bluuebunny/crossref_metadata_2025 huggingface dataset:
Decomposition of the switchback boundary on MHD wave modes.
Authors: Krasnoselskikh Vladimir , Larosa Andrea , Dudok de Wit Thierry , Agapitov Oleksiy , Froment Clara , Kretzschmar Matthieu , Jagarlamudi Vamsee , Velli Marco , Bale Stuart D. , Goetz Keith , Harvey Peter , Kasper Justin , Korreck Kelly , Larson Davin , MacDowall Robert , Malaspina David , Mozer Forrest , Pulupa Marc , Reveillet Claire , Stevens Michael
Published: March 2021

Switchback boundaries separate two plasmas moving with different velocities, that may have different temperatures and densities and typically manifest sharp magnetic field deflections through the boundary. They may be analyzed similarly to MHD discontinuities. The first step of their characterization consists of analysis in terms of MHD discontinuities. Such an analysis was performed by Larosa et al., (2021) who has found that 32% of them may be attributed to rotational discontinuities, 17% to tangential, about 42% to the group of discontinuities that are difficult to unambiguously define whether they are tangential or rotational, and 9% that do not belong to any of these two groups. We describe and apply hereafter for two events another approach for the characterization of the boundaries based on classification of the general type discontinuity in MHD approximation. It is based on the problem of the decay of the general type of discontinuity. It is well known [Kulikovsky and Lyubimov, 1962, Gogosov, 1959} that general type MHD discontinuity decays on 7 separate discontinuities belonging to different types of MHD waves, namely, entropic wave, two slow mode waves, two Alfvenic waves, and two fast mode waves. Entropic wave is standing in the reference frame of the discontinuity; other wave modes are supposed to run in the opposite directions from the initial discontinuity with their characteristic velocities. Making use of plasma parameters from two sides of the boundary one can evaluate the fraction of each wave mode present in the discontinuity. We apply this method to two boundary crossings. This repartition of the discontinuity allows characterizing the deviation from Alfvenicity quantitatively.

References

Larosa, A., et al., A&A, 2021, (accepted)

Kulikovsky, Lyubimov, Magnetohydrodynamics, (1962)

Gogosov, V.V., Decay of the MHD discontinuity, (1959)
Trait-Based Modeling of Microbial Interactions and Carbon Cycling in the Rhizosphere
Authors: Sircan Ahmet , Giraud Mona , Lobet Guillaume , Schnepf Andrea , Streck Thilo , Pagel Holger
Published: March 2021

 The rhizosphere shows complex spatial and temporal patterns of biophysical and biochemical processes. Process-based modeling that accounts for functional microbial traits provides a tool to gain a better understanding of microbial interactions involved in carbon cycling in the rhizosphere. Here, we present a trait-based rhizosphere model that accounts for microbial life-history strategies (copiotrophs, oligotrophs), microbial physiology (e.g., dormancy), and organic carbon bioaccessibility (small and large polymers). The model reflects the mm-scale microbial and carbon dynamics around a cylindrical root segment and will be linked with a structural-functional soil-plant model (CPlantBox), which enables to connect water, carbon and nitrogen dynamics in the rhizosphere to plant and bulk soil dynamics. We show the concept of trait-based rhizosphere modeling, first simulations, and our model coupling approach to CPlantBox.

 
Global glacio-hydrological model coupling for streamflow prediction
Authors: Wiersma Pau , Hut Rolf , Aerts Jerom , Drost Niels , Zekollari Harry , Hrachowitz Markus
Published: March 2021

Global hydrological models (GHMs) have become an increasingly valuable tool in a range of global impact studies related to water resources. However, the parameterization of glaciers is often overly simplistic or non-existent in GHMs. The representation of glacier dynamics and evolution, including related products such as glacier runoff, can be improved by relying on dedicated global glacier models (GGMs). Coupling a GGM to a GHM could consequently lead to increased GHM predictive skills, decreased GHM uncertainty, and an increased understanding of the contribution of glaciers to catchment hydrology, particularly in light of climate change.

To test this hypothesis, the GHM PCR-GLOBWB 2 (Sutanudjaja et al., 2018) is coupled with the GGM GloGEM (Huss and Hock, 2015) using eWaterCycle (Hut et al., 2018). For the years 2001-2012, the coupled model is evaluated against the uncoupled benchmark in 25 large (>50.000 km2) glacierized basins using GRDC streamflow observations. Across all basins, the coupled model produces higher runoff throughout the melt season, which can principally be attributed to the underrepresentation of glacial melt in PCR-GLOBWB 2. In highly glaciated basins this difference is pivotal, while in lowly glaciated basins it is negligible. In the evaluation against the GRDC observations, the performance increment of the coupled model at the peak of the melt season in highly glaciated basins stands out.

This study underlines the importance of glacier representation in GHMs and demonstrates the potential of coupling a GHM with a GGM for better glacier representation and runoff predictions in glaciated basins.

 
Improved representation of forest snow processes in coarse-resolution models: lessons learnt from upscaling hyper-resolution simulations
Authors: Mazzotti Giulia , Webster Clare , Essery Richard , Malle Johanna , Jonas Tobias
Published: March 2021

Forest snow cover dynamics affect hydrological regimes, ecosystem processes, and climate feedbacks, and thus need to be captured by model applications that operate across a wide range of spatial scales. At large scales and coarse model resolutions, high spatial variability of the processes shaping forest snow cover evolution creates a major modelling challenge. Variability of canopy-snow interactions is determined by heterogeneous canopy structure and can only be explicitly resolved with hyper-resolution models (<5m).

Here, we address this challenge with model upscaling experiments with the forest snow model FSM2, using hyper-resolution simulations as intermediary between experimental data and coarse-resolution simulations. When run at 2-m resolution, FSM2 is shown to capture the spatial variability of forest snow dynamics with a high level of detail: Its accurate performance is verified at the level of individual energy balance components based on extensive, spatially distributed sub-canopy measurements of micrometeorological and snow variables, obtained with mobile multi-sensor platforms. Results from hyper-resolution simulations over a 150,000 m2 domain are then compared to spatially lumped, coarse-resolution runs, where 50m x 50m grid cells are represented by one model run only. For the spatially lumped simulations, we evaluate alternative upscaling strategies, aiming to explore the representation of forest snow processes at model resolutions coarser than the spatial scales at which these processes vary and interact.

Different upscaling strategies exhibited large discrepancies in simulated (1) distribution of snow water equivalent at peak of winter, and (2) timing of snow disappearance. Our results indicate that detailed canopy structure metrics, as included in hyper-resolution runs, are necessary to capture the spatial variability of forest snow processes even at coarser resolutions. They further demonstrate the relevance of accounting for unresolved sub-grid variability in snowmelt calculations even at relatively small spatial aggregation scales. By identifying important model features, which allow coarse-resolution simulations to approximate spatially averaged results of corresponding hyper-resolution simulations, this work provides recommendations for modelling forest snow processes in medium- to large-scale applications.
Identifying the plasmapause location from global auroral image data
Authors: Mooney Michaela , Forsyth Colin , Marsh Mike , Rae Jonathan
Published: March 2021

Identifying the plasmapause location is crucial for forecasting and modelling the radiation belts, as well as larger scale models of the magnetosphere. The ionospheric footpoints of the plasmapause are thought to map to the equatorward edge of the diffuse aurora, with the first direct observation of an undulation of the plasmapause boundary and corresponding auroral features reported by He et al. (2020). Despite the importance of the plasmapause location, we do not have global observations of the plasmapause location.

We provide a new statistical model of the plasmapause location determined from mapping the equatorward boundary of the observed auroral oval out to the inner magnetosphere. The model uses the equatorward boundary of the auroral oval determined from far-ultraviolet observations from the IMAGE spacecraft from Longden et al. (2010) to provide a statistical estimate of the plasmapause location for different levels of geomagnetic activity. Comparing the results of the statistical plasmapause model to other more direct measurements of the plasmapause shows a good agreement in the nightside local time sectors. 

The results of this analysis show that the equatorward boundary of the auroral oval statistically maps closely to the plasmapause boundary the nightside sectors and provides an alternative use for global auroral image data from the upcoming SMILE mission. 
Complex groundwater flow systems in the light of climate change: response of combined fluid driving forces on recharge reduction
Authors: Trásy-Havril Timea , Szkolnikovics-Simon Szilvia , Mádl-Szőnyi Judit
Published: March 2021

Climate change induced alteration of recharge is expected to have diverse effects on groundwater levels, which could also modify the fragmentation and hierarchy of groundwater flow systems, including their dimensions and relative positions.

This study put emphasis on how flow system hierarchy may change due to recharge reduction in complex, vertically superimposed groundwater flow systems with different fluid driving forces through an example of the Duna-Tisza Interfluve in Hungary. Two main groundwater flow domain was identified by previous authors in this area with a separate source of water. Recharge to the upper, unconfined, gravitational regime is inferred to occur from infiltrating precipitation, while the underlying confined, overpressured flow domain is maintained by pore volume reduction due to tectonic compression of the basement (Tóth and Almási 2001, Almási 2003, Mádl-Szőnyi and Tóth 2009). The exposure of these groundwater flow systems, one is driven by gravity and other one is by overpressure, is completely different to the effects of changes in hydrologic parameters. Local scale gravity-driven flow systems are identified to be the most vulnerable to atmospheric processes (Kurylyk et al., 2014), while overpressured upward flow is driven by tectonic compression, and thus independent of climatic variation.

Two-dimensional transient numerical simulations were performed to gain insight into the response of this complex flow system to the predicted climate change of the region. Special emphasis is placed on i) how relative rate and influence of the different driving forces may change due to the predicted recharge reduction, ii) how the fragmentation of the flow field may alter, iii) how the penetration depth of upper, gravity-driven flow field may adjust to these changes and iv) how groundwater-related shallow surface water bodies will be affected by these changes.

Understanding the effects of changed hydrologic conditions on such complex flow patterns and recharge-discharge relationships as well as on interactions with surface water bodies can help to set-up three-dimensional site-specific models. These models provide a base to better mitigate and prepare for the consequences of predicted future changes.

The research is supported by the ÚNKP-20-4 New National Excellence Program of the Ministry for Innovation and Technology from the source of the National Research, Development and Innovation Fund, as well as by the József and Erzsébet Tóth Endowed Hydrogeology Chair. This work is part of a project that has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 810980.
Interior of an ice stream: 3-D geometry of distorted radar stratigraphy of upstream NEGIS and vicinity.
Authors: Jansen Daniela , Franke Steven , Binder Tobias , Bons Paul , Dahl-Jensen Dorthe , Eisen Olaf , Miller Heinrich , Paden John , Weikusat Ilka
Published: March 2021

The North East Greenland Ice Stream clearly stands out in the surface velocity field of the ice flow of Greenland, with its sharp and narrow shear margins visible in the flow field almost up to the central divide. While the current extent and strength of the streaming can be determined from remotely sensed velocities of the ice surface, it is less known how the ice stream is affecting the deeper layers of ice in its catchment area, and how it may have evolved over time. The deformation of the ice due to streaming can be made visible by mapping the distortion of the isochronous stratigraphy of the ice. This has been done by an airborne radar survey centering on the location of the EGRIP drilling camp, carried out with the ultra wide band  radar system (AWI UWB). The dense grid of profiles arranged mainly perpendicular to the ice flow reveals the imprint that the strong shearing leaves within the layering of the ice. Although the layers are tightly folded and distorted within the shear zones, it is possible to continuously trace reflections within the upper half of the ice column throughout the entire survey area. It can be shown that the intensity of the folding is linked to the strain rate field derived from the surface velocities, and that the deformation history of the ice is preserved in the folded layers, even after it is no longer affected by high strain rates.  The advection patterns of the mapped stratigraphic features reveal how the streaming of the ice and the resulting local changes of surface topography may have affected the inflow into the stream and the position of the shear margins over time.
Multi-sensor approach towards understanding debris-flow activity in the Lattenbach catchment, Austria
Authors: Aigner Philipp , Kuschel Erik , Zangerl Christian , Hübl Johannes , Hrachowitz Markus , Sklar Leonard , Kaitna Roland
Published: March 2021

Debris flows (DFs) pose a severe risk to Alpine communities and infrastructure. The Lattenbach catchment (basin area 5,3 km², relief 2134 m) in Tyrol, Austria, is an example for an active DF-site with several DFs occurring per year. To improve our understanding of the DF-process cascade in this catchment, we raise the questions: where does the sediment originate, are hillslope processes the drivers for DF-activity, and how is the relationship of rainfall amount and DF-magnitude?

We employ an approach that makes use of the data richness of this study site: High resolution ALS and TLS terrain models and aerial photographs are considered to locate significant elevation differences. Furthermore, we performed an in-detail UAV-based surveying campaign of the active channel reaches for the 2019 and 2020 DF-season. Additionally, we use datasets captured by a DF monitoring station (discharge, volume, timing, precipitation) at the catchment outlet to assess triggering rainfall as well as DF-frequency and magnitudes.

We find that in the last fifteen years up to three events occurred annually. A single location, where all DFs originate from, is not detectable, indicating a variety of sediment sources is relevant for DF-initiation, including bank failures and channel incision, partly driven by deep-seated landslides that continuously feed the channel with sediment. Between the years 2005 and 2018 the DF-volumes recorded at the catchment outlet varied between about 5.000 m³ (small) and 46.000 m³ (large). A first analysis suggests that there is a prevailing “background noise“ pattern of relatively small DF-events that happen regularly during every DF-season. We hypothesize that rare, very large events represent a tipping point in the catchment system, which leads to a period of increased large-scale DF-activity over following seasons.
Observations of vertical propagation of near-inertial Waves in a complex vorticity field during the EURAC4A-OA campaign in the tropical western North Atlantic
Authors: Rudloff Daniel , Karstensen Johannes , Fischer Tim , Schütte Florian , Bendinger Arne , Speich Sabrina , L'Hegaret Pierre , Carton Xavier , Reverdin Gilles , Laxenaire Rémi , Gula Jonathan
Published: March 2021

In this study, we investigate the mesoscale flow field and how it enables energy to propagate vertically in form of near-inertial waves. As part of the EURAC4A-OA campaign the research vessels RV Maria S. Merian and NO L’Atalante simultaneously surveyed mesoscale eddy fronts in the western tropical North Atlantic. From velocity profile data, measured by a shipboard Acoustic Doppler Current Profiler (sADCP), we reconstruct eddies in the upper 1000m of the surveyed area, by fitting a Rankine Vortex model. The model derives an idealized velocity structure of the eddy as well as the location of its centre. Multiple occurrences of stacked eddies are identified and often surrounded by current shear structures associated with near-inertial waves. Using data from ship sections, where both research vessels operated less than 1nm apart, the vertical component of the relative vorticity (zeta) is calculated using different methods (single ship, two ships)[Shcherbina et al. 2013]. It is found that in particular zeta outside of the eddy cores is sensitive to the way the vorticity is calculated and may even change sign. Furthermore, the resulting zeta sections and its impact on the ability of near-inertial waves propagating vertically below the mixed layer is discussed.
Sources and Sinks of BVOCs in a Managed Boreal Forest
Authors: Petersen Ross C. , Rinne Janne , Holst Thomas , Mölder Meelis
Published: March 2021

The ecosystem-atmosphere flux of biogenic volatile organic compounds (BVOCs) has important impacts on tropospheric oxidative capacity and the formation of secondary organic aerosols, influencing air quality and climate. In particular, this is true in managed boreal forests in the Northern Hemisphere, where BVOC emissions often dominate over anthropogenic sources of VOC.

Here we present measurements of BVOCs in a managed boreal forest located at the ICOS station Norunda in Sweden, collected using proton transfer reaction mass spectrometry (PTR-MS). This managed forest consists of a mix of Scots pine (Pinus sylvestris) and Norway spruce (Picea abies). These long-term PTR-MS measurements were collected at six heights (4m, 8.5m, 13.5m, 19m, 24.5m, and 33.5m) in the forest canopy over several periods during 2014 to 2016. Ozone concentrations were simultaneously measured in conjunction with these PTR-MS measurements. The main BVOCs investigated with the PTR-MS were isoprene, monoterpenes, methanol, acetaldehyde, and acetone. The distribution of BVOC sources and sinks in the forest canopy was explored using several Lagrangian dispersion matrix methods, including localized and continuous near-field theory. The canopy resistance and deposition velocities for ozone and the BVOCs were investigated, and the results for isoprene and monoterpene emissions were found to agree well with several standard BVOC emission algorithms. These results will have importance for constraining BVOC emission estimates from managed boreal forests in the future.
Geodiversity assessment with Crowdsourced Data and Spatial Multicriteria Analysis
Authors: Najwer Alicja , Jankowski Piotr , Zwoliński Zbigniew , Niesterowicz Jacek
Published: March 2021

The main objective of virtual PICO is to present an approach to geodiversity assessment based on spatial multicriteria analysis (MCE) with Crowdsourced Data. Geodiversity assessment usually involves an individual expert or a group of experts who assess the value of geodiversity factors to the overall geodiversity score for a study area. The biggest objection to methods used so far is subjectivism. Responding to these objections, a crowdsourcing approach that uses an online geo-questionnaire linked with an interactive map was used.

The assessment input data comprised of seven environmental factor ratings and weights were obtained from 57 Earth science researchers worldwide. These data served as the bases for a joint  assessment of geodiversity. To provide more comprehensive assessment approach for aggregating factor ratings and weights to compute an overall measure of geodiversity the weighted linear combination (WLC) method and its local version L-WLC were used. Karkonosze National Park (KNP) located in south-western Poland in the border area between Poland and the Czech Republic was chosen as a research area. Karkonosze is the highest mountain range of the Sudetes, characterised by unique geological and geomorphological values. The geodiversity of the research area was valued with regards to the reliability of assessment evaluated by means of spatially explicit uncertainty analysis. Average (AVG) and standard deviation (STD) geodiversity maps (on the basis of 57 respondent data) were computed. As a result of their cross-tabulation, a bivariate maps with average geodiversity values (AVG: low, high) and standard deviation values (STD: low, high) were created. Two such maps, one for WLC results and another for L-WLC results, were compiled and evaluated, providing a more holistic visages of final geodiversity and its uncertainty. Given that L-WLC provides a realistic assessment of geodiversity and guided by its results, the areas of  high geodiversity and low uncertainty have been identified within Karkonosze range.
Large-Eddy Simulation in LSPIV techniques: the study of surface turbolence
Authors: Alongi Francesco , Ciraolo Giuseppe , Napoli Enrico , Pumo Dario , Noto Leonardo V.
Published: March 2021

In recent years, technological advances have been observed in environmental monitoring field, leading to a rapid spread of innovative technologies overcoming many historical challenges. In river monitoring field the use of image-based techniques provides non-intrusive measurements ensuring the best safety conditions for operators. The most used optical methods are the Large-Scale Particle Image Velocimetry (LSPIV) and the Large-Scale Particle Tracking Velocimetry (LSPTV).

In LSPIV and LSPTV techniques a floating tracer is introduced on the water surface and its motion is recorded by commercial devices (e.g. digital cameras). Resulting videos are then processed by free and open source software which applies a statistical cross-correlation analysis to provide the instantaneous surface velocity field.

The aim of this work is to investigate the performance of the most widely used LSPIV software in estimating the surface velocity field taking into account the presence of turbulent structures. Indeed a typical feature of natural river is the presence of turbulent eddies which makes the tracer patterns above the water surface difficult to predict. The evaluation of tracer particle displacement is further complicated by the negative phenomenon of aggregation; it influences cross-correlation causing an incorrect estimation of the velocity vectors.

The study of the hydraulic turbulence of a natural river has been tackled from a numerical point of view. PANORMUS (Parallel Numerical Open-Source Model for Unsteady Flow Simulations) package (Napoli, 2011) has been used by adopting a LES (Large Eddy Simulation) scheme. PANORMUS is a numerical tool coded to solve the 3D momentum equations for incompressible flows (Navier-Stokes and Reynolds equations) using the Finite-Volume Method (FVM). The analyses were carried out on real cases modelled with PANORMUS-LES package. The hydraulic reconstructed domains are characterised by regular cross sections, accurately derived from real topographic survey campaigns, and low river-bed roughness (smooth concrete surface).

Synthetic sequences of tracer motion were derived from the hydraulic model and then processed by using LSPIV software.

The results of such numerical analyses have allowed an evaluation of LSPIV performance assessing the errors in terms of mean value of the surface velocity field and velocity along transverse transects.
Modes of variability in the Tropical Atlantic and its influences on the precipitation regime in Brazil
Authors: Cardoso Andressa , Wainer Ilana
Published: March 2021

Tropical Atlantic variability modes can influence atmospheric circulation impacting the precipitation regimes over South American and the intensity of the meteorological systems associated. The objective of this work was to analyse the centennial variability and trends of the zonal and meridional modes in the Tropical Atlantic Ocean and their influences in the precipitation, focusing on the North and Northeast of Brazil. The zonal mode was estimated using the ATL3 index, calculated by the monthly sea surface temperature anomaly (SSTa) within 3ºS-3º N and 20ºW-0.  The AMM index represents the meridional mode and was obtained by the difference of the monthly SSTa between the North (5-20ºN and 60ºW-10ºE) and South (20ºS-5ºN and 60ºW-10ºE) Atlantic.  The indices were calculated for three reanalyses, NOAA ERSST v4, ERA20C and ERA-Interim, and compared to the observational dataset OISSTV2 using correlation for the 1982-2010 period. The results showed a positive trend in both indices considering the period of 1900-2010 for the two centennial reanalyses (NOAA ERSST v4 and ERA20C). However, the trend is higher for the ATL3 index and lower for the AMM considering the NOAA reanalysis. The monthly precipitation was also used to analyse the relationship between the indices and precipitation pattern. The correlation between ATL3 and AMM and the precipitation field using the NOAA reanalysis showed that ATL3 positively influences rain over northeastern Brazil, throughout the Tropical South Atlantic, and northwestern Africa between 1900 and 2010. The opposite is observed relative to AMM, once anomalies of negative (positive) precipitation in the Southern (Northern) Hemisphere are related to a positive SSTa in the region. These results may be related to the most intense SSTa in the northern tropical Atlantic, which shifts the ITCZ, promoting more precipitation further north, and favors the hurricane season All reanalyses represented the indices in agreement with observations, however, the statistical parameters were better for with the ERA-Interim. A possible reason is that ERA-Interim is a newer reanalysis, with more observed assimilated data. Moreover, it has a finer resolution when compared to the other datasets, which contributes to a better representation of the precipitation patterns.  In conclusion, ATL3 positively influences precipitation in the North and Northeast Brazilian regions, as the warmer SST drives the position of the ITCZ. Therefore, the observed increasing trend in the precipitation over this region over the past years was associated with the increase in SSTa over the Tropical Atlantic, which may favor precipitation in the north and northeast of Brazil.
Network properties as functional traits for fungi
Authors: Aguilar-Trigueros Carlos , Fricker Mark , Rillig Matthias
Published: March 2021

Fungal mycelia consist of an interconnected network of filamentous hyphae and represent the dominant phase of the lifecycle in all major fungal phyla, from basal to more recent clades. Indeed, the ecological success of fungi on land is partly due to such filamentous network growth. Nevertheless, fungal ecologists rarely use network features as functional traits. Given the widespread occurrence of this body type, we hypothesized that interspecific variation in network features may reflect both phylogenetic affiliation and distinct ecological strategies among species. We show first that there is high interspecific variation in network parameters of fungi, which partly correlates with taxonomy; and second that network parameters, related to predicted-mycelial transport mechanisms during the exploration phase, reveal the trait space in mycelium architecture across species.  This space predicts a continuum of ecological strategies along two extremes: from highly connected mycelia with high resilience to damage but limited transport efficiency, to poorly connected mycelia with low resilience but high transport efficiency. We argue that mycelial networks are potentially a rich source of information to inform functional trait analysis in fungi, but we also note the challenges in establishing common principles and processing pipelines that are required to facilitate widespread use of network properties as functional traits in fungal ecology.
Sounding plasma turbulence at sub-ion scales with Fast Iterative Filtering in space and time.
Authors: Papini Emanuele , Cicone Antonio , Franci Luca , Piersanti Mirko , Landi Simone , Verdini Andrea , Hellinger Petr
Published: March 2021

We present the results from a spacetime study of Hall-MHD and Hybrid-kinetic numerical simulations of decaying turbulence. By combining Fourier analysis and Multivariate Iterative Filtering (a new technique developed for the analysis of nonstationary nonlinear signals) we calculate the kω-power spectrum of magnetic, velocity, and density fluctuations at the maximum of turbulent activity. Results show that the magnetic power spectrum at sub-ion scales is formed by localized structures and/or perturbations with temporal frequencies much smaller than the ion-cyclotron frequency Ωi. Going toward smaller ion-kinetic scales, the contribution of low-medium frequency perturbations (ω < 3Ωi) to the magnetic spectrum becomes important. Our analysis clearly indicates that such low-frequency perturbations have no kinetic-Alfvén neither Ion-cyclotron origin. At higher frequencies, we clearly identify signatures of both whistler and kinetic-Alfvén wave activity. However, their energetic contribution to the turbulent cascade is negligible. We conclude that the dynamics of turbulence at sub-ion scales is mainly shaped by localized intermittent structures, with no contribution of wavelike perturbations.
Management legacies and forest structure shape the root rot risk of coniferous forests in Finland
Authors: Honkaniemi Juha , Heikkinen Juha , Henttonen Helena , Peltoniemi Mikko
Published: March 2021

Forest management and land use can strongly alter the forest ecosystem with long-lasting legacy effects by shaping e.g. species composition and age structure in stand and landscape scales. These changes may lead to changes in the local disturbance regime. In addition, forest management may directly affect the dynamics of disturbance agents. Heterobasidion root rot is one of the most important diseases of conifers in the Northern hemisphere. The epidemiology of the fungus relies heavily on the availability of fresh wood material which the spores need to cause an infection. In managed forests, fresh stump surfaces provide massive amounts of perfect growth media.  Once the fungus has infected a stand, the disease remains in there over tree generations slowly deteriorating the timber quality, killing trees and predisposing trees to subsequent disturbance agents such as wind. Thus, host availability in landscape scale, stand conditions and the management history all are assumed to play an important role in the epidemiology. The aim of this study was to analyze the drivers of current distribution of Heterobasidion root rot in Finland in order to understand the disease dynamics better and to manage the disease in the future. Specifically, we asked how important the legacies of different past management and land-use methods are. The National Forest Inventory (NFI) in Finland has recorded root rot observations since 1995 covering in total over 348 000 sample plots over four inventories. We combined that database with 20 different explanatory variables with a hypothetical relation to the biology and epidemiology of the fungus. The variables were categorized to three categories; (i) management legacies, (ii) landscape structure, and (iii) site conditions. Management legacies included for example the historical locations of sawmills and the share of forest pastures. Landscape structure combined structural characteristics, such as Norway spruce and old forest (120+ years) shares from different time periods. Site conditions were described with e.g. temperature sum and Shannon index for tree species richness. By using Boosted Regression Tree and Generalized Liner Models, we found that variables from all the three categories contributed to the presence of Heterobasidion root rot. The distance from an NFI plot to the nearest sawmill operating in 1910 (historical intensity of logging) and the distance to a waterway (timber rafting as main transportation methods) were shown to be one of the most important variables together with temperature sum and current Norway spruce share in landscape scale. This indicates that the management legacies, especially the past management intensity, has a significant effect on the epidemiology of Heterobasidion root rot.
The spatio-temporal evolution of groundwater dependent precipitation
Authors: Passet Cristina , Wang-Erlandsson Lan , Wada Yoshihide , Pranindita Agnes , De Boer Agatha
Published: March 2021

A substantial portion of groundwater abstracted from aquifers is used for irrigation and evaporated to the atmosphere, potentially contributing towards downwind precipitation. While the fate of evaporation fluxes from land have been analysed, the atmospheric pathways of evaporation originating from groundwater have not yet been globally quantified. This study analysed the geographical distribution, the seasonality and the magnitude of groundwater-dependent precipitation (Pgw) at a global scale and for a selection of countries and river basins. The Eulerian moisture tracking WAM-2layers model was used to process meteorological and groundwater abstraction input data from 1980 to 2010.  Results show considerable contributions of groundwater to precipitation downwind of the most heavily irrigated areas, leading to net groundwater losses over these areas. Globally, 40% of the Pgw precipitates directly in the oceans, and do not contribute to biomass production in terrestrial ecosystems. Some of the countries with the highest rates of groundwater abstraction (India, the USA, Pakistan and Iran), receive low volumes of Pgw and are net losers of groundwater resources. The countries with the highest net gain of groundwater are China, Canada and Russia. At river basin scale, the Indus, Ganges and Mississippi basins are net losers of groundwater to downwind Pgw, while the Yangtze, Tarim and Brahmaputra basins receive more Pgw than their groundwater withdrawals. The share of precipitation that originates from groundwater varies considerably with seasons, and can be especially high when low local precipitation levels occur in combination with high upwind groundwater abstraction. Furthermore, precipitation dependence on groundwater (ρgw), has steadily increased between 1980 to 2010 in all studied areas and globally. Our study suggests that the countries and basins with a high and increasing dependency on ρgw to support their precipitation can be vulnerable to groundwater availability upwind.
Downward particle flux in the open ocean: Future global opportunities and insights from time-series measurements at the PAP Sustained Observatory in the Northeast Atlantic.
Authors: Lampitt Richard
Published: March 2021

The Joint Global Ocean Flux Study (JGOFS) started in 1987 and stimulated massive integration of efforts to measure and understand the processes of downward flux in the ocean. A small number of sustained observatories have persisted from this time in the belief that a key to gaining this understanding is by prolonged time-series observations. The sustained observatory over the Porcupine Abyssal Plain (PAP-SO) in the Northeast Atlantic is one such site which has provided nearly continuous measurements of downward flux at a depth of 3000m since 1989. This was using sediment traps but, in order to understand the data, we have exploited a wide range of other approaches such as optical methods, drifting sediment traps in the upper 1000m, chemical variables near the surface and computational modelling. Insights are also gained from the Continuous Plankton Recorder (CPR), satellite observations and various climatic indices.

This presentation draws together these measurements to quantify and understand flux at 3000m. Seasonal and interannual variability is large but after 30 years of observation, explanations are now possible. In addition, some of the conclusions identify major and surprising features about the ways ecosystems in one year may be influenced by their structure and function in previous years.

At the same time as these time-series observations have been in progress, major new developments have taken place globally and at PAP-SO to provide additional and alternative means to asses flux. The sediment trap has significant advantages as well as uncertainties which have been described previously. The new era of approaches using, for instance, BGC Argo, the Carbon Flux Explorer and a variety of other optical techniques offer what may be a quantum leap in our understanding of downward particle flux now and how it is changing in response to changes in the global climate. This presentation will give a personal and optimistic view of the opportunities which are now developing to quantify and understand this crucially important process.
Improved predictability of numerical flow models of fractured crystalline media: The effect of surface roughness.
Authors: Cardenas Rivera Maria Alejandra , Kulenkampff Johannes , Jankovsky Filip , Havlova Vaclava
Published: March 2021

Transport and flow through fractured crystalline rocks is an important and often studied topic in the context of nuclear waste disposal, given that the heterogeneity of fluid transport constraints the efficiency of radionuclide sorption processes. In past years, several studies have provided numerical simulations of the flow rate that can be expected in different types of fractures. Such studies rely on the required length-scale and spatial resolution of geometrical data in order to conduct flow and transport modeling. The numerical results are validated against tracer data of break-through experiments, such as the recently available spatiotemporal tracer concentration analysis, obtained from positron emission tomography (PET) . In many cases, however, the results obtained from the numerical simulations differ greatly from the experimental observations. While some numerical models commonly operate under the cubic law assumption, which defines a fracture as two perfectly parallel smooth surfaces, more advanced simulations include the effect of fracture surface roughness. Such results suggest the need of an improved understanding of transport heterogeneities as a function of fracture surface roughness and topography. Moreover, a systematic evaluation provides insight into the model complexity required for reliable radionuclide transport and flow predictability in potential host rocks.

In this study, we focus on the numerical modeling of flow through a fracture while taking into account surface roughness of the fracture walls, and validating the results against tomographic methods. For this purpose, the structural parametrization of the fracture is carried out by performing the segmentation of micro-computed tomography (µCT) images obtained from Granite samples from the Mrákotín quarry  in the Czech Republic. Subsequently, interferometry measurements of identical fracture material are carried out in order to quantify the details in the surface topography at the nm to µm scale. Resulting data are combined with µCT data through statistical methods, which provide a more meaningful definition of the surface topography, and are compared with numerically generated surface roughness. Resulting numerical simulations are then validated against PET measurements. As a result from the outlined workflow and the quantitative comparison, we provide suggestions of general applicability of the required degree of complexity for surface geometry segmentation in flow simulations.
Analysis and Monitoring atmospheric gases in a high performing and versatile isotope ratio instrument
Authors: Barker Sam , Hackett Phil , Price Will , Rosenthal Kathrin
Published: March 2021

Biogenic gases carbon dioxide, methane and nitrous oxide are regularly analysed in many environments to understand elemental cycling and processes through the ecosphere. They are also of interest to atmospheric chemists for their role in climate change.  The Isoprime Tracegas has been key to a large amount of studies providing data on the isotopes of these key dynamic molecules. We shall review some of the notable publications and modifications in the field of atmospheric gas monitoring.

The development of the isoprime precisION mass spectrometer has permitted a new generation of control and automation of the mass spectrometer and integrated peripherals. This has greatly improved the accessibility and versatility of the instruments as a whole.

Taking advantage of the inherent benefits of the isoprime precisION the iso FLOW GHG has been developed for high performance analysis of CO2, N2O and CH4 and has the capacity to be rapidly customised for specific needs with options for N2 and N2O, Hydrogen isotopes in CH4 and denitrifier analysis.
Challenges in the development of the geodiversity concept
Authors: Brilha José
Published: March 2021

The concept of geodiversity, despite being in use for almost 30 years, still has little impact on society. It is not easy to explain the reason for this dissociation, considering that the elements that constitute geodiversity are intrinsically part of nature, play an essential role in ecosystem services and, consequently, in human well-being.

During the last decade we have seen a great development in the interest of the geoscientific community in this subject, represented by the increase in the publication of papers and doctoral and master theses all over the world. One of the main challenges is now to transpose all this scientific knowledge into society. Obviously, theoretical and conceptual discussions about geodiversity are an integral part of science and must continue, but if we want that society recognizes the importance and value of geodiversity, we must be able to demonstrate clearly how geodiversity can help to solve some of the problems we face today.

Among other priorities, the geoscientific community has to be able to demonstrate in an structured way:

The importance of geodiversity in implementing nature conservation actions and its direct relationship with biodiversity;

The contribution of geodiversity for ecosystems restoration and its accounting as part of natural capital;

The need to quantify the role of geodiversity in ecosystem services;

The urgency of make environmental impact assessments including all possible effects that may affect geodiversity elements and processes;

The importance of integrate the concept of geodiversity in pre-university education curricula;

That the information and environmental interpretation provided to visitors of protected areas and other conservation areas should always include geodiversity.

Once the importance of geodiversity is fully recognized by policy-makers, managers, and the society in general, the fulfilment of the UN Sustainable Development Goals will be for sure closer than it is today.
The Quasi-Liquid Layer on ice observed with NEXAFS
Authors: Gabathuler Jérôme , Manoharan Yanisha , Yang Huanyu , Boucly Anthony , Artiglia Luca , Ammann Markus , Bartels-Rausch Thorsten
Published: March 2021

The Quasi-Liquid Layer on ice observed with NEXAFS

Gabathuler, Y. Manoharan, H. Yang, A. Boucly, A. Luca, M. Ammann, T. Bartels-Rausch

Paul Scherrer Institute, Villigen, Switzerland

 

 

As temperature approaches the melting point of ice from below, the hydrogen-bonding network at the air – ice interface evolves from a well-defined hexagonal structure towards more randomly spatialized interactions. The general agreement is that a Quasi-Liquid-Layer (QLL) exists at the surface of the ice, and reports on the thickness of this disordered interfacial layer range from 2 nm to 25 nm at 271 K, depending on the probing technique (atomic force microscopy (AFM), ellipsometry, optical reflectivity, sum-frequency generation (SFG)) [1]. These large differences partly arise from the fact that the different techniques are probing different properties of the interface, and the delicate calibration into the thickness of the QLL contributes greatly to the uncertainty.

 

We investigate the QLL using Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy, as Bluhm and his group did in 2002 [2]. The technique probes Auger electrons emitted upon X-ray absorption, thus, NEXAFS becomes inherently sensitive to the upper few nm of the air-ice interfacial region. This work focuses on the probing depth associated with this method and proposes a comprehensive treatment of the data, to help resolve the discrepancy of current thickness data. The importance of the QLL’s thickness comes from its contribution to environmental science as a reservoir for chemical impurities and as a host of chemical reactions with an impact on atmospheric and cryospheric composition.

 

We will present a first data set of NEXAFS from neat ice between – 40 °C and 0°C acquired at the ISS endstation at the Swiss Light Source of the Paul Scherrer Institute. Results including error bars will be compared to earlier studies. The preliminary analysis suggests that the interfacial disorder seems to be less pronounced than reported in many earlier studies, very much in agreement with recent SFG [3] and AFM data [4].

 

 

 

Literature References:

 

 

Acknowledgment:

We thank A. Laso for technical help, SNF for funding (grant 178962)

 
O3 responses in CMIP6 AerChemMIP experiments: different roles of O3 precursors, CH4 concentrations and climate change
Authors: Liu Zhenze , M. Doherty Ruth , Wild Oliver , M. O’Connor Fiona , T. Turnock Steven
Published: March 2021

A new version of the UKCA chemistry-climate model with highly reactive volatile organic compounds (VOCs) is used to investigate the ozone (O3) responses in historical (2004-2014) and future (2045-2055) shared socio-economic pathways (SSPs) scenarios of CMIP6 AerChemMIP experiments. Significant increases in surface O3 levels in South and East Asia are simulated in the new version compared with the standard UKCA model. The O3 production and the O3 burden averaged over the troposphere increase slightly by 6 % as a result of more highly reactive VOCs, but the O3 lifetime is quite similar. Comparing the different SSP scenarios using this new model version we find the averaged surface O3 concentrations are higher in the scenario with high emissions than for historical conditions. O3 concentrations are much lower than historical O3 concentrations when O3 precursor concentrations are low. However, regional O3 increases occur in East Asia in the future scenario with low emissions of short-lived climate forcers due to strong VOC limited regimes. Decreases in surface O3 concentrations occur globally in the future scenario that has lower methane (CH4) concentrations. We construct O3 and O3 production isopleths. These both suggest that the threshold of NOx/VOCs shifting from NOx limited to VOC limited regimes is approximately 0.8. More areas become VOC limited in South Asia in all future scenarios, but there is little change for East Asia. The hydroxyl radical (OH) concentrations generally increase in regions with high O3 precursor abundances in the future scenario, but the high OH levels are offset by lower CH4 concentrations in the future low CH4 scenario. We find that there are small changes in O3 production efficiency in continental regions in all future scenarios. Relative O3 burden changes between the future SSP and historical scenarios are larger in the troposphere than in the planetary boundary layer (PBL), illustrating that O3 burdens are less sensitive in the PBL under emission and climate change. The O3 lifetime in the troposphere decreases in all future scenarios as compared to the historical period. We find that the decreases in O3 precursors and CH4 concentrations play important roles in reducing O3 burdens in the future.