bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of an hybrid GMPE-less ShakeMap implementation for real-time ground shaking maps reconstruction
Authors: Fornasari Simone Francesco , Pazzi Veronica , Costa Giovanni
Published: February 2023

Ground shaking maps are an essential tool for seismic monitoring and civil defence operations as they provide information about the area and amplitude of the ground motion relative to a seismic event.Such maps are developed integrating spatially sparse data recorded by the stations, which also provide a constraint to the process, and theoretical values obtained from ground motion prediction equations (GMPEs), given the magnitude and location of the earthquake, also accounting for local site effects.One of the problems arising during the development of a real-time implementation of these techniques is the lack of information in real-time needed to compute the GMPE.One possible solution to the problem is to develop algorithms that can constrain the interpolation process using only the ground motion parameters recorded at the stations (Fornasari et al., 2022).We propose a hybrid model combining the conditioned multivariate normal distribution (MVN; Worden et al., 2018) technique adopted by ShakeMap and a neural network replacing the GMPE.The neural network provides a purely data-driven approximation of the GMPE results based only on the spatially sparse data from the stations, with possible correction for the site effects. The network is trained using a supervised approach with labelled data obtained from GMPEs used for the Italian territory. Moreover, by limiting the use of a neural network to a specific task we improve its explainability with respect to end-to-end models.This approach is easily integrable into the existing workflow, combines the well-studied interpolation techniques and neural networks in a clearly explainable structure, and provides high-resolution estimates of the ground-shaking fields in real-time with potential relevance in the context of early warning. References:Simone Francesco Fornasari, Veronica Pazzi, Giovanni Costa; A Machine‐Learning Approach for the Reconstruction of Ground‐Shaking Fields in Real Time. Bulletin of the Seismological Society of America 2022; 112 (5): 2642–2652. doi: https://doi.org/10.1785/0120220034.C. Bruce Worden, Eric M. Thompson, Jack W. Baker, Brendon A. Bradley, Nicolas Luco, David J. Wald; Spatial and Spectral Interpolation of Ground‐Motion Intensity Measure Observations. Bulletin of the Seismological Society of America 2018; 108 (2): 866–875. doi: https://doi.org/10.1785/01201702
Global sensitivity analysis of water level response to harmonic aquifer disturbances considering wellbore effects
Authors: Xing Yixuan , Liu Quan , Hu Rui , Ptak Thomas
Published: February 2023

Abstract: Oscillatory water level is often observed in groundwater monitoring wells when the aquifer is disturbed by some periodic pressure sources, such as oscillatory hydraulic test, ocean tide, and far-field seismic wave. The amplitude attenuation (A) and phase shift (P) between the source and water level response are utilized to estimate aquifer properties in many related studies. Water level response, in essence, is not only affected by aquifer parameters but also the characteristics of disturbance source and wellbore effects, which are determined by multiple parameters and the highly nonlinear well-aquifer system. To clarify the impacts of A and P on all relevant parameters, a global sensitivity analysis of water level response to harmonic aquifer disturbance is conducted in this study. A general numerical model of water level response that integrates different types of sources and considers wellbore effects is first introduced. Based on the quasi-Monte Carlo method, nine relevant parameters regarding wellbore geometry, aquifer property, and characteristics of the source, are sampled within their normal ranges. A data-driven model of the water level response to the selected parameters is trained and cross-validated using the random forest regression method. The global sensitivity analysis of the A and P is then implemented by using the variance-based method.  The first-order Sobol index shows that for both A and P, the oscillatory period of the disturbance source is the most sensitive factor among others. The second-order Sobol index indicates that the interaction between the period of disturbance source and water column height in the wellbore is the most important to A and P. preliminary results show that wellbore effects have significant impacts on water level responses, especially under a high-frequency disturbance.
Variability of (234U/238U) in surface water and tufa deposits: A study in the Mono Basin, California, USA
Authors: Lin Ke , Hemming Sidney R. , Ali Guleed , Lin In-Tian , Su Chih-Chieh , Stine Scott W. , Hemming N. Gary , Wang Xianfeng
Published: February 2023

Uranium concentrations and 234U/238U activity ratios (δ234U) of Earth’s surface waters can provide independent and complementary information on changes in weathering regime and hydroclimate. The response of δ234U variation in surface waters in US Great Basin to climate change however remains unclear, which brings ambiguities in interpreting δ234U in aquatic carbonate deposits. Here, we analysed U concentration and δ234U in a suite of surface waters (creeks, springs and lake) as well as tufa deposits from the last glacial lake highstands in the Mono Basin, California, USA to assess the modern uranium budget in the lake water and the controlling factors on its δ234U. We find that U concentrations in groundwater springs are about one order of magnitude higher than those of creek waters. Hence, even though springs only deliver about 15% of annual inflow to the lake, they contribute 70% of U in the lake water. The residence time of U in lake water is calculated to be approximately 15,000 years, on the same order as those of Li, Na, and Cl, but significantly longer than those of alkaline earth elements. The δ234U in Mono Lake water is 180‰, same as in modern-day tufa deposits. The δ234U in lake highstand tufas is ~ 220‰, suggesting much more enhanced physical weathering associated with mountain glacial activities in the basin, even though chemical weathering was also stronger due to increased precipitation. On the other hand, the higher δ234U values (~ 250‰) in modern creeks and springs is consistent with the overall dry environment and stronger physical weathering in the basin. The 40‰ decrease in δ234U of lake water however cannot be explained by radiative decay. We hypothesis that lake water was more frequently stratified in the past, during the last glacial in particular, and the resulted anoxic environment in deep lake water has probably facilitated precipitations more enriched in 234U. 
The WorldFAIR project: enabling global interdisciplinary cooperation on integrating FAIR Data policy and practices in geochemistry with ten other disciplinary groups.
Authors: Farrington Rebecca , Prent Alexander , Wyborn Lesley , Rawling Tim , Klöcking Marthe , Lehnert Kerstin , Elger Kirsten , ter Maat Geertje , Hezel Dominik , Hodson Simon
Published: February 2023

‘WorldFAIR: Global cooperation on FAIR data policy and practice’ is a European Commission funded project composed of 11 discipline and cross-discipline case studies drawn together by CODATA, the Committee on DATA of the International Science Councils Committee on DATA, and is supported by the Research Data Alliance. WorldFAIR is a diverse, global community effort that currently has 19 partners located in Africa, Australasia, Europe, and North and South America, representing organisations from research, government and industry. The 11 individual case studies are drawn from Chemistry, Nanomaterials, Geochemistry, Social Surveys, Population Health, Urban Health, Biodiversity, Agriculture, Oceans, Disaster Risk Reduction and Cultural Heritage. The WorldFAIR project aims to focus on the interoperability and reusability of research data products from both within and across disciplines by creating a Cross-Domain Interoperability Framework (CDIF).The foundation of the CDIF will be a series of FAIR Implementation Profiles (FIPs) which will be used as a methodology for individual communities to express their FAIR practices and decisions for each of the 15 individual FAIR guiding principles. As an example of how this will work, the WorldFAIR’s Geochemistry case study is led by OneGeochemistry, an international network of national geochemical data infrastructure organisations. Initially an informal network with representatives from AuScope (Australia), GEOROC (Germany), EPOS Multi-scale Laboratories (Europe), EarthChem (US) and AstroMaterials (US). With the advent of WorldFAIR, OneGeochemistry has formalised it’s governance structure and is now a CODATA Work Group. Over the life of WorldFAIR, OneGeochemistry will work towards developing a community prototype FAIR Implementation Profile(s) for individual geochemical techniques, including the minimum defined variables, through workshops and consultations, and subsequently be responsible for their communication, publication and dissemination. The Geochemistry case study will work closely with the Chemistry case study and leverage relevant chemical standards and vocabularies wherever possible.Through the development of community lead FAIR Implementation Profile(s) for geochemistry within a global Cross-Domain Interoperability Framework (CDIF), WorldFAIR and OneGeochemistry are both advancing the adoption of the FAIR data principles within Geochemistry and simultaneously enabling interoperability of geochemical research data products across the other ten discipline case studies.
Carbon dynamics of a controlled peatland restoration experiment in Norway
Authors: Bekken Michael , Pirk Norbert , Vatne Astrid , Tallaksen Lena , Westermann Sebastian , Larsen Poul , Ibrom Andreas , Steenberg Larsen Klaus , Knutson Jacqueline , Dörsch Peter
Published: February 2023

Norway has the third greatest extent of peatlands in Europe, after Finland and Sweden. Norwegian peatlands cover nearly 30 000 km2 or 7.7 percent of Norway’s land area. However, 6500 km2 of these peatlands have been drained for forestry or agriculture and are estimated to emit approximately 6 Mton CO2 annually, accounting for 11 percent of Norway’s total carbon emissions. In 2016, the Norwegian Environment Agency and the Norwegian Directorate of Agriculture embarked on a peatland restoration plan to reduce greenhouse gas emissions and improve the ecological conditions of drained and degraded peatlands in Norway. Since then, over 100 peatland sites have been restored. However, only one of these sites is being actively monitored to determine the effect of restoration on carbon fluxes, making this site critical to understanding carbon dynamics of restored peatlands in Norway. The site, located in the Regnåsen and Hisåsen Nature Reserve (Trysil Municipality, Innlandet county) consists of two study areas that are sub-catchments of the same watershed, cover approximately 0.5 km2, and are separated by 0.5 km. Both areas were drained in the 1960s, with a network of drainage ditches totaling approximately 4000m. One of the areas was restored in 2021 by constructing 318 dams in the drainage ditches, while the other area remains drained as a control. In 2019 eddy covariance towers were installed to track vertical CO2 and CH4 fluxes on each site. In addition, DOC, DIC and water discharge measurements were taken to estimate lateral carbon transport, and soil samples were taken to estimate carbon stocks. Preliminary results indicate that CO2 fluxes have decreased and CH4 fluxes have increased in the restored site as compared to the drained site, and that vertical carbon fluxes account for over 90% of carbon transport on both sites. This project is coordinated by the LATICE (Land-ATmosphere Interactions in Cold Environments) project at University of Oslo. The results of this study will assist the Norwegian Environment Agency in shaping the next phase of the peatland restoration work in Norway.
Use of global climate and weather reanalysis to fill meteorological time series gaps
Authors: Trotta Carlo , Vuichard Nicolas , Pastorello Gilberto , Manco Ilenia , Mancini Marco , Mercogliano Paola , Papale Dario
Published: February 2023

Meteorological is an essential input for many terrestrial ecosystem models to simulate energy, water and carbon exchanges between the surface and the atmosphere. A significant improvement in the comprehension of the processes represented in the models is linked to the installation of the eddy covariance (EC) towers.In particular the EC carbon and energy data are utilized by the modelers to develop and parameterize the models and evaluate their  performances. Continuous, gap-free main in-situ meteorological time series are crucial for the EC fluxes processing (mainly gap-filling and partitioning) but are also used as input for simulations of many different models. Different approaches exist for filling the gaps present in the meteorological data collected at the EC sites. In the standard FLUXNET processing (ONEFlux) a downscaled approach is used (Vuichard and Papale 2015), which was originally based on the ERA-Interim dataset, and now uses ERA5.Here we present the results of a modified method where the downscaling has been also compared across three different reanalysis datasets (ERA5 hourly data on single levels and ERA5-Land from Copernicus and a CMCC product at 2.2 km produced for the whole Italian territory). Our results show that the reanalysis product used has an impact on the performance of the overall gap-filling of data and we suggest the implementation of a new strategy in the standardized processing chains.
Evolution of Turbulence Anisotropy in the Outer Heliosphere and Transport of Pickup-ion-associated Energy in Turbulence Channel : Voyager 2 Observations
Authors: Zhu Xingyu , He Jiansen , Duan Die , Lin Rong
Published: February 2023

The solar wind plasma environment in the outer heliosphere is different from the inner heliosphere where has been widely studied. An important factor influencing the turbulence evolution in the outer heliosphere is the pickup ions, primarily originated from neutral atoms from the interstellar medium. Pickup ions are not readily assimilated by the background solar wind plasma and thus provide extra free energies which can drive ion-scale instabilities. The unstable growing waves will end up taking part in the turbulent energy transport. However, how these pickup-ion-associated energies involve in turbulent cascade and influence turbulence evolution have yet to be studied. In this work, we study the solar wind turbulence evolution from 1 au to 33 au based on Voyager 2 magnetic field measurements. We study 305 time intervals listed in Pine et al. (2020). In all these time intervals, no ion-scale bumps are present in the turbulent spectra. We find that: (1) The perpendicular and trace power spectra (and ) still follow a Kolmogorov-like spectrum until 33 au while the parallel power spectrum transits from -2 to -5/3 at heliocentric distance R~10 au; (2) At periods 10 s <τ< 500 s, quasi-parallel propagation dominates in 1 au<R<7 au, with quasi-perpendicular propagation gradually emerging at R>5au. For R > 7 au, oblique propagation becomes a primary component. (3) At larger periods of τ>100 s, increases with propagation angle in 1 au<R<5 au, and in contrast decreases with propagation angle at R>5 au due to the enhanced power level at propagation angles smaller than . We suggest that such enhancement may derive from the injection of the wave energy from the pickup ion source into the background tubulent cascade , and the injected wave energy is transferred across scales withou leaving bumps in or .
Local Insolation Drives Afro-Asian Monsoon at Orbital-Scale in Holocene
Authors: Wen Qin , Liu Zhengyu
Published: February 2023

Insolation changes play an important role in driving monsoon changes at orbital time scales. One key issue that has remained outstanding is whether the Asian monsoon is driven by local insolation from the Northern Hemisphere (NH) or remote insolation from the Southern Hemisphere (SH) at orbital band. Here, we perform a set of sensitivity experiments to quantify the impacts of local and remote insolation changes on the Afro-Asian summer monsoon at 11 ka BP relative to the present. We show that the Afro-Asian summer monsoon is overwhelmingly driven by the precession induced local insolation change in the tropical-subtropical NH. The insolation from NH high latitudes also affects the Afro-Asian summer monsoon. In contrast, the insolation from SH plays a negligible role. Our model experiments support the idea that the Afro-Asian summer monsoon are driven predominantly by the direct forcing of NH low latitudes summer insolation for the Holocene.
Drivers of Sedimentary Pyrite δ34S Values - at Present and in the Past
Authors: Mertens Cornelia , Hemingway Jordon
Published: February 2023

The most important sulfur sink from a global redox-perspective is diagenetic pyrite produced in marine sediments. The amount and isotopic composition of this pyrite is thought to reflect environmental and physical properties of the ocean. This includes sulfate reduction rate, sulfate concentration, sedimentation rates, organic carbon and reactive iron concentrations and reactivities, porosity of the sediment etc. Our goal is to identify the main drivers that can explain the majority of observed sulfur isotopic composition in pyrite. To this end, we use a diagenetic model and calculate theoretical profiles for organic carbon, reactive iron, and a number of sulfur species and their isotopes in marine sediments. We calibrate our model using 216 sedimentary cores from a wide range of environmental conditions and locations from across the world. The model allows us to calculate burial rates and isotopic composition of pyrite in marine sediments on a global scale as well as infer drivers of the Phanerozoic pyrite d34S record. We show that isotopic composition of pyrite is determined by only three variables: the ratio of sulfate to organic carbon, the ratio of reactive iron to organic carbon, and the porosity. Based on this, we reinterpret Phanerozoic d34S trends as recording a shift in the locus and environmental conditions where pyrite is formed, rather than a change in microbial sulfate reducer fractionation.
Sedimentological characterization of geological cores from marginal lakes in the Salar de Atacama
Authors: Piggot Alan M. , Reid R. Pamela , Oehlert Amanda M.
Published: February 2023

Although thought to be high-resolution archives of paleoenvironmental changes, subsurface sediments deposited in saline lakes situated in salar environments have rarely been studied. To address this knowledge gap, sediment cores of varying depths ranging from 0.42 to 2.2 meters were collected from four saline lakes along the eastern margin of the Salar de Atacama, Chile. Characterization included sedimentological descriptions of lithification, sedimentary structures (microbial mats and microbialites), and color, as well as discrete measurements of total organic carbon content. Radiocarbon analysis was conducted on organic matter in the sediments.  The recovered subsurface lithologies were heterogenous in color, stratigraphic features, and age dates, especially when compared between the lakes. Intervals of coarser sediment in the Soncor system lakes Chaxa, Burros Muertos and Barros Negros, appeared to be crystalline and were likely precipitated during periods characterized by higher salinity lake waters. Sediment cores collected from the Soncor system were broadly characterized by low total organic carbon content and punctuated intervals of coarse grained material deeper in the core. In the core collected from Aguas de Quelana, variations in lithology and hardgrounds were commonly observed. In concert, these results suggest that the eastern periphery of the salar was impacted by changes in salinity and water depth as these wetland area experienced changes in extent as a result of changes in wet and dry periods. Radiocarbon dating conducted on organic matter sampled at 4 intervals from each core revealed ages that were significantly older than expected, possibly due to local reservoir effects and subsurface hydrological dynamics. There were five age reversals documented in the transect of cores suggesting that the sources of radiocarbon may have changed over time. Results indicate that the geologic records of saline lake environments are as heterogeneous through time as they are in space.
Integration of lake modeling and paleolimnological records to perform long-term simulations of water quality in Lake Geneva over 250 years (1850–2100 period)
Authors: Soares Laura , Desgué-Itier Olivia , Domaizon Isabelle , Barouillet Cecilia , Jenny Jean-Philippe
Published: February 2023

Lake systems are facing long-term (>150 years) changes around the world acting on multi-decadal to centennial scales. Historic temperature warming at global scales, projected to continue by the end of the century, acting concomitant with eutrophication has modified ecosystem functioning in complex ways. Process-based lake models have emerged as powerful tools to assess the effects of climate and human activities on ecosystems, as well as the responses under future scenarios since they take into account the processes in the boundaries lake-catchment and lake-atmosphere. Most of these models are constrained by short-term monitoring limnological records, traditionally ranging from days to a few decades, potentially limiting the robustness of long-term reconstructions. The integration of lake modeling and paleolimnological records can overcome the short-term monitoring data temporal scale, thereby providing a long-term perspective on lake ecosystem dynamics related to climate variability and human pressures. The present study develops a methodological framework using paleolimnological records from well-dated lake sediment records to constrain, validate and model temporal changes in water quality over a period of 250 years (1850–2100). Lake Geneva (France, Switzerland) was selected as a case study in face of its similarity with other peri-alpine lakes and its representativeness as it is one of the most studied and well-known lentic ecosystems in the world. The 1D hydrodynamic-biogeochemical GLM-AED2 model was applied to simulate dissolved oxygen, nutrients, and chlorophyll-a concentrations along the water column. Pluri-decadal series of limnological data monthly collected by the French Observatoire des LAcs (OLA database) were used to calibrate and validate the model. In addition, model outputs were further validated with published paleolimnological records for the past 170 years. Preliminary results of the calibration procedure show that the GLM-AED2 model accurately predicts the magnitude and seasonal dynamics of the state variables with goodness-of-fit metrics under the literature range (e.g. RMSE = 0.96 mg L–1 and RRMSE = 25% for dissolved oxygen; RMSE = 6.53 ug L–1 and RRMSE = 37% for chlorophyll-a, both in the epilimnion). The integration of a one-dimensional lake model, paleolimnological records, and in situ measurements supports a better understanding of the historical dynamics and provides more robust long-term hindcast/forecast simulations to elucidate the impacts of climate change and critical implications for lake management and planning.
Rayleigh and Love wave tomography from seismic noise of the North African and South Iberian Peninsula lithospheric structure and collision zone
Authors: Neri Alejandra , Badrane Said , Gaite Beatriz , Villaseñor Antonio , Cabieces Roberto , Ranero César R. , Ugalde Arantza
Published: February 2023

With more than 40 years of study, there are still uncertainties about the structure, evolution, and geodynamics of the North African and South Iberian Peninsula lithospheric structure and collision zone. Models of the lithosphere of the region coincide in some anomaly zones, such as the subduction slab under the Gibraltar arc. However, they show discrepancies in the distribution and polarity of the velocity anomalies in the onshore and offshore of most of North Africa.To contribute to the study of the lithospheric structure and to unveil the tectonics in this controversial region, we constructed an ambient noise tomography (ANT) of Love and Rayleigh waves from temporary and permanent broadband stations located in the Iberian Peninsula, North Africa, and Atlantic islands (Madeira, Canarias, Balearic Islands). The methodology employed contemplates phase cross-correlation of 14 months of ambient noise records and the subsequent stacking of the cross-correlograms to obtain the Empirical Green's Function (EGF). To measure the dispersion characteristics of surface wave EGFs present in the ambient noise, we implemented the Frequency-Time Analysis (FTAN). And finally, the inversion of the dispersion measures to get the surface wave tomography.The distribution of the almost 100 broadband stations in North Africa, Portugal, Spain, and the Atlantic islands, results in a broad path coverage in the North African and South Iberian Peninsula lithospheric structure and collision zone, complementing the previous Rayleigh wave velocity models. Furthermore, current studies in this region are Rayleigh-waves based, so the integration of Love waves in this ANT yields new information on the media velocity anisotropy.
Alteration of the Black Carbon pool shortly after a fire under dry conditions at the boreal southern border
Authors: Donnerhack Oliver , Liebmann Patrick , Maurischat Philipp , Guggenberger Georg
Published: February 2023

Fires belong to the most intensive disturbances in ecosystems, but do have different effects on the soil depending on their intensity and fuel materials. Taiga ecosystems contain significant reserves of potentially fire-prone materials, and as temperatures rise in the circumpolar region and precipitation patterns change, an increase in the frequency and intensity of fires is observed. In these fires, incomplete combustion processes result in the formation of black carbon (BC), which is known as a long-term carbon sink due to its chemical properties. As the majority of forest fires are ground fires burning at a rather low intensity in terms of duration and temperature, it is discussed that the BC species formed under these circumstances are chemically less stable than those formed at high temperatures and should therefore only be considered as temporary carbon sinks.
Here we studied the effects of low intensity ground fire shortly after the event and tracked changes in BC within the first four years after the fire event at the southern edge of the boreal forest. We analysed a fire transect running through the two main forest types of this region, focusing on the BC species that we could quantify using the BPCA method. Our results indicate a decline in BC after the fire within the four years of observations, which mainly mainly occurred for the low condensed BPCAs. This finding is independent of the forest typ. Since the precipitation within the experimental period was also negligible and only occurred in very small amounts, we exclude leaching as well as a possible significant aeolian losses, since the trees remained unaffected by the fire and covered the soil against strong wind. We therefore deduce that in situ degradation of the BC must have occurred. Concluding, the general assumption that BC is a stable, long-term carbon sink needs to be questioned more critically. Together with other studies, our results show a quite fast decrease in the concentration of low-condensed BC species in soil over time, indicating a potential for degradation.
The  evidences of deep melting from the  xenolith bearing mafic rocks in Southern Thrace region: The significance of the peridotite and the  pyroxenite source melting.
Authors: Kurkcuoglu Biltan , Yürür Tekin , Günes Berivan , Furman Tanya , Hanan Barry
Published: February 2023

Xenolith bearing mafic rocks with Late Miocene age are widely distributed in southern Thrace region. Primitive mantle - normalised multi-element diagrams of these mafic rocks display OIB signature and specific incompatible element ratios such as Nb/La (1.65-2.05) Nb/U( 37.81 -48.74), Zr/Ba (0.45-0.72) also reveal that mafic rocks were originated  from  the uncontaminated mantle . In adddition, Re content of xenoliths range between 0.09 – 0.44 and similar with fertile mantle values (0.26 ppb) suggested by Morgan (1986), Besides, xenoliths (0.1191-.0.1379) and the host rocks (0.1279-0.1439) have the similar   187Os/188Os isotopic compositions.

The geothermobarometry  calculations (Putirka, 2008) on  cpx and opx  indicate  the average  of 212 km depth  in  xenoliths and   about 32 km depth in host basalts. Furthermore, Gd/Yb ratios range  between 0.97-3.3 in xenoliths and  also range between 3.92-5.24 in basaltic rocks suggest melting  from the  deep source.

The mafic lavas of Thrace region with  high  Tb/Yb(N) values  (2.33 – 3.16) seem to be related with  garnet bearing peridotite  (Tb/Yb(N) >1.8 Wang et al., 2002), besides, high Nb/U, Gd/Yb  ratios,  Re-Os isotopic  compositions, and the melting model  starting from the primitive xenolith (from study region) and pyroxenite source  (Van Nostrand, 2015)  reveal that  mafic lavas  were originated from  the melting of deep mantle  rather than shallow asthenosphere.

 

Morgan, J.W,1986 Journal of of Geophysical Research, 91, 12375–12387

Putirka, K.D 2008, Reviews in Mineralogy and Geochemistry Vol:69, 61-120

Van Nostrand T. S.(2015) Geological Survey report, 191-213

Wang et al.,  (2002), Journal of Geophysical Research Vol:107 No:B1

 

 
A coupled hydrogeological and multi-isotopic approach to investigate saltwater intrusion in a coastal groundwater system (Sardinia, Italy)
Authors: Porru Maria Chiara , Da Pelo Stefania , Arras Claudio , Lobina Francesca , Cidu Rosa , Podda Francesca , Biddau Riccardo
Published: February 2023

Many coastal areas around the world, especially low-lying delta areas, have a high density population and host important economic activities. In such context groundwater abstraction for public water, irrigation and private water supply can lead to over-exploitation and seawater intrusion phenomena. Saltwater intrusion is a critical socio-economic and environmental issue in the coastal plain of Muravera, south-eastern Sardinia (Italy). Since the early fifties the natural hydrodynamic equilibrium between groundwater, surface-water and seawater has been deeply modified by human interventions mainly related to the development of agriculture and tourism activities. The aim of this work is to deepen the knowledge about groundwater recharge areas, salinization mechanisms and water chemistry evolution through a combined hydrogeological and multi-isotopic approach. In this frame, a monthly piezometric and electrical conductivity monitoring survey was carried out for one year, integrated with chemical and isotope analyses of δ18OH2O e δ2HH2O, δ11B, δ18OSO4, δ34SSO4, 87Sr/86Sr. Isotope analyses of δ18OH2O e δ2HH2O from two precipitation samples are also performed to provide a reference for local meteoric composition.Results from hydrochemistry analysis show the occurrence of seawater-freshwater mixing, extending up to 4 km inland. δ18OH2O & δ2HH2O, δ11B, δ18OSO4 & δ34SSO4 isotopes analysis confirms the mixing processes and indicates the meteoric origin of recharge waters for both shallow and semi-confined aquifers. Moreover, a clear correlation between precipitation and seawater H2O isotopic composition is observed. Strontium isotopes ratio has allowed the identification of four main groundwater flow paths, including lateral recharge from bedrock, surface water infiltration from the Flumendosa river and Rio Flumini Uri, and the occurrence of young mixing processes between fresh and sea waters. Outcomes from the combined investigation approach are crucial in the implementation of an integrated and sustainable management system which aims, on the one hand, at slowing the process of saltwater intrusion, and on the other hand to meet socio-economic needs for local communities’ development.
Dendrochronological records of Salix arctica and Salix glauca collected during historical expeditions to Greenland
Authors: Opała-Owczarek Magdalena
Published: February 2023

Arctic dwarf shrub dendrochronology has become the focus of an increasing number of studies since the end of the 20th century. However, an attempt to use Arctic shrub dendrochronology as a tool for climate reconstruction is limited by the age of tundra plants, which rarely exceeds ~100 yrs. To overcome this main limitation, an innovative approach linking contemporary growing tundra species with growth-ring chronologies from specimens collected from historical botanical collections will be used. “Historical” dwarf-shrub specimens had been collected in the field during polar expeditions since the turn of the 18th and 19th centuries (e.g. by Ross’s, Nansen’s and Peary’s Expeditions and later by Greenland Botanical Survey). These materials are now deposited in herbaria collections. Despite the many new research applications of the dry plant material collected in herbaria, historical specimens have never been tested for dendrochronological research. For the preliminary investigation two collections have been selected: The Herbarium at the Royal Botanic Gardens Kew, UK and Herbarium C in the Natural History Museum of Denmark, University of Copenhagen, well known for their Greenland collections. In 2021 and 2022 research on these resources was carried out, consisting in reviewing all materials, the initial selection of sheets in terms of interesting species and areas, photographing, and then final verification and selections of sheets with specimens for invasive sampling. To limit the negative impact of research on collections as much as possible, a rigorous sample selection protocol has been adopted. Preliminary results allowed the construction of dendrochronological scales of arctic willow and greyleaf willow covering the last two centuries. Methodological approaches and perspectives for dendroclimatological reconstructions based on herbarium records are presented.

The research was funded by a Polish National Science Centre project no. UMO-2019/35/D/ST10/03137.
Stability properties of a new anisotropic current sheet equilibrium for planetary magnetotails
Authors: Munoz Patricio A. , Zhou Xiaowei , Büchner Jörg
Published: February 2023

Current sheets are the fundamental structures that store magnetic energy in astrophysical plasmas, such as planetary magnetospheres and solar flares. This free energy can then be explosively released by magnetic reconnection. This process has been traditionally modeled by highly idealized models such as the so-called Harris current sheet equilibrium. But recently, a new class of current sheet equilibrium has been analytically  developed, which takes into account several features of recently observed current sheets in planetary magnetotails. Those features include an embedded multi-layer structure, electron temperature anisotropy and a non-linear magnetic field profile in the (inner) electron inner layer which also includes a normal magnetic field component.Here we present the analysis of the so-far unknown stability properties of this new current sheet equilibrium by means of fully kinetic Particle-in-Cell (PIC) numerical simulations. We used parameters appropriate for the current sheets in diverse planetary magnetotails.Our results allow us to make more realistic predictions concerning the development of magnetic reconnection in those magnetotails compared to the standard Harris current sheet models.
Influence of hydrodynamic and sedimentary processes on tidal wetland landscape evolution for Making Room for Wetlands in the Bay of Fundy
Authors: van Proosdij Danika , Elliott Megan , Lewis Samantha , Graham Jennie , Nichols Kailey , Bowron Tony
Published: February 2023

Managed dyke realignment is increasing being implemented in the Upper Bay of Fundy Canada in response to increased vulnerability of dyke infrastructure to erosion and overtopping.  The Making Room for Wetlands project was initiated in 2017 to develop an evidence-based framework for implementing managed realignment (MR) and tidal wetland restoration in this hypertidal estuary.  MR was conducted at two sites: Converse (near mouth of Missiguash River) and Belcher St. (near head of Cornwallis River) and included both pre and post restoration monitoring of hydrology, soils & sediments, vegetation and morphology.  Earthworks included removal of an aboiteau structure, channel excavation, inner dyke construction and levelling of old dyke infrastructure.  Detailed hydrodynamics, sediment transport and deposition data were collected seasonally at the Converse site since first tidal waters were introduced in Dec 2018.  Ecomorphodynamic changes were quantified using repeat high resolution RPAS surveys, field measurements and RSET stations at both sites.  The rate of evolution of tidal wetland landscape differed between the two sites.  High sedimentation rates (~10 cm/yr) associated with the turbidity maximum at Belcher provided a disturbance surface rapidly colonized by annual halophytes and was fully vegetated by Year 3 with a mix of tidal brackish species (equivalent to reference site).   Sedimentation also played a role at Converse, filling in the borrow pit used to construct the inner dyke within the first two years, facilitating the development of a shallow tidal creek network.  Additional sedimentation over the former agricultural surface aided in slower development of a hybrid creek network incorporating the relict ditches.  Large spring tides play an important role in sediment supply to the marsh platform.  Positive sediment flux values into the site were recorded in association with erosion of the inlet channel which typically occurred during higher spring tide events.  A preliminary model linking sediment flux at the inlet with deposition on the marsh surface was developed.  While some halophytic vegetation was established within the first two years at Converse, vegetation established increased markedly in Year 4.   Erosion of the tidal inlet during high spring tides provided important subsidies of sediment in addition to baseline concentrations within tidal waters to the marsh platform that facilitated the evolution of the tidal wetland landscape.  While the establishment of tidal marsh vegetation was slower at Converse than Belcher both are providing ecosystem services.  Implications for modelling the trajectory of tidal wetlands after managed realignment including MR design, timing of earthworks and position within the estuary are discussed.   
Root soil Nitrogen acquisition by mature Oak trees exposed to elevated CO2: Nitrogen preference and uptake rate under a future climate
Authors: Pihlblad Johanna , Hamilton R. Liz , Rumeau Manon , Sayer Emma J. , Hartley Iain P. , Ullah Sami
Published: February 2023

In a future CO2 rich world, nitrogen (N) limitation is projected to decrease the CO2 fertilization effect limiting the ability of temperate forests to mitigate climate change. There are limited direct measurements of roots showing if mature trees are able to increase their N uptake in a future climate. Additionally, it is not currently understood if roots of mature trees can change their N form preference under elevated CO2 to maintain or enhance their N uptake. These are all gaps in knowledge identified as adding uncertainty to modelling efforts assessing ecosystem response to climate change. We quantified the rate of N uptake of living mature oak tree roots (Quercus robur) and their preference of N forms. On two occasions (July and November 2022) we carefully excavated live oak roots of three mature trees in each of the six experimental Free Air Carbon Enrichment (FACE) arrays (three ambient and three +150 ppm CO2) at the BIFoR FACE facility located in Staffordshire (United Kingdom). The live roots were cleaned and pre-incubated in acid washed sand and a nutrient solution for 24 hours to establish an acclimatized baseline condition following excavation. The roots were then exposed to a mix of inorganic and organic N forms where only one form was labelled in each treatment (15N-nitrate, 15N-ammonium, a mix of 20 15N labelled amino acids and an unlabelled control) to elucidate N preferences and rate of uptake during a two-hour incubation period. By analysing the root tissue for 15N our findings will investigate the preferences and uptake rates of N by mature trees under elevated CO2. We hope to shed light on these mechanisms mediating N uptake of mature trees to explain how mature forest stands respond to climate change in a temperate climate.    
Variability of Fallout Radionuclides in River Channels: Implications for Sediment Residence Time Estimations
Authors: Munoz-Arcos Enrique , Millward Geoffrey , Clason Caroline , Bravo-Linares Claudio , Blake William
Published: February 2023

Fine sediment plays an important role in the healthy functioning of river ecosystems providing nutrients and contributing to habitat functioning. However, excessive sediment supply into rivers has several detrimental impacts on water quality and it causes sedimentation in river channels, reservoirs and estuaries. In addition, silts and clays are geochemically active and consequently are responsible for the transport of contaminants, including trace metals, phosphorus, pesticides and radionuclides among others which have high sorptive affinity for fine-grained particles. Hence, quantifying the timescales of sediment transfer throughout a river system is critical for understanding river basin sediment dynamics and the fate of their associated pollutants.Fallout radionuclides (7Be, 210Pbex and 137Cs) have been used to assess sediment travel distances, sediment age and sediment residence times in a variety of landscapes. An advantage of using these radionuclides as sediment chronometers is their half-lives which can be used to model sediment residence time from days to decades in different catchment compartments.The River Avon (Devon, UK) is a 40 km long gravel-bed river, draining rough moorland and with a catchment area of 110 km2. The mean annual flow is 3.7 m3 s-1 and is moderated by managed discharges from a reservoir upstream. Suspended and channel bed sediments were sampled in a 5 km section of the river during four seasonal surveys (January, March, July and November 2022) and suspended sediments during a stormflow event were also sampled.Radionuclide activity concentrations of channel deposited sediments varied substantially within and between river bars and seasonally. Suspended sediment activity concentrations varied within the stormflow hydrograph and seasonally. Relationships between radionuclide activity concentrations and sediment storage, particle size, total organic carbon and C:N ratios were also evaluated. Channel sediment residence times obtained using 7Be/210Pbex activity ratios ranged between 0 to 110 days, reproducing the high variability found in activity concentrations. Future research will assess the influence of sediment sources on 7Be/210Pbex ratios and the relationship between sediment storage dynamics and sediment-bound contaminants. Sediment residence time modelling will allow an improved understanding of sediment dynamics in gravel-bed rivers which is essential to inform management decisions and prediction of the timescales of transfer and fate of associated contaminants.
Evaluation of the MONARCH-simulated NO2 tropospheric columns against Sentinel-5P TROPOMI observations over the Iberian Peninsula
Authors: Lopez Franco , Petetin Hervé , Jorba Oriol
Published: February 2023

Despite a relatively simple chemistry, nitrogen dioxide (NO2) remains challenging to reproduce accurately in current air quality models, notably due to persistent uncertainties affecting the representation of its anthropogenic and natural emission sources. Another reason for these uncertainties lies is the lack of surface in-situ observations in many rural areas where nitrogen oxides (NOX) are yet playing a strong role in ozone formation.In this study, we take benefit from the TROPOMI NO2 tropospheric columns (TrC-NO2) observations complemented by surface NO2 observations to comprehensively evaluate the MONARCH chemical weather model. We focus our analysis over the Iberian Peninsula during the year 2019. MONARCH reproduces relatively well the spatial variability of TrC-NO2 observed by TROPOMI, although with a negative bias. A lack of NOx emission in rural areas over the Iberian Peninsula is strongly suggested by the results. In order to investigate more deeply the corresponding underestimation of rural NOx, different sensitivity analyses are performed, notably on anthropogenic NOX and natural soil nitric oxide (NO) emissions. The sensitivity analysis showed a spatially and seasonally dependent response of the emissions used as inputs in MONARCH on the modeled TrC-NO2. The combined evaluation on surface and TrC NO2 provide some interesting insights on the vertical distribution and its representation in MONARCH.This study thus illustrates the strong interest of such satellite-based observations to complement surface monitoring stations, especially in areas such as croplands where almost no surface observations are available.
Monitoring of elastic properties using DAS and DTS in a controlled experiment during road construction
Authors: Krawczyk CharLotte M. , Lipus Martin P. , Hart Johannes , Wollin Christopher , Cunow Christian , Jousset Philippe
Published: February 2023

Maintenance of infrastructure is costly and difficult to implement systematically when it spreads over wide areas, such as road or pipeline networks. In the monitoring of road ways, conventional methods to control the road integrity rely on discrete measurements in space and time. There is a large demand for innovative technologies that are able to assess the structural integrity as a whole and in regular intervals or even continuously. Distributed fiber-optic sensing opens the opportunity to measure numerous physical quantities such as temperature and strain with high spatial and temporal resolution over tens of kilometers. In addition, it is easily deployable at reasonable cost.In order to address the issue of asphalt aging due to exposure to heavy traffic loads, we installed a fiber-optic cable into a reworked road interval and recorded fiber-optic data in a controlled experiment with numerous test vehicles of different sizes and weights. The recorded data suggests that elastic properties of the asphalt can be retrieved from the bypassing traffic. Vehicles can be characterized by the number of axes and load on the asphalt composite. In the next phase, we will monitor the aging of the test field to deduce how varying matrial properties can be better identified for geotechnical and geoscience applications.