The continuous redistribution of water mass involved in the hydrologic cycle leads to deformation of The continuous redistribution of water involved in the hydrologic cycle leads to deformation of the solid Earth. On a global scale, this deformation is well explained by the loading imposed by hydrological mass variations and can be quantified to first order with space-based gravimetric and geodetic measurements. At the regional scale, however, aquifer systems also undergo poroelastic deformation in response to groundwater fluctuations. Disentangling these related but distinct 3D deformation fields from geodetic time series is essential to accurately invert for changes in continental water mass, to understand the mechanical response of aquifers to internal pressure changes as well as to correct time series for these known effects. Here, we demonstrate a methodology to accomplish this task by considering the example of the well-instrumented Ozark Plateaus Aquifer System (OPAS) in central United States. We begin by characterizing the most important sources of groundwater level variations in the spatially heterogeneous piezometer dataset using an Independent Component Analysis. Then, to estimate the associated poroelastic displacements, we project geodetic time series corrected for hydrological loading effects onto the dominant groundwater temporal functions. We interpret the extracted displacements in light of analytical solutions and a 2D model relating groundwater level variations to surface displacements. In particular, the relatively low estimates of elastic moduli inferred from the poroelastic displacements and groundwater fluctuations may be indicative of aquifer layers with a high fracture density. Our findings suggest that OPAS undergoes significant poroelastic deformation, including highly heterogeneous horizontal poroelastic displacements.

Gravity Recovery And Climate Experiment (GRACE) and GRACE-Follow On (GRACE-FO) global monthly measurements of Earth’s gravity field have led to significant advances in the quantification of mass transfer on Earth. Yet, a long temporal gap between missions prevents interpretation of long-term mass variations. Moreover, instrumental and processing errors translate into large non-physical stripes polluting geophysical signals. We use Multichannel Singular Spectrum Analysis (M-SSA) to overcome both issues by exploiting spatio-temporal information of multiple Level-2 GRACE/GRACE-FO solutions. We statistically replace missing data and outliers using iterative M-SSA on Equivalent Water Height (EWH) time series processed by CSR, GFZ, GRAZ, and JPL to form a combined evenly spaced solution. Then, M-SSA is applied to retrieve common signals between each EWH time series and its neighbours to reduce residual spatially uncorrelated noise. We develop a complementary filter, based on the residual noise between fully processed data and a parametric fit to observations, to further reduce persisting stripes. Comparing GRACE/GRACE-FO M-SSA solution with SLR low-degree Earth’s gravity field and hydrological model demonstrates its ability to statistically fill missing observations. Our solution reaches a noise level comparable to mass concentration (mascon) solutions over oceans, without requiring \textit{a priori} information or regularisation. While short-wavelength signals are hampered by filtering of spherical harmonics solutions or challenging to capture using mascon solutions, we show that our technique efficiently recovers localized mass variations using well-documented mass transfers associated with reservoir impoundments.