Earth and Environmental Sciences

Runoff prediction in ungauged basins remains a fundamental challenge due to the absence of discharge observations and the limited transferability of data-driven models across heterogeneous hydrological conditions. This study proposes a regime-aware framework that models hydrological processes from the perspective of shared driver-induced regimes. Instead of relying on runoff observations, a view-based contrastive self-supervised learning strategy is employed to extract transferable features from hydrometeorological drivers. Specifically, augmented temporal-window views generated through temporal masking and feature perturbation are contrasted to learn runoff-independent representations, enabling the identification of cross-basin hydrological regimes via unsupervised clustering. Regime-specific prediction models are then constructed and adaptively combined for target basins based on regime similarity. Experimental results show that the proposed method achieves a median Nash-Sutcliffe efficiency of 0.5 across ungauged test basins, demonstrating improved prediction performance under ungauged conditions. These findings highlight the effectiveness of learning shared hydrological regimes from driver space and provide a new perspective for robust runoff prediction in ungauged basins.

Abstract Global surface ozone (O 3 ), intensified by climate change, poses increasing health and ecosystem threats. Despite stringent air policies, China’s persistent O 3 pollution exemplifies a global challenge intertwined with climate actions reshaping emission pathways. Optimal mitigation remains contentious, primarily due to inconsistent conclusions regarding the sensitivity of summer regional O 3 formation. Here we show the path dependency in O 3 mitigation strategies for synergistic clean air and climate action goal achievement over multidecade scales. This path dependence is validated by observed concurrent plateaus (2020-2023) in deweathered O 3 concentrations and sensitivity trends across Chinese megacity clusters. Leveraging this understanding of path dependency, we quantitatively reveal that the optimal future strategy involves prioritizing early volatile organic compound reductions, as their high effectiveness for regional O 3 mitigation gradually diminishes towards 2050. This challenges prevailing nitrogen oxides priority paradigms. Our work reframes O 3 control, providing a paradigm for resilient air quality-climate governance.

Small-scale turbulent mixing in the ocean interior is vital in governing ocean circulation and tracer distributions, and hence global climate. However, the planetary extent of this role and its dependence on the microphysics of mixing remain inadequately understood. Here, we emphasize the variety of spatio-temporal scales on which such interior turbulent mixing can shape the climate system. In addition to its well-established role in facilitating the equilibration of deep branches of ocean circulation on centennial-to-millennial timescales, interior turbulent mixing is a leading determinant of oceanic tracer budgets on timescales as short as sub-annual. We highlight the importance of the co-dependence of vertical (diapycnal) mixing and lateral (isopycnal) stirring in establishing the large-scale impacts of oceanic turbulence. We conclude with a summary of theoretical, observational and computational bottlenecks in the way of a sufficiently accurate representation of mixing in Earth System Models, and discuss emerging opportunities for making progress in these areas.

Sand dunes develop when there is a source of sediment and adequate wind. Dune morphology and occurrence can then be used to infer sediment source distribution and formative climate conditions. This is useful where direct climate observation is challenging on Earth, other planets, and the past. However, there has been no complete and accurate digital map of the occurrence of Earth’s sand dunes with distinguishable morphologies. Here we present that map and demonstrate that in arid environments dune presence is mostly explained by convergent transport and source proximity, whereas in wetter climates wind strength is an additional constraint. By limiting analysis to dunes identified from globally available imagery and topographic data, we produce a consistent dataset useful for inferring myriad aspects of geology and climate, and improving understanding of aeolian landscapes. We provide an example, using barchan dune orientations, to demonstrate a trade-off between inference of sediment and wind characteristics. A global dune map, combined with climate and geologic data, reveals how sediment availability, wind-driven transport, and flux convergence control dune formation, enabling improved prediction of dunes across past and future climates.

This study examines the long-term surface temperature variability across Jammu and Kashmir using ground-based observations and reanalysis data during 1980–2024. The region shows a clear but spatially heterogeneous warming, with the strongest annual mean temperature (T mean ) rise at mid-elevation stations such as Bhaderwah (+ 0.3 °C/dec) and weak or insignificant trends at lower elevations like Jammu (about − 0.1 °C/dec). Minimum temperature (T min ) shows the most rapid acceleration, by + 0.1 to 0.5 °C/dec at several mid-to-high elevation regions, whereas daytime maximum temperature (T max ) trends remain modest (about 0–0.2 °C/dec). These spatial and seasonal contrasts, along with enhanced warming at higher altitudes in specific seasons (e.g., pre-monsoon T min up to + 0.6 °C/dec), indicate the presence of elevation-dependent warming (EDW) in these mountainous regions. The annual T mean increases by 0.18 °C/km/dec and winter T max shows the strongest altitude dependence of 0.43 °C/km/dec, whereas T min exhibits no significant EDW across seasons. Multiple linear regression analysis suggests that wintertime altitude-dependent temperature trends are statistically associated with albedo-related surface processes, whereas the annual and seasonal increases in Tmin are more closely associated with atmospheric moisture and longwave radiative conditions. Overall, the region has warmed by up to nearly 1 °C in last two decades at several high-altitude locations (e.g., Pahalgam and Gulmarg), highlighting the sensitivity of the Himalayan environment to ongoing climate change with severe implications for high-altitude hydrology, cryosphere stability, and regional climate resilience.

The albic horizon is a bleached diagnostic layer formed through combined processes of iron-manganese leaching and clay illuviation. Its thickness and burial depth collectively determine the critical role in impeding water movement and restricting root extension. However, understandings of the spatial variation of the albic horizon remain limited. Traditional understandings primarily rely on extensive field surveys combined with geostatistical methods. To expand such understandings on a broader geographical area, we developed a digital soil mapping (DSM) framework to predict the thickness and burial depth of the albic horizon. We integrated 111 soil profile points containing albic horizons with a rich set of environmental covariates to construct reliable prediction models. Following the feature selection process of recursive feature elimination (RFE), a quantile regression forest (QRF) model was employed for spatial prediction, cross-validation, and uncertainty estimation. The results from 50 repetitions of 10-fold cross-validation demonstrated robust model performance, with R² of 0.38 and 0.29 for thickness and burial depth, respectively, and RMSE% accounting for 34% and 38% of their mean values. The prediction interval coverage percentage (PICP) indicated that approximately 86.9% and 90.6% of the validation samples for thickness and burial depth, respectively, fell within the predefined 90% prediction interval (PI), affirming the reliability of uncertainty estimation. The relative variable importance indicated that climate factors were the dominant determinants in predicting both albic horizon thickness and burial depth, highlighting the necessity of incorporating climate data in the spatial modeling of albic soils. The prediction maps indicated a general decreasing trend in both the thickness and burial depth from northeast to south across the study area. Large prediction uncertainty mainly occurred in areas where soil survey points were lacking, highlighting the need for targeted supplementary surveys. Our findings offer valuable references for other similar large-scale mapping of soil layer thickness (or depth) in plain agricultural regions.

The Dyrfjöll ridge represents the remnant of the filling of a Neogene volcanic caldera. The volcanic succession consists of a basal ignimbrite overlain by basaltic hyaloclastites and capped by basaltic lavas. The ridge is truncated by the Dyr Pass (856 m a.s.l.), which formed when a major rock avalanche (RA), composed of hyaloclastites and lava blocks, collapsed from both flanks of the ridge. On the eastern side, the RA partly overrode the Dyrajökull glacier along the Jökuldalur valley. About 4 km downstream at the valley outlet, a well-preserved RA deposit remains, characterized by hummocky mounds of lava and hyaloclastite megablocks. Between this deposit and the present-day glacier fronts, six push-moraine complex ridges are preserved. The aim of this study is to establish the chronology of these glacier stages in Jökuldalur and to distinguish their different origins. To constrain the timing of deposition, 20 boulders were sampled for 36 Cl cosmogenic exposure dating from both the RA deposit and the moraine ridges. The main RA yielded an exposure age of 9.4 ± 1.1 ka. The four outermost glacial stages, represented mainly by hummocky moraine assemblages, yield ages ranging from 8.8 ± 0.9 to 6.2 ± 0.7 ka. The ages of the moraines are coeval with the Holocene Thermal Maximum, a period during which most Icelandic glaciers experienced substantial retreat or complete disappearance. The results emphasise the insulating effect of debris following RA emplacement, which appears to have promoted subsequent glacier re-advance despite prevailing peak Holocene warmth. Stage 5 yields an age of 4.0 ± 0.5 ka and is likely associated with a distinct RA event, whereas Stage 6 is younger than 0.13 ka.

Accurate characterization of heavy petroleum fractions remains challenging in hydroprocessing reactor modeling, where reliable hydrogen-solubility estimates in complex hydrocarbon mixtures are essential. Continuous thermodynamics has been successfully applied to represent crude oils and petroleum fractions in vapour-liquid equilibrium calculations through continuous composition distributions. Building on this framework, we propose a continuous-thermodynamics-based characterization methodology for vacuum gas oils and integrate it with the Augmented Grayson-Streed (AGS) approach to predict hydrogen solubility. Over temperature and pressure ranges of 459-653 K and 1.0-12.5 MPa, respectively, the proposed strategy reduces the global average absolute deviation with respect to experimental data from 22.5% to 11%. Beyond improving accuracy, the framework provides a systematic route to define a minimal set of pseudocomponents, reducing arbitrariness in heavy-fraction characterization while relying only on routinely measured laboratory data.

Fossils of the Ediacara Biota preserve the oldest macroscopic communities that include animals. Classification of many of these taxa has proved contentious. Instead, studies of ecological characters reveal key insights. Here we examine the Ediacaran fossil Spriggina floundersi from the Ediacara Member, Flinders Ranges and surrounding region. Specimens from Nilpena Ediacara National Park (NENP) and the South Australia Museum (SAM) present significant morphological variation. Fossils found in situ on discrete bedding planes at NENP reveal no systematic orientation of features, suggesting variable morphologies formed via biological processes, rather than external forces. Our results support motility in Spriggina, which involved bending about the long axis, propagation of pedal waves, vertical adjustment of the anterior region and horizontal manipulation of repeated body units. A significant number of fossil specimens are bent to the left (right in life). The nature of these bends does not match expectations of anatomical asymmetry and instead constitutes the oldest described evidence of behavioural handedness. Results are consistent with Spriggina as a bilaterally symmetrical, possibly segmented, benthic organism. These characters are unique compared with known Ediacaran ecologies but are common in various extant bilaterian groups, indicating major animal innovations prior to the Phanerozoic.

This research provides novel insights into the diversity of DNA extracted from samples collected from the Turin Shroud in 1978, revealing its biological complexity through rigorous DNA and metagenomic analyses. Our findings highlight its preservation conditions and environmental interactions, offering valuable perspectives into the identified genetic variants, which originated from multiple biological sources. We identified several human mitochondrial DNA (mtDNA) lineages, including K1a1b1a, which matches the 1978 official collector's mitogenome, H2a2 (i.e., the lineage of the mtDNA reference sequence rCRS), H1b, which is common in Western Eurasia, and the rare H33, which is also present in the Near East. Additionally, the reconstructed microbiome of the Shroud reveals a rich tapestry of multiple microbes commonly found on the human epidermis, as well as archaeal communities adapted to high salinity and fungi including molds. These findings are consistent with the preservation conditions experienced by the Shroud over the centuries. The presence of abundant Mediterranean endemic red coral, various cultivated plants (e.g., carrot, wheat, corn, bananas, and peanuts) and domesticated animals (e.g., cattle, pigs, chickens, dogs, and cats) provide a fascinating glimpse into the diverse biological sources of the contaminants that have accumulated on the Turin Shroud over time. Finally, radiocarbon dating of two distinct threads collected from the reliquary is consistent with their use in repair interventions of the Shroud carried out in 1534 and 1694 CE.

In the version of this article initially published, there was an error in the units listed in the Fig. 1b x -axis label, where in the text now reading “Age (Ma),” “Ma” originally appeared as “Ga.” The figure is now updated in the HTML and PDF versions of the article.

In the version of this article initially published, there was a layout error in Table 2 where the “Generation Time (d)” header was misaligned and did not cover the six right-hand columns from “Median” through “Maximum.” The table has been corrected in the HTML and PDF versions of the article.

As anthropogenic forcing intensifies, soil moisture droughts have become prevalent across many regions. Soil moisture anomalies can influence near-surface air temperature by modulating both energy and carbon fluxes. However, the annual temperature response to soil moisture anomalies in the year following a soil moisture drought remains unclear. Here, we show that annual soil water loss in the year after soil moisture droughts induces a larger annual warming effect than the annual cooling from an equivalent water gain. This asymmetric response arises only when the effects of anthropogenic greenhouse gas forcing are included, where vegetation is more strongly suppressed after soil moisture drought than enhanced after soil moisture gaining, contributing to reduced transpiration and carbon uptake that collectively amplify warming. More than 60% of global land areas exhibit the asymmetry. Our findings suggest that past climate extremes may accelerate future warming by impairing vegetation's capacity to regulate biophysical and biogeochemical processes.

Grid expansion remains a key strategy for increasing electricity access across Sub-Saharan Africa (SSA). However, whether utilities can generate sufficient revenue under current tariffs to support capital investment is unclear. We compile a comprehensive dataset of residential electricity tariffs for 48 SSA countries and develop a standardized model to estimate electricity bills using the Multi-Tier Framework (MTF). Affordability is assessed across income percentiles using simulated income distributions. Under current tariffs, around 608 million people (50%) may not afford Tier 4 electricity, rising to 1.05 billion (85%) for Tier 5 under a 10% energy-poverty threshold. Sensitivity analyses using 5% and 15% thresholds confirm the robustness of these findings. Even where higher-tier electricity is affordable, usage remains low. Combining affordability estimates with utility financial performance, we identify where grid expansion could be viable and where affordability constraints and utility deficits can create electrification traps. In many countries, off-grid solutions may be the only feasible pathway to achieving SDG7.

The relative retention of nitrogen (N) and phosphorus (P) in lakes and their roles in nutrient cycling remain debated. Although the United States has implemented long-term P control measures in lakes, inexplicable eutrophication exacerbation still reoccurred over the past two decades. Here we geographically track and analyze the nutrient retention changes of 121 lakes in the USA during 2012-2022 using a combination of machine learning and Bayesian hierarchical methods. We find that the preferential retention of P in 70.3% lakes in 2012 shifted to that of N in 85.1% lakes in 2017, and 92.6% lakes in 2022. Four key lake indicators exhibit flickering-like dynamics, which may help identify the nutrient metabolic disorder-like state in the aquatic ecosystem. Overall, our results show that eutrophication in U.S. lakes during 2012-2022 is advancing on the basis of preferential and net nutrient retention shift from P to N, flickering-like dynamics, and associated occurrence of the nutrient metabolic disorder-like state that are all predominantly driven by internal cycling instead of external loading. These patterns are consistent with the possibility of a regime shift rather than simple eutrophication recurrence, and provide insights relevant to lake management and water quality improvement strategies.

Smaragdinella marine snails are the only members of the family Haminoeidae and the order Cephalaspidea that inhabit hard substrates in the upper tidal zone, making them of special evolutionary interest. To investigate whether possible novel trophic adaptations coupled with unique morphological traits may underlie this ecological shift, we analysed the gut contents and microbiota of Smaragdinella viridis using DNA metabarcoding (COI and 16S rRNA) and scanning electron microscopy (SEM). COI metabarcoding revealed a diverse assemblage of dietary components dominated by diatoms, rotifers, small arthropods, and fungi. SEM observations partially corroborated these findings, indicating an omnivorous feeding strategy rather than strict herbivory. The gut bacterial community was dominated by Firmicutes (Mycoplasma), Proteobacteria (Vibrio, Photobacterium), and Fusobacteriota (Psychrilyobacter, Propionigenium), taxa associated with the degradation of complex carbohydrates and proteins. Morphological traits in Smaragdinella, including an increased number of gizzard plate ridges, a flattened ovoid shell, and an enlarged foot, most likely facilitate the processing of diverse food items and survival in wave-exposed environments. In addition, the functionality of the gut microbiome may contribute to dietary flexibility enhancing survival in dynamic, resource-variable tidal habitats. The adaptation of these snails to tidal hard bottom habitats could have been prompted by the acquisition of novel morphological features and by a diet shift, but the data do not permit to establish a causal relationship and alternative hypotheses may have to be considered.

This study investigated the abundance, characteristics, and potential ecological risks of microplastics in three commercially important fish species (Clarias gariepinus, Oreochromis niloticus, and Labeobarbus spp.) in Lake Tana, Ethiopia. Given the increasing anthropogenic pollution from surrounding urban activities and agricultural runoff, evaluating microplastic ingestion in aquatic biota is critical. Thirty-six fish (n = 12 per species) were collected, and their gastrointestinal tracts were analyzed using stereomicroscopy and an infrared spectrometer. Microplastics were detected in 69.5% of the total samples. The ingestion rates varied significantly among the species, with the omnivorous C. gariepinus showing the highest average contamination (4.92 ± 2.68 microplastics per fish), followed by the phytoplanktivorous O. niloticus (2.17 ± 1.99 microplastics per fish), and the herbivorous Labeobarbus spp.(0.17 ± 0.39 microplastics per fish). Fibers (61.8%) and fragments (36.0%) were the dominant shapes, while red (38.2%) and blue (29.2%) were the most frequently observed colors. Polymer analysis identified polyethylene (55%), polypropylene (27%), and polyethylene terephthalate (18%) as the primary types. The severe contamination observed in C. gariepinus and O. niloticus highlights significant ecological risks and potential human health implications. Targeted interventions, such as improved urban waste management and agricultural runoff control, are urgently needed to mitigate microplastic pollution in the Lake Tana ecosystem.

Polycyclic Aromatic Hydrocarbons (PAHs) are produced whenever there is burning from energy sources, such as coal, oil, gas, wood, garbage, and tobacco. When these chemicals are produced, they tend to bind to or form small particles in the air, water, and soil. While some Polycyclic Aromatic Hydrocarbons are naturally occurring, others are produced by industrial activities, causing potential toxicity to humans, and are reported to interfere with the function of cellular membranes and related enzymes. It has been reported that several carcinogenicity and mutagenicity effects can be traced to the accumulation of PAHs. This work evaluates the properties of selected Polycyclic Aromatic Hydrocarbons to understand their chemical characteristics and assess their carcinogenic potential using density functional theory and molecular docking studies. The selected PAHs include phenanthrene (PHE), pyrene (PYR), benzo[a]pyrene (BAP), fluoranthene (FLT), acenaphthylene (ACY), naphthalene (NAP), fluorene (FLU), chrysene (CHR), benzo-g-perylene (BGP), and benzo-k-fluoranthene (BKF), which were analysed through various methods. Quantum chemical studies showed moderate reactivity of the PAHs, with energy gaps between 3.346 eV and 4.926 eV. Molecular docking revealed moderate to very strong binding energy to the receptor Cytochrome P450 1A1, with predicted binding scores from - 8.3 kcal/ mol to -15.6 kcal/mol. The study suggests that selected PAHs (ACY, BAP, NAP) pose significant health risks, displaying possible interactive toxicity, hepatotoxicity, immunotoxicity, and carcinogenic potential. The findings from this study will serve as a baseline for further investigation and experimental validation of the combined toxicity of selected PAHs in the system, thereby underscoring the need for sustainable environmental remediation strategies.