bluuebunny/crossref_metadata_2025 huggingface dataset:
Interactions between soil mineral composition and particulate organic matter mediate bioavailable nitrogen 
Authors: Jilling Andrea , Carrell Marian , Grandy A. Stuart , Hestrin Rachel , Keiluweit Marco , Knatvold Erik , Whitaker Andrew
Published: March 2024

Soil organic matter (SOM) can supply critical quantities of nitrogen (N) to plants, but fundamental questions remain regarding from what pools and by which processes plants and microbes obtain N. The source of bioavailable N is generally assigned to polymeric or particulate organic matter (POM), but in mineral soils, POM is often a minor pool of N and can be a poor predictor of bioavailable N or plant N uptake. Mounting evidence suggests mineral-associated organic matter (MAOM) is significantly more dynamic than previously assumed and may serve as an important source of N for plants and microbes. The abundance and chemical traits of POM (e.g., C/N ratio) are likely key controls on N mineralization, but bioavailable N is also regulated by the capacity for minerals to intercept, immobilize and release DON via sorption and desorption.Our objective was to assess how the relative abundance of and chemistry of MAOM controls N bioavailability. The conceptual underpinnings for this project will be presented as will the result of an associated lab incubation. We assembled mixtures of POM and MAOM and manipulated the MAOM type and the POM:MAOM ratio to achieve varying levels of POM-N supply and mineral sorption capacity. MAOM was isolated with a particle-size based fractionation technique from four soil types that differed in mineralogical composition as determined via X-ray diffraction. Wheat residue was partially decomposed in the lab to 60% of original mass to generate POM, which was then mixed in varying ratios with a fixed amount of MAOM to achieve 5, 10, 15, and 20% of POM-N out of total soil N. Mixtures were brought to 40% of water-holding capacity and incubated for seven days. Destructive sampling occurred on days 0, 2, and 7 to assess KCl-extractable inorganic N (ammonium + nitrate), pH, and gross ammonification and nitrification rates. Greater abundance of POM-N was associated with increased inorganic N. However, when normalized to total N, we observe notable differences by MAOM type where ammonium was more bioavailable in soils with greater 2:1 clays and iron oxide minerals. We expect gross mineralization results to shed more light on how MAOM-N quantity and mineral surface properties interact with POM-N supply to control the supply of bioavailable N.
Enhancing Microplastic Transport Research in Agricultural Soils through Fluorescent Particles: A Simplified Method for Detection and Quantification
Authors: Sinha Ray Saunak , Zumr David , Dostal Tomas
Published: March 2024

Preselection of polymer characteristics has been demonstrated to streamline the recovery process in microplastic transport studies, obviating the need for extensive post-examination procedures. Nevertheless, the labor-intensive nature of microplastic extraction and identification remains a significant challenge. This study introduces a novel protocol employing fluorescent microplastic particles for expeditious identification and enumeration without the requirement for extraction, thereby contributing to the cost-effective advancement of microplastic transport research. Size fractionation was utilized to evaluate the protocol's efficacy with respect to 100–500 µm polyethylene (PE) and polylactic acid (PLA) microplastics in soil and sediment matrices, resulting in a substantial 90 to 95% reduction in sample volume post-sieving. Sample assays were conducted under controlled darkroom conditions using a 365 nm excitation wavelength UV lamp, with a digital camera set at 0.2 s, ISO200, and F5.6. Image J analysis ensured meticulous identification, quantification, and characterization of fluorescent microplastics, revealing 95% precision, a 90% F-score, and an 85% recovery rate. Application of the protocol to an agricultural plot-scale case study demonstrated its effectiveness in identifying and quantifying fluorescent microplastic particles in soil samples. This investigation, conducted on five plots (1m x 1m) subjected to rainfall simulations at an intensity of 60 mm h−1, involved the addition of 7.1 g m−2 of fine (size 125-150 µm) and coarse (size 425-500 μm) fluorescent polyethylene to the topsoil (1 cm). The results indicated a preferential erosion and transport of the microplastics. Overall, our study underscores the utility of fluorescent particles as proxies and their identification through our developed protocol as an effective means of advancing microplastic fate, transport, and deposition research in field and laboratory-scale experiments. Additionally, it highlights that agricultural land susceptible to soil erosion can constitute a significant reservoir of microplastics for aquatic ecosystems.
Deposition of synthetic polystyrene and low-density polyethylene to quartz sand in different background solutions
Authors: Saliminasab Somayeh , Cheng Tao
Published: March 2024

Microplastics (MPs) and nanoplastics (NPs) have gained considerable attention as emerging contaminants that can pose potential risks to subsurface environments due to their widespread presence and persistence in the environment. They can act as carriers for other contaminants, such as heavy metals, by adsorbing onto their surfaces, potentially increasing their mobility and consequently causing toxicity to organisms and human health. MPs and NPs can enter groundwater through landfill leachate, agricultural mulches, and wastewater effluent. However, MPs’ and NPs’ behavior in porous media with complicated components has not been thoroughly examined. Therefore, further research is essential to identify the key factors such as aggregation (particles attaching to each other) and deposition (particles attaching to a transport medium), that may influence MPs' and NPs' behavior, fate, and transport mechanisms in soils and groundwater.The purpose of our research is to investigate how plastic particle properties, pore water chemistry, as well as characteristics of the medium would influence the aggregation and deposition of MPs and NPs.This study focuses on the attachment of low-density polyethylene micro- and nano-plastics (LDPE) released from macro-plastic pellets and synthesized polystyrene micro-spheres to quartz sand under controlled laboratory conditions. Batch experiments were performed to study the aggregation and deposition of LDPE and synthesized polystyrene micro-spheres onto quartz sand that allow for precise control over environmental variables, facilitating the observation of microplastic-sand interactions in varying background solutions. The influence of two common salts, sodium chloride (NaCl) and calcium chloride (CaCl2), on the attachment process is systematically investigated. The results from our experiments indicated that similar to polystyrene micro-spheres, the LDPE particles did not adsorb to quartz sand at pH 5 in 3 mM NaCl solution, while a substantial amount of LDPE adsorbed to quartz sand in 1 mM CaCl2 at pH 5. This could be attributed to the less negative zeta potential of LDPE (~-25 mV) and polystyrene micro-spheres (~-17 mV) in 1mM CaCl2 background solution as a result of lower electrostatic repulsion between particles.Results from these experiments provide insights into the complex mechanisms governing MPs' and NPs' behavior in aquatic environments, aiding in the development of strategies to mitigate their impact on ecosystems.
Physical and chemical effects of natural zeolites additives on the cementitious stabilization of cesium and barium isotopes in boric acid liquid waste  
Authors: Iklaga Gabriel , Kaposy Nándor , Tolnai Istvan , Gável Viktória , Fábián Margit , Szabó Csaba , Völgyesi Péter , Szabó-Krausz Zsuzsanna
Published: March 2024

Boric acid is used in pressurized water reactor (PWR) systems as an efficient neutron absorber for activity control which aids in the maintenance of steady state operating temperature control. The boric acid liquid waste produced from the system might contain low concentrations of nuclear fission produced radioisotopes such as 137Cs and its metastable decay product 137mBa (also named as 137mCs). Adequate repository storage of this high-volume liquid waste has become environmentally important for study as these radioisotopes can become bio-available in the natural systems if not effectively immobilized. Our research main aims are to assess the geochemical effects of natural zeolite (i.e., clinoptilolite and mordenite) additives in sulfoaluminate cement (SAC) and ordinary Portland cement (OPC) blends for optimizing chemical and mechanical stability for immobilizing boric acid liquid waste and contained fission isotopes, mentioned above in solidified cement paste waste forms.To accomplish our research goal, the natural zeolite additives at ratios ranging from 0%, 5%, 10%, 15% and 20%, respectively, were added to a benchmarked OPC to SAC blend (i.e., 80% OPC to 20% SAC) based on results from our previous experiments. The samples were then mixed with simulated boric acid liquid waste containing Cs and Ba isotopes and allowed to cure for 28 days. Standardized reference leaching test was carried out on the cured solid waste forms for 11 days and then they were analyzed by standardized compressive strength test, scanning electron microscopy (SEM) for morphology and X-ray diffraction (XRD) for mineralogy. While the liquid waste solutions (leachate) from the leaching test were analyzed by inductively coupled plasma optical emission spectroscopy (ICP-OES) and inductively coupled plasma mass spectroscopy (ICP-MS) to assess elemental and isotopic changes.  
Acceleration and Release of Solar Energetic Particles Associated with a Coronal Shock on 2021 September 28 Observed by Four Spacecraft
Authors: Zhuang Bin , Lugaz Noé , Lario David , Kwon Ryun Young , Chrysaphi Nicolina , Niehof Jonathan , Gou Tingyu , Zhao Lulu
Published: March 2024

The main driver of the acceleration of solar energetic particles (SEPs) is believed to be shocks driven by coronal mass ejections (CMEs). Extreme ultraviolet (EUV) waves are coronal disturbances that have been interpreted as the propagating footpoint of CME-driven shocks on the solar surface. One of the key questions in SEP research is the timing of the SEP release with respect to the time when the EUV wave magnetically connects with an observer. Taking advantage of the measurements by Parker Solar Probe (PSP) and Solar Orbiter (SolO) close to the Sun, we investigate a SEP event that occurred on 2021 September 28 and was observed at four different locations by SolO, PSP, STEREO-A, and the near-Earth spacecraft. During this time, SolO, PSP, and STEREO-A shared similar nominal magnetic footpoints but were at different heliocentric distances. We find that the SEP release times estimated at these four locations were delayed compared to the times when the EUV wave intercepted the footpoints of the nominal magnetic fields connecting to each spacecraft by around 30 to 60 minutes. Combining observations in multiple wavelengths from radio to EUV wavelengths passing by white light, with a geometrical shock model based on multi-viewpoint observations, we analyze the associated shock properties, and discuss the acceleration and delayed release processes of SEPs in this event as well as the accuracy and limitations of using EUV waves to determine the SEP acceleration and release times.
Effect of biochar application depths on leaching of nitrate and crop growth
Authors: Hamada Kosuke , Nakamura Satoshi
Published: March 2024

Abundant use of chemical fertilizer causes reactive nitrogen load to the environment. Leaching of reactive nitrogen occurs mainly in nitrate (NO3−N) form, which moves into groundwater and other water bodies causing human health hazard and harming ecosystems, especially in tropical islands. Biochar application, which is known as a measure of carbon sequestration, can mitigate the leaching of NO3−N. We have accumulated knowledge regarding the effective application rate of biochar. However, the information on the effect of biochar application depth remains unclear, although it would affect the leaching of NO3−N and crop growth. The objective of this study was to evaluate the effect of biochar application depth on the leaching of NO3−N and crop growth. Using biochar made from bagasse, which is a major organic waste in tropical islands, we conducted a pipe experiment with upland rice (NERICA). We set four treatments: control (no biochar application); surface application (0−5 cm); plow layer application (0−30 cm); subsurface application (25−30 cm). Regarding leaching of NO3−N, the result under surface application showed a 12% decrease, while that under plow layer application showed an 11% increase against that under the control. Whereas the leaching of NO3−N was the same under subsurface application as that under the control. Total nitrogen uptake by crop was the highest under surface application, whereas those under plow layer and subsurface applications were smaller than those under the control. By comparing the leaching of NO3−N with the total nitrogen in the root, we obtained a clear relationship that the higher the total nitrogen in the root was, the lesser the leaching became. The result of the matric potential head in each pipe revealed that soil water condition was stressless for crops under the surface application. On the other hand, dry stress occurred more frequently under plow layer and subsurface applications. These results indicated that, depending on biochar application depth, soil water stress conditions differed and affected root growth positively/negatively. Consequently, crop growth and the leaching of NO3−N were changed. The surface application can be considered as an effective application, which mitigates the leaching and promotes crop growth simultaneously. We believe the finding of this study encourages the establishment of sustainable agriculture.
Changes in the Rate of Ocean Crust Production Over the Past 19 Myr: Implications for Sea Level, Mantle Heat Loss, and Climate
Authors: Dalton Colleen , Herbert Timothy , Wilson Douglas , Si Weimin
Published: March 2024

The rate of ocean-crust production exerts control over mantle heat loss, sea level, seawater chemistry, and climate. Reconstructing ocean-crust production rates back in time relies heavily on the distribution of present-day seafloor age. Different strategies to account for the incomplete preservation of older seafloor have led to differing conclusions about how much production rates have changed since the Cretaceous, if at all. We have constructed a new global synthesis of ocean-crust production rates along 18 mid-ocean ridges for the past 19 Myr at high temporal resolution.  We find that the global ocean-crust production rate decreased by ~37% from its maximum during 19-15 Ma to its minimum during 6-4 Ma. Our ability to resolve these changes at a statistically significant level is due to the availability of many new plate reconstructions at high temporal resolution and our use of an astronomically calibrated magnetic time scale with small uncertainties in reversal ages. We show that the reduction in crust production occurred because spreading rates slowed down along almost all ridge systems. While the total ridge length has varied little since 19 Ma, some fast-spreading ridges have grown shorter and slow-spreading ridges grown longer, amplifying the spreading-rate changes. The change in crust production rate skews the seafloor area-age distribution toward older crust, and we estimate that sea level may have fallen by as much as 32-37 m and oceanic heat flow may have been reduced by 6%. We also show, using a simple model of the carbon cycle, that the inferred changes in tectonic degassing resulting from the crust-production changes can account for the majority of long-term surface-temperature evolution since 19 Ma.
Analysis and Model Verification of Extreme rainfall Processes in Huabei of China in 2023
Authors: guan yue
Published: March 2024

         From July 29 to August 1, 2023, extreme heavy rainfall occurred in the Chinese HUABEI region. Heavy rainstorm occurred in the most areas of Beijing, Tianjin and Hebei province, with the maximum accumulated precipitation of 1103.4 mm. The daily precipitation of 14 national meteorological observatories in Hebei and Beijing exceeded the historical extreme value, and the accumulated precipitation of 26 national meteorological observatories in three days exceeded the historical extreme value. The process intensity exceeded the three extreme rainstorm processes in the history of HUABEI region. Studying the causes of extreme heavy precipitation in HUABEI and evaluating the predictive performance of the model for extreme heavy precipitation is beneficial for improving the application and forecasting ability of the model. This article analyzes the weather scale characteristics and anomalies of this precipitation process from factors such as height field, wind field, divergence field, vorticity field, and water vapor. The dynamic and thermal structure of the vortex and the cause of the upper level continental high are analyzed using the method of cyclone phase space map and full type vorticity equation. Finally, the predictive ability of the model for extreme precipitation is tested.
Determining the CME Onset Mechanism 
Authors: Antiochos Spiro , van der Holst Bart , Gombosi Tamas , Sokolov Igor , Zhao Lulu , Dahlin Joel
Published: March 2024

Coronal Mass Ejections (CME) are the drivers of the most destructive space weather at Earth; therefore, determining their onset mechanism is of paramount importance for both space physics understanding and space weather prediction.  Two types of models for CME onset have been proposed: an ideal instability as in the kink or torus models, or magnetic reconnection as in the breakout or tether-cutting models. These two types are distinguished by the nature of the pre-eruption filament channel that powers the CME, a twisted flux rope in the case of the ideal mechanisms and a sheared arcade in the case of reconnection.  We describe two powerful new capabilities within the Space Weather Modeling Framework (SWMF) that enable the simulation of either ideal or reconnection driven CMEs. For ideal onset, we have developed and implemented a finite-beta extension of the well-known Titov-Demoulin twisted flux rope model. We present simulations using this capability and describe its application to event studies. For reconnection-driven onset we have developed and implemented the STITCH formalism, which efficiently captures the buildup of magnetic shear along a polarity inversion line by the process of helicity condensation.  We present simulations using this capability, as well, and describe its application to event studies. Furthermore, we discuss how these capabilities within SWMF will enable the community to simulate well-observed events with both ideal and reconnection onset, and by detailed comparison with the observations, finally determine the CME onset mechanism.This work was supported by the NSF SHINE Program and the NASA Living With a Star Program. 
On the microstructural evolution of Carrara marble during semi-brittle deformation
Authors: Qu Tongzhang , Brantut Nicolas , Wallis David , Harbord Christopher
Published: March 2024

Semi-brittle deformation, which is characterized by the simultaneous occurrence of fracturing and crystal plasticity, plays a critical role in determining the mechanical properties of the middle crust. Laboratory experiments have identified semi-brittle deformation as ductile flow involving distributed microfracturing, an absence of localized macroscopic failure, and widespread plasticity. However, a constitutive law of semi-brittle deformation remains elusive, and a lack of quantitative microstructural analyses has hindered the development of micromechanical models for semi-brittle deformation.This study aims to address these limitations by providing quantitative characterization of twins, lattice distortion, and intragranular fractures in Carrara marble that has undergone semi-brittle deformation. Three sets of samples were uniaxially shortened to varying strains up to 8% under a confining pressure of 400 MPa and different temperatures at 20, 200, and 350ºC. The tested samples were examined by forescattered electron imaging and electron backscattered diffraction mapping. The results reveal that, in the early stages of deformation (strain < 2%), deformation is primarily accommodated by twins. Lattice distortion, linked to geometrically necessary dislocations, becomes prominent in the later stages (strain > 4%). Intragranular fracture intensity shows a linear correlation with strain. Despite some nuanced variations, the qualitative development of each microstructure type remains similar at different temperatures. At the onset of semi-brittle deformation, microstructural evidence has shown that the nucleation of microfractures or lattice distortion is induced by strain incompatibility at granular scale. The local stress concentrations associated with such strain incompatibility are enhanced by irregularities of grain boundaries. These observations provide a foundational microstructural understanding, facilitating the development of a robust microphysical model for semi-brittle deformation in the lithosphere.
Comparing the performance of Chlorophyll-a retrieval models in coastal and transitional waters 
Authors: Diganta Mir Talas Mahammad , Uddin Md Galal , Dabrowski Tomasz , Olbert Agnieszka I.
Published: March 2024

Among water quality (WQ) indicators, Chlorophyll-a (CHL) plays a pivotal role in assessing algal biomass production in aquatic ecosystems, serving as a crucial parameter for monitoring aquatic health and eutrophication events. Satellite remote sensing (RS) techniques offer an extended spatio-temporal coverage compared to conventional methods, making them valuable for CHL estimation, especially in optically complex waters like coastal and inland areas. However, the retrieval of CHL using RS in such environments poses challenges, and selecting the appropriate algorithm is one such challenge.In this study, Sentinel-3 OLCI images were employed to estimate CHL levels in Cork Harbour, Ireland. Twenty widely used CHL retrieval algorithms, ranging from traditional blue-green band-based ocean color algorithms (e.g., OC4, OC5, OC6) to two-band and three-band NIR-red algorithms, were applied to water leaving reflectance data obtained from the Case 2 Regional CoastColour atmospheric correction algorithms. Additionally, in-situ CHL concentration data from 32 monitoring sites within Cork Harbour were used for validation.The results revealed that three-band algorithms based on NIR-red bands (specifically B12/(B08-B11)) exhibited a higher sensitivity (R2 = 0.77) to in-situ CHL measurements, outperforming other CHL algorithms with superior performance (RMSE = 0.28 mg/m3, MAPE = 28.6%, MAE = 0.28 mg/m3, and MBE = - 0.00 mg/m3). Furthermore, the study demonstrated the potential of Sentinel-3 OLCI satellite images for CHL retrieval in Irish coastal waters. These findings offer valuable insights into optimizing CHL retrieval from remotely sensed data, potentially enhancing traditional monitoring programs by addressing existing limitations.Keywords: Coastal and transitional water quality, chlorophyll-a, retrieval algorithms; remote sensing, atmospheric correction.
Mantle convection modes in 3D mantle convection simulations and its implications for the evolution of Earth’s plate tectonics
Authors: Xiang Song , Huang Jinshui
Published: March 2024

Plate tectonics is the most prominent surface manifestation of mantle convection in Earth. Current observational results suggest that Earth is the only planet displaying plate tectonics. However, whether plate tectonics has accompanied the entire evolutionary history of Earth is a key question. If not, questions such as when plate tectonics began and what kind of tectonic mode prevailed before plate tectonics, have always been at the forefront and hot topics in the field of Earth science.In this study, we employed three-dimensional spherical mantle convection numerical simulations to explore various mantle convection modes. Results indicate that, under different parameter frameworks, mantle convection modes can be categorized into five types: I) non-plate active lid convection mode, where the surface exhibits multiple concentrated weak zones, resulting in relatively fragmented plates; II) plate-like mobile lid convection mode, characterized by a higher number of subduction zones and mid-ocean ridges on the surface, which spontaneously form, develop and disappear over time, dividing the surface into about 10 plates; III) episodic plate-like mobile lid convection mode, where the surface experiences plate-like mobile lid mode for most of the time, interspersed with transient surface stagnation; IV) episodic stagnant lid convection mode, characterized by long periods of surface stagnation interspersed with short periods of surface movement with the surface mostly featuring only one subduction zone. V) stagnant lid convection mode, where the surface appears as a single rigid layer.We mainly analyze the influence of lithospheric strength, i.e., yielding stress, Rayleigh number and internal heat rate on these five mantle convection modes. We can better explain the plate tectonics of the present Earth using mode Ⅱ. Because of the higher internal heat rate, higher mantle temperature and lower mantle viscosity, resulting in a larger Rayleigh number, our research suggests that the early Earth was in mode III or IV. Our results suggest that even if there was some type of plate tectonics in the early Earth, it is different from present plate tectonics. Before the onset of plate tectonics, the Earth might have experienced episodic lid convection. The results hold important scientific significance for understanding the evolution of the Earth's plate tectonics.
Early Pleistocene Sediment Record from the Antarctic Zone of the Southern Ocean Dominated by Obliquity
Authors: Muench Bastian , Garrioch Bella , Bradtmiller Louisa , Billups Katharina
Published: March 2024

We present an orbital-scale record of percent biogenic silica (opal) at Ocean Drilling Program Site 745B situated in the Antarctic Zone of the Indian Ocean sector of the Southern Ocean spanning a majority of the early Pleistocene (1.1-2.6 Ma). By investigating the relative importance of obliquity versus precession-paced variability in our record, we seek to contextualize the apparent dominance of obliquity pacing in early Pleistocene d18O records. Notably, between 1.1 and 1.8 Ma, both the site’s shipboard magnetic susceptibility record and our biogenic silica record principally exhibit obliquity-related spectral peaks at a periodicity of 41 kyr, with relatively minor spectral power at precessional periodicities (23-19 kyr). During the older part of the record (1.8-2.6 Ma), only d18O and magnetic susceptibility vary at the 41 kyr obliquity periodicity, while the biogenic silica record does not show prominent orbital pacing at any of the major periodicities. We suggest that the surprising dominance of obliquity-paced variability in all records between 1.1 and 1.8 Ma indicate a lack of response of the proxies to precessional forcing during this period. The notable lack of orbital forcing in the opal record before 1.8 Ma may reflect both a more southerly location of the polar frontal zone with respect to the site and thus outside the region of wind-driven upwelling and waters undersaturated with respect to silica prior to the establishment of the opal belt at about 2 Ma.
Occurrence and Sources of Microplastics in groundwater divided by well depth and Hydrogeology in South Korea
Authors: Jeon Chan-Hyeok , Kim Hee-Jung , Jeong Darae
Published: March 2024

Groundwater plays a critical role as a vital and renewable water resource for drinking, domestic, and agricultural purposes. Unfortunately, it is under threat from various emerging contaminants, including antibiotic resistance genes, per- and poly-fluoroalkyl substances (PFAS), and micro- and nano-plastics (MNPs). MNPs act as agents, transporting trace heavy metals, hydrophobic pollutants, and toxic chemicals into groundwater from terrestrial and aquatic environments through physical, chemical, and biological processes. The transported MNPs have an impact on human health and ecological species. The objectives of this study were to: (1) assess the abundance of microplastics based on hydrogeology and well depth; (2) characterize the properties of aquifer; (3) identify possible sources of microplastics. The study aims to establish a baseline for the area, contribute to databases on microplastic pollution, and may lead to new solutions for this type of pollution. Data were collected from 17 wells of the National Groundwater Monitoring Network in South Korea. Sixteen water quality parameters, as well as the abundance and properties of microplastics, were analyzed based on depth and hydrology groups. As a result, the average number of microplastics (MPs) detected in 17 groundwater wells, each with a volume of 1.5 liters, was 4.8 particles per liter. In the groundwater samples, a total of six polymer types were identified, including PP, PE, PVC, PS, PA, and PU, with PP and PE being the predominant polymer types. There is a trend where the concentration of MPs tends to be higher in groundwater wells with shallower depths. The main source of MP contamination in groundwater is expected to be the transport through groundwater flow from adjacent industrial and agricultural areas with higher energy levels.
A hydrothermal model for unsaturated frozen rocks based on lattice Boltzmann method
Authors: Wang Zheng , Zhang Chi , Zhang Yaning , Li Bingxi
Published: March 2024

Frost weathering is considered the primary cause of erosion in periglacial environments. This process is initiated by the freezing of water within rock pores and its subsequent expansion, which generates substantial forces leading to the physical fragmentation and disintegration of the rock structure. To detail the mechanism and predict the patterns of rock fracturing, this study has developed a specialized numerical model. In previous study, researchers typically studied the mechanical failure of rocks via macroscopic numerical methods. However, these methods often face limitations in depicting mesoscale forces, particularly in the context of multiphase flow processes of water migration. Moreover, the influences of various hydrothermal conditions on the mechanical behavior of rocks are frequently overlooked. In this study, a coupled lattice Boltzmann model (LBM) was developed to simulate the freezing process in rocks. The porous structure with complexity and disorder was generated by using a stochastic growth method, and then the Shan-Chen multi-phase model and enthalpy-based phase change model were coupled by introducing a freezing interface force to describe the variation of phase interface. By utilizing the developed model, the ice growth process in rock pores can be well depicted under porous conditions characterized by varying contact angles, porosities, and specific surface areas. Building on this foundation, our work advances the understanding of the complex interaction between thermal dynamics and mechanical processes in periglacial environments, shedding light on the mechanisms of frost weathering and the predictive modeling of rock fracture patterns under varying hydrothermal conditions.
What explains the proportionality of global warming to cumulative carbon emissions?
Authors: Gillett Nathan
Published: March 2024

The constant ratio of global warming to cumulative CO2 emissions underpins the use of remaining carbon budgets as policy tools, and the need to reach net zero CO2 emissions to stabilize global mean temperature. One requirement for this proportionality is that the temperature response to a pulse emission of CO2 is independent of the background emissions scenario, and this property has been explained by a balance between the logarithmic dependence of radiative forcing on CO2 concentration, and the saturation of CO2 sinks at higher CO2 levels. Several studies have argued that this proportionality also arises because heat and carbon are mixed into the ocean by similar physical processes, and this argument was echoed in the Intergovernmental Panel on Climate Change Sixth Assessment Report. However, contrary to this hypothesis, atmosphere-ocean fluxes of heat and carbon evolve very differently to each other in abrupt CO2 increase experiments in five earth system models, and changes in the atmosphere, ocean and land carbon pools all contribute to making warming proportional to cumulative emissions. Moreover, an analytical model only exhibits proportional heat and carbon fluxes and proportional warming to cumulative emissions if the land and atmosphere carbon pools are neglected, among other unrealistic assumptions. These results strongly suggest that this proportionality is not amenable to a simple physical explanation, but rather arises because of the complex interplay of multiple physical and biogeochemical processes.
Radiative closure assessment using A-Train satellite data for the EarthCARE mission
Authors: Qu Zhipeng , Cole Jason , Barker Howard , Kacimi Meriem , Mason Shannon , Hogan Robin , Courtier Ben
Published: March 2024

The EarthCARE mission will perform continuous radiative closure assessment utilizing both 1D and 3D broadband (BB) radiative transfer (RT) models. The radiance and flux calculations from these models will be compared to observations obtained through EarthCARE's Broadband Radiometer (BBR). The inputs for the RT models will be derived from synergistic retrievals of cloud and aerosol properties, facilitated by the Clouds, Aerosol and Precipitation from Multiple Instruments using a Variational Technique (CAPTIVATE) algorithm. In preparation for the EarthCARE launch, this study involves the application of CAPTIVATE to A-Train data, with the resultant cloud, aerosol, and precipitation properties serving as inputs for the RT models. The outcomes of these models will be utilized in a radiative closure assessment, incorporating measurements from the Clouds and the Earth's Radiant Energy System (CERES). The analyses center on discerning differences between 1D and 3D RT calculations, as well as differences between RT calculations and measurements obtained from the CERES.
Ocean chemistry archived in modern evaporites: implications for robust seawater and CO2 reconstructions from Earth’s past
Authors: Jurikova Hana , Bodnar Robert , Branson Oscar , Dumont Matthew , Evans David , Gázquez Fernando , Kirichenko Yana , Lazar Boaz , Liang Mao-Chang , Lowenstein Tim , Sendula Eszter , Voigt Claudia , Xu Chen , Zheng Xinyuan , Rae James
Published: March 2024

The chemical history of seawater provides key information on Earth’s geologic processes and is fundamental for robust CO2 reconstructions. The knowledge of the secular evolution of the oceanic boron isotope budget is particularly important for CO2 reconstruction from boron isotopes. The boron isotope composition of seawater (δ11Bsw) is homogeneous, but varies on multi-million year time scales, given its residence time of approximately 10 million years. To date, the secular evolution of the oceanic boron isotope budget has been difficult to constrain, posing a major uncertainty for boron-based pH and CO2 reconstructions from Earth’s geologic past and critically limiting our understanding of the global biogeochemical cycling of this important element through time. Evaporitic minerals bearing fluid inclusions – and halites in particular – have provided important insights on past variations in major and minor ion composition, and present a highly appealing archive for reconstructing δ11Bsw (as well as other isotopic systems) given their direct origin from seawater. However, the interpretation of their signatures is not straightforward due to the possibility of fractionation during evaporation, crystallisation, and local biogeochemical interactions. Here we present data illuminating the evolution of boron isotopes and various other elements during evaporite formation from laboratory experiments and natural modern evaporitic settings across the globe, accompanied by new analytical developments for high-precision single fluid inclusion measurement using laser ablation. These data enable us to critically evaluate the evaporite archive, paving an avenue to robust seawater and CO2 reconstructions from Earth’s geological past.
Geochemical insights into conditions of vent fluid origin and water-rock interaction over two eruptive cycles at 9° 50´N East Pacific Rise
Authors: McDermott Jill M. , Downing Connor C. , Siverand Jada M. , Bibaj Esmira , Barreyre Thibaut , Fornari Daniel J. , Parnell-Turner Ross , Seewald Jeffrey S. , Reeves Eoghan P. , Syverson Drew D. , Hardisty Dalton S. , Cox Alysia D.
Published: March 2024

Multidisciplinary studies at the 9°50’N East Pacific Rise (EPR) hydrothermal field span three decades and encompass two periods of volcanic activity in 1991-1992 and 2005-2006. Shifts in the pressure and temperature of hydrothermal circulation induced by the magmatic cycle drive changes in the composition of venting fluids. Previous geothermobarometric model approaches used quartz solubility and fluid Cl concentrations to estimate pressure and temperature conditions in the zone where hydrothermal fluids originate [1, 2]. A geothermometer based on dissolved Fe/Mn [3] now provides additional insight on fluid origin temperatures. Consequently, application of an updated geothermobarometric model is possible.We estimate the pressure and temperature conditions of fluid formation at historic high temperature vents in the 9°50’N EPR area between 2018 and 2023 and compare them with time series data since 1991. These calculations focus on six vents that span 7 km north to south along the axial summit trough, including M, Bio9, P, V, L, and L-Hot8 vents.Immediately following eruptions, fluid origin pressures are considerably shallower at Bio9, M, and P vents (25-27 MPa) than during periods of lower magmatic activity (30-35 MPa). Additionally, fluid origin temperatures at the same vents rise from 390-400 °C for 1-2 years after eruptions to 410-430 °C during the periods between eruptions. Despite repeated observation of a continuous warming trend in vent fluid exit temperatures in the years preceding eruptions, fluid origin temperatures are relatively stable at a given vent location over the same time periods. These results support previous assertions that the upflow zone may experience enhanced permeability immediately following an eruption, leading to seawater entrainment, and cooling prior to venting. These inferences are also supported by a significantly greater proportion of radiogenic, seawater-derived Sr isotope input to circulating fluids in the 1-2 years after eruptive events, followed by a shift toward less radiogenic, more basalt-derived Sr isotope signatures.  The vent fluids are presently circulating into the sheeted dikes and attaining maximum depths and temperatures similar to those previously observed leading up to the 2005/2006 eruption. The chemical behavior and formation conditions of these hydrothermal fluids will be tracked through 2025, with the goal to understand the hydrothermal response preceding the next magmatic event. [1] Von Damm (2004) AGU Mono; [2] Fornari et al. (2012) Oceanography; [3] Pester et al. (2011) Geochim. Cosmochim. Acta.
Hydrologic responses to climate change and implications for reservoirs in the source region of the Yangtze River
Authors: Xu Hongmei , Qin Pengcheng , Xia Zhihong , Liu Lüliu , Wang Qiuling , Xiao Chan
Published: March 2024

Understanding the hydrological impacts of climate change is essential for robust and sustainable water management. This study assessed the hydrologic impacts of climate change in the Jinshajiang River basin, the source region of the Yangtze River, using the historical observations and the future hydrologic simulations under two Shared Socioeconomic Pathways (SSP2-4.5 and SSP5-8.5), deriving from a hydrological model. For the historical period, there is an increasing trend in precipitation, evapotranspiration, snowmelt, and consequently an increasing in streamflow in the upstream, whereas a decreased streamflow in the downstream catchment. For future scenarios, a warmer and wetter climate was projected for the basin throughout the 21st century, and correspondingly an overall increase in mean and extreme streamflow, with a larger magnitude in the far future than in the near future, and under SSP5-8.5 than SSP2-4.5. The projected remarkable increase in precipitation cause the transition in changing trend of streamflow compared with the historical period. The projected continuing decline in snowfall and snow water equivalent result in a significant advance and decrease in snowmelt, followed by an earlier and more concentrated peak streamflow in July, especially for the upstream catchment. Ultimately, reservoirs in the basin are expected to gain more inflows, however, with larger variability and more floods and hydrological droughts, which impose potential challenges on reservoir operations. These outcomes indicate the importance of adaptive water resources management in the melting water contributed basin to sustain and enhance its services under global warming.
Early Assessment of SWOT’s Swath-mapping Capabilities over Arctic Sea Ice
Authors: Farrell Sinead L. , Fischer Reint , Duncan Kyle , Yi Donghui , Kuhn John M. , Leuliette Eric , Connor Laurence
Published: March 2024

The routine measurement of sea ice, an essential climate variable, is urgently needed for improving seasonal sea ice forecasting and tracking ocean-ice-atmosphere interactions. Over the last few decades, ocean remote sensing techniques have revealed significant and rapid declines in both the extent and volume of Arctic sea ice, driven by accelerated warming at high northern latitudes. The Surface Water Ocean Topography (SWOT) mission delivers innovative wide-swath Ka-band synthetic aperture radar (SAR) interferometry and coincident Ku-band altimetry and provides, for the first time, swath mapping of sea ice from a space-based system. The novel SWOT technology can be exploited to advance knowledge of sea ice processes and properties. Although SWOT’s latitudinal limit of coverage is 78° N, this is nevertheless sufficient for mapping the seasonal sea ice zone in the Arctic which develops, grows and deforms in winter and typically reaches a maximum in the month of April. SWOT can obtain measurements across ~9-10 million square kilometers of Arctic sea ice in April. It's high-resolution swath-mapping approach captures sea ice surface topography in two dimensions, both along- and across-track. This new capability allows us to determine the areal fraction and shape of individual sea ice floes, map the 2D structure of leads, identify the ice edge location in higher fidelity than has heretofore been possible, and simultaneously measure sea ice height, from which sea ice freeboard and hence thickness may be derived. Here we show the results of our initial assessment of SWOT data collected during the 1-day fast repeat orbit phase. This particular sampling strategy allows us to track individual sea ice floes and derive high resolution estimates of ice drift velocity. SWOT backscatter signatures over sea ice are also used to discriminate between rough sea ice floes and smooth, specular  leads. We evaluate SWOT backscatter using high-resolution measurements of sea ice roughness derived from spatially-coincident ICESat-2 laser altimetry data.  We also show the feasibility of using the 2D swath-mapping capabilities of SWOT in concert with ICESat-2 sea ice height profiles to map the joint floe size-ice thickness distribution. Our results demonstrate the many benefits of swath mapping altimetry for polar sea ice studies.
Hydrological implications of the Chile Megadrought in high mountain basins and lessons for climate adaptation.
Authors: McPhee James , Hernandez Diego , Courard Maria , Mejías Alonso , Tesemma Zelalem , Pietroniro Alain , Pomeroy John
Published: March 2024

La Niña years are historically associated with precipitation deficits in central Chile. However, since the onset of the so-called Chile Megadrought in 2010, the teleconnection between the El Niño-Southern Oscillation phases and the hydroclimate in central Chile has either weakened or disappeared. This study investigates the hydrological response of high mountain watersheds to La Niña (LN) and megadrought conditions (MD) in the Andes of central Chile (30°S – 35°S) through physically-based simulation of processes at the watershed scale. It is shown that during LN years, winters and summers are colder, but spring seasons are warmer, while in MD years the summers are warmer. In addition, the hydrologic response to LN and MD is distinct and amplified during MD in terms of flow deficit.  Simulation results for five snow-dominated basins within the central Andes suggest lower efficiency in the transformation of precipitation to snowmelt flow (-3.7% and 1.6% with respect to the long-term average, for MD and LN, respectively), accompanied by higher evaporation (8.7% and 6.1%) and lower flow (-9.3% and -3.4%) relative to annual precipitation. Also, snow accumulation deficits at the end of winter propagate (-36.2% and -17.7%) with respect to the deficit of solid precipitation (-29.7% and -17.5%) and total precipitation (-26% and -19.3%), and during the MD the duration of snow is shorter compared to LN (-16.3 and -10.6 days). Thus, the key role played by snow processes and their variability in the hydrological response to droughts in central Chile is highlighted. The findings presented here are expected to inform ongoing discussion on adaptation strategies to climate change, as the observed climate during the megadrought (2010-?) is strikingly similar, on average, to GCM projections for this region toward the end of the 21st century.
Reconstructing the coupled Greenland Ice Sheet–climate evolution during the Last Interglacial warm period
Authors: Osman Matt , Tierney Jessica , Lofverstrom Marcus
Published: March 2024

During the Last Interglacial (LIG), approximately 130-118 thousand years ago (ka), the Arctic experienced relative warmth and global sea levels considerably higher than modern.  While this interval is thus considered key for understanding long-term ice–climate feedbacks under warm-state climate conditions, large uncertainties remain surrounding i. the magnitude and spatial expression of LIG global temperature change, ii. the relative contributions of the Antarctic vs. Greenlandic Ice Sheets (GrIS) to LIG sea level rise, and iii. the sensitivity of the GrIS to centennial- to millennial-scale ocean-atmospheric forcing.  Here, we present, to our knowledge, a first attempt at reconstructing the coupled GrIS–climate evolution during the LIG using an internally consistent offline “paleoclimate data assimilation” approach.  Our methodology combines a newly compiled database of nearly 400 chronologically consistent marine geochemical and ice sheet-derived climate-proxy records (spanning 250 sites globally) with recently developed, state-of-the-art transient simulations of the LIG using the coupled Community Earth System Model v2 featuring an interactive Community Ice Sheet Model v2 (CESM2-CISM2).  Our preliminary assimilations suggest LIG peak global mean surface warming of +0.1-0.5˚C (±2 range) above the pre-industrial state, arising from enhanced and widespread (>2-5˚C) high Arctic warming.  Leveraging our CESM2-coupled CISM2 results, we further identify a max GrIS contribution of 2.0 (±0.6) meters of sea level rise equivalent at around 125 ka, nearly ~two millennia after peak LIG climate forcing.  These initial results provide a new proxy-model integration framework for reconciling past GrIS contributions to global sea level rise and benchmark the potential long-term sensitivity of the GrIS to ongoing Arctic warming.