Journals
2026 EN
Dean Amy E. · Banham Steven G. · Paar Gerhard
+3 more
Abstract Sedimentary texture, facies, and architecture can be used to reconstruct the palaeoenvironment under which sediments accumulate. On Mars, palaeoenvironmental reconstructions are used to understand ancient Martian atmospheric circulation, surface sedimentary processes, and the presence of water, to provide insight into ancient habitability and climate evolution. Exploration of the Stimson formation at the Naukluft plateau, Gale crater, by the MSL rover Curiosity yielded evidence of aeolian dunes recorded within the strata, and that the Stimson formation unconformably overlies the older, lacustrine Murray formation. Analysis of the strata revealed a hierarchy of bounding surfaces forming compound cross‐bedding, indicating two scales of bedform: primary dunes (draa) and superimposed dunes. Cross‐set dip‐azimuths indicate a broad sediment transport direction toward the north, aligning with the north or north‐east transport direction of previous work. Paired with textural analysis, the outcrops of the Naukluft plateau are interpreted to have formed within the central section of a large, dry aeolian dune field. The formation of concretions, veins and alteration halos, formed by diagenesis or fracturing associated with sub‐surface fluids, coincide with the lithification of the Stimson formation. This hints toward an extended presence of water within Gale crater but at a much lower abundance than earlier during the crater fill sequence. The unconformity denotes a large climatic transition from the lacustrine Murray formation to dry aeolian Stimson formation, reflecting long‐term drying of the ancient environment. Such observations enhance the understanding of the ancient Martian environment, allowing reconstructions of atmospheric conditions, climate and habitability on a regional scale.
Journals
2026 EN
Schoenfeld Ashley M. · Vance Steven D. · Lopes Rosaly M. C.
+2 more
Abstract Surface observations of Saturn's moon Titan revealed features characterized as dissected, elevated plateaus with high valley density known as labyrinth terrains. Of this terrain class, a subtype referred to as radial labyrinth is described as dome‐shaped uplifts with radial channel patterns. Uplift of these radial labyrinths has previously been explained as cryomagmatic intrusions at the brittle–ductile transition zone. Here we propose an alternative hypothesis that crustal heterogeneities in Titan's upper clathrate crust introduce density differentials due to ethane‐methane substitution, as ethane‐rich liquids percolate into methane clathrate, inducing solid state flow and generating domal topography. This mechanism is analogous to salt tectonics on Earth and has similarly been evoked for dome formation on the dwarf planet Ceres. We show that the elevation and width of the observed radial labyrinths are consistent with domal uplift driven by a hydraulic head within the uppermost portion of Titan's crust, given a plausible set of elastic parameters for clathrate hydrates. Additionally, the insulating effect of clathrate, combined with partial mixing with water‐ice, allows for sufficiently low viscosity for geologic flow on a relevant timescale: uplift of the domes could have occurred within the last billion years.
Journals
2026 EN
Barnes Robert · Gupta Sanjeev · Treiman Allan
+25 more
Abstract The JPL rover Perseverance's investigations of Jezero crater's floor reveal that the ultramafic Séítah formation and the overlying mafic Máaz formation are deformed into a broad, low‐amplitude structural dome. Mastcam‐Z stereo images processed into digital outcrop models, together with RIMFAX ground‐penetrating radar profiles, were used to reconstruct the three‐dimensional stratal geometry of both units along a SW–NE transect across a southern domain of the dome called south Séítah. Measurements from 3‐D reconstructions show a progression from sub‐horizontal layers in the central parts of the dome to dips <20° away from the dome on its flanks, with Máaz and underlying Séítah layers dipping concordantly. RIMFAX profiles and imaging around the dome confirm that limb dips are continuous into the subsurface and form a flat‐crested composite quaquaversal fold structure. Séítah rocks in the fold core are up to 17 m higher than adjacent Máaz lava flows, despite stratigraphically underlying them, a relationship attributed to structural uplift. Fold geometry, wavelength (∼1 km), and amplitude (∼30–50 m), match models of forced folding produced by inflation of shallow igneous intrusions. The most likely cause is the emplacement of a sill or laccolith beneath the crater floor, generating elastic bending of the overlying layers. This intrusion‐driven uplift explains Séítah's elevated position, constrains the deformation history of Jezero's crater floor units post‐emplacement of the Séítah and Máaz formations, and supports a significant role for shallow magmatic intrusion in shaping intracrustal structures on Mars.
Journals
2026 EN
Bemis Sean P. · Holbrook W. Steven · Flinchum Brady
+5 more
Abstract Most of Earth's present‐day terrestrial surface is covered by regolith—the layers of soil, saprolite, and weathered bedrock that together comprise the critical zone. Recent research has focused on understanding fluxes of minerals, water, and energy through the critical zone under steady state assumptions. However, in eroding landscapes, regolith and soil are produced from the bedrock as it is exhumed. Therefore, at some point in time, every location on the Earth's surface currently mantled by regolith experienced an onset of weathering processes. This initial creation of a critical zone from rock is poorly understood. Here we study initial critical zone formation from exposed bedrock by combining surface and subsurface geophysical observations at a site where regolith appears to be forming from bedrock on a granodiorite outcrop in Panola Mountain State Park, Georgia, USA. Vegetation gains an initial foothold on the outcrop by colonizing microtopographic depressions created by differential weathering of contrasting bedrock compositions. We observe a range of colonization stages, from moss to grasses to small bushes and eventually to large trees. Subsurface signatures of the vegetation include enhanced radar reflectance and reduced seismic velocities, with larger vegetation associated with stronger subsurface signals. Using a space‐for‐time substitution approach, we propose an evolutionary sequence for critical zone development. While disentangling the chicken‐and‐egg questions that pervade this topic remains challenging, our results suggest that geological heterogeneity can provide the initial catalyst for colonization, but ultimately vegetation itself plays a strong role in producing subsurface structures associated with the critical zone.
Journals
2026 EN
Zhao Jingjing · Wu Libin · Nie Yaguang
+5 more
Abstract Antarctica's sensitivity to climate warming expands ice‐free terrestrial environments, where lakes act as key reservoirs of organic carbon (OC). Penguins deliver nutrients from marine to terrestrial environments, which can in turn boost lake productivity near penguin colonies. However, the mechanisms by which penguin guano inputs impact sedimentary dissolved organic matter (DOM) remain unclear. Here, we analyzed three types of sediment cores (microbial mats, ornithogenic, and mixed sediments) from ice‐free areas of the Ross Sea region in East Antarctica. Combining ultraviolet‐visible spectroscopy, excitation‐emission‐matrix spectra, and pyrolysis gas chromatography‐mass spectrometry, we characterized water‐extractable DOM composition and assessed its potential for OC release. Results show that the ratios of Antarctic sedimentary dissolved organic carbon to total organic carbon (DOC:TOC) exceed those in most cold regions globally. Ornithogenic sediments exhibit the highest DOC:TOC ratio (12%), significantly higher than microbial mat sediments (7%), indicating that penguin guano contributes highly soluble organic matter to sediments—a process driven by differences in carbon‐nitrogen composition between solid phase and DOM. DOM from aquatic microbial mats presents low‐molecular‐weight and primarily consists of tryptophan‐like compounds (54%), whereas the solid‐phase components are predominantly lipids. Guano inputs contribute substantial nitrogen‐containing compounds, forming a relatively high‐molecular‐weight DOM pool with humic‐like properties and high aromaticity. Additionally, ultraviolet parameters and fluorescence indices can be used as novel proxies for reconstructing penguin activity and primary productivity. This study demonstrates that guano rapidly dissolves from sediment into water, providing key scientific evidence for evaluating the organic matter‐biological activity‐climate feedback mechanism under global change.
Journals
2026 EN
Jia Mengqi · Peng Bin · Guan Kaiyu
+13 more
Abstract Agrivoltaics, combining agriculture with photovoltaic systems, offers a promising solution to address land‐use conflict between food and energy production. However, the complexities of agrivoltaics and its effects on the water‐energy‐carbon interactions remain poorly understood. In this study, we developed a process‐based agrivoltaic model within the Community Land model 5 to assess the impacts of agrivoltaics on water, energy, and carbon cycles. The model was validated using data from agrivoltaic sites in Illinois and Colorado, generally capturing spatiotemporal variations in light conditions, soil moisture, and biomass carbon. Simulation results suggest that agrivoltaics significantly impact water, energy, and carbon budgets at the patch and system levels for maize and soybean in Illinois and grass in Colorado (2000–2014). Our findings show that the impacts of agrivoltaics vary by climate conditions and plant types. In dry climates, rainfall redistribution and shading from agrivoltaics conserve soil moisture and enhance evapotranspiration, promoting greater carbon assimilation and soil carbon storage for C 3 grass. Conversely, in wetter regions, reduced solar radiation from shading becomes the dominant factor, lowering carbon assimilation and sequestration for maize and soybean. These results suggest that agrivoltaics can help mitigate drought impacts in arid environments. Our analysis of land equivalent ratios across different photovoltaic ground coverage ratios (PV GCR) shows that a medium PV GCR (60%) under “AgPV” deployment, where PV and plants share the same land, maximizes land‐use efficiency at the study sites. Our modeling study supports informed decision‐making to promote sustainable management of water, energy, and food resources amid environmental change.
Journals
2026 EN
Fassnacht Steven R. · LópezMoreno Juan Ignacio · Barnard David M.
+8 more
Abstract The correlation of earth system properties is important for assessing monitoring strategies, determining scales of modeling, and improving forecasting capabilities. We present a new method to examine the spatial scale of inter‐annual patterns from time series data. The variability in annual patterns between stations is computed using daily data from a network of stations. This variability is used to compute the semi‐variance for intervals of distance and plotted in the form of a variogram. Variograms are used to identify the correlation distances for a specific process. Here, the method is applied to 90 stations of daily snow water equivalent accumulation and precipitation data over the Southern Rocky Mountains of the Western USA for a 40‐year period (1981–2020). At 5‐, 10‐, or 20‐km lag distances, snow accumulation patterns are very similar to 90 or 100 km. Snow accumulation patterns are less correlated up to about 380 km; beyond there is no quantifiable spatial correlation. Summer precipitation patterns are correlated up to about 60 km while winter precipitation patterns are spatially consistent for 100 km and likely to more than 300 km. Subsets of the accumulation and precipitation data to explore differences due to geographic location, land cover type, and the Oceanic Niño Index yielded similar results.
Journals
2026 EN
Sun Ge · Bian Zihao · Khand Kul
+9 more
Abstract Urban forests and other green infrastructures have been viewed as part of the “Nature‐based Solutions” (NbS) to mitigate emerging urban environmental change. This study focuses on the role of evapotranspiration (ET) in regulating water balances of small watersheds in the eastern United States. We compared streamflow and ET patterns at daily, monthly and annual scales and linked these hydrological variables to the physical properties of 11 paired watersheds dominated by forests (FW) or urban (UW) land covers. The annual precipitation ranged from 1028 mm to 1683 mm and potential ET (PET) from 815 mm to 1450 mm. The mean annual flow/precipitation (Q/P) ratios were 0.26 ± 0.13 and 0.41 ± 0.1 for FW and UW, respectively. Overall, UW had lower annual ET (772 mm in UW vs. 947 mm in FW), but higher mean annual and (∼58% higher), monthly water yield (17%–186% higher), and peakflow rates (up to 100 times higher) than FW. The streamflow differences between FW and UW were most pronounced during the growing season and early winter (June‐November). The mean Q/P ratios for 30 large hurricane events (2016–2021) were 0.12 ± 0.11 and 0.38 ± 0.23 for FW and UW, respectively. The flow rates in the dormant season (around December‐May) in UW were similar or lower than FW. We developed conceptual models to explain the seasonal and storm event streamflow differences using background climate (PET), ET, and land surface characteristics. Urban NbS designs should factor in strategies that maximize ET while minimizing impervious surfaces enhancing watershed “sponge” and “pump” functions.
Journals
2026 EN
Park YoungJin · Hwang HyounTae · Tanaka Tatsuya
+5 more
Abstract Seepage boundary conditions are commonly used in groundwater simulations to allow groundwater to discharge at the upper surface of the model when groundwater head exceeds atmospheric pressure. However, the extent and transient behavior of the seepage zone are often unknown a priori and difficult to predict. The standard mathematical representation of seepage boundaries defines head as equivalent to elevation only when groundwater pressure exceeds atmospheric pressure, which is a mixed conditional Dirichlet and Neumann boundary condition. While this representation has been widely implemented in groundwater models, it is rarely noted that convergence is guaranteed only when both the efflux and zero‐pressure conditions are simultaneously satisfied, often requiring unnecessarily small timestep sizes, resulting in low computational efficiency. This study presents a continuous‐differentiable seepage face (CDSF) equation that replaces the conventional mixed boundary condition (or traditional seepage face, TSF) with a head‐dependent Robin boundary condition, improving numerical stability and computational performance. It is a refined adaptation of an existing seepage boundary condition approach previously used in integrated surface‐subsurface hydrologic models, specifically optimized for saturated flow simulations. Through a series of verification models, we demonstrate that the refined method provides robust and efficient solutions for seepage boundary conditions in saturated flow models. The results suggest that this CDSF approach improves accuracy and computational performance compared to TSF methods, offering a more stable alternative for groundwater modeling. These findings contribute to the advancement of subsurface hydrology by providing a practical framework for handling seepage boundary conditions in groundwater simulations.
Journals
2026 EN
Rochford Louisa M. · Bulovic Nevenka · Flook Steven
+2 more
Abstract Sustainable management of groundwater resources requires a comprehensive understanding of the groundwater system and its water balance, including groundwater extraction. Bores (otherwise known as wells) used for cattle grazing are not typically metered and extraction is usually estimated using analytical models based on supply and demand‐based factors. A world‐first program of metering of 36 bores on 24 beef cattle grazing properties and landholder interviews on factors affecting water use was undertaken in semi‐arid southern Queensland, Australia, over a 6‐year period. This study investigated whether data from this program could be used to develop empirical models that could improve estimates of groundwater extraction. A model to predict cattle numbers was initially developed. The outputs from this model, together with public domain spatial data sets, were then used to predict groundwater extraction using a generalized linear model. Modeled property groundwater extraction ranged from 0.31 to 25.5 ML a −1 and was 7.6 ML a −1 on average. The model explained 83.3% of the variance in metered extraction and was found to be more accurate for the metered properties than models previously applied. The study demonstrates that models developed using data for a representative subset of users can be an effective means of estimating groundwater extraction. The approach could be applied across a range of hydrological environments and agricultural settings globally to improve estimation of unmetered take.