bluuebunny/crossref_metadata_2025 huggingface dataset:
Seasonal Salinification of the US Northeast Continental Shelf Driven by an Imbalance Between Along-Shelf Advection and Cross-Shelf Eddy-Covariance Fluxes
Authors: Taenzer Lukas , Chen Ke , Plueddemann Albert , Gawarkiewicz Glen
Published: March 2024

The US Northeast continental shelf “cold pool” defines the body of winter-cooled Shelf Water that decouples from the surface layer during the stratified season. The cold pool canonically preserves fresh Shelf Water properties throughout the summer, which fulfills vital needs for the regional benthic ecosystem in the economically most productive fisheries region across the United States. However, recent warming trends significantly above the global average have put the ecosystem under environmental stress. While the cold pool’s heat content has been studied in detail, data limitations and large interannual variability in salinity have hampered an assessment of the cold pool’s salt budget. Here, we provide first evidence that the cold pool’s salt content increases significantly during the stratified season and investigate dynamical drivers of this trend, using a combination of multi-year mooring and glider observations and high-resolution regional model output. Cold pool salinification rates of 6 mPSU/day remain steady throughout the stratified season, leading to salinity differences of 1 PSU between April and October. The annual cold pool salinification is caused by an imbalance between eddy-covariance salt fluxes across the US Northeast shelfbreak front and advection of freshwater from upstream. While eddy-fluxes deposit salt onto the continental shelf at all times of year, the US Northeast shelfbreak jet is weakest during the summer, which reduces along-shelf advection. A seasonal reduction in the along-shelf salinity gradient is likely caused by processes in the Gulf of Maine/on Georges Bank. The observed interannual variability of the salinification signal is shaped by the intermittency of strong cross-shelfbreak eddy-covariance fluxes that are concentrated within 3-4 episodic events per year. Capturing the hydrographic trends in coastal water mass budgets and identifying their underlying dynamical mechanisms will lead to a better understanding of ecosystem responses and support sustainable fisheries management in a rapidly changing coastal ocean region. 
Soil organic matter turnover: global implications from δ13C and δ15N signatures
Authors: Kuzyakov Yakov , Soldatova Evgeniya
Published: March 2024

The residence time of carbon (C) and nitrogen (N) in soil is a fundamental parameter reflecting the rates of soil organic matter (SOM) transformation and the contribution of soils to greenhouse gases fluxes. Based on the global database of the stable isotope composition of C (δ13C) and N (δ15N) depending on soil depth (171 profiles), we assessed С and N turnover and related them to climate, biome types and soil properties. The 13C and 15N discrimination between the litter horizon and mineral soil was evaluated to explain the key litter transformation processes. The 13C and 15N discrimination by microbial utilization of litter and SOM, as well as the continuous increase of δ13C and δ15N with depth, enabled to assess C and N turnover within SOM. N turnover was two times faster than that of C, which reflects i) repeated N recycling by microorganisms accelerating the N turnover, ii) C loss as CO2 and input of new C atoms to cycling, which reduces the C turnover, and iii) generally slower turnover of N free persistent organic compounds (e.g. lignin, suberin, cellulose) compared to the N containing compounds (e.g. amino acids, ribonucleic acids). An increase in temperature and precipitation accelerated C and N turnover because: i) higher microbial activity and SOM decomposition rate, ii) larger soil moisture and fast diffusion of dissolved organics towards exoenzymes, iii) downward transport of 13C-enriched organic matter (e.g. sugars, amino acids), and iii) leaching of 15N-depleted nitrates from the topsoil and losses from the whole soil profile. Temperature accelerates SOM turnover stronger than precipitation. The temperature increase by 10 °C accelerates the C and N turnover for 40%. SOM turnover is boosted by decreasing C/N ratio because: i) SOM with a high C/N ratio originated from litter is converted to microbially-derived SOM in mineral soil characterized by a low C/N ratio; ii) litter with a low C/N ratio is decomposed faster than litter with a high C/N; iii) microbial carbon-use efficiency increases with N availability. The biome type affects SOM decomposition by i) climate: slower turnover under wetter and colder conditions, and ii) by litter quality: faster utilization of leaves than needles. Thus, the fastest C turnover is common under evergreen forests and the lowest under mixed and coniferous ones, whereas temperature and C/N ratio are the main factors controlling SOM turnover. Concluding, the assessment of SOM turnover by δ13C and δ15N approach showed two times faster N turnover compared to C, and specifics of SOM turnover depending on the biomes as well as climate conditions.Soldatova E, Krasilnikov S, Kuzyakov Y 2024. Soil organic matter turnover: global implications from δ13C and δ15N signatures. Science of the Total Environment 912, 169423. https://doi.org/10.1016/j.scitotenv.2023.169423
Geomorphological Analysis of Cirques in the Western Islands of Greenland
Authors: Oien Rachel , Kurjanski Bartosz
Published: March 2024

This study employs Arctic DEM data and GIS tools, ACME 2.0 (Li et al., 2024), and GlaRe (Pellietero et al., 2016), to systematically investigate cirques in the western islands off central Greenland. The primary objective is to reconstruct past Equilibrium Line Altitude (ELA) variations at the end of the Younger Dryas period and derive insights into palaeoclimate conditions in this region.By leveraging high-resolution Arctic DEM datasets and advanced GIS methodologies, we analyse cirque morphologies and elevations to reconstruct ELAs, a key indicator of glacial development and climate conditions. The Younger Dryas, a well-documented, abrupt and relatively short climatic event, represents a critical period for understanding past climate dynamics and their impact on glacial landscapes on a timescale relevant to the contemporary human population.Our approach combines the semi-automated extraction of cirque parameters from the Arctic DEM with GIS-based modelling to reconstruct palaeo-ELA variations. Through spatial and temporal analysis, we aim to discern patterns of glacial response to climatic shifts between 13-9.5ka (Leger et al., 2024), shedding light on the sensitivity of Arctic cirques to rapid environmental changes.Preliminary results indicate distinct patterns in cirque morphology and ELAs consistent with variations in the ELA during the Younger Dryas. These findings contribute to a more comprehensive understanding of the regional impact of past climatic events on the Greenlandic glacial landscape. This research enhances our knowledge of the Younger Dryas climate dynamics in the western islands off Greenland, providing valuable insights into the region's palaeoclimate history and contributing to broader discussions on Arctic environmental change.
Workflow composition for compound flooding events and adaptation measures
Authors: Tromp Willem , Winsemius Hessel , Eilander Dirk , Weerts Albrecht , Backeberg Björn
Published: March 2024

Modelling of compound flood events, the assessment of their impact, and assessing mitigation and adaptation measures is in increasing demand for local authorities and stakeholders to support their decision making. Additionally, the severity of extreme events driving compound flooding, including storms and heavy rainfall, is projected to increase under climate change. To support local communities in flood risk management, complex modelling systems involving multiple cross-disciplinary models need to be orchestrated in order to effectively and efficiently run a wide range of what-if scenarios or historical events to understand the drivers and impacts of compound floods. The large volume and variety of data needed to configure the necessary models and simulate events strain the reproducibility of modelling frameworks, while the number of events and scenarios demand increasingly powerful computing resources. Here we present a solution to these challenges using automated workflows, leveraging the Common Workflow Language standard. The presented workflows update a base model configuration for a user-specified event or scenario, and automatically reruns multiple defined scenarios. The models are executed in containers and dispatched using the StreamFlow workflow manager designed for hybrid computing infrastructures. This solution offers a single, uniform interface for configuring all models involved in the model train, while also offering a single interface for running the model chain locally or on high performance computing infrastructures. The allows researchers to leverage data and computing resources more efficiently and provide them with a larger and more accurate range of compound flood events to support local authorities and stakeholders in their decision making.
A modelling investigation of foliage pH and its impact on the dry deposition flux of SO2 and NO2
Authors: Miller Stefan , Makar Paul , Hayden Katherine , Fathi Sepehr
Published: March 2024

The dry deposition of atmospheric pollutants (i.e., particulate matter, gases) has profound impacts on human and ecosystem health.  In regions of vegetation, a large fraction of particulate matter is deposited onto plant foliage, where it may undergo deliquescence to form a thin water layer on the leaf surface, altering the leaf surface pH.  Presently, gas-phase deposition algorithms used in air-quality models tend to ignore variations in the foliage pH and assume a constant neutral leaf of pH 6.68.  This constant pH is then used to determine the effective Henry’s law constants, which in turn influences the deposition velocity of atmospheric gases such as SO2 and NO2.  We use the GEM-MACH air-quality model to investigate and contrast the use of a neutral foliage pH versus a ‘dynamic’ foliage pH on the dry deposition of SO2 and NO2 in the Athabasca Oil Sands region.  In this work, the surface foliage pH in GEM-MACH is dynamically determined using HETP (Miller et al., 2023) by considering the accumulated deposition of anion and cation species to leaf surfaces (i.e., deposited precursor species such as sulfate, nitrate, ammonium, sodium, chloride, potassium, calcium and magnesium).  Processes such as precipitation, nutrient leeching, and epicuticular wax encapsulation are also considered in these simulations since these processes may impact the leaf surface chemistry after dry deposition has occurred. The results show that near the Athabasca Oil Sands sources, the large amount of base cation deposition has a profound impact on the predicted foliage surface pH where it often exceeds 7.0 (in contrast to the pH within the plant cells, for example).  The result of this elevated foliage surface pH is an increase in the dry deposition flux of SO2 and NO2 by a factor of 2 to 10 close to the sources, relative to using a foliage pH of 6.68.  Downwind of the sources, the foliage pH is often near neutral to moderately acidic, leading to decreased dry deposition of SO2 and NO2..  Together, these changes in pH result in an exponential decrease in the dry deposition fluxes with increasing distance from the Oil Sands sources.References Miller, S. J., Makar, P. A., and Lee, C. J.: HETerogeneous vectorized or Parallel (HETPv1.0): An updated inorganic heterogeneous chemistry solver for metastable state NH4+–Na+–Ca2+–K+–Mg2+–SO42––NO3––Cl– based on ISORROPIA II, Geosci. Model Dev. Discuss. [preprint], https://doi.org/10.5194/gmd-2023-159, in review, 2023.
Experimental evidence of non-equilibrium water flow during bare-soil evaporation
Authors: Iden Sascha , Diamantopoulos Efstathios , Sut-Lohmann Magdalena , Durner Wolfgang
Published: March 2024

The Richards equation is de facto the standard model for simulating variably-saturated water flow in soils. It is based on the assumption that water content and matric potential are in instantaneous equilibrium. Their relationship is the water retention curve which is widely used to evaluate soil quality, to determine the effective pore-size distribution, and to derive the soil hydraulic conductivity curve. Experimental data collected over the last 6 decades show that the water retention curve depends not only on the history of wetting / drying, but also on the dynamics of water flow (transient vs equilibrium conditions). Many studies present experimental evidence on the hypothesis that the faster the water flow in soils, the more pronounced is the deviation of the dynamic retention curve from the equilibrium one. In this contribution, we present experimental data which show that these effects also occur during experiments in which water flow can be characterized as relatively slow. We conducted evaporation experiments on two soils, a sand and a silt loam, and varied the evaporation rate. Evaporation rates were controlled by wind speed, and flow interruptions were induced by temporarily covering the samples. We measured soil temperature and matric potential at different depths. The results show a relaxation of the matric potential with changes in wind speed, in particular during the flow interruptions. A complete analysis of the data requires a distinction between the vertical redistribution of moisture caused by changes in the evaporation rate, the effect of temperature on matric potential, and the “true” nonequilibrium between matric potential and water content. Contrary to the general assumption that bare-soil evaporation is a slow process during which equilibrium between water content and matric potential is ensured, our results show that dynamic nonequilibrium occurs even in the case of relatively slow, upward water flow. This results in a shift in the dynamic water retention curve estimated from evaporation experiments, indicating that more water is retained in the soil when water is flowing, as compared to static experiments.
Uranium-isotope records of global ocean deoxygenation during the Early Aptian Oceanic Anoxic Event (OAE 1a)
Authors: Percival Lawrence , Dickson Alexander , Basu Anirban , Castro José , Ruiz-Ortiz Pedro , Bottini Cinzia , Erba Elisabetta , Mutterlose Jörg , Goderis Steven , Claeys Philippe
Published: March 2024

The Phanerozoic Aeon was marked by several variations in global oxygenation levels, occuring both gradually over multi-million year timescales and also more abruptly as transient perturbations lasting typically a million years or less. Following an overall trend of rising atmospheric oxygen levels in the mid–late Palaeozoic, marine redox conditions are thought to have been close to modern by the time of the Cretaceous Period (145–66 Ma). However, the Cretaceous Period also featured multiple episodes of geologically abrupt depletions in seawater oxygen levels, known as Oceanic Anoxic Events (OAEs), one of the most severe of which occurred during the Early Aptian (OAE 1a, ~120 Ma). This environmental crisis is thought to have been triggered by major carbon emissions related to the volcanic formation of the Greater Ontong-Java Plateau. Several OAE 1a sites are marked by the preservation of organic-rich laminated shales, indicative of oxygen-depleted conditions in the water column and at the sediment-water interface. However, the relative paucity of Early Aptian open-ocean sedimentary records means that the degree to which anoxic conditions spread throughout the global marine realm during OAE 1a remains poorly constrained.Here, we aim to verify the nature of seawater oxygen levels prior to, during, and after OAE 1a, using uranium-isotope (δ238U) records of that event. Under iron-reducing conditions, soluble U6+ transforms to insoluble U4+, which is associated with a pronounced isotopic fractionation in favour of 238U in U4+ ions. Thus, the subsequent sequestration of U4+ in organic-rich sediments causes depletion of 238U in the water column and a shift to an isotopically lighter δ238U composition of seawater. This change in marine δ238U is recorded by carbonates precipitated in seawater. Thus, δ238U trends across various records of OAE 1a enable the hypothesis that background Cretaceous ocean redox conditions were comparable to today to be tested, and the change in geographic extent of anoxic water masses during the environmental change quantified. By further comparing the δ238U data with other geochemical proxies (e.g., carbon-isotope evidence of organic-matter burial; osmium-isotope evidence of volcanism), we further explore the causes and environmental consequences of transient ocean redox fluctuations in the Early Cretaceous oceans.
Can Jupiter's atmospheric metallicity be different from the deep interior?
Authors: Müller Simon , Helled Ravit
Published: March 2024

Updated formation and structure models of Jupiter predict a metal-poor envelope. This is at odds with measurements of the Galileo probe, which measured an enrichment of about two to three times solar. Additionally, Juno data imply that water and ammonia are enriched compared to a solar composition. Here we explore whether Jupiter can have a deep radiative layer that separates the upper atmosphere from the deeper interior. The origin of this radiative layer could be related to a hydrogen-transparency window or a depletion of alkali metals. We show that the accretion of heavy elements during Jupiter's evolution can lead to the desired atmospheric enrichment and that this configuration is stable over billions of years. The origin of the heavy elements could be due to cumulative impacts of small objects or from a large impact. We conclude that most of Jupiter's molecular envelope could have a solar composition while its uppermost atmosphere is enriched with heavier elements. The origin of this enrichment is likely the accretion of solid objects. This possibility resolves the long-standing mismatch between Jupiter's interior models and measurements of its atmospheric composition. Furthermore, our results imply that the measured atmospheric composition of exoplanets does not necessarily reflect their bulk compositions. We also investigate the possibility of the enrichment coming from the deeper interior and show that the observed enrichment is highly unlikely due to the erosion of a dilute core. This scenario is inconsistent with evolution calculations, the suggested deep radiative layer, and published interior models.
Using U-Pb Carbonate Geochronology to constrain the timing of fault development and fluid source evolution in an inverted continental rift basin.
Authors: Connolly Joe , Anderson Mark , Mottram Catherine , Price Gregory , Sanderson David
Published: March 2024

The Bristol Channel Basin (BCB) is a small continental rift basin that developed along the eastern margin of the North-Atlantic during the Mesozoic. Relatively minor basin inversion occurred during the Cenozoic. It has been extensively studied due to the exceptional exposure of faults along both margins of the basin. Widespread calcite mineralisation of overprinting fracture networks documents fluid partitioning along these structures over time. However, the temporal evolution of deformation has been constrained solely from the relative timing of structures in the field and through comparisons with other basins in the region. This has made detailed modelling of how structures have evolved during basin development and later inversion problematic. In this study we succesfully use U-Pb carbonate geochronology on low U samples (
Relative sea level rise trends and projections up to 2150 along the Italian coasts: implications for coastal flooding
Authors: Anzidei Marco , Vecchio Antonio , Alberti Tommaso , Serpelloni Enrico , Grezio Anita
Published: March 2024

We focus on the current and future sea level (SL) trends along the Italian coasts which are affected by spatially variable rates of Vertical Land Movements (VLM) in response to tectonics and anthropic activities. Since VLM play a crucial role in local sea level rise along the coasts, they need to be estimated and incorporated in the analysis for more affordable sea level rise projections.To estimate the current VLM rates we used geodetic data from about 27 years of continuous GNSS observations at a set of stations belonging to Euro-Mediterranean networks located within 5 km from the coast. Revised SL projections up to the year 2150 are provided at a set of points on a geographical grid and at the location of some tide gauges belonging to the PSMSL network, by including the estimated VLM in the SL projections released by the IPCC in the AR6 Report. Our results show that the current IPCC projections are not representative of the expected future sea levels since they do not properly consider the effects of tectonics and other local factors. Here we show that revised multi-temporal sea level projections at 2030-2050-2100 and 2150 show significant differences with respect to those of the IPCC for different Shared Socio-economic Pathways and global warming levels. Finally, our results indicate that about 1600 km of length and 10.000 km2 of the considered Italian coasts are yet exposed to flooding risk, with enhanced impacts on the environment, human activities and coastal infrastructures, in particular in 39 coastal plains. With the above scenarios, and especially in case of eventual instabilities of the Greenland and west Antarctica ice sheets, the effects of extreme meteorological events and tsunamis, will soon amplified along the Italian coasts, with serious concerns for main and small islands. Therefore, actions are needed to support vulnerable populations to adapt to the expected relative sea level rise by the end of this century and beyond.
Channel mobility-driven hydrological connectivity controls water surface area variations in oxbow lakes
Authors: Ahmed Joshua
Published: March 2024

Oxbow lakes serve as rich habitats for wildlife, natural contaminant filters, and an essential source of sustenance and prosperity for riverine communities around the world. Despite their significance, little is known about their interannual hydrological variations, how these are controlled, and the impact they have on lake physiochemistry. Without an understanding of how these environments currently function, it will be challenging to protect them from the pressures of climate change and land use conversion, thus threatening their ability to deliver a range of ecosystem services in the future. Data from 76 recently formed (1984-2022) oxbow lakes along two near-pristine Amazonian tributaries in Bolivia are presented to evaluate the role of rainfall and channel connectivity in driving variations in water surface area (WSA) over interannual timescales. These results were extracted from multispectral satellite imagery using a range of semi-automated workflows leveraging a range of band rationing techniques. Over interannual timescales, lakes were observed to diminish by up to 97% and increase by over 200% relative to the WSA in the previous year. Seasonal rainfall and the proximity of the active channel were used to discern predominant controls on WSA variations and demonstrated that active channel proximity was important, particularly where established flow pathways were present. Rainfall was more important for lakes in the distal floodplain. Changes in hydro-climate, flow regulation, and land use will alter these key hydrological controls in fluvial systems, thus potentially altering the functioning of lakes in the future and threatening those communities who rely on the lakes for survival.
Integrated Bayesian Approach for Station Location and Orientation in Marine Active-Source Seismic Shear Wave Studies
Authors: Cryder Morgan , Dunn Robert , Xu Chong
Published: March 2024

Since the introduction of the ocean bottom seismograph (OBS), it has played a pivotal role in the expansion of our comprehension of the Earth’s interior structure and dynamics. Typically deployed through free-fall from a ship, the position of the OBS on the seafloor and its orientation are initially unknown. When using airgun shots to locate and orient an instrument, a severe downside is the often-limited azimuthal distribution of shots around the OBS, possibly leading to large location and, subsequently, orientation errors. We introduce a novel and efficient method aimed at enhancing the accuracy of station locations in active-source seismic experiments. The approach uses airgun shots recorded as part of the experiment, and integrates both acoustic wave travel time information and waveform polarizations. The inverse problem of station location is formulated in terms of Bayesian inference. At each location of a search grid, the misfit of observed and theoretical water wave travel times and the clustering of polarization data are combined into one probabilistic formulation to map the relative likelihood of a station’s position and orientation. We demonstrate the practical utility of the method via application to the location and orientation of OBS deployed during a recent seismic experiment located across the Hawaiian Ridge. Thereafter, we will use the results to compute radial seismograms, extract the travel times of crustal and mantle S waves, and develop S-wave models of the oceanic lithosphere across the Hawaiian Ridge.
Estimates of Polar Ocean CO2 Uptake from Atmospheric Inverse Analyses 
Authors: Suntharalingam Parvadha , Chen Zhaohui , Ghosh Jayashree
Published: March 2024

Estimates of global scale air-sea CO2 fluxes have traditionally been derived from ocean biogeochemistry models and ocean surface pCO2 data products (Friedlingstein et al. 2022). An alternative means of estimating ocean carbon uptake is provided by atmospheric inversions; these use optimization procedures and data assimilation methods to combine atmospheric CO2 measurements with numerical transport model simulations and prior knowledge of air-sea fluxes. Here we use the GEOSChem-LETKF (GCLETKF) inverse system (Chen et al. 2021) in conjunction with atmospheric observations from the NOAA-GML surface CO2 measurement network to derive grid-scale air-sea CO2 flux estimates for the period 2000-2017. We focus, in particular, on estimates of CO2 uptake by the polar oceans (Southern and Arctic oceans). These  regions have accounted for a significant component of global oceanic carbon uptake  in recent decades (e.g., more than 20% of global ocean uptake, in comparison to their ocean areal  extent of < 10%).We present GCLETKF estimates of ocean CO2 uptake at global and regional scales, and assess the robustness of our results with a suite of metrics that include model concentration bias, CO2 flux error reduction, and comparison to independent atmospheric measurements. GCLETKF flux estimates for the 2000-2017 period indicate regional CO2  uptake of 0.1-0.2 PgC/year for the Arctic,  and  0.45-0.55 PgC/yr for the Southern Ocean. We also provide summary estimates of the  interannual variations and  decadal-scale trends of the polar ocean carbon fluxes, and compare the GCLETKF results  to estimates derived from global ocean biogeochemistry models and surface ocean pCO2 data products.  
Change in eruption location in Kerguelen hotspot and Kinematic Reconstruction of Rajmahal Trap:  Implications for Cretaceous to present day Geodynamics of Indian plate
Authors: Guleriya Simran , Beniest Anouk , Tiwari Sudheer Kumar
Published: March 2024

The Rajmahal Traps is one of the two major Large Igneous Provinces (LIPs) that erupted in the Indian subcontinent in the Mesozoic. The trap was the product of activity at the Kerguelen hotspot, located in the Indian Ocean, that initiated around 117 Ma. Earlier studies on the eruption location of the Rajmahal trap show that its location does not coincide with the present-day location of the Kerguelen Hotspot. This difference in the paleo-locations could be the result of mantle dynamics beneath the Indian Ocean during the Cretaceous and has been explained with concepts such as the multiple diapir-single plume model, the migration pathway of the hotspot beneath the mantle, and the complex plume-ridge interaction.In this study, we use paleogeographic reconstruction software GPlates to reconstruct the paleogeography of the Rajmahal Traps on the Indian subcontinent plate in an Antarctica fixed reference frame since 117 Ma to pin-point the paleo-location of the Kerguelen hotspot and eruption location of the Rajmahal trap along with the tectonic changes that the Indian Ocean was encountering. The mantle structure below the Indian Ocean was further studied using publicly available P-wave tomography data. The paleogeographic reconstruction linked to the mantle structure hints towards the presence of a tree-like hotspot-plume structure beneath the Kerguelen hotspot where a deep-seated single plume feeds into various fissures at the surface which are active at different points in time.Our kinematic analysis for the Indian Plate reveals significant changes in the velocity of the plate since the Cretaceous at specific points in time in response to tectonic activities initiated by the plumes present in the Indian Ocean. These activities that link to changes in the velocity include interactions with the Morondova plume (velocity increase at 90 Ma) and Reunion hotspot (velocity increase between 78 – 62 Ma), and other processes like continental collision (velocity decrease at 56 Ma and between 50-43 Ma) and slab pull (velocity increase at 56 Ma). Using this new velocity profile, we have developed a revised velocity model for the drift of the Indian subcontinent since the Cretaceous.
Radiocarbon measurements of archived fish scales reconstruct past carbon cycle changes in a peri-alpine lake
Authors: White Margot , Mittelbach Benedict , Rhyner Timo , Haghipour Negar , Blattmann Thomas , Wessels Martin , Dubois Nathalie , Eglinton Timothy
Published: March 2024

Climate change and other anthropogenic impacts such as nutrient pollution result in perturbations to freshwater systems that alter aquatic carbon cycling. In the alpine Rhine basin, for example, long-term monitoring over the past four decades has documented increasing water temperatures that cause a decrease in the solubility of CO2. However, this same dataset records a small increase in the concentration of dissolved inorganic carbon (DIC) over the same period. This requires increasing inputs of DIC to aquatic systems and an acceleration of the carbon cycle, but the source of this additional carbon is not clear. Possible explanations include increased weathering of bedrock or increased soil organic matter respiration, with sharply contrasting implications for carbon storage and turnover. Radiocarbon (14C) is an ideal tool to distinguish between these different scenarios, as bedrock weathering will contribute 14C-depleted (fossil) DIC whereas increased soil respiration will contribute DIC that is more 14C-enriched (younger). Furthermore, large changes in the atmospheric radiocarbon content over the past century resulting from the testing of nuclear weapons provide a strong signal with which to track the exchange between aquatic and atmospheric carbon pools by examining how lake water DI14C changes through time. Here we focus on Lake Constance, a large peri-alpine lake fed mostly by the alpine Rhine River. We measured natural abundance radiocarbon in archived fish scales collected from Lake Constance over the past 100 years to reconstruct changes in lake water DI14C. These fish scales come from young fish caught in the lake who feed primarily on phytoplankton and thus reflect the 14C of the lake DIC pool. Preliminary measurements of fish scales from the pre-bomb period were 0.78 to 0.79 Fm, reflecting the addition of 14C dead rock-derived carbon from the dissolution of carbonate rocks within the catchment. These values are 14C-depleted compared to present day water column DIC values of 0.82 to 0.84 Fm, where the bomb spike signal persists. Results from fish scales will ultimately be compared with other archives of water column DI14C currently in development, including 14C of chlorophyll degradation products and zooplankton exoskeletons isolated from varved lake sediments. These records permit us to investigate how carbon cycling in the lake and its catchment has responded to anthropogenic perturbations such as warming and nutrient pollution over the past century, with the eventual goal of calibrating isotope enabled carbon cycle models.
Global soil microplastic assessment in different land-use systems is largely determined by the method of analysis
Authors: Wrigley Olivia , Amelung Wulf , Braun Melanie
Published: March 2024

Although microplastics (1 μm - 5 mm, MPs) are increasingly recognised as a novel entity of pollutants, we still lack a basic understanding of their prevalence in different terrestrial environments, such as managed soils. Here, we aimed at elucidating the global MP pollution of managed soils, with specific focus on continental differences, input pathways, and land use types as impact factors, whilst considering the effect of the respective analytical methods on the reported results. After evaluation of 305 sites from 51 studies, we found that the analytical method mostly determined the reported MP load, as analysis of both small and large MPs, use of high density separation solution, and of post-density separation soil organic matter removal yielded significantly higher MP loads. The global means of MP loads benchmarks 2,081 ± 6323 MP items kg-1 soil (global median of 476 (0 - 72,200) MP items kg-1), with 75% of studies located in Asia. Highest mean numbers of MP items were found for Asia and The Americas (2,408 ± 7,194 and 2,138 ±  2,142 MP items kg-1 respectively), with the former being significantly higher than the mean MP concentration of Europe (1,153 ± 1,721 MP items kg-1, p < 0.05). Maximum MP numbers were found for soils under plastic mulching (2,576 ± 8,568 MP items kg-1), followed by greenhouses and polytunnels (1,980 ± 1,200 MP items kg-1), and sludge amendments (1,845 ± 1,925 MP items kg-1). There was no evidence of elevated MP loads in horticultural fields relative to other agricultural management practices (agronomy). Yet, quantitative comparisons were biased by the methodology selected for MP analyses, as looking at the effect size methodology had the largest effect on MP loads. Hence, we conclude that based on the current database, comparisons across studies and input pathways as well as land-use systems are hampered by methodological inconsistencies.
Weed management strategies with Picea abies L. sawmill by-products
Authors: Xotta Valeria , Trespidi Giacomo , Nikolić Nebojša , Otto Stefan , Masin Roberta , Loddo Donato
Published: March 2024

Weeds can cause significant impact on agriculture and require effective management; however, traditional control measures can lead to serious environmental damage. Considering both the need and demand for more sustainable use of pesticides in Europe, regenerative bio solutions are gaining much attention, especially the possibilities for by-product usage. Here, such a possibility was examined using sawdust and bark from Picea abies L., the most common conifer in the Alpine region forestry, known for generating large quantities of these by-products in sawmills.The tests comprised the assessment in Petri dishes of phytotoxic effects on germination and root growth of two weeds Abutilon theophrasti Medik. (ABUTH), Lolium rigidum Gaudin (LOLRI) and two crops Triticum aestivum L. (wheat) and Sinapis alba L. (mustard) treated with P. abies bark and sawdust aqueous extracts at different concentrations (from 0 to 100% v/v). Another test was carried out in pots to evaluate the effects of these by-products as mulches and phytotoxicity by incorporation in the first 10 cm of soil. For this trial, Amaranthus retroflexus L. (AMARE) and Glycine max L. (soybean) were added to the species used in the Petri test.The by-product incorporation test showed no germination reduction but increased AMARE germination by 9%. This corresponds to the Petri tests where no effect on germination was observed. Regarding root elongation, sawdust extract shows no relevant effects except for 35.3 % reduction in mustard root growth at the 100 % v/v concentration. Bark extracts were more effective, particularly at the highest extract concentration (100 % v/v), reaching root growth reduction from 41.8 to 69 % for all species. The most susceptible species was LOLRI with root growth reduction by 44.5 and 69 % at concentrations of 40 and 100 % v/v, respectively.Conversely, bark and sawdust mulching effectively reduced germination in species with smaller seeds (-51% in AMARE and mustard, -27% in LOLRI), while having little or no effect on the others. In addition, mulching delayed emergence of all species by no more than one day compared to untreated. LOLRI and ABUTH showed the most significant germination slowdown with an average of 35% at the higher mulching dose of 2.25 kg/m2.As an innovative solution, the use of sawmill by-products as mulch seems to be the most viable strategy for sustainable weed control and increasing its use is desirable considering the environmental benefits. Results suggest that the mulching effect is purely physical, while releasing allelopathic compounds from by-products does not affect the species germination. The development of natural herbicides from waste bark and sawdust has not yielded satisfactory results, but the presence of phytotoxic compounds, especially in bark extracts, is suspected. Chemical analyses may be carried out to assess their presence.
Continental slivers in oceanic transform faults controlled by tectonic inheritance
Authors: Balázs Attila , Gerya Taras , Tari Gabor
Published: March 2024

The ocean floor shows variable morphological features, transtensional and transpressional structures, magmatic and amagmatic domains. Surprisingly, continental blocks separated from the continental margins from 100s or 1000s km distance have been occasionally reported, however, their origin remains debated.We conducted 3D magmatic-thermo-mechanical numerical experiments with the code I3ELVIS to simulate the dynamics of continental rifting, continental proto-transform fault zones, and eventually the formation of persistent oceanic transform faults and their connection to mantle melting. Numerical modelling results allow to analyze the first order features of passive and transform margins and oceanic basins. Our models explain the evolution of continental blocks entrapped between oceanic spreading ridges bounded by strike-slip fault zones inherited from the preceding continental rifting stage. The formation of such continental slivers is controlled by the relative timing between the onset of oceanic spreading and strain localization along strike-slip fault zones. This is connected to the rheology of the plates and also linked to different thermal gradients, divergence velocities, melting conditions and surface processes. Furthermore, we discuss the formation of zero-offset V-shaped oceanic fracture zones and the along-ridge variation of oceanic crustal thicknesses. Our model results are compared with observational data from the Romanche transform of the Equatorial Atlantic, the East Greenland Ridge and Newfoundland Ridge in the northern Atlantic, the Zabargad Islands in the Red Sea and the Davie Fracture Zone.
Soil restoration for urban areas: Exploring water-related ecosystem services and hydrological functionality 
Authors: Zupanc Vesna , Zeiser Anna , Rath Sebastian , Strauss Peter , Grčman Helena , Zupan Marko , Gantar Anja , Pečan Urša , Pirnat Matjaž , Weninger Thomas
Published: March 2024

The challenge of restoring degraded landscapes or ecosystems and recultivating them in a way that maximizes the multifunctionality of the artificial soil depends on the extent of soil degradation and its causes. The process of land restoration is expensive, time-consuming and requires careful planning and collaboration between different stakeholders and sectors. In densely populated regions such as Central Europe, there are two major types of artificial soil ecosystems: restoration of landfills or mining pits and urban green infrastructure (e.g. urban tree sites, stormwater retention areas). To compensate for the increasing scarcity of arable land, soils with unfavorable properties must be improved and degraded land must be rehabilitated in order to fulfill soil functions and promote agricultural production.Engineered soils offer a solution for construction the top layer that allows the restored ecosystem to function. Such soils are made from excavated material and other mineral or organic waste and are composed to provide suitable conditions for plant growth and other ecosystem services provided by the soil.As the need for green spaces in urban areas is also increasing, e.g. to adapt and mitigate the urban heat island effect, soil is needed as a habitat for plants and engineered soil mixtures are required depending on the target location and purpose. Soil mixtures with suitable chemical, physical, biological and geotechnical properties (i.e. physical structure) are needed, which are suitable for the restoration of topsoil for various purposes (e.g. mining reclamation, urban greening) and can be used for the near-natural composition of functional soil layers suitable for reclamation and plant growth. Soil structural properties such as infiltration rate, pore volume and water retention capacity are crucial for the functionality of restored soils in the water cycle, especially in view of the increasing challenges posed by ongoing climate change.The aim of this study is to provide a comprehensive overview of the experiences made at research sites in Slovenia and Austria with the application of engineered soils for the restoration of degraded areas. The focus of the contribution is set on different regulatory requirements and methods to ensure the proposed soil hydrological functionality.This research has been financed by ARIS BI-AT-22-23-019, LIFE20 IPE/SI/000021 ReStart and OEAD WTZ SI 01/2023.
Biomass quality of rich fen bryophytes along the temperate to subarctic gradient sheds light on possible effects of climate change on peat formation in fens
Authors: Kozub Łukasz , Jaszczuk Izabela , Kucharzyk Jan , Jabłońska Ewa , Kotowski Wiktor
Published: March 2024

Introduction:Fens, unlike bogs, are mires fed by ground or surface water, usually enriched by minerals and nutrients, which allows them to support high and specific biodiversity. Fens are dominant mires of the more continental temperate areas and the Arctic but they are also common in some of the boreal regions. Even though much less recognized than bogs, they remain globally important carbon stores and sinks. Their major peat builders are sedges and so-called brown mosses (non-Sphagnum bryophytes) which have been much less studied in the context of biomass quality than Sphagnum species. In the presented study we aimed to quantify the biomass quality (decomposability) of the common fen bryophytes along more than 15 degrees south-to-north transect.Material and methodsWe studied the biomass quality of fen bryophytes in three regions: temperate fens of NE Poland, mid-boreal Trøndelag, and sub-arctic Finnmarksvidda (both latter in Norway). Studied species were Campyllium stellatum, Scorpidium cossonii, Sphagnum warnstorfii and Tomentypum nitens. In each region, mosses were collected from several sites during the summer of 2022. Each collected moss sample was divided into two. One was quickly dried and the latter was kept alive and later grown in a common garden in standardized conditions, for more than a month, to produce new biomass. Both the biomass collected in the field and the new biomass produced in the common garden experiment were analysed with NIR spectroscopy to assess their biomass quality. We compared the impact of origin on biomass quality of both original biomass and the one produced in common conditions using mixed effect models with location and species as the random factors.ConclusionsThe obtained results shed light on the possible impacts of climate warming on peat formation in fens. Assuming that fens will maintain their integrity in the course of climate change, this change may impact the peat-forming potential of fens via changes in bryophyte community composition as well as by impacting the performance and biomass quality of the locally occurring species. Thus studying bryophyte biomass quality along the climatic gradient might help us to better predict the future of carbon accumulation in fens.
Clouds of bubbles and droplets; formation and distribution under breaking waves
Authors: Mostaani Arsalan , Nordam Tor , Davies Emlyn J. , Steinvik Andreas
Published: March 2024

Formation of bubble clouds under breaking waves and whitecaps is a prominent phenomenon in quantifying the air-sea gas exchange process. The size distribution of bubbles will impact the bubble cloud properties such as volume, concentration, and intrusion depth over time and space. The number, size, and shape of the bubbles are highly associated with the intensity of the breaking wave (i.e., wave steepness). While for low-intensity spilling waves, the rolling surface jet and the subsequent secondary (splash-up) jets may generate clouds of bubbles with nearly similar length and time scales, however under high-intensity plunging waves, a more complicated plume-cloud of bubbles may be generated due to the frontal plunging jets. In the case of an oil spill at sea, breaking waves will also lead to breakup and entrainment of a surface slick into smaller submerged droplets.A series of lab experiments were conducted in a linear wave flume with a piston-type wave maker, investigating bubble clouds and oil droplets and their spatial and temporal properties under 2-D spilling and plunging breakers. In this work, the SINTEF SilCam camera system with a uniform LED backlight was utilized to capture images of the bubbles and droplets at high frequency. The PyOpia open-source image processing library was enhanced and subsequently trained to capture the overlapping bubbles, droplets, and individual bubbles with highly deformed shapes.In the present poster, results extracted from the image analysis are described. We show depth- and time-resolved size distributions for both bubbles and oil droplets. Some of the size-distribution models and scales presented in the literature, for both air bubbles and oil droplets, are examined to evaluate their performance with current data.