Abstract. We study the time series of vertical ground displacements from
continuous global navigation satellite system (GNSS) stations located in the European Alps. Our goal is to
improve the accuracy and precision of vertical ground velocities and spatial
gradients across an actively deforming orogen, investigating the spatial and
temporal features of the displacements caused by non-tectonic geophysical
processes. We apply a multivariate statistics-based blind source separation
algorithm to both GNSS displacement time series and ground displacements
modeled from atmospheric and hydrological loading, as obtained from global
reanalysis models. This allows us to show that the retrieved geodetic
vertical deformation signals are influenced by environment-related
processes and to identify their spatial patterns. Atmospheric loading is the
most important process, reaching amplitudes larger than 2 cm, but
hydrological loading is also important, with amplitudes of about 1 cm, causing the peculiar spatial
features of GNSS ground displacements: while the displacements caused by
atmospheric and hydrological loading are apparently spatially uniform, our
statistical analysis shows the presence of N–S and E–W displacement gradients. We filter out signals associated with non-tectonic deformation from the GNSS
time series to study their impact on both the estimated noise and linear
rates in the vertical direction. Taking into account the long time span of the time series considered in this work, while the impact of filtering on rates appears rather limited, the uncertainties estimated from filtered time series assuming a power
law plus white noise model are significantly reduced, with an important
increase in white noise contributions to the total noise budget. Finally, we
present the filtered velocity field and show how vertical ground velocity
spatial gradients are positively correlated with topographic features of the
Alps.