bluuebunny/crossref_metadata_2025 huggingface dataset:
Sensitivity of pond methane emissions in the Lena River Delta to climate changes in new model MeEP
Authors: Rehder Zoé , Kleinen Thomas , Kutzbach Lars , Stepanenko Victor , Brovkin Victor
Published: March 2021

Permafrost ponds are a steady source of methane. However, it is difficult to assess the sensitivity of pond methane emissions to ongoing warming and climate-change-induced drainage, because pond methane emissions show large temporal and spatial variability already on local scale.
We study this sensitivity on the landscape level with a new process-based model for Methane Emissions from Ponds (MeEP model), which simulates the three main pathways of methane emissions (diffusion, plant-mediated transport and ebullition) as well as the temperature profile of the water column and the surrounding soils. The model was set up for the polygonal tundra in the Lena River Delta. Due to a temporal resolution of one hour, it is capable of capturing the diurnal, day-to-day and seasonal variability in methane fluxes. MeEP also considers one of the main drivers of spatial variability - ground heterogeneity. Depending on where ponds form in the polygonal tundra, they can be classified as ice-wedge, polygonal-centre or merged-polygonal ponds. In MeEP, each of these pond types is simulated separately and the representation of these ponds was informed by dedicated measurements.
The model performance is validated against eddy-covariance measurements of methane fluxes and against in-situ measurements of the aqueous methane concentration, both obtained on Samoylov Island.  We will present results regarding the sensitivity of modeled methane emissions from ponds to warming and drainage on the landscape scale.
An online service for analysing ozone trends within EOSC-synergy
Authors: Kerzenmacher Tobias , Kozlov Valentin , Sanchis Borja , Cayoglu Ugur , Hardt Marcus , Braesicke Peter
Published: March 2021

The European Open Science Cloud-Synergy (EOSC-Synergy) project delivers services that serve to expand the use of EOSC. One of these services, O3as, is being developed for scientists using chemistry-climate models to determine time series and eventually ozone trends for potential use in the quadrennial Global Assessment of Ozone Depletion, which will be published in 2022. A unified approach from a service like ours, which analyses results from a large number of different climate models, helps to harmonise the calculation of ozone trends efficiently and consistently. With O3as, publication-quality figures can be reproduced quickly and in a coherent way. This is done via a web application where users configure their queries to perform simple analyses. These queries are passed to the O3as service via an O3as REST API call. There, the O3as service processes the query and accesses the reduced dataset. To create a reduced dataset, regular tasks are executed on a high performance computer (HPC) to copy the primary data and perform data preparation (e.g. data reduction, standardisation and parameter unification). O3as uses EGI check-in (OIDC) to identify users and grant access to certain functionalities of the service, udocker (a tool to run Docker containers in multi-user space without root privileges) to perform data reduction in the HPC environment, and the Universitat Politècnica de València (UPV)  Infrastructure Manager to provision service resources (Kubernetes).
A hydrodynamically consistent "slope-area" relationship for analysing fluvial landscape with wide rivers.
Authors: Bernard Thomas , Davy Philippe , Lague Dimitri
Published: March 2021

Landforms and channel networks have long been analysed through co-variation between topographic slope and drainage area, which is derived from easy-to-implement flow routing algorithms (D8 or Dinf) relying on topographic slopes. The slope-area relationship has been successful to identify morphologic regions in landscapes likely reflecting the erosion and transport processes that shape them. But the implicit assumption for using the slope-area relationship is that channels are narrower than the DEM resolution and that, at this scale, the flow is correctly routed. These assumptions are no more valid for very high-resolution DEM (HRDEM, <2 m) that are now widely available with unprecedented level of vertical accuracy (< 20 cm). In wide rivers, the drainage area algorithm puts the total river discharge in one of the pixel of each channel section and let the others with unrealistically low areas. In other words, D8 or Dinf algorithms are not adapted to resolve the lateral extent of rivers.

In this study, we propose a new topographic analysis relying on realistic hydraulic simulations of surface flow. For this, we use a particle-based hydraulic model, Floodos, which solves the 2D shallow water equations, and we present an analysis of the 1m LiDAR DEM of the Elder creek watershed in California, for which channels are up to ten meters wide. By simulating channel flows with water depth, hydraulic slope, specific discharge and bed shear stress, the hydraulic model reveals landscape patterns that are not described by the slope-area relationship. Additionally, the flow model handles very well the small irregularities of the topography.

We introduce new geomorphic descriptors: the hydraulic slope and the specific drainage area (or specific discharge). The catchment organization is then analysed through a new framework called the hydraulic slope-area diagram. This diagram has several benefits over the classical slope-area diagram. It correctly classifies pixels located in the river for a given discharge in the fluvial domain leading to a sharper transition between the colluvial and fluvial domain. The hillslope-to-valley transition is also insensitive to the DEM resolution. Channel width can also be automatically calculated based on a joint analysis of Dinf and 2D shallow water simulation. Finally, the capability to perform the hydraulic slope-area for various discharges brings a richer description of landscape organization by highlighting discharge-dependent regions such as floodplain areas and fluvial terraces.
Sediment displacement evolution after dam removal in a mountain river (Oioki dam, Leitzaran River)
Authors: García J. Horacio , Ibisate Askoa , Sánchez-Pinto Iban , Vázquez-Tarrío Daniel , Ollero Alfredo , Herrero Xabier , Ortiz Martínez de Lahidalga Josu , Beltrán de Lubiano Jon
Published: March 2021

Bedload sediment transport was monitored from 2016 to 2020 in the Leitzaran River, in a reach affected by the removal of 7-meters high dam (Oioki dam). The removal was accomplished in two phases, the 3 first meters were removed in September 2018 and the second phase (September 2019) involved the removal of the remaining 4 meters. The study area was divided into three subreaches: control (unaffected by the dam), upstream and downstream of the dam. A sample of 300 RFID-tagged stones were seeded every year (100 at each reach).. Prior to this, the grain-size distribution of the surface sediment was characterized using the Wolman method. Then, the grain-size chosen for the tracer stones was distributed according to three Wentworth intervals: that corresponding to the surface d50, d50+1 (immediate upper interval), and d50-1 (immediate lower interval). It was not possible to follow completely, and the lower interval had to be dismissed as the sediment was very small or narrow to insert the tracer.

We conducted an extensive surveying field campaign every summer.

The number of retrieved tracers was relatively high, around 40-70% (considering all field campaigns), although with differences amongst the different sub-reaches. The obtained results were organized by displacements and volumes of sediment moved. The maximum (3,500 meters) and higher mean displacement (~1,550 meters) were registered in the hydrologic year 2019/20. These values are from the upstream reach of the dam and match simultaneously with (i) the whole removal of the dam, and (ii) the period showing a lower discharge (note the critical discharge for the movement of our particles is ~25-30 m3·s-1 (d50 = 64.0≥Ø<90.5 mm); mean discharge and peak flow from 2013 to 2020 were ~5.3 m3·s-1 and ~125.0 m3·s-1, respectively and at the end of the watershed).

We also estimated the bulk bedload volumes during the time spanned by this research and we report how the hydrologic year 2019/20 was the more active in terms of displaced volumes, moving up to 27,500 tons in the upstream reach. In fact, this year also presents the maximum for the downstream reach.

At this moment, besides the raw data of displacements and volumes, our observations highlight how the fact that a copious load of sediment was made available with the dam removal seemed to be more determinant than the magnitude of the flow to get larger tracer displacements.
Assessing farmers’ irrigation practices under drought conditions in semi-arid area: Combining remote sensing data and agro-hydrological modeling
Authors: Labbaci Adnane , Brouziyne Youssef , Hallam Jamal , Bouchaou Lahoussaine
Published: March 2021

Drought is a serious natural hazard with far-reaching impacts including modification of biodiversity and other ecosystem functions, economic disruption, and a threat to human livelihoods and health through food systems alteration. Climate models project robust increases in drought and dryness in the Mediterranean region because of changing climate conditions.  Despite the scarcity of water, irrigated agriculture plays a major socio-economic role in groundwater-dependent irrigated regions of Morocco. Strategic sectors such as citrus rely on irrigation to maintain or even increase production and citrus stakeholders put sustainable irrigation management at the top priorities. This study aims to assess seasonal drought severity in the Souss plain, the largest citrus’ growing area in Morocco, using VCI (Vegetation Condition Index), TCI (Temperature Condition Index), and VHI (Vegetation Health Index) based on Sentinel-2 and Landsat 8 data. We explored the benefits of using the Soil Water Atmosphere Plant (SWAP) agro-hydrological model to optimize irrigation water management of a citrus orchard. The SWAP model was applied over three growing seasons from 2016 to 2019 to optimize seasonal water supply based on different criteria (e.g., critical soil pressure head and allowable daily stress), particularly during the drought episodes. The VHI was estimated and classified into five classes: extreme, severe, moderate, mild, and no drought. Key outputs of the SWAP model show that the farmers’ irrigation practices did not compensate for the lack of rainfall in the spring, which led to long-term unavailable water during crop development. The SWAP predictive model determined the optimal amount of water and irrigation scheduling systems to make efficient use of while maintaining appropriate yields. The developed algorithm simulation uses the minimal sufficient seasonal amount of water. The designed approach helps prevent critical stress in citrus orchards together with sustainable water distribution in accordance with best agronomic practices.

Keywords: Citrus, drought, water scarcity, sustainable irrigation management, VHI, VCI, TCI, SWAP, Souss plain
Active Moving Area Identification using Machine Learning. Case study: Ometepe Island, Nicaragua
Authors: Arcia Víctor , Corzo Gerald , Calderón Heyddy
Published: March 2021

This study aims to propose the use of spatio-temporal Remote Sensing information and Machine learning techniques (ML) for Active Moving Area Identification and Forecast. Mass Movements are frequent in Central American countries, mainly due to the combined extreme hydro-meteorological events with the seismic activity and the characteristics of the geological formations in the region. Ometepe Island is located in Lake Cocibolca, Nicaragua; it has two volcanoes (one active) and Mass Movements happen quite often in the area, where many of them represent a big risk for the population. The triggering factors for these Mass Movements are mainly volcanic activity in conjunction with high and quick precipitations. The process of identification of a Mass Movement from Remote Sensing images is used first as a way to characterise the data, and then a lagged time step was used to evaluate the forecasting capabilities in a time window of precipitation forecast. For this, Remote Sensing was used to create the Active Moving Area Inventory, using InSAR technique with Sentinel-1 SAR images. SNAP software was used to locate occurrences of displacements in the island. This inventory was used to develop ML models that had Rainfall and Soil Moisture as dynamic variables; and DEM, Land Use, Geomorphology, and others as static variables. These were trained and evaluated using Logistic Regression (LR), Random Forest (RF) and Long Short-Term Memory (LSTM) to detect occurrence of Displacement in a particular area of the island. The results were analysed performance-wise and compared to each other. The results of this methodology are a first step into a larger framework of spatiotemporal analysis for forecasting using Machine Learning.
Constraining ice nuclei freezing efficiency using cloud phase observations together with climate models.
Authors: Villanueva Diego
Published: March 2021

Aerosol-cloud interactions are an important source of uncertainty in current climate models. In particular, the role of mineral dust and soot particles in cloud glaciation is poorly understood. This lack of understanding leads to high uncertainty in climate predictions.

To estimate the global co-variability between mineral dust aerosol and cloud glaciation, we combined an aerosol model reanalysis with satellite retrievals of cloud thermodynamic phase. Our results confirmed that the cloud thermodynamic phase increases with higher mineral dust concentrations.

To better understand and quantify the impact of ice-nucleating particles on cloud glaciation, it is crucial to have a reliable estimation of the hemispheric and seasonal contrast in cloud top phase, which is believed to result from the higher dust aerosol loading in boreal spring. For this reason, we locate and quantify these contrasts by combining three different A-Train cloud-phase products for the period 2007-2010. These products rely on a spaceborne lidar, a lidar-radar synergy, and a radiometer-polarimeter synergy. We used these observations to constrain the droplet freezing in the ECHAM-HAM climate model. After tuning, the model leads to more realistic cloud-top-phase contrasts and a dust-driven glaciation effect of 0.14 ± 0.13 Wm−2 between 30–60°N. Our results show that using observations of cloud-top phase contrasts provide a strong constraint for ice formation in mixed-phase clouds and a weak constraint for the associated impact on radiation and precipitation.

Besides mineral dust, it has been under debate whether black carbon also contributes to cloud glaciation. Therefore, we studied the cloud top phase retrieved by CALIOP during the Australian wildfires in 2020. After repeating the tuning strategy for black carbon, we were able to replicate the increase in ice cloud frequency observed during the wildfires.
Simulated suspended sediment flows in South America using hydrological-hydrodynamic modeling
Authors: Fagundes Hugo , Fan Fernando , Paiva Rodrigo , Siqueira Vinicius , Buarque Diogo , Kornowski Luisa , Laipelt Leonardo , Collischonn Walter
Published: March 2021

Suspended sediments (SS) have an important role in the maintenance of several ecosystems by supplying them with nutrients. On the other hand, erosion and sediment transport can carry pollutants and pesticides, contributing to the negative impacts on the aquatic biota. Besides that, sediment supply for the rivers is often a driver to geomorphologic changes occurring in the rivers. Erosion and sediment rates in South America are considerably high in comparison to northern continents in the world. In this study we modeled the natural (non affected by reservoirs) spatio-temporal dynamic of suspended sediments in South America, including deposition rates in floodplain areas, using the sediment continental model MGB-SED SA. The model performance was evaluated aga inst 595 in-situ stations; 80 sites using results from regional studies; and 51 sites using results from a global sediment model. For most places, model performance analysis shows a better agreement between simulated and observed (in-situ) data than when results were compared to regional studies and a global model data. A better representation of sediment flow in rivers and floodplains was possible due to the use of hydrodynamic river routing. Based on MGB-SED SA estimates, South America delivers to the oceans 1.00×109 t/year of SS. The bigger suppliers are the Amazon (4.36×108 t/year), Orinoco (1.37×108 t/year), La Plata (1.11×108 t/year), and Magdalena (3.26×107) rivers. Around 12% (2.40×108 t/year) of SS loads reaching the rivers are stored in the floodplains, showing the importance of these regions.  
Impact of Multi-GNSS Antenna-Receiver Calibrations in the Coordinate Domain
Authors: Kröger Johannes , Kersten Tobias , Breva Yannick , Schön Steffen
Published: March 2021

In order to obtain highly precise positions with Global Navigation Satellite Systems (GNSS), it is mandatory to take all error sources adequately into account. This includes phase center corrections (PCC), composed of a phase center offset (PCO) and corresponding azimuthal and elevation-dependent phase center variations (PCV). These corrections have to be applied to the observations since the pattern of the GNSS receiver antennas deviate from an ideal omnidirectional radiation pattern.
The Institut für Erdmessung (IfE) is one of the IGS accepted institutions for absolute antenna calibration. Recently, the operationally calibration procedure has been further developed to a post processing approach. Thus, PCC can also be estimated for all frequencies (including e.g. GPS L2C, L5) and systems like Galileo and Beidou. Additionally, the newly developed approach allows to assess the impact of using different receivers with different settings on an individual calibration. 
Previous studies already have shown, that the geodetic receivers used during the absolute calibration of antennas have an impact on the estimated PCC. However, currently this impact is only analysed at the level of the respective patterns and not in the coordinate domain. Moreover, the results are always only valid for the respective antenna-receiver combination. Therefore, more samples of different combinations are required.
In this contribution, we study calibration results of several antenna-receiver combinations using a zero baseline configuration during the calibration process in order to assess the receiver’s impact due to different signal tracking modes. The resulting PCC are analysed on the pattern level regarding (i) the repeatability of individual calibrations and (ii) differences between different antenna-receiver combinations. Finally, the impact of the different PCC are validated in the coordinate domain by a well controlled short baseline and common clock set-up. Here, again a zero baseline configuration with the identical receivers used during the calibration process is performed. Consequently, the impact of the respective antenna-receiver combination with individually estimated PCC on the positioning is analysed.
Investigating the chemical and spatial distribution of root carbon along the root-microbe-mineral pathway
Authors: Shabtai Itamar , Lehmann Johannes , Bauerle Taryn
Published: March 2021

Plants allocate an estimated 11% of the C that they fixate as root exudates, a complex mixture of compounds that helps engineer the plant’s subterranean habitat. Root exudates stabilize soil aggregates, improve water retention, and shape rhizosphere microbial community composition. Exudates are also thought to contribute to the formation of stable mineral-associated organic matter. However, the function and fate of exudates along the soil profile may differ. We hypothesize that in topsoils with highly active microbial populations and mineral surfaces saturated with organic matter, root exudates may be rapidly intercepted and assimilated by soil microbes, and later adsorbed to surfaces as microbial necromass. But in subsoils with low microbial activity, exudates may directly adsorb on unsaturated mineral surfaces. The magnitude of these divergent pathways can shape the role of root exudates in rhizosphere C cycling. However, little is known about how adsorption vs. decomposition processes at the root-soil interface control i) the chemical transformations of C occurring along the root-microbe-mineral pathway, and ii) the spatial distribution and heterogeneity of exuded and processed exudate C. Our objective was to investigate the effect of microbial activity, and reactive mineral surfaces on the spatial distribution and functional group chemistry of root exudates at the root-microbe-mineral interface.

We packed samples from O, A, B, and C horizons collected from a grassland Mollisol, into individual microcosms, and installed a porous microdialysis membrane which served as an artificial root. Through this root, we injected either root exudates collected from maize plants, or dissolved organic carbon extracted from plant litter collected at the site. This comparison allowed us to study the dynamics of organic inputs entering the soil profile from the litter layer vs. directly from the roots. We destructively sampled the microcosms and obtained intact cross sections containing the artificial root and surrounding mineral/pore structures at different time points throughout the experiment. Here, we will present results obtained using synchrotron-radiation FTIR-microscopy of the temporal evolution, and spatial distribution of organic matter functional group chemistry in an artificial rhizosphere.
Global Heritage Stone Resource in Brazil
Authors: Del Lama Eliane Aparecida , Costa Antônio Gilberto
Published: March 2021

Since the establishment of the Heritage Stone Subcommission by the International Union of Geological Sciences (IUGS), in 2011, idealized with the purpose of designating stones of historical significance to compose the Global Heritage Stone Resource (GHSR), 22 of them have been designated. The nationalities of these GHSR are: 3 British, 1 Norwegian, 2 Belgian, 2 Swedish, 1 Slovenian, 3 Italian, 2 Portuguese, 3 Spanish, 1 Maltese, 1 Indian, 2 American and 1 Argentine. So far, no Brazilian stone has been designated as GHSR. We can observe in monuments and buildings in the Brazilian territory the following imported GHSR: Lioz Stone and Estremoz Marble from Portugal, Carrara Marble and Rosa Beta Granite from Italy and Larvikite from Norway. The use of stones from Portugal and Italy is related firstly to the Portuguese colonization and, later, to economic cycles, such as rubber and coffee, with Italian immigration being significant to the coffee cycle. The presence of Lioz is major, however, it is found almost exclusively in some Brazilian coastal capitals, such as Rio de Janeiro, Salvador and Belém. The churches of Salvador are richly decorated with numerous varieties of Lioz. In Belém, it is found in the Basilica of Nossa Senhora de Nazaré, among other churches, and in many tombstones in the Nossa Senhora da Soledade Cemetery. Estremoz Marble is found in commercial buildings and tombstones. In the city of São Paulo, lots of buildings have internal cladding and ornaments made in Carrara Marble, e.g. Municipal Theater, Palace of Justice, Metropolitan Cathedral and Obelisk Mausoleum for the Heroes of 32. In the city of Rio de Janeiro, the tomb of Orville Derby (founder of the Geological Survey of Brazil) at São João Batista Cemetery, among others, is decorated with Carrara Marble, which can also be seen in tomb art of Salvador, Belo Horizonte, Curitiba and São Paulo. Rosa Beta Granite can be seen at Monument to Bartolomeu de Gusmão in the city of Santos, costal area of São Paulo State. The use of Larvikite is contemporary. This stone is mainly present in tombstones, for example, at the Consolação Cemetery in São Paulo, but it also decorates the façades of several commercial buildings, both in capitals and several Brazilian cities. In Brazil, several types of Brazilian stones are found in monuments and religious or administrative buildings. These stones, which have been used since Colonial Brazil, are characteristic of certain regions, such as Augen Gneiss in Rio de Janeiro, Itaquera Granite in São Paulo, beachrock in northeastern Brazil, quartzites and steatite in Minas Gerais, among others. Some of them constitute UNESCO World Heritage Sites, and due to their historical importance to our heritage, these stones may be indicated as GHSR in the future.
Heavy rainfall in the northern coast of Ecuador in the aftermath of El Niño 2015/2016 and its predictability 
Authors: Pineda Luis E. , Changoluisa Juan , Muñoz Ángel G.
Published: March 2021

In January 2016, a high precipitation event (HPE) affected the northern coast of Ecuador leading to devastating flooding in the Esmeraldas’ river basin. The HPE appeared in the aftermath of the 2015/2016 El Niño as an early onset of heavy rainfalls otherwise expected in the core rainy season (Mar-Apr). Using gauge data, satellite imagery and reanalysis we investigate the daily and ‘weather-within-climate’ characteristics of the HPE and its accompanying atmospheric conditions. The convective storms developed into a mesoscale convective complex (MCC) during nighttime on 24th January. The scale size of the heavy rainfall system was about 250 km with a lifecycle lasting 16 hours for the complete storm with 6 hours of convective showers contributing to the HPE. The genesis of the MCC was related to above-normal moisture and orographic lifting driving convective updrafts; the north-south mountain barrier acted as both a channel boosting upslope flow when it moves over hillslopes; and, as a heavy-rain divide for inner valleys. The above normal moisture conditions were favored by cross-time-scale interactions involving the very strong El Niño 2015/2016 event, an unusually persistent Madden–Julian oscillation (MJO) in phases 3 and 6, remotely forced by tropical synoptic scale disturbances. In the dissipation stage, a moderate low-level easterly shear with wind velocity of about 10 m/s moved away the unstable air and the convective pattern disappear on the shore of the Esmeraldas basin.

 

We use ECMWF re-forecast from the Sub-seasonal to Seasonal (S2S) prediction project dataset and satellite observations to investigate the predictability of the HPE. Weekly ensemble-mean rainfall anomaly forecasts computed from raw (uncorrected) S2S reforecast initialized on 31st Dec 2015, 7th, 14th and 21st Jan 2016 are used to assess the occurrence of rainfall anomalies over the region. The reforecast represents consistently, over all lead times, the spatial pattern of the HPE. Also, the ensemble-mean forecast shows positive rainfall anomalies at times scales of 1-3 weeks (0-21 days) at nearly all initialization dates and lead times, predicting this way successfully the timing and amplitude of the highest HPE leading the 25th January flood.
A view of recent forest fire in Australia by satellite derived indices
Authors: Nguyen Kim-Anh , Liou Yuei-An , Ho Le-Thu
Published: March 2021

Bushfire is one of the dangerous natural manmade hazards. It can cause great damges to the air quality, human health, environment and bio-diversity. In addition, forest fires may be a potential and signigicant source of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans. In early 2020, Australia experienced serious bushfires with over an area of estimated 18.6 million hectares burned, over 5,900 buidlings (including 2, 779 homes) destroyed, and at least 34 people (including three fire fighters) and billion animals and some endangered species killed. Subsequently, air quality was degraded to hazardous levels. It was estimated that about 360 million tonnes of CO2 was emitted as of 2 Jan. 2020 by NASA. Remote sensing data has been instrumental for the environmental monitoring in particular the bushfire. Many methods and algorithms have been proposed to detect the burned areas in the forest. However, it is challenging or even infeasible to routinely apply them by non-experts due to a chain of sophisticated schemes during their implementation. Here, we present a simple and effective method for mapping a burned area. The performances of different optical sensors and indices are conducted. Sentinel-2 MSI and Landsat 8 data are ultilized for the comparison of burned forest by analyzing different indices (including NDVI, NDBR and newly development index Nomarlized Difference Laten Heat Index (NDLI)). The forest damages are estimated over the Katoombar, Austrialia and the burning severity map is generated and classified into eight levels (none, high regrowth, lowregrowth, unburned, low severity, moderate low severity, moderate high severity, and high severity). The comparision in results from Sentinel-2 MSI data and Landsat image is performed and presented.
On the stress sensitivity of the dehydration kinetics of gypsum: insights from fast in-situ synchrotron X-ray scattering  
Authors: Schrank Christoph , Gaede Oliver , Blach Tomasz , Gioseffi Katherine , Mudie Stephen , Kirby Nigel , Regenauer-Lieb Klaus , Radlinski Andrzej
Published: March 2021

The potential role of differential stress for mineral stability and the kinetics of mineral replacement reactions remains a matter of hot debate. We present a series of unique in-situ laboratory experiments on the dehydration of polycrystalline natural gypsum to hemihydrate, which were designed to test if the application of small differential stresses affects the mineral transformation rate. The dehydration experiments were conducted in a purpose-built loading cell suitable for in-situ monitoring with synchrotron transmission small- and wide-angle X-ray scattering (SAXS/WAXS). The time-resolved SAXS/WAXS data provide measurements of the transformation kinetics and the evolution of nano-pores of the dehydrating samples.

In our experiments, the kinetic effects of two principal variables were examined: dehydration temperature and axial confinement of the sample discs. In contrast to most previous dehydration experiments conducted in triaxial deformation apparatus, we applied different axial pre-stresses to the radially unconfined sample discs, which were well below the uniaxial compressive strength of the test material. This loading condition corresponds to constant-displacement rather than constant-stress boundary conditions. We find that in natural gypsum alabaster with randomly oriented grains an increase in axial pre-stress leads to a significant acceleration of the dehydration rate. Simple estimates of the energy budget suggest that the acceleration of the dehydration rate due to elastic straining is significantly cheaper energetically than due to heating. We hypothesise that the observed strong effect of differential stress on dehydration kinetics can be explained by geometry-energy interactions in the granular sample microstructure.
Gravity-driven liquid splitting behavior at intersections and its control on infiltration in unsaturated fracture networks 
Authors: Yang Zhibing , Xue Song , Hu Ran , Chen Yi-Feng
Published: March 2021

A fundamental understanding of water infiltration in unsaturated fractured rocks is important in a range of subsurface hydrological, environmental and engineering applications. We perform an experimental and modeling investigation of the gravity-driven liquid slug flow behavior at fracture intersections. In the experiments, we visualize the flow processes and quantitatively analyze the flow dynamics. We develop a novel computational model that adequately captures the splitting dynamics. This model considers dynamic contact angles and solves temporal evolution of interface motion based on force balance with the quasi-static assumption at each time step. We systematically examine the influence of various physical parameters on the flow splitting behavior, including the widths and inclination angles of channels, and slug lengths. Using the local splitting relationships obtained mechanistically, develop a network model to study infiltration in unsaturated fracture networks. Then, the influence of the local flow dynamics on large-scale flow structures is systematically investigated. We find that an avalanche infiltration mode emerges spontaneously and that the local splitting relationship controls the divergent and convergent flow structures.
Reconstructing the long-term dynamic of pigmented communities in freshwater ecosystems using qPCR
Authors: Barouillet Cécilia , Rotschi Julie , Jenny Jean-Philippe , Lami Andrea , Etienne David , Domaizon Isabelle
Published: March 2021

The use of molecular biology tools in paleolimnological investigations provides promising opportunities to study the long-term dynamic of a broad spectrum of organisms and obtain a more comprehensive overlook at the overall lake biodiversity. In this study, we reconstruct the long-term dynamic of pigmented communities of three peri-alpine lakes (Leman, Annecy and Bourget) using the analysis of traditional paleolimnological proxies (i.e. diatom frustules, pigments) and quantitative PCR (qPCR) analysis of sedimentary DNA (sed-aDNA). We then compare the results with the phytoplankton data from decadal long limnological surveys. The goal being 2-fold: (1) to consolidate and reinforce the quantitative estimates derived from qPCR analysis of sed-aDNA, (2) reconstruct the long-term dynamics and identify the timing of changes of the pigmented communities in these lakes. We will present the preliminary results of this study and discuss the potential of this type of multi-proxy analysis to strengthen the application of molecular tools in paleolimnology.
How would irrigation enhance the global BECCS potential in view of sustainable water use?
Authors: Ai Zhipin , Hanasaki Naota
Published: March 2021

Bioenergy with carbon capture and storage (BECCS) plays a critical role in many stringent scenarios targeting the 2°C goal. Although irrigation is considered a promising way to enhance BECCS potential while reducing the land requirement, it is still unknown where and to what extent it can enhance the global BECCS potential in view of sustainable water use. Based on integrated hydrological simulations, we found that sustainable irrigation without intervention in water usage for other sectors and refrain from exploiting nonrenewable water sources enhanced BECCS potential by only 5–6% (much smaller than 60–71% for unlimited irrigation) above the rainfed potential by the end of this century. Nonetheless, it adds limited additional water withdrawal (166–298 km3 yr-1, corresponding to only 4–7% of the current total withdrawal) compared to that with unlimited irrigation (1392–3929 km3 yr-1, corresponding to 35–98% of the current total withdrawal).
High-frequency absorbance measurements for sediment source apportionment – laboratory and field assessment
Authors: Lake Niels , Martínez-Carreras Núria , Shaw Peter , Collins Adrian
Published: March 2021

To manage effectively excessive sediment inputs to rivers and streams, it is crucial to have detailed and reliable information on key sediment sources. Such evidence is important for implementing targeted measures for improving ecosystem functioning and meeting environmental objectives. Although sediment fingerprinting is increasingly adopted worldwide to provide such evidence, current procedures do not provide detailed information on how sediment sources can change over both short (e.g., events and in between events) and long (e.g., over seasons or years) time scales. These limitations are mainly due to the conventional methods used for target sediment sampling and the high workloads and costs associated with laboratory analyses for tracers, which limit both high-frequency and longer duration sampling campaigns. To address this issue, we propose the use of a submersible spectrophotometer, which measures absorbance in the UV-VIS range in situ and at high frequency (e.g., minutes) to trace suspended sediment sources. In our proof of concept investigation, the approach was first tested in a laboratory setting, using soil samples and artificial mixtures with known proportions of two, three and four soil source samples in an experimental water tank. A total of six soil samples were collected, which were sieved to different fractions to investigate the influence of particle size on the sensor absorbance readings. Both soil samples and artificial mixtures were suspended in the laboratory tank set-up at different concentrations to investigate the effects on: (i) absorbance, and; (ii) un-mixing accuracy. The results showed that absorbance was linearly additive and could be used to predict dominant samples in the artificial mixtures correctly using a Bayesian tracer un-mixing model, largely regardless of particle size and of the concentration inside the experimental tank. This approach is currently being tested in a field experiment in the Attert River Basin (Luxembourg) to investigate if the results found in the laboratory experiments hold under natural field conditions. Our preliminary insights into the use of absorbance for sediment source apportionment in the field will be presented.
Hydroclimate and atmospheric circulation over North Africa through the last two climatic cycles reconstructed from dust deposited off West Africa
Authors: Leblanc Maxime , Skonieczny Charlotte , Bory Aloys , Bout-Roumazeilles Viviane , Miska Serge , Abraham Romain , Delattre Marion , Nouet Julius , Malaizé Bruno
Published: March 2021

On glacial to interglacial time scales, northern Africa fluctuated between arid to hyperarid states and much wetter conditions called African Humid Periods (AHP). These AHP are characterized by a major transformation of the Saharan hydrological cycle, favoring the development of vast fluvial networks, tropical flora and fauna in a region previously hyperarid. In the present-day context of global warming, it is crucial to understand the environmental mechanisms and responses associated with these dramatic swings between two extreme climatic states in order to improve the climatic projections. Numerous studies have been focused on the last AHP, which occurred at the beginning of the Holocene and corresponds to a period when insolation - governed by precession – and obliquity both reached their maximum almost synchronously, thus complicating the distinction of their respective roles. The study of older AHP corresponding to different orbital configurations is likely to provide some answers. However, finding climatic archives allowing the reconstruction of past changes in the Saharan hydrological cycle on longer timescales remains challenging (e.g., discontinuity of continental archives, preservation of tracers…). In this study, we propose to circumvent this difficulty by studying the Saharan dust deposited in marine sediments of the northeastern Atlantic tropical ocean. In fact, past modifications of Saharan dust deposited off West Africa can provide precious information on changes in environmental conditions in their source areas (aridity, weathering), as well as on changes in the characteristics of their atmospheric transport (pathways and strength). Here, we present a unique high-resolution (1 sample/200yrs) multi-proxy characterization of the dust deposited continuously through the last 240ka - a period punctuated by eight AHP - in the marine core MD03-2705 (18°05N; 21°09W; 3085 mbsl) retrieved from a bathymetric dome, 300 meters above the surrounding seafloor. Considering this particular environmental setting, the terrigenous fraction in this record is assumed to be predominantly of eolian origin. We combine the 230Th-normalized dust flux1 together with grain-size distribution, clay mineralogy and geochemical compositions in order to explore changes in the Saharan hydroclimate and atmospheric circulation over North Africa on millennial to orbital timescales, with a particular focus on the mechanisms associated with the recurrence of the AHP.

1Skonieczny et al., 2019 – Science Advances 5 (1) - eaav1887
First year of real-time VOC measurements at the SIRTA facility (Paris region, France): diurnal and seasonal variabilities, impact of lockdowns on air quality
Authors: Simon Leïla , Gros Valérie , Petit Jean-Eudes , Truong François , Sarda-Esteve Roland , Baisnee Dominique , Bonnaire Nicolas , Dupont Jean-Charles , Haeffelin Martial , Marchand Caroline , Favez Olivier
Published: March 2021

Volatile Organic Compounds (VOCs) have direct influences on air quality and climate. They also play a key role in atmospheric chemistry, as they are precursors of secondary pollutants, such as ozone (O3) and secondary organic aerosols (SOA).

Long-term datasets of in-situ atmospheric measurements are crucial to characterize the variability of atmospheric chemical composition. Online and continuous measurements of O3, NOx and aerosols have been achieved at the SIRTA-ACTRIS facility (Paris region, France), since 2012. Regarding VOCs, they have been measured there for several years thanks to bi-weekly samplings followed by offline Gas Chromatography analysis. However, this method doesn’t provide a good representation of the temporal variability of VOC concentrations. To tackle this issue, online VOC measurements using a Proton-Transfer-Reaction Quadrupole Mass-Spectrometer (PTR-Q-MS) have been started in January 2020.

The dataset acquired during the first year of online VOC measurements is analyzed, which gives insights on VOC seasonal variability. The additional long-term datasets obtained from co-located measurements (O3, NOx, aerosol physical and chemical properties, meteorological parameters) are also used for the sake of this study.

Due to Covid-19 pandemic, the year 2020 notably comprised a total lockdown in France in Spring, and a lighter one in Autumn. Therefore, a focus can be made on the impact of these lockdowns on the VOC variability and sources. To this end, the diurnal cycles of VOCs considered markers for anthropogenic sources are carefully investigated. Results notably indicate that markers for traffic and wood burning sources behave quite differently during the Spring lockdown in comparison to the other periods. A source apportionment analysis using positive matrix factorization allows to further document the seasonal variability of VOC sources and the impacts on air quality associated with the lockdown measures.
Centennial to millennial-scale variability of Holocene climate and environmental dynamics in the western Mediterranean (Lake Sidi Ali, Middle Atlas, Morocco)
Authors: Schmidt Johannes , Kertscher Cathleen , Reichert Markus , Ballasus Helen , Schneider Birgit , Dietze Elisabeth , Tjallingii Rik , Benkkadour Abdelfattah , Mikdad Abdselam , Werther Lukas , Bolland Alexander , Pichat Sylvain , von Suchodoletz Hans , Fletcher William , Mischke Steffen , Zielhofer Christoph
Published: March 2021

The Western Mediterranean region including the North African desert margin is considered one of the most sensitive areas to future climate changes. In order to refine long-term scenarios for hydrological and environmental responses to future climate changes in this region, it is important to improve our knowledge about past environmental responses to climatic variability at centennial to millennial timescales. During the last two decades, the recovery and compilation of Holocene records from the subtropical North Atlantic and the Mediterranean Sea have improved our knowledge about millennial-scale variability of the Western Mediterranean palaeoclimate. The variabilities appear to affect regional precipitation patterns and environmental systems in the Western Mediterranean, but the timescales, magnitudes and forcing mechanisms remain poorly known. To compare the changes in Holocene climate variability and geomorphological processes across temporal scales, we analysed a 19.63-m long sediment record from Lake Sidi Ali (33°03’ N, 5°00’ W, 2080 m a.s.l.) in the sub-humid Middle Atlas that spans the last 12,000 years (23 pollen-based radiocarbon dates accompanied with 210Pb results). We use calibrated XRF core scanning records with an annual to sub-decadal resolution to disentangle the complex interplay between climate changes and environmental dynamics during the Holocene. Data exploration techniques and time series analysis (Redfit, Wavelet) revealed long-term changes in lake behaviour. Three main proxy groups were identified (temperature proxies: 2ky, 1ky and 0.7ky cycles; sediment dynamic proxies: 3.5ky, 1.5ky cycles; hydrological proxies: 1.5ky, 1.2ky, 0.17ky cycles). For example, redox sensitive elements Fe and Mn show 1ky cycles and higher values in the Early Holocene and 1.5ky cycles and lower values in the Mid- to Late Holocene. All groups show specific periodicities throughout the Holocene, demonstrating their particular climatic and geomorphological dependencies. Furthermore, we discuss these periodicities relating to global and hemispheric drivers, such as the North Atlantic Oscillation (NAO), El-Niño Southern Oscillation (ENSO), Innertropical Convergence Zone variability (ITCZ) and North Atlantic cold relapses (Bond events).
Combining Sentinel-1 and ALOS-2 observations for soil moisture retrieval
Authors: Balenzano Anna , Satalino Giuseppe , Lovergine Francesco , Palmisano Davide , Mattia Francesco , Rinaldi Michele , Montzka Carsten
Published: March 2021

One of the limitations of presently available Synthetic Aperture Radar (SAR) surface soil moisture (SSM) products is their moderated temporal resolution (e.g., 3-4 days) that is non optimal for several applications, as most user requirements point to a temporal resolution of 1-2 days or less. A possible path to tackle this issue is to coordinate multi-mission SAR acquisitions with a view to the future Copernicus Sentinel-1 (C&D and Next Generation) and L-band Radar Observation System for Europe (ROSE-L).

In this respect, the recent agreement between the Japanese (JAXA) and European (ESA) Space Agencies on the use of SAR Satellites in Earth Science and Applications provides a framework to develop and validate multi-frequency and multi-platform SAR SSM products. In 2019 and 2020, to support insights on the interoperability between C- and L-band SAR observations for SSM retrieval, Sentinel-1 and ALOS-2 systematic acquisitions over the TERENO (Terrestrial Environmental Observatories) Selhausen (Germany) and Apulian Tavoliere (Italy) cal/val sites were gathered. Both sites are well documented and equipped with hydrologic networks.

The objective of this study is to investigate the integration of multi-frequency SAR measurements for a consistent and harmonized SSM retrieval throughout the error characterization of a combined C- and L-band SSM product. To this scope, time series of Sentinel-1 IW and ALOS-2 FBD data acquired over the two sites will be analysed. The short time change detection (STCD) algorithm, developed, implemented and recently assessed on Sentinel-1 data [e.g., Balenzano et al., 2020; Mattia et al., 2020], will be tailored to the ALOS-2 data. Then, the time series of SAR SSM maps from each SAR system will be derived separately and aggregated in an interleaved SSM product. Furthermore, it will be compared against in situ SSM data systematically acquired by the ground stations deployed at both sites. The study will assess the interleaved SSM product and evaluate the homogeneous quality of C- and L-band SAR SSM maps.

 

 

References

Balenzano. A., et al., “Sentinel-1 soil moisture at 1km resolution: a validation study”, submitted to Remote Sensing of Environment (2020).

Mattia, F., A. Balenzano, G. Satalino, F. Lovergine, A. Loew, et al., “ESA SEOM Land project on Exploitation of Sentinel-1 for Surface Soil Moisture Retrieval at High Resolution,” final report, contract number 4000118762/16/I-NB, 2020.