bluuebunny/crossref_metadata_2025 huggingface dataset:
Event-based high-resolution water quality measurements in rural headwater catchments: DOC quality and DOC export
Authors: Ditzel Lukas , Spill Caroline , Gaßmann Matthias
Published: March 2024

In this study, the DOC concentration and DOC quality as well as the discharge of a small spring catchment area in the North Hessian low mountain range were investigated over a period of 1 ½ years. The Nesselbach near Kassel is a small siliceous low mountain stream with an average flow of around 8.5 l/s. The catchment area is primarily characterized by agriculture (75% area share) and is home to a small settlement and forest areas (15% area share). The DOC concentration and the quality indices SUVA254 and SL270 and SL290 were determined using a UV-Vis in-situ probe with a resolution of 5 minutes. These indices can be used to evaluate the strength of the aromatic compounds of the DOC molecules (SUVA254) or the molecular weight (SL275 and SL290). Good DOC quality is generally associated with strong aromatic bonds and a high molecular weight. Spearman correlations were calculated to investigate factors such as water temperature and event characteristics on DOC quality and DOC export. In addition, hysteresis analyses were carried out to interpret the discharge-DOC load relationship with a time lag. The results of the study show an unexpectedly low DOC export from the headwater catchment compared to the relevant literature, as well as a strong correlation between DOC export and DOC quality. The observed fluctuations in DOC quality are mainly determined by the season and the changing land use.
Estimating Hourly Nitrogen Oxide Emissions Across Asia Using Data from the GEMS Geostationary Satellite
Authors: Palmer Paul , Yao Fei , Henze Daven , Park Rokjin , Lee Gitaek
Published: March 2024

Conventional bottom-up emission inventories for atmospheric pollutants suffer from infrequent updates and substantial uncertainties. The Geostationary Environment Monitoring Spectrometer (GEMS) now provides columnar measurements for key atmospheric pollutants, including tropospheric O3, aerosols, and their precursors (NO2, SO2, HCHO, and glyoxal), on an hourly basis throughout the sunlit day, with a nominal spatial resolution of a few kilometres. These satellite data represent new constraints to determine top-down estimates of air pollutant emissions, providing complementary information to the bottom-up inventories. Collectively, bottom-up and top-down information provide better actionable information to develop more effective air pollution mitigation strategies. To demonstrate this, we infer emissions of nitrogen oxides (NOx=NO+NO2) across Asia from GEMS column observations of NO2 by using the adjoint of GEOS-Chem atmospheric chemical transport model. We explore diurnal variations in NOx emissions across diverse Asian cities, assessing their implications for emission policy formulation. Additionally, we conduct a critical evaluation of our top-down estimates of NOx emissions by comparing model simulations of NO2, driven by these estimates, with independent observations of NO2 throughout the region.
Sustainable water management in Southern Ecuador: water availability under climate change and adaptation strategies.
Authors: Ochoa-Sánchez Ana , Crespo Patricio , Willems Patrick , Célleri Rolando , Guzmán Pablo , Alvarado-Carrión María , Ochoa Johanna , García Jorge , Núñez Santiago , Rodas Verónica , Guerrero Rigoberto , Marín María Augusta , Sánchez Gabriela
Published: March 2024

Anthropogenic climate change together with non-climate drivers (e.g land use change) have affected natural and human systems in the Andean Mountain region. There is more evidence of changes in water systems, with decreasing water availability and increasing frequency and magnitude of extreme events (i.e. flooding and droughts). This region is especially vulnerable to climate change and faces challenges towards adaptation due to limited resources and policies. Therefore, we present an integrated water management (IWM) approach to secure water availability in a middle-size city in Southern Ecuador - Cuenca. The Andean city of Cuenca (~ 600 000 inhabitants, located at 2600 m a.s.l.) depends highly on precipitation and surface water from the highlands to ensure drinking water. Due to its complex orography, climate change projections are not yet available at an adequate resolution for local decision making and limited actions and plans towards adaptation are undertaken. Our IWM approach, then, involves two phases:(1) Quantifying water availability projections. Statistical and dynamical downscaling techniques are used to quantify climate change projections at 1 km resolution for the study area, together with indicators useful for decision-makers. Discharge projections are quantified by using conceptual and distributed hydrological models. In parallel, water consumption is monitored and projected. Finally, we find water availability projections towards 2100.(2) Constructing adaptation strategies. On the provision side, water management improvements are co-constructed with the local drinking water company (ETAPA EP), such as: evaluating old infrastructure (e.g. leaks control), proposing new green-blue and gray infrastructure. On the demand side, strategies to reduce water consumption are co-constructed and implemented within a pilot project that involves citizens from three neighbourhoods in Cuenca.Our study involves a variety of actors and sectors (i.e. Ecuadorian and Belgian Universities, decision- and policy makers and citizens), enhancing capacity building of local governments and transferring knowledge among Universities and institutions, to plan and implement adaptation strategies through bottom-up approaches. We expect that our approach can be used in other middle-size cities, with similar challenges or complex orography conditions.
Seagrasses' role as a reverse sedimentary phosphate pump
Authors: Soto Neta , Antler Gilad , Gross Avner
Published: March 2024

Seagrasses are marine-flowing plants that form an important coastal ecosystem. Although occupying less than 0.2% of the ocean’s surface, seagrasses store over 15% of the accumulated global carbon storage in the ocean’s sediments. Thus, Seagrass meadows play a pivotal role in mitigating climate change by carbon sequestration. Seagrasses are widely distributed in oligotrophic tropical waters despite the low nutrient levels in the water column due to their ability to absorb nutrients from the sediment porewater. Moreover, seagrasses can actively mobilize unavailable nutrients e.g., iron and phosphorus in the rhizosphere via multiple biogeochemical interactions. This provides them with an important advantage over pelagic photoautotrophs, which are limited by the availability of nutrients in the water column. Despite their ability to transport nutrients from sinks e.g., sediments to the water column where they can be recycled trough grazing or decomposition, the potential role of seagrass as a revers sedimentary phosphate pump remains unclear. The aim of this study is to examine the effect of seagrass disappearance on phosphate flux in marine coastal environments. In a series of incubation experiments, the change in the phosphate release was examined in different tissues of seagrass Halophila stipulacea. The results showed that the while the highest decomposition rate of the rhizomes was the fastest, the highest phosphate release rate was measured in the leaves, despite having similar phosphate content. Since the leaves mostly decompose in the water column, the released phosphate is made available to planktonic photoautotrophs and further enhances more carbon fixation. Overall, we suggest that in oligotrophic environments seagrasses act as a reverse phosphate pump by accessing phosphate in the sediment and later translocating it to the aboveground parts and releasing in the water column, thus fertilizing planktonic photoautotrophs and enhancing further carbon sequestration.
How Might the May 2015 Flood in the U.S. Southern Great Plains Induced by Clustered MCSs Unfold in the Future?
Authors: Feng Zhe , Chen Xiaodong , Leung Ruby
Published: March 2024

The historic 22-26 May 2015 flood event in Texas and Oklahoma was caused by anomalous clustered mesoscale convective systems (MCSs) that produced record-breaking rainfall and $3 billion of damage in the region. A month-long regional convection-permitting simulation is conducted to reconstruct multiple clustered MCSs that lead to this flood event. We further use the pseudo global warming approach to examine how a similar event may unfold in a warmer climate and the driving physical factors for the changes. Tracking of MCSs in observations and simulations shows that the historical simulation reproduces the salient characteristics of the observed MCSs. In a warmer climate under a high-emission (SSP5-8.5) scenario, the Southern Great Plains is projected to experience a near surface warming of 4-6 K, accompanied by enhanced moisture transport by the strengthened Great Plains low-level jet. A warmer and moister lower troposphere leads to 36-59% larger convective available potential energy, supporting wider and more intense convective updrafts and rainfall production. Consistently, MCSs have wider convective areas and stronger rainfall intensities, producing 50% larger rain volumes during the mature stage. Extreme (99.5%) MCS rainfall frequency and amount will increase by threefold (Fig. 1). However, MCS stratiform rain area decreases as a result of elevated stratiform cloud bases that lead to stronger sublimation and evaporation of precipitation in response to warming, resulting in reduced weak-to-moderate surface precipitation. Results suggest that global warming greatly increases precipitation intensity of clustered MCS events under strong synoptic influence, with much higher potential to produce serious floods without additional climate adaptation.Figure 1. (a) Frequency distribution of MCS grid-point hourly rain rates, and (b) normalized cumulative distribution of rainfall amount by hourly rain rates. The region of the data included is show in the inset.
Florida Current: four decades of steady state at 27°N
Authors: Volkov Denis , Smith Ryan , Garcia Rigoberto , Baringer Molly , Johns William , Moat Benjamin , Smeed David
Published: March 2024

The Florida Current (FC) provides the majority of the northward volume and heat transports for both the meridional overturning and the horizontal gyre circulations in the subtropical North Atlantic. A unique, sustained observing system in the Florida Straits at about 27°N, consisting of voltage measurements recorded from a submarine telecommunication cable installed between Florida and Grand Bahama Island, paired with regular calibration and validation cruises, was established in 1982. Since then, the recorded cable voltage time series has enabled over 40 years of quasi-continuous, daily estimates of the FC volume transport. The cable data constitutes the longest observational record of any boundary current and a key component of the Atlantic Meridional Overturning Circulation (AMOC) in existence. By this measure, it can be representative of the AMOC weakening, suggested by climate models and proxy-based reconstructions.Here, we reassess the record-long change in the FC strength by revising the processing of voltages measured on the submarine cable. With the increased length of the cable record, we show that it has become necessary to account for the secular change in the Earth’s geomagnetic field, especially when studying processes on decadal and longer time scales. We calculate the corrected estimates of the FC volume transport and show that (i) the FC strength has not declined as reported recently, but has remained remarkably stable since 1982, and (ii) with the corrected FC record, the AMOC at ~26.5°N exhibits a decadal-scale variability rather than a long-term decline.The results of this study indicate that, if climate models are correct that the AMOC is slowing or will soon slow down, this slowdown has not yet been reflected in the FC, or the observational record is still too short to detect it with confidence. The existing records are just starting to resolve decadal-scale signals relevant to climate variability. Continued observations are thus necessary for detection and mechanistic understanding of climate-related changes and for validating and improving ocean and climate models.
Teacher on board the deep sea vessel Pourquoi pas ?  for SUPER MOUV campaign off the coast of Ecuador 
Authors: Gendron Faustine
Published: March 2024

As a biology and geology teacher, I have followed virtually, with some of my students, the HIPER campaign off the coast of Ecuador in 2022-2023, and from the 28th of january 2024 to the 23rd of february 2024, I have the honnor to take part in the SUPER MOUV campaign on the french oceanographic ship Pourquoi pas ? in Ecuador.The scientists left me an additional place on one of the most innovative ship in the Ifremer fleet, in order to spread geology tools use on board in destination to teachers and their students in college and highschool, not only in France but also all over the world in the french schools abroad or the french classes abroad : http://edumed.unice.fr/data-center/oceano/supermouv.phpDuring this campaign, the aim is to prepare some challenges connected to SUPER MOUV activities for schools :- students can indeed discover geodynamic in Ecuador west coast which is located in the ring of fire, and shaken by several earthquakes due to the subduction of Nazca tectonic plate under south-america tectonic plate,- they can also discover how rocks or fluids are collected by Nautile submarine, how sediments are collected by coring, how highligths geo-mechanical properties of rocks or methods for fluids analysis,…- and furthermore, they can learn about life on board a deep sea vessel (way of life, different jobs,..) during videoconferencings between the ship and the pupils in their classrooms ! 
Full-Field Numerical Simulation of Halite Dynamic Recrystallization From Subgrain Rotation to Grain Boundary Migration
Authors: Hao Baoqin , Llorens Maria-Gema , Griera Albert , Bons Paul D. , Lebensohn Ricardo A. , Yu Yuanchao , Gomez-Rivas Enrique
Published: March 2024

Full-field numerical modelling is a useful method to gain understanding of rock salt deformation at multiple scales, but it is quite challenging due to the anisotropy and complex plastic behavior of halite and other evaporite minerals at the single crystal level, together with dynamic recrystallization processes. We overcome these challenges and present novel results of full-field numerical simulation of dynamic recrystallization of halite polycrystalline aggregates during simple shear deformation, including subgrain rotation and grain boundary migration recrystallization processes. The results illustrate that the approach successfully reproduces the evolution of pure halite microstructures from laboratory torsion deformation experiments at 100-300℃ up to shear strain of four. Temperature determines the competition between (i) grain size reduction controlled by dislocation glide and subgrain rotation recrystallization (at low temperature) and (ii) grain growth associated with grain boundary migration (at higher temperature), while the resulting crystallographic preferred orientations are similar for all cases. The analysis of the misorientation reveals that the relationship between subgrain misorientation and strain follows a power law relationship with a general exponent of 2/3. However, with progressive deformation, dynamic recrystallization leads to a gradual deviation from this relationship. Therefore, predicting strain or temperature from microstructures necessitates careful calibration.
Estimating the risk of crop yield loss due to changing regional air temperatures
Authors: Unnikrishnan Poornima , Ponnambalam Kumaraswamy , Hipel Keith
Published: March 2024

Agricultural produce’s yield can be heavily impacted by changes in the weather patterns. With the current global warming scenario, the extremes temperature anomalies are expected to occur more frequently, posing a significant threat to the crop yields. To better plan the agricultural practices and crop rotation, it would be highly beneficial to understand the impact of temperature anomalies on crop yields. Here in this study, we investigated the impact of changing air temperature extremes on the yields of strawberries in farms in California's Central Valley. By using a copula modeling framework, the study has identified the risks of crop yield loss associated with temperature extremes. Based on this analysis, various scenarios of crop yield loss have been identified, and the likelihood of encountering those scenarios based on changes in temperature extremes has been estimated. The results of this study can be immensely helpful in planning agricultural practices and implementing appropriate measures to mitigate the risks. With air temperature forecasts readily available from various sources, nature-based solutions can be effectively implemented to combat the negative effects of temperature extremes on crop yields.
Response of carbon, water and energy fluxes to drought and flood at a forest ICOS station in Norway
Authors: Lange Holger , Zhao Junbin , Meissner Helge
Published: March 2024

Hurdal (NO-Hur) is a recently labelled ICOS class 2 station in Southeast Norway. It represents a typical southern boreal forest of medium productivity, dominated by old Norway spruce (average tree height: 25 m, ages: up to 100 years) with some pine and broadleaved trees. The eddy covariance technique is used to measure CO2 fluxes on a 42 m tower since 2021 . The measurements have an average footprint area of approximately 63 ha.In 2023, the region experienced an unusual dry spring and then an extraordinary flood in August. Both events showed significant impact on the Net Ecosystem Exchange (NEE) and heat fluxes. The station is also equipped with automatic dendrometers and sap flow devices on the dominant spruce trees, allowing us to investigate the impact of these events at the individual tree scale. We will present tree growth and transpiration flux at different temporal scales (from sub-daily to seasonal), and relate these single tree observations with environmental variables, ecosystem-level NEE and evapotranspiration using phase synchronization analysis. These observational data will yield insights into carbon and water processes of a boreal forest at different scales in response to multiple disturbances.
A constrained spectral approximation of subgrid-scale orography on unstructured grids
Authors: Chew Ray , Dolaptchiev Stamen , Wedel Maja-Sophie , Achatz Ulrich
Published: March 2024

The representation of subgrid-scale orography is a challenge in the physical parameterisation of orographic gravity-wave sources in weather forecasting. A significant hurdle is encoding as much physical information with as simple a spectral representation as possible on unstructured geodesic grids with non-quadrilateral grid cells, such as the one used in the German Weather Service's Icosahedral Nonhydrostatic Model. Other issues include scale awareness, i.e., the orographic representation has to change according to the grid cell size. This work introduces a novel spectral analysis method approximating a scale-aware spectrum of subgrid-scale orography on unstructured geodesic grids. The dimension of the physical orographic data is reduced by more than two orders of magnitude in its spectral representation. Simultaneously, the power of the approximated spectrum is close to the physical value. The method is based on well-known least-squares spectral analyses. However, it is robust to the choice of the free parameters, and tuning the algorithm is generally unnecessary. Numerical experiments involving an idealised setup show that this novel spectral analysis performs significantly better than a straightforward least-squares spectral analysis in representing the physical energy of a spectrum. Studies involving real-world topographic data are conducted, and competitive error scores within 10% error relative to the maximum physical quantity of interest were achieved across different grid sizes and background wind speeds. The deterministic behaviour of the method is investigated along with its principal capabilities and potential biases, and it is shown that the error scores can be iteratively improved if an optimisation target is known.
Hillslope and river runoff generation in permafrost areas: a case study in the Qilian Mountains
Authors: Zhang Fan , Zeng Chen , Xie Shenqi
Published: March 2024

Permafrost is widely distributed across the Tibetan Plateau and plays a significant role in regional hydrological processes. This study focuses on a permafrost catchment located at Dadongshushan Yakou, Qilian County, Qinghai Province, China. Water samples, including rainfall, soil water (encompassing mobile soil water, bulk soil water, and supra-permafrost groundwater), ground ice, and runoff from hillslope plot, were collected during various thawing stages from May to September in 2021 and 2022. Stable isotope and hydrochemical analyses were utilized to trace the sources of hillslope runoff. Additionally, a standard runoff plot on a typical hillslope and a gauging weir at the catchment outlet were established to monitor hillslope and river runoff from July to August in both 2021 and 2022. Analysis of the data yielded several key findings: (1) Ground ice meltwater and rainfall were identified as the primary sources of hillslope runoff in spring (approximately 70%) and summer (60-80%), respectively. (2) The thickness of the saturated layer emerged as the pivotal factor influencing lateral subsurface flow on permafrost hillslopes during the summer months. (3) Slow runoff in forms of subsurface flow and quick runoff originating from river channel rainfall accounted for more than 90% and less than 10% of the total river runoff during the summer period, respectively. These results indicate that the combined effects of rainfall and groundwater thawing contributed to the formation of a super-permafrost saturated soil layer, which subsequently initiates a chain process where the saturated soil layer interacts with rainfall to supply streamflow in the river channel. This study enhances our understanding of the hydrological significance of the active layer thawing process and supra-permafrost groundwater, providing a theoretical foundation for the future development of hydrological models in permafrost regions.
Geodynamic and kinematic model of the South China Sea and regional plates since the end of seafloor spreading
Authors: Zhao Minghui , Sibuet Jean-Claude , Wu Jonny , Liu Siqing , Cheng Jinhui
Published: March 2024

The geodynamics and plate tectonics of the South China Sea (SCS)-Taiwan region since Miocene times are uncertain because the former extent and tectonic configuration of the subducted easternmost SCS along the Manila trench is uncertain. Here we unravel the regional kinematic context from main offshore constraints including published unfolding of the Manila slab from seismic tomography, which provides insight on restoring the subducted part of the SCS. We reconstruct a whole northern SCS continent-ocean boundary (COB) that consists of a northeastern SCS COB segment (called ‘S3’), trending N070° that roughly parallels the present SCS shelf; a 350-km long ~N-S trending segment S2 that steps north to Hualien; and, a third segment S1 that extends from east of Hualien beneath the Ryukyu subduction zone trending N085° that ends near Miyako Island in the Ryukyus.We demonstrated that the two-plate kinematic model is the best framework to explain the existing data. The boundary between Eurasia and Philippine Sea plate is a ~NS oriented left-lateral lithospheric shear fault called the Manila transcurrent fault (MTF). The MTF initiated ~18 Ma at the onset of the tear and progressively moved eastward, creating the intra-oceanic Luzon arc. The MTF ancestor was a N337° oriented left-lateral shear fault, while the HB-PSP/EU motion was changing to N307°, allowing the HB-PSP plate to subduct between the two lips of a westward propagating tear fault until ~7 Ma. Since ~7 Ma, the MTF-PFZ constantly moved westward and 23° clockwise rotated from N337° to ~NS, which began collision ~7 Ma ago along the EU margin. Plate kinematic reconstructions from ~18 Ma to Present are synthesized in terms of continental or oceanic nature of the main PSP-HB and EU entities before their subduction that provide new understanding on Taiwan, PSP-SCS kinematics, and regional histories. This work is supported by Key projects of the Chinese National Natural Science Foundation (contracts 91958212, 42106078).
Primary Origin of Lunar Surface Water: Constraints from Observations of Chang'e-5
Authors: Lin Honglei
Published: March 2024

Water plays a crucial role in the Moon's evolution and holds significant implications for potential human activities on its surface. Previous studies, based on measurements of a limited number of lunar soil particles, have revealed evidence supporting various sources of lunar water, including its origin from the lunar interior, solar wind implantation, and impacts from comets or asteroids. Nevertheless, the limitation of these studies stems from the restricted number of particle samples, hindering the achievement of adequate statistical significance. As a result, the primary source of water on the Moon remains enigmatic. To address this critical question and advance our understanding of lunar water sources, we initiated new spectral measurements using lunar bulk soil collected by Chang'e-5 under controlled conditions. We observed variations in water content across different particle sizes. Our findings suggest that solar/ Earth wind implantation is likely the primary source of lunar surface water. The controlled experiments conducted on the lunar bulk soil samples provide valuable insights, offering statistical evidence for the origin of water in lunar soil. We also bridged the laboratory, in-situ, and orbital results, offering a cohesive understanding of lunar surface water characteristics as represented by Chang'e-5.
Sub-Arc Mantle Redox Evolution since the Archean
Authors: Liu Chun-Tao , Ye Chen-Yang , Zhang Zhou
Published: March 2024

The redox state of the sub-arc mantle is critical in contraining the behavior of redox-sensitive elements, particularly volatile species, within the magmatic system. However, the long-term evolution of redox conditions in the sub-arc mantle and its impact on atmospheric oxygen levels remain unclear. In this study, we address two key challenges in understanding the sub-arc mantle redox throughout geological history: 1) the need for more effective methods to identify arc samples in different tectonic settings, and 2) the lack of constraints on the evolution of redox-sensitive trace elements from the mantle source. To overcome these challenges, we used an XGBoost machine learning model trained on multiple elements and elemental ratios (e.g., Nb, Ta, Ti, Pb, Th/Nb, Nb/La, and U/Nb) to accurately classify arc basalts and basalts (N ≈ 14,000) derived from other tectonic settings. Subsequently, we modeled the evolution of trace elements (V, Ti, and Sc) partitioning in the hydrous and dry depleted mantle beneath the arc using non-modal near-fractional melting. Finally, we applied the trained machine learning model and redox-sensitive elemental ratios to a refined global dataset of basalts (N ≈ 19,000) to calculate the redox evolution since 3.4 Ga. Our findings reveal that there have been minimal fluctuations in the melting T-P conditions since 3.4 Ga, indicating a consistent oxidized state in the sub-arc mantle. The average ΔFMQ of 0.96 ± 0.52 (1 SD) observed in our study is similar to that of the modern arc mantle since the early Archean. Interestingly, it is unlikely that the long-term oxidation of the sub-arc mantle has significantly impacted the progressive increase in atmospheric oxygen levels over time.
Redox state of Archean surface environments: Insights from the Banded Iron Formations (BIFs) of the Western Dharwar Craton, Southern India 
Authors: Mukherjee Aindrila , Mudlappa Jayananda , Nasipuri Pritam , Krishnasamy Raveendran Aadhiseshan
Published: March 2024

The interplay of geological, chemical and biological processes that drive the oxygenation of the oceans-atmosphere of the early earth are spatially linked to the emergence of biosphere. Banded Iron Formations (BIFs) from the Archean greenstone belts form important archives for understanding the redox conditions of Archean surface environments. The Archean Dharwar craton preserves BIFs in the volcano-sedimentary greenstone belts of two distinct stratigraphic units (older Sargur Group and younger Dharwar Supergroup) corresponding to a time span of 3300-2600 Ma.  These BIFs are confined to the highest stratigraphic levels forming summits of greenstone belts.  They show alternate layers of chert and iron oxides, and petrographic data reveal diverse mineralogy including oxides, carbonate, sulphide and silicate facies. The occurrence of riebeckite and stilpnomelane in BIFs of younger Dharwar Supergroup indicates recrystallization under low-grade metamorphism. Slightly higher abundances of CaO and Al2O3 reveal significant influence of crustal source and precipitation of CaCO3 during BIFs formation. Mesoscopic layers of chert and iron oxide with variable thickness suggest fluctuating redox state of surface environments. The higher enrichment of Ni (6-26 ppm) than the Cr content (3-19 ppm) with variable Sr concentrations may be attributed to feldspar breakdown during hydrothermal fluid acceleration. Trace element ratios (Y/Ho, Sm/Yb, Eu/Sm) coupled with positive Eu anomalies of the BIFs from both older Sargur Group and younger Dharwar Supergroup BIFs reveal dominant hydrothermal input in BIFs origin. The PAAS normalized REE data preclude major continental input in the origin of BIFs. The variable negative Ce anomalies imply periodic fluctuating surface environments (oxic to anoxic) at the dawn of the Great Oxidation Event close to 2340 Ma. This is consistent with the published Fe, N, and S isotope data on the BIFs of the Western Dharwar craton. 
Understanding the 2022 heat wave mechanism in the Iberian Peninsula
Authors: Nam So-Hyun , Kim Jeong-Hun , Kim Maeng-Ki
Published: March 2024

Recently, the intensity and frequency of heat waves have been increasing worldwide. Especially in 2022, Europe was severely affected by unprecedented heat waves, resulting in about 3,000 deaths in Spain. In this study, we investigate the mechanisms of extreme heat waves in the Iberian Peninsula and examine the differences between the typical heat wave cases and heat waves in 2022. Results show that the Iberian heat waves of 2022 strongly developed during two periods (9−18 June and 8−18 July; P1 and P2, respectively). The typical heat wave cases exhibit wave patterns, but in 2022, a high-pressure anomaly developed over the North Atlantic, blocking the atmosphere and enhancing the heatwave in the Iberian Peninsula. In the P1 period, the lower troposphere in the Iberian Peninsula was moistened, resulting in a water vapor-driven heat dome. In contrast, during the P2 period, the dry atmosphere was heated, causing high temperatures. As a result, the longer-than-normal blocking events over the Iberian Peninsula led to a prolonged heat dome, causing the unprecedented Iberian heat wave. Keywords: Heat waves, Europe, Iberian Peninsula, blocking, extreme events AcknowledgmentThis research was supported by the Specialized university program for confluence analysis of Weather and Climate Data of the Korea Meteorological Institut (KMI) funded by the Korean government (KMA) and the Korea Meteorological Administration Research and Development Program under Grant KMI (KMI2022-01311).
Increasing gross primary productivity under soil warming and wettingon the Tibetan Plateau
Authors: Jia Binghao , Peng Qing
Published: March 2024

The soil freeze-thaw process has undergone significant changes on the Tibetan Plateau (TP) in the context of global change, resulting in the changes of soil physical and chemical properties, thereby affecting the vegetation phenology and photosynthesis through affecting the utilization capacity of CO2 and light by vegetation. However, little is known about how soil temperature (ST) and soil moisture (SM) affect the gross primary productivity (GPP) on the TP at different seasons and elevations. In this study, the spatiotemporal variation patterns of GPP, ST, and SM were analyzed based on the Community Land Model version 5.0 (CLM5.0) simulations in order to illustrate the impacts of ST and SM in surface (0–10 cm) and root zone soil (0–100 cm) on GPP between 1979 and 2020. The results showed that the CLM5.0-based GPP and ST were in good agreement with in situ observations. ST, SM and GPP increased at the rates of 0.04 ℃ a−1, 2.4 × 10−4 mm3 mm−3 a−1, and 5.36 g C m−2 a−2, respectively. SM dominated the variations of GPP in winter (64.3%), while ST almost was the dominant factor in other periods, especially spring (99.9%) and autumn (94.7%). The explanatory power of ST and SM for GPP increased with elevation, especially for ST. The relative contributions of ST and SM to GPP at different time scales in root zone soil were similar to those in surface soil. This study provided a new understanding of how soil freeze-thaw affected GPP changes on the TP in the context of the intensification of warming and humidification.
Subseasonal Variability of Sea Level Pressure and Its Influence on Snowpack over Mid-High-Latitude Eurasia during Boreal Winter
Authors: Yalu Ru , Xuejuan Ren
Published: March 2024

The atmospheric circulation significantly influences the snowpack over mid-high-latitude Eurasia. This study examines the characteristics of the leading subseasonal variability mode of boreal winter sea level pressure (SLP) and its influence on snowpack over mid-high-latitude Eurasia, using the fifth generation of European Center for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA5) data and different snowpack datasets. The leading mode, characterized by a monopole pattern with a strong surface anomalous high centered near the Ural Mountains, exhibits a barotropic structure and extends from the surface to the tropopause. Above SLP and geopotential height anomalies propagate southeastward from the Barents-Kara Sea to East Asia. This leading SLP mode contributes to surface air temperature (SAT) and snowfall circulation anomalies over mid-high-latitude Eurasia. The latter two both directly influence on snowpack anomalies in situ. Over high latitude region, snowfall circulation anomaly is the dominant factor to control the snow depth anomaly. Over middle latitude region, both SAT and snowfall circulation anomalies lead to the snowpack anomaly. Furthermore, the response of snow depth to the leading subseaonal SLP mode occurs 2-5 days earlier than the response of snow cover to the same mode. In addition, it is suggested that the Arctic Oscillation (AO), East Atlantic/West Russia (EAWR) and Polar/Eurasia (PEU) pattern may contribute to the development of the leading SLP mode and subsequently influence snowpack anomalies.
A Clue to the Filamentary Nature of Solar Filaments
Authors: Choe Gwangson , Lee Minseon , Yi Sibaek
Published: March 2024

It is generally accepted that solar prominences, also known as filaments, are formed through thermal condensation instability from hot coronal plasmas. Within solar prominences (filaments), counter-streaming subscale flows are frequently observed. It is quite surprising that thermal instability in magnetized plasmas with such shear flows has never been earnestly studied despite extensive research on thermal instability in various astrophysical contexts. In this paper, we have investigated this unexplored territory of thermal instability and have unexpectedly gained hints on why solar filaments are filamentary.We have performed linear stability analysis of magnetized plasmas with shear flows within the framework of magnetohydrodynamics (MHD), incorporating radiative cooling, phenomenological plasma heating, and anisotropic thermal conduction. Our approach formulates an eigenvalue problem, which we solve numerically to derive eigenfrequencies and eigenfunctions.Our findings reveal that, for shear speeds less than the Alfven speed of the background plasma, the dominant mode corresponds to an isobaric thermal condensation mode. Most remarkably, the eigenfunctions associated with this mode display a distinctive, discrete structure resembling delta functions, especially when the shear velocity in the k-direction exceeds 10−5 of the Alfven speed. We identify that these delta function-like spikes coincide with the zeroes of the coefficients of the second-order derivative terms in the differential equation of the eigenvalue problem.In contrast, for shear speeds exceeding the Alfven speed (a rare occurrence in reality), we observe an isentropic Kelvin-Helmholtz instability, incompatible with thermal condensation.Our investigation underscores that any non-uniform velocity field with a magnitude surpassing 10−5 of the Alfven speed triggers the discrete eigenfunction characteristic of the condensation mode. Consequently, filamentary condensation at discrete layers or threads, emerges as a natural and universal process whenever thermal condensation instability arises in magnetized plasmas with shear flows.
Characteristics of geochemistry and benthic communities in microbial mat-covered sediments related to methane seepage, northeastern Japan Sea
Authors: Ota Yuki , Suzumura Masahiro , Tsukasaki Ayumi , Suzuki Atsushi , Iguchi Akira , Nishijima Miyuki , Yoshioka Hideyoshi , Aoyagi Tomo , Hori Tomoyuki
Published: March 2024

We investigated characteristics of benthic macrofaunal communities and geochemical parameters in and around microbial mat-covered sediments associated with a methane seepage on Sakata Knoll in the northeastern Japan Sea. A depression on top of the knoll corresponds to a gas-hydrate-bearing area with seepage of methane-rich fluid, and microbial mats patchily cover the seafloor sediments. Sediment cores were collected at three sites for this study: one within a microbial mat, a second a few meters outside of the microbial mat, and a third from a reference site outside the gas-hydrate-bearing areas.The profile of porewater sulfate ion concentrations below the microbial mat showed linear decreases from near seawater values close to the sediment-water interface to zero concentration at approximately 7 cmbsf. Compared to the reference site, total sulfur (TS) contents were significantly higher and δ13C of total inorganic carbon were strongly negative values in the entire core below the microbial mats and in sediments below 10 cm depth outside mat, respectively. These results indicate the presence of the authigenic carbonates and sulfide minerals produced by the anaerobic oxidation of methane (AOM) in these sediments. There is no fall in sulfate concentration in the whole core collected outside microbial mat, which may be explained by the higher upward flow of methane gas inside than outside the mat. Both the 18S rRNA genes and morphological analyses showed that the surface sediment inside the microbial mat noticeably favored annelids, with dorvilleid Ophryotrocha sp. and ampharetid Neosabellides sp. identified as major constituents. The sulfidic sediment conditions with concentrations of H2S up to 121 µM resulting from AOM likely resulted in the predominance of annelids with tolerance to sulfide. In addition, the higher contents of Mo in whole cores collected inside the microbial mat than that at the reference site indicate strong enrichments of molybdenum in the sediment inside the mat. The positive correlation of Mo with TS contents suggests that the AOM-derived H2S favored the capture of Mo on sulfide minerals such as pyrite. Because of the absence of enrichments of redox-sensitive trace elements other than Mo in the Sakata Knoll sediments, molybdenum may be efficiently transported into the AOM-induced sulfidic seafloor by absorption on the particulate Fe-Mn hydroxides that are well preserved in oxic water column of the Japan Sea Proper Water.This study was conducted as a part of the methane hydrate research project funded by METI (the Ministry of Economy, Trade and Industry, Japan).
Energization of Cold Ions in Asymmetric Reconnection: Particle-in-Cell Simulation
Authors: Song Liangjin , Zhou Meng , Yi Yongyuan , Deng Xiaohua
Published: March 2024

Cold ions from Earth's ionosphere and plasmasphere are frequently observed at the Earth's magnetopause, impacting reconnection in ways such as altering the reconnection rate and energy budget. Despite extensive research on reconnection, the fluid properties and kinetics of cold ions in magnetopause reconnection remain unclear. Our recent 2-D particle-in-cell simulation provides new insight into cold ion dynamics in asymmetric reconnection. Our simulation shows that cold ions, initially located only in the magnetosphere, absorb 10% to 25% of the total released magnetic energy, primarily converting it into thermal energy through stochastic heating, that is, the viscous heating associated with the non-gyrotropic pressure tensor. Cold ions are step-by-step accelerated by the Hall electric field during meandering motion across the magnetopause current sheet. The velocity distribution functions of cold ions in different regions are made up of two types of particles, differentiated by their ability to penetrate into the magnetosheath. The reconnection electric field has different effects on these two types of cold ions. As reconnection continues, the velocity distribution functions of the cold ions diffuse, leading to bulking heating. These findings significantly enhance our understanding of cold ion dynamics at the Earth's magnetopause.
Isotope Hydrology progress in sub-Saharan Africa. What information for water management? 
Authors: Nlend Bertil , Huneau Fréderic , Ngo Boum-Nkot Suzanne
Published: March 2024

The utility of isotope techniques in hydrological investigations stems from their ability to label water sources and cycling processes including surface/groundwater interaction, water residence times, flow pathways, evaporation fluxes, and solute processes, to name a few. In Africa, they have been applied since four decades following the severe drought of the 1970s, and can now be summarized in important case studies. This review focusing on Cameroon (often called the little Africa) aims to put together all the stable and radioactive isotopic data (>500 samples from rainfall, surface and groundwater) published in the country to: (i) identify the drivers responsible for precipitation isotopes spatial variation and climatological implications, (ii) elucidate the groundwater recharge mechanisms over the countries and relationships with rivers, and (iii) highlight the existence of paleo-groundwater in the country. It is found that rainfall stable isotopes variation is linked to the migration of the Intertropical Convergence Zone (ITCZ). The groundwater recharge can be diffuse and focused. This latter mechanism is mainly observed in the semi-arid region. It is in this relatively dry region that most of the paleo-groundwater resources are identified thanks to 14C dating. This information will be useful to develop water management strategies regarding all the challenges (e.g., climatic and demographic) faced by the country. Finally, this paper discusses the gaps groundwater isotope hydrology can still fill for contributing to a sustainable development of the country. Reflections provided here can be extend in each country of the sub-Saharan Africa region.
Hot spot in the schoolyard
Authors: Veltz Isabelle , Bour Virginie
Published: March 2024

Defined by Howard in 1818, an “Urban Heat Island” corresponds to an urbanized area where the temperature is higher than in natural or surrounding environments. With climate change, this phenomenon affects more than 80% of urban populations and is linked to the storage of heat in the asphalt during the day and the stagnation of air between homes. Water runs off the surface of the waterproofed soil and the vegetation must be watered constantly.With the regular increase in temperatures, the Roosevelt high school in the city center of Reims (Champagne, France) becomes a furnace from spring to autumn. In fact, with its tarmac square schoolyard surrounded by high dark red brick buildings, we measure recurring morning temperatures above 30°C and afternoon peaks above 40°C in classrooms.This work, carried out by students, aims to define adaptation strategies and propose feasible modifications in this enclosure, which is classified as a “historic monument” and which must therefore maintain its total integrity. Roosevelt high school contains the “War Room” which is the surrender room where the end of the Second World War was signed on May 7, 1945 and it’s impossible to change its appearance.After identifying the causes favouring the “Heat Island” effect in their highschool, the student carried out measurements of albedo, runoff and impact of the scare vegetated areas were carried out. Analog and computer-assisted experiments have been developed to propose solutions to limit heat accumulation and soil drying and promotes humidification and CO2 trapping in the ground.This work conducted by the students allowed them to propose non-invasive solutions improving the quality of life in their work environment.Through its local and experimental approach, this work has made concrete highly mediatized notions whose causes and consequences are not always well associated. Moreover, the major role of soil and soil preservation, in modulating climate change, has been clearly highlighted.
Preliminary Results of P-wave tomographic imaging beneath Sulawesi, Indonesia
Authors: Supendi Pepen , Rawlinson Nicholas , Han Jifei , Widiyantoro Sri , Karnawati Dwikorita
Published: March 2024

The island of Sulawesi is located within a complex tectonic region at the confluence of the Eurasian, Indo-Australian and Philippine plates. The recent geological history in the area reflects the ongoing subduction, extension, obduction, and collision of continental fragments. The island consists of four elongated arms (the north, east, southeast, and southern arms) that are composed of distinct lithological assemblages. Based on local and regional earthquake travel-time tomography, we present a new 3-D P-wave velocity model of the crust and upper mantle beneath Sulawesi. We used the Fast Marching Tomography (FMTOMO) package to retrieve 3-D P-wave velocity variations relative to a 1-D starting velocity model based on ak135. The catalogue and phase data were taken from the Agency for Meteorology, Climatology, and Geophysics (BMKG) of Indonesia for the period 2018 through to 2023, recorded by 126 seismic stations in Sulawesi and its neighbourhood. Our preliminary results reveal clear evidence of subducted slabs as indicated by high-velocity anomalies penetrating into the mantle along the Molucca Sea Collision Zone and to the north of Sulawesi; we also see a low-velocity anomaly beneath volcanoes located at the eastern end of the North Arm of Sulawesi.