alps. Transcurrent tectonics is reported all over the Alps. We compute a kinematic model of the active deformation as well as strain and rotation rates. Major blocks are defined and average translation velocities are constrained. Where data are well distributed the velocity field can be explained well by block motion and localized slip across block boundaries. The reported large ratio of geodetic over seismic strains in the Western Alps is confirmed and is smaller within the Eastern Alps. The vertical velocity field shows larger values over the high elevation parts of the Alps. The Western Alps are likely undergoing larger upward movem...
This study finds the relationship between increases in precipitable water vapor (PWV), and intens... more This study finds the relationship between increases in precipitable water vapor (PWV), and intense rainfall events in four different climatological regions of South America’s equatorial northwest: the coast, Andes valley, high mountains, and Amazon. First, the PWV was derived from tropospheric zenith delay measured by Global Navigation Satellite System (GNSS) instrumentation located near meteorological stations within the regions of interest using hourly data from the year 2014. A harmonic analysis approach through continuous wavelet cross-spectrum and coherence, as well as discrete wavelets, was used to determine a measure of the lags found between PWV and specific heavy rain events and then compared with satellite IR images and meteorological anomalies. The link between PWV peaks and rainfall was the most evident on the coast, and less discernible in the other stations possibly due to local dynamic factors. The results showed a lag of 11 h between the preceding PWV increase and an...
International audienceIn the framework of EPOS (EPOS - European Plate Observing System) project i... more International audienceIn the framework of EPOS (EPOS - European Plate Observing System) project implementation phase, an analysis center is hosted in France at Université Grenoble Alpes – CNRS.Within the work package WP10, GNSS data and product, UGA-CNRS is responsible for providing products (position time series and velocity field) generated by a processing using double difference method (via GAMIT/GLOBK software). For this purpose, we developed strategies to take up the up-scaling challenge and generate from a big data set the usual GNSS products. For computational efficiency, the massive data set was split into sub-networks and the GAMIT software launched for each sub-network independently, following the same approach than the one presented in the framework of the PBO project.The informatics resources at our disposal are composed of a management tool for batch processing on computing environments (CiGri) and an open source data management software (IRODS), installed on the high p...
International audienceIn the framework of the implementation phase of the European Plate Observin... more International audienceIn the framework of the implementation phase of the European Plate Observing System (EPOS) project, a pan-European processing center is hosted in Université Grenoble Alpes – CNRS, France. The prototype solution spans the 2005-2015 period, and includes more than 500 European cGPS stations. RInEx data and metadata from RING, NOA and Rénag cGPS networks were downloaded from archive centres (GSAC) maintained in France (CNRS-OCA), Greece (NOA) and Italy (INGV). RINEX data from the European Permanent Network (EPN) were downloaded from the EPN ftp server. Data were processed in double difference with the GAMIT/GLOBK software. The network is first split into daily sub-networks (between 8 and 14 sub-networks) using NETSEL tool included in the GAMIT/GLOBK package. The sub-networks consist in about 40 stations, with 2 overlapping stations. For each day and for each sub-network, the GAMIT processing is conducted independently on the high performance computing platform CIME...
<p>Glacier deformation velocity is typically linked to ice thicknes... more <p>Glacier deformation velocity is typically linked to ice thickness and is very sensitive to parameters of the Glen’s flow law (i.e. rate factor <em>A </em>and flow exponent <em>n</em>). Detailed observations of glacier deformation in the Greenland Ice Sheet (Ryser et al. 2014, Maier et al. 2019, 2021) reveal that the deformation profile close to the bed, where most of the deformation takes place, is not well represented by typical models and is heavily influenced by bed geometry. We present a similar study done on the ablation zone of Argentière Glacier, a temperate glacier in the french Alps. Glacier deformation was observed during 2020 with permanently installed inclinometers that record deformation at high temporal frequency. This data set is complemented with a dense network of GNSS sensors providing surface velocity. Combining the two sets of observations, we are able to reconstruct the deformation profile with depth and the sliding velocity. We show that the Shallow Ice Approximation strongly overestimates shear stress gradients at depth, such that it can lead to a wrong interpretation of deformation profiles. Instead, the use of a three-dimensional full-stokes model enables us to demonstrate that the yearly-averaged deformation profile is poorly sensitive to the flow law exponent n and instead mainly reflects an increase in the  rate factor with depth. We interpret this rate factor increase by an associated increase in water content with depth, as expected from experimental data and field observations (Duval et al., 1977, Vallon et al., 1976). We further show that internal ice deformation also exhibits seasonal variability that is concomitant with and even stronger than surface velocity changes, such that basal sliding actually has to decrease in summer (at least locally) for our observations to be consistent. These results challenge the general view that glacier seasonal variability is mainly due to seasonal variability in sliding velocity. Further work remains to be conducted in order to fully determine the cause for internal deformation seasonality, which may be explained by changes in stress distribution, in water content or to other yet unidentified factors.</p>
This dataset includes solutions processed by ISTerre for all Japanese GNSS stations. These produc... more This dataset includes solutions processed by ISTerre for all Japanese GNSS stations. These products are daily position time series (North, East and Vertical), in the ITRF14 reference frame, calculated from RINEX files using the double difference method with GAMIT software.
Continuous Global Positioning System (cGPS) time series in Guerrero, Mexico, reveal the widesprea... more Continuous Global Positioning System (cGPS) time series in Guerrero, Mexico, reveal the widespread existence of large Slow Slip Events (SSEs) at the boundary between the Cocos and North American plates. The existence of these SSEs asks the question of how seismic and aseismic slips complement each other in subduction zones. We examined the last three SSEs that occurred in 2001/2002, 2006 and 2009/2010, and their impact on the strain accumulation along the Guerrero subduction margin. We use continuous cGPS time series and InSAR images to evaluate the surface displacement during SSEs and inter-SSE periods. The slip distributions on the plate interface associated with each SSE, as well as the inter-SSE (short-term) coupling rates are evaluated by inverting these surface displacements. Our results reveal that the three analyzed SSEs have equivalent moment magnitudes of around 7.5 and their lateral extension is variable.The slip distributions for the three SSEs show that in the Guerrero ...
Velocities from 110 Continuous Global Positioning System (CGPS) stations are used to study the on... more Velocities from 110 Continuous Global Positioning System (CGPS) stations are used to study the on-going deformation of the European Alps and surroundings. The horizontal velocity field reveals that extension dominates the current tectonics of the Western Alps and Rhine graben while compression dominates the current tectonics of the Central and Eastern Alps. Transcurrent tectonics is reported all over the Alps. We compute a kinematic model of the active deformation as well as strain and rotation rates. Major blocks are defined and average translation velocities are constrained. Where data are well distributed the velocity field can be explained well by block motion and localized slip across block boundaries. The reported large ratio of geodetic over seismic strains in the Western Alps is confirmed and is smaller within the Eastern Alps. The vertical velocity field shows larger values over the high elevation parts of the Alps. The Western Alps are likely undergoing larger upward movem...
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