bluuebunny/crossref_metadata_2025 huggingface dataset:
Transform versus non-transform offsets controlled by offset length and the variation in magmatic accretion within the offset zone
Authors: Schierjott Jana , Ito Garrett , Behn Mark , Morrow Thomas , Tian Xiaochuan , Kaus Boris
Published: March 2022

Transform faults and non-transform offsets define the bounds of mid-ocean ridge spreading segments, but tectonic and magmatic controls on the length of segments and the morphology of intervening offsets are poorly understood. A general observation at intermediate and slow-spreading oceanic environments is that localized strike-slip motion along transform faults tends to occur on larger offsets in space or crustal age, whereas more diffuse deformation at non-transform zones occurs at shorter offsets distances. In addition, variables such as lithospheric thickness, the size and spacing of faults, and the fraction (M) of extension accommodated by magmatic accretion (rather than faulting) are known to influence the overall morphology of the ridge segment and its vicinity. We hypothesize that the decrease in the amount of magmatic extension along the ridge segment towards the discontinuity along with the ridge segment offset play a role in defining the transition between transform and non-transform offsets.

In this study, we employ a 3D-numerical model to investigate how the relative amounts of fault- or magma-accommodated spreading and distance offset (D) between ridge segments control the development of transform versus non-transform offsets. Our model employs a ridge-like initial temperature structure, with magma intrusion simulated by adding a divergence to the right-hand-side of the continuity equation within a magmatic accretion zone at the ridge axis. M, the fraction of magmatically compensated spreading inside the magmatic accretion zone, can be varied along strike. By using a visco-elasto-plastic formulation the model can simulate the spontaneous formation and evolution of normal faults that accommodate part of the spreading. The temperature field is allowed to evolve and the model accounts for an increased, temperature-dependent conductivity around each ridge segment. We vary both the offset distance D separating two axes of magmatic accretion as well as the length L over which M decreases along the ridge axes towards the discontinuity. We find that increasing L leads to non-transform offsets, particularly for small offset distances D. As D increases, the occurrence of the offset zone is less prominently dominated by L. Depending on M, the style of faulting differs along the magmatic segments. While for M>0.5 we observe migrating faults creating topography similar to abyssal hills, values for M that are smaller or equal to 0.5 lead to stationary faults which are located closer to the ridge axis. 
Borehole Disposal of Radioactive Waste in Israel 
Authors: Klein-BenDavid Ofra , Freeze Geoff , Sassani David , Calvo Ran , Balaban Noa , Peer Gilboa
Published: March 2022

Israel is assessing borehole disposal of radioactive waste. With limited geological options for disposal, intermediate-depth borehole disposal is being considered in the arid Yamin Plain region of the northeastern Negev desert at depths of several hundred meters below ground surface in the vadose zone. Unlike deep borehole disposal of several kilometers, which relies on emplacement below the depth of recirculating groundwater, the safety case for intermediate-depth borehole disposal relies more on the aridity of the vadose zone, the robustness of the engineered barriers (e.g., canister, seals, backfill materials) in the disposal borehole.

To study the suitability of the Yamin Plain region for borehole disposal a small-diameter characterization borehole is planned, to retrieve core samples and to better understand the vadose zone geo-mechanical and hydrogeochemical properties and percolation flux. Moreover, a wide range of laboratory geochemical, hydrological, and mechanical studies as well as a new seismic survey are being carried out. The information from the characterization borehole as well as the supplementary laboratory and seismic studies will inform the safety case, and together with performance assessment analyses will help to identify key areas of uncertainty and guide future research and development activities aimed at demonstrating the feasibility of the intermediate-depth borehole disposal concept in Israel.
An Atmospheric Bridge Between the Subpolar and Tropical Atlantic Regions:A Perplexing Asymmetric Teleconnection
Authors: Baek Seung Hun , Kushnir Yochanan , Robinson Walter , Lora Juan , Lee Dong Eun , Ting Mingfang
Published: March 2022

The largest sea surface temperature (SST) anomalies associated with Atlantic Multidecadal Variability (AMV) occur over the Atlantic subpolar gyre, yet it is the tropical Atlantic from where the global impacts of AMV originate. Processes that communicate SST change from the subpolar Atlantic gyre to the tropical North Atlantic thus comprise a crucial mechanism of AMV. Here we use idealized model experiments to show that such communication is accomplished by an “atmospheric bridge.” Our results demonstrate an unexpected asymmetry: the atmosphere is effective in communicating cold subpolar SSTs to the north tropical Atlantic, via an immediate extratropical atmospheric circulation change that invokes slower wind-driven evaporative cooling along the Eastern Atlantic Basin and into the tropics. Warm subpolar SST anomalies do not elicit a robust tropical Atlantic response. Our results highlight a key dynamical feature of AMV for which warm and cold phases are not opposites.
Accuracy of GNSS positioning: GPS+GLONASS case
Authors: Cetin Deniz , Sanli D.Ugur , Ogutcu Sermet
Published: March 2022

For a long time, the main factor affecting the accuracy of GPS PPP has been the observing session duration. Researchers have recently shown that the accuracy of PPP also varies with latitude. The reason for the latitudinal variation is the inability to determine the tropospheric zenith delay with a globally homogeneous precision and its impact on the position determination results. A formula has been developed to give the accuracy of the PPP position in a local geocentric system based on observation session duration and latitude. Currently, the interest of researchers is to determine the accuracy of Multi-GNSS solutions. In this context, the MGEX experiment of the IGS provides a rich data source to researchers. In this study, 15 globally distributed GNSS stations were selected from the MGEX network, GPS+GLONASS data was evaluated with CSRSPPP software, and the accuracy of the GNSS positioning was investigated. Continuous GNSS observations and 8-hour campaign measurements are evaluated comparatively. The results of the study showed that 60% of the RMS values obtained from the 24-hour data became smaller, indicating that it was equal between the horizontal and vertical coordinate components. The improvement in campaign solutions is better and around 80% overall. The share of this between horizontal position and vertical position is around 73% and 87%, respectively. The average improvement in the RMS of the coordinate components is around 0.5 mm for the campaign solutions, but the improvement can reach up to 2 mm at some stations. Our motivation was to determine whether this improvement was reflected in the accuracy modeling. Initial findings show that the results are in agreement with the latest accuracy modeling, and it turns out that the positioning accuracy of GNSS PPP also depends on the latitude of the GNSS site as well as the observation session, as in the GPS PPP.
Body wave extraction by using sparsity-promoting time-frequency filtering
Authors: Imanibadrbani Bahare , Mohammadigheymasi Hamzeh , Sadidkhouy Ahmad , Fernandes Rui , Gholami Ali , Schimmel Martin
Published: March 2022

Different phases of seismic waves generated by earthquakes carry considerable information about the subsurface structures as they propagate within the earth. Depending on the scope and objective of an investigation, various types of seismic phases are studied. Studying surface waves image shallow and large-scale subsurface features, while body waves provide high-resolution images at higher depths, which is otherwise impossible to be resolved by surface waves. The most challenging aspect of studying body waves is extracting low-amplitude P and S phases predominantly masked by high amplitude and low attenuation surface waves overlapping in time and frequency. Although body waves generally contain higher frequencies than surface waves, the overlapping frequency spectrum of body and surface waves limits the application of elementary signal processing methods such as conventional filtering. Advanced signal processing tools are required to work around this problem. Recently the Sparsity-Promoting Time-Frequency Filtering (SP-TFF) method was developed as a signal processing tool for discriminating between different phases of seismic waves based on their high-resolution polarization information in the Time-Frequency (TF)-domain (Mohammadigheymasi et al., 2022). The SP-TFF extracts different phases of seismic waves by incorporating this information and utilizing a combination of amplitude, directivity, and rectilinearity filters. This study implements SP-TFF by properly defining a filter combination set for specific extraction of body waves masked by high-amplitude surface waves. Synthetic and real data examinations for the source mechanism of the  Mw=7.5 earthquake that occurred in November 2021 in Northern Peru and recorded by 58 stations of the United States National Seismic Network (USNSN) is conducted. The results show the remarkable performance of SP-TFF extracting P and SV phases on the vertical and radial components and SH phase on the transverse component masked by high amplitude Rayleigh and Love waves, respectively. A range of S/N levels is tested, indicating the algorithm’s robustness at different noise levels. This research contributes to the FCT-funded SHAZAM (Ref. PTDC/CTA-GEO/31475/2017) and IDL (Ref. FCT/UIDB/50019/2020) projects. It also uses computational resources provided by C4G (Collaboratory for Geosciences) (Ref. PINFRA/22151/2016).

REFERENCE
Mohammadigheymasi, H., P. Crocker, M. Fathi, E. Almeida, G. Silveira, A. Gholami, and M. Schimmel, 2022, Sparsity-promoting approach to polarization analysis of seismic signals in the time-frequency domain: IEEE Transactions on Geoscience and Remote Sensing, 1–1.
Solar wind modelling with EUHFORIA and comparison with the PSP observations
Authors: Valliappan Senthamizh Pavai , Magdalenic Jasmina , Rodriguez Luciano , Poedts Stefaan , Samara Evangelia
Published: March 2022

During recent decades, numerous studies were devoted to improve our understanding of the origin and the propagation of the fast solar wind, and its accurate modelling. The solar wind characteristics were poorly mapped up to now by the in situ observations, available mostly only at about 1AU. The novel Parker Solar Probe (PSP) observations, that are employed in this study, allow us to map the solar wind characteristics in the low solar corona at only few tens of solar radii, and to study the solar wind characteristics. These observations are also very important for understanding how accurately we can model the solar wind characteristics employing models such as EUHFORIA (European heliospheric forecasting information asset, Pomoell & Poedts, 2018), at distances rather close to the Sun.
In this study, we inspect the solar wind characteristics during the first eight closest PSP approaches to the Sun. The solar wind plasma characteristics observed by PSP are compared with the modelling results using the default set-up of EUHFORIA. We also calibrate the inner boundary (0.1 AU) conditions in EUHFORIA, but without changing the Wang-Sheeley-Arge formula which describes the solar wind characteristics at the inner boundary. The aim is to better model the solar wind at distances close to the Sun. We also use a magnetic connectivity tool (developed by ESA’s MADAWG group) to better associate the fast solar wind with its source region on the Sun.
Two decades of forest monitoring shows instability in the rainforests
Authors: Singh Chandrakant , van der Ent Ruud , Wang-Erlandsson Lan , Fetzer Ingo
Published: March 2022

The tropical terrestrial ecosystems naturally exist as alternative stable states, commonly referred to as forest and savanna ecosystems. However, these ecosystems, especially forests, are currently threatened by the risk of drought-induced forest-to-savanna transitions across the tropics and subtropics. Therefore, a better understanding of ecosystem dynamics and characteristics behind these alternative stable states is crucial in predicting their response to future hydroclimatic changes. Previous studies have analyzed these alternative stable states against precipitation predominantly based on space-for-time substitution. However, such a substitution provides a partial picture of ecosystem adaptation dynamics and associated ecosystem structural change over time. 

Here, we empirically study the transient state of tropical ecosystems and their hydroclimatic adaptations by examining remotely sensed tree cover and root zone storage capacity over the last two decades in South America and Africa. Tree cover represents the above-ground ecosystem structure's density, and is derived directly from MODIS satellite data. Whereas root zone storage capacity is the maximum amount of soil moisture that the vegetation can access for transpiration is derived using daily precipitation and evaporation data. 

We found that ecosystems at high (>75%) and low (<10%) tree cover adapt to changing precipitation by instigating considerable subsoil investment while experiencing limited tree cover change over time. For these ecosystems, the below-ground investment does not come at the cost of changing the above-ground ecosystem structure. Thus, we deem these ecosystems as stable since ecosystems' adaptive dynamics keep the structural characteristics intact. In contrast, unstable ecosystems at intermediate (30-60%) tree cover were unable to exploit the same level of adaptation as stable ecosystems, thus showing considerable changes to their above-ground ecosystem structure. We also found that ignoring this adaptive capacity of the ecosystem can underestimate the resilience of the forest ecosystems, which we find is largely underestimated in the case of the Congo rainforests. The results from this study emphasize the importance of the ecosystem's temporal dynamics and adaptation in inferring and assessing the risk of forest-savannah transitions under rapid hydroclimatic change.
Effects of environmental filtering and PFT-based model parameterization approaches on NBE prediction errors across the globe
Authors: Famiglietti Caroline A. , Worden Matthew , Quetin Gregory R. , Smallman T. Luke , Dayal Uma , Bloom A. Anthony , Williams Mathew , Konings Alexandra G.
Published: March 2022

Accurate forecasts of net biosphere exchange (NBE) are vital for understanding the role of terrestrial ecosystems in a changing climate. It is therefore problematic that NBE projections from most state-of-the-art terrestrial biosphere models (TBMs) diverge considerably from one another. Efforts to reduce this divergence have historically focused on improving models’ structural realism, but several lines of evidence have brought the role of poorly determined and/or over-generalized parameters into sharper focus. Here we investigate how different parameterization assumptions propagate into NBE prediction errors across the globe. To do so, we simulate two methods for parameter assignment within a flexible model–data fusion framework (CARDAMOM): (a) the traditional plant functional type (PFT)-based approach, whereby parameters retrieved at a small number of select locations are applied broadly within regions sharing similar land cover characteristics; and (b) a novel top-down “environmental filtering” (EF) approach, whereby a pixel’s parameters are predicted based on relationships with climate, soil, and canopy properties. In an effort to isolate the role of parametric from structural uncertainty, we benchmark the resulting PFT-based and EF-based NBE predictions with estimates from a Bayesian optimization approach (whereby “true” parameters consistent with a suite of data constraints are retrieved on a pixel-by-pixel basis). We find that the EF-based approach outperforms the PFT-based approach at twice as many pixels as the converse and across multiple performance metrics. However, NBE estimates from the EF-based approach may be more susceptible to compensation between errors in component flux predictions. This work provides insight into the relationship between TBM performance and parametric uncertainty, informing efforts to improve model parameterization via nontraditional approaches.
FABDEM - A 30m global map of elevation with forests and buildings removed
Authors: Uhe Peter , Hawker Laurence , Paulo Luntadila , Sosa Jeison , Sampson Christopher , Neal Jeffrey
Published: March 2022

Digital Elevation Models (DEMs) depict the elevation of the Earth’s surface and are fundamental to many applications, particularly in the geosciences. To date, global DEMs contain building and forest artifacts that limit its functionality for applications that require precise measurement of terrain elevation, such as flood inundation modeling. Using machine learning techniques, we remove both building and tree height bias from the recently published Copernicus GLO-30 DEM to create a new dataset called FABDEM (Forest And Buildings removed Copernicus DEM). This new dataset is available at 1 arc second grid spacing (~30m) between 60°S-80°N, and is the first global DEM to remove both buildings and trees.

Our correction algorithm is trained on a comprehensive and unique set of reference elevation data from 12 countries that covers a wide range of climate zones and urban types. This results in a wider applicability compared to previous DEM correction studies trained on data from a single country. As a result, we reduce mean absolute vertical error from 5.15m to 2.88m in forested areas, and from 1.61m to 1.12m in built-up areas, compared to Copernicus GLO-30 DEM. Further statistical and visual comparisons to other global DEMs suggests FABDEM is the most accurate global DEM with median errors ranging from -0.11m to 0.45m for the different landcover types assessed. The biggest improvements were found in areas of dense canopy coverage (>50%), with FABDEM having a median error of 0.45m compared to 2.95m in MERIT DEM and 12.95m for Copernicus GLO-30 DEM.

FABDEM has notable improvements over existing global DEMs, resulting from the use of Copernicus GLO-30 and a powerful machine learning correction of building and tree bias. As such, there will be beneifts in using FABDEM for purposes where depiction of the bare-earth terrain is required, such as in applications in geomorphology, glaciology and hydrology.
Distribution of the Ring Current and Coupling with Field-Aligned Currents: Joint observation of MMS and Swarm
Authors: Tan Xin , Dunlop Malcolm , Yang Yanyan , Yang Junying , Russell Christopher
Published: March 2022

The ring current and field-aligned currents have a dominant effect in the inner magnetospheric current system, where the coupling mechanism to the ionosphere has a significant impact on space weather and magnetic activity on the ground. We use FGM data from the four spacecraft MMS mission to estimate in situ current density and study the distribution of the ring current, by statistically analyzing the azimuth component of current density. We also compare the statistical results of field-aligned component of current density from MMS with the statistical results of dual-FAC data of Swarm in the same time range to explore the large-scale coupling of the ring current and field-aligned currents. The joint observational results show that: on the one hand (on the dawn side), due to the injection of Region 2 field-aligned currents, the westward ring current increases continuously from noon to midnight; while (on the dusk side, from midnight to noon), due to the injection of Region 1 field-aligned current near midnight and the outflow of Region 2 field-aligned currents, the westward ring current increases, then decreases until it turns eastward and increases in magnitude. On the other hand, due to the existence of a mesoscale, clockwise banana current centered at about 4.8Re (Earth Radii) between noon and dusk, the eastward ring current is significantly enhanced in the inner ring and enhanced westward in the outer ring. Similarly, due to the existence of a mesoscale counterclockwise current centered at about 4.8Re between midnight and dawn, the westward ring current is slightly enhanced in the inner ring and enhanced eastward in the outer ring. The influence of these two factors on the distribution of the ring current is of the same order of magnitude. Work to clarify the operation of these effects relative to activity levels is in progress.
Validation and adaptation of WRF-Chem numerical model to simulate CO2 transport in Saint-Petersburg
Authors: Nerobelov Georgy , Timofeyev Yuri , Foka Stefani , Hatakka Juha , Virolainen Yana , Smyshlyaev Sergei
Published: March 2022

Alteration of the Earth's radiation balance due to the rise of the content of the main anthropogenic greenhouse gas СО2 in the atmosphere leads to the changes of the planet's climate. It is known that megacities contribute approximately 70% to the total anthropogenic CO2 emissions playing a critical role in the climate changes. Several methods of emission estimation are being developed to control commitments undertaken by different countries on reducing greenhouse gas emissions. One of such methods - inverse modelling - combines accurate observations of the increase of gas` content, a priori anthropogenic emissions and numerical modelling of atmospheric transport to define gas` sources and correct emission data used in the simulation. Several studies demonstrated that the inverse modelling of CO2 anthropogenic emissions highly depends on the modelling of CO2 transport in the atmosphere. Therefore a careful validation of such models must be carried out before CO2 emissions estimation by the inverse modelling. In the current research we studied capabilities of numerical weather prediction and chemistry dynamic model WRF-Chem to simulate CO2 transport on the territory of Saint-Petersburg (Russia) using observations of near-ground and total CO2 content. 
Ten-year long-range transport of radiocaesium in the surface layer in the Pacific Ocean and its marginal seas
Authors: Aoyama Michio , Kumamoto Yuichiro , Inomata Yayoi
Published: March 2022

Radiocaesium derived from the Fukushima Dai-ichi Nuclear Power Plant (FNPP1) accident was observed across a wide area of the North Pacific, not only in surface seawater, but also in the ocean interior. In this presentation, we summarized the time scale of Lagrangian transport of the FNPP1 derived radiocaesium in surface water during the period from the time of the accident to March 2021 in the North Pacific and the Arctic Oceans and its marginal seas as shown below.

Initial observation results until December 2012 in the surface layer in the North Pacific Ocean by the global observations revealed that a typical feature within one year after the accident was a westward movement across the North Pacific Ocean, speed of which was reported at 7 km day-1 until August 2011. After that, the main body of FNPP1-derived radiocaesium moved east as 3 km day-1 and is separated from Japan in 2013. The arrival of the FNPP1 signal at the west coast of the American continent was reported in 2014. The elevation in the FNPP1 derived radiocaesium concentration in the Bering Sea in 2017 and in the Arctic Ocean in 2019 was reported. The northward bifurcation of the Kuroshio Extension made these obvious transport of the FNPP1 derived radiocaesium to the subarctic and arctic region while the transport by southward bifurcation was not observed. At Hawaii Islands in the subtropical gyre, there was no signal of the FNPP1 derived radiocaesium during the period from March 2011 and February 2017. At Yonaguni Island where the Kuroshio enters the East China Sea, the FNPP1 signal arrived at Yonaguni Islands eight years after the time of the accident, and these might be transported mainly from the subtropical gyre.

At the marginal seas of the North Pacific Ocean, the elevation in the FNPP1 derived radiocaesium concentration in the northern East China Sea in 2014, in the Sea of Japan in 2014/2015 were observed.

We also briefly summarize study results on nuclides other than radiocaesium (e.g., 90Sr, 239240Pu, and 129I).
Joint analysis of GNSS and seismic data to track magma transport at Piton de la Fournaise volcano (La Réunion, France)
Authors: Journeau Cyril , Peltier Aline , Shapiro Nikolai , Beauducel François , Ferrazzini Valérie , Duputel Zacharie , Taisne Benoit
Published: March 2022

Geophysical measurements from the networks of instruments maintained by volcano observatories for several decades provide a large database that is rich in information concerning magma transport from deep storage zones to its shallow propagation before eruptions. In this study, we analyze multi-year time series of GNSS and seismic data acquired at Piton de la Fournaise (PdF) volcano (La Réunion, France) from 2014 up to now. These observations are sensitive to the dynamics of the magma within the volcanic system and their detailed study allows us to better apprehend its behavior both during pre-eruptive periods, by informing us about the preparation phases before an eruption and also during co-eruptive periods, by following the eruptions time-evolution and the corresponding dynamics.

We propose to scan continuously GNSS data by inverting them in time windows ranging from minutes to days using a point compound dislocation model (pCDM). This approach provides analytical expressions for surface displacements due to a complex source of deformation with variable geometry to model different shapes such as dikes, prolate ellipsoids, or pipes. As a result, we image a deep reservoir around 7-8 km below the PdF summit, as well as, in some cases, the upward magma migration dynamics in the crust over several days toward a shallow reservoir at sea level and the final dyke propagation over a few hours that ultimately feeds the eruptive site.

These observations are systematically compared to seismic data over the same time period and are jointly interpreted. We use both the seismicity catalog of "regular" volcano-tectonic events as well as the results of cross-correlations network-based methods obtained with the CovSeisNet package allowing the detection of “un-regular” signals and the location of their sources, such as micro-seismicity generated during dyke propagation, and long-period seismicity (tremor and LP events).

The joint use of information from geodetic and seismic networks constitutes an important step in improving our knowledge of volcanic systems. While the analysis of GNSS network data enables the imaging of active pressure-sources in the system with an estimation of the volumes of involved magma, the seismic network analysis allows for a more detailed view of the magma dynamics in the volcanic edifice.
Fate and transport of titanium dioxide nanoparticles in porous media 
Authors: Manik Rima , Narayanan Seetha
Published: March 2022

Fate and transport of titanium dioxide nanoparticles in porous media

Rima Manik, N. Seetha

Department of Civil Engineering, Indian Institute of Technology Hyderabad, Kandi, Sangareddy-502284, India

 

Abstract

Increasing use of engineered nanoparticles in various fields has led to its inevitable release into the natural environment thereby causing soil and groundwater contamination. Soil is inhabited by various types of bacteria, which forms biofilm on the grain surface. Biofilms have been found to influence the fate & transport of nanoparticles. In this study, the transport behavior of titanium dioxide (nTiO2) nanoparticles through soil is studied through laboratory column experiments in the presence and absence of soil biofilm. Escherichia coli BL21 strain is used for the biofilm formation. It is observed that the retention of nTiO2 is larger in the presence of biofilm than in its absence. This indicates that biofilm acts as a more favourable attachment site for TiO2 than the bare soil. The column experiment results are further modelled using a 1D advection-dispersion-deposition equation. The mechanisms predominantly observed in the experiment are straining and ripening.
Quaternary magmatism above a slab tear, Northern Andes of Colombia
Authors: Conde-Carvajal Camilo , Kammer Andreas , Avila-Paez Michael , Cubillos Sofia , Piraquive Alejandro , von Quadt Albrecht
Published: March 2022

The north Andean block evidences by its shallow to intermediate seismicity a juxtaposition of a southern, relatively steeply dipping slab segment with a correlating volcanic arc and a northern flat slab domain, where a margin-parallel volcanic arc became extinct since the Late Miocene. The clear-cut offset of the seismic pattern suggests the presence of a slab tear, which has its correlative morphological expression by a distinct lineament in the Cauca Valley and separates, within the Eastern Cordillera of Colombia, a southern narrow antiformal cordilleran tract from a northern composite belt with an axial depression that constitutes the High Plain of Bogotá. Faults are consistently blind and associated with tight, basement-cored folds with inverted limbs at the mountain front and distinct domes separated by marginal synclines. These structures belong to a young deformation phase as they were superposed on older cylindrical fold trains. Their ductile deformation style may be associated with a thermal anomaly as evidenced by abnormally high Ro data. In order to assess the age of this folding we extracted zircons from a rhyolitic dike that straddles a marginal syncline of a major dome. U-Pb age data indicate a recycling of these crystals from a Neoproterozoic volcanoclastic sequence that composes the basement of this marginal part of the Cordillera. Euhedral overgrowths yield, however, Quaternary ages that we tentatively associate to the advance of the outer bend of the flat slab to its present position.
AmazonFACE – Assessing the response of Amazon rainforest functioning to rising atmospheric CO2 concentration
Authors: Rammig Anja , Lapola David ,   AmazonFACE team
Published: March 2022

The rapid rise in atmospheric CO2 concentration over the past century is unprecedented. It has unambiguously influenced Earth’s climate system and terrestrial ecosystems. Plant responses to rising atmospheric CO2 concentrations are thought to have induced an increase in biomass and thus, increased the carbon sink in forests worldwide. Rising CO2 directly stimulates photosynthesis (the so-called CO2-fertilization effect) and tends to reduce stomatal conductance, leading to enhanced water-use efficiency, which may provide an important buffering effect for plants during adverse climate conditions. For these reasons, current global climate simulations consistently predict that tropical forests will continue to sequester more carbon in aboveground biomass, while several lines of evidence point towards a decreasing carbon sink strength of the Amazon rainforest in the coming decades, potentially driven by nutrient limitation, droughts or other factors. Mechanistically modelling the effects of rising CO2 in the Amazon rainforest are hindered by a lack of direct observations from ecosystem scale CO2 experiments. To address these critical issues, we have been developing a free-air CO2 enrichment (FACE) experiment in an old-growth, highly diverse, tropical forest in the Brazilian Amazon and we present our main hypotheses that underpin the AmazonFACE experiment.  We focus on possible effects of rising CO2 on carbon uptake and allocation, phosphorus cycling, water-use and plant-herbivore interactions, and discuss relevant ecophysiological processes, which need to be implemented in dynamic vegetation models to estimate future changes of the Amazon carbon sink. We also report recent results from the open-top chamber experiments on understorey saplings under rising CO2 and phosphorus fertilization, recently conducted at the AmazonFACE site. We give an overview over phosphorus uptake strategies and potential modelling approaches.
Development of actionable salt intrusion forecasts
Authors: Wullems Bas , Weerts Albrecht
Published: March 2022

We address the need for improved forecasts of saltwater intrusion in estuaries. Estuaries worldwide face problems with saltwater intrusion, which threatens the freshwater supply for drinking, agriculture and industry. The Rhine-Meuse delta is taken as a case study. This is a complex multi-branched system that is highly influenced by hydraulic management structures. Problems with saltwater intrusion occur regularly in this delta (e.g. 2003, 2005, 2006, 2011, 2013, 2018). These problems are most likely to occur when high sea levels due to storm swell coincide with low river discharge. We aim to provide water managers with better forecasts, so they can take mitigating measures in a timely fashion. Two modelling approaches will be investigated on how they can be applied to forecast salt intrusion on a timescale of days to weeks. These approaches are a machine learning model and several improvements (e.g. parameters, data assimilation, postprocessing) to the existing hydrodynamic SOBEK 1D model forecasts. In both approaches, the probabilistic nature of the input data will be processed to yield a probabilistic forecast of salt intrusion. Finally, we will test the developed models, or a combination thereof, in a scenario analysis of several water management decisions. The aim of this presentation is to exchange ideas on the various methods of (salt intrusion) forecasting, their advantages and limitations, and their application for deriving actionable forecasts.
A Novel Method for Natural Gas Hydrate Production: Depressurization and Backfilling with In Situ Supplemental Heat
Authors: Li Shouding , Zhang Zhaobin , Sun Yiming , Xu Tao , Li Xiao , Wang Sijing
Published: March 2022

Natural gas hydrate (NGH) is the most promising clean alternative energy resource for world. Based on the analysis of the bottleneck problems in hydrate recovery method, the achievement of reservoir-scale production of NGH by depressurization depend on three key factors, namely heat supply, reservoir stability and reservoir permeability. Based on the three principles of depressurization, in-situ supplemental heat and backfilling and increased permeability, the novel method, depressurization and backfilling with in-situ supplemental heat method was proposed. In this method, calcium oxide (CaO) powder is injected into the hydrate reservoir, which will provide a large amount of heat for the decomposition of NGH. At the same time, the Ca(OH)2 produced by the reaction will backfill the void volume left by hydrate decomposition and improve the permeability of the reservoir. The method is mainly implemented in three stages, i.e., horizontal well drilling and completion, powder injection and depressurization and backfilling. Currently, the two-dimension and three-dimension numerical simulations based on this novel method are completed. And the simulation results quantitatively verify the potential value of the depressurization and backfilling with in-situ supplemental heat method from the perspective of the theoretical calculation of numerical model. Based on the key procedures of this method, the related physical simulations for specific operating technique, such as CaO injection and corresponding production performance, are advancing. Combining above promising simulation results, this novel method is expected to be an effective hydrate recovery method.
Hillslope response to oscillating forcing
Authors: Godard Vincent , Tucker Gregory
Published: March 2022

Assessing rivers' and hillslopes' sensitivity to external forcing is paramount to understand landscape evolution, in particular as a response to Quaternary climate changes. River networks are usually considered to be the main conveyors of environmental signals, such as changes in precipitation, temperature, or baselevel. Yet because hillslopes provide the source of sediment for river networks, their response to environmental change  also  modulate landscape dynamics. In order to characterize such  behavior we analyse the response times of a transport-limited hillslope.
We use simple numerical models of denudation to study hillslope responses to oscillatory forcing and understand their filtering effects on  environmental signals. Modifications in the frequency of climate oscillation, such as the change that occurred at the Mid-Pleistocene Transition, can significantly modulate hillslope sediment-flux response. We infer a wide range of hillslope responses, ranging from negligible change over the full range of climate-forcing frequencies, to a significant filtering of long-period signals. 
Identification of the recharge zone using stable isotopes in the Salar de Atacama, Chile
Authors: Valdivielso Sonia , Vázquez-Suñe Enric , Herrera Christian , Custodio Emilio
Published: March 2022

In the peripheral aquifer of the Salar de Atacama, recharge is a key term of the water balance. This recharge is produced under arid conditions in the sub-basins surrounding the Salar and is dominated by medium salinity water due the intense evapo-concentration conditions. To solve the uncertainty in closing the water balance in the Salar de Atacama basin, this study aims to characterize the isotopic composition of precipitation, groundwater and surface water and to identify the recharge area. The results show that winter precipitation is more depleted in heavy isotopes, δ2H and δ18O, than summer precipitation. Surface water is evaporated and it has the same isotopic footprint as groundwater in each sub-basin, indicating that surface water runoff is a main recharge component. The meteoric source of surface and underground water in the basins of the Altiplano-Puna Plateau is isotopically lighter than the other waters found in the Salar de Atacama basin, although there is no significant transfer of isotopically lighter water to the peripheral aquifer of the Salar de Atacama from areas significantly outside the hydrographic basin.
A Buffer Gas Cooling experiment coupled to Cavity Ring Down Spectroscopy to explore complex spectra in the Near-Infrared range
Authors: Libert Alexis , Robert Séverine , Fabre Baptiste , Kassi Samir , Roucou Anthony , Glorieux Robin , Daman Marc , Vanlancker Guilhem , Hays Brian , Lauzin Clément
Published: March 2022

Buffer gas cooling relies on the thermalization of a buffer gas with a surface brought to cryogenic temperatures, which in turn thermalizes the target molecules through collisions. Because this process does not rely on any particular energy pattern, any molecule can be brought to the temperature of the buffer gas. Advantages of buffer gas cooling are numerous: it is a continuous source of slow laboratory frame velocities, allowing for long observation times. Moreover, in contrast to supersonic expansion, it does not require important pumping infrastructure because it relies on small gas throughput and cryogenic pumping (Changala et al., Appl. Phys. B 122 (2016) 292). Finally, buffer gas cooling is applicable to nearly all molecules and is very efficient in terms of sample density (Santamaria et al., ApJ 801 (2015) 50). The technique requires continuous injection of helium atoms and the species under study inside a vacuum chamber. We developed a cavity ringdown spectroscopy setup to seek the first cold molecules obtained with our apparatus.

One of our first molecular targets is a six-atoms asymmetric top molecule and the smallest molecule to present internal rotation: methanol (CH3OH).
The size of this molecule and the presence of this large amplitude motion lead to a dense and disordered rotational structure. This structure gets even more complicated when one goes up in energy with vibrational excitations. Due to its complicated spectrum, this molecule remains poorly known, especially in the NIR. This frequency range was recently explored by Svoboda et al. (Phys. Chem. Chem. Phys., 17 (2015) 15710), probing the 2ν1 vibration overtone around 7200 cm-1. In this report, the authors were able to assign on the order of a few percent of the observed lines. It thus seemed to be a promising candidate to challenge our ability to record and understand the spectral signature of large molecules in the overtone range using the cooling efficiency of the buffer gas cooling setup and the sensitivity of the cavity ringdown spectrometer.

The experiment and the spectra of CH3OH will be discussed. The floor will be open for discussion to identify new targets of astrophysical or atmospheric interest.
Climate model sensitivity to ice formation processes
Authors: Sotiropoulou Georgia , Broman Lina , Dej Dipanjan , Ekman Annica M. L. , Nenes Athanasios
Published: March 2022

Clouds remain among the largest sources of uncertainty in future climate projections. To accurately describe cloud radiative effects in models, an accurate description of the microphysical structure (the amount of liquid and ice) is required. Ice formation remains among the most poorly understood microphysical processes that profoundly impact clouds and their impact on climate. Ice formation at temperatures above -38oC can occur either (a) heterogeneously, with the assistance of aerosols that can act as ice nucleating particles or (b) through secondary ice production (SIP). The complexity of the heterogeneous nucleation parameterizations used in numerical models largely varies; some schemes simply diagnose ice formation depending on the thermodynamic conditions, while others explicitly predict ice from cloud-aerosol interactions. Secondary ice production is either not described in models or only accounts for one mechanism, which occurs at a limited temperature range: the Hallett-Mossop process. For this reason, the importance of SIP processes may be largely underappreciated and contribute to predictive uncertainty in climate models. In this study we use the Norwegian Earth System Model (version 2) to quantify the model sensitivity to (a) different heterogeneous nucleation schemes (diagnostic vs prognostic) and (b) the addition of missing key SIP mechanisms (collisional break-up and drop-shattering). The modeled cloud properties and radiation budget are evaluated against relevant global satellite datasets.
Reflections of ice penetrating radar from surface features
Authors: Helm Veit , Zeising Ole , Humbert Angelika
Published: March 2022

Surface features like supraglacial lakes and rivers may appear in radargrams as reflections at depth. Here, we simulate the propagation and reflection of a radar wave by assuming different reflectivity of water and ice. Our simulations represent AWI’s ultrawideband (UWB) radar, with a center frequency of 335 MHz and bandwidth of 340 MHz. Aim of the study is to better understand features in radargrams which are difficult to interpret.
First, we present a suite of artificial settings, like idealised lake geometries to infer a range of depth in which surface features may be found in radargrams. Next, we simulate real situations and compare those with radargrams from an airborne campaign over 79°N Glacier, Greenland, in July/August 2021. To this end, we classify dry/wet/water surfaces in Sentinel-2 data and use this for the simulation of the reflected power. For the surface classification, in addition to Sentinel-2, we also make use of the reflectivity detected by an airborne laser scanner, recorded synchronously with the UWB.
Multiple-pulse blue luminous events detected by ASIM
Authors: Li Dongshuai , Luque Alejandro , Lehtinen Nikolai G. , Gordillo-Vázquez Francisco  J. , Neubert Torsten , Lu Gaopeng , Chanrion Olivier , Zhang Hongbo , Østgaard Nikolai , Reglero Víctor
Published: March 2022

Narrow Bipolar Events (NBEs) are powerful radio emissions from thunderstorms, which sometimes occur isolated from lightning and at other times appear to initiate lightning. They are recently associated with Blue LUminous Events (BLUEs) on cloud tops and attributed to extensive streamer electrical discharges named fast breakdown, but their physics is not fully understood. Here, we analyse simultaneous observations of NBEs detected by radio receivers on the ground with their optical emissions observed by the Atmosphere-Space Interactions Monitor (ASIM) on the International Space Station (ISS). In this study, we focus on the multiple-pulse BLUEs that include one primary BLUE pulse and one or several subsequent BLUE pulses with a few millisecond intervals, as detected by a photometer at 337 nm. The observations indicate that the initial streamer discharge of an NBE is followed within a few milliseconds of horizontally oriented secondary streamer discharges at similar or higher altitudes but without triggering a leader process.
Insights from the LGBTQIA+ working group at EGU 2022
Authors: Bellomo Katinka , Di Chiara Anita , Rutter William A. J. , Davies Hannah Sophia , Prior-Jones Michael , Piispa Elisa Johanna , Muchow Marek , Beard Dylan Bodhi
Published: March 2022

Geoscientists identifying as LGBTQIA+ (Lesbian, Gay, Bisexual, Trans, Queer, Intersexual, Asexual, plus) are currently likely to face several more obstacles throughout their career compared to their cisgender/heterosexual colleagues. Additionally, they could experience the cumulative effect of an intersection of sexism, racism, and colonialism, if coming from one or more under-represented communities. With the aim to gather an EGU-based LGBTQIA+ group to coordinate and encourage a positive change within EGU and the broader geoscience community, a first social event was organized during the General Assembly (GA) in 2019, followed by a similar event during the GA in 2020 and 2021. Last year, the working group (WG) created a Discord forum to meet more frequently online and have a place for mutual support. The series of bottom-up initiatives - all community-driven -  aimed at raising awareness or promoting initiatives for changes. These have included thus far: gathering feedback, promoting initiatives toward the inclusion of LGBTQIA+ scientists in the EGU community, and doing research in general (i.e., conducting fieldwork as LGBTQIA+ individuals in locations where it can be considered more dangerous, due to the illegality of belonging to the LGBTQIA+ community). An additional task the WG has undertaken is to engage with the wider community via webinars and represent the WG in meetings with other stakeholders. The WG also works closely with the Equality, Diversity, and Inclusion (EDI) Committee of EGU for improving the representation and inclusion of their members at EGU and across the scientific organizations. In this presentation, we summarise our work since the last General Assembly and highlight areas where we hope to attract further support for institutional and cultural changes that will foster an inclusive culture for LGBTQIA+ geoscientists.