bluuebunny/crossref_metadata_2025 huggingface dataset:
Physical simulation on oil charging process and controlling factor in reservoirs of Wenchang formation and Enping formation in Zhu-I Depression, Pearl River Mouth Basin
Authors: zhao xiang , liu hua , liu jingdong
Published: March 2024

    The Wenchang Formation and Enping Formation in the Pearl River Mouth Basin have huge oil and gas potential, but the migration and accumulation characteristics are not clear, which seriously restricts the large-scale exploration and development of oil and gas.In combination with thin section,scanning electron microscope and high-pressure mercury injection, physical modeling experiments of oil charging were conducted to find out laws and affecting factors of oil migration and seepage in reservoirs using core samples from reservoir beds of the Wenchang formation and Enping formation in Zhu-I Depression, Pearl River Mouth Basin. The growth curve of oil saturation presents three stages: rapid growth, slow growth and stabilization, and the final oil saturation ranges from 30% to 80%. Reservoir pore types are mainly intergranular pore, dissolution pore and fracture, and reservoir can be divided into three types: high porosity-high permeability, high porosity-low permeability and low porosity-low permeability. At the same time,The growth modes of oil saturation can also be divided into three types: Type Ⅰ is rapid speed growth-high saturation type, corresponding to high porosity-high permeability reservoir; The Type Ⅱ is medium speed growth- medium saturation type, corresponding to high porosity-low permeability reservoirs. The Type Ⅲ is slow speed growth-low saturation type, corresponding to low porosity-low permeability reservoir. The microscopic model diagram of oil charging shows that with the change of reservoir type from high porosity-high permeability to low porosity-low permeability, the main pore types of charging change from intergranular pore and dissolution pore to dissolution pore and fracture, and the growth mode of oil saturation also changes from type I to type III. The accumulation process and flow characteristics of crude oil are dominantly influenced by the injection pressure and pore structure of reservoirs.The injection pressure is a prerequisite for the increase of oil saturation,and pore structure is the main factor to control the growth pattern of oil saturation. Based on the experimental results,the relationship diagram of porosity-permeability- charging pressure-oil saturation is established. According to the distribution of residual pressure and the relationship diagram,the lower porosity-permeability limit of the reservoir to reach the specific oil saturation under different residual pressure can be determined. This is conducive to the dynamic analysis of oil and gas charging process and the prediction of oil saturation under different physical properties and dynamic conditions.
Microbial diversity controls soil multifunctionality across the European continent
Authors: Han Xingguo , Doménech-Pascual Anna , Casas-Ruiz Joan Pere , Donhauser Jonathan , Jordaan Karen , Ramond Jean-Baptiste , Priemé Anders , Romaní Anna , Frossard Aline
Published: March 2024

Soil microorganisms, crucial players of soil organic matter degradation, contribute substantially to global carbon and nitrogen biogeochemical cycles. Although microbial community structure and diversity have been extensively studied at different latitudes worldwide, the relationship between microbial communities, environmental drivers, and ecosystem functions across latitudes has yet to be explored. Here we investigate soil bacterial and fungal community structure and diversity, and ecosystem multifunctionality across different biomes of the European continent from southern Spain (37°N) to Sweden (60°N). Bacterial alpha-diversity increased with increasing the latitude, while fungal alpha-diversity showed an opposite pattern. Fungal communities were more geographically dispersed than bacterial communities. Microbial communities were structured by soil temperature, water content, and resources (TOC, C/N ratio and phosphate). While multifunctionality index related to N cycling functions decreased linearly and significantly with increasing bacterial diversity, it increased significantly with the increases in fungal diversity indices. Our study sheds light on the soil microbial complexity, microbial diversity and function relationship across latitudes and biomes, and highlights the importance of microbial diversity and community structure in driving soil multifunctionality.
Implementation of the Generalized Double-Moment Normalization Method in the Cloud Microphysics Scheme
Authors: Jo JoongHyun , Park Sun-Young , Lim Kyo-Sun Sunny , Bang Wonbea , Lee Gyuwon
Published: March 2024

Cloud microphysics parameterizations are generally divided into two categories: bin models that explicitly calculate the evolution of the drop size distribution (DSD) and bulk models that represent the DSD with a specific function. The Weather Research and Forecasting (WRF) Double-Moment 6-class (WDM6) scheme is one of the bulk microphysics options in the WRF model and is widely utilized for both research and operational purposes. In WDM6 scheme, the gamma form with a single static shape parameter is applied for the DSD of rain. This study adopts a generalized double-moment normalization method for the rain DSD in WDM6 scheme. Previous study mentions that the advantage of the generalized double-moment normalization method lies in its ability to singnificantly reduce the observed DSD scatter. Therefore, it can concisely represent the DSD with appropriate shape parameters, c and μ. The modified WDM6 is evaluated through simulations of an idealized 2D squall line and a summer precipitation case over the Korean peninsula. Based on similar experimental results from the original WDM6 and the modified WDM6 schemes, we can confirm that the generalized double-moment normalization method in the WDM6 scheme is properly implemented. We further collected the observed shape parameters suitable for the generalized double-moment DSD of rain over a two-year summer period (2018, 2019). The modified WDM6, with the observed shape parameters, simulates a more comparable spatial distribution of acummulated precipitation that occurred on 6 August 2013 with the observation, compared to the original WDM6. More detailed simulation results will be presented at the conference. * This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT). (grant no.RS-2023-00208394).
Aerosol Type Classification and Surface Reflectance Optimization for GOCI-II Aerosol Retrieval.
Authors: Lee Jeewoo , Kim Jhoon , Lee Seoyoung
Published: March 2024

Since its launch in 2020, the GOCI-II (Geostationary Ocean Color Imager-II) onboard the GEO-KOMPSAT-2B (GK-2B) satellite has provided aerosol products using the Yonsei aerosol retrieval (YAER) algorithm (Lee et al., 2023). The GOCI-II YAER algorithm retrieves aerosol optical depth (AOD) at 550 nm using an inversion algorithm with a precalculated look-up table (LUT) over UV to near-IR wavelengths. The surface reflectance database is collected using the Cox and Munk method (Cox and Munk, 1954) and the minimum reflectance technique (Hsu et al., 2004) over ocean and land, respectively. The minimum value of Lambertian Equivalent Reflectance (LER) of each wavelength is designated as the surface reflectance at each pixel. The 550 nm AOD is calculated by averaging the weighted AOD of two aerosol types that minimize the standard deviation among the six pre-assumed types.In this study, we improved the performance of the GOCI-II YAER algorithm by renewing the surface reflectance database and the aerosol type selection phase. First, we validated the spectral AOD of the YAER algorithm to that of the AErosol RObotic NETwork (AERONET) to test the accuracy fluctuations between each wavelength. The wavelength with its AOD showing the highest consistency with that of AERONET was selected as the standard of the minimum reflectance composition. Second, aerosol type selection was modified to consider more information on the aerosol optical properties. As a result, the improved product showed better validation statistics when compared to AERONET AOD in terms of % within expected error (EE), the correlation coefficient, and the root mean squared error (RMSE). The improved GOCI-II aerosol products can help the air quality policymakers and broaden our knowledge of distribution of aerosols over Northeast Asia.
Effects of Different Vegetation Restoration Measures on Soil Health in Black Soil Region of Northeast China
Authors: Liu Bingjie , Fu Yu
Published: March 2024

To research the soil health of different vegetation restoration measures in black soil region of Northeast China, the 0-10cm soil layer with different vegetation restoration measures (pure larch forest and mixed forest) were selected to be the object of study in Binxian County, Harbin City, Heilongjiang Province, China. The farmland were selected to be the control check (CK). The soil physical, chemical and biological indexes have been measured to determine the soil health of the soil with different vegetation restoration measures. The results showed that (i) in the 0-10cm soil layer, the soil bulk density of pure larch forest and mixed forest decreased significantly by 16% and 23%. The soil of the mixed forest has a lower soil bulk density and a higher soil water holding capacity and porosity. Compared with the soil of CK, the soil mean weight diameter of pure larch forest and mixed forest were significantly increased by 211.73% and 338.35%. The soil geometric mean diameter (GMD) of pure larch forest and mixed forest were significantly increased by 180.78% and 248.99%. (ii) The soil total carbon of pure larch forest and mixed forest were significantly increased by 39.98% and 43.98%. The soil total nitrogen of pure larch forest and mixed forest were significantly increased by 54.95% and 53.47%. The soil available K of pure larch forest and mixed forest were significantly increased by 26.88% and 133.67%. (iii) The soil microbial carbon (S-MC) of pure larch forest and mixed forest were significantly increased by 84.87% and 165.17%. The soil microbial nitrogen of pure larch forest and mixed forest were significantly increased by 10.80% and 62.32%. The Solid-Sucrase of pure larch forest and mixed forest were significantly increased by 45.79% and 73.68%. In general, there were significant differences in soil health among the soil with different vegetation restoration measures and CK. The mixed forest has the best restorative effects in the 0-10cm soil layer, which has the largest increase in GMD, available K and S-MC. The study would like to provide reference for the restoration of land and soil health evaluation in black soil region of Northeast China.
Estimating Seasonal to Multi-year Predictability of Statistics of Climate Extremes using the CESM2-based Climate Prediction System
Authors: Karwat Alexia , Lee June-Yi , Franzke Christian , Kim Yong-Yub
Published: March 2024

Climate extremes, such as heat waves, heavy precipitation, intense storms, droughts, and wildfires, have become more frequent and severe in recent years as a consequence of human-induced climate change. Estimating the predictability and improving prediction of the frequency, duration, and intensity of these extremes on seasonal to multi-year timescales are crucial for proactive planning and adaptation. However, climate prediction at regional scales remains challenging due to the complexity of the climate system and limitations in model accuracy. Here we use a large ensemble of simulations, assimilations, and reforecasts using Community Earth System Model version 2 (CESM2) to assess the predictability of statistics of climate extremes with lead times of up to 5 years. We show that the frequency and duration of heat waves during local summer in specific regions are predictable up to several months to years. Sources of long-term predictability include not only external forcings but also modes of climate variability across time scales such as El Niño and Southern Oscillation, Pacific Decadal Variability, and Atlantic Multidecadal Variability. This study implies opportunities to deepen our scientific understanding of sources for long-term prediction of statistics of climate extremes and the potential for the associated disaster management.
Unraveling the non-linear relationship between surface deformation and active layer thickness in the Qinghai-Tibetan permafrost region
Authors: Chang Tian , Yi Yonghong , Jiang Huiru , Zwieback Simon , Li Rongxing
Published: March 2024

Seasonal freezing and thawing of the active layer in permafrost regions generally induce surface deformation that interferometric synthetic aperture radar (InSAR) can monitor on regional scales. InSAR has been widely used for detecting changes in active-layer thickness (ALT), an indicator of permafrost thaw. Previous studies have shown that the depth of the active layer and its soil water content have a strong influence on the magnitude of the surface deformation, and a linear relationship between ALT and surface deformation is often assumed in poorly drained Arctic soils. However, in dry areas such as the Tibetan Plateau permafrost region, the relationship between ALT and deformation is more complex and challenging to elucidate. To examine the relationship in the Qinghai-Tibetan permafrost region, this study synthesizes InSAR-derived surface deformation data, multispectral measurements from unmanned aerial vehicle (UAV) sensors, and in-situ soil temperature and moisture data along a ~930-km transect. Our analyses reveal that seasonal deformation generally increases with ALT (R=0.74, p=0.26) at sites with moderate to dense vegetation cover (summer NDVI>0.5), aligning with previous research. However, at sites with sparse vegetation (summer NDVI
The balance between nature and human in the carbon and water compound use efficiency of the Yunnan-Guizhou Plateau
Authors: Yang Yang , Nie Xiaowe , Cong Zhiyuan , Pan Xiaoduo , Gong Xinyu , Zhang Zhuoying
Published: March 2024

Carbon and water use efficiencies (CUE and WUE) represent the carbon-water exchange capacity between terrestrial ecosystems and the atmosphere, which are key parameters for evaluating carbon dioxide uptake, the water cycle, and ecosystem balance. Previous studies have matured the assessment of single use efficiency but lack the comprehensive quantification of compound use efficiency (COM). COM can simultaneously evaluate carbon-water use efficiency in karst regions, but its driving mechanism has not been fully explored. Therefore, this study took the Yunnan-Guizhou Plateau as a case, calculated COM based on CUE and WUE, used exploratory spatial analyses to identify the scale effect of spatial divergence of COM, and then explored the driving forces of COM from natural and human factors at optimal scale using the optimal parameter geo-detector model and geographically weighted regression. The results revealed that (1) from 2000 to 2018, the average of CUE (0.6) was higher in the karst areas of the Yunnan-Guizhou Plateau than that in the non-karst areas, whereas the mean WUE (2.41 gC kg H2O) and COM (1.18) were lower than that in the karst areas; (2) except for CUE, the WUE and COM tended to increase, and the change rate was higher in the karst areas; (3) NDVI dominated the spatial divergence of COM, showed a transition from a negative correlation in the eastern of the study area to a positive correlation in the western. Therefore, the findings can enhance our understanding of CUE and WUE in karst areas, which is meaningful for the regional targeted implementation of ecological restoration projects and the promotion of ecosystem carbon-water balance.-
The QuakeMatch Toolbox: Using waveform similarity to enhance the analysis of microearthquake sequences at Swiss geothermal projects 
Authors: Toledo Tania , Simon Verena , Kraft Toni , Antunes Veronica , Herrmann Marcus , Diehl Tobias , Villiger Linus
Published: March 2024

 

Many Swiss microearthquake sequences have been analyzed using relative location techniques. While these methods have often been effective in identifying active fault planes and the tectonic processes driving the seismic activity, several sequences present a limited number of located events. This limitation often hampers the detailed analysis of their space-time evolution, seismicity patterns, and driving mechanisms. 

 

To address this challenge, we introduce a nearly automatic workflow that combines established seismological analysis techniques to enhance the completeness of detected and located earthquakes within a sequence. Starting with a manual catalog (magnitude of completeness, Mc ≈ 1.0−1.5 ML), we compile a template set and conduct a matched filter analysis on a single station with the highest signal-to-noise ratio (SNR). This approach enables the detection of events with local magnitudes ML < 0.0, with waveform similarity further leveraged to determine consistent magnitudes for these detections. The enhanced catalog is statistically analyzed to obtain high-resolution temporal evolutions of the Gutenberg−Richter a- and b-values, and consequently, the occurrence short-term probability of larger events. Finally, strong events are relocated by the double-difference technique, typically improving the final number of relocated events by a factor of 2-5. 

 

The proposed workflow significantly improves the analysis of the spatiotemporal behavior of natural and induced microearthquake sequences. Notably, we employ it for semi real-time monitoring of commercial and scientific fluid-injection projects. The QuakeMatch workflow is implemented in Python and PostgreSQL. We discuss the capabilities of QuakeMatch through examples involving induced microearthquake sequences associated with various geothermal projects monitored by the Swiss Seismological Service within the GEOBEST2020+ project. 
A review of opportunities and challenges for AI driven multi-hazard risk assessment and resilience enhancement in climate services
Authors: Sano Marcello , Ferrario Davide , Maraschini Margherita , Torresan Silvia , Critto Andrea
Published: March 2024

As climate change accelerates and environmental uncertainties mount, traditional models fall short in effectively handling the complexity and fluidity of multi-hazard risk and corresponding resilience measures. Notably, the vast amount of data being collected and the rapid advancements in artificial intelligence offer extraordinary potential. These advancements can equip us to tackle complex climate risks and develop innovative services that empower both government and communities to adapt and thrive.This review aims to bolster research on the transformative potential of Artificial Intelligence (AI), propelled by Machine Learning (ML) and Big Data (BD), to address the escalating challenges posed by climate change across several key areas. On the one hand, it examines AI's capability to process and integrate diverse data sources, such as satellite imagery, monitoring stations, climate models, social data, with varying spatial and temporal resolutions, including the potential of AI tools in identifying and quantifying cascading and interconnected hazard events and potential resilience measures. On the other hand, the review delves into the development of AI-powered climate services designed to manage climate risk and enhance resilience across various sectors. It evaluates the integration of AI techniques in climate services for dynamic, user-centric platforms that offer actionable insights and decision support. The current and future data constraints and emerging opportunities in implementing these services are explored, alongside strategies to overcome these challenges. Additionally, the review considers the scalability and adoption of AI-powered climate services in the future, highlighting the role of AI in revolutionizing the landscape of climate risk assessment and resilience planning.In summary, this comprehensive literature review synthesizes insights from multi-hazard risk assessment and resilience building. It aims to bridge the gap between static risk models and the dynamic reality of climate threats, paving the way for a comprehensive AI-driven framework helping building climate resilience.This research is funded under the European projects MYRIAD-EU (Horizon 2020) and EXPEDITE (Horizon 2021 MSCA).
Characterising functionalised nanoparticles for improving fluid flow for CCUS in legacy hydrocarbon reservoirs 
Authors: Tliba Louey , Hetnawi Afif , Sagala Farad , Menzel Robert , Glover Paul , Hassanpour Ali
Published: March 2024

In recent years there has been rapid development of nanoparticles (NPs). Nanoparticles can be used both as a probe into restricted spaces, such as the pores within a reservoir rock, and as tools for altering wettability or deliberately blocking pore throats to enhance fluid movement in less connected pores. Silica nanoparticles can have functional surfaces allowing them to react specifically to oils or water. Nanoparticles can be used to enhance oil production by releasing oil on mineral surfaces and improving fluid flow. However, they also have the potential for improving CO2 flow in CCUS reservoirs while enhancing the pore volume available for CO2 storage. In this paper we evaluate the performance of different non-functionalised and functionalised nanoparticles for enhancement of oil production, CO2 emplacement and gas flow. Different forms of silica NPs have been made, either unfunctionalized, or functionalised with branched amino-based polymer (hydrophilic) or a silane-based agent (hydrophobic). Their stability has been characterised using a range of laboratory methods. The microscopic performance of the nanoparticles has been measured using contact angle measurements. Their ability to enhance oil production and CO2 emplacement has been tested using imbibition and drainage experiments. The contact angles, measured in the presence of brine, no modified silica NPs, branched amino-based polymer (hydrophilic) modified silica NPs and silane-based agent (hydrophobic) modified silica NPs showed contact angle values of approximately 110°, 116°, 124°, and 136°, respectively. These results show that introduction of nanofluids led to a change in substrate wettability from water-wet to strongly water-wet. Notably amongst the tested nanoparticles the Silane-based NPs demonstrated the highest hydrophilic surface. The spontaneous imbibition tests conducted on various sandstone cores revealed that silane-based NPs yielded the highest oil recovery rates among the tested NPs. Specifically, these nanoparticles showed an approximate 12% and 50% enhancement in oil recovery compared to non-modified silica nanoparticle, and branched amino-based polymer (hydrophilic) modified silica NPs. In summary, nanofluids have been shown to substantially improve the wettability alteration of the rock surface from oil-wet to water-wet, which can lead to improve the volume and flow characteristics of legacy CCUS prospects. Our future plan is to investigate the enhancement of carbon dioxide (CO2) solubility in brine through the utilization of the prepared nanoparticles, with the objective of advancing carbon capture technologies.
Consumption of methane by a landfill cover soil under variable moisture and temperature conditions
Authors: Lam Christina , Slowinski Stephanie , Ramezanzadeh Mehdi , Hug Laura , Willms Nathanael , Van Cappellen Philippe , Rezanezhad Fereidoun
Published: March 2024

Landfills are one of the largest anthropogenic sources of methane (CH4), and hot-spots of CH4 emissions in landfill cover soils can enrich microbes that oxidize CH4 to carbon dioxide (CO2). CH4 oxidation rates are modulated by multiple variables including soil moisture and temperature, although the interactive effects of these factors on CH4 oxidation rates have not been well-studied. Here, we conducted a closed-headspace batch experiment with cover soil from a former landfill in Ontario, Canada to measure CH4 consumption and CO2 efflux rates associated with variations in soil moisture and temperature simultaneously. Soil samples were incubated under a factorial design of 5 soil moisture contents ranging from 11 to 47% WFPS (water-filled pore space), and 6 temperatures ranging from 1 to 35°C. At each temperature and WFPS combination, CH4 (812 nmol) was spiked into the headspace, and headspace CH4 and CO2 concentrations were measured over 2 hours to calculate CO2 efflux and CH4 consumption rates. The maximum CO2 efflux rate was observed at the maximal WFPS and temperature conditions of this experiment (92 nmol h-1 g dry wt.-1 at 47% WFPS and 35°C), while the maximum CH4 consumption rate was observed at intermediate WFPS and temperature conditions (1.9 nmol h-1 g dry wt.-1 at 25% WFPS and 25°C). The CO2 efflux observed is primarily attributed to the oxidative degradation of soil organic matter. A diffusion-reaction model was fit to the observed data to represent the effects of temperature and soil WFPS on the CH4 consumption and CO2 efflux rates. The model predicted similar optimal conditions as those observed for both the CH4 consumption and the CO2 efflux rates. The modeling and experimental results show that the dominant controls on optimal soil moisture for CH4 consumption are moisture limitation of microbial activity and of gas (CH4 and oxygen) diffusion, versus the interactive effects of moisture limitation of gas (oxygen) diffusion and of solute mobility for CO2 effluxes. These results provide insight into how seasonal changes in soil moisture and temperature could impact CH4 oxidation rates, and therefore also net CH4 emissions, in landfill cover soils and other environments.
Slip Behaviors Controlled by Rheological and Frictional Properties of A Two-Phase Mélange in Subduction Shear Zones
Authors: Xie Jun , Ding Xiaotian , Xu Shiqing
Published: March 2024

A rich spectrum of slip behaviors, spanning from aseismic creep (mm/yr) to seismic slip (m/s), has been observed in many subduction zones and some strike-slip faults. Slow earthquakes, intermediate between these two end-member modes, exhibit transitional slip behaviors in fault sections adjacent to the seismogenic zone. Focusing on subduction zones, it is shown that they experience deformation not only along discrete fault planes but also over distributed frictional-viscous shear zones, the latter of which are thought to be responsible for the observed diverse slip behaviors. Here we employ a frictional-viscous mélange model consisting of brittle blocks surrounded by a viscous matrix to investigate its influence on slip behaviors. By varying the mélange's rheological and frictional properties, we observe a diverse range of slip behaviors. We also reproduce the source scaling relations observed in natural faults, including the relation between seismic moment and duration and that between moment magnitude and stress drop. Additionally, we find a close link between the modeled shear zone deformation patterns and the various geological structures observed in natural fault zones. Our study demonstrates that the interaction between the frictional and viscous compositions of the mélange is responsible for the resulting slip behaviors and their transitions under different compositional ratios. These results provide useful clues for constraining the environmental and rheological conditions of different subduction zone sections from the observed slip behaviors.
Appropriate Thermal Modelling Approaches for Interpreting Topographic and Tectonic Change from Thermochronometer Data (Remembering the Geotherm and 200 years of Lord Kelvin’s legacy)
Authors: Ehlers Todd A. , Willett Sean D.
Published: March 2024

Quantifying rates and magnitudes of topographic change across timescales requires diverse observational and modeling techniques.  Low-temperature thermochronometer methods are a powerful tool for quantifying denudation rates, paleotopography, and/or the kinematic history of orogens over geologic timescales.  Parallel to thermochronometer technique development, a range of thermal, kinematic, and erosion modeling approaches are available to interpret tectonic and surface processes from thermochronometer data. However, differing thermal modelling approaches exist in the literature and often lead to the question of which approach is most appropriate, and when?This presentation addresses the diversity of thermo-kinematic and erosion modelling approaches available to quantitatively interpret topographic change or tectonic processes from thermochronometer data. Emphasis is placed on deciphering the different approaches available and which approach is suitable for the scientific questions asked (e.g., topographic change, tectonic/faulting history, etc.) in diverse geologic settings.  Thermo-physical factors explored include the appropriate model spatial dimension (e.g., 1D, 2D, vs. 3D); the influence of model geometry on geotherms; the importance of constant basal temperature vs. flux basal boundary conditions; transient vs. steady-state geotherms, and how tradeoffs in different parameters (exhumation rate, material properties, boundary conditions) can produce similar thermochronometer ages. The presentation focuses on examples from the literature, ranging from William Thompson’s (Lord Kelvin) founding work on continental geotherms to contemporary numerical modeling approaches.
Using multispectral imagery to characterise weathering: A case study of moraines in the Central Andes
Authors: D'Arcy Mitch , Lang Martin , Schildgen Taylor F. , Crawford Henry T. , Brooke Sam
Published: March 2024

There is growing recognition that multispectral satellite imagery can be used to characterise the weathering state of material exposed at the Earth’s surface. However, it remains unclear if and how satellite-derived weathering indices can be linked, in a universal way, to the fundamental controls on weathering (e.g., surface age and composition, temperature, moisture availability). Here, we use Landsat-8 Operational Land Imager (OLI) multispectral imagery to characterise the reflectance of 75 dated moraines, distributed throughout the Central Andes between 7 and 27 °S. As imaged from space, these moraines represent ageing surfaces composed of sediment that is undergoing physical and chemical weathering. The moraines present an ideal opportunity to explore the controls on weathering over 103-105 year timescales, because they span major gradients in age (1-112 kyr), temperature (2-9 °C), precipitation (100-1000 mm/yr), and also lithological composition.From contrast-enhanced Landsat-8 imagery, we derive a simple band ratio that has been demonstrated to act as a weathering index, scaling with the extent of chemical weathering and the presence of secondary minerals. At every location, we observe a non-linear increase in the weathering index with moraine age. Older moraines exhibit a systematic shift in brightness from visible wavelengths to the short-wave infrared, driven by mineralogical changes during weathering. We also detect subtler variations in the rates and magnitudes of changes in the weathering index that relate to lithological composition. Moraines with mineralogically-diverse compositions (e.g., intrusives and volcanics) display faster and larger increases in the weathering index compared to moraines with mineralogically-simple lithologies (e.g., quartzite and carbonates). Next, we derive the rates of change of the weathering index as a function of moraine age, and compare with past climate. Precipitation emerges as a key control on the weathering index, with faster weathering coinciding with wetter conditions in both time and space. The weathering index increases faster during known episodes of wet climate in the past, registering both 23 kyr precessional cycles and abrupt, 1 kyr Heinrich events. The weathering index also exhibits significantly larger increases in the northern Central Andes, where the climate is much wetter, compared to the southern Central Andes where the climate is drier. Temperature exerts an inverse control on the weathering index, which we speculate reflects the role frost-shattering plays in facilitating chemical weathering.This work demonstrates that freely-available Landsat-8 imagery can be used to reconstruct the weathering of sedimentary landforms across time and space. Furthermore, our results hint at the presence of fundamental relationships between weathering state, as detected by multispectral sensors, and primary variables such as time, substrate composition, and climate.
Reduced Southern Ocean CO2 uptake due to the positive SAM trend
Authors: Menviel Laurie , Spence Paul , Kiss Andrew , Chamberlain Matthew , Hayashida Hakase , England Matthew , Waugh Darryn
Published: March 2024

While the Southern Ocean (SO) provides the largest oceanic sink of carbon, some observational studies have suggested that the SO total CO2 (tCO2) uptake exhibited large (~0.3 GtC/yr) decadal-scale variability over the last 30 years, with a similar SO tCO2 uptake in 2016 as in the early 1990s. Here, using an eddy-rich ocean, sea-ice, carbon cycle model, with a nominal resolution of 0.1°, we explore the changes in total, natural and anthropogenic SO CO2 fluxes over the period 1980-2021 and the processes leading to the CO2 flux variability.The simulated tCO2 flux exhibits decadal-scale variability with an amplitude of ~0.1 GtC/yr globally in phase with observations. Notably, two stagnation in tCO2 uptake are simulated between 1982 and 2000 as well as since 2012, while a re-invigoration is simulated between 2000 and 2012. This decadal-scale variability is primarily due to changes in natural CO2  (nCO2) fluxes south of the polar front associated with variability in the Southern Annular Mode (SAM). Positive phases of the SAM lead to enhanced SO nCO2 outgassing due to higher surface natural dissolved inorganic carbon (DIC) brought about by a combination of Ekman-driven vertical advection and DIC diffusion at the base of the mixed layer. The pattern of the CO2 flux anomalies indicate a dominant control of the interaction between the mean flow south of the polar front and the main topographic features. While positive phases of the SAM also lead to enhanced anthropogenic CO2 (aCO2) uptake south of the polar front, the amplitude of the changes in aCO2 fluxes is only 25% of the changes in nCO2 fluxes. Due to the larger nCO2 outgassing compared to aCO2 uptake as the SH westerlies strengthen and shift poleward, the SO tCO2 uptake capability thus reduced since 1980 in response to the shift towards positive phases of the SAM. 
Spatiotemporally-separated framework for the source reconstruction of atmospheric radionuclide releases
Authors: Xu Yuhan , Fang Sheng , Dong Xinwen , Hu Hao , Zhuang Shuhan
Published: March 2024

Determining the source location and release rate is critical in assessing the environmental consequences of atmospheric radionuclide releases, yet this task remains challenging due to the vast multi-dimensional solution space. To address this, we propose a spatiotemporally-separated two-step framework that reduces the dimension of the solution space in each step and enhances the reconstruction accuracy, which is applicable to radionuclide releases. The separating process involves applying a temporal sliding-window average filter to the observations, thereby reducing the influence of temporal variations in the release rate and ensuring that the features of the filtered data are dominated by the source location. Initially, candidate source locations are pre-screened using a correlation-based method. To establish the relationship between the filtered data and candidate source locations, time- and frequency-domain features are extracted from the filtered data and an eXtreme Gradient Boosting algorithm is employed for fitting. The features are further screened out by the Recursive Feature Elimination with Cross-Validation. Utilizing the features of filtered observations, the source location can be determined without the knowledge of the release rate. Subsequently, the release rate is determined using projected alternating minimization with the L1-norm and total variation regularization algorithm.The proposed method was rigorously tested on two field experiments: the SCK-CEN experiment, featuring local-scale 41Ar releases over two days, and the ETEX-I experiment, involving continental-scale PMCH releases. Validation on the SCK-CEN experiment showed that the lowest source location error fell below 1% and the mean source location error remained under 5%, with temporal variations and peak release rate being accurately reconstructed. Similar accuracy was also observed in the ETEX-I experiment. Compared to traditional correlation-based method and Bayesian method, our method exhibited superior accuracy and a reduced uncertainty range.Furthermore, comprehensive sensitivity tests were conducted on the SCK-CEN experiment to evaluate the influence of pre-screening range, sliding-window length, feature types, and combinations of observation sites. The results indicated that our method achieved consistent performance across various parameters and conditions, maintaining low error levels even with only a single observation site.
Glacier mass change gridded data from 1976 to present derived from the Fluctuations of Glaciers Database - A new product in the Copernicus Service Climate Data Store
Authors: Dussaillant Ines , Bannwart Jacqueline , Paul Frank , Zemp Michael
Published: March 2024

Glaciers play a fundamental role in the Earth’s water cycles. They are one of the most important freshwater resources for societies and ecosystems and the recent increase in ice melt contributes directly to the rise of ocean levels. For this reasons, they have been declared as an Essential Climate Variable (ECV) by the Global Climate Observing System (GCOS). Within the Copernicus Climate Change Services (C3S), the global gridded annual glacier mass change dataset provides information on changing glacier resources for the last five decades by combining the glacier outlines from the globally complete Randolph Glacier Inventory with the mass balance and elevation change observations from the Fluctuation of Glaciers database of the World Glacier Monitoring Service (WGMS).The glacier change product provides a global assessment of annual glacier mass change and related uncertainties (in m w.e. and Gt) and gridded area changes (km2)  since the hydrological year 1975/76 to present, provided in a 0.5°x0.5° (latitude-longitude) global regular grid and in netcdf file format. The new product bridges the gap on spatio-temporal coverage of glacier change observations, providing for the first time in the CDS an annually resolved glacier mass change product using the glacier elevation change sample as calibration. This goal has become feasible at the global scale only recently and thanks to a new globally near-complete (96% of the world’s glaciers) dataset of glacier elevation changes between 2000 and 2020.The global gridded annual glacier mass change product integrates nicely into the family of the gridded ECV products provided by the C3S CDS. It provides new insights into regional to global glacier mass changes and, hence, has a great potential for contributing to the various state of the climate reports as well as to assessments of the global sea-level budget, the global energy cycle or the global water cycle. Continuation and expansion of the glaciological in-situ observation network is essential for providing the temporal variability of the glacier mass change product. Ensuring the continuation of open source spaceborne datasets with extensive acquisitions tasking planned over glaciated regions is crucial for ensuring the good quality of future glacier products, and one of the greatest gaps in the quality and continuation of the glacier services delivered to C3S.
An overview of environmental seismology used to study the internal structure of the North East Greenland Ice Stream 
Authors: Pearce Emma , Zigone Dimitri , Fitchner Andreas , Hofstede Coen , Rimpot Joachim , Brehmer-Moltmann Johanna , Eisen Olaf
Published: March 2024

In 2022 a network of 23 seismometers and Distributed Acoustic Sensing (DAS) fibre optic cable were deployed on the North East Greenland Ice Stream (NEGIS). Using a combination of environmental seismology methods, we were able to gain a comprehensive understanding of the ice streams internal structure, giving insight into its past and present dynamics.  From ambient noise recording, we utilise the 9-component correlation tensors associated with all station pairs.  We derived dispersion curves for Rayleigh and Love wave group velocities with usable data in the frequencies from 1 to 25 Hz. These data are then inverted to obtain shear wave velocity measurements for the top 150 m of the ice stream using an MCMC approach. We reveal variations in the radial anisotropy for both the along and across-flow components.Alternative methods of passive seismology were explored, such as using the seismic signal from an airplane landing. The recorded signals by the surface DAS cable displayed exceptional clarity, revealing at least 15 visible wave propagation modes, including various Rayleigh and pseudo-acoustic waves within the frequency range of 8 to 55 Hz.Seismic While Drilling (SWD) methods utilising the noise from ice core drilling and cutting at NEGIS were investigated as an unconventional signal at the borehole camp. While not successful in this instance, recommendations for future deployments were provided to optimize the utilisation of these techniques.These methods collectively offer insight into the layering of snow, firn, and ice within the ice stream, indicating the presence of seismic anisotropy. Demonstrating the effectiveness of short-duration (2-3 weeks) seismic deployments in glaciology.  
NMME Experimental Subseasonal Precipitation Forecasts (SubX) provide enhanced predictions of end-of-season water balance over Sub-Saharan Africa
Authors: Turner William , Shukla Shraddhanand , Husak Greg
Published: March 2024

The Famine Early Warning Systems Network (FEWS NET) and its partners use timely and spatially focused monitoring products to guide humanitarian assistance and secure livelihoods in some of the world’s most food-insecure populations. Subseasonal predictions bridge the gap between coarse, seasonal climate predictions and finer-scale, medium-range weather forecasts, providing insight for in-season agricultural decision making, including planting dates, labor allocation, and loan and fertilizer investments. In adverse conditions, they can increase the lead-time for necessary intervention (e.g., food or monetary aid); and in favorable conditions can provide opportunities for increased investment and subsequent improved agricultural productivity. Accuracy in forecasting both each scenario can enhance loss mitigation and increase capital, providing opportunities for long-term resilience building and poverty reduction. Collectively, this work aims to improve upon and contribute to early warning systems in semiarid African rainfed agricultural zones for the purpose of improving food security and livelihoods.Here we report on an ongoing project to assess the efficacy of the NMME Experimental Subseasonal Precipitation Forecasts (SubX) for use in a regional water balance model—the Water Requirement Satisfaction Index (WRSI)—in Sub-Saharan Africa. While SubX has been shown to be effective for hydrologic monitoring in India and eastern South America, and for predicting extreme events, including droughts and floods in the US and South Korea, assessments of the accuracy and certainty of SubX is quite limited over Africa. We begin to fill this gap by assessing the viability of SubX for use in WRSI deterministic and probabilistic forecasts in rainfed agricultural areas of east, southern, and west Africa, from 1999-2016. We briefly explore the regional characteristics and inter-model variability in forecast skill.
Connecting the dots: teleconnection of global floods and their association with climate variability
Authors: Yang Yixin , Yang Long , Wang Qiang , Villarini Gabriele
Published: March 2024

A fundamental question in global hydrology is how global floods behaved in the past and are expected to behave in the future. Previous site-specific analyses might offer locally relevant insights, but little is known about how floods are connected in space and time as well as their synchronous responses to climate variability at the global scale. Here we carry out empirical analyses based on a comprehensive dataset of annual maximum flood peak series from 4407 stream gaging stations. We establish the link between any two stream gages if their annual maximum flood peak discharges are significantly correlated and the dates of their occurrences are sufficiently close (using event synchronization and complex network). Our results identify notable remote links of annual flood peak series over western Canada/US (e.g., upper Missouri River basin), northern Europe (e.g., Kemijoki River basin), southern China (e.g., middle Yangtze River basin), and northern South America (e.g., Amazon River basin). Annual flood peak series are linked to their local neighbors (within a distance of 4500 km) over eastern United States, central Europe, and eastern Australia. Remote links highlight the spatial dependence of riverine floods at the global scale. These links are dictated by the oscillation of dominant climate modes over the Pacific Ocean (e.g., El Niño Southern Oscillation, Pacific Decadal Oscillation) and their resultant anomalous atmospheric circulation patterns. Local flood clusters are more responsive to region-specific atmospheric forcings. The complex flood network plays an important role in regulating the dynamic behaviors of flood hazards. Our results offer new insights into global flood hydrology and their connections with large-scale climate forcings.