bluuebunny/crossref_metadata_2025 huggingface dataset:
Complex landslide dynamics: establishing a monitoring setup to investigate sub-surface properties and displacements of a slow moving landslide system
Authors: Stumvoll Margherita J. , Fahrngruber Robert , Glade Thomas
Published: March 2020

Quantitative data of the sub-surface properties and dynamics of recently active landslides spanning a temporal scale of more than a few years are still fairly rare. This is due to the fact that long-term landslide-monitoring setups are expensive regarding both financial and human resources as well as to install and maintain. Yet, a comprehensive understanding of potential landslide triggering thresholds is mandatory.
Apart from external triggers the internal hydrological, soil mechanical and geophysical properties of a hillslope determine its potential for displacement. The spatial distribution of groundwater levels and soil water contents as well as of the regolith material, resistance and depth define potential areas of activity. The internal structure of a landslide needs to be assessed in order to be able to evaluate magnitude and frequency as well as potential triggers of activity.

In this study, we present a long-term monitoring setup for the detection of sub-surface properties, structure and dynamics of the complex Hofermühle-landslide near Konradsheim in Lower Austria. A combination of direct (invasive) and indirect (non-invasive) methods is used. Direct methods include 1) dynamic probing to investigate sub-surface resistance and 2) the analysis of cores generated via drilling. Data analysis hereby focus on geotechnical parameters such as soil properties, regolith depth and resistance. To investigate hydrological properties data regarding 3) groundwater level using piezometers as well as 4) soil moisture using time domain reflectometry (TDR) probes are used. Data analysis focus on the spatio-temporal behaviour of soil moisture and groundwater level changes in order to assess sub-surface water pathways, water residence time and the connection to changes – regarding both input (precipitation) and output (evapotranspiration). Sub-surface movement rates and their position along vertical soil profiles are planned to be analysed using 5) inclinometer data. Direct methods are combined with non-invasive geophysical methods. As this monitoring setup will be maintained for a longer time period (>10a), the setup itself is assessed critically; challenges and issues of the installation, data transfer and analysis are discussed.

First results regarding the analysis of hydrological parameters indicate a heterogenic distribution of groundwater static level, soil water retention time after infiltration and flow paths. A first interpretation of the sediment core, dynamic probing as well as geophysical results support this heterogeneity. Sub-surface areas of potential activity could be presumed to be correlated with the spatial distribution of surface displacements as these also show a heterogenic distribution.
Decomposing the geomagnetic field: oscillation modes and characteristics
Authors: Stefan Cristiana , Dobrica Venera , Demetrescu Crisan
Published: March 2020

Using the COV-OBS.x1 (Gillet et al., 2015) main geomagnetic field model, covering the time span 1840–2020, respectively IGRF-13 (1900-2020), we decomposed the geomagnetic field at Earth’s surface in oscillation modes by means of empirical orthogonal functions (EOF) as well into a long term and a cyclic component using HP filtering (Hodrick and Prescott, 1997). Further, the long term component is filtered using a Butterworth filter (1930) with different cut-off periods in order to obtain oscillation at inter-centennial (> 100 years) and sub-centennial (60-90 years) timescales. The EOF analysis shows that the first three oscillation modes are characterized by periodicities of >100 years while modes 4 and 5 are characterized by dominant periodicities of 70-90 year. Although the variance of the modes 4 and 5 is rather small compared to that of the first three modes, these two modes are responsible for the detailed structure of the geomagnetic field. A comparison between the results of both methods is done as well.
Non-destructive method based on infrared spectroscopy and partial least square regression for the quantification of the ionic component of atmospheric particulate matter
Authors: Molteni Ugo , Piazzalunga Andrea , Fermo Paola
Published: March 2020

Atmospheric aerosols influence radiative forcing through interaction with solar radiation and indirectly by acting as cloud condensation nuclei and have a negative impact on air quality especially in urban scenarios. With socio-economic models suggesting that in a growing global population, 70% of the humans will live in urban areas by 2050, the adverse impact on urban air quality is a prominent societal and health issue, expected to become more and more severe in the future. In order to introduce effective mitigation strategies and monitor their effect, the state and characteristics of pollution need to be characterized and main sources identified. Offline-analysis of particulate matter (PM) collected on filter samples offers such insight. However, PM chemical composition is highly complex, and its comprehensive characterization and quantification requires advanced instrumentation and data analysis techniques and strategies.

Here, we present the development and application of a novel analytical nondestructive method. We acquired Fourier-transform infrared spectroscopy (FTIR) spectra of ambient PM collected on Teflon filters at various locations in Italy. FTIR allows to obtain high-resolution spectral data non-destructively and therefore to detect and quantify functional groups of organic and inorganic species present in the aerosol PM. The spectral dataset was analyzed by applying partial least squares regression (PLS regression) methods in order to allow quantification of ammonium, sulphate and nitrate ionic PM components. This statistical method allowed to disentangle the inner complexity of the PM sample and to train a statistical model for each of the three ionic species. In our conference contribution, the so developed models are discussed and compared with the more traditional analytical method, ionic chromatography (IC).

 

References:

Cuccia, et al. (2011). Atmospheric Environment, 45(35), 6481–6487. https://doi.org/10.1016/j.atmosenv.2011.08.004

Piazzalunga, A., et al. (2013). Analytical and Bioanalytical Chemistry, 405(2–3), 1123–1132. https://doi.org/10.1007/s00216-012-6433-5

Russell, L. M., et al. (2009). Atmospheric Environment, 43(38), 6100–6105. https://doi.org/10.1016/j.atmosenv.2009.09.036
Natural and anthropogenic methane emissions in West Siberia estimated using a wetland inventory, GOSAT and a regional tower network
Authors: Maksyutov Shamil , Sasakawa Motoki , Janardanan Rajesh , Wang Fenjuan , Tsuruta Aki , Terentieva Irina , Sabrekov Alexander , Glagolev Mikhail , Machida Toshinobu , Arshinov Mikhail , Davydov Denis , Krasnov Oleg , Belan Boris , Dlugokencky Ed , Lavric Jost V. , Ito Akihiko , Janssens-Maenhout Greet , Kaiser Johannes , Yoshida Yukio , Matsunaga Tsuneo
Published: March 2020

West Siberia contributes a large fraction of Russian methane emissions, with both natural emissions from peatlands and anthropogenic emissions by oil and gas industries. To quantify anthropogenic emissions with atmospheric observations and inventories, we must better understand the natural wetland emissions.  We combine high-resolution wetland mapping based on Landsat data for whole West Siberian lowland with a database of in situ flux measurements to derive bottom-up wetland emission estimates. We use a global high-resolution methane flux inversion based on a Lagrangian-Eulerian coupled tracer transport model to estimate methane emissions in West Siberia using atmospheric methane data collected at the Siberian GHG monitoring network JR-STATION, ZOTTO, data by the global in situ network and GOSAT satellite observations. High-resolution prior fluxes were prepared for anthropogenic emissions (EDGAR), biomass burning (GFAS), and wetlands (VISIT). A global high-resolution wetland emission dataset was constructed using 0.5-degree monthly emission data simulated by the VISIT model and wetland area fraction map by the Global Lake and Wetlands Database (GLWD). We estimate biweekly flux corrections to prior flux fields for 2010 to 2015. The inverse model optimizes corrections to two categories of fluxes: anthropogenic and natural (wetlands). Based on fitting the model simulations to the observations, the inverse model provides upward corrections to West Siberian anthropogenic emissions in winter and wetland emissions in summer. The use of high-resolution atmospheric transport in the flux inversion, when compared to low-resolution transport modeling, enables a better fit to observations in winter, when anthropogenic emissions dominate variability of the near-surface methane concentration. We estimate 15% higher anthropogenic emissions than EDGAR v.4.3.2 inventory for whole Russia, with most of the correction attributed to West Siberia and the European part of Russia. Comparison of the inversion estimates with the bottom-up wetland emission inventory for West Siberia suggests a need to adjust the wetland emissions to match observed north-south gradient of emissions with higher emissions in the southern taiga zone.
The seasonal cycle of biogenic ice-nucleating particles in a boreal forest environment
Authors: Schneider Julia , Höhler Kristina , Heikkilä Paavo , Keskinen Jorma , Bertozzi Barbara , Schorr Tobias , Umo Nsikanabasi , Vogel Franziska , Brasseur Zoé , Wu Yusheng , Hakala Simo , Duplissy Jonathan , Petäjä Tuukka , Adams Michael P. , Murray Benjamin J. , Korhonen Kimmo , Thomson Erik S. , Castarède Dimitri , Leisner Thomas , Möhler Ottmar
Published: March 2020

By triggering the formation of cloud ice crystals in the atmosphere, ice-nucleating particles (INP) strongly influence cloud properties, cloud life cycle and precipitation. Describing the abundance of atmospheric INPs in weather forecasts and climate projections remains challenging, as the global distribution and variability of INPs depend on a variety of different aerosol types and sources. Although widespread field measurements have been conducted, neither short-term variability nor long-term seasonal cycles have yet been well characterized by continuous measurements. In 2018, the University of Helsinki and the Karlsruhe Institute of Technology (KIT) initiated a field campaign HyICE to perform comprehensive long-term INP measurements in the Finnish boreal forest. The campaign took place in Hyytiälä, Southern Finland at the University of Helsinki SMEARII research station (Hari and Kulmala, 2005). KIT provided the INSEKT (Ice Nucleation Spectrometer of the Karlsruhe Institute of Technology) to analyse the INP content of ambient aerosols sampled on filters. INSEKT is able to measure INP concentrations in the immersion-freezing mode at temperatures between 273 K and 248 K. The measurements started in March 2018 and ended in May 2019, which provides a unique continuous long-term time series of INP concentrations for over more than one year with a time resolution of about one to three days. This long-term observation record is used to examine systematic seasonal trends in the INP concentrations and to find meteorological and aerosol related parameters to describe the observed trends and variabilities. These findings will enable to find new parameterizations of atmospheric INP concentrations, as current parameterizations do not reproduce the observed seasonal cycle yet. In addition to INP concentration measurements, heat treatment tests of the aerosol samples have been conducted providing additional indications about the INP types dominating the INP population in the boreal forest, also in dependence on the season. Finally, this contribution will summarize and discuss major findings and implications from the HyICE long-term INP observation.

 

Hari and Kulmala (2005), Boreal Environ Res. 14, 315-322.
Variation in hydrogen stable isotopes in cellulose and n-alkanes: phylogenetic signal and related traits
Authors: Baan Jochem , Holloway-Phillips Meisha , Kahmen Ansgar
Published: March 2020

Hydrogen (H) stable isotope analysis of specific plant organic compounds has become of interest as a tool for ecological, environmental and palaeoclimatological studies. Aside from the influence of leaf water evaporative enrichment on the δ2H composition of organic compounds, hydrogen isotope fractionation occurs during carbon metabolism in the plant (εbio). To get a better understanding of the metabolic signal recorded in εbio, we explored the variation of δ2H in cellulose and n-alkanes, and its relationship with phylogeny and other plant traits. Leaf material of a large set of species in the eudicot clade was collected in the botanical garden at the University of Basel, cellulose and n-alkanes were extracted, δ2H in both compounds and δ18O in cellulose were analysed. It was found that modelled leaf water differences only explain part of the observed variation of δ2H in organic compounds. δ2H appears to be related to phylogeny and a wider assessment of trait data is currently being undertaken to test for signal associations with physiological traits. This study helps address at which taxonomic level the variation of δ2H is found; illuminate plant physiological traits that can be responsible for shaping species specific δ2H values in organic compounds; as well as, provide novel insights into the δ2H covariation between cellulose and n-alkanes.
Particle-In-Cell simulations of magnetic reconnection in the presence of a cold shear flow
Authors: Flø Spinnangr Susanne , Tenfjord Paul , Hesse Michael , Norgren Cecilia , Kwagala Norah
Published: March 2020

Our group has done extensive research on the fluid and kinetic effect of cold ion populations on the reconnection process, in an effort to identify factors that can lead to the onset or stopping of magnetic reconnection. Recent fully kinetic studies involving cold protons or oxygen have shown that flows of cold particles significantly modify the reconnection process, and that the nature of this modification is dependent on the configuration of these flows and the constituent ions of the flows. In this study we want to investigate how the reconnection process is affected by a shear flow of cold protons outside of the current sheet, using a 2.5D Particle-In-Cell simulation. The effect of shear flows on magnetic reconnection has investigated earlier, indicating a signifficant modification of the reconnection process. However, it is not clear how these effects will be influenced by the additional scale lengths introduced into the system by a cold ion flow. In particular we want to investigate how the current sheet and diffusion regions are altered by a cold shear flow on a kinetic level, and how the reconnection process is altered on ion scales and beyond. Preliminary results indicate that the shear flow introduces a tilt of the current sheet, which appears to be consistent with earlier studies. Results will be compared to our group’s earlier results involving symmetric and asymmetric flows of cold particles in the inflow regions, as well as existing simulations and observations of magnetic reconnection including warm shear flows.
Towards a staggered-grid finite difference code for modelling magmatic systems
Authors: Berlie Nicolas , Kaus Boris , Popov Anton , Sanan Patrick
Published: March 2020

The in-depth behaviour of magmatic systems is still poorly constrained due to their lack of accessibility and the difficulty of finding good analogue representations. However, progresses in the field of geological numerical modelling can allow to better understand and interpret those constraints. The MAGMA project aims on developing tools and software for studying a range of magmatic processes in the lithosphere. On the way to building a general framework able to model the behaviour of a fluid-solid chemically coupled magmatic system, we present here the current development of a mechanical staggered-grid finite difference 2D code using robust analytical linear and non-linear solvers via the PETSc infrastructure, able to run in parallel on highly performant computers. The mesh is assembled using the recently developed DMStag framework, which is part of PETSc. This code solves the Stokes equations for elasto-visco-plastic rheologies, including tensile plasticity essential to the development of dyke structures. Here, we will present the equations and implementations used, and show initial results and benchmarks.
CrowdSlide – a mobile web application for building a database of gravitational mass movements using volunteer field reports
Authors: Schlegel Jona , Grass Annemarie , Fuchs Florian
Published: March 2020

Gravitational mass movements like rockfalls or landslides pose a sincere threat to human population and infrastructure in particular in densely populated alpine regions such as the European Alps. Comprehensive identification of such events is challenging since they may occur spontaneously and at previously unknown places in remote areas. Small mass movements in remote areas may even completely evade our attention. Remote sensing surveys may also miss small-scale events in unfavorable conditions such as e.g. high-altitude rocky landscapes. However, comprehensive knowledge and reliable event data are of particular importance for the assessment of hazards imposed by rapid gravitational mass movements.

Consequently it is highly desired to expand our event databases and be open to new ways of data collection. We suggest that hikers and other enthusiasts can contribute to building a scientific database of gravitational mass movements by reporting events they witness or discover in the field. We developed a prototype of a mobile web application that allows anyone to report mass movements and to attach photographs and crucial event information such as location and time. Additional features may be implemented in the future, such as retrieving event information from social media posts. Future versions may also teach enthusiasts to characterize mass movements (e.g. type, volume) so they can contribute valuable information themselves. Ultimately, we are envisioning to form a citizen science community of interested enthusiasts that jointly create a valuable scientific database.
Effects of Salt Precipitation on Evaporation Rate in Porous Media
Authors: Karatas Tuna
Published: March 2020

Salts in porous rocks are destructive agents that may derive from various sources such as capillary rise of groundwater, rock weathering, or atmospheric deposition; which later precipitate within or on the surface of the media. This results in clogged pore structures, and hence affects the vapor flux between the evaporation front, where subsurface evaporation takes place, and the rock surface. It is known that salt precipitation results in lower evaporation rate; however, there is still need to investigate various aspects of these processes. In the present study, sodium chloride and magnesium sulfate salts were used for evaporation experiments using loose porous media of different structure: similar grain size of natural sand and well-rounded glass beads. The combined effect of grain angularity and concentration of salt solutions were examined in cylindrical glass containers. For each experiment, the mass loss is calculated with periodic weighting, and visual changes are measured and documented. The laboratory experiments were performed in three stages: a) different type of salts under the same conditions, b) same type of salt in different concentrations, c) same type of salt solution in structurally different porous medium. We found that magnesium sulfate caused decrease in evaporation rate by a factor of 5 compare to the same concentration of sodium chloride. Comparing the sodium chloride solution in different concentrations, the solution with higher concentration showed a slower trend growth on evaporation rate. Regarding the difference of pore structure, sodium chloride created a salt crust that was covering circa 90% of the surface with superficial fractures in the case of natural sand whereas in the case of glass beads, it covered only less than 40% of the surface. Nevertheless, the evaporation rate in the described experiment from natural sand showed a faster trend growth than in the case of the glass beads, which agrees with the observation of the evaporation front, which dropped down relatively faster in natural sand than in the glass beads. This indicates that materials with more rounded grains tend to have lower evaporation rate with less visible salt crust on the surface, whereas materials with rougher grain surface tend to have higher evaporation rate with considerably thicker and wider salt crust on the surface. Therefore, the pore structure might be one of the important determinatives of salt weathering patterns in porous materials.
A seismotectonic study and minimum 1D velocity model for the Greater Geneva Basin, Western Switzerland
Authors: Antunes Verónica , Planès Thomas , Zahradník Jiří , Obermann Anne , Alvizuri Celso , Lupi Matteo
Published: March 2020

In the framework of the Geothermie2020 project, the canton of Geneva and the Industrial Services of Geneva (SIG) are currently developing geothermal exploration in the Greater Geneva Basin (GGB), located in south-western Switzerland and neighbouring France. Before geothermal exploration begins, it is important to investigate the ongoing seismic activity, its relationship with local tectonic features, and the large-scale kinematics of the area. Background seismicity suggest that the local tectonic structures affecting the basin may still be active. Moderate-magnitude earthquakes have been identified along the Vuache fault, a major strike-slip structure crossing the basin. In this context we deployed a dense temporary network of 20 broadband stations around and within the GGB, during ~1.5 years, and reaching a detection threshold 0.5ML. 

Using a new coherence-based detector (LASSIE), we detected and located 158 events in our area of interest. However, only 20 events were located in the GGB, with local magnitudes ranging from 0.7 to 2.2ML. We found no earthquakes in the Canton of Geneva where geothermal activities are taking place. We constructed a local minimum 1D velocity model with VELEST, using the recorded seismicity together with earthquakes from adjacent regions, in a total of 1263 P- and S-picks. The new velocity model allowed to relocate micro-seismic activity up to 11km depth along the main fault systems (i.e. Vuache, Cruseilles, Le Coin, and Arve) offsetting the GGB. We retrieved 8 new focal mechanisms for the area, using a combination of polarities and waveform inversion techniques (CSPS method). A stress inversion shows a tectonic deformation dominated by a quasi-pure strike-slip regime in the GGB, consistent with structural and geological data.

The study of microseismicity in a quiet sedimentary basin is challenging due to the scarce occurrence of seismic events combined with low signal-to-noise ratios and the often strong attenuation. However, the investigation of the sporadic (yet present) natural seismicity with dedicated dense networks could provide useful information about the GGB, even with a short-term experiment. We propose a newly-computed 1D velocity model that can be used in the GGB for seismic monitoring purposes throughout the geothermal project. This model can be easily improved later on, whenever more data is available. Monitoring the evolution and dispersion of the seismic-activity through the identified seismogenic areas during the geothermal project is essential. Quantifying the seismic rate in the basin before geothermal operations start will help to quantify the impact that geothermal energy extraction might have on the GGB. 
System identification models for waves in the inner magnetosphere
Authors: Boynton Richard , Aryan Homayon , Simon Walker , Balikhin Michael
Published: March 2020

This research develops forecast models of the spatiotemporal evolution of emissions throughout the inner magnetosphere between L=2-6 and at all MLT. The system identification, or machine learning, technique based on Nonlinear AutoRegressive Moving Average eXogenous (NARMAX) models is employed to deduce the forecasting models of the lower band chorus, Hiss, and magnetosonic waves using solar wind and geomagnetic indices as inputs. It is difficult to develop machine leaning based spatiotemporal models of the waves in the inner magnetosphere as the data is sparse and machine learning techniques require large amounts of data to deduce a model. To solve this problem, the spatial co-ordinates at the time of the measurements are included as inputs to the model along with time lags of the solar wind and geomagnetic indices, while the measurement of the waves by the Van Allen Probes are used as the output to train the models. The estimates of the resultant models are compared with separate data to the training data to assess the performance of the models. The models are then used to reconstruct the spatiotemporal waves over the inner magnetosphere, as the waves respond to changes in the solar wind and geomagnetic indices.  
Assessment of CH4 sources in the Arctic using regional atmospheric measurements and their link to surface emissions
Authors: Wittig Sophie , Berchet Antoine , Paris Jean-Daniel , Arshinov Mikhail , Machida Toshinobu , Sasakawa Motoki , Worthy Doug , Pison Isabelle
Published: March 2020

The Arctic is a critical area in terms of global warming. Not only are the rising temperatures already causing changes in the natural conditions of this region, but the high potential of increased methane (CH4) regional emissions are also likely to intensify global warming even stronger in the near term.

This future effect consists in the thawing and destabilization of inland and sub-sea permafrost that enhance the release of methane into the atmosphere from extensive CH4 and organic carbon pools which have so far been shielded by ice and frozen soil. Moreover, the high latitude regions are already playing a key role in the global CH4-budget because of such large sources as wetlands and freshwater lakes in addition to human activities, predominantly the fossil fuel industry of the Arctic nations.

However, the level of scientific understanding of the actual contribution of Arctic methane emissions to the global CH4-budget is still relatively immature. Besides the difficulties in carrying out measurements in such remote areas, this is due to a high inhomogeneity in the spatial distribution of methane sources and sinks as well as to ongoing changes in hydrology, vegetation and carbon decomposition.

Therefore, the aim of this work is to reduce the uncertainties about methane sources and sinks in the Arctic region during the most recent years by using an atmospheric approach, in order to improve the quality of the assessment of the local and global impacts.

To do so, the data of atmospheric CH4 concentrations measured at about 30 stations located in different Arctic nations have been analysed in regard to the trends, seasonal fluctuations and spatial patterns that they demonstrate as well as their link to regional emissions.
Towards a revision of 234U and 230Th decay constants
Authors: Kerber Inga Kristina , Warken Sophie , Gerdes Axel , Frank Norbert
Published: March 2020

The quality of uranium-series ages depends on the accuracy and precision at which the decay constants of 234U, 230Th and 238U are determined. Here, we present intermediate results for a revision of the decay constants of 234U and 230Th. Therefore, we examined a selection of different materials in secular equilibrium using isotope dilution multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). New approaches of our study in particular concern the characterization of routines for measuring all isotopes on Faraday cups, i. e. low abundance isotopes on cups with 10^13 Ohm amplifiers, and a different selection of materials in comparison to previous studies.  λ_234 could be determined so far at a precision of 24 ε and agrees with the latest literature value of Cheng et al. (2013) within its error margins.
Seasonal dynamics of mesopelagic organic particles in the subpolar North Atlantic. Learning from the crosstalk between biogeochemical Argo float measurements and PISCESv2 simulations
Authors: Galí Martí , Falls Marcus , Bernardello Raffaele
Published: March 2020

Organic particle populations in the mesopelagic layer span a wide range of sizes and sinking speeds. A long-standing paradigm in ocean biogeochemistry posits that large, fast-sinking detrital particles contribute to most of the vertical export flux of particulate organic carbon (POC), whereas small, slow-sinking or suspended particles comprise most (>90%) of the stock. Over the last decades, most studies have placed emphasis on understanding and predicting the vertical fluxes driven by large particles owing to their influence on ocean carbon storage. Yet, there are compelling reasons to study the dynamics of suspended and slow-sinking small POC (sPOC) in greater detail. First, sPOC likely supports most of the mesopelagic respiration. Second, recent studies have shown that a number of mechanisms can inject large amounts of sPOC into the mesopelagic layer, to the point that the sPOC fraction may seasonally dominate total vertical POC fluxes. Thus, better accounting for sPOC fluxes might allow us overcome historical difficulties in balancing mesopelagic carbon budgets.

In the last decade, hundreds of bio-optical sensors deployed on autonomous profiling robots (bgc-Argo floats) have enabled observation of small particle stocks between the sea surface and 1000 m depth with a profiling frequency of 1-10 days. These observations are showing that mesopelagic sPOC follows distinct seasonal cycles in different oceanic areas, and allow identification of sPOC supply events (e.g., caused by vertical mixing or by disaggregation or fragmentation of larger particles) and of net sPOC removal. Regarding ocean biogeochemistry models, they have traditionally been tuned to estimate sinking POC fluxes but failed to capture POC stocks. Recently, the formulation of POC degradation rates in the model PISCESv2 was changed and a POC reactivity continuum approach was adopted, which greatly improved the representation of small and big POC stocks. These parallel developments now enable the quantitative assessment of mesopelagic POC dynamics.

Here we analyze the annual cycles of mesopelagic sPOC in the subpolar North Atlantic, as seen by biogeochemical Argo floats, and compare them to their PISCESv2-simulated counterparts. We then discuss the processes that drive mesopelagic sPOC seasonality in the observations and in 1D model simulations. Finally, we present a genetic algorithm approach that uses biogeochemical Argo float observations to optimize the PISCESv2 parameters that influence sPOC, focusing on the interplay between particle degradation rate and sinking speed.
Silicon recycling through rice-residue management does not prevent silicon depletion in paddy rice cultivation
Authors: Hughes Harold , Trong Hung Dao , Sauer Daniela
Published: March 2020

Silicon (Si) is known to have beneficial effects on plants, in particular on rice, which is a strong Si accumulator. Si helps mitigate environmental stresses and nutrient deficits of plants. In some regions, the limited plant-available Si in soils might have detrimental effects on rice cultivation. Crop-residue recycling can help to maintain the amount of plant-available Si in soils. However, the effect of crop-residue management practices on the soil-plant Si cycle and on Si availability to plants remains largely understudied. Here, we contribute to fill this knowledge gap by reporting a study on the effects of three different rice-residue management practices on Si-depleted paddy rice systems from northern Vietnam. The rice-residue management practices were (1) direct incorporation of rice residues into the soils, (2) burning in the field, and (3) use as fodder for animals, followed by composting of the obtained manure, and subsequent application of the composted manure to the field. We analyzed different Si reservoirs in soils and plant-Si contents under these different practices. Our results show a strong correlation between the different soil Si reservoirs and plant Si contents. We found no significant difference with respect to plant-available Si in soils and plant-Si contents between the different management practices. Moreover, our data suggest that Si-depleted rice-cultivation systems proportionally lose Si through grain harvest faster than less Si-depleted systems, because of enhanced relative Si accumulation in the grains. This loss cannot be mitigated by straw recycling. It may be one of the reasons why straw recycling has only a limited effect in the extremely Si-depleted rice-cultivation systems that were analysed in this study. Such information is critical in finding ways to maintain an appropriate level of plant-available Si in cultivated soils.
Estimation of Vegetation Proportion Cover to Improve Land Surface Emissivity
Authors: Neinavaz Elnaz , Skidmore Andrew K. , Darvishzadeh Roshanak
Published: March 2020

Precise estimation of land surface emissivity (LSE) is essential to predict land surface energy budgets and land surface temperature, as LSE is an indicator of material composition. There exist several approaches to LSE estimation employing remote sensing data; however, the prediction of LSE remains a challenging task. Among the existing approaches for calculating LSE, the NDVI threshold method appears to hold well over vegetated areas. To apply the NDVI threshold method, it is necessary to know the proportion of vegetation cover (Pv). This research aims to investigate the impact of Pv's prediction accuracy on the estimation of LSE over the forest ecosystem. In this regard, a field campaign coinciding with a Landsat-8 overpass was undertaken for the mixed temperate forest of the Bavarian Forest National Park, in southeastern Germany. The Pv in situ measurements were made for 37 plots. Four vegetation indices, namely NDVI, variable atmospherically resistant index, wide dynamic range vegetation index, and three-band gradient difference vegetation index, were applied to predict Pv for further use in LSE computing. Unlike previous studies that suggested variable atmospherically resistant index can be estimated Pv with higher prediction accuracy compared to NDVI over the agricultural area, our results showed that the prediction accuracy of Pv is not different when using NDVI over the forest (R2CV = 0.42, RMSECV = 0.06). Pv was measured with the lowest accuracy using the wide dynamic range vegetation index (R2CV = 0.014, RMSECV = 0.197) and three-band gradient difference vegetation index (R2CV = 0.032, RMSECV = 0.018).  The results of this study also revealed that the variation in the prediction accuracy of the Pv has an impact on the results of LSE calculation.
Characterization of methane emissions from oil and gas production in Mexico: Linking measurements to mitigation
Authors: Zavala-Araiza Daniel , Omara Mark , Gautam Ritesh , Smith Mackenzie , Conley Stephen , Pandey Sudhanshu , Houweling Sander , Aben Ilse
Published: March 2020

A wide body of research has characterized methane emissions from the oil and gas supply chain in the US, with recent efforts gaining traction in Canada and Europe. In contrast, empirical data is limited for other significant oil and gas producing regions across the global south. Consequently, measuring and characterizing methane emissions across global oil and gas operations is crucial to the design of effective mitigation strategies.

Several countries have announced pledges to reduce methane emissions from this sector (e.g., North America, Climate and Clean Air Coalition [CCAC] ministers). In the case of Mexico, the federal government recently published regulations supporting a 40-45% reduction of methane emissions from oil and gas. For these regulations to be effective, it is critical to understand the current methane emission patterns.

We present results from multi-scale empirical estimates of methane emissions from Mexico’s major oil and gas production regions (both offshore and onshore), based on a set of airborne-based measurement campaigns, analysis of satellite data (TROPOMI), and development of spatially explicit inventories. Our results provide a revised estimate of total emissions in the sampled regions and highlight the importance of empirically based characterization as a basis for prioritization in terms of emission reduction opportunities.

Finally, we highlight how these measurements –as well as similar policy-relevant studies- connect into action, based on the current needs from relevant stakeholders (e.g., inventory builders, regulators and industry).
Age distribution and organic matter degradation in bioturbated sediment
Authors: Kuderer Matthias , Middelburg Jack J
Published: March 2020

Bioturbation is an important process in the early diagenesis of soft marine sediment. Benthic infaunal activity, such as feeding, burrowing and ploughing redistributes particles within the topmost layers of the sediment. Recently deposited particles are mixed into deeper sediment depth layers and old material remains longer near the surface. A sediment layer thus contains an assemblage of particles from young to very old ages. Under certain assumptions, bioturbational mixing can be modelled as a diffusive process with the macroscopic mixing coefficient DB. Here we model the age distribution of the bioturbated sedimentary record with a depth dependent mixing coefficient DB(z). The potential age bias introduced by mixing is typically higher than multiples of the mean mixed layer residence time, which scales linearly with the ratio of mixed layer depth and sediment accumulation rate. Scaling the mixing intensity has only a minor effect, as most marine environments are mixing dominated.

The rate of organic matter degradation can been modelled empirically as an age dependent process, with recently deposited, fresh organic matter having higher reactivities than older and more refractory material. With insights into the age distribution, this allows to couple the degradation of organic matter with bioturbation and estimate the burial of carbon.
Revisiting ENSO Atmospheric Teleconnections and Challenges
Authors: Taschetto Andréa S. , Ummenhofer Caroline C. , Stuecker Malte  F. , Dommenget Dietmar , Ashok Karumuri , Rodrigues Regina R. , Yeh Sang-Wook
Published: March 2020

The warming of the equatorial Pacific associated with the El Niño–Southern Oscillation (ENSO) causes profound impacts on rainfall and temperature in the tropics and extratropics. El Niño drives changes in the Walker and Hadley circulations, warms the tropics and affects the neighboring ocean basins, favoring a short-term rise in global temperatures. We will present an overview of the atmospheric teleconnections driven by ENSO and its diversity focusing on the impacts over land and remote ocean basins. During El Niño, dry conditions are generally observed in the Maritime Continent, northern South America, South Asia and South Africa, while wet weather typically occurs in southwestern North America, western Antarctica, and east Africa. Global effects during La Niña are overall the opposite to El Niño, however this assumption is not true for all regions. ENSO atmospheric teleconnections are non-linear in part due to different locations of the anomalous equatorial warming (Eastern versus Central Pacific events) superimposed on the Pacific mean state, as well as interactions with the annual cycle, off-equatorial regions, remote ocean basins, and other modes of climate variability. Adding to this complex behavior, ENSO teleconnections are non-stationary either due to deterministic low-frequency modulations or stochastic variability, the latter being a factor generally overlooked in the literature. As the world warms in response to greenhouse gas forcing, ENSO atmospheric teleconnections are expected to change, despite large uncertainties in ENSO projections. We will discuss the limitations of climate models in representing realistic teleconnections from the tropical Pacific to remote regions and some of the challenges for future projections.
Dynamic boundary conditions control the spatial and temporal variations of nutrient turnover in human impacted surface waters
Authors: Schuetz Tobias , Kurm Anna , Gößges Till , Groß Marion , Schmitz Selina , Krehenwinkel Henrik
Published: March 2020

The temporal dynamics of nutrient cycles and the remineralization of micropollutants in given stream or river sections are driven by a complex interplay of hydraulic, climatic and ecological processes which are difficult to quantify and to predict. Typically, we use either e.g. water levels or velocity, radiation input, oxygen availability, water and air temperatures, hyporheic exchange or the activity of auto- and heterotroph organisms alone or in combination to explain observed rates of substance cycling. To improve the predictability of occurring nutrient cycles and biomass growth we selected seven river reaches (1.5 -3.3 km) throughout the Mosel-region in western Germany which are located down stream of sewage water treatment plant effluents. Over a time span of four months we carried out about 10 longitudinal snapshot sampling campaigns at each of the river sections. We sampled for nutrients (C, N, P) and selected pharmaceutical products as well as the hydraulic and climatic and boundary conditions. Additionally, at one of the river sites we observed along the river reach weekly microbial biofilm growth rates, microbial biodiversity (DNA), macrozoobenthos biodiversity in the dominating streambed substrates as well as weekly samples of C, N, P in the sediment.

The results show clearly how the interplay between hydraulic and climatic boundary conditions controls ongoing nutrient cycles and process rates; e. g. the spatial (downstream) extent of measurable surplus C, N, and P varies clearly over time as well as between the substances (P > C > N). Restricted by hydraulic boundary conditions, biomass production and a reduced (function specific) biodiversity of microbial biofilms coincide either with high nutrient surplus or with exposition to solar radiation. Favorable ambient conditions (lower water levels and higher energy availabilty) are dominant drivers for observable removal of pharmaceutical products rather than nutrient availability. Overall, our results demonstrate the importance of the local settings (cross section, shading) in combination with season and hydraulic loadings at given river sections for occurring process rates in nutrient cycles and biomass growth.
Diffusion of climatic signals in ice cores by vein migration
Authors: Ng Felix S. L.
Published: March 2020

Ice-core analysis shows that climatic signals carried by dissolved impurities (e.g., sulphate) in the water veins exhibit peak broadening and damping with depth into the ice. Such diffusion distorts the signals progressively, limiting the retrievability of the past climatic variations, notably their time resolution. A mechanism put forward for the diffusion invokes continuous differential grain growth in creating gradients in impurity concentration in the vein water (Barnes et al., 2003). Separately, a mechanism known as “anomalous diffusion” has been proposed (Rempel et al., 2001) where vertical temperature gradients in the ice drive the migration of chemical peaks without diffusion — this migration causes age offset between the signals and the ice. Here, we show that climatic signals diffuse because of constant dynamical evolution of the vein network in polycrystalline ice that accompanies grain-boundary migration. In this new mechanism, the stochastic motion of vein segments carrying solute leads to a net diffusive transport of impurities when there is spatial gradient in the bulk impurity concentration or porosity. By modelling this phenomenon with a statistical-mechanical formulation in three dimensions, we find that the diffusivity κ for the bulk impurity concentration is given by κ = K(T)/3c, where K is the temperature-dependent grain growth rate and c (≈ 2 to 3) is a geometry constant, and that κ is independent of the mean grain size. The description of porosity follows an advection-diffusion equation that includes the other processes of Rempel et al. (2001) and Barnes et al. (2003). Our calculations for the Greenland summit ice cores and the EPICA ice core predict diffusivities of κ ∼ 10–8 – 10–7 m2 yr–1, which can explain the observed amount of peak broadening. Further including into this theory the regelative transport of the solute by water flow along the veins reveals a correction of ≈ 10% for the signal migration speed predicted by Rempel et al. (2001). Besides contributing a new diffusion mechanism, our study highlights the importance of grain-scale recrystallisation processes for understanding bulk ice properties.
Inferring the Last Interglacial West Antarctic Ice Sheet from the coupling of an ice core water stable isotope record and an atmospheric general circulation model
Authors: Goursaud Sentia , Sime Louise , Wolff Eric
Published: March 2020

The Last Interglacial period (130-115 ka BP, hereafter LIG) is often considered as a prime example to study the effect of warmer-than-present temperatures on polar ice sheets evolution. As the debate mainly focuses on the causes and tipping point of a potential collapse of the West Antarctic Ice Sheet (hereafter WAIS), few investigations examine the consequences of a wais collapse in terms of atmospheric circulation. However, a knowledge of the state of the atmosphere is necessary to use proxy data recorded in ice cores. By analysing a new ice core drilled in Skytrain ice rise and using climate modeling, the WACSWAIN (WArm Climate Stability of West Antarctic ice sheet in the last Interglacial) aims to reconstruct WAIS extent during the LIG. Here, we use simulations from the atmospheric general circulation model HadCM3  with different WAIS configurations. We show that changes in temperature are directly linked to changes in orography through thermodynamic effects, as well as a linear sea ice extent rise over the Pacific Ocean with the WAIS reduction explained by a reversal of meridional winds turning southwards as the WAIS disappears. At the Skytrain ice rise, we show that not only the isotopic thermometer can be applied, but we also suggest that the water stable isotope record imprinted in the ice core will allow us to quantify the wais reduction.