bluuebunny/crossref_metadata_2025 huggingface dataset:
Occurrence of offshore freshened groundwater in the Pearl River Estuary and adjacent continental shelf
Authors: Sheng Chong , Jiao Jiu Jimmy , Luo Xin , Zuo Jinchao , Jia Lei , Cao Jinhe
Published: February 2023

The ~100 ka Milankovitch cycles during the Quaternary generated a significant sea level fluctuation with the lowest sea level of 120 m below the present level at the Last Glacial Maximum in the coastal areas. The large-river deltaic estuaries (LDEs), due to the proximity to sea environments, therefore, may archive the periodical transgression and regression information. During delta-front progradation, the sedimentation process is usually dominated by coarse-grained fluvial deposits, and the river networks extend further to the sea, whereas during marine transgressions, fine-grained marine sediments dominated by clay and silt are deposited. From a hydrogeological perspective, this geologic scenario leads to the formation of multi-layered aquifer-aquitard systems in current continental shelves. Therefore, we hypothesize that the offshore freshened groundwater (OFG) may be widely distributed in the LDEs and their adjacent continental shelves.Pearl River is the second largest river in China in terms of water discharge, and the accompanying subaqueous paleo delta extends to the slope at the northern margin of the South China Sea with an offshore distance of 200 km. To address the key scientific issues raised in OFG of the LDEs and their adjacent shelves, we have studied the offshore hydrogeology, marine seismic profiles, and porewater hydrogeochemistry in the subaqueous paleo-delta and adjacent shelf of the Pearl River. A total of 31 offshore boreholes with high-resolution porewater geochemistry profiles have been obtained in this area. These boreholes have led to an identification of a large and unexpected OFG with a volume of ~523.3×109 m3, with the freshwater (salinity < 1 PSU) extending as far as 55 km offshore. The total OFG volume is twice of the annual discharge of the Pearl River. The distribution of the OFG is closely related to the morphology of the subaqueous paleo-delta of the Pearl River, where the buried paleochannel system is widely distributed. The values of δ2H and δ18O together with the chlorinity of the OFG in the Pearl River Estuary and adjacent shelf clearly reveal its meteoric origins. Besides, the systematic analysis of water quality indices including major ions, nutrients, heavy metals, and trace elements indicates that the OFG can be used as potable water with minor treatment or raw water source for effective desalination. Hotspots of OFG in the LDEs and their adjacent shelves, likely a global phenomenon, have a great potential for useful water resources for highly urbanized coastal areas suffering from water shortage.
Relationship between Kuroshio variation east of Taiwan and the Kuroshio intrusion west of the Luzon Strait during 1998-2013
Authors: Ho Chung-Ru , Tseng Yu-Hao
Published: February 2023

Although the issue of the global warming hiatus during 1998-2013 is still under debate, the surface velocity of the Kuroshio has been shown to decrease east of Taiwan but increase east of Luzon during the global warm hiatus period. In this study, we revealed a significant increase in cut-off events on the Kuroshio main path east of Taiwan during the hiatus period. This is probably related to the interaction between the weakening Kuroshio off the east of Taiwan and the westward propagation of the mesoscale cyclone eddy from the western Pacific Ocean. The cut-off event of the main path of the Kuroshio is determined using the momentum ratio of the Kuroshio to the eddy. If the ratio is less than one, the eddy dominates and the Kuroshio is cut off. Sea surface velocities derived from satellite altimeter data for these events in the Kuroshio region east of Taiwan and the Kuroshio intrusion region west of the Luzon Strait were then analyzed by empirical orthogonal functions. The results showed that the Kuroshio intrusion to the west of the Luzon Strait increased after an average of about one month after the main Kuroshio off east of Taiwan was cut off. This appears to be reverse feedback from the Kuroshio downstream to upstream.
Towards hazard, vulnerability, and resilience-based assessment of spatial-temporal trends, patterns, and disparities in drought risk
Authors: Sajjad Muhammad
Published: February 2023

While droughts pose notable socio-economic impacts on societies, most of the related research has focused on droughts as a hazard. It is imperative to think beyond the in-practice approaches to provide more integrated tools and solutions for effective drought risk management. In connection with this, the present study introduces an integrated drought risk assessment framework to evaluate multi-dimensional high-resolution drought risk.  A Drought Risk Index (DRI) is computed at the tehsil level in Pakistan — a sub-administrative division under the district government where localized planning and decision-making take place. The DRI is based on Drought Hazard (DHI), Drought Vulnerability (DVI), and Drought Resilience (DReI) indices, which are systematically computed using a diverse range of data (i.e., the standardized precipitation evapotranspiration, soil, land-use land-cover, night-time light, population, and socio-economic variables among others). Furthermore, spatial modelling techniques (i.e., spatial autocorrelation and the Local Indicators of Spatial Association) are applied to locate and highlight statistically significant risk regions. In addition, this preliminary effort engages the state-of-the-art space-time pattern mining technique for the simultaneous spatial-temporal dynamics investigation of droughts. Pakistan exhibits a large geographical heterogeneity in terms of drought risk. Comparatively, the regions from Balochistan province are at the highest risk followed by Sindh. Notably, approximately one-third of Pakistan is identified as the hot spot with the highest drought risk (95% confidence). To an agrarian nation with ~220 million people and among the top 10 most vulnerable countries to climate change impacts, this situation ascertains grave threats under global warming. The comprehensive results from this study are expected to provide important and useful insights to prepare for drought mitigation, adaptation, and systematic impact evaluation in the face of environmental changes.
Estimation of broadband source time functions of seismic slow earthquakes
Authors: Takemura Shunsuke , Emoto Kentaro , Yabe Suguru
Published: February 2023

We propose a method for estimating broadband source time functions of seismic slow earthquakes, which can reproduce observed seismograms at both bands of very low frequency earthquake and tectonic tremor. In our method, we assume the broadband characteristics of seismic slow earthquakes (e.g., Ide et al., 2008; Masuda et al., 2020).In our method, first, we estimated source time functions of very low frequency earthquakes using filtered seismograms at frequencies below 0.1 Hz via the simulated annealing method (e.g., Takemura et al., 2022ab). To achieve broadband source time function, we added random temporal fluctuations into obtained smooth source time function of very low frequency earthquakes. This approach is similar to previous studies for regular earthquakes (e.g., Koyama, 1985; Hisada, 2000). We assumed that fluctuations of source time function can be characterized by a von-Kármán autocorrelation function. A decay rate parameter of a von-Kármán autocorrelation function can model various decay rates at high-frequency ranges.We confirmed the validity of our method using synthetic seismograms, which were made from Green’s function datasets using a 1D velocity model and the Brownian-walk source time function model (e.g., Ide, 2008; Ide & Maury, 2018). Our estimation well reproduced target seismograms of synthetic seismic slow earthquakes.In our presentation, we will introduce our methodology and applications at shallow plate boundary in Nankai.
Deep Learning-Based Vegetation Extraction and Vegetation Change Monitoring by using Very High-Resolution Satellite Imagery
Authors: Javed Aisha , Yun Yerin , Hur Jaewon , Yeom Junho , Han Youkyung
Published: February 2023

Vegetations play an important role in the management of physical activities and the public health of urban residents. However, with the rapid urbanization in the world, vegetation regions are changing constantly. In order to prevent the decrease in vegetation areas, constant vegetation monitoring is required. In this study, we performed vegetation extraction and vegetation change monitoring in very high-resolution (VHR) satellite imagery through deep learning-based techniques. To this end, two deep learning networks (i.e., DeepLabV3-plus, and deeply supervised image fusion network (DSIFN)) were used for vegetation extraction and change detection, respectively. Firstly, the two networks were trained on the two datasets each for their respective purpose. Then, a DSIFN was tested to detect all the changes occurring in VHR bitemporal satellite images. Moreover, the binary vegetation maps from bitemporal images were independently generated by using DeepLabv3-plus. Later, the vegetation maps and the change detection result were combined to figure out the change tendency related to vegetation. To show the effectiveness of the proposed method, an accuracy assessment was carried out. The proposed method can be used to determine the amount of change occurring within a period in the vegetation of urban areas.
Seismic and aseismic slip on the Central Range fault associated with the 2013 Mw 6.3 Ruisui earthquake (Taiwan)
Authors: Lin Hsiao-Fan , Canitano Alexandre , Hsu Yu-Fang , Gualandi Adriano , Hsu Ya-Ju , Huang Hsin-Hua , Lee Hsin-Ming
Published: February 2023

The 2013 Ruisui earthquake is the first unequivocal evidence of the seismicity activity of the Central Range Fault (CRF) in the central Longitudinal Valley in Taiwan, and hence reveals the existence of aseismic slip on the CRF. The finite-fault coseismic model obtained from the Bayesian joint inversion of GNSS and strainmeter data suggests that the rupture area is mainly distributed on a 26 km × 22 km fault plane located at the depth of 3 to 19 km with a maximum slip of about 0.5 m. A variational Bayesian independent component analysis (vbICA) technique is applied to the detrended GNSS time series to extract postseismic deformations in the near-source region. Although the afterslip distribution was not able to be well inverted due to the lack of observation on the western side of the fault plane, using rate-and-state friction rheology to simulate the surface displacements generated by the stress-driven afterslip model, we infer for the first time the existence of a shallow velocity-strengthening region on the CRF, which is capable of hosting and sustaining aseismic transient deformations over months.
Origin of low-tropospheric potential vorticity in Mediterranean cyclones
Authors: Scherrmann Alexander , Flaounas Emmanouil , Wernli Heini
Published: February 2023

Mediterranean cyclones are extratropical cyclones, typically of smaller size and weaker intensity than other cyclones that develop over the main open ocean storm tracks. Nevertheless, Mediterranean cyclones can attain high intensities, even comparable to the ones of tropical cyclones, and thus cause large socio-economic impacts in the densely populated coasts of the region. After cyclogenesis takes place, a large variety of processes are involved in the cyclone’s development, contributing with positive and negative potential vorticity (PV) changes to the lower-tropospheric PV anomalies in the cyclone center. Although the diabatic processes that produce these PV anomalies in Mediterranean cyclones are known, it is still an open question whether they occur locally within the cyclone itself or remotely in the environment (e.g., near high orography) with a subsequent transport of high-PV air into the cyclone center. This study introduces a Lagrangian method to determine the origin of the lower-tropospheric PV anomaly, which is applied climatologically to ERA5 reanalysis and to 12 monthly simulations, performed with the IFS model. We define and quantify so-called "cyclonic" and "environmental" PV and find that the main part of the lower-tropospheric PV anomaly (60%) is produced within the cyclone, shortly prior (-12 h) to the cyclones’ mature stage. Nevertheless, in 19.5% of the cyclones the environmental PV production near the mountains surrounding the Mediterranean basin plays a significant role in forming the low-tropospheric PV anomaly, and therefore in determining the intensity of these cyclones. The analysis of PV tendencies from the IFS simulations reveals that the major PV production inside the cyclone is typically due to convection and microphysics, whereas convection and turbulent momentum tendencies evoke most of the positive PV changes in the environment.
Object detection and classification applying AI (computer vision) to underwater images
Authors: Son Young-Tae , Jin Sang-Yeop , Kang Tae-Soon
Published: February 2023

Visual AI (artificial Intelligence) YOLOv5 algorithm was used in order to detect marine organisms from underwater images, and the test results showed an average high detection rate (>90%). As performance indicators of the AI model, both precision and recall showed very good performance, exceeding 0.95. So as to minimize the change in object detection performance according to the variation of underwater conditions, image correction was conducted, and more objects could be detected after image correction.In order to determine which species the object detected in the video or image corresponds to, the performance was evaluated by AI learning classification model (YOLO-Classification), which is a deep learning algorithm (approximately 3% accuracy improved after image correction). We tried to identify the taxonomic species of organisms using deep learning, and although the number of target species was small, we achieved a classification accuracy of about 80% or more based on the data collected so far.High-quality image DB data of the target species have to be established from a long-term perspective in order to accurately classify object (fish) species, and imaged taken from various angles of the target species must be collected simultaneously improve performance. As a prerequisite for measuring the size of an object detected in an image, MDE (Monocular Depth Estimation), a deep learning algorithm for estimating the depth of a mono camera image, was applied and the distance from a certain reference point was calculated with the MiDAS v3 algorithm. As a result of the MiDas v3 algorithm test, the excessive error has been reduced compared to before application and the distance measurement accuracy of up to 2m, which is longer than the guide stick length, has been obtained.
Trends in evaporative water demands in the Tibetan Plateau and its implication for hydroclimatic change
Authors: Xu Shiqin
Published: February 2023

The Tibetan Plateau functions as the Asian water tower. It is highly sensitive to climate change and is warming faster than low-lying areas. The snow-melt dynamics are being perturbed, precipitation and evaporation patterns are shifting, and permafrost is degrading. Climate change therefore threatens the basin water supply as well as agriculture, hydropower, and industry which depend on it. The scientific questions we emphasized here are: (i) How evaporative water demand (EWD) changes in space and time during the current decades across the Asian water tower? (ii) Which driver should be attributable for the change? (iii) How EWD change informs the potential alteration of surface water resources in the Asian water tower? The expected outcomes would improve our understanding of the hydroclimatic change in the Asian water tower as well as other high-water yielding mountainous regions worldwide. 
A novel machine learning national model for diffuse source total phosphorus concentrations in streams
Authors: Kronvang Brian , Windolf Jørgen , Tornberg Henrik , Rolighed Jonas , Larsen Søren
Published: February 2023

Data on the diffuse source annual flow weighted total phosphorus (TP) concentrations from 349 Danish streams draining smaller catchments (< 50 km2) for the period 1990-2019 were used for developing a model in machine learning software (DataRobot version 6.2; DataRobot Inc. Boston MA, USA). The developed diffuse source TP-concentration model will substitute an older model that have been in place to calculate P-loadings to Danish estuaries from ungauged areas. A total of 207 streams with 3,144 annual observations of flow-weighted TP concentrations together with information on 19 explanatory variables was entered into the DataRobot software. DataRobot divides the input data into three layers: Training dataset (64%), validation dataset (16%) and hold out dataset (20%). Thereafter, DataRobot conducts a five-layer cross-validation and tests among 72 different model types before suggesting final best solutions.In this case, the TP-concentration model was developed as an ‘eXtreme Gradient Boosted Trees Regressor with early stopping’ as suggested by the DataRobot software to be superior for modelling the annual flow-weighted TP concentration based on 13 explanatory variables. The most influencing explanatory variables in the final model are: 1) tile drainage in the catchments; 2) ; 3) period (two periods with different sampling regimes; 4) proportion of agricultural land; 5) importance of bank erosion; 6) deviation of annual runoff from long-term mean. The final TP-concentration model has a R2=0.69 for the training dataset, R2 = 0.71 for the validation dataset and R2 = 0.67 for the hold out dataset.A validation of the new machine learning TP-concentration model on 142 independent streams with 1,261 annual observations was conducted to investigate the uncertainty of the model simulations. The validation showed the TP-concentration model to have a high explanatory power (R2=0.60) and with a very good simulation performance in the nine Danish georegions, as well as for the 30 year long time series of data. An application of the model for calculating flow-weighted TP-concentrations within nearly 3,200 catchment polygons (ID15’s) covering the Danish land area showed that the new developed machine learning TP-model is a valuable tool both for calculation of TP-loadings from ungauged areas to lakes and coastal waters as well as for linking catchment pressures to stream ecological status.   
Evaluation of water quality change and sludge generation according to hydrogen peroxide treatment during lime neutralization
Authors: Cheong YoungWook , Cho Dong-Wan , Yim Giljae , Jang Jeong-Yun
Published: February 2023

This study investigated the effect of hydrogen peroxide treatment on the removal pH for Fe, Al, and Mn and sludge production in the lime neutralization process. In the laboratory, the AMD collected from the coal mine was oxidized with 5% H2O2, and then neutralized to pH 3, 5, 7 and 9, respectively, with 20% lime slurry. In the control experiment, the same neutralization experiment was performed without H2O2 treatment. During the experiment, the supernatant was measured for pH and Eh and analyzed for Fe, Al, Mn, Ca and SO42- ions. Simple neutralization without H2O2 treatment up to pH 8 resulted in almost 100% Fe (<0.3 mg/L), Al (<0.3 mg/L), and Mn (2 mg/L) removal. Neutralization with pre H2O2 treatment also eliminated Fe and Al at pH 6 to the same removal efficiencies and Mn remained at 15 mg/L. The use of lime was 17% less and the weight of sludge was 35% less, and the volume of sludge decreased by 47%. As a result of evaluating the pH-Eh-Fe diagram for hydrogen peroxide/lime neutralization facilities, it was evaluated that Fe could be removed at pH 5-6. It can be concluded that neutralizing up to pH 6 after oxidation effectively minimizes the amount of sludge generated by removing Fe and Al and suppressing gypsum production.
Increased glacier melt enhances future extreme floods in the southern Tibetan Plateau
Authors: Sun He , Yao Tandong , Su Fengge
Published: February 2023

Mountainous areas on the Tibetan Plateau (TP) are of particular hydrological concern as topography and atmospheric conditions can result in large and sudden floods, and pose critical threats to water-related safety and sustainability in neighboring countries. The Yarlung Zangbo (YZ) river basin is the largest river basin on the southern TP, but the ways in which flood discharges in this basin will evolve under 21st-century climate change and the effect of precipitation extremes and glacier melt remain unclear. Here, we comprehensively quantify the future evolution of extreme flood frequency and intensity under 21st-century climate change, and determine the predominant drivers of flood changes in the YZ basin. We show that total runoff is projected to increase owing to continued wetting throughout the 21st century under two different shared socioeconomic pathways (SSPs) in the YZ basin. Both the frequency and intensity of flood extremes are projected to increase under both SSPs, primarily driven by enhanced total days and magnitude when daily precipitation estimates > 95th percentile. Glacier melt is projected to enhance the intensity and frequency of extreme floods by 12%–23% under both SSPs. This study aims to close the knowledge gap regarding future flood risks in the TP’s rainfall- or meltwater-impacted basins.
Incorporating agricultural practices in digital mapping improves prediction of cropland soil organic carbon content: the case of the Tuojiang River Basin
Authors: Wang Qi , Le Noë Julia , Li Qiquan , Lan Ting , Gao Xuesong , Deng Ouping , Li Yang
Published: February 2023

Cropland soil organic carbon (SOC) is key to maintain soil fertility for plant growth and mitigating climate change by storing considerable amount of organic carbon. Accurate mapping of cropland SOC is essential for improving soil management in agriculture and assessing the potential of different strategies aiming at enhancing regional carbon sequestration. Digital Soil Mapping represents an intermediate approach between labor-intensive soil measurement survey and uncertain SOC modelling. However, most of the widely-used environmental predictors employed in current cropland SOC mapping describe the natural conditions. Indeed, anthropogenic activities, particularly agricultural management practices have profound impacts on agricultural soils, but have rarely been considered in previous research on SOC digital mapping.Here, we filled that gap by incorporating within the Extreme Gradient Boosting (XGBoost) model several key cropland management practices including carbon input, length of cultivation, and irrigation as management covariates, together with natural variables in order to predict the spatial distribution of cropland SOC in a traditional agricultural area in the Tuojiang River Basin, China. This approach revealed the dominant role of carbon input in explaining SOC variation in this intensively cultivated areas, followed by elevation and soil pH. Adding cropland management practices to natural variables improved prediction accuracy, with the coefficient of determination (R2), the root mean squared error (RMSE) and Lin’s Concordance Correlation Coefficient (LCCC) improving by 16.67%, 17.75% and 5.62%, respectively. Our research highlights the necessity of considering cropland management practices alongside environmental predictors in order to provide more reliable prediction of cropland SOC. We conclude that the construction of spatio-temporal database of agricultural management practices is a research priority as it has a very strong potential, not only to provide accurate digital SOC maps when incorporated within XGBoost model, but also to better initialize the SOC stocks in process-oriented model, such as Dynamic Vegetation Models and Earth System Models.
Extremes in river flood hydrology: making Black Swans grey
Authors: Viglione Alberto
Published: February 2023

Black Swans in river flood hydrology are unexpected events that surprise flood managers and citizens, causing massive impacts when they do occur, but that appear to be more predictable in retrospect, after their occurrence. My talk aims at showing how black swans in river flood hydrology can "be made grey", i.e. can be anticipated to a certain degree, in probabilistic terms, and/or made less impactful, by (1) expanding information on flood probabilities by gathering data on floods occurred in other places and at other times; (2) understanding the mechanisms causing heavy tails in flood frequency distributions; (3) understanding the mechanisms causing river flood changes in time; (4) accounting for uncertainties in data, models and flood frequency estimates; (5) accounting for the possible dynamics of coupled human-water systems; and (6) coupling the classical top-down approach to hydrological risk assessment based on predictive modelling with a bottom-up approach that is centered on robustness and resilience.
Non-destructive geophysical damage analysis of medieval plaster in the cloister of the St. Petri Cathedral Schleswig (Germany)
Authors: Esel Yunus , Erkul Ercan , Schulte-Kortnack Detlef , Leonhardt Christian , Heller Julika , Meier Thomas
Published: February 2023

Buildings that have existed for centuries undergo structural changes over time due to variations in use. In addition, many structures are severely damaged for example by moisture intrusion. To determine the distribution of moisture in the structure, they are often examined pointwise by core sampling. In addition to invasive methods, non-destructive methods may be applied to obtain three-dimensional hints on the moisture distribution with structures of interest.             The purpose of this paper is to show that non-destructive determination of moisture distribution is possible by using and combining geophysical measurement methods such as infrared thermography (IR), ultrasound (US) and ground penetrating radar (GPR). There are examples for the combination of these methods for non-destructive examination, but it is not yet commonly applied in the field of restoration and conservation of historic buildings.             We present results of geophysical investigations of medieval wall paintings in the cloister of the cathedral in Schleswig (Federal State Schleswig-Holstein, Northern Germany) in the framework of a project funded by the German Federal Foundation for the Environment (Deutsche Bundesstiftung Umwelt - DBU). In the cloister, large-scale alterations of the medieval red-line paintings occurred due to gypsum deposits and a shellac coating. In order to quantify the material properties of a vault section (yoke) in the cloister during the restoration ultrasound surface wave measurements, passive and active thermography and ground penetrating radar measurements were carried out. Repeating measurements at intervals of several months made it possible to evaluate the effectiveness of the test treatments by different solvents to remove the shellac as well as the gypsum deposits. In addition, our results from the passive thermography measurements show that in one section a defect in the horizontal barrier could be responsible for moisture ingress and associated damage. The radargrams recorded in this area confirm that a significant change in reflection amplitudes is present in the areas of increased moisture.
Highly Asymmetric Seismicity in a System of Tectonic Extension and Hydrothermal Venting at the Mohn-Knipovich Ridge Bend
Authors: Pilot Matthias , Lien Marie Eide , Schlindwein Vera , Ottemoeller Lars , Barreyre Thibaut
Published: February 2023

In recent years hydrothermal vent systems were found in unexpectedly high abundance along ultraslow spreading ridges, despite their overall decreased magma supply. Thin oceanic crust and resulting shallow heat sources can drive hydrothermal fluid circulation and detachment faults can act as fluid pathways, resulting in e.g., serpentinization of the oceanic crust. So far, no long-term recording of seismicity around hydrothermal vent systems along ultraslow spreading ridges have been reported. Here, we present results from a ~1-year local Ocean Bottom Seismometer deployment between 2019 - 2020 at Loki’s Castle hydrothermal vent field (LCVF) along the Arctic Mid Ocean Ridge. LCVF is located at a water depth of ~2500m on top of the axial volcanic ridge (AVR) at the Mohn-Knipovich Ridge bend where spreading is highly asymmetric from west to east.For the processing we use a combination of an automatic event detection algorithm (Lassie), a deep-learning phase picking model (PhaseNet) and partial manual re-evaluation of phase picks. Additionally, selected clusters of events are cross-correlated and relocated using hypoDD. The resulting earthquake catalogue consists of a total of 12368 events with 6719 manually re-evaluated and 5649 automatically picked events.From the results we see that most of the plate divergence at the Mohn-Knipovich Ridge bend is accommodated by a young detachment fault west of the AVR. Most of the seismicity occurs between depths of ~2-8km in a bended band that steepens up to 70° with depth and follows the local topography. However, the described detachment fault differs from reported mature detachment faults at the Mid-Atlantic Ridge or Southwest Indian Ridge. Within the footwall we observe episodical, clustered seismicity with extensional faulting mechanisms, indicating that the detachment could be cross-cut by normal faults. Along strike, the seismicity of the fault plane appears highly heterogeneous, with the central part showing only sparse seismicity at depths below 3km while other segments show episodical shallow seismicity. Towards LCVF seismicity below the AVR increases and the maximum depth of earthquakes shallows by about ~2km. This could indicate the presence of a shallow heat source below LCVF as a driving factor for the hydrothermal circulation.
How to deal with spectral interferences when measuring water stable isotopes of plants?
Authors: Orlowski Natalie , Wengeler Lena , Herbstritt Barbara
Published: February 2023

Nowadays, a wide range of water extraction/vapor equilibration techniques for obtaining soil and plant water isotopic composition (δ18O and δ2H) is applied by various ecohydrological disciplines. Here, researchers need to rely on accurate and precise measurements of water isotope ratios for tracing water movement through the critical zone. Previous research has shown that utilizing isotope ratio infrared spectroscopy (IRIS) to analyze water or vapor samples containing co-extracted/-equilibrated organic contaminants (e.g., methanol, ethanol) has the potential to result in significant inaccuracies through spectral interferences. However, the scientific community and the manufacturers have not effectively addressed the inaccuracies caused by organic contaminants. While some hardware solutions for combusting organics as well as some software solutions exist for spectral interference detection during liquid water IRIS analysis, limited tools exist for the post-correction of direct vapor-mode IRIS data e.g., from in-situ water vapor measurements or from the direct water vapor equilibration laser spectrometry method (DVE-LS).For our study, we applied three different water extraction and vapor equilibration techniques (i.e., DVE-LS, in-situ water vapor measurements and cryogenic vacuum extraction) to four types of vegetables (cauliflower, celery root, kohlrabi and potatoes). We investigated how co-extracted organic contaminants (i.e., methanol and ethanol) via the different methods affect the isotopic ratios between liquid and vapor CRDS measurements of our vegetable samples. Through applying different CRDS instrument-specific post-correction options, we could reduce isotopic discrepancies and maximize the accuracy and precision of CRDS measurements from vegetables.We could show that all vegetables produced species-specific different amounts of organic contaminants, which affected the isotope ratios obtained via the different extraction or vapor equilibration techniques in different ways. Clear relationships between DVE-LS samples and spectral parameters indicated co-equilibrated contaminants which we used for a technique-specific ‘organics-correction’. Whereas, results obtained from in-situ water vapor measurements were the least affected by organic contaminants and showed the smallest data spread. Those were also comparable to results from cryogenic vacuum extraction for some type of vegetables.Our study underlines the importance and necessity of plant water vapor isotope data post-correction and highlights the need for a definitive and general protocol in order to prevent ill-founded ecohydrological data interpretations.
Automatic Sand Dune Detection and Classification Framework Using Remote Sensing Images
Authors: Tang Yingfu , Wang Zhongjing
Published: February 2023

Dune field landscape patterns serve as an important signs of aeolian processes, such as wind conditions, sediment supply, and so on. A novel framework was proposed and evaluated for automatic dune detection and classification with remotely sensed images. The framework consists of two main steps: (1) The first step is to detect sand dunes from remote sensing images by SandUnet, which is firstly proposed in this paper. SandUnet, a Convolutional Neural Network (CNN), has a similar network structure with Attention U-net but modifies its attention gate module. In SandUnet, the input signals' information is not compressed as in the Attention U-net, therefore, the nuanced color and texture information of dunes are preserved. This paper demonstrated that SandUnet has better detection accuracy than other popular CNNs such as FCN, U-net, U-net++, and Attention U-net. (2) The second step is to compute the image similarity scores through MobileNet between each dune detection result image and the representative images of 6 different types of dunes. Then, each dune detection result image is classified into a dune type automatically. This paper applied the proposed framework to Taklimkan Desert in China. The average classification accuracy rate is around 80%, which proves the usefulness of this framework in automatic, no-cost, and accurate sand dune classification.
Anisotropy of out-of-phase magnetic susceptibility in titanomagnetite-bearing rocks due to weak field hysteresis
Authors: Hrouda Frantisek , Jezek Josef , Chadima Martin
Published: February 2023

Magnetic susceptibility (both in-phase, ipMS, and out-of-phase, opMS, components) and its anisotropy were investigated in artificial specimens with pure synthetic magnetite and in rocks with titanomagnetite with variable Ti-content reaching XUsp = 0.6 of ulvospinel end member. The opMS of pure magnetite is in its absolute values three orders lower than the ipMS. The phase angle is then lower than 0.2° in absolute values, which is mostly lower than the sensitivity of phase angle determination. Consequently, the opMS can be considered effective zero. In low-Ti titanomagnetite (XUsp~0.2), the intensity of the ipMS variation with field is very low, hardly reaching 1% of the initial value. In high-Ti titanomagnetite (XUsp~0.6), the intensity of ipMS variation is relatively strong reaching 50% of the initial value and that of opMS variation is even much stronger reaching multiples of the initial value.In artificial specimens with magnetite, the opMS is isotropic from the statistical point of view as indicated by the values of the F-statistics and by confidence angles. In titanomagnetite-bearing rocks, the opAMS ellipsoids resemble the ipAMS ellipsoids, the degree of opAMS being significantly higher than that of ipAMS. The principal directions of ipAMS and opAMS are related closely in specimens with high-Ti titanomagnetites and only poorly in specimens with low-Ti titanomagnetites. In specimens with high-Ti titanomagnetites, there is a linear and very strong (R2 = 0.9433) correlation between the degree of ipAMS and root squared degree of opAMS.The results of the present research are mainly applicable to the rocks whose magnetism is dominantly carried by titanomagnetite and pure magnetite. The opAMS indicates solely the titanomagnetite fabric unaffected by magnetite whose fabric may often originate in different conditions or in different time.
Acceleration of Suprathermal protons near an Interplanetary Shock
Authors: Yang Liu , Heidrich-Meisner Verena , Berger Lars , Wimmer-Schweingruber Robert , Wang Linghua , He Jiansen , Zhu Xingyu , Duan Die , Kollhoff Alexander , Pacheco Daniel , Kühl Patrick , Xu Zigong , Keilbach Duncan , Rodríguez-Pacheco Javier , Ho George
Published: February 2023

Context. Interplanetary collisionless shocks are known to be sources of energetic charged particles up to hundreds of MeV. However, the underlying acceleration mechanisms are still under debate.Aims. We determine the properties of suprathermal protons accelerated by the interplanetary shock on 2021 November 3 with the unprecedented high-resolution measurements by the SupraThermal Electron Proton sensor of the Energetic Particle Detector onboard the Solar Orbiter spacecraft, in order to constrain the potential shock acceleration mechanisms.Methods. We first reconstruct the pitch-angle distributions (PADs) of suprathermal protons in the solar wind frame. Then, we study the evolution of the PADs, flux temporal profile and velocity distribution function of this proton population close to the shock and compare the observations to theoretical predictions.Results. We find that the suprathermal proton fluxes peak ∼12 to ∼24 seconds before the shock in the upstream region. The proton fluxes rapidly decrease by ∼50% in a thin layer (∼8000 km) adjacent to the shock in the downstream region and become constant further downstream. Furthermore, the proton velocity distribution functions in the upstream (downstream) region fit to a double power law, f (v) ∼ v−γ, at ∼1000 − 3600 km s−1, with a γ of ∼3.4 ± 0.2 (∼4.3 ± 0.7) at velocities (v) below a break at ∼1800 ± 100 km s−1 (∼1600 ± 200 km s−1) and a γ of ∼5.8 ± 0.3 (∼5.8 ± 0.2) at velocities above. These indices are all smaller than predicted by first-order Fermi acceleration. In addition, the proton PADs show anisotropies in the direction away from the shock in the close upstream region and become nearly isotropic further upstream, while downstream of the shock, they show a clear tendency of anisotropies towards 90◦ PA.Conclusions. These results suggest that the acceleration of suprathermal protons at interplanetary shocks are dynamic on a time scale of ∼10 seconds, i.e., few proton gyro-periods. Furthermore, shock drift acceleration likely plays an important role in accelerating these suprathermal protons.
A view of 3D variability of atmospheric methane over India using MIROC4-ACTM simulations
Authors: shikha Deep , Dey Sagnik , K. Patra Prabir
Published: February 2023

In this study, we examine a maximum of 13 years (2009-2021) of the observational datasets of columnar dry-air mole fractions of methane (XCH4), from the Greenhouse gases Observation SATellite (GOSAT) GOSAT-1 (2009-2021) on board the IBUKI satellite and vertical profiles of CH4 from the Atmospheric Infrared Sounder (AIRS) on board AQUA satellite. We also use the XCH4 and vertical distributions over the Indian subcontinent from the JAMSTEC’s MIROC4 atmospheric chemistry transport model (ACTM) from 2009-2021, after convolution with GOSAT-1 and AIRS a priori profiles and averaging kernels. A comparison of observed and modeled CH4 and XCH4 reveals that MIROC4-ACTM provides explicit insights into the spatio-temporal variability of atmospheric methane over the Indian region. Global CH4  emission inventory EDGARv7.0 reports a total of ~30 Mt of anthropogenic emissions in India in 2020 while GAINS emissions stand at ~33Mt for the same year. The ACTM simulations from this study are also examined to retrieve preliminary information on the quality of these constructed bottom-up fluxes of methane (EDGAR and GAINS).      Our time series analysis of GOSAT-1 shows the annual mean XCH4 has increased by 100 ppb from 2009 to 2021 over the Indian subcontinent, compared to 85 ppb globally in the latitude band of 6.25 °N-41.25 °N. Observations from both AIRS and GOSAT-1 show distinct seasonality in the vertical profiles of CH4 and XCH4 over the entire region, respectively. Seasonality in the CH4  concentration over India in boundary layer heights (>850 hPa) is affected majorly by the local emission strengths while in the middle (400- 600 hPa) and upper (< 200 hPa) troposphere it is governed by the convective transport of surface emissions signals and redistribution in the monsoon winds in the upper troposphere. GOSAT-1 shows highest XCH4 of ~1900 ppb (2021) in northern India (North of 20° N) in winter season  (November) while AIRS shows highest CH4 ~1910 ppb in summer month of May at 200 hPa for the same year. Based on the findings from the vertical (AIRS) and total column (GOSAT-1) distribution of CH4, our analysis suggests that 3D variability of CH4 over the entire Indian region is governed by a diverse spread of surface emissions and global monsoon divergent wind circulations.  Through this study, the reasons for these observed patterns of CH4 are explored in light of forward model results using an ACTM by combining and comparing the strengths of AIRS and GOSAT-1.
Building a robust Middle Cambrian astrochronology using deep-water rhythmites and parsequences in the Marjum Formation of western North America
Authors: Pas Damien , Jamart Valentin , Wouters Sébastien , Da Silva Anne-Christine , Elrick Maya , Spangenberg Jorge , Adatte Thierry , Thaureau Marion
Published: February 2023

During the Middle Cambrian, western Utah (USA) occupied the deepest part of the House Range embayment along the western edge of North America and accumulated deep-water facies dominated by cm-scale, cyclically interbedded limestone-marl layers (‘rhythmites’) of the Marjum Formation. The studied section is ~500 m thick and spans the lower Drumian-lower Guzhangian. The rhythmites (cm-scale) are packaged into repeated 2-5 m-thick parasequences and larger scale eustatic sequences both characterized by more carbonate-dominated rhythmites alternating with more siliciclastic-dominated rhythmites. Previous studies of the Marjum rhythmites suggest millennial-scale interpretation for the cm-scale rhythmites, corresponding to wetter vs drier climate oscillations influencing the relative abundance of siliciclastic vs carbonate accumulation in the deep-water setting (Elrick and Hinnov, 1996; Elrick and Hinnov, 2007).We conducted a high-resolution study of a representative 35 m-thick interval of the Marjum Formation to build a floating astrochronology assuming the meter-scale parasequences represent orbital-scale frequencies modulated by the larger scale sequences (based on biostratigraphically controlled sediment accumulation rates). To capture orbital-scale frequencies and to avoid aliasing related to millennial-scale limestone-marl lithological changes, 350 rock samples were collected at minimum 10-cm-interval exclusively in the limestone layers of rhythmite couplets. Major elements (e.g., Ti, Al, K, Si), TOC and δ13C were measured on each sample to infer on paleoenvironmental and paleoclimatic conditions. To estimate the duration of the sampled interval, multiple spectral techniques will be applied on the paleoclimatic proxies using amplitude modulation, frequency ratio as well as the 405 kyr long eccentricity as a starting point for the calibration of the time scale. Having an astronomically calibrated time scale for this interval will provide 1) independent evidence assessing the millennial-scale paleoclimatic origin of the cm-scale rhythmites, and 2) refine the Cambrian time scale to better constraint the origin and rate of the Cambrian explosion events.Elrick, M. and Hinnov, L.A., 1996. Millennial-scale climate origins for stratification in Cambrian and Devonian deep-water rhythmites, western USA. Palaeogeography, Palaeoclimatology, Palaeoecology, 123(1-4): 353-372.Elrick, M. and Hinnov, L.A., 2007. Millennial-scale paleoclimate cycles recorded in widespread Palaeozoic deeper water rhythmites of North America. Palaeogeography, Palaeoclimatology, Palaeoecology, 243(3-4): 348-372.
Analyzing the degree of organic matter transformation of rewetted European peatlands in the context of their greenhouse gas emission potential
Authors: Groß-Schmölders Miriam , Leifeld Jens
Published: February 2023

Peatlands are a vast and vulnerable carbon stock. Although they cover only 3% of the land area, globally the organic matter stored in peat accounts for 20% of soil carbon. In peat-rich countries, peat soils contribute much to the carbon dioxide (CO2) emissions from croplands and grasslands in the national greenhouse gas (GHG) budgets. This may seriously diminish any possible net carbon sink of the land use sector. Owing to their high emission reduction potential per area, cultivated peat soils are often considered as a very effective target for GHG mitigation measures in the agriculture and land use sector. This goal can be achieved by rewetting. Rewetting often comes with synergies such as water protection, as peat soils are also high sources of dissolved organic matter and nutrient efflux. In wet soil transformation is driven by anaerobic processes and the resulting methane emissions can be considered a tradeoff of CO2 savings by wet management. How groundwater table raise influences GHG emissions depends e.g. on peat properties, environmental conditions and site management. The goal of the EU project EJP Soil INSURE, to which our research project belongs, is to evaluate the significance of different factors regulating the GHG balance of wet cultivated peat soils at different European sites and to seek for indicators of successful GHG mitigation. We contribute to this goal by analyzing the organic matter of peat profiles. We study the molecular composition of the different peats using analytical pyrolysis GC-MS, in conjunction with organic matter stoichiometry. Our aim is to better understand the role of peat properties for the biogeochemical cycles in rewetted peatlands and their GHG balance. By using different classes of compounds, we were able to distinguish between transformed organic matter and peat that is relatively rich in undecomposed plant material. We identified marker compounds that were highly specific for fresh plants, transformed plant material or microbial abundance. For example, the abundance of undecomposed plants can be linked to levosugars, decomposed plant material is pictured by low weight polysaccharides such as 5-methyl-2-furalaldehyde and microbial matter is displayed by specific nitrogen compounds, as pyridines, pyrroles and indene’s, such as 1H-indene, 3-methyl. In addition, we studied the correlation between peat stoichiometry, compound abundance and the degree of transformation. We find that for example a high C/N ratio is negatively correlated with a high amount of low weight polysaccharides and compounds indicative for microbial abundance. We conclude that our method gives a detailed insight of peat composition. Further, it enhances our knowledge of peat quality and could therefore help to gain insights into the dependency of GHG emissions on peat quality.