bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermochronology and REE analyses as new tools to track thermal anomaly and fluid flow along a crustal scale fault (Têt fault, French Pyrenees)
Authors: Milesi Gaétan , Patrick Monié , Münch Philippe , Soliva Roger , Mayolle Sylvain , Taillefer Audrey , Bruguier Olivier , Bellanger Mathieu , Bonno Michaël , Martin Céline
Published: March 2020

The Têt fault is a crustal scale major fault in the eastern Pyrenees that displays about 30 hot springs along its surface trace with temperatures between 29°C and 73°C. The regional process of fluid circulation at depth has previously been highlighted by thermal numerical modelling supported by hydrochemical analyses and tectonic study. Numerical modelling suggests the presence of a strong subsurface anomaly of temperature along-fault (locally > 90°C/km), governed by topography-driven meteoric fluid upflow through the fault damage zone (advection). On the basis of this modelling, we focused our thermochronological study on 30 samples collected close and between two hot spring clusters in both the hanging wall and the footwall of the Têt fault, where the most important thermal anomaly is recorded by models. We analysed apatite using (U-Th)/He (AHe) dating combined with REE analyses on the same dated grains.

Along the fault, AHe ages are in a range of 26 to 8 Ma in the footwall and 43 and 18 Ma in the hanging wall, and only few apatite grains have been impacted by hydrothermalism near the St-Thomas hot spring cluster. By contrast, particularly young AHe ages below 6 Ma, correlated to REE depletion, are found around the Thuès-les-bains hot spring cluster. These very young ages are therefore interpreted as thermal resetting due to an important hydrothermal activity. A thermal anomaly can be mapped and appears restricted to 1 km around this cluster of hot springs, i.e. more restricted than the size of the anomaly predicted by numerical models. These results reveal that AHe dating and REE analyses can be used to highlight neo- or paleo-hydrothermal anomaly recorded by rocks along faults.

This study brings new elements to discuss the onset of the hydrothermal circulations and consequences on AHe and REE mobilisation, and suggest a strong heterogeneity of the hydrothermal flow pattern into the fault damage zone. Moreover, this study suggests that crustal scale faults adjacent to reliefs can localise narrow high hydrothermal flow and important geothermal gradient.  Besides these results, this study provides new constraints for geothermal exploration around crustal faults, as well as a discussion on the use of thermochronometers into fault damage zones. 
Learning from mistakes: Online updating for deep learning models.
Authors: Klotz Daniel , Kratzert Frederik , Sampson Alden K. , Klambauer Günter , Hochreiter Sepp , Nearing Grey
Published: March 2020

Accurate streamflow forecasts are important for many operational purposes, like hydropower operation or flood risk management. It is obvious that for data-driven models best prediction performance would be obtained if recent streamflow observations were used as an additional model input. Therefore, there exists a certain imperative which demands to use forecasting models that use discharge signals whenever available.

 

Forecasting models are, however, not well suited when continuous measurement of discharge can not be guaranteed or for applications in ungauged settings. Regarding the former, missing data can have long lasting repercussions on data-driven models if large data-windows are used for the input. Regarding the latter, data-driven forecast models are not applicable at all. Additionally, we would like to point out that data-driven simulation models need to represent the underlying hydrological processes more closely since the setup explicitly reflects the rainfall-runoff relationship. To conclude, in many contexts, it is more appropriate to use process or simulation models, which do not use discharge as input.

 

Despite the above mentioned difficulties of forecasting models it would nevertheless be beneficial to integrate, whenever available, past runoff information in simulation models in order to improve their accuracy. To this end, multiple potential approaches and strategies are available. In the context of conceptual or physically based rainfall-runoff models, recent runoff information is usually exploited by data assimilation/updating approaches (e.g. input-, state-, parameter- or output-updating). In this contribution we concentrate on input-updating approaches, since it allows to adjust the system for a forecasting period even if no explicit process can be attached to the system states.

 

We propose and examine different input-updating techniques for DL-based runoff models that can be used as baselines for future studies on data-assimilation tasks and which can be used with arbitrary differentiable model. To test the proposed approaches, we perform a series of experiments on a large set of basins throughout the continental United States. The results show that even simple updating techniques can strongly improve the forecasting accuracy.   

 
Analysis of plant water stable isotopes using the water-vapor equilibrium method
Authors: Stockinger Michael , Santos Pires Sabrina , Stumpp Christine
Published: March 2020

Plant water stable isotopes (δ18O, δ2H) have been used in eco-hydrological, biogeochemical and hydrological studies to e.g., quantify terrestrial water fluxes or to determine plant water sources. Current plant water extraction methods for isotope measurements are either expensive, labor-intensive or can lead to isotopic fractionation. Recent studies employed a new, extraction-free measurement method that was originally developed for the analysis of isotopes in sediment pore water: the water-vapor equilibrium method. It still needs to be tested if this method can be reliably used for isotope analysis of plant samples and how to best prepare the samples. Therefore, we investigated the effects of various preparation steps when measuring the plant water stable isotopes using this new method. We chose tomato and strawberry plants and prepared roots, shoots, leaves and fruits by either grinding or cutting them into pieces. Further, the necessary sample amount and the effect of equilibration time was evaluated. We investigated the effect of the preparation steps on mean values, standard deviations and a measurement device-specific value (LWV) that indicates a negative impact of volatile organic compounds (VOC) on reported isotope values. Results showed that an equilibration time longer than 24 hours is not advisable as the relationship between δ18O and δ2H of all plant samples worsened with R² declining from 0.97 to a minimum of 0.16. Additionally, the LVW indicated the influence of VOC with progressing equilibration time. Optimum amounts of plant material for roots were 3 g while for all other plant parts 5 g was necessary. In contrast to cut samples, kinetic fractionation effects were observed for grinded samples which could also be apparent fractionation effects because of the observed changes in LWV indicative of VOC interferences. For both plants the successive enrichment of the irrigation water from roots to leaves was observed. Fruits showed differences in their isotopic composition of the water stored inside the fruit compared to the water in the skin, with the inside water closer to the applied irrigation water. The intersection of the dual-isotope plot of all measured plant samples with the local meteoric water line was close to the applied irrigation water, making it theoretically possible to acquire information about the plant source water and enrichment factors in future studies when using the water-vapor equilibration method. From the findings of this study protocols can be established for sample preparation and plant water stable isotope analysis using the water-vapor equilibrium method.
Impacts of water resources management on the North China Plain revealed in multi-mission earth observation datasets
Authors: Liu Jun , Jiang Liguang , Bandini Filippo , Zhang Xingxing , Bauer-Gottwein Peter
Published: March 2020

The natural conditions of surface water bodies and groundwater aquifers in many densely populated river basins have been altered in order to satisfy various human water demands, such as drinking water supply, irrigation, power generation and navigation. The North China Plain (NCP) accounts for about 24% of the country's population, and the huge water demand makes it one of the regions with the strongest artificial intervention in the water cycle. China has promoted the South-to-North Water Diversion (SNWD), which diverts surplus water from the Yangtze River Basin to the water-deficient North. Since the central line project of SNWD has become fully operational in 2014, more than 16 km3 of water have been supplied to the NCP, which has had a significant impact on water resources in the regions along the route. Monitoring the recent dynamics of surface and sub-surface water storage is essential for water resources management and sustainable use of ongoing and forthcoming SNWD water transfers. Multi-mission satellite earth observation methods provide timely and spatially resolved datasets for monitoring inland water bodies, which have been validated over the last two decades. In this study, first, we evaluate the influence of SNWD on the Terrestrial Water Storage (TWS) monitored by the Gravity Recovery and Climate Experiment (GRACE) and its follow-on mission (GRACE-FO) over the NCP. The results indicate that the significant downward trend during 2002 – 2014 period, has stopped in the past 5 years, since the implementation of the central line project of SNWD. Second, Sentinel-3 radar altimetry and Sentinel-1 SAR missions were used to monitor the water surface extent and water surface elevation of surface water bodies. Sentinel-1 with its newly available Synthetic Aperture Radar (SAR), high spatial resolution and short temporal baselines shows potential for monitoring surface water area variations. Sentinel-3 benefits from the new Sentinel Ku/C Radar Altimeter (SRAL) and a modified on-board tracking system and shows great potential for monitoring inland water surface elevation (WSE) variations for several large and medium reservoirs and canals in this region. We show that, along with other policy measures, the SNWD transfers have had a significant impact on the water balance of the NCP region as evident from multiple satellite earth observation missions.
Indian Monsoon Rainfall Variability and associated Climatic forcings in the last two millennia inferred by a Stalagmite from the peninsular India
Authors: Gandhi Naveen , Reddy A. Phannindra , Krishnan Raghavan , Yadava Madhusudan G.
Published: March 2020

We present high temporal (near-annually) resolved δ18O values from absolutely dated stalagmite record that represents the Indian Summer Monsoon (ISM) rainfall variations for the Indian subcontinent spanning from 207 AD to 2014 AD. This rainfall reconstruction shows ISM varaitions for four major global climatic periods viz., Roman Warm Period (RWP), Dark Ages Cold Period (DACP), Medieval Warm Period (MWP) and Little Ice Age (LIA). Cave records from different patrs of the sub-continent synchronously show enhanced precipitation during DACP. This wet period was forced by Solar-induced El-NiNo Southern Oscillation (ENSO) and Tibetan Plateau Temperature. Cliamtic conditions were wetter during LIA than that during MWP, as the former witnessed more number of wet monsoon years. However, MWP witnessed the strongest and the weakest monsoon years in the last two millennia. The direct influence of Soalr activity on the position of Inter Tropical Convergance zone (ITCZ) might have caused the observed ISM variability of MWP. Altough ISM shows largest variability during MWP, the overall monsoon state was moving towards wetter conditions, forced by ENSO. Solar induced forcings on ENSO influenced ISM during LIA. Our results suggest of non-stationary dynamical forcings over ISM during different periods in the last two millennia.
The relevance of climate information in the assessment of flood regulating ecosystem services
Authors: Wübbelmann Thea , Bender Steffen , Burkhard Benjamin
Published: March 2020

Extreme weather events, failure of climate-change mitigation and adaptation, and biodiversity loss and ecosystem collapse are some of the main global risks. Climate change is one of the major drivers for ecosystem and biodiversity loss as well as for higher frequency and intensity of natural disasters and extreme weather events. Consequently, ecosystem health and the provision of ecosystem services (ES) is affected by the increasing pressures.

However, the provision of ecosystems must be ensured in order to guarantee and maintain human well-being. To define the benefits that people obtain from ecosystems there exist the concept of ES that links social and environmental systems to achieve sustainable use and discover trade-offs between different ES.

With respect to the increasing number of flood events (pluvial and fluvial) and of affected persons in the last years, one important key ES under external pressure is flood regulation. It describes the capacity to reduce flood hazards. Amongst other factors, climate change has a high impact on flood characteristics. Currently, most studies analyse the present status of flood regulating ES. Changing climate conditions and associated functionalities of the flood regulating ES are mostly not taken into account. This study shows the importance of assessing the current and future functionalities of flood regulating ES. In order to adapt ecosystems and their functionalities to projected climate impacts, it is important to consider regional climate information in the estimation process for flood regulating ES.
Influence of salinity gradient on Ni complexation by Fluorescent Dissolved Organic Matter (FDOM) and dispersal across estuaries in New Caledonia
Authors: Dupouy Cécile , Juillot Farid , Lemonnier Hugues , Bessard Marie , Jamet Leocadie , Boher Laura , Mounier Stephane
Published: March 2020

Dissolved organic matter (DOM) is ubiquitous in the environment. Its composition and properties depend on water type (freshwater, estuarine, brackish, marine) and are influenced by the geological nature (ultramafic, volcano-sedimentary, metamorphic) and occupancy (mangrove, forest, agriculture, urbanized) of the upstream catchment. Due to its capacity  to form complexes with dissolved trace metals, DOM can render them hardly available to living organisms, and thus limit their toxicity. Considering its capacity to be transported on large distances, DOM can significantly contribute to the dispersal of trace metals in aquatic ecosystems. In this study, we used 3D fluorescence spectroscopy to characterize the actual nature of FDOM (a fraction of DOM that shows specific fluorescence properties) across estuaries downstream of two contrasted catchments (ultramafic vs. volcano-sedimentary) in New Caledonia. In a first step, Excitation-Emission Matrix (EEM) were obtained on 0.2 µm filtered water samples and a parallel factor analysis (PARAFAC) allowed to identify the different FDOM components in the two catchments. These data indicated a dramatic decrease of all components as a function of increasing salinity, with a threshold value around 25 g/L whatever the catchment. This trend is considered to reflect an aggregation-flocculation behavior of FDOM across the salinity gradient of the studied estuaries. In a second step, fluorescence quenching experiments emphasized the complexing capacity of the different components toward dissolved Ni. FDOM might thus play a significant role on Ni dispersal in aquatic ecosystems through the formation of FDOM-Ni complexes. However, this dispersal capacity might be hampered in estuaries due to the suspected aggregation-flocculation behavior of FDOM across the salinity gradient. Rather than the geological setting of the upstream catchment, salinity appears thus as the major driver of Ni dynamics across estuaries through FDOM-Ni complexes.
Network scale sediment connectivity to explore stability and resilience of channel forms and river types in the Vjosa basin
Authors: Tangi Marco , Bizzi Simone , Castelletti Andrea
Published: March 2020

Sediment connectivity is a fundamental property of river network, which directly influences the geomorphological processes regulating the formation and development of the different in-channel geomorphic units and leading to different river types. Alterations of sediment connectivity, e.g. caused by human disturbances such as dam construction or bed mining, are often followed by changes in channel patterns resulting in potential radical shifts in river types, e.g., from braided systems to sinuous single channel, with consequent loss of river ecosystems associated with specific river types.

In this work, we analyze the connections between basin-scale sediment connectivity indices and river types with the aim of advancing our quantitative ability to inter-relate channel forms and processes with type and amount of sediment fluxes available to the river channel. Our study focuses on the Vjosa river, Albania, which due to the limited anthropogenic bias still showcases a large variety of fluvial forms, including ample sections of braided channels, some of the few remaining in Europe and well renewed as ecological hotspots. The Vjosa river is now interested by large scale hydropower development plans, which may threaten the river unique ecological and morphological value. We estimate sediment transport using the CASCADE model, a modelling framework for basin-scale sediment transport simulation, which generates spatially distributed information on sediment movement and connectivity in river networks. The model has been validated using available data on bed load transport in a braided section close to the basin outlet and surficial grain size distributions collected across the river network.

By integrating CASCADE outputs (i.e., sediment fluxes and size distributions) with available geomorphic information at the network scale (e.g., channel slope and water discharge), we successfully tested an empirical formula proposed in literature based on sediment concentration, median grain size, channel slope and bankfull discharge, to disentangle the drivers of braided or single channel patterns. We then tested the same threshold for different dam development portfolios, showing how even few new dams would alter current conditions in terms of type and amount of sediment availability, leading to multiple channel type shifts from braided to sinuous single channel across the network.

For the first time, the incorporation of the CASCADE model with more traditional geomorphic analysis of river system demonstrate how CASCADE sediment connectivity information advances our ability to interpret existing river system processes, to assess stability of the different channel forms and to evaluate resilience and identify tipping points of fragile system like the Vjosa basin.
Oxidation kinetics of Jurassic coal in Northwest China at low temperature by TG and FTIR analysis
Authors: Wang Kai , Fan Haohao , He Yunzhong , Deng Jun , Zhang Yanni
Published: March 2020

The spontaneous combustion risk of Jurassic coal in Northwest China is special and different from that of permo-carboniferous coal. TG-FTIR experiments of a typical Jurassic coal sample in north Shaanxi was carried out to identify the grading, gas graduating and oxidation kinetics characteristic, under four heating rates of 5, 10, 15, and 20 ℃·min–1 in an air atmosphere. The coal oxidation process of Jurassic coal at low temperature could be divided into two stages, mass loss stage and mass gain stage. The changing rules of apparent activation energy in the coal oxidation process at low temperature were determined by FWO and Kissinger methods. The model-fitting mathematical approach was used to identify the reaction kinetics mechanism functions at two oxidation stages of Jurassic coal in northwest China.
A Teleconnection Pattern over Eurasian Continent in early Spring and its Impact on Bay of Bangle Monsoon Onset
Authors: Yang Yaoxian , Liu Yimin , Wu Guoxiong , Xie Yongkun , Li Jinxiao
Published: March 2020

A teleconnection pattern over the Eurasian continent in early spring and its impact on Bay of Bangle Monsoon onset, is investigated on the basis of reanalysis datasets and numerical test. It is revealed that this pattern shows Rossby wave activities that excited by the forcing feedback of the transient eddies over the exit region of the North Atlantic jet. The anomalous centers can manifest themselves as Rossby wave dividing into two branches and propagating towards Lake Baikal and south flank of the Tibetan Plateau. Meanwhile, asymmetric atmospheric response to vorticity forcing is characterized by weaker amplitude during positive phase than negative phase, which is caused by weaker positive vorticity forcing. Moreover, the anomalous cold cyclone locates on the Tibetan Plateau can bring more snowfall and correspond to anomalously wet soil condition, thereby decreasing surface heat flux and near-surface temperatures, leading to an anomalous cold cyclone can be maintained until April. Therefore, it can postpone Bay of Bangle Monsoon onset. Subsequently, the interannual variations of stationary wave can give a better explanation for late Monsoon onset under neutral ENSO condition. The simulated response to vorticity forcing also can reproduce the pattern of this stationary wave in Linear Baroclinic Model (LBM).
Revealing of surface deformations induced by geodynamic processes in the Kuril island arc from GNSS data
Authors: Gabsatarov Yurii , Vladimirova Irina , Steblov Grigory , Lobkovsky Leopold , Muravieva Ksenia
Published: March 2020

Kuril subduction zone is one of the most active continental margins due to the high plate convergence rate. Latest oceanographical, seismological and geological studies show a block structure of the Kuril island arc. In 2006-2008 Kuril GNSS network was installed along the island arc to provide information on the dynamics of the continental margin. Proper geodetic characterization of surface deformations in Kuril region is necessary for studies of regional geodynamical processes associated with seismic cycles and the evolution of the subduction zone. Since Kuril network has some disadvantages such as small amount of continuous stations (cGNSS) and its near-linear arrangement, special attention must be paid to correct processing of the GNSS data to exclude miscalculations that can affect further modeling of regional geodynamical processes.

We use regression analysis of time series of cGNSS stations displacements to distinguish components which are related to: 1) long-term accumulation of elastic stresses (secular velocity); 2) almost instant release of substantial part of accumulated stresses during main shock (coseismic offsets); 3) transient processes following large subduction eartquakes. The main advantages of the proposed regression analysis algorithm are: 1) an automatic process for detecting coseismic displacements, based on direct modeling of surface deformations using a dislocation model, 2) an automatic process for identifying transient processes; 3) taking into account the realistic GNSS noise model in calculating errors.

Since most of the GNSS stations were deployed only after large 2006-2007 Simushir earthquakes their time series were affected by intense and long-term postseismic transient processes such as afterslip and viscoelastic relaxation in the upper mantle. We use our direct models of these postseismic processes to construct residual time series, which allows us to estimate magnitudes of seasonal periodic signal and to calculate realistic errors.

We use correlation-based clustering algorithm to identify the influence of block structure of island arc on observed deformation patterns during interseismic, coseismic and postseismic stages of the seismic cycle. We also check our processing of GNSS data by constructing model of slip distribution in the source of 2006 Simushir earthquake on the basis of our estimates of coseismic offsets and by comparing our model with previous ones obtained on the basis of satellite geodetic data. The performed analysis of continuous GNSS observations shows that different parts of Kuril island arc are at different stages of seismic cycle.
Seasonal transitions of Arctic sea ice over the satellite era in CMIP6 models
Authors: Smith Abigail , Jahn Alexandra , Wang Muyin
Published: March 2020

Projections of Arctic sea ice area show substantial model spread in CMIP3, CMIP5 and early results from CMIP6. Here we assess how simulated seasonal transitions in Arctic sea ice may be contributing to the large inter-model spread. For this we make use of CMIP6 models, the CESM Large Ensemble and the new Arctic Sea Ice Seasonal Change and Melt/Freeze Climate Indicators satellite dataset. Spring ice loss and fall ice growth can be characterized by various metrics (melt onset, break-up, opening, freeze onset, freeze-up, closing). By assessing numerous metrics of seasonal sea ice transitions, we evaluate a range of ice loss and gain processes in CMIP6 models, as well as biases that may contribute to the large spread in model projections of Arctic sea ice. We show that model biases in seasonal sea ice transitions can compensate for other unrealistic aspects of the sea ice, such as very low ice thickness, resulting in acceptable September sea ice areas for the wrong reasons. Furthermore, we find that the metrics of seasonal sea ice change, while often used interchangeably, are not related to ice area and thickness in the same ways.
The hydrological cycle in a warmer world: combined effects of changes in snowmelt and evaporation on Rhine discharge evaluated with the new dS2 model
Authors: Buitink Joost , Teuling Adriaan J.
Published: March 2020

Recent and projected changes in the climate are known to affect the hydrological cycle. Many studies have shown how these climate changes result in differences in for example, evaporation rates, melt of snow and ice, precipitation patterns and seasonality. Since these processes are influencing different parts of the hydrological cycle, the hydrological response as result of changes in climate can be rather complex (Buitink et al., 2019b). In this study, we investigate how the combined effects of changes in melt from frozen water and increased evaporation rates affect the hydrological response in the Rhine basin, using the new dS2 model (Buitink et al., 2019a). It is known that increased temperatures affect both the melt of frozen water and the energy available for evaporation. However, as temperatures will reach melting point earlier in the year, the contribution of meltwater to the total discharge will also peak earlier in the year. Contrary, evaporation will increase without strong changes in the seasonality. Since the Rhine depends for a significant fraction on meltwater from snow and ice during warm and dry summers, this change in timing can have significant impacts on the low flows. This study shows these effects both for the recent changes in climate, but also presents the sensitivity of the hydrological cycle to the changes in the climate.

 

Buitink, J., Melsen, L. A., Kirchner, J. W., and Teuling, A. J.: A distributed simple dynamical systems approach (dS2 v1.0) for computationally efficient hydrological modelling, Geosci. Model Dev. Discuss., https://doi.org/10.5194/gmd-2019-150, in review, 2019a.

Buitink, J., Uijlenhoet, R., and Teuling, A. J.: Evaluating seasonal hydrological extremes in mesoscale (pre-)Alpine basins at coarse 0.5° and fine hyperresolution, Hydrol. Earth Syst. Sci., 23, 1593–1609, https://doi.org/10.5194/hess-23-1593-2019, 2019b.
Spatio-temporal Inversion using the Selection Kalman Model
Authors: Conjard Maxime , Omre Henning
Published: March 2020

The challenge in data assimilation for models representing spatio-temporal phenomena is made harder when the spatial histogram of the variable of interest appears with multiple modes. Pollution source identification constitutes one example where the pollution release represents an extreme event in a fairly homogeneous background. Consequently, our prior belief is that the spatial histogram is bimodal. The traditional Kalman model is based on a Gaussian initial distribution and Gauss-linear dynamic and observation models. This model is contained in the class of Gaussian distribution and is therefore analytically tractable. These properties that make its strenght also render it unsuitable for representing multimodality. To address the issue, we define the selection Kalman model. It is based on a selection-Gaussian initial distribution and Gauss-linear dynamic and observation models. The selection-Gaussian distribution may represent multimodality, skewness and peakedness. It can be seen as a generalization of the Gaussian distribution. The proposed selection Kalman model is contained in the class of selection-Gaussian distributions and therefore analytically tractable. The recursive algorithm used for assessing the selection Kalman model is specified. We present a synthetic case study of spatio-temporal inversion of an initial state containing an extreme event. The study is inspired by pollution monitoring. The results suggest that the use of the selection Kalman model offers significant improvements compared to the traditional Kalman model when reconstructing discontinuous initial states. 
A Spatially Transferable Drought Hazard and Drought Risk Modeling Approach Based on Remote Sensing Data
Authors: Schwarz Maximilian , Landmann Tobias , Cornish Natalie , Wetzel Karl-Friedrich , Siebert Stefan , Franke Jonas
Published: March 2020

This study presents a new methodology for spatially explicit and globally applicable drought hazard, vulnerability and risk modelling. We focused on agricultural droughts since this sector affects the food security and livelihood situation of the often most vulnerable communities especially in developing countries. Despite recent advances in drought modeling, coherent and spatially explicit information on drought hazard, vulnerability is still lacking over wider areas. In this study a spatially explicit inter-operational drought hazard, vulnerability and risk modeling framework was investigated for agricultural land, grassland and shrubland areas. The developed drought hazard model operates on a higher spatial resolution than most available global drought models while also being scalable to other regions. Initially, a logistic regression model was developed to predict drought hazard for rangelands and cropland in the USA. The model results showed a good spatiotemporal agreement within the cross-verification with the United States Drought Monitor (USDM), using visual interpretation. Subsequently, the explicit and accurate drought hazard model was transferred and calibrated for South Africa and Zimbabwe, where a simplified drought risk indicator was calculated by the combination of drought hazard and drought vulnerability. The drought hazard model used time series crop yields data from the Food and Agriculture Organization Corporate Statistical Database (FAOSTAT) and biophysical predictors from satellite remote sensing (SPI, NDII, NDVI, LST, albedo). The McFadden’s Pseudo R² value of 0.17 indicated a good model fit for drought hazard in South Africa. Additionally, the plausibility of the model results in Southern Africa was evaluated by using regional climate patterns, published drought reports and through visual comparison to a global drought risk model and food security classification data. Drought risk and vulnerability were also assessed for Southern Africa and could be mapped in a spatially explicit manner, showing, for example, lower drought risk and vulnerability over irrigated areas. This developed modeling framework can be applied globally, since it uses globally available datasets and therefore can be easily modified to account for country-specific conditions. Additionally, it can also capture regional drought patterns on a higher spatial resolution than other existing global drought models. This model addressed the gap between global drought models, that cannot accurately capture regional droughts, and sub-regional models that may be spatially explicit but not spatially coherent. The approach of this study can potentially be used to identify risk and priority areas and possibly in an early warning capacity while enhancing existing drought monitoring routines, drought intervention strategies and the implementation of preparedness measures.  
Magnetic modeling of the West Iberian Margin constrained by new geophysical data
Authors: Neres Marta , Ranero César , Grevemeyer Ingo , Merino Irene , Sallares Valenti , Prada Manel , Calahorrano Alcinoe , Cameselle Alejandra
Published: March 2020

The nature of the J magnetic anomaly off West Iberia and its implications on the kinematic and geodynamic evolution of the margin has been addressed by several studies, with several distinct interpretations and resulting models. The main reason for this is that one single geophysical dataset (the IAM-9 seismic profile on the Iberia Abyssal Plain) has until now imaged the respective crust and was available as constraint, leaving a large degree of uncertainty for interpretation and modeling. New geophysical imaging of the structure of J anomaly and nearby domains, preferably in different margin sectors, would then be essential to cast new light on the discussion on the Iberian margin evolution. We here present new constrained magnetic modeling for two profiles across the J anomaly off Iberia, in the Tagus and in the Iberia Abyssal Plain, respectively. These profiles were recently surveyed for wide angle and reflection seismics and for magnetic data, during the FRAME-2018 survey. The joint processing of wide angle and reflection seismic data revealed with unprecedented detail the velocity structure and the tectono-stratigraphy along the profiles. Here, we use these results as constraints for magnetic modeling of the measured anomalies, namely for detailed definition of the basement topography and identification of the different domains. Magnetic modeling allowed inferring the relative contribution of each layer and the existence of additional magnetic sources, such as intrusive bodies in exhumed mantle domains. Regarding the J anomaly, we show that it cannot be attributed only to magnetization contrasts between different layers. The J anomaly is rather the result of an anomalous highly magnetized source body, associated with a locally thicker crust, which claims for an abnormal magmatic composition with strong enrichment in iron oxides. We discuss possible origins for the found structure and composition of the J anomaly off Iberia, as well as implications of the new magnetic modeled profiles for the margin conjugation and kinematics.

The author would like to acknowledge the financial support  FCT through project UIDB/50019/2020 – IDL.
Application of Geoinformation Technologies for minimization of thyroid gland diseases in the impact areas of the radioiodine fallout
Authors: Baranchukov Vladimir , Korobova Elena , Romanov Sergey
Published: March 2020

Modern geoinformation technologies are widely used in spatial data analysis including medical geography locating spatial distribution of site-specific diseases. Following obviously essential problems the major part of such maps have been constructed for the most dangerous diseases. Although thyroid goiter has been known since ancient times, but it was not earlier than the middle of XIXth century when Chatain has related this disease to deficiency of the particular chemical element (iodine). And not earlier than 1938 Vinogradov has coined the notion of biogeochemical provinces to distinguish areas of specific endemic disease of geochemical origin and summarized natural factors causing iodine deficiency in local diets and contributing to goiter manifestation. The Chernobyl accident has highlighted the problem of a combined negative impact of radioiodine contamination and stable iodine deficiency. Technogenic and natural isotopes of iodine have specific spatial structure and this fact opened new prospects in identification of areas under different risk levels by using GIS technology. To study the geochemical factors responsible for distribution of the thyroid gland diseases in Chernobyl fallout area we have created and develop a specialized geographic information system basing on the idea of a two-layers spatial structure of modern noosphere (Korobova, 2017) according to which the natural geochemical background reflected in the soil cover structure is overlain by technogenic contamination fields. As a result an interferential imagery is produced. This image can be interpreted as a risk map which in turn may be verified by health effects. The study was performed for 4 regions subjected to the Chernobyl accident (Bryansk, Oryol, Kaluga and Tula oblast’s). An overlay of natural iodine deficiency and technogenic iodine fallout map layers classified by 6 zones from minimum to maximum risk allowed to identify 12 zones and to evaluate a combined risk for 93 rural districts. Comparison of the created combined risk map and radionuclide contamination map with regional medical data on standardized incidence of thyroid cancer (code C-73 ICD-10) had a higher correlation (r = 0.493, n = 93) compared to the map of the levels of radionuclide loss. All this, obviously, demonstrates that the proposed GIS technology will be useful to adequately minimize in any case thyroid diseases.

References
Korobova, E.M. Principles of spatial organization and evolution of the biosphere and the noosphere. Geochem. Int. 55, 1205–1282 (2017) doi:10.1134/S001670291713002X
Calibrating and validating a numerical model concept for microbially enhanced coal bed methane production with batch and column data
Authors: Emmert Simon , Davis Katherine , Gerlach Robin , Class Holger
Published: March 2020

Microbially enhanced coal-bed methane (MECBM) production is an innovative idea to stimulate biogenic coal-bed methane production by providing nutrients to the native microbial community. Through additional substrate in the subsurface, a stimulation of microbes occurs, which leads to an increased methane production. Experimental studies, performed at Montana State University, provide the basis for modelling MECBM production with two-phase multi-component transport processes using the numerical simulator DuMuX [1].

We will present the calibrated and validated numerical batch model. The conceptual model comprises a food-web that includes two types of bacteria and three types of archaea representing substrate-specific members of the community with the corresponding biogeochemical reactions. These are derived from experimental studies [2]. The model is able to capture the interactions between different microbial groups, coal bioavailability, biofilm growth and decay as well as CH4 production.

The numerical batch model is extended to simulate column studies [3]. The model is being used to test hypotheses on different processes e.g. coal bioavailability and retardation or filtering effects when adding substrate. The numerical model provides a more detailed understanding of the relevant processes involved in MECBM production as well as a general understanding of biogeochemical reactions coupled with possibly changing flow and transport conditions in the subsurface. This model will be an instrumental tool in further development of a more sustainable method of harvesting methane from unmineable coal-beds.

[1] Koch, Timo, et al. "DuMuX3--an open-source simulator for solving flow and transport problems in porous media with a focus on model coupling." arXiv preprint arXiv:1909.05052 (2019).
[2] Davis, Katherine J., et al. "Biogenic Coal-to-Methane Conversion Efficiency Decreases after Repeated Organic Amendment." Energy & fuels 32.3 (2018): 2916-2925.
[3] Davis, Katherine J., et al. "Biogenic coal-to-methane conversion can be enhanced with small additions of algal amendment in field-relevant upflow column reactors." Fuel 256 (2019): 115905.

 
Detection of subsurface water storage dynamics with combined gravity - vertical gravity gradient monitoring and hydrological simulation
Authors: Cooke Anne-Karin , Champollion Cédric , Vermeulen Pierre , Janvier Camille , Desruelle Bruno , Le Moigne Nicolas , Merlet Sébastien
Published: March 2020

Time-lapse ground-based gravimetry is increasingly applied in subsurface hydrology, providing mass balance constraints on water storage dynamics. For a given water content change as e.g. after a precipitation event, the simplest assumption is that of a homogeneous, infinite slab (Bouguer plate) of water column causing the measurable increase in gravitational attraction. For heterogeneous subsurface environments such as karst aquifers at field scale this assumption may not always hold. The gravity signal is depth-integrated and non-unique, hence indistinguishable from a heterogeneous distribution without further information.

Exploiting the different spatial sensitivities of gravity and vertical gravity gradient (VGG) data can shed light on the following questions:

 

Is the subsurface water content within the gravimeter’s footprint likely to be homogeneous or showing small-scale heterogeneity?

If not, at which distance are these mass heterogeneities and how large are they?

Which monitoring set-ups (tripod heights, number of and distance between VGG measurement locations) are likely to detect mass heterogeneity of which spatial characteristics?

One year of monthly vertical gravity gradient surveys has been completed in the geodetic observatory in karstic environment on the Larzac plateau in southern France. We interpret the VGG observations obtained in this field study in the context of further available hydraulic and geophysical data and hydro-gravimetrical simulation. Finally, practical applications in view of detecting near-surface voids and reservoirs of different porosities as well as their storage capacity and seasonal dynamics are evaluated.
Formation and preservation of syntectonic sedimentary breccias in extensional environments (Crete and Pyrenees) and in-situ U-Pb constraints for the age of breccias in the Bas-Agly Basin
Authors: Kernif Tarik , Nalpas Thierry , Gautier Pierre , Bourquin Sylvie , Poujol Marc
Published: March 2020

A breccia is a rock made up of angular clasts. Its formation can be the result of several types of geological processes (sedimentary, tectonic, hydraulic, magmatic, etc.). The aim of this study is to understand the formation and the preservation of sedimentary breccias with a significant thickness (several tens to hundreds of meters) in extensional environments, by comparing the Bas-Agly Basin, in the eastern French Pyrenees, to a recent analogue (Pleistocene-Holocene deposits of the Chora Sfakion region, SW Crete). In both cases, the breccias mainly consist of carbonate elements.

Our preliminary results show that:

- Along the coast of the Chora Sfakion region, sedimentary breccias are preserved at the front of a major normal fault scarp over a distance of ca. 20 km. Their formation results from a destabilization of the topographic slope triggered by the activity of the fault. The breccias were preferentially developed at the expense of dolomitic layers that underwent intense fracturation during an older deformation phase. Breccia deposition was related to processes of aerial or sub-aquatic landslides. Relatively fine-grained unsorted breccias are found close to the main fault whereas larger blocks and olistoliths are found farther away and down-slope, attesting for large mass slides. Preservation of the breccias has been favoured by subsidence at the front of the fault.

- The sedimentary breccias of the Bas-Agly Basin bear characteristics that are broadly comparable to those of Crete. With respect to the Cretan case, the Bas-Agly deposits, which consist of breccias alternating with fine sediments, represent a more distal part of the system. However, the age of the breccias in the Bas-Agly Basin is widely debated, with estimates ranging from the Late Jurassic to the Eocene. Depending on the actual age, the tectonic environment could have been quite different, e.g. extensional or compressional. Thus, it is crucial to know the real age of these rocks. In order to solve this issue, we initiated a geochronological study, using in-situ U-Pb dating by LA-ICP-MS and focusing on the carbonate matrix of the breccias. This approach has proven successful and yielded ages consistent with the proposed extensional environment.

In summary, extensional tectonics appear to favour both the production and the preservation of large volumes of sedimentary breccias, which, therefore, may be considered as a marker of this tectonic regime. Whether compressional tectonics could produce a similar situation is a topic of ongoing research.

Keywords: breccias, sedimentary, syntectonic, extension, Crete, Pyrenees, U-Pb dating
Investigation of active movement prior to artificial slope landslides from multi-temporal InSAR: a case study of Northern Taiwan
Authors: Liang Hongyu , Zhang Lei , Ding Xiaoli
Published: March 2020

Detection of slope instability using Interferometric Synthetic Aperture Radar (InSAR) can aid the understanding of landslide kinematics and prevent the related geological hazards. However, conventional InSAR techniques often fail in the retrieval of deformation measurements in mountainous areas with dense vegetation and complex terrain, thus resulting in diminished information of slope movement. In this study, we propose a new multi-temporal InSAR method to improve the spatial coverage of measurement points by jointly exploiting persistent scatterers (PS) and distributed scatterers (DS). Particularly, topographic errors and tropospheric delays are well-considered according to their spatial and temporal characteristics. We applied this method to retrieve the historic displacements prior to the collapse of an artificial slope in Northern Taiwan using 15 ALOS/PALSAR images. The derived results suggest a pre-landslide movement with a rate of approximately -30 mm/year in the radar line-of-sight (LOS) direction. Meanwhile, the time series displacements reveal that the temporal behaviors of downslope movement are correlated with local rainfall and seismic activities. The study helps to analyze the slope instability in Northern Taiwan.
Dynamics of spatiotemporal heterogeneity of cyanobacterial blooms in large eutrophic Lake Taihu, China
Authors: Li Wei , Qin Boqiang
Published: March 2020

  Cyanobacterial blooms caused by eutrophication in Lake Taihu, China are recognized as highly heterogeneous spatiotemporally. It is assumed that the high spatiotemporal heterogeneity of algal blooms is determined by divergence/ convergence processes in the fluid medium. To address this issue, three episodes of the dominant spatial patterns of hourly simulated divergence fields of current in Lake Taihu in July of 2012 were analyzed using a hydrodynamic numerical model combined with the Empirical Orthogonal Function (EOF) method. The results showed that, on days that blooms occurred, the first two EOF modes explained 89.4% of the variability and the dominant spatial patterns of stronger convergence zones were in agreement with the regions of bloom occurrence and accumulation. When no blooms occurred, the first EOF mode explained 72.5% of the variability and divergence zones were dominant in the lake. Both the simulated hourly average divergence field and the first EOF mode in the time interval in which blooms occurred further confirmed that blooms accumulate in the current convergence zones. These findings explain the dynamic mechanism of occurrence of cyanobacterial blooms and will facilitate forecasting of short-term blooms for protecting drinking water supplies and managing risk.