The storage of fluids in the subsurface is critical for a broad spectrum of applications including managed aquifer recharge, storage of liquified carbon dioxide and hydrogen, geothermal heat extraction and management of hydrocarbon resources. It is surprising then, that there has been relatively little measurement of the vertical distribution of fluid storage in geologic formations as compared with permeability. We present experiments in which fluid was injected into an important regional aquifer and the depth-dependent strain response measured using fiber optic distributed acoustic sensing. The formation expansion and contraction in response to fluid injection were measured in nanostrain. Strain, and the implied storage distribution, was highly localized in specific strata and demonstrated complex, (non-elastic and non-local) hydromechanical behavior. This new window into fluid-geomechanical coupling undermines some typically use models and observations, currently in practice, but provides potential for complete representation and prediction of fluid storage in the subsurface.

Machine learning approaches, such as random forests, have been used to effectively emulate various aspects of climate and weather models in recent years. The limitations to these approaches are not yet known, particularly with regards to varying complexity of the underlying physical parameterization scheme within the climate model. Utilizing a hierarchy of model configurations, we explore the limits of random forest emulator skill using simplified model frameworks within NCAR's Community Atmosphere Model, version 6 (CAM6). These include a dry CAM6 configuration, a moist extension of the dry model, and an extension of the moist case that includes an additional convection scheme. Each model configuration is run with identical resolution and over the same time period. With unique random forests being optimized for each tendency or precipitation rate across the hierarchy, we create a variety of "best case" emulators. The random forest emulators are then evaluated against the CAM6 output as well as a baseline neural network emulator for completeness All emulators show significant skill when compared to the "truth" (CAM6), often in line with or exceeding similar approaches within the literature. In addition, as the CAM6 complexity is increased, the random forest skill noticeably decreases, regardless of the extensive tuning and training process each random forest goes through. This indicates a limit on the feasibility of random forests to act as physics emulators in climate models and encourages further exploration in order to identify ideal uses in the context of state-of-the-art climate model configurations.

We present a novel tectonic and structural framework for the Sumatran Volcanic Arc and Sumatran Fault System (SFS), based on a comprehensive compilation of the controls of heterogeneities in both subducting and overriding plate on the local to lithospheric-scale geology. A new conceptual model is proposed to explain the interaction between pre-existing inherited basement structures, which are well exposed along the arc, with the much younger SFS. The model also illustrates the relationship between brittle deformation and nearby magmatism-volcanism. We present a novel structural restoration of the island prior to the SFS strike-slip faulting contributing to in-depth understanding of the initial condition of the island, especially in view of the basement structures underlying the volcanic arc and the inherited basement structures. More detailed structural analysis along the SFS showcases different interaction styles between SFS and the basement structures. Different intersection angles between those two structural features create different deformation styles along the arc. An elongated rhomboidal pull-apart basin is expected where the segments of SFS are parallel or sub-parallel to the basement structures, while a more complex and irregular pull-apart basin is developed where the intersection angle is larger. The structural controls on volcanism along the arc are located along the basement structures, and demonstrate that they are only partially in tune with the SFS fault structures. Furthermore, the different deformation styles and interaction between volcanism-tectonism along the arc have been grouped into two different main tectono-volcanic domains, with distinctive transitional area around the Toba Caldera Complex.

A document by Pu Lin. Click on the document to view its contents.

The planetary boundary layer (PBL) is the main region for the exchange of matter, momentum and energy between land and atmosphere. The transport processes in the PBL determine the distribution of temperature, water vapour, wind speed and other physical quantities within the PBL and are very important for the simulation of the physical characteristics of the meteorology. Based on the two non-local closure PBL schemes (YSU, ACM2) and two local closure PBL schemes (MYJ, MYNN) in the Weather Research and Forecasting (WRF) model, seasonal and daily cycles of meteorological variables over the Yangtze River Delta (YRD) region are investigated. It is shown that all the four PBL schemes overestimate 10-m wind speed and 2-m temperature, while underestimate relative humidity. The MYJ scheme produces the largest biases on 10-m wind speed and the smallest biases on humidity, while the ACM2 scheme show WRF-simulated 2-m temperature and 10-m wind speed are closer to surface meteorological observations in summer. The ACM2 scheme performs well with daytime PBL height, the MYNN scheme performs the lowest mean bias of 0.04 km and the ACM2 scheme shows the highest correlation coefficient of 0.59 compared with observational data. It is found that there is a varying degree of sensitivity of the respective PBL in winter and summer and a best-performing PBL scheme should be chosen to predict various meteorological conditions under different seasons over a complicated region like the YRD.

Limited and declining water resources, increasing demand of water resources from different sectors has posed a major challenge for maintaining water sustainability and thus overall sustainability for a populous and water scarce country like India. Over extraction and changing climate have put additional pressure to maintain water sustainability. Therefore, there is a need of proper planning of utilization and management of water resource. Recently, virtual water trade has received much attention and become important tool for balancing the water budget. On the other hand, virtual water trade has become a threat that can adversely effects water balance of exporter's country as well as economy. Analysis of virtual water trade with its implications on water resources are missing, there is a need of such analysis that will help in management of water resources. We present a quantitative analysis of virtual water trade and its implications on water sustainability. We have considered rice crop only due to its characteristics as rice is major water consumer and water exporter crop of India

The present study objectively classify the convective cloud objects detected by the space-borne CloudSat radar over the Asian-Australian monsoon region using the hierarchical agglomerative clustering algorithm. Based on key properties representing the morphological features and convective intensity of the systems, five distinct convective cloud regimes are derived. The unique Coastal-Intense regime exhibits the most expansive horizontal scales (> 1000 km), high convective strength, the strongest cloud radiative effects, the highest probability of extreme rainfall, and a significant coupling with the sharp onset of the Asian summer monsoon circulation. Secondly, the Coastal regime illustrates smaller but also highly organized coastal convections, with the strongest convective strength. Less than 10% of the systems in the CI and Coastal regimes overlap with the tropical cyclones. The rest three regimes mark the less organized convection at various life cycle stages mainly over the land areas, with small seasonal variation in their occurrence.

Various recent studies have shown that basalt formations have the capacity for long-term secure CO2 storage through carbon mineralization. Many of these studies have demonstrated extremely rapid rates of mineralization, but the underlying mechanism enabling these elevated reaction rates, and their relation to the processes occurring in proposed basaltic reservoirs, remain poorly constrained. In this work, a 3D micro-continuum reactive transport model was designed to investigate the impact of alkalinity on basalt interactions with CO2-rich fluids. Reactive transport models were developed in PFLOTRAN based on 3D imaging data from high-temperature, high-pressure flow-through experiments (Luhmann et al. (2017) Chemical Geology, Water Resources Research). Mineral reactive surface areas in the model were adjusted to produce agreement with chemistry of output fluids sampled during the experiments. The benchmarked model showed that no considerable carbonate was formed during interaction with the relatively low alkalinity, low pH solutions, regardless of the enrichment of basalt-derived Na+, Mg2+, and Fe2+ ions in the reactant fluid. Increasing the alkalinity of the injected fluids consistently yielded higher rates of carbon mineralization. Similarly, introducing a small initial volume fraction of carbonate minerals into the system contributed to increased carbon mineralization, because of the increased fluid alkalinity. These results thus reinforce a conceptual understanding of carbonate mineralization in basalt-hosted CO2 storage reservoirs that emphasizes the importance of aquifer fluid alkalinity, and caution against extrapolating results from elevated-alkalinity CO2 storage reservoirs and experiments to others where this is less likely to be representative.

Brazil’s Amazon deforestation is one of the world’s great environmental problems, and the fate of the “TransPurus” region – the vast block of intact forest to the west of the Purus River in Brazil’s state of Amazonas – will be the deciding factor in maintaining Amazonia’s biogeochemical cycles and associated ecosystem services, including carbon storage and water cycling and biodiversity. The Purus River effectively divides Brazilian Amazonia between its eastern side (where the forest has been heavily affected by deforestation, fragmentation and degradation), and the western side (where the forest is largely intact due to lack of accessibility by road). This situation in western Amazonia is likely to change radically if the proposed AM-366 and associated roads are built, opening this block of forest with a connection to Highway BR-319 (Manaus-Porto Velho). The AM-366 would cross the Purus River at Tapauá and link BR-319 to Tefé, Coarí and Juruá. BR-319 is a highway that was-abandoned in 1988 but that has been “maintained” since 2015 while awaiting approval of a federal environmental impact assessment (EIA) before being “reconstructed.” Another threat comes from the “Solimões Sedimentary Basin” project that would open a substantial part of the TranPurus area to oil and gas drilling, potentially totaling thousands of wells. This would greatly increase the probability of roads being built to reduce the costs of servicing these wells. Roads are the primary drivers of deforestation in Brazil. The TransPurus area would be subject to invasion by actors ranging from landless farmers to large “land grabbers” (grileiros), and would be likely to attract oil palm and logging interests. Logging can potentially provoke large-scale forest degradation in conjunction with its increasing the vulnerability of forest to fire. Should the huge area of intact forest in this region be lost, potential release of greenhouse gases would be of a scale that could be a key factor in pushing global temperatures beyond a “tipping point” leading to global warming escaping from human control to begin a “runaway greenhouse” ending in a “hothouse Earth.” It would also threaten the source of water vapor for the “flying rivers” – winds that carry water vapor recycled through Amazonian trees to São Paulo and other parts of Brazil and neighboring countries.

The surface is the interface through which the bedrock interacts with the boundary-layer. Here, living organisms of various shapes, sizes, and function intermingle with the mineral soil, organic residue, and canopy air space that reside there. Together, they breath, absorb momentum, exchange water and gases, and bask in the heat from the sun and clouds above and thermal reservoirs below. While many of these functions are well understood, we knew less about how those functions operate and behave at different spatial and time scales. More intriguing, surface variance with scale influences scales of motion in the atmosphere. Here, I present a generalized look at how land and atmosphere scales interact, focusing on the lens of the surface energy budget. These processes are investigated through intensive measurements and high-resolution models conducted at the CHEESEHEAD19 field experiment in Wisconsin. A combination of airborne and tower eddy covariance networks, drone and airborne canopy imaging, and turbulence resolving simulations reveal persistent mesoscale contributions in the atmosphere enabled by surface heterogeneity.

Partially creeping faults exhibit complex behavior in terms of which parts of the fault slip seismically versus aseismically. The specific geometry of creeping versus locked fault patches may pose constraints on rupture lengths on partially-creeping faults. We use the 3D finite element method to conduct dynamic rupture simulations on simplified partially-creeping strike-slip faults, to determine whether coseismic rupture can propagate into creeping regions, and how the presence and distribution of creeping regions affects the ability of rupture to propagate across the whole fault. We implement rate-state friction, in which locked zones are represented by rate-weakening behavior and creeping zones are assigned rate-strengthening properties. We model two simplified geometries: a locked patch at the base of a creeping fault and a creeping patch at the surface of a locked fault. In the case of a locked patch within a creeping fault, rupture does not propagate far past the edges of the locked patch, regardless of its radius. The case of a creeping patch within a locked fault is more complicated. The width of the locked areas around the creeping patch determine whether rupture is able to propagate around the creeping patch. Although rupture is always able to propagate at least a small distance into the creeping patch, if the width of the locked zone between the edge of the creeping patch and the end of the fault is too narrow, rupture stops. This simplified parameter study may be useful for understanding first-order behaviors of real-world partially-creeping strike-slip faults.

Simple models of fluid and solid mechanics predict that the depressurization of a shallow reservoir that occurs during large effusive eruptions produces exponential trends in time series of both pressure drop and extruded volume. These models are attractive due to their simplicity and because they can explain geodetic and extruded volume data recorded at several volcanoes like at St. Helens and Cordón Caulle, regardless of their magma compositions. However, several lava and dome-forming eruptions like at Redoubt, Hekla and Santiaguito volcanoes do not show clear ground deformation coeval to lava and dome effusion despite the extrusion of at least 0.1 km3 DRE of magma. This apparent paradox can be explained by a variety of factors including deep magma sources and highly compressible magmas that leave no geodetic footprint. Here we explore the role of magma buoyancy with a reanalysis of ALOS-1, TerraSAR-X and RADARSAT-2 InSAR ground deformation and Pleiades DEM data of the VEI 5 Plinian and dome forming rhyolitic eruption of Chaitén volcano in 2008-2009. We show that almost all of the recorded ground deformation occurred during the first three weeks of the eruption, which implies that the extrusion of a rhyolitic dome (~0.8 km3 DRE) did not result in significant depressurization of a magma reservoir, despite the clear exponential trends in the extrusion data. Instead, we show that the exponential trend in the time series of extruded volume can be explained by magma ascending due its buoyancy instead of its overpressure. These results imply that ground deformation alone is not always indicative of the temporal evolution of an eruption and urges for the acquisition of denser time series of DEM data to calculate time-lapse extrusion rates.

Airborne electromagnetic (AEM) data can be inverted to recover models of the electrical resistivity of the subsurface; these, in turn, can be transformed to obtain models of sediment type. AEM data were acquired in Butte and Glenn Counties, California, U.S.A. to improve the understanding of the aquifer system. Around 800 line-kilometers of high-quality data were acquired, imaging to a depth of ~300 m. We developed a workflow designed to obtain, from the AEM data, information about the large-scale structure and heterogeneity of the aquifer system to better understand the vertical connectivity. Using six different forms of inversion and posterior sampling of the recovered resistivity models, we produced 6006 resistivity models. These models were transformed to models of sediment type and estimates of percentage of sand/gravel. Exploring the model space, containing the resistivity models and the derived models, allowed us to delineate the large-scale structure of the aquifer system in a way that captures and communicates the uncertainty in the identified sediment type. The uncertainty increased, as expected, with depth, but also served to indicate, as areas of high uncertainty in sediment type, the location of both large-scale and small-scale interfaces between sediment type. A plan view map of the integrated percentage of sand/gravel, when compared to existing hydrographs, revealed the extent of lateral changes in vertical connectivity within the aquifer system throughout the study area.

Structural and lithological controls in mountain valleys have been shown to affect the erosional connectivity of hillslopes, tributaries and alluvial fans, as well as the formation and preservation of strath terraces. In this study we explore the synchronicity of fluvial bedload aggradation and bedrock incision in valleys of one river draining a collisional mountain belt through geomorphological, sedimentological and chronological datasets of strath terraces. Along the M’Goun River on the southern flank of the central High Atlas Mountains strath surfaces and bedload sediments are preserved in valleys with differing structure and lithology throughout the thrust front and wedge-top basin. We (1) extract terrace surface and river channel elevations from a digital elevation model and field mapping to reconstruct river long profiles; (2) collect grain size and lithology data from terraces to derive information on sediment source and transport; (3) constrain the timing of bedload aggradation within the two latest strath levels using a new approach to OSL dose rate correction of gravels. Strath terraces form in weak sedimentary bedrock in valleys confined by limestone and conglomerate units, and are capped by up to 3 to 10 m of gravel bedload and overbank sands. The record of strath burial and incision extends to 180 ka, but only includes one synchronous bedload aggradation event during the last interglacial maximum MIS 5a (~130-110 ka). Reconstructed paleo-river long profiles and chronology demonstrate time-transgressive bedrock incision through the thrust front and wedge-top basin on the order of 10^4 – 10^5 yrs, representing strath incision of 12 to 40 m. A lack of a downstream bedload grain-size trend and presence of locally derived clast lithologies indicate lateral input of gravel from valleys in addition to downstream transport. These results allow for the development of a conceptual model of asynchronous strath terrace formation in a collisional mountain belt.

We present a data-driven approach to clustering or grouping Global Navigation Satellite System (GNSS) stations according to their observed velocities, displacements or other selected characteristics. Clustering GNSS stations has the potential for identifying useful scientific information, and is a necessary initial step in other analysis, such as detecting aseismic transient signals (Granat et. al., 2013). Desired features of the data can be selected for clustering, including some subset of displacement or velocity components, uncertainty estimates, station location, and other relevant information. Based on those selections, the clustering procedure autonomously groups the GNSS stations according to a selected clustering method. We have implemented this approach as a Python application, allowing us to draw upon the full range of open source clustering methods available in Python’s scikit-learn package (Pedregosa et. al., 2011). The application returns the stations labeled by group as a table and color coded KML file and is designed to work with the GNSS information available from GeoGateway (Heflin et. al., 2020; Donnellan et al, 2021) but is easily extensible. We focused on California and western Nevada. The results show partitions that follow faults or geologic boundaries, including for recent large earthquakes and post-seismic motion. The San Andreas fault system is most prominent, reflecting Pacific-North American plate boundary motion. Deformation reflected as class boundaries is distributed north and south of the central California creeping section. For most models the southernmost San Andreas fault connects with the Eastern California Shear Zone (ECSZ) rather than continuing through the San Gorgonio Pass.

The effects of climate on eroding landscapes and the delivery of sediment from these remain poorly understood. The sampling and dating of river terraces provide one way to address this question, because these embed information about the interconnected dynamics of mountain valley widening, river incision, sediment delivery, and their sensitivity to external forcing. We developed a new approach to OSL dose rate correction of gravels to derive the most detailed chronology of river terrace stratigraphy in NW Africa to date. We sampled river terraces 10-20 m above the modern river plain for dating in a 1200 km2 river catchment, the River M’Goun, eroding the High Atlas Mountains hinterland of the continental river Draa. We applied OSL and IRSL dating to determine the age of 23 samples, using Bayesian methods to derive a robust chronology. We show terrace strath planation starts at ~180 ka in the MIS 6 glacial maximum, followed by aggradation from 140 – 57 ka in MIS 5 to MIS 4 which deposited the up to 10 m stratigraphy of fluvial conglomerate (imbricated rounded cobbles). Incision and abandonment of river terraces occur in MIS 3 to 2 during the transition to the last glacial maximum. Our results compared with an Atlantic record of aridity in the Northern Sahara over the last 120 ka show that aggradation and valley widening occur in response to periods of northward penetration of the African summer monsoon into the High Atlas. We note that these signals persist across the different tectonic zones, from the fold and thrust belts into the sedimentary basins. More widely, our data demonstrate how changes in monsoon patterns can cause changes in the erosion of mountains and transport of sediment in arid continental interiors and these form new inputs for numerical landscape evolution models.

Surface melting can alter ice sheet sliding by supplying water to the bed, but subglacial processes driving ice accelerations are complex. We examine linkages between surface runoff, transient subglacial water storage, and short-term ice motion from 168 consecutive hourly measurements of meltwater discharge (i.e. moulin input) and GPS-derived ice surface motion for Rio Behar, a ~60 km2 moulin-terminating supraglacial river catchment the southwest Greenland ablation zone. Short-term accelerations in ice speed correlate strongly with lag-corrected measures of surface mass loss, specifically supraglacial river discharge (r= 0.9; p<0.001). Though our 7-day record cannot address seasonal-scale forcing, diurnal ice accelerations align with normalized differenced supraglacial and proglacial discharge, a proxy for subglacial storage change, better than GPS-derived ice surface uplift. These observations counter theoretical steady-state basal sliding laws and suggest that moulin- and proglacially induced fluctuations in subglacial water storage, rather than absolute subglacial water storage, drive short-term ice accelerations.

Quantitatively assessing the abundance of the composite minerals of terrestrial granite is crucial for understanding the evolutionary history of the Earth’s crust and for mineral exploration. Prevalent methods based on the Hapke model to estimate mineral abundance by setting the optical constants of endmembers ahead are no longer applicable to terrestrial granite because of the complexity of natural granite, which will lead to remarkable uncertainties in estimations. In this study, we retrieved such specific photometric parameters from the bidirectional reflectance spectra measured at a range of incidence, emergence, and phase angles before they were inputted to the Hapke model to estimate mineral abundance. Four different kinds of granite samples of main rock-forming minerals (quartz, alkali feldspar, and plagioclase) comprising the bulk of granite were used to test the effectiveness of our proposed method. The effects of particle size and dark minerals on the inversion results using the visible near and shortwave infrared (VNIR-SWIR) wavelengths were also examined. The results show that using the photometric parameters retrieved from multiangle measurements as inputs for the Hapke model accurately estimated the abundances of quartz, alkali feldspar, and plagioclase for both natural and synthetic granite samples. Furthermore, the results also prove that the retrieved particle sizes of particulate samples are all within their measured ranges. These results indicate that the proposed approach provides a more accurate and efficient estimation of the compositions of terrestrial granite and is feasible for quickly assessing the abundance of minerals contained in granite.