bluuebunny/crossref_metadata_2025 huggingface dataset:
Stratigraphic and Structural setting of Cenozoic deep-sea units from the Agri valley (southern Apennines, Italy), recording the tectonic evolution of the Southern Apennines.
Authors: Prosser Giacomo , Palladino Giuseppe
Published: March 2021

Cenozoic units from thrust-top and foredeep basins provide crucial information for constraining the progressive evolution of the Southern Apennine thrust and fold belt and, more in general, the geodynamic evolution of the Mediterranean area. For this reason, we have analysed the stratigraphic and tectonic setting of deep-sea Cenozoic units exposed in the southeastern sector of the Agri Valley (Basilicata, Southern Italy), in an area located immediately north of the Montemurro village, between the Costa Molina and Monte dell’Agresto localities. These units have not been studied in detail so far and different interpretations are reported in the literature. The study was based on an accurate field survey which led to a new geological map and to the reconstruction of the stratigraphic and structural setting of the area. Results of the field survey were constrained by well, seismic and new biostratigraphic data kindly provided by Eni. In our study, we focussed on the Albidona Formation, which was deposited in a thrust-top basin on the Liguride accretionary wedge, formed above the NW-dipping subduction of the Ligurian Tethys Ocean during the Late Cretaceous? - Early Miocene. Facies characteristics and age determinations allowed the differentiation of the Albidona Formation in two members, with the older one, identified as Member B-C (Lutetian) consisting of alternating marls, sandstones and clays and the younger one, identified as Member D (Barthonian/Priabonian), consisting in alternating sandstones and conglomerates. In particular, the presence of marker horizons such as a pebbly mudstone containing ophiolite debris strongly helped in the structural reconstructions. By this means, we recognized the presence of two folding phases affecting the Albidona Formation. Moreover, the geometrical relationships between the two members and the overlying Miocene Gorgoglione Formation allowed recognising two major NE-trending normal faults, which crosscut the aforementioned structures. These data provide new indications on the tectonic setting and the evolution of the Southern Apennines thrust and fold belt.
Theory and observations of switchbacks’ evolution in the solar wind
Authors: Tenerani Anna , Velli Marco , Matteini Lorenzo
Published: March 2021

Alfvénic fluctuations represent the dominant contributions to turbulent fluctuations in the solar wind, especially, but not limited to, the fastest streams with velocity of the order of 600-700 km/s. Alfvénic fluctuations can contribute to solar wind heating and acceleration via wave pressure and turbulent heating. Observations show that such fluctuations are characterized by a nearly constant magnetic field amplitude, a condition which remains largely to be understood and that may be an indication of how fluctuations evolve and relax in the expanding solar wind. Interestingly, measurements from Parker Solar Probe have shown the ubiquitous and persistent presence of the so-called switchbacks. These are magnetic field lines which are strongly perturbed to the point that they produce local inversions of the radial magnetic field. The corresponding signature of switchbacks in the velocity field is that of local enhancements in the radial speed (or jets) that display the typical velocity-magnetic field correlation that characterizes Alfvén waves propagating away from the Sun. While there is not yet a general consensus on what is the origin of switchbacks and their connection to coronal activity, a first necessary step to answer these important questions is to understand how they evolve and how long they can persist in the solar wind. Here we investigate the evolution of switchbacks. We address how their evolution is affected by parametric instabilities and the possible role of expansion, by comparing models with the observed radial evolution of the fluctuations’ amplitude. We finally discuss what are the implications of our results for models of switchback generation and related open questions.
Learning Soil Freeze Characteristic Curves with Universal Differential Equations
Authors: Groenke Brian , Langer Moritz , Gallego Guillermo , Boike Julia
Published: March 2021

Permafrost thaw is considered one of the major climate feedback processes and is currently a significant source of uncertainty in predicting future climate states. Coverage of in-situ meteorological and land-surface observations is sparse throughout the Arctic, making it difficult to track the large-scale evolution of the Arctic surface and subsurface energy balance. Furthermore, permafrost thaw is a highly non-linear process with its own feedback mechanisms such as thermokarst and thermo-erosion. Land surface models, therefore, play an important role in our ability to understand how permafrost responds to the changing climate. There is also a need to quantify freeze-thaw cycling and the incomplete freezing of soil at depth (talik formation). One of the key difficulties in modeling the Arctic subsurface is the complexity of the thermal regime during phase change under freezing or thawing conditions. Modeling heat conduction with phase change accurately requires estimation of the soil freeze characteristic curve (SFCC) which governs the change in soil liquid water content with respect to temperature and depends on the soil physical characteristics (texture). In this work, we propose a method for replacing existing brute-force approximations of the SFCC in the CryoGrid 3 permafrost model with universal differential equations, i.e. differential equations that include one or more terms represented by a universal approximator (e.g. a neural network). The approximator is thus tasked with inferring a suitable SFCC from available soil temperature, moisture, and texture data. We also explore how remote sensing data might be used with universal approximators to extrapolate soil freezing characteristics where in-situ observations are not available.
Modeling surface deformation of geothermal environments with high-fidelity finite element models
Authors: Tung Sui , Feigl Kurt
Published: March 2021

The geothermal environment is an assembly of heterogeneous geological settings and complex interactions among different phases of rock and fluid medium. The artificial activities of energy production could further interplay with the on-going natural processes within volcanos, hotspots, and other geothermal areas to result in spatiotemporal signatures of displacements near the surface. Here, we study the temporal ground deformation near a geothermal site through processing Interferometric Synthetic Aperture Radar (InSAR) time-series data obtained over the past decades, as reconciled with the nearby GPS station. To interpret these signals and potentially reveal the reservoir’s temporal activity, we employ state-of-art finite element models (FEMs) to simulate a more realistic crustal domain near the energy-production zone with irregular reservoir geometry, distributed rock materials, and surface topography. Linear Bayesian geodetic inversion and Green’s function library area were adopted to quantify the cause of surface subsidence, as compared to the documented production history. Our study demonstrates an unprecedented approach to precisely simulate the elastic deformation caused by geothermal energy extraction and pumping, providing an important platform to further explore the in-depth evolving stress state and its relation to surrounding induced and natural seismicity.
The effect of cover crops on soil structure is mainly driven by root architecture
Authors: Lucas Maik , Nguyen Linh , Guber Andrey , Kravchenko Alexandra
Published: March 2021

Cover crops are known to increase macroporosity and pore connectivity, thus having a beneficial effect on soil hydraulic properties such as saturated hydraulic conductivity, However, cover crop species typically used encompass a variety of contrasting root architectures and their effects on small-scale pore properties are difficult to quantify.

Here we explore the influence of five different cover crops (annual ryegrass, Austrian winter pea, dwarf essex rapeseed, oats, and oilseed radish) on soil structure with X-ray µCT. Undisturbed samples were taken from an experiment with these cover crops on Kellogg Biological Station (Michigan, USA) in October 2019. Two soil columns with a diameter of 5 cm were taken in 5 - 10 cm depth from each of three replicated plots per plant species and scanned with X-ray µCT at a resolution of 18 µm.

These images will be used to characterize pore structure in terms of pore size distribution, pore connectivity. In addition, a new imaging protocol will be used, which combines existing ones with a random forest classifier to segment image features such as pores, biopores and roots simultaneously.

First, the results reveal that different cover crops indeed result in different pore characteristics.  The fibrous root system of oats leads to the highest volume of narrow macropores and increased their connectivity, while the tap root system of dwarf essex rapeseed mainly effected wide macropores.  The highly diverse root system of Australian winter pea increased a wide range of pore sizes and thus resulted in the highest visible porosity.

The current study is funded by a grant from USDA Organic Transition program
On the semi-annual variation of relativistic electrons in the outer radiation belt
Authors: Aminalragia-Giamini Sigiava , Katsavrias Christos , Papadimitriou Constantinos , A. Daglis Ioannis , Sandberg Ingmar , Jiggens Piers
Published: March 2021

The nature of the semi-annual variation in the relativistic electron fluxes in the Earth’s outer radiation belt is investigated using Van Allen Probes (MagEIS and REPT) and GOES (EPS) data during solar cycle 24. We perform wavelet and cross-wavelet analysis in a broad energy and spatial range of electron fluxes and examine their phase relationship with the axial, equinoctial and Russell-McPherron mechanisms. It is found that the semi-annual variation in the relativistic electron fluxes exhibits pronounced power in the 0.3 – 4.2 MeV energy range at L-shells higher than 3.5 and, moreover, it exhibits an in-phase relationship with the Russell-McPherron effect indicating the former is primarily driven by the latter. Furthermore, the analysis of the past 3 solar cycles with GOES/EPS indicates that the semi-annual variation at geosynchronous orbit is evident during the descending phases and coincides with periods of a higher (lower) HSS (ICME) occurrence.

This work has received funding from the European Union's Horizon 2020 research and innovation programme “SafeSpace” under grant agreement No 870437 and from the European Space Agency under the “European Contribution to International Radiation Environment Near Earth (IRENE) Modelling System” activity under ESA Contract No 4000127282/19/NL/IB/gg.
The effect of harvesting on national forest carbon sinks up to 2050 simulated by the CBM-CFS3 model: a case study from Slovenia
Authors: Mali Bostjan , Jevsenak Jernej , Klopcic Matija
Published: March 2021

With the advent of global warming, forests are becoming an increasingly important carbon sink that can mitigate the negative effects of climate change. An understanding of the carbon dynamics of forests is, therefore, crucial to implement appropriate forest management strategies and to meet the expectations of the Paris Agreement with respect to international reporting schemes. One of the most frequently used models for simulating the dynamics of carbon stocks in forests is the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3). We applied this model in our study to evaluate the effects of harvesting on the carbon sink dynamics in Slovenian forests. Five harvesting scenarios were defined: (1) business as usual (BAU), (2) harvesting in line with current forest management plans (PLAN), (3) more frequent natural hazards (HAZ), (4) high harvest (HH) and (5) low harvest (LH). The simulated forest carbon dynamics revealed important differences between the harvesting scenarios. Relative to the base year of 2014, by 2050 the carbon stock in above-ground biomass is projected to increase by 28.4% (LH), 19% (BAU), 10% (PLAN), 6.5% (HAZ) and 1.2% (HH). Slovenian forests can be expected to be a carbon sink until harvesting exceeds approximately 9 million m3 annually, which is close to the calculated total annual volume increase. Our results are also important in terms of Forest Reference Levels (FRL), which will take place in European Union (EU) member states in the period 2021-2025. For Slovenia, the FRL was set to –3270.2 Gg CO2 eq/year, meaning that the total timber harvested should not exceed 6 million m3 annually.
Covid-19: What about Resilience and Scaling Dynamics?
Authors: Schertzer Daniel , Tchiguirinskaia Ioulia
Published: March 2021

The current Covid-19 pandemic has underlined the need to thoroughly revisit our conceptions of managing and developing urban systems and to make them resilient to epidemics. For  instance, it fundamentally questions the long-held goal of continually increasing human mobility. More generally, the definition of optimal Covid-19 mitigation strategies remains worldwide on the top of public health agendas, especially in the face of a second wave. However, the relevance of resilient strategies depends heavily on our understanding and our ability to model epidemic dynamics.

Epidemic models are phenomenologically based on the paradigm of a cascade of contacts that spreads infection. However, scaling -a fundamental characteristic that easily results from cascade models,- is not taken into account by conventional epidemic models.  The introduction of ad-hoc characteristic times and corresponding rates spuriously break their scale symmetry.

Here, we theoretically argue and empirically demonstrate that Covid-19 dynamics, during both growth and decline phases, is a cascade with a rather universal scale symmetry whose power-law statistics drastically differ from those of exponential processes. This implies slower but longer phases; which are furthermore linked by a fairly simple symmetry. The resulting variability across space-time scales is a major feature that requires alternative approaches with practical consequences for data analysis and modelling. We illustrate some of these consequences using the Johns Hopkins University Center for Systems Science and Engineering database. 

The obtained results explain biases of epidemic models and help to improve them. By virtue of their generality, these results pave the way for a renewed approach to epidemics, and more generally to growth phenomena, towards more resilient development and management of our urban systems.
SubSpread: An integrated approach to understand the signature, mechanics and controls of subaqueous spreading
Authors: Giona Bucci Monica , Micallef Aaron , Urlaub Morelia , Mountjoy Joshu
Published: March 2021

Subaqueous spreading is a widespread type of mass movement, which involves extensional displacement along a gliding plane and the deformation of the failing layer into a sequence of ridges and troughs. Spreading has been poorly investigated, nonetheless it poses hazard to offshore infrastructures. SubSpread is a new project that will investigate the mechanics of the spreading failure and its geological controls in the subaqueous environment. The first objective of SubSpread is to identify the topographic and sedimentary signature of subaqueous environment. We have compiled a global database of subaqueous and subaerial spreads that includes information on physiography, geomorphology, sedimentology and geotechnical properties, where available. A preliminary analysis of the database reveals that spreading morphologies occur on both passive and active margins, especially in the headwall area of translational retrogressive slides. Potential causes of spreading include seismic loading (also glacially induced), sediment loading, and increased pore pressure generated by migration of fluid or gas. The latter may induce loss of shear strength and the formation of a weak layer, particularly in gentle open slopes. Information compiled in this database will also be used to develop a numerical model that can better understand the mechanics and rheological aspects of submarine spreading, focusing on the role played by pore pressure generation. The Tuaheni slide complex in the Hikurangi Margin of New Zealand is being used as a case-study in view of the wealth of geophysical and sedimentological data that are available. The final part of the SubSpread project will test whether the morphometric and sedimentological signature of spreading can provide information on past seismicity. In this case, the test site will be Lake Tekapo in the South Island of New Zealand.
Modelling the Covid-19 impact on CO2 concentrations in Germany
Authors: Kaiser-Weiss Andrea K. , Mamtimin Buhalqem , Roth Franziska , Sunkisala Anusha , Förstner Jochen
Published: March 2021

The sharp decrease in emissions caused by the Corona crisis entails the question: where, when, and how strong impacts on observations can be expected? The Icosahedral Nonhydrostatic (ICON) model is online-coupled to the modules for Aerosols and Reactive Trace gases (ART). With the model system ICON-ART run at roughly 13km resolution we determine how CO2 emission reductions in Germany relate to a reduction in CO2 concentrations. This varies over several orders of magnitude, depending on the weather related atmospheric transport. We compare this with the emission reduction effect originating from outside Germany. In a case study, we identify locations and times, where either effect reaches a magnitude to be observable at the Integrated Carbon Observation System (ICOS) towers in Germany. In contrast, there are also weather situations, where both contributions (from inside/outside Germany) are negligible with respect to the background variability. Reducing background uncertainty, as foreseen in the CoCO2 project, will allow better disentangling of the national contribution in future. Here we focus on the height dependency of the modelled concentration change with respect to recent anthropogenic emissions. We draw conclusions on measurement and modelling capabilities essential for an integrated greenhouse gas monitoring system for Germany to detect anthropogenic emission reductions.
Monitoring and assessment of an oil spill event with very high resolution tools. 
Authors: Mancho Ana M. , García-Sánchez Guillermo , Ramos Antonio G. , Coca Josep , Pérez-Gómez Begoña , Álvarez-Fanjul Enrique , Sotillo Marcos G. , García-León Manuel , García-Garrido Víctor J. , Wiggins Stephen
Published: March 2021

This presentation discusses a downstream application from Copernicus Services, developed in the framework of the IMPRESSIVE project, for the monitoring of  the oil spill produced after the crash of the ferry “Volcan de Tamasite” in waters of the Canary Islands on the 21st of April 2017. The presentation summarizes the findings of [1] that describe a complete monitoring of the diesel fuel spill, well-documented by port authorities. Complementary information supplied by different sources enhances the description of the event. We discuss the performance of very high resolution hydrodynamic models in the area of the Port of Gran Canaria and their ability for describing the evolution of this event. Dynamical systems ideas support the comparison of different models performance. Very high resolution remote sensing products and in situ observation validate the description.

Authors acknowledge support from IMPRESSIVE a project funded by the European Union’s Horizon 2020 research and innovation programme under grant agreement No 821922. SW acknowledges the support of ONR Grant No. N00014-01-1-0769

References

[1] G.García-Sánchez, A. M. Mancho, A. G. Ramos, J. Coca, B. Pérez-Gómez, E. Álvarez-Fanjul, M. G. Sotillo, M. García-León, V. J. García-Garrido, S. Wiggins. Very High Resolution Tools for the Monitoring and Assessment of Environmental Hazards in Coastal Areas.  Front. Mar. Sci. (2021) doi: 10.3389/fmars.2020.605804.
Analogue modelling of strike-slip tectonics from basin to structural-scale comparing silica sand and new rock-analogue materials
Authors: Massaro Luigi , Adam Jürgen , Jonade Elham , Yamada Yasuhiro
Published: March 2021

Strike-slip fault zones commonly display complex 3D geometries, with high structural variability along strike and with depth and their architecture and evolution are difficult to analyse. In this regard, analogue modelling represents a powerful tool to investigate the structural, kinematic and mechanical processes in strike-slip fault systems with variable scales. In detail, dynamically scaled experiments allow the direct comparison between model and nature. The geometrical scale factor defines the model resolution, in terms of model/prototype length equivalence, and depends on the physical properties of prototype and model material. Therefore, the choice of the analogue material is critical in scaled analogue experiments.
Granular materials like dry silica sand are ideal for the simulation of upper crustal deformation processes due to similar non-linear strain-dependent deformation behaviour of granular flow and brittle rock deformation. Comparing the geometrical scaling factor of the common analogue materials applied in tectonic models, we identified a model resolution gap for the simulation of fault-fracture processes corresponding to the structural scale (1 m – 100 m) observed in fault zones and damage zones in outcrops, field studies or subsurface well data. We developed a new Granular Rock-Analogue Material (GRAM) for the simulation of fault-fracture processes at the structural scale. GRAM is an ultra-weak sand aggregate composed of silica sand and hemihydrate powder capable to deform by tensile and shear failure under variable stress conditions. Based on dynamical shear tests, the new GRAM is characterised by a similar stress-strain curve as dry silica sand and has a geometrical scaling factor L*= Lmodel/Lnature = 10-3 (1 cm in model = 20 m in nature).
We performed strike-slip experiments at two different length scales, applying as model material dry silica sand and the new GRAM. Digital Image Correlation (DIC) time-series stereo images of the experiments surface allowed the comparison of the developed structures at different stages of dextral displacement above a single planar basement fault. The analysis of fractures localisation and growth in the strike-slip zone with displacement and strain components enabled the comparison of the different structural styles characterising dry silica sand and GRAM models. The application of the developed GRAM in scaled experiments can provide new insights to the multi-scale investigation of complex deformation processes with analogue models. 
The transition toward resilient water management regimes: where are we now?
Authors: Mannocchi Matteo
Published: March 2021

Hydro-Meteorological Hazards (HMH) such as drought, floods and storm surge have always constituted a threat to social-ecological systems (SES) but, due to increasing uncertainties caused by climate and by rapidly changing socio-economic boundary conditions, it is necessary to step up effort to mitigate the risks. More attention should be devoted to understanding and managing the transition from traditional management regimes to more sustainable and resilient regimes that take into account environmental, technological, economic, institutional and cultural characteristics of river basins.

Since the 1990s many scholars, from both natural and social sciences, have urged to integrate knowledge and shed light on the functioning of the SESs in order to increase resilience to perturbances (Berkes and Folke 1998). As sustainability science is mainly a problem-driven and solution-oriented field that follows a transformational agenda (Lang 2012), it becomes evident that the nexus between environmental, political and institutional dimensions cannot be ignored to accelerate the path toward sustainability.  

There is consensus that the complex, non-linear and rather unpredictable nature of HMHs, exacerbated by climate change, should require a more adaptive (Armitage 2007), flexible and holistic (Holling 2002) management approach that can speed up and reinforce the learning loops to allow for more rapid assessment and implementation of the consequences of new insights and scientific evidence (Pahl Wostle 2007). Cooperation among a wide range of stakeholders with different knowledge, expertise and views is often indicated as a prerequisite to establish a resilient and adaptive water management regime (Olsson et al. 2004). These principles mainstreamed since the beginning of the 2000s and synthesized by concepts like “co-management”, “adaptive and integrated management”, or “adaptive co-management”, are the pillars of what is considered a paradigm shift in water management (Pahl Wostle and Nicola 2011) and have inspired institutional settings, policies, and practices.

However, the debate is still ongoing to determine at what stage of the transition we are in, whether the aforementioned principles have been adopted and translated into practices on a wide scale, and whether and how such practices have contributed to increasing the resilience of the SES. It will be critically examined the literature trying to identify the main trend of the last two decades. The review will be accompanied by the case-studies upon which theories have been built and tested.
Measurements of airborne particles and chemical identification of metal content in a public underground transport system
Authors: Crazzolara Claudio , Lüchtrath Sabine , Stosnach Hagen , Held Andreas
Published: March 2021

In urban areas, a large number of people use public transport systems on a daily basis, and depending on the length of their commute, they spend a considerable amount of time in it. Part of the public transport system runs underground. Even though underground trains are powered by electric traction motors, the accumulation of airborne particles may be of concern due to limited air exchange in underground transport systems.

Initial measurements carried out in previous studies worldwide have shown that the air in a subway train station can be considerably more polluted with particulate matter than the air at a busy road junction. PM10 mass concentrations as high as 120 µg/m3 have been measured at a subway train station in Stuttgart. This is more than double the daily average PM10 limit value of 50 µg/m3 for outside air in Europe.

In order to study particulate matter concentrations in the underground transport system of Berlin (Germany) and potential particle sources, first semester students carried out preliminary measurements in a student project in January 2021. The students were equipped with handheld optical particle counters to study particulate matter levels at various locations of the underground transport system and at roadside station at street level for comparison. In additions, airborne particles were collected by using a single staged impactor, and subsequently analysed for their metal content using Total Reflection X-ray Fluorescence (TXRF) analysis.

The results indicate significantly elevated PM10 levels in underground train stations compared to street levels. Up to 35 times as much iron was found in the air of an underground train station compared to a busy street intersection at Potsdamer Platz. These high levels of iron suggest that a reason for the elevated concentrations of particulate matter in the underground system could be abrasion from wheels and rails.

This preliminary study sets the basis for a more comprehensive investigation of PM sources in public underground transport systems required to evaluate its effect on urban air quality.
Analysis of the influence of storms on massive marine litter wash-outs to the shore of the Sambian Peninsula
Authors: Fetisov Sergei , Chubarenko Irina
Published: March 2021

The problem of contamination of the shore of the Sambian Peninsula with marine anthropogenic litter is pressing and requires detailed study since it has a detrimental effect on the touristic and recreational activity of the region. Observations show that the most volumetric marine litter wash-outs to the beach take place after certain storms and are associated with abundant spots ofbiota (primarily branched Furcellaria lumbricalis). Such spots contain litter of anthropogenic origin, such as glass, paper, etc., along with macro and micro plastics. In this paper, meteorological and hydrophysical data were collected and analyzed in order to determine the most significant factors causing the wash-outs of anthropogenic marine litter to the shore of Sambian Peninsula. Both in-situ observations and reanalysis datasets were used for the analysis. It was revealed that the wash-out to the shore occurs during the storm subsiding phase, and the determining factors are significant wave height, wind speed and current velocity during the preceding storm.

Investigations are supported by the Russian Science Foundation, grant No 19-17-00041 and IKBFU competitiveness improvement program for 2016-2020 (project 5-100).
Experimental and numerical investigation of microparticle transport and deposition in the context of permafrost thaw
Authors: Khadhraoui Madiha , Molson John , Bhiry Najat
Published: March 2021

In natural porous environments, soil particle migration during flow plays an important role in soil stability and pollutant transport by affecting soil mechanical properties and water quality. In northern areas, permafrost degradation alters the subsurface connection pathways leading to mass movements and rearrangement of the soil. To date, few models have included the influence of temporal and spatial variations of flow velocity and porous media heterogeneity on the transport and deposition of suspended particles.

In this study, laboratory column experiments and a numerical model were used to investigate these issues. The laboratory column experiments were carried out under different flow rates and the effect of porous media heterogeneity was investigated using different grain size distributions. The soil columns were reconstituted from several samples taken in the studied site, the Tasiapik Valley, located in the discontinuous permafrost zone near Umiujaq, Nunavik, Québec. During the experiments, the spatio-temporal distribution of the porosity and the hydraulic conductivity was monitored using X-ray computed tomography imaging (CT-SCAN). Using the pore water velocity computed from the groundwater flow solution, the advection–dispersion transport equation with a first-order kinetic term for particle deposition was solved using the finite element model Heatflow/Smoker. The dependency of the attachment kinetics on the pore water velocity and on the porous media heterogeneity was included. The model was tested and validated with an analytical solution and calibrated with the experimental data. Our simulations highlight the roles of hydrodynamic conditions and soil characteristics on particle transport and deposition mechanisms and the susceptibility of the porous medium to thermo-suffosion in permafrost environments.
Northern Appalachian, USA relic charcoal hearths and their unique Ecological Fingerprint 
Authors: Drohan Patrick , Bayuzick Samuel , Diefenbach Duane , McDill Marc , Raab Thomas , Hirsch Florian , Bonhage Alexander
Published: March 2021

Abrupt changes in a forest ecosystem, whether natural or anthropogenic, are changes that occur over short time periods; such disturbance has the potential to drive state changes and alter forest resilience. Understanding how present-day abrupt forest change may alter ecosystem services is becoming more important due to ever-growing anthropogenic stresses. Forest managers trying the adapt to anthropogenic stress can benefit from the study and quantification of past abrupt changes in forests, especially when the legacy of past disturbance is still evident. Across the United Kingdom, Europe, and recently the northeastern United States, the examination of historic forest change due to charcoal manufacturing for the firing of iron or lime furnaces is yielding new insights relative to landscape stability, anthropogenic vs natural soil genesis, and forest evolution. We present results of a study that strives to evaluate how historic land clearing for the charcoal industry (supporting iron furnaces) affected local soils and may drive surrounding present day forest composition. We incorporate field sampling of hearth soils and modeled hydrologic parameters (in hearth and non-hearth areas), to quantify the uniqueness of relict charcoal hearth (RCH) systems. We identified 1,239 hearths using a LiDAR terrain analysis; approximately 10% of these were visited to quantify hearth morphology and soil moisture differences on and off hearth. Nine hearths from this 10% were intensively sampled and were associated with a northern Appalachian, USA furnace that was in operation from 1867 to 1904. Three profiles were excavated across each hearth and compared to an adjacent soil profile on the same contour. Soil descriptions were made of hearths and soil samples analyzed for total, trace and rare earth element content (Aqua Regia digestion). Soil pH (water) and fertility (Mehlich III extraction) were also determined. Results indicate that hearths have a unique geochemistry with higher bases and some concentrated metals and higher organic carbon. Coupled with a higher hearth soil water content, hypothesized to be due to an observed restrictive subsurface morphology and higher organic carbon, hearths are potentially unique locations of refugia for forest flora and fauna. Future research should more closely investigate whether hearths support unique species assemblages and how they may play a role in enhancing today’s forest biodiversity.
Kinetics and mechanism of phosphate release upon sulfidation of phosphate-containing lepidocrocite
Authors: Ma Mingkai , Voegelin Andreas , Behrends Thilo
Published: March 2021

Sulfidation of Fe(III) (hydr)oxides plays an important role in the phosphate(P) cycle in oceans and lakes. P has a strong affinity to Fe(III) (hydr)oxides and can either become incorporated via coprecipitation or adsorb onto the solid’s surface. Consequently, P enters aquatic sediments often associated with Fe(III) (hydr)oxides. In the sediments, when sulfidic conditions are prevalent, the reaction of Fe(III) (hydr)oxides with sulfide can lead to the formation of Fe(II) sulfides and P release. The released P can, in turn, diffuse upwards into the overlying water and thus aggravate eutrophication in water bodies.  Although it is generally expected that P is released during the sulfidation of P containing Fe(III) (hydr)oxides, questions remain whether part of the P could be re-adsorbed onto the products of the sulfidation reaction, or trigger the formation of vivianite [1] (Fe3(PO4)2 · 8H2O). Furthermore, it is still unclear how the rates of P release are related to the progress of the sulfidation reaction.

In order to study the P dynamics during sulfidation, we performed experiments in flow-through reactors with P-bearing lepidocrocite (γ-FeOOH). The inflow solution contained sulfide and we monitored P, dissolved S(-II) and Fe(II) in the outflow to follow the progress of sulfide consumption and P release. Sulfide concentrations in the outflow of reactors containing lepidocrocite with adsorbed P tended to be lower than in the outflow of reactors with lepidocrocite but no P. Consequently, the preliminary results indicate that consumption rates of sulfide by the reaction with lepidocrocite were lower when P was present, implying that adsorbed P reduced the rates of sulfidation. At the beginning of the experiment, P concentrations in the outflow remained low, then started to increase and reached a steady state after passing several reactor volumes. This indicates that P was not instantaneously released upon sulfide adsorption but only as lepidocrocite sulfidation progressed. At the end of the experiment, the fraction of P released from the reactor was significantly lower than the fraction of lepidocrocite that had reacted with sulfide(calculated from cumulative sulfide consumption and solid phase characterization). This implies that part of the P has been retained in the solid phase despite the reductive transformation of lepidocrocite. The underlying mechanisms of P retention and the complex relationship between the rates of sulfide consumption and P release will be discussed.

References

[1] Jilbert and Slomp, 2013. Geochimica et Cosmochimica Acta 107, 155-169.
The effect of geothermal heat flux on the deglacial evolution of the Greenland ice sheet
Authors: Ajourlou Parviz , PH Lapointe François , A Milne Glenn , Martos Yasmina
Published: March 2021

Geothermal heat flux (GHF) is known to be an important control on the basal thermal state of an ice sheet which, in turn, is a key factor in governing how the ice sheet will evolve in response to a given climate forcing. In recent years, several studies have estimated GHF beneath the Greenland ice sheet using different approaches (e.g. Rezvanbehbahani et al., Geophysical Research Letters, 2017; Martos et al., Geophysical Research Letters, 2018; Greve, Polar Data Journal, 2019). Comparing these different estimates indicates poor agreement and thus large uncertainty in our knowledge of this important boundary condition for modelling the ice sheet. The primary aim of this study is to quantify the influence of this uncertainty on modelling the past evolution of the ice sheet with a focus on the most recent deglaciation. We build on past work that considered three GHF models (Rogozhina et al., 2011) by considering over 100 different realizations of this input field. We use the uncertainty estimates from Martos et al. (Geophysical Research Letters, 2018) to generate GHF realisations via a statistical sampling procedure. A sensitivity analysis using these realisations and the Parallel Ice Sheet Model (PISM, Bueler and Brown, Journal of Geophysical Research, 2009) indicates that uncertainty in GHF has a dramatic impact on both the volume and spatial distribution of ice since the last glacial maximum, indicating that more precise constraints on this boundary condition are required to improve our understanding of past ice sheet evolution and, consequently, reduce uncertainty in future projections.
Helicopter Liming to Help Restore Acidified Forest Soil Productivity 
Authors: McCavour Caitlin , Sterling Shannon , Keys Kevin , Halfyard Edmund
Published: March 2021

Decades of acid deposition across northeastern North America has caused excess leaching of soil base cations (Ca2+, Mg2+, K+) and increases in bioavailable aluminum (Al3+) that, in combination, have resulted in widespread decreases in potential forest productivity. Despite major reductions in SO2 and NOx emissions since the 1990s, forest soils across the region have shown few signs of recovery from acid deposition impacts and it could take decades or centuries for natural recovery to occur. As a result, affected forests are stressed, less productive, and more prone to climate change-induced damage. Helicopter liming of upland forests may be an effective way to jump-start the soil recovery process. Here we report on early results (one-year) from a helicopter liming trial in Nova Scotia, Canada where 10 tonnes/ha of dolomitic limestone was applied to approximately 8 ha of mature red spruce (Picea rubens) and mature tolerant hardwood (Acer spp. and Betula spp.) forest. Data are presented on (i) the effectiveness of helicopter liming in forests; (ii) the initial chemical response of forest floor organic and mineral soil horizons; and (iii) the initial chemical response of red spruce foliage, maple foliage, and ground vegetation. Preliminary results showed that despite non-uniform lime distribution, there were significant increases (P < 0.05) in Ca2+, Mg2+, pH, and base saturation (BS), and significant decreases in total acidity in forest floor organic horizons in both the mature red spruce and tolerant hardwood stands; however, there were no significant changes in Al3+. The initial chemical response in sugar maple and red spruce foliage showed significant increases in the Ca/Al molar ratio .  The initial response in ground vegetation (Schreber’s moss; Pleurozium schreberi and wood fern; Dryopteris intermedia) showed significant increases in Ca2+ and decreases in K+ for both species; however, Schreber’s moss also showed significant increases in Mg2+ and Al3+ while wood fern did not. These early chemical results are promising and further support the use of helicopter liming as an effective tool to combat lingering effects from acid deposition in acidified forests.
Do convection-permitting ensembles lead to more skilful short-range probabilistic rainfall forecasts over tropical East Africa ?
Authors: Cafaro Carlo , Woodhams Beth J. , Stein Thorwald H. M. , Birch Cathryn E. , Webster Stuart , Bain Caroline L. , Hartley Andrew , Clarke Samantha , Ferrett Samantha , Hill Peter
Published: March 2021

Convection-permitting ensemble prediction systems (CP-ENS) have been implemented in the
mid-latitudes for weather forecasting timescales over the past decade, enabled by the increase in
computational resources. Recently, efforts are being made to study the benefits of CP-ENS for
tropical regions. This study examines CP-ENS forecasts produced by the UK Met Office over
tropical East Africa, for 24 cases in the period April-May 2019. The CP-ENS, an ensemble with
parametrized convection (Glob-ENS), and their deterministic counterparts are evaluated against
rainfall estimates derived from satellite observations (GPM-IMERG). The CP configurations have
the best representation of the diurnal cycle, although heavy rainfall amounts are overestimated
compared to observations. Pairwise comparisons between the different configurations reveal that
the CP-ENS is generally the most skilful forecast for both 3-h and 24-h accumulations of heavy
rainfall (97th percentile), followed by the CP deterministic forecast. More precisely, probabilistic
forecasts of heavy rainfall, verified using a neighbourhood approach, show that the CP-ENS is
skilful at scales greater than 100 km, significantly better than the Glob-ENS, although not as good
as found in the mid-latitudes. Skill decreases with lead time and varies diurnally, especially for
CP forecasts. The CP-ENS is under-spread both in terms of forecasting the locations of heavy
rainfall and in terms of domain-averaged rainfall. This study demonstrates potential benefits in
using CP-ENS for operational forecasting of heavy rainfall over tropical Africa and gives specific
suggestions for further research and development, including probabilistic forecast guidance.
Mixed cultures,a sustainable way to accelerate phytomining of rare earth elements, is there a future here?
Authors: Monei Nthati , Wiche Oliver , Hitch Michael , Heilmeier Hermann
Published: March 2021

This study aims to identify the effects of having narrow leaf lupine grown in a mixed culture with barley at different proportions when different treatment regimens are introduced to the plants. The effects of the usage of fertilizer, NK and NPK on the plants are determined, where the absence and presence and absence of phosphorus will be used to determine the variation in REE accumulation. Furthermore, to investigate how the carboxylate-based strategies for nutrient acquisition in the rhizosphere of Lupinus angustifolius, affect the availability of trace elements to the neighbouring species (in this case barley) and are traceable by rare earth element (REE) pattern.  Barley (Hordeum vulgare L. cv. Modena) was cultivated with narrow leaf lupin (Lupinus angustifolius). The experimental design involved both a monoculture (L0) and mixed cultures, where barley was replaced with narrow leaf lupin at two different proportions 11 and 33 % (Lan 11 and Lan 33). To test the influence of fertilizer on the accumulation of REEs, the plants were further treated with two variated fertilizer options; nitrogen (N), phosphorus (P) and potassium (K) and on the contrary just N & K. Elemental concentrations within the leaves and stems of the barley were determined by ICP-MS. In the presence of P (NPK treatment) An increase in LREE is observed in the leaves of barley than in the stems. There is a statistically significant difference between L0 and Lan 11. HREE also shows an increased uptake in the leaves than in stems. The behaviour of both LREE and HREE from the NK treatment show a similar pattern for both stems and leaves, however, at lower concentrations than when P is present. From the obtained results we can conclude that the presence of P increases the availability of REEs, particularly LREE. Furthermore, intercropping with narrow leaf lupin positively influences the uptake of trace REEs, thus increasing their availability to adjacent plants.
The Impact of Mixed-Phase Microphysical Processes on the Turbulence in Low-level Clouds in the Arctic
Authors: Chylik Jan , Neggers Roel
Published: March 2021

The proper representation of Arctic mixed-phased clouds remains a challenge in both weather forecast and climate models. Amongst the contributing factors is the complexity of turbulent properties of clouds. While the effect of evaporating hydrometeors on turbulent properties of the boundary layer has been identified in other latitudes, the extent of similar studies in the Arctic has been so far limited.

Our study focus on the impact of heat release from mixed-phase microphysical processes on the turbulent properties of the convective low-level clouds in the Arctic. We  employ high-resolution simulations, properly constrained by relevant measurements.
Semi-idealised model cases are based on convective clouds observed during the recent campaign in the Arctic: ACLOUD, which took place May--June 2017 over Fram Strait. The simulations are performed in Dutch Atmospheric Large Eddy Simulation (DALES) with double-moment mixed-phase microphysics scheme of Seifert & Beheng.

The results indicate an enhancement of boundary layer turbulence is some convective regimes.
Furthermore, results are sensitive to aerosols concentrations. Additional implications for the role of mixed-phase clouds in the Arctic Amplification will be discussed.