bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of water on brittle creep of Indiana limestone
Authors: Pluymakers Anne , Allen Michael , Bedford John , Faulkner Daniel
Published: March 2022

The effect of water on time-dependent deformation (creep) behaviour in intact limestone is not yet fully understood. Using a triaxial deformation apparatus, we investigated creep of an allochemical limestone (Indiana) using three different pore fluid chemistries: standard demineralized water, a saturated CaCO3 solution and Argon gas (i.e. in the absence of water). Room temperature experiments are performed at 10 MPa effective confining pressure and a pore fluid pressure of 20 MPa. For each pore fluid type, a reference triaxial test was performed at 10 MPa effective confining pressure, using a constant strain rate of 10-5 s-1,to ascertain the failure stress for samples with this porosity under these conditions. To investigate the stress-dependence of creep, samples of a narrow porosity band are loaded to 75, 80 or 90% of the failure stress, after which the stress is held constant and we monitor the subsequent time-dependent deformation. We use a combination of axial and volumetric strain measurements and acoustic monitoring. The porosities of our sample sets were chosen to enable comparison between the strain rates obtained of samples loaded to different stresses for each pore fluid type, where the porosities were 16.25 +/- 0.15 %, 17.25 +/- 0.05%, and 16.6 +/- 0.15 % for demineralized water, CaCO3-saturated solution and Argon respectively.

 

Our initial results indicate that creep rates of samples saturated with demineralized water and saturated CaCO3 solution are 10-7 – 10-9 s-1. Creep rate depends exponentially on stress, with an exponent of ~8.2 for demineralized water and ~9.6 for CaCO3 saturated solution. Such high exponents are generally associated with brittle creep processes, though using a microstructural model for pressure solution indicates that solution transfer processes will lead to creep rates of 10-3-10-11 s-1 under these conditions for grain sizes between 0.1 and 100µm, which is roughly the range of grain sizes present in Indiana limestone. An initial experiment with Argon shows a decrease of ~ 1 order magnitude in creep rate compared to an experiment with water at a similar stress. Our preliminary results imply that Indiana limestone deforms via a combination of fluid-assisted solution-transfer and brittle creep processes, however more Argon experiments and microstructural analyses are required to confirm the rate-controlling deformation mechanisms.
Multiples suppression scheme of waterborne GPR data
Authors: Zhao Yonghui , Shen Ruiqing , Cheng Hui
Published: March 2022

Ground penetrating radar (GPR) is a geophysical method that uses high frequency electromagnetic waves to detect underground or internal structures of objects. It has been widely used in the Geo-engineering and environment detection. In recent years, GPR has played an increasingly important role in shallow underwater structure survey due to its advantages of economy, high efficiency and high accuracy. However, due to the strong reflection coefficients of water surface and bottom for electromagnetic waves, there are multiples in the GPR profile acquired in waters, which will reduce the signal-to-noise ratio of the data and even lead to false imaging, finally seriously affect the reliability of the interpretation result. With the increasing requirement of high-precise GPR detection in waters, multiple suppression has become an essential issue in expanding the application fields of GPR. In order to suppress multiple waves in waterborne GPR profile, a novel multiple wave suppression method based on the combination scheme of the predictive deconvolution and free surface multiple wave suppression (SRME). Based on the validity test of one-dimensional data, the adaptive optimizations of these two methods are carried out according to the characteristics of GPR data in waters. First, the prediction step of predictive deconvolution can be determined by picking up the bottom reflection signal. Second, the water layer information provided by the bottom reflection is used in continuation from the surface to the bottom to suppress the internal multiples. The numerical model and real data test results show that each single method can suppress most of the multiples of the bottom interface and the combination strategy can further remove the additional residues. The research provides a basis for the precise interpretation of GPR data in hydro-detection.
Modes of Lorenz atmospheric energetics under different CMIP6 climate scenarios
Authors: Michaelides Silas
Published: March 2022

This aim of this study is to examine whether different climate scenarios, as they are adopted in Phase 6 of the Coupled Model Intercomparison Project (CMIP6), lead to different modes of the energetics components of the Lorenz’s energy cycle which would therefore have an impact on the “rate of working” of the climate system. In particular, the study focuses on four energy forms, namely the Zonal and Eddy components of both the Available Potential and Kinetic Energies, the permissible conversions between these forms of energy, the diabatic generation of Available Potential Energy as well as the dissipation of the Kinetic Energy.

The CMIP6 climate projections in the 85-year period from 2015 to 2100 produced by the HadGEM3-GC3.1 model have been used. These projections are driven by a set of Shared Socioeconomic Pathways (SSP’s) based on new future pathways of societal development but also incorporating the previously used Representative Concentration Pathways (RCPs). In this respect, the following three concentration-driven scenarios under Tier 1 of ScenarioMIP are used:

ssp126: Α scenario with low radiative forcing by the end of the century, following the RCP2.6 global forcing with SSP1 socioeconomic conditions; radiative forcing reaches a level of 2.6 W/m2 in 2100;

ssp245: Α scenario with medium radiative forcing by the end of the century, following the RCP4.5 global forcing with SSP2 socioeconomic conditions; radiative forcing reaches a level of 4.5 W/m2 in 2100;

ssp585: Α scenario with high radiative forcing by the end of century, following the RCP8.5 global forcing with SSP5 socioeconomic conditions.

For comparative purposes, the corresponding historical 85-year dataset, preceding the time period covered by the climatic projections has been used. In this respect, data from the same cohort in the period 2029 to 2014 form also part of this study.

The energy balance and time series of the energetics components under different SSP-based scenarios show that different scenarios yield diverse energetics regimes, consequently impacting the Lorenz’s energy cycle and its underlying physical processes.
Evaluation of the root system and phyto-management potential of Sesbania cannabina grown in hexavalent chromium contaminated soils utilizing modified rhizobox systems.
Authors: Ibne Kamal Abdul Kadir , Batty Lesley , Bartlett Rebecca
Published: March 2022

This study aimed to assess how the root system of Sesbania cannabina behaves under various concentrations of Cr (VI) and whether it could be a suitable species for the phyto-management of Cr (VI) contaminated soils. The experiment was conducted in rhizoboxes under greenhouse conditions using a sandy loam soil dosed with potassium dichromate giving eight different Cr (VI) concentrations (0 ppm, 5 ppm, 10 ppm, 20 ppm, 40 ppm, 80 ppm, 160 ppm, and 360 ppm). Plant roots were photographed with a Canon 60D (18-megapixel) camera with a 50 mm prime lens and analysed with Image J image processing software.

At 360 ppm concentration, seeds of S. cannabina germinated but were unable to grow further. However, under concentrations of 0-80ppm there was no significant change observed in the root growth (Length) . At 160 ppm root growth was reduced by about 55±0.65% at 25 days and 35±0.25 % at 60 days compared to plants grown at 0 ppm. After 60 days no chromium (VI) was detected in the soil for (0 to 160 ppm) in comparison with the control (with no plants) where no changes in Cr (VI) were observed.

 

The absence of Cr (VI) in soil after 60 days suggests that S. cannabina can be considered as a candidate for phyto-management of soils containing up to 160 ppm Cr (VI).
Data assimilation of soil moisture measurements in land surface simulations to study the impact on evapotranspiration estimates in European forests
Authors: Strebel Lukas , Bogena Heye , Vereecken Harry , Hendricks Franssen Harrie-Jan
Published: March 2022

Land surface models are important tools to improve our understanding of interacting ecosystem processes and for the prediction of future risks of droughts and fires. However, such predictions are associated with uncertainties related to model forcings, parameters and process simplifications. Therefore, the increasing availability of high-quality observations should be used to improve the accuracy of land surface model predictions. In this study, we use the Ensemble Kalman Filter for the fusion of in-situ soil moisture observations from different observation networks across Europe (e.g. eLTER, FLUXNET, TERENO, ICOS) into the Community Land Model 5.0 (CLM5). The sites selected for this study cover different regional climate zones and forest types and feature in-situ soil moisture as well as evapotranspiration observations from eddy covariance towers for the period from 2009 to 2019. In this study, we specifically focus on European forested study sites where both in-situ soil moisture and evapotranspiration observations are available for the period from 2009 to 2019. CLM5 simulates a broad variety of important land surface processes including water and energy partitioning, surface runoff, subsurface runoff, photosynthesis and carbon and nitrogen storage in vegetation and soil. Here, we focus on improving the accuracy of model predictions by updating soil moisture dynamics and related soil hydraulic parameters by coupling CLM5 to the Parallel Data Assimilation Framework (PDAF) to assimilate soil moisture data into CLM5 during simulation runtime. Additionally, we implemented a new and more direct approach to update the hydraulic parameters compared to previous versions of the CLM5-PDAF coupling and show the effects of this implementation.We demonstrate the value and limitation of assimilating soil moisture data for simulating evapotranspiration focusing on recent drought events in 2018 and 2019. We found that soil moisture dynamics were better characterized by data assimilation, but this did not result in improved estimation of evapotranspiration for the different sites during both wet and dry periods.
Sea level response to Quaternary erosion and deposition in Scandinavia
Authors: Pallisgaard-Olesen Gustav , Pedersen Vivi Kathrine , Gomez Natalya , Mitrovica Jerry X.
Published: March 2022

The landscape in western Scandinavia has undergone dramatic changes through numerous glaciations during the Quaternary. These changes in topography and in the volumes of offshore sediment deposition, have caused significant isostatic adjustments and local sea-level changes, owning to erosional unloading and de- positional loading of the lithosphere. This geomorphic mass redistribution also has the potential to perturb the geoid, resulting in additional sea-level changes. However, the combined sea-level response from these processes is yet to be investigated in detail for Scandinavia.

In this study we estimate the total sea-level change from i) late Pliocene- Quaternary onshore bedrock erosion and erosion of sediments on the coastal shelf and ii) the subsequent deposition in the Norwegian Sea, northern North Sea and the Danish region. We use a gravitationally self-consistent global sea- level model that includes the full viscoelastic response of the solid Earth to surface loading and unloading. In addition to total late Pliocene-Quaternary geomorphic mass redistribution, we also estimate transient sea-level changes related specifically to the two latest glacial cycles.

We utilize existing observations of offshore sediment thicknesses of glacial origin, and combine these with estimates of onshore glacial erosion and of erosion on the inner shelf. Based on these estimates, we define mass redistribution and construct a preglacial landscape setting as well as approximate a geomorphic history of the last two glacial cycles.

Our results show that erosion and deposition has caused a sea-level fall of ∼50-100 m along the southern coast of Norway during the last two glacial cycles reaching ∼120 m in the offshore Skagerak region. The total relative sea-level fall during the Quaternary reach as much as ∼350 m in Skagerak. This highlights the importance of accounting for geomorphic sediment redistribution in glacial isostatic-adjustment modelling when interpreting ice sheet histories and glacial rebound.
Study on tight sandstone gas accumulation process in transition zone of basin-margin: A case study of Duguijiahan block, Hangjinqi area, northern Ordos Basin, China
Authors: Yu Hanwen
Published: March 2022

Hangjinqi area is located in the northern margin of Ordos Basin in north China, the main body of which is on the inherited palaeo-uplift, and has been considered as a favorable oil-gas accumulation direction area. Duguijiahan block structurally located in the middle of Hangjinqi area, in the fault transition zone of Boerjianghaizi fault and Wulanjilinmiao fault, which is a transition area from quasi-continuous gas reservoir to continuous gas reservoir. By analyzing the reservoir characteristics and evolution process of tight sandstone gas reservoirs, the thermal maturation history of source rocks and the history of natural gas charging in Lower Shihezi Formation, this paper studies the natural gas accumulation process in the transition zone between quasi-continuous and continuous gas reservoirs, hoping to contribute to tight gas exploration in Ordos Basin and other basins with similar tectonic backgrounds in the world. The results show that the initial porosity of the Lower Shihezi Formation in Duguijiahan block is about 32~36%, and experienced the porosity decreasing of compaction (avg. = 18.58%) and cementation (avg. = 11.03%), and porosity increasing of dissolution (avg. = 1.24%). The sandstone densification (porosity <10%) occurred in the mid-late Jurassic (~170–150 Ma). Due to tectonic uplift from the end of the Early Cretaceous to the present day, the present porosity has basically inherited the characteristics of the end of the Early Cretaceous, and the average porosity is only 8.4%. On the other hand, based on the homogenization temperature test of fluid inclusions, laser Raman spectroscopy analysis of gas inclusions and basin simulation, the hydrocarbon charging time of the Lower Shihezi Formation gas reservoir in Duguijiahan block is early Cretaceous (~145-100Ma), indicating that the gas charging time of the gas reservoir in the study area is later than the reservoir densification time. Furthermore, the natural gas charging time in the study area is characterized by gradual charging from south to north, indicating that the early natural gas charging is mainly affected by the maturity of underlying source rocks. From the end of early Cretaceous to now, it is the adjustment period of natural gas accumulation in the study area. The continuous tectonic uplift leads to the decrease of geothermal temperature, the loss of reservoir pressure and the formation of fractures. The natural gas charged in the early stage gradually migrates and accumulates along the northern up-dip direction of the fracture zone. The Lower Shihezi Formation was pinched out in the northern Gongkahan uplift to form effective blocking. The migration process of natural gas has been confirmed by the present exploration findings, the relationship between porosity and permeability of reservoir physical properties and the difference of natural gas components in the north and south.
Deep learning cluster techniques for large aerosol datasets 
Authors: Topping David , Crawford Ian , Gallagher Martin , Moss Maxamillian , Chan Man Nin , Lee Hing Bun martin , Xing Sinan , Ng Tsin Hung , Tai Amos
Published: March 2022

The impacts that aerosol particles have on the climate, air-quality and thus human health, are linked to their evolving chemical and physical characteristics. We know that many processes taking place in/on atmospheric aerosol particles are accompanied by changes in the particles’ morphology (size and shape). Likewise, particles of primary origin [e.g. desert dust, volcanic ash, soot, pollen] can have widely varying morphological features that should nonetheless offer significant information to aid detection and classification. There have been a number of developments in instrument capability that capture spectral signatures and images of individual particles. This includes the development of instruments designed to identify biological particles through a combination of fluorescent profiles, fluorescence lifetime decay and scattering images. Whilst the development of experimental frameworks continue, the marriage of developing compact systems and associated data analytics is lacking. There has been a rapid proliferation of data science methodologies, now wrapped up in commonly accessible open source environments. However, the tuning of appropriate hyperparameters, and the choice of architecture can be difficult. Likewise, where the challenge is to include multivariate datasets into one routine, such as chemical signatures and scattering information, it is difficult to know how best to combine them.  

In this presentation we present an evaluation of an approach that uses a combination of convolutional neural network autoencoders to 1) lead to cluster strategies for long term ambient datasets, no matter the size and 2) combines sell-supervised learning with small amounts of laboratory data to arrive at classification routines. In each case the architecture is automatically tuned using a hyperband approach and various data augmentation strategies are applied. The initial focus is on data derived from the PLAIR Rapid-E instrument , though developments are applicable to a number of measurement techniques.  
The Emirates eXploration Imager (EXI) onboard the Emirates Mars Mission (EMM): Overview of In-flight Performance, and Water Ice Cloud Retrievals
Authors: Wolff Michael , Jones Andrew R. , Osterloo Mikki , Shuping Ralph , Edwards Christopher , Al Shamsi Mariam , Espejo Joey , Fisher Charles , Jeppesen Chris , Knavel Justin
Published: March 2022

The EXI instrument is a camera onboard the EMM spacecraft, with a field a view capable capturing the full disk of Mars throughout its nominal science orbit.   Though the use of its multiple band passes (220, 260, 320, 437, 546, 635 nm) and the effective spatial resolution (2–4 km per native pixel), EXI’s primary goal is to provide both regional and global imaging of the Martian atmosphere with diurnal sampling over much of the planet on a time scale of approximately 10 days.  This presentation will provide an overview of EXI’s on-orbit instrument performance, a brief description of the observation strategy employed with the start of Science Operations (23-May-2021, Ls=49°), and the retrieval results of the ice optical depth and their diurnal behavior for the period of mid-spring through late-summer in the northern hemisphere.  More specifically, the presentation will cover:

 

Status of the instrument calibration and plans for on-going on-orbit monitoring of instrument performance, including radiometric errors. Plus, some guidance on interpreting the metadata of the EXI publicly released raw and calibrated images;

 

Illustration of the various disk geometries sampled during an EMM orbit of Mars, and how such observations are combined to provide diurnal coverage of the illuminated portion of the disk/atmosphere;

 

Overview of the ice optical depth retrieval algorithm, and its application to the data obtained since the start Science Operations with an emphasis on the behavior of the aphelion cloud belt; including the formation and decay phases.
Investigating the evolution of tropical cirrus clouds from deep convection
Authors: Horner George , Gryspeerdt Edward
Published: March 2022

Tropical convective clouds, particularly their large cirrus outflows, play an important role in modulating the energy balance of the Earth’s atmosphere. Understanding the evolution of these clouds, and how they change in response to anthropogenic emissions is therefore important to understand past and future climate change. Previous work has focused on tracking individual convective cores and their evolution into anvil cirrus and subsequent thin cirrus clouds in satellite data.

In this work we have introduced a novel approach to investigating the evolution of tropical convective clouds by creating a ‘Time Since Convection’ (TSC) dataset. Using reanalysis windspeeds, the time since the air at each location last experienced a convective event (as defined by the presence of a deep convective core) is calculated. Used in conjunction with data from the DARDAR and CERES products, we can build a composite picture of the radiative and microphysical properties of the clouds as a function of their time since convection.

As with previous studies, we find that cloud properties are a strong function of time since convection, with decreases in the optical thickness, cloud top height, and cloud fraction over time. These changes in in cloud properties also have a significant radiative impacts, with the longwave and shortwave component of the cloud radiative effect also being a strong function of time since convection. In addition, using the DARDAR product, a combination of CloudSat radar and the CALIPSO lidar measurements, we build composite cross sections of convective clouds, characterising their vertical evolution and how it is influenced by external meteorological and initial conditions flagged in the TSC dataset.
What we can learn about transboundary aquifers from geochemical signatures of springs
Authors: Koit Oliver , Retike Inga , Terasmaa Jaanus , Bikše Jānis , Lode Elve , Vainu Marko , Popovs Konrāds , Babre Alise , Abreldaal Pamela , Sisask Karin , Tarros Siim , Marandi Andres , Hunt Marlen , Männik Magdaleena , Polikarpus Maile
Published: March 2022

As groundwater does not follow human-drawn boundaries such as country borders, groundwater pollution in one country can adversely affect groundwater quality and availability in a neighboring country. It is vital to develop a conceptual understanding of shared groundwater resources not only to ensure their protection, but also to avoid future conflicts, especially in a changing climate. Both the Water Convention and EU Water Framework Directive emphasize the need for joint assessment and management of transboundary groundwater resources (commonly referred to as “transboundary aquifers” or “groundwater bodies''), and it is crucial to establish a representative transboundary groundwater monitoring network to gather the necessary data. Often, the coverage of monitoring points in the existing groundwater monitoring networks is scarce in the peripheral areas and the installation of new wells would be economically unreasonable. Springs are natural groundwater outflows that can fill gaps in monitoring networks. Monitoring springs can be cost-effective, make water sampling easier, moreover, their water can provide information on a significantly larger catchment area than monitoring wells. The spring site cannot be selected like monitoring wells, so selecting the best springs requires a thorough preliminary assessment. A good conceptual understanding of the recharge area is a prerequisite for the selection of suitable monitoring springs. In this study, 46 springs in the transboundary area of Estonia and Latvia (NE Europe) were screened in 2021-2022 for a variety of geochemical parameters (field parameters, major ions, biogenic and trace elements, water stable isotopes). Some springs were sampled more than once to assess seasonal variability. Then springs were clustered based on their geochemical characteristics using multivariate statistics. This study is the first step in the procedure established on how to select representative springs for transboundary aquifer monitoring.

This study is financed by the Interreg Estonia-Latvia cooperation program project “WaterAct”, the EEA and Norway Grants Fund for Regional Cooperation project “EU-WATERRES”, and by performance-based funding of University of Latvia Nr.AAP2016/B041 within the “Climate change and sustainable use of natural resources” program.
Evidence of abiotic graphite formation in Proterozoic marbles of the Lewisian Complex: mechanisms and consequences for the deep carbon cycle
Authors: Schito Andrea , Parnell John , Muirhead David , Boyce Adrian
Published: March 2022

The role of subduction zones has been considered critical to understand carbon fluxes among the Earth’s reservoirs. At plate margins, most of the carbon is stored in carbonate sediments. Nevertheless, the past decade saw an increasing focus also on reduced carbon - kerogen and graphite – to understand its role in the deep carbon cycle. Most of reduced carbon derive from seafloor organic-rich sediments, even if, a little portion can form by decarbonation during metamorphism.

In the Palaeoproterozoic supracrustal rocks of the Lewisian Complex, graphitic marbles were found in a mixed succession of metasediments at Gott Bay, Island of Tiree (Scotland). Such marbles show bedding-parallel slip surfaces associated with chlorite that are absent in other marbles on the island that are devoid of graphite. Marbles and schists-hosted graphite were analysed showing marked differences in carbon isotopic composition and structural ordering measured by means of Raman spectroscopy.

Petrographic and chemical evidence support the hypothesis of an abiotic origin of the marble-hosted graphite and the mechanisms that led to its formation could explain the heavy isotopic composition of many Proterozoic marbles in the world.

 

 

 

 
Climate change or just new software? The impact of Extrap software on ADCP discharge measurements in Norway
Authors: Florvaag-Dybvik Kristoffer
Published: March 2022

Acoustic Doppler Current Profilers (ADCP) are used a lot all around the world to measure discharge in rivers. These instruments measure most of the vertical velocity profile in rivers, but due to technical and physical limitations they cannot measure all the way to the surface or all the way to the bottom. To calculate discharge, the instruments (or software) need to extrapolate data into the un-measured regions. Previously there was no good and available tools to aid the operators in selecting proper extrapolation. In 2010 USGS released the software Extrap, which plots relative velocity versus relative depth for ADCP measurements, and this tool made it way easier to determine the correct extrapolation of data. (Extrap is now a part of Qrev/QrevInt). Before the introduction of Extrap, 80-90% of the ADCP-measurements at NVE used the default power law extrapolation in the ADCP’s standard software (WinRiver at the time), and around 5% used constant at top and no-slip at the bottom. The first if these assumes a velocity profile that is very similar to the logarithmic velocity profile that comes from classical boundary layer theory. The latter one is much steeper (constant) close to the surface.

After starting to use Extrap regularly, 60% of the measurements use the constant/no-slip extrapolation, while 40 % uses the power law extrapolation. This impacts the reported discharge from the measurements by reducing the reported discharge by on average 4% for the measurements using constant/no-slip extrapolation, and data users must be aware, because these measurements eventually form the foundation for the long time, continuous data series for discharge in our archives.

How will a climate researcher react to a 4% decrease in annual run-off from Norway?
Faulting and crater development controlled by pre-existing topography - evidence from drone and satellite observations during the 2021 Cumbre Vieja eruption
Authors: Walter Thomas R. , Zorn Edgar , Gonzalez Pablo J. , Plank Simon , Villacreses Valeria Munoz , Shevchenko Alina , Richter Nicole , Malebran Carla Valenzuela
Published: March 2022

Volcanic terrains host complex and commonly steep morphologies and are often also subject to tensile and shear faulting episodes. Previous studies demonstrated that strike slip and dip slip faults deflect at topographic highs and may locally diverge to develop multiple fault branches with varying strike and dip directions. Although fault deflection is associated with dike-related faults, a direct link to the positioning of eruption craters could not be established yet. Here we show that the Cumbre Vieja eruptions occurred in a complex pre-existing topographic and structural environment that affected fault development and evolution of eruption vents. 

We investigate available satellite radar data from the CosmoSkymed and TerraSAR-X missions, to track the temporal and spatial evolution of summit craters and faults. We find that summit craters are closely aligned in a direction NW-SE and developing a nested structure. We also conducted repeat drone measurements to acquire close-range optical images of the summit and nearby flanks. Results allow an in-depth analysis of the morphology of craters and the geometry, traces and throws of faults. We find that in late stages of the eruption important tensile faults evolve, and deflect at pre-existing topographic highs. We further find that these faults are developing complex sinkholes and secondary features due to their burial by loose unconsolidated material (i.e. tephra), and that the faults converge again at topographic lows, with varying degrees of the slip or dilation tendency. We discuss the coalignment of these structures with crater alignments, and present results from analogue models aiming to better constrain the varying deflection of faults controlled by topography.
An integrated geophysical approach for imaging of the Semail ophiolite
Authors: Pilia Simone , Ali Mohammed , Searle Mike , Watts Anthony , Keats Brook , Ambrose Tyler
Published: March 2022

The Semail ophiolite, a thick thrust sheet of Late Cretaceous oceanic crust and upper mantle, was obducted onto the previously rifted Arabian continental margin in the Late Cretaceous, and now forms part of the United Arab Emirates (UAE)-Oman mountain belt. A deep foreland basin along the west and SW margin of the mountains developed during the obduction process, as a result of flexure due to loading of the ophiolite and underlying thrust sheets. Structural and compositional complexities (e.g., presence of thick sand dunes, relatively shallow high-velocity and dense ophiolite structure) have made geophysical imaging of the sub-ophiolite and mid-lower crustal structure particularly challenging.

A combination of active and passive-source seismic techniques, potential field modelling and surface geological mapping are used to constrain the stratigraphy, velocity structure and crustal thickness beneath the UAE-Oman mountains and its bounding basins. Depth-migrated multichannel seismic-reflection profile data are integrated in the modeling of traveltimes from long offset reflections and refractions, which are used to resolve the crustal thickness and velocity structure along two E-W onshore/offshore transects in the UAE. Additionally, we apply receiver function and virtual deep seismic sounding methods to distant earthquake data recorded along the two transects to image crustal thickness variations. Seismic and geological constraints from the transects have been finally used to model gravity and magnetic anomaly data along two coincident profiles.

Geophysical methods define the Semail ophiolite as a high-velocity, high density, > 15 km thick body dipping to the east. The western limit of the ophiolite is defined onshore by the Semail thrust while the eastern limit extends several km offshore, where it is defined seismically by a ~40–45° normal fault. Emplacement of the ophiolite has probably flexed down a previously rifted continental margin, thus contributing to subsidence of flanking sedimentary basins. The new crustal thickness model presented in this work provides evidence that a crustal root is present beneath the Semail ophiolite, suggesting that folding and thrusting during the obduction process may have thickened the pre-existing crust by 16 km.
Using atmospheric variability to understand the wintertime regional warming and cooling patterns in the North Atlantic Sector
Authors: Tao Dandan , Madonna Erica , Li Camille
Published: March 2022

The 20th century “early warming” (1910-1940) and cooling (1940-1970) of the Northern Hemisphere offer an interesting contrast of periods with opposite temperature trends, similar hemispheric temperature anomalies, yet very different temperature anomaly patterns. These contrasts are particularly clear in the North Atlantic sector, which exhibits large climate variability over a range of time scales, from short (weather regimes) to long (Atlantic Multidecadal Variability). In this study, we explore the role of the atmospheric circulation (North Atlantic jet stream) in determining the temperature anomaly patterns over the 20th century. While different jet configurations are associated with distinct synoptic temperature patterns in the North Atlantic sector, only some are found to contribute substantially to longer term temperature trends. Notably, the southern jet configuration has the strongest temperature anomalies, with a dipole signal that is opposite from the one under the tilted jet configuration. At the same time, these two jet configurations exhibit relatively large decadal variations in frequency (days of occurrence in given winter seasons), with trends that are almost the opposite. In fact, changes in the frequency of southern and tilted jet “days” alone account for much of the North Atlantic and Arctic temperature variability on decadal time scales, including the differences between the early warming and cooling periods (e.g., the flipped warming versus cooling patterns are associated with fewer southern jet days and more tilted jet days). However, the reconstruction skill of the 30-year mean temperature anomaly in the North Atlantic sector using jet frequency exhibits decadal variability, with high skill scores interestingly coinciding with the positive phases of the Atlantic Multidecadal Variability. The lower reconstruction skill especially during the global warming period from the1980s onwards is likely due to the impact from the warming hole in the North Atlantic, which dominates the temperature patterns in the North Atlantic. Overall, the evolution of Northern Hemisphere surface temperature over the 20th century is found to be influenced by North Atlantic jet variability, with lower frequency ocean effects contributing more in recent decades.
Metric-Decametric Gyrosynchrotron Radio Emission From the Quiet Solar Corona
Authors: Kozarev Kamen , Zhang Peijin , Zucca Pietro
Published: March 2022

The radio emission of the quiet Sun in the metric and decametric bands has not been well studied historically due to limitations of existing instruments. It is nominally dominated by thermal brehmsstrahlung of the solar corona, but may also include significant gyrosynchrotron emission, usually assumed to be weak under quiet conditions. In this work, we investigate the expected gyrosynchrotron contribution to solar radio emission in the lowest radio frequencies observable by ground instruments, for different regions of the low and middle corona. We approximate the coronal conditions by a synoptic magnetohydrodynamic (MHD) model. The thermal emission is estimated from a forward model based on the simulated corona. We calculate the expected gyrosynchrotron emission with the Fast Gyrosynchrotron Codes framework by Fleishman and Kuznetsov (2010). The model emissions of different coronal regions are compared with quiet-time imaging observations between 20-90 MHz by the LOw Frequency ARray (LOFAR) radio telescope. The contribution of gyrosynchrotron radiation to low frequency solar radio emission may shed light on effects such as the hitherto unexplained brightness variation observed in decametric coronal hole emission, and help constrain measurements of the coronal magnetic fields. It can also improve our understanding of electron populations in the middle corona and their relation to the formation of the solar wind.
Measurement of short  (Debye length) scale electrostatic waves with MMS EDP instrument:  Problems and possible mitigation
Authors: Lalti Ahmad , Khotyaintsev Yuri , Graham Daniel , Steinvall Konrad , Johlander Andreas
Published: March 2022

High frequency electrostatic oscillations are one of the most fundamental players in energy conversion in collisionless plasmas. Whether at collisionless shocks, turbulence energy cascades or reconnection, small scale Debye length processes  are at the heart of irreversible energy exchange between particles and fields. MMS is one of the most advanced still active spacecraft, with high resolution field and particle instruments. The electric field instrument (EDP) on board of MMS is formed of 3 axial double probes positioned in a perpendicular configuration allowing for the measurement of the 3D electric field. In this study we probe the limitations of the EDP instrument in measuring Debye-scale electrostatic oscillations. In particular we show that at such small wavelengths the electric field is attenuated due to the finite probe-to-probe separation. Furthermore, we propose a method to correct for the electric field attenuation based on the single spacecraft interferometry technique which will allow us to properly determine the observed wave modes.
A remote sensing-based inventory of West-Africa tropical forest patches 
Authors: Wingate Vladimir , Akinyemi Felicia , Iheaturu Chima , Ifejika Speranza Chinwe
Published: March 2022

The rate of tropical forest fragmentation is increasing globally. This process is essentially driven by commodity demands on the international market, and consequent conversion of forested lands to agricultural land-uses. The extension of urban settlements and other land uses such as roads, infrastructure, small-scale clearing, selective logging, fire, and natural disturbance are major drivers of tropical forest loss and fragmentation.  Even though tropical forests are an essential component of the earth system, and fundamental for biodiversity conservation, ecosystem functioning and social well-being, anthropogenic pressures continue unabated and at an increasing rate. Indeed, recent research has shown that forest fragmentation and loss are particularly high in arable landscapes where fragments are smaller, reflecting their easier access.  As such, there is an urgent need to map and monitor the dynamics of remaining smaller tropical forest patches/fragments and identify their multiple benefits and values. Recognizing their existence is expected to help ensure their continued provision of social-ecological functions, while facilitating their conservation.  The main objective of this study is therefore to inventory and characterise the current extent of forest patches for a West-Africa region (Nigeria), by combining multi-source remote sensing products, time-series analyses, and ancillary datasets.  Here, we collated and analysed descriptive and dynamics metrics derived from various sources, and provide estimates of fragment size, age, biophysical conditions, and relation to social-ecological variables, which together provide insights into their dynamics over four decades. Specifically, forest patches with a tree cover ≥ 30%, a tree height of ≥ 5 m, an area ≥ 1 hectare and ≤ 10 km2 and which are outside of protected areas, are mapped. Appended to each patch are descriptive (country, administrative region, coordinates, area, biome, distance to water and roads, tree height and cover, primary/secondary forest, estimated age) and dynamics attributes (land cover in 1975, forest loss/gain, as well as trend and disturbance metrics for last two decades).  We find tree cover loss is widespread, the more numerous smaller fragments cumulatively lose a greater forested area, while fragment number increased slightly (2000-2020). Widespread greening occurs in larger fragments, the trend is pronounced for secondary forests (which predominate). Patch size is related to human disturbance metrics, e.g., distance to roads, larger patches being more distant. Thus, this inventory forms the basis for understanding forest patch change and condition, as well as prioritizing them for in-depth, social-ecological field investigation and conservation. 
Numerical modelling of lithosphere-asthenosphere interaction and intraplate deformation in the Gulf of Guinea 
Authors: Almeida Jaime , Riel Nicolas , Neres Marta , Custódio Susana , Dumont Stéphanie
Published: March 2022

Despite extensive research, intraplate deformation and associated earthquakes remain elusive. We argue that one potential reason for its occurrence is the interplay between the lithosphere and the upper mantle dynamic processes, specifically the lithosphere-asthenosphere interaction. To explore this possibility, we targeted the Gulf of Guinea and adjacent Western Africa, a region with low plate velocities and clear asthenosphere dynamics, which allows for the isolation of the underlying dynamic constraints which govern intraplate deformation. An in-depth understanding of intraplate deformation mechanisms will contribute towards the improvement of seismic hazard assessment away from plate boundaries.

Thus, here we present exploratory 3D numerical geodynamic models of the asthenosphere-lithosphere interaction in the Gulf of Guinea, ran with the state-of-the-art modelling code LaMEM. We employ different initial/boundary conditions such as: (a) different spreading rates for the Atlantic mid-ocean ridge (from 5 to 25 mm/yr), (b) rheological/lithological configurations (accounting for the cratonic/mobile nature of the region), (c) the presence/absence of weak zones (e.g., the Romanche/Central-African shear zones), and (d) the effect exerted by an active mantle plume. Seismicity data was employed to rank the models to ensure the validity of our results.

Preliminary results suggest that intraplate deformation within the Gulf of Guinea is influenced by the spreading rate of mid-ocean ridge, with stress being localized around the ocean-continent transition and existing shear zones.

This work was developed in the frame of SHAZAM (POCI-01-0415-FEDER-031475). FCT is further acknowledged for support through project UIDB/50019/2020-IDL.
Rapeseed reaches 4 meters depth – but does it escape drought stress?
Authors: Rasmussen Camilla , Rosenqvist Eva , Liu Fulai , Dresbøll Dorte Bodin , Thorup-Kristensen Kristian , Javaux Mathieu
Published: March 2022

Deep-rooted crops, such as rapeseed have access to deep stored soil moisture unavailable to more shallow-rooted crops. However, it appears that the presence of deep roots in moist soil does not necessarily ensure full water supply and prevent drought stress during progressive soil drying. Thus, there is a need to quantify the contribution of deep roots to water uptake and investigate the role of deep roots in delaying drought stress.

In large parts of Europe, climate change will lead to lower precipitation in the growing season and higher outside the growing season. This imbalance can be levelled out by growing summer crops on winter precipitation. However, it requires crops that a capable of utilizing previous surplus precipitation stored deep in the soil profile.

We grew rapeseed in a large-scale semi-field setup, allowing root growth down to 4 meters depth. We monitored the development in root growth, water uptake, stomatal conductance, leaf ABA, photosynthesis, and soil water content during progressive soil drying. This allowed us to investigate the ability of rapeseed to compensate for a lack of water in the upper root zone with water uptake in the deeper root zone and to identify the onset of stress responses.
Error hotpots of the modelled global terrestrial water storage interannual variation
Authors: Lee Hoontaek , Jung Martin , Carvalhais Nuno , Trautmann Tina , Kraft Basil , Reichstein Markus , Forkel Matthias , Koirala Sujan
Published: March 2022

Terrestrial water storage (TWS) is a socially (e.g., floods and drought) and scientifically (e.g., water and carbon cycles) important variable. Hydrological models have been extensively used to study variations in TWS but the models are showing significant uncertainties, especially for the interannual variability (IAV). It is therefore essential for TWS IAV studies to further improve model accuracy, calling for a better understanding of the TWS IAV simulation error. We conducted a covariance matrix analysis to spatially attribute the contributions to global TWS IAV and its simulation error by two hydrological models: 1) a parsimonious process-based one, implemented in the Strategies to INtegrate Data and BiogeochemicAl moDels (SINDBAD) framework, and 2) a hybrid one, the hybrid hydrological model (H2M), which combines a dynamic neural network and a water balance concept. Both models were calibrated against observation-based data streams for evapotranspiration, snow water equivalent, and runoff, as well as against the Gravity Recovery and Climate Experiment (GRACE) satellite observations of TWS. Both models indicate that the global TWS IAV is largely driven by some regions such as Amazon, Zambezi, Mekong basins, and India. The analysis also identified hotspots of the global TWS IAV error from river basins (e.g., Amazon, Paraná, Congo, and Mekong basins) and inland water bodies (e.g., the Laurentian Great Lakes). Excluding those hotspots in the global integration, the 12-month running mean of the global TWS IAV showed a large improvement: R2 of the global TWS IAV time series was improved from 0.62 to 0.82 for SINDBAD and from 0.62 to 0.88 for H2M. Therefore, the model simulation of the global TWS can efficiently be improved by focusing on correcting the hotspot regions. Comparing GRACE and modelled TWS IAV time series revealed various potential sources of errors, including anthropogenic factors (e.g., reservoir management) and model structure (e.g., insufficient storage capacity and missing storage processes), while the latter was prevalent over many regions. A further comparison to surface water data could characterize the hotspots as areas of 1) more dynamic surface water, and 2) wetlands (i.e., near-inland water bodies). These characteristics of hotspots imply that surface water processes (e.g., seasonal inundation) are relevant for understanding global TWS IAV and are underestimated in the two tested models, calling for further improvement in that respect. Our approach presents a general avenue to identify model simulation errors for global data streams and can guide efficient model development.