bluuebunny/crossref_metadata_2025 huggingface dataset:
Root hairs bridge the gap between roots and soil water
Authors: Duddek Patrick , Ahmed Mutez , Zarebanadkouki Mohsen , Koebernick Nicolai , Lovric Goran , Carminati Andrea
Published: March 2020

Although 40% of total terrestrial precipitation transits the rhizosphere, there is still substantive lack of understanding of the rhizosphere biophysical properties and their impact on root water uptake. Our hypothesis is that roots are capable of altering the biophysical properties of the rhizosphere and hereby facilitating root water uptake. In particular, we expect that root hairs maintain the hydraulic contact between roots and soil at low water potentials. We have recently shown that root hairs facilitate root water uptake in dry soils at high transpiration rates. Our explanation was that root hairs extend the effective root radius decreasing the flow velocity at the root surface and hence the drop in matric potential across the rhizosphere.

To test this hypothesis, we used synchrotron X-ray CT to image the distribution of root hairs in soils. The experiments were conducted with two maize genotypes (with and without root hairs) grown in two soil textures (loam vs sand). Segmenting the different domains within the high-resolution images enabled us to quantify the contact area of the root surface and root hairs with the soil matrix at different water potentials. Furthermore, we calculated the geodesic distance between the root and the soil matrix as a proxy of the accessibility of water to the root.

The results show that root hairs increase the total root surface by approx. 30% and the contact area with the soil matrix by approx. 40%. Furthermore, the average distance from the soil to the root surface decreases by approx. 40% due to hairs, which is the effect of root hairs preferentially growing through macropores. In summary, root hairs not only increase the root surface and the root-soil contact area, but also bridge the air-filled pores between the root epidermis and the soil matrix, thus facilitating the extraction of water.  On top of that, the segmented CT images are also the basis for image-based models aiming at quantifying root water uptake and the effect of root hairs.

 

 

References

(1) Koebernick N, Daly KR, Keyes SD, et al. 2019. Imaging microstructure of the barley rhizosphere: particle packing and root hair influences. New Phytologist 221, 1878–1889.

(2) Carminati A, Benard P, Ahmed MA, Zarebanadkouki M. 2017. Liquid bridges at the root-soil interface. Plant and Soil 417, 1–15.

 
Systematic hydrogeological conceptual model testing using remote sensing and geophysical data
Authors: Enemark Trine , Peeters Luk , Mallants Dirk , Batelaan Okke
Published: March 2020

Conceptual uncertainty is considered one of the major sources of uncertainty in groundwater flow modelling. In this regard, hypothesis testing is essential to increase system understanding by analysing and refuting alternative conceptual models. We present a systematic approach to conceptual model development and testing, which involves defining alternative models and then attempting to refute the alternative understandings using independent data. The method aims at finding an ensemble of conceptual understandings that are consistent with prior knowledge and observational data, rather than tuning the parameters of a single conceptual model to conform with the data through inversion.

The alternative understandings we test relate to the hydrological functioning of enclosed depressions in the landscape of the Wildman River Area, Northern Territory, Australia. These depressions provide potential for time-dependent surface water-groundwater interactions. Alternative models are developed representing the process structure and physical structure of the conceptual model of the depressions. Remote sensing data is used to test the process structure, while geophysical data is used to test the physical structure of the conceptual models.

The remote sensing and geophysical data are used twice in the applied workflow. First in a model rejection step, where models whose priors are inconsistent with the observations are rejected and removed from the ensemble. Then the data are used to update the probability of the accepted alternative conceptual models.

The updated conceptual model probabilities of the combined physical and process structures revealed the data indicated that the depressions act as preferential groundwater recharge features for three out of five depressions used as test case. For the fourth depression, the data is indecisive, and more testing would be needed to discriminate between model structures. For the fifth depression, all physical structures were rejected indicating that the model structure is still an unknown unknown.

This insight into system functioning gained from testing alternative conceptual models can be used in future modelling exercises. With more confidence in the conceptual model, confidence in the predictions of future modelling exercise increase, which can that underpin environmental management decisions.
Charcoals as archives of soils pyrogenic events
Authors: Golyeva Alexandra , Petrov Dmitry
Published: March 2020

The fires themselves have become important factor, which controls ecosystems, pedological processes and climate.

Our work are aimed as the decoding of the soil archives, which contain unique information about the direction and rates of the soil formation; the interactions between fire and vegetation composition and studying the long-term dynamics of vegetation.

The primary study objects are charcoal layers in pyrogenic soils, preserved in particular geomorphological traps of various karst landscapes in the North part of European Russia. Such layers, as pyrogenic archives are represented by several (up to dozens)  interlayers, that are separated by buried soil profiles.

The main method is pedoanthracological. About 100 charcoal particles from all interlayers in different podzol soils were studied. The age interval was between early Holocene and modern time.

Results. The bulk of all coals was represented by pine, the rest by spruce. Coals belonging to other tree species (for example, birch) were absent. That is, only indigenous coniferous forest always burned.

Conclusions. Over the entire period of soil and sediment formation, the vegetation cover in the region has not changed. It is possible that the time period required to restore indigenous forests and the chronology of the cyclicality of fires are interconnected.

The study was supported by the Russian Foundation for Basic Research. Project No. 19-23-05238.
Discriminating icequakes from volcanic seismicity at Cotopaxi volcano (Ecuador)
Authors: Battaglia Jean , Hidalgo Silvana , Helmstetter Agnes , Espín Cristian , Velez Luis , Cordova Marco , Proaño Antonio
Published: March 2020

Cotopaxi volcano (5,897 m) is located in Central Ecuador, 50 km south of Quito. It has a long eruptive history including more than 70 eruptions with an estimated VEI between 2 and 4 since 1534. Its last low magnitude eruption occurred in 2015. The summit of the volcano is covered by a glacier down to about 5000 m elevation. The volcano is monitored by the Instituto Geofísico (IG) whose monitoring network includes permanent seismic stations. The closest station to the summit (BREF) is located 1 km below the summit (2.2 km distance), about 400 m from the base of the glacier. It is used as a reference station by the IG to characterize the seismicity. The station records transient events related to volcanic activity such as Long Period (LP) and Volcano Tectonic (VT) events, as well as icequakes (IQ) issued from the neighboring glacier. IQs may have various origins including fracture propagation or opening, collapse of ice blocks, basal friction or forced water flow within the glacier. These signals may be difficult to distinguish from VTs or LPs.

We examined data from station BREF recorded between January 2013 and October 2018, with the aim of identifying families of characteristic similar events. We applied a 3-step procedure including: (1) an automatic detection of transient events, (2) a classification of the detected events into families of similar events and (3) a re-composition of the temporal evolution of the largest families using matched-filtering. This procedure outlines the presence of numerous families and points out 4 characteristic temporal evolutions with respect of the 2015 eruption. These evolutions allow to distinguish precursory LP events from background seismicity and outline the presence of long lasting families which may persist for years. We use amplitude ratios calculated between BREF and a station more distant from the summit to distinguish shallow families from deeper ones. We also locate sources of long-lasting families with a seismic antenna installed at the foot of the glacier from April to September 2018. Locations indicate shallow sources below the glacier corresponding to IQs. These results confirm that background seismicity close to the summit of Cotopaxi is dominated by IQs. Temporal evolutions of these families also suggest that the large (Mw=7.8) subduction earthquake which occurred near Pedernales on April 16, 2016, 250 km from the volcano, had a stronger influence on the glacier or its shallow substratum than the 2015 eruption.
1D and 2D Debris Flow Modeling with HEC-RAS
Authors: Sanchez Alejandro , Gibson Stanford , Ackerman Cameron , Floyd Ian
Published: March 2020

The Hydrologic Engineering Center River Analysis System (HEC-RAS) is a free software developed by the United States Army Corps of Engineers for simulating hydraulics, sediment transport, and water quality.  We present on the recent and ongoing developments of non-Newtonian flow and mobile bed modeling within HEC-RAS. The numerical models solve the in one-dimensional (1D) St. Venant equation, and the two-dimensional (2D) Diffusion Wave and Shallow Water Equations with corrections and modifications for non-Newtonian flows and steep slopes. The equations are solved using a combination of Finite-Difference and Finite-Volume methods on unstructured grids (for 2D). Several flow resistance laws are implemented including the Bingham, Coulomb, Herschel-Bulkley, and Voellmy models. Sediment transport is simulated in 2D with a total-load advection-diffusion model with corrections for steep slopes and high concentrations. A subgrid modeling approach is utilized for hydraulics and sediment transport, which allows for larger computational cells while maintaining accuracy. The numerical models have been verified with analytical test cases, and validated with small and large scale physical experiments and field applications. The results demonstrate the applicability of HEC-RAS as a tool for natural hazard studies involving non-Newtonian flows.
Water Quality Mixing Model (WQMM) for Environmental Flow Release Monitoring
Authors: Sentlinger Gabriel
Published: March 2020

Environmental Flow Release monitoring can be an expensive undertaking in active watercourses normally suitable for run-of-river hydropower projects.  In order to attain acceptable (<10%) uncertainty in the derived flow series, it is necessary for a Qualified Professional (QP) to make several site visits to measure a range of flows in order to calibrate a stage-discharge (rating) curve.  With climate change, the need to measure drought conditions and respond appropriately is crucial for habitat health and to prevent fish stranding.  The current study employs a Water Quality Mixing Model (WQMM) to estimate flows at a downstream site from an existing hydropower plant using a modified constant rate mixing model.  This is an independent estimate of flow entirely distinct from the stage-discharge curve.  The method can be employed anywhere there is a sufficient mixing length and sufficiently distinct WQ traits.  The method can reduce both maintenance costs and flow uncertainty where Environmental Flow Release Monitoring is required.
Magnetosheath kinetic structure: Mirror mode and jets during southward IP magnetic field
Authors: Blanco-Cano Xochitl , Preisser Luis , Rojas-Castillo Diana , Kajdic Primoz
Published: March 2020

Earth's magnetosheath is permeated by a variety of plasma waves, nonlinear structures and ion distributions.  Understanding solar wind interaction with Earth's magnetic field requires a detailed knowledge of the magnetosheath as the interface between both regions, including its kinetic micro-structure. In this work we study an extended interval (45 min) with southward magnetic field (Bz< 0) observed by MMS in the dayside magnetosheath. We use magnetic field and plasma data to study the properties of three transient enhancements in dynamic pressure identified as jets. We also calculate instability thresholds and investigate wave characteristics inside and outside of the jets. The characteristics of these jets are variable, which suggest different origins. While two of them can be classified as V-jets with large increment in velocity with almost no density increment the third one is an N-jet showing large enhancements in density with almost no velocity increment. The N-jet lasts seven times longer than the V-jets and occurs just at the region where the negative Bz becomes positive. Ion distributions inside the jets are more isotropic (Tperp ≈Tparallel) compared with the surrounding plasma where Tperp > Tparallel. FFT and minimum variance analysis show that fluctuations inside the N-jet tend to have larger transversal components, although they propagate at large angles to the background field. In contrast, waves in regions surrounding the jets are compressive and can be identified as elliptically polarized mirror mode waves. We have also show that the mirror instability threshold CM is positive inside these intervals.
Modern environment characterization of interdunal lakes in Inhambane province (SE Mozambique) as an analogue to understand past environmental changes
Authors: Gomes Ana , Connor Simon , Martins Maria João , Zinsious Brandon , Gonçalves Célia , Moura Delminda , Skosey-LaLonde Elena , Cascalheira João , Haws Jonathan , Nhanombe Judite , Raja Mussa , Fernandes Paulo , Mauelele Reginelinda , Matias Roxane , Oliveira Sónia , Costas Susana , Bicho Nuno
Published: March 2020

To better understand Quaternary environmental changes in Southeastern Mozambique and their role in human evolution, it is first necessary to characterized the modern environment of this area and the environmental drivers on their evolution. For this reason, an international and interdisciplinary team interpreted the Inhambane Province’s geology, hydrographic and tectonic maps and open-access satellite imagery and derived products (for morphometric analysis and landscape interpretation). Inhambane province is in a coastal plain composed of a Pleistocene dune system, within which many lakes can be found. Additionally, a comprehensive review of the existing research for the region was conducted, to choose the most suitable lakes from which to collect sediment records for paleoenvironmental reconstructions. The team carried out fieldwork during the summer of 2019 in four of the selected interdunal lakes (Muangue, Nyalonzelwe, Nhambutse and Chivanene). During fieldwork the vegetation cover and the land uses were carefully described, and the lakes water column parameters were measured. Additionally, in the two lakes that presented the longest sedimentological records (Muangue and Nyalonzelwe), an unmanned aerial vehicle (UAV) survey was carried out to create high resolution maps and elevation models of the lakes and their surroundings. UAV flights were carried out at 25 and 60 m height, with a front and side overlap between 60 to 70 %, using georeferenced Ground control points (GCPs). The lakes’ areas vary between 0.4 (Muangue) to 0.8 km2 (Chivanene). The longest sedimentological records were found in lakes with a water level 5 m above the Mean Sea Level (MSL) and surrounded by higher dunes (between 31 and 121 m elevation in relation to MSL). Most of the lake margins are used for agriculture, livestock and housing and some have fish farming. Regarding vegetation, between 16 families and 27 species were identified around Nhambutse and 27 families and 43 species around Muangue. The lakes’ maximum depths vary between 1 (Nhambutse) and 4.6 meters (Muangue). All lakes are freshwater except Nyalonzelwe, which is brackish. On average, surface water pH varies between 7.2 (Chivanene) and 9.12 (Nyalonzelwe). Surface water temperature varies between 25.03 (Nhambutse) and 26.6 ° C (Chivanene). All the collected data highlight the diversity of interdunal lake environments in the Inhambane Province, and how these environments may impact the sedimentological record. This work was supported by project PTDC/HAR-ARQ/28148/2017, funded by the Portuguese Foundation for Science and Technology.
Ground Motion Prediction Equations for shallow, small-magnitude events: application to the Mirandola-Cavone oil field
Authors: Venturini Elisa , Faenza Licia , Munafò Irene , Anselmi Mario , Zaccarelli Lucia , Garcia‐Aristizabal Alexander , Morelli Andrea
Published: March 2020

Ground motion prediction equations (GMPEs) based on data collected on hydrocarbon extraction areas have to deal with lower magnitude and smaller distances compared to the natural seismicity. This study focuses on the Mirandola-Cavone oil field located in the Po Plain (Northern Italy), an area that has been struck by the Emilia earthquake sequence in 2012.
We start with the compilation of a new homogeneous seismic catalogue, in terms of locations and moment magnitudes. The data come from the local network run by the industrial operator, integrated by the closest stations of the Italian seismic network managed by Istituto Nazionale di Geofisica e Vulcanologia.
Subsequently, we calculate the intensity parameters of interest (e.g., Peak Ground Acceleration, Peak Ground Velocity and spectral values) for the available set of about 250 earthquakes.
Lastly, we develop a functional form for the GMPE using software tools available at  IS-EPOS Platform, derived for the geometrical mean of the horizontal components of seismograms. The resulting attenuation curve is calibrated for magnitudes higher than 0.1 and distances up to 50 km, appropriate for monitoring local seismicity. This work represents the first attempt to construct the GMPEs for an oil field in Italy, starting from the raw data, in support to the Italian Guidelines for monitoring seismicity, deformation and pore pressure in hydrocarbon extraction areas.
Modeling earthquake numbers by Negative Binomial Hidden Markov models
Authors: Orfanogiannaki Katerina , Karlis Dimitris
Published: March 2020

Modeling seismicity data is challenging and it remains a subject of ongoing research. Assumptions about the distribution of earthquake numbers play an important role in seismic hazard and risk analysis. The most common distribution that has been widely used in modeling earthquake numbers is the Poisson distribution because of its simplicity and easy to use. However, the heterogeneity in earthquake data and temporal dependencies that are often present in many real earthquake sequences make the use of the Poisson distribution inadequate. So, we propose the use of a Hidden Markov model (HMM) with state-specific Negative Binomial distributions in which some states are allowed to approach the Poisson distribution. A HMM is a generalization of a mixture model where the different unobservable (hidden) states are related through a Markov process rather than being independent of each other. We parameterize the Negative Binomial distribution in terms of the mean and dispersion (clustering) parameter. Maximum likelihood estimates of the models’ parameters are obtained through an Expectation-Maximization algorithm (EM-algorithm).

We apply the model to real earthquake data. We have selected the area of Killini Western Greece to test the proposed hypothesis. The area of Killini has been selected based on the fact that in a time window of 17 years three clusters of seismicity associated with strong mainshocks are included in the catalog. Application of the model to the data resulted in three states, representing different levels of seismicity (low, medium, high). The state that corresponds to the low seismicity level approaches the Poisson distribution while the other two states (medium and high) are following the Negative Binomial distribution. This result complies with the nature of the data. The variation within each state that is introduced to the model by the Negative Binomial distribution is greater in the states of medium and high seismicity. 
The innermost ion radiation belts of Jupiter and Saturn
Authors: Kollmann Peter , Mauk Barry , Clark George , Paranicas Chris , Nenon Quentin , Shprits Yuri , Aseev Nikita , Ebert Rob W. , Kim Thomas , Roussos Elias , Haggerty Dennis , Rymer Abi M. , Sicard Angelica , Connerney John E. P.
Published: March 2020

The ion radiation belts just above the surface of the giant planets Jupiter and Saturn have recently been observed for the first time with Juno and Cassini. The relevant physical processes differ from Earth’s inner proton belt. Jupiter’s innermost ion belt consists of protons, oxygen, and sulfur ions. A comparison of Juno particle and plasma data with numerical modeling supports that these ions are occasionally transported from the magnetosphere across the main ring of Jupiter. It has been suggested earlier that this ring is populated through the stripping of energetic neutral atoms that are produced in the magnetosphere. This process is found to be too slow to populate the belt. After radial transport, the new ions lose energy in the tenuous ring halo inward of the main ring. This gives rise to an unusual spectral shape that rises from 100keV to 1MeV. Neutralization of the ions in the ring grains acts slower and eventually removes <100keV ions until the next transport across the ring.

Saturn’s innermost belt differs from Jupiter’s and Earth’s inner belts in the sense that Saturn’s rings are too dense and extended to allow radial transport of magnetospheric ions into the innermost belt. Saturn’s ion belts are therefore thought to be exclusively populated by cosmic ray tertiary particles from the CRAND process. While the source is different, the losses are similar as at Jupiter, namely interaction with the tenuous D-ring and the planetary exosphere. This interaction shows in the proton pitch angle distribution and has been used to constrain the scale height of Saturn’s exosphere that is difficult to do otherwise.
Uncertainty of precipitation reference dataset for climate change impact studies
Authors: Tarek Mostafa , Brissette François , Arsenault Richard
Published: March 2020

Abstract.

Climate change impact studies typically require a reference climatological dataset providing a baseline period to assess future changes.  The reference dataset is also used to perform bias correction of climate model outputs.  Various reliable precipitation datasets are now available over regions with a high-density network of weather stations such as over most parts of Europe and in the United States.  In many of the world’s regions, the low-density of observation stations (or lack thereof) renders gauge-based precipitation datasets highly uncertain.  Satellite, reanalysis and merged products can be used to overcome this limitation.   However, each dataset brings additional uncertainty to the reference climate. This study compares ten precipitation datasets over 1091 African catchments to evaluate dataset uncertainty contribution in climate change studies. The precipitation datasets include two gauged-only products (GPCC, CPC), four satellite products (TRMM, CHIRPS, PERSIANN-CDR and TAMSAT) corrected using ground-based observations, three reanalysis products (ERA5, ERA-I, and CFSR) and one merged product of gauge, satellite, and reanalysis (MSWEP).

Each of those datasets was used to assess changes in future streamflows. The climate change impact study used a top-down modelling chain using 10 CMIP5 GCMs under RCP8.5. Each climate projection was bias-corrected and fed to a lumped hydrological model to generate future streamflows over the 2071-2100 period. A variance decomposition was performed to compare GCM uncertainty and reference dataset uncertainty for 51 streamflow metrics over each catchment. Results show that dataset uncertainty is much larger than GCM uncertainty for most of the streamflow metrics and over most of Africa. A selection of the best performing reference datasets (credibility ensemble) significantly reduced the uncertainty attributed to datasets, but remained comparable to that of GCMs in most cases. Results show also relatively small differences between datasets over a reference period can propagate to generate large amounts of uncertainty in the future climate. 
A New Way of Understanding Rebound Phenomenon in Agriculture Water Demand Using A Global Sensitivity Analysis Approach
Authors: Ghoreishi Mohammad , Sheikholeslami Razi , Razavi Saman , Elshorbagy Amin
Published: March 2020

Effective use of water resources has been identified as a means to improve resilience to drought, particularly in the agricultural sector. In recent decades, the idea of shifting to more efficient irrigation systems (e.g., sprinkler irrigation systems) has received increasing attention to reduce the amount of water loss by traditional irrigation systems (e.g., flood irrigation systems), requiring considerable capital investments. However, there are indications that such investments do not lead to a reduction in water use in the long-run, which may even increase paradoxically; a phenomenon known as the rebound phenomenon or Jevon’s paradox. One of the fundamental information gaps concerns an explicit evaluation of coevolutionary dynamics and the interactions among socio-economic factors in the rebound phenomenon in agriculture, which calls for the application of systems-based methodologies such as global sensitivity (GSA) analysis methods to look at time-dynamical aspects of the coevolutionary dynamics between various factors influencing rebound phenomenon. In this study, we use a previously calibrated and validated Agent-Based Agricultural Water Demand (ABAD) model applied to the Bow River Basin in Alberta, Canada - home  to extensive irrigated farmlands with a history of drought experience. We perform a time dependent variance-based GSA on the ABAD model to examine the direct impact of factors as well as their joint inﬂuence due to interactions on rebound phenomenon. The overall findings show that the economic factors are the most important elements, which has an upward trend in the simulation time, in the rebound phenomenon. This finding is supported by the local observation as the net income of irrigated land has an upward trend in this time period. In addition, although the individual effect of the factor representing the social interaction among farmers is less important compared to the irrigation expansion factor, its total-order effect (i.e., the total contribution of a single factor including interactions with all other factors) becomes more important indicating the significant interactions among model factors. This analysis provides a deeper understanding of the coevolutionary dynamics of the rebound phenomenon and paves the way for better management of water resources.
Soil organic amendments for restoring degraded drylands: strategies, recommendations and challenges for large-scale application
Authors: Hueso-Gonzalez Paloma , Muñoz-Rojas Miriam
Published: March 2020

Soil is an essential and non-renewable resource in natural and agricultural ecosystems with extremely slow formation and regeneration potential. In dryland areas, many ecosystems are being seriously affected by degradation processes because of an excessive use of agro-chemicals, deep tillage and intensive irrigation, among many other factors. The decline in soil organic matter is also becoming a major cause of soil degradation, particularly in dryland regions where low soil fertility cannot always maintain a sustainable production. The use of organic amendments in ecosystem restoration programs can be an effective technique for promoting soil restoration processes in degraded drylands and several studies have shown their beneﬁts for improving soil physical, chemical and biological properties. This recovery is a result of the rapid increment of organic matter and clay contents in the soil in the short term. In the long-term, soil structure becomes more stable and water holding capacity, permeability and infiltration are improved, whereas surface runoff and erosion are reduced. Nevertheless, there are many research gaps in the knowledge of the effects of climatic conditions on their application, as well as the adequate types of amendment and doses and decomposition rates. In this presentation, we evaluate the role of organic amendments as an effective strategy in dryland restoration, highlighting the effects of different amendment types, doses and application rates. We will speciﬁcally address: (1) type of amendments and beneﬁts arising from their use, (2) application methods and more appropriate doses and, (3) potential risk derivates for their application. We also showcase some recent case studies using organic amendments in degraded dryland areas from Spain and Australia.
The temporal evolution of syn-sedimentary normal faults and the possible role of tip retreat
Authors: Lathrop Bailey , Jackson Christopher , Bell Rebecca , Rotevatn Atle
Published: March 2020

We need to understand how normal faults grow in order to better determine the tectono-stratigraphic evolution of rifts, and the distribution and size of potentially hazardous earthquakes. The growth of normal faults is commonly described by two models: 1) the propagating fault model (isolated growth model), and 2) the constant-length model. The propagating fault model envisages a sympathetic increase between fault lengthening (L) and displacement (D), whereas the constant-length model states that faults reach their near-final length before accumulating significant displacement (Walsh et al., 2002). Several relatively recent studies agree that faults generally follow a constant-length model, or a “hybrid model” of the two, where most faults reach their near final length within the first 20-30% of their lives, and accrue displacement throughout. Furthermore, in the past 20 years, much research has focused on how faults grow; relatively few studies have questioned what happens to the fault geometry as it becomes inactive, i.e. do faults abruptly die, or do they more gradually become inactive by so-called tip retreat. We here use a 3D seismic reflection dataset from the Exmouth Plateau, offshore Australia to support a hybrid fault growth model for normal faults, and to also determine the relationship between length and displacement as a fault dies. We show that the studied faults grew in three distinct stages: a lengthening stage (<30% of the faults life), a displacement accrual stage (30-75%), and a possible tip retreat stage (75%-end). This work has important implications in our understanding of the temporal evolution of normal faults, both how they grow and how they die.
Summer N₂O dynamics in the western Arctic Ocean : Distributions, Processes, and Fluxes
Authors: Kim Seong-Su , Kang Sung-Ho , Yang Eun Jin , Kim Il-Nam
Published: March 2020

We collect seawater samples from 32 stations for N2O analysis between August 6 and August 25, during 2017 ARA08B cruise in western Arctic Ocean (WAO), covering from Southern Chukchi Sea (SC) to Northern Chukchi Sea (NC). At surface depth (~50 m), N2O concentrations were 10.9‒19.4 nmol L-1, and distinct pattern was observed between SC and NC. N2O concentrations were increased from surface to bottom (~50 m) at SC, corresponding to positive relationship of ∆N2O (N2Omeasured - N2Oequilibrium) with DIN (NO3­- + NO2-) and negative relationship between ∆N2O and N*. It suggests that nitrification and denitrification are the main processes to produce N2O at SC. On the other hand, N2O concentration at NC increased from the south to north, and remained vertically constant. It may be the result of physical processes such as dilution by sea ice melting water, and high solubility that affected by low temperature and low salinity. The highest N2O concentrations were observed at intermediate depth (50‒200 m), ranging 13.4‒21.9 nmol L-1. It would be determined by high solubility and active biogeochemical processes synthetically. Concentrations of N2O were rapidly diminished to 400 m, ranging 10.2‒14.1 nmol L-1, and did not be remarkably altered under 400 m, ranging 11.3‒13.7 nmol L-1. It might be affected by advection of Atlantic Water (AW) and existence of Arctic Bottom Water (ABW), and influence of biogeochemical processes was negligible at deep and bottom depth (below 200 m). N2O flux was calculated to determine that the WAO is sources or sinks region for atmospheric N2O. Positive N2O flux was observed at SC, and it indicate that N2O gas is released to atmosphere at SC. Negative value of N2O flux at NC suggest that atmospheric N2O is absorbed into NC. Furthermore, positive relationship of N2O flux with environmental parameters (temperature, salinity, and ∆N2O) also observed in WAO. These results provide comprehensive information of the spatial N2O distribution and main processes which decide N2O distribution in WAO, and also suggest that air-sea N2O flux could be affected by changing environments of the Arctic Ocean.
Interaction among biogenic, climate and tectonic processes influences tufa precipitation, Araripe Basin, Brazil
Authors: Lopes Diniz Jaqueline , Wohnrath Tognoli Francisco Manoel , Siqueira de Miranda Tiago , Nóbrega Sial Alcides , Vieira de Souza Laís , Campos Inocêncio Leonardo , Bonato Juliano , Modica Custódio Caroline , Spaniol Aline Fernanda
Published: March 2020

Tufas are continental freshwater carbonates common in epi-karst zones. They are composed of micrite and microsparitic crystals of calcite with variable primary moldic and fenestral porosity and with the frequent presence of biogenic content. By definition, tufa petrogenesis depends on climate processes and usually has precipitation induced by biological activity. Our examples include two morphotypes resulting from weathering of limestone of the Crato Formation, Araripe Basin, NE Brazil, and precipitated along vugular fractures. To understand how the climate and the biological activity act on precipitation of these rocks, we integrate structural data, petrography, and δ18O and δ13C values. Tufas are always associated with joints and faults in the northern boundary of the basin. The block where tufas occur has a dip angle between 5º and 30º, which differs from the regional average of 0° to 3º. The tufas fill vugular steep fractures with preferential planes oriented N50E and N30W and have a pipe-shaped growth pattern with top-down and center-out growth direction. The presence of organic filaments and mollusk shells are recurrent in all samples. Isotopic values measured on 32 samples indicate δ18O VPDB between -11,4‰ and -1,7‰ and δ13C VPDB between -12,1‰ and -5,1‰. The enrichment of 16O reveals the composition of meteoric water, responsible by the limestone dissolution and tufa precipitation. Organic fractioning induced by photosynthesis of the C4 plants result in 12C enrichment in the tufas. Macro and microscopic analysis revealed bryophyte filaments. Moreover, the porosity pattern strongly evidences the presence of these plants in tufa diagenesis. The close association of these rocks with the boundary faults suggests a relationship with climate denudation processes. The Araripe Basin is part of a set of continental rift basins in the Brazilian Northeast affected by uplifting. Thus, there are two stages recognized; the first one corresponds to the exhumation and reworking of the basement, probably in the early Cenozoic; and in the second stage a more intense weathering under semi-arid climate during Oligocene, or later.
CH4 variability over India derived from the GOSAT/TANSO-FTS TIR observations and simulated by MIROC4-ACTM model
Authors: Belikov Dmitry , Saitoh Naoko , K. Patra Prabir , Chandra Naveen
Published: March 2020

We examine CH4 variability over different regions of India and the surrounding oceanic regions using thermal infrared (TIR) band observations by the Thermal And Near-infrared Sensor for carbon Observation-Fourier Transform Spectrometer (TANSO-FTS) onboard the Greenhouse gases Observation SATellite (GOSAT) and simulated by the updated MIROC4.0-based Atmospheric Chemistry Tracer Model (ACTM) for the period 2009-2014. GOSAT TIR provides data coverage and density captures detailed features of CH4 distributions at height levels from the top of the boundary layer to the upper troposphere even in the cloudy conditions, which is very common for the region with a monsoon climate. Analysis of transport and emission contributions to CH4 variabilities suggests that the CH4 seasonal cycle over India is controlled by the heterogeneous distribution of surface emissions under the influence of the monsoonal divergent wind circulations. Distinct seasonal variations of CH4 are observed over northern and southern regions of India corresponding to the southwestern monsoon (July–September) and early autumn (October–December) seasons. In summer, three principal circulations pumping CH4 upward over South Asia: the lateral (the cross-equatorial circulation) and transverse (flows between the arid regions of North Africa and the Near East and South Asia) monsoons, and the Walker Circulation extends across the Pacific Ocean. GOSAT TIR derives CH4 profiles due to retrieval of signal from 22 vertical levels. In general, the mean ACTM (no averaging kernel incorporated)-GOSAT misfit is within 50 ppb, excepting the level of 150 hPa and upward, where the GOSAT TIR sensitivity becomes too low. Due to the use of MIROC4.0 AGCM performance of ACTM in the upper troposphere and lower stratosphere has been improved. The GOSAT-ACTM misfit above the level of 150 hPa is likely to arise from a priori model for TIR retrievals. Convolution of the modeled profiles with retrieval a priori and averaging kernels reduces the misfit to below uncertainty. However, the weight of the a priori profiles becomes too large with such smoothing. Overall, the ACTM simulations of CH4 in the Indian regions compare favorably with the GOSAT TIR samplings, in terms of seasonality and regional variability. However, the GOSAT-ACTM inconsistencies indicate opportunities for further flux optimization and emission uncertainty reduction by inverse modeling methods.
A Global Assessment of Non-Stationarity in Extreme Precipitation
Authors: Sheikholeslami Razi , Papalexiou Simon Michael , Clark Martyn
Published: March 2020

Rapid urban development, along with human modifications in river discharge (both frequency and magnitude) increase the need to design safe and resilient infrastructure. In addition, continental-domain studies show that there are significant changes in the intensity and frequency of the extreme rainfall events. Importantly, Earth System Models predict that these changes will continue to grow in the future. Consequently, flood frequency from heavy precipitation events is expected to increase, thereby threatening human society and the environment. Therefore, the stationary climate assumption — the idea that the future variability of the system will remain within the limits observed in the past record — may not be valid and should be carefully examined. Despite the existing awareness of potential non-stationarity, there has been a limited research on analysis of non-stationary of extreme precipitation at the global scale. This motivated us to conduct a comprehensive global study to compare the performance of non-stationary and stationary models in describing precipitation extremes.
The May 7 - 11, 2016 Earthquake Sequence at Rivera Fault Zone
Authors: Nunez-Cornu Francisco J , Cordoba Diego , Bandy William L , Dañobeitia Juan José , Mortera-Gutierrez Carlos , Alarcon Edgar , Nuñez Diana , Quinteros-Cartaya Claudia B , Suarez-Plascencia Carlos
Published: March 2020

The geodynamic complexity in the interaction between Rivera, Cocos and NOAM plates is mainly reflected in the high and not well located seismicity of the region. In the framework of TsuJal Project, a study of the passive seismic activity was carried out. A temporal seismic network with 25 Obsidian stations with sensor Le-3D MkIII were deploying from the northern part of Nayarit state to the south of Colima state, including the Marias Islands, in addition to the Jalisco telemetric Seismic Network, being a total of 50 seismic stations on land. Offshore, ten Ocean Bottom Seismographs type LCHEAPO 2000 with 4 channels (3 seismic short period and 1 pressure sensors) were deployed and recover by the BO El Puma from UNAM in an array from the Marias Islands to off coast of the border of Colima and Michoacan state, in the period from 19th April to 7th November 2016.

A seismic sequence started on May 7, 2016 with an earthquake Mw = 5.6 reported by CMT-Harvard, USGS and SSN at the area north of Paleo Rivera Transform fault and west of the Middle America Trench, an area with a very complex tectonics due to the interaction of Rivera, Cocos and NOAM plates.

An analysis of this earthquake sequence from May 7 to May 11 using data from OBS and adequate P-Wave velocity model for Rivera plate is presented, 87 earthquakes were located. Data from onland stations were integrated after a travel-time residual analysis.

We observed that the new location is about 50 km southwest direction, from previous one, between the Paleo Rivera Transform fault and the northern tip of the East Pacific Rise – Pacific Cocos Segment.  This area has a different tectonic stress regime.
The reliability of radiocarbon dates of different carbon fractions in the Australian tropical savannas: A case study from Sanamere Lagoon, northeast Australia
Authors: Rivera-Araya Maria , Bird Michael , Rowe Cassandra , Ulm Sean , Levchenko Vladimir
Published: March 2020

The selection and pre-treatment of a reliable organic fraction from which to acquire radiocarbon dates is fundamental to obtain accurate chronologies. Sampling from tropical lakes is particularly challenging given the adverse preservation conditions and diagenesis in these environments. Our research is the first to examine and quantify the differences between the radiocarbon date results from different carbon fractions and pretreatments from the same depths from a tropical lake sediment core (1.72 m long) located in north Australia to assess which one(s) are more reliable. Six different organic fractions (bulk organics, pollen concentrate, cellulose, stable polycyclic aromatic carbon (SPAC), charcoal >250 um and charcoal >63 um), for a total of 27 radiocarbon dates, were compared in six different depths along the core. Acid-base-acid (ABA), modified ABA (30 % hydrogen peroxide + ABA), 2chlorOx (a novel cellulose pre-treatment method) and hydrogen pyrolysis (hypy) were used to pre-treat the correspondent organic fractions. The oldest date is 31,295 calibrated years before present (cal yr BP) and the youngest is 2,048 cal yr BP, spanning 29,247 years. The smallest offset between the minimum and the maximum age in a given depth was found to be 975 years (between SPAC and charcoal >63 um) and the largest 16,527 years (between pollen concentrate and SPAC). The SPAC fractions pre-treated with hypy consistently yielded older ages compared to all other fraction in most cases, while bulk organics yielded consistently younger ones. The magnitude and consistency of the offsets and the physical and chemical properties of the tested organic fractions suggest that SPAC is the most reliable fraction to date in tropical lake sediments and that hypy successfully removes contamination sourced from exogenous carbon.
Identification of Engineering Bedrock in Taiwan based on Site Amplification and Velocity Structures of Strong-motion Stations
Authors: Lin Che-Min , Huang Jyun-Yan , Kuo Chun-Hsiang , Wen Kuo-Liang
Published: March 2020

There are two kinds of bedrocks that are widely used in seismology and earthquake engineering respectively. The seismology field uses the “seismic bedrock” to define an interface that has a practically lateral extent. The strata deeper than this interface is much more homogeneous in comparison with the shallower one. It is common to set the seismic bedrock within the upper crust has 3000 m/sec of the shear wave velocity. In contrast, the earthquake engineering prefers the shallower interface which dominates the main seismic site amplification, especially the predominant frequency of ground motion. The interface is called “Engineering Bedrock”, which the underlying stratum has the shear wave velocity from 300 to 1000 m/sec for different purposes. But, the reference shear wave velocity of the engineering bedrock is mostly defined as 760 m/sec for ground motion prediction and simulation. In Taiwan, the Central Weather Bureau (CWB) constructed and operates a dense strong-motion network called TSMIP (Taiwan Strong Motion Instrument Program), which provides numerous ground motion data for seismology and earthquake engineering. In our previous studies, the shallow shear wave velocity profiles of over 700 TSMIP stations were estimated by the Receiver Function method. The velocity profiles are from the ground surface to the depth with the shear wave velocity of at least 2000 m/sec. It allows us to compare the theoretical site amplification of the velocity profile of TSMIP stations with their observed one from the seismic records. The variance of fitness between theoretical and observed amplifications through shear wave velocity is analyzed to evaluate which reference velocity can appropriately define the depth of engineering bedrock, where the most site amplification occur beneath, in all of Taiwan. The difference between local geology is also discussed. Finally, an engineering bedrock map is proposed for further applications in earthquake engineering.
Impacts of Variable Climate and Effluent Flows on the United States-Mexico Transboundary Santa Cruz Aquifer
Authors: Tapia Elia , Shamir Eylon , Megdal Sharon
Published: March 2020

The Transboundary Santa Cruz Aquifer (TSCA) is located in Northwestern Mexico and Southwestern United States (U.S.). Groundwater from the transboundary aquifer is being shared by the states of Arizona in the U.S. and Sonora in Mexico; particularly by the cities of Nogales, Arizona and Nogales, Sonora. The Arizona-Sonora border region is subject to climate uncertainties, limited water availability, and water quality issues. The objective of this study is to assess the impacts of changes in groundwater demand, effluent discharge, and climate uncertainties within the TSCA. Groundwater recharge in the TSCA is highly sensitive to climate uncertainties and physical water and wastewater transfers from both the U.S. and Mexico. Perennial flows in the area depend on the effluent discharges from both the U.S. and Mexico. Population growth and residential construction have increased groundwater demand in the area, in addition to wastewater treatment and sanitation demands. These human activities, coupled with climate uncertainties and possible reductions to effluent discharge, influence the hydrology of the area. We use a conceptual water budget model to analyze the long-term impact of the different components of potential recharge and water losses within the aquifer, including changes in projected climate that are based on three downscaled CMIP5 RCP8.5 Global Climate Models. Water budget model simulations for most effluent discharge and groundwater pumping scenarios reflected groundwater deficit. Additionally, climate projections showed variations that range from severe long-term drying to positive wetting. This research improves the understanding of the impact of climate uncertainties and water management decisions on water sustainability, with an accessible methodology that can be globally applied.