Our water resources have changed over the last century through a combination of water management evolutions and climate change. Understanding and decomposing these drivers of discharge changes is essential to preparing and planning adaptive strategies. We propose a methodology combining a physical-based model to reproduce the natural behavior of river catchments and a parsimonious model to serve as a framework of interpretation, comparing the physical-based model outputs to observations of discharge trends. We show that over Europe, especially in the South, the dominant explanations for discharge trends are non-climatic factors. Still, in some catchments of Northern Europe, climate change seems to be the dominating driver of change. We hypothesize that the dominating non-climatic factors are irrigation development, groundwater pumping and other human water usage, which need to be taken into account in physical-based models to understand the main drivers of discharge and project future changes.

The southeastern margin of the Tibetan Plateau has undergone complex deformation since the Cenozoic, resulting in a high level of seismicity and seismic hazard. Knowledge about the seismic anisotropy provides important insight about the deformation mechanism and the regional seismotectonics beneath this tectonically active region. In this study, we conduct fullwave multi-scale tomography to investigate the seismic anisotropy in the southeastern margin of the Tibetan Plateau. Broadband records at 111 permanent stations in the region from 470 teleseismic events are used to obtain 5,216 high-quality SKS splitting intensity measurements, which are then inverted in conjunction with 3D sensitivity kernels to obtain an anisotropic model with multi-scale resolution. Resolution tests show that our dataset recovers anisotropy anomalies reasonably well on the scale of 1º x 1º horizontally and ~100 km vertically. Our result suggests that in the southeastern margin of the Tibetan Plateau the deformation in the lithosphere and asthenosphere are decoupled. The anisotropy in the lithosphere varies both laterally and vertically as a result of dynamic interactions of neighboring blocks as well as lithospheric reactivation. The anisotropy in the asthenosphere largely follows the direction of regional absolute plate motion. The SKS splittings observed at the surface are shown to be consistent with the vertical integral of our depth-dependent anisotropy model over lithospheric and asthenospheric depths.

In this study, 27 soil samples were collected for laboratory pretreatment and the total concentration of heavy metal Cd, Cr, Cu, Ni, Pb, Zn, As and Hg was measured. Pearson correlation analysis was carried out on the measured data after removing outliers, and the comparison groups with a significant correlation at the level of 0.01 between the concentration of several groups of elements were obtained. In order to identify effectively source of soil heavy metals by PMF analysis (Positive Matrix Factorization), we drew the location map in the study area and the concentration distribution of heavy metals. Combining Pearson correlation analysis, distribution of heavy metal concentration and PMF analysis, we obtained convincing identification results of heavy metal sources. With C# language and ArcGIS Engine development components, we developed a soil heavy metal database management system to manage the spatial and attribute data needed in source apportionment for soil heavy metals, which will provide data support for the latter sustainable research. In this paper, we proposed a sustainable heavy metal pollution identification research process, SSAPD (sustainable source analysis process based on database), which includes data collection in the field, laboratory measurement, pretreatment, PMF pollution source analysis and database establishment. The process can not only effectively identify the source of soil heavy metal pollution, but also realize the continuity of research and the sharing of data.

We present an upscaled Lagrangian approach to predict the plume evolution in highly heterogeneous aquifers. The model is parameterized by transport independent characteristics such as the statistics of hydraulic conductivity and the Eulerian flow speed. It can be conditioned on the tracer properties, the conductivity data at the injection region, and is able to account for mobile-immobile mass transfer. Thus, the model is transferable to different solutes and hydraulic conditions. It captures the large scale non-Gaussian features for the evolution of the longitudinal mass distribution observed for the bromide and tritium tracer plumes at the macrodispersion experiment (MADE) site (Columbus, Ohio, USA), which are characterized by a slow moving peak and pronounced forward tailing. These large scale features are explained by advective tracer propagation due to a broad distribution of spatially persistent Eulerian flow speeds as a result of spatial variability in hydraulic conductivity.

Firstly, we re-tune an algorithm based on empirical orthogonal functions (EOF) for globally retrieving the chlorophyll a concentration (Chl-a) of phytoplankton functional types (PFTs) from multi-sensor merged ocean color (OC) products. The re-tuned algorithm, namely EOF-SST hybrid algorithm, is improved by: (i) using 30% more matchups between the updated global in situ pigment database and satellite remote sensing reflectance (Rrs) products, and (ii) including sea surface temperature (SST) as an additional input parameter. In addition to the Chl-a of the six PFTs (diatoms, haptophytes, dinoflagellates, green algae, prokaryotes and Prochlorococcus), the fractions of prokaryotes and Prochlorococcus Chl-a to total Chl-a (TChl-a), are also retrieved by the EOF-SST hybrid algorithm. Matchup data are further separated for low and high temperature regimes based on different PFT dependences on SST, to establish the SST-separated hybrid algorithms which further shows improved performance as compared to the EOF-SST hybrid algorithm. The per-pixel uncertainty of the retrieved TChl-a and PFT products is estimated by taking into account the uncertainties from both input data and model parameters through Monte Carlo simulations and analytical error propagation. The uncertainty assessment provided within this study sets the ground to extend the long-term continuous satellite observations of global PFT products by transferring the algorithm and its method to determine uncertainties to similar OC products until today. Satellite PFT uncertainty is also essential to evaluate and improve coupled ecosystem-ocean models which simulate PFTs, and furthermore can be used to directly improve these models via data assimilation.

Using a recently developed 1/12th degree regional ocean model, we establish a link between U.S. East Coast sea level variability and offshore upper-ocean heat content change. This link manifests as a cross-shore mass redistribution driven by an offshore thermosteric sea level response to subsurface warming or cooling. Approximately 50\% of simulated monthly to inter-annual coastal sea level variance south of Cape Hatteras can be statistically accounted for by this mechanism, realized as a function of regional ocean hypsometry, gyre scale warming, and the depth-dependence of density change. This response to offshore warming explains the non-stationarity of U.S. East coast sea level covariance, specifically observed and modeled behavior after $\sim$ 2010. Since approximately 2010, elevated rates of sea level rise south of Cape Hatteras can be partly explained as the result of shore-ward mass redistribution due to offshore sub-surface warming within the North Atlantic subtropical gyre. These results reveal a mechanism that connects local coastal sea level to a broader region and identifies the influence of regional heat content changes on coastal sea level. This analysis presents a framework for identifying new regions that may be susceptible to enhanced sea level rise due to ocean warming and helps bridge the gap between quantifying large scale change and anticipating local coastal impacts like flooding and storm surge.

A dynamic one-dimensional model of the freezing of first-year sea ice with a snow cover is presented along with Matlab code. The model is based on historical models in the literature, and is primarily intended to design a computational tool that accurately simulates transient temperature changes within growing sea ice. This may complement temperature data at various depths and times in growing sea ice. The model is validated by comparing the simulated ice temperature profile and growth rate to thermistor temperature profiles measured in 1997 in McMurdo Sound, Antarctica. This comparison shows evidence of platelet ice growth. Despite this, an accuracy of ±0.4 o C is achieved throughout the entire ice temperature profile, when comparing simulated transient temperatures to data. The model is also used, with the inclusion of a 15mm thick snow layer, to correct a previously observed discrepancy between ice growth rates measured via banding structures in ice cores and the predictions of a steady state ice growth model.

Climate change affects the water cycle. Despite the improved accuracy of simulations of historical temperature, precipitation and runoff in the latest Coupled Model Intercomparison Project Phase 6 (CMIP6), the uncertainty of the future sensitivity of global runoff to temperature remains large. Here, we identify an emergent relationship between the historical sensitivity of precipitation to temperature change (1979–2014) and the future sensitivity of runoff to temperature change (2015–2100), which can be used to constrain future runoff sensitivity estimates. Using this constraint, we estimate that the uncertainties in future sensitivity of runoff have been reduced by 7.2 – 12.0%. The constrained sensitivity of runoff is much larger (36 – 104%) than that directly inferred from original CMIP6 projections. Our constrained sensitivities also indicate more extreme wet conditions and fewer dry conditions. These results suggest that the future global land water cycle is accelerating and comes with more hydroclimatic extremes than previously projected

Exposed sections of accretionary orogens allow reconstruction of their tectonic evolution. Most commonly, orogens are characterised by two-dimensional shortening perpendicular to the orogenic front. We describe the mid-crustal section of the back-arc of the early Paleozoic Famatinian accretionary orogen, exposed in the Sierra de Quilmes. Here crustal deformation evolved from a typical two-dimensional shortening with tectonic transport towards the west, to a non-coaxial constrictional strain with a southward tectonic transport parallel to the orogen. During the early phase of deformation, HT-LP metamorphic complexes were juxtaposed by west-directed thrusting on remarkably thick shear zones forming a thrust duplex. Deformation of the buried footwall complex continued after the exhumed hanging wall ceased to deform. We suggest that the thermally-weakened footwall complex responded by initiating a phase of south-verging thrusting, parallel to the orogen, associated with strong constriction, associated with L-tectonites, and sheath folds. This late phase of deformation defines a non-coaxial constrictional regime characterized by simultaneous east-west and vertical shortening and strong north-south, orogen-parallel stretching. Titanite ages and Zr-in-titanite thermometry demonstrate that this back-arc remained above 700 °C for 120 Ma between 500 and 380 Ma. Combined with regional geology, the new data suggest that west-verging thrusting interrupted an early, back-arc extensional phase, and lasted from ~ 470 to 440 Ma, and that footwall constriction and south-verging thrusting continued for another 40 to 60 Ma. The Famatinian back-arc exposed in Sierra de Quilmes thus is an example of how shortening and orogenic growth in a hot orogen was counterbalanced by lateral flow.

Theoretical studies predict that during earthquake rupture faults slide at non-constant slip velocity, however it is not clear which source time functions are compatible with the high velocity rheology of earthquake faults. Here we present results from high velocity friction experiments with non-constant velocity history, employing a well-known seismic source solution compatible with earthquake source kinematics. The evolution of friction in experiments shows a strong dependence on the applied slip history, and parameters relevant to the energetics of faulting scale with the impulsiveness of the applied slip function. When comparing constitutive models of strength against our experimental results we demonstrate that the evolution of fault strength is directly controlled by the temperature evolution on and off the fault. Flash heating predicts weakening behaviour at short timescales, but at larger timescales strength is better predicted by a viscous creep rheology. We use a steady-state slip pulse to test the compatibility of our strength measurements at imposed slip rate history with the stress predicted from elastodynamic equilibrium. Whilst some compatibility is observed, the strength evolution indicates that slip acceleration and deceleration might be more rapid than that imposed in our experiments.

A document by Shan Shan. Click on the document to view its contents.

Quantifying evapotranspiration is critical to accurately predict vegetation health, groundwater recharge, and streamflow generation. Hillslope aspect, the direction a hillslope faces, results in variable incoming solar radiation and subsequent vegetation water use that influence the timing and magnitude of evapotranspiration. Previous work in forested landscapes has shown that equator-facing slopes have higher evapotranspiration due to more direct solar radiation and higher evaporative demand. However, it remains unclear how differences in vegetation type (i.e., grasses and trees) influence evapotranspiration and water partitioning between hillslopes with opposing aspects. Here, we quantified evapotranspiration and subsurface water storage deficits between a pole- and equator-facing hillslope with contrasting vegetation types within central coastal California. Our results suggest that cooler pole-facing slopes with oak trees have higher evapotranspiration than warmer equator-facing slopes with grasses, which is counter to previous work in landscapes with singular vegetation types. Our water storage deficit calculations indicate that the pole-facing slope has a higher subsurface storage deficit and a larger seasonal dry down than the equator-facing slope. This aspect difference in subsurface water storage deficits may influence subsequent deep groundwater recharge and streamflow generation. In addition, larger root-zone storage deficits on pole-facing slopes may reduce their ability to serve as hydrologic refugia for oaks during periods of extended drought. This research provides a novel integration of field-based and remotely-sensed estimates of evapotranspiration required to properly quantify hillslope-scale water balances. These findings emphasize the importance of resolving hillslope-scale vegetation structure within Earth system models, especially in landscapes with diverse vegetation types.

It has been standard practice for about two decades to compute GPS-based station velocity uncertainties using the apparent noise statistics of the non-linear position residuals rather than assume white noise (WN) behavior. The latter choice would yield unrealistic velocity uncertainties. The most common noise types used are power-law, usually close to flicker noise (FN), over most frequencies mixed with WN at the shortest periods. The complicating impact of offsets in the position time series, mostly caused by equipment changes or tectonic events, has not been fully appreciated. These are far less benign than recently suggested. In addition to contributing a pseudo-random walk noise (RW) component to the velocity errors, estimating offset parameters changes the apparent noise color towards whiter. Spectral power is effectively drained by offsets at periods longer than roughly the mean span between them. This consequently promotes a Gauss-Markov process as the apparently preferred noise model and, importantly, obscures the presence of RW and long-period Earth deformation in the series. Both effects can lead to potentially under-estimated velocity uncertainties. The full value of decadal-long GPS time series for geodynamical applications is thereby greatly eroded by recurring offsets, especially when they occur quasi-regularly. In addition, contrary to common assumption, the noise color is generally not fixed with time, but clearly becomes whiter in more recent data. The origin of the colored noise and its whitening over time remain elusive.

Two-phase flow of CO2/brine in porous media is critical to the capacity and safety of carbon sequestration into the brine aquifer. In order to provide valuable information and important theoretical basis for site selection and CO2 injection, the microscopic visualization technology was employed in this study to conduct displacement experiments of CO2/brine at the pore scale. Four micromodels with different sizes and structures, five injection rates of CO2 and six salinities of brine were used to study the effects of micromodel’s structure and displacement pattern on two-phase flow. Several parameters including the differential pressure, contact angle, permeability, velocity field and force field were obtained by experimental measurement, image post-processing and theoretical analysis, and then these parameters’ variation was investigated. Phenomena such as thin film, corner flow and Haines jump were also found during the displacement. Although brine could be completely displaced by CO2 in the capillary duct, the backflow of wetting phase would occur at low injection rate. Phenomena different from the theoretical analysis also occurred in pore doublet models: some brine was residual in the homogeneous pore doublet model at low injection rate, while the heterogeneous pore doublet model was fully occupied by CO2 at high injection rate. These phenomena are very useful for two-phase flow, and multiple factors need to be comprehensively considered to determine the operating conditions of CO2 storage into the brine aquifer.

Anthropogenic activities such as fluid injection, fluid extraction, mining, and hydraulic fracturing can all cause induced seismicity which can in turn result in land subsidence. This latter phenomenon is devastating to local infrastructure as well as underlying aquifers. It is for this reason that monitoring and predicting land deformation is of utmost importance. We relied on Interferometric Synthetic Aperture Radar (InSAR) images captured by Sentinel-1 to monitor deformation in the line-of-sight of the satellite. The Geysers geothermal field, where injection plays a direct role in induced seismicity, was used as the area of study and a deformation time series was built using LiCSBAS [1]. Two machine learning models (model A and model B) that included Long Short-Term Memory (LSTM) and Convolutional Neural Network (CNN) layers were built to predict future deformation maps. The only difference between the models was the incorporation of geothermal injection and production data in model B. While both models outperformed a baseline linear model, it was model B that performed the best based on a mean squared error metric.

In this study, we evaluated the variations of air quality in Lanzhou, a typical city in Northwestern China impacted by the COVID-19 lockdown. The mass concentration and chemical composition of non-refractory submicron particulate matter (NR-PM) were determined by a high-resolution aerosol mass spectrometry from January to March 2020. The concentration of NR-PM dropped by 40% from pre- to during control period. The five aerosol components (sulfate, nitrate, ammonium, chloride, and organic aerosol (OA)) were all decreased during control period with the largest from secondary inorganic species (70% of the total reduction), whereas the OA sources did not vary synchronously. OA from coal and biomass burning remained stably from pre- to during control period, while traffic and cooking related emissions were reduced by 30% and 50%, respectively. The production rates for secondary inorganic and organic aerosols were also evaluated and represented a decreased trend from pre- to during control periods.

We report observations of the ion dynamics inside an Alfven branch wave that propagates near the reconnecting dayside magnetopause. The measured frequency, wave normal angle and polarization are within 1% with the predictions of a dispersion solver, and indicate that the wave is an electromagnetic ion cyclotron wave with very oblique wave vector. The magnetospheric plasma contains hot protons (keV), cold protons (eV), plus some heavy ions. The cold protons follow the magnetic field fluctuations and remain frozen-in, while the hot protons are at the limit of magnetization. The cold proton velocity fluctuations contribute to balance the Hall term in Ohm’s law, allowing the wave polarization to be highly-elliptical and right-handed, a necessary condition for propagation at oblique wave normal angles. The dispersion solver indicates that increasing the cold proton density facilitates generation and propagation of these waves at oblique angles, as it occurs for the observed wave.

The location and origin of Neoproterozoic-Cambrian sutures provide keys to understand the formation and evolution of the supercontinent Gondwana. The Larsemann Hills is located near a major Neoproterozoic-Cambrian suture zone in the Prydz Belt, but has not been examined locally by comprehensive geophysical studies. In this study, we analyzed data collected from a 1-D joint seismic-MT array deployed during the 36th Chinese National Antarctic Research Expedition. We found that a sharp Moho discontinuity offset of 6-8 km shows up in the stacked image of teleseismic P-wave receiver function analysis; coinciding with the abrupt Moho offset, a near-vertical channel with (1) low resistivity extending to the uppermost mantle depths, and (2) a high crustal Poisson’s ratio in the crust is identified. These findings provide evidence for the determination of the location and collisional nature of the Prydz belt or a portion of it.