bluuebunny/crossref_metadata_2025 huggingface dataset:
Sliding conditions beneath the Antarctic Ice Sheet
Authors: Gladstone Rupert , Moore John , Wolovick Michael , Zwinger Thomas
Published: March 2020

Computer models for ice sheet dynamics are the primary tools for making future predictions of ice sheet behaviour, the marine ice sheet instability, and ice sheet contributions to sea level rise. However, the dominant mode of flow for ice streams is sliding at the bed, and the physical processes that control sliding are not well understood. Ice sheet models often use hard-bed (often Weertman-type) sliding rules for computational efficiency.  However, soft beds with deformable sediments, which are known from laboratory experiments and direct glacier observations to exhibit Coulomb plastic behaviour, are ubiquitous beneath fast flowing ice streams. Using hard-bed sliding rules leads to actively misleading rates of inland surface diffusion and grounding line migration as compared to plastic beds, leading to incorrect forecasts of future sea level rise. Here, we use a 3D Stokes-flow ice sheet model along with observations of the Antarctic Ice Sheet to infer, through inversions and steady temperature simulations, key basal properties, most important of which are sliding speed, basal resistance, friction heat and grounded ice basal melt rate.  In addition to simulations of the whole Antarctic Ice Sheet we implement fine resolution simulations of the Pine Island Glacier and its catchment.  Contrary to the predictions of most hard-bed sliding relations, we find no correlation between basal resistance and sliding speed for fast moving ice streams. These results emphasize the importance of Coulomb plastic sliding, and strongly suggest that ice sheet modelers should devote greater efforts to developing models that can incorporate Coulomb plastic sliding relations without generating numerical instabilities.  We use our model results, along with some assumptions, to infer properties of the sub-glacial hydrologic system.  Assumptions about connectivity of the sub-glacial hydrologic system to the ocean limit our capacity to assess sliding relations that incorporate a dependence on effective pressure, and likely cause underestimates of ice sheet mass loss in model-based predictions utilising such sliding relations.  Hydrology modelling is likely essential both to further assess sliding relations and to use sliding relations in future predictions.  We estimate that the dominant source of basal meltwater for Pine Island Glacier is due to friction heat caused by basal sliding, despite recent estimates of high heating due to volcanic activity.

 
Turn climate information into value for the Mediterranean wine sector: the MED-GOLD potential
Authors: Dell'Aquila Alessandro ,   the MED-GOLD Wine Service Team
Published: March 2020

MED-GOLD is an EU-funded Horizon 2020 project (https://www.med-gold.eu/) whose main objective is to demonstrate the proof-of-concept for climate services in agriculture by developing case studies for three staples of the Mediterranean food system: grapes, olives and durum wheat.

MED-GOLD will propose climate services deploying forecast information at seasonal (next 6 months) and long-term (next 30 years). This information will be provided at higher spatial resolution than what is currently available. To provide the highest value for decision-making, the services will be co-developed with professional users from each sector.

For the wine sector, the project objective is to use the most recent state-of-the-art climate models outputs to produce user-oriented predictions of essential climate variables, bioclimatic indicators  and ad-hoc implemented compound risk indices. All of these indices  are relevant for viticulture at large scales, and more specifically for the MED-GOLD focus region of the Douro valley (Portugal). The indices  will be readily available for users in the grape and wine sector under several different formats and visualizations, allowing for easy, quick and seamless integration into critical decision-making.

Timely warnings of when climate change might impose a disruptive pressure upon wine production systems offers stakeholders a chance to act proactively both at seasonal (operational campaign planning) and decadal (strategic business planning) time-scales, making the wine sector more resilient to the impacts of climate change.
Watch and Learn: Promoting Student Autonomy and Competence in the Field with Just-in-Time Knowledge Clips
Authors: Trabucho Alexandre João , de Bresser Hans , Cuesta Cano Andrea , Veenma Yorick
Published: March 2020

The ultimate aim of field courses should be to enable students to work autonomously in the field. We should therefore organize learning activities during which students work autonomously in the field. Student- and problem-centered approaches to learning in the field afford students much autonomy, but unlike in the more traditional show-and-tell approach, independent projects have so far required that students spend a significant amount of time working in the field without access to supervision. Unless students are competent enough to experience proficiency and a feeling of controlling the quality of their own work, such autonomy is detrimental to student motivation.

Short knowledge clips that meet the immediate need of a student exactly when it arises are an interesting form of blended learning that promotes student autonomy and competence. Just-in-time knowledge clips can (a) provide further information and insights into a key question; (b) complement students’ background knowledge and help refresh their memory on important concepts; and/or (c) demonstrate techniques needed to acquire field data successfully. Knowledge clips, by their very nature, help students learn visual subjects, such as structural and sedimentary geology in the field.

Students no longer need to wait to get the contact time they need to move on with their work: they can watch (a knowledge clip) and learn just-in-time. Face-to-face time in the field with an instructor can then be used to achieve higher-order learning outcomes, focusing not on acquiring knowledge but on gaining insight and understanding.
Applied magnetic cartography is a tool for understanding the self-organization of the planet Earth system and its energy supply
Authors: Litvinova Tamara , Кашик Дмитрий , Тихомиров Сергей
Published: March 2020

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The energy supply of geodynamic processes is one of the most important factors in the evolution of the planet earth system.The continuity and relatively stable regime of the planetary dipole magnetic field of the Earth is due, first of all, to the constant level of rotation energy continuously generated by the Earth during its rotation around its axis. In the mantle, asthenosphere, and the earth's crust, the determining energy factor is the density inhomogeneity of matter.

The Earth’s magnetic field, which is 99% generated by its internal sources, responds to phase transitions, which are the basis of the processes of self-organization of the planet Earth system.

The report presents ideas about energy sources, mechanisms and patterns of formation, transformation and replenishment of its reserves will significantly increase the reliability of the interpretation of cartographic information about structural and geophysical anomalies and related mineralogenesis processes.
Multiple drivers of seasonal and interannual variation in Pmax: Implications for leaf photosynthesis of Artemisia ordosica
Authors: Tian Yun , Zha Tianshan , Jia Xin
Published: March 2020

Revealing the seasonal and interannual variations in leaf-level photosynthesis is a critical issue in understanding the ecological mechanisms underlying the dynamics of carbon dioxide exchange between the atmosphere and shrub ecosystem. Artemisia ordosica is a dominant shrub species in semi-arid area of northwest China. Photosynthetic gas exchange, leaf nitrogen content(LN), specific leaf area (SLA) and some environmental factors were measured simultaneously on clear days (rotated every 10 days) of the growing season from 2011 to 2018, to quantify the temporal variations and environmental controls of photosynthetic parameters. Our results demonstrated that mean value of light-response curve parameters, the maximum photosynthetic capacity (Pmax), appear quality efficiency (AQE), respiration in dark (Rd), light saturated point (LSP) and light compensated point (LCP) had a gradual decline with the growth (spring> summer>autumn). Structural equation modeling (SEM) was used to elucidate the direct and indirect effects of biophysical factors on Pmax. The driven factors of Pmax in growing season changed, but stomatal conductance (gs) was the dominant factor in all stages. The gs was influenced by SLA and LN，and the soil water content at a depth of 10cm (SWC10) affected the Pmax in spring. In summer, Pmax was significantly positively related with gs and transpiration rate (Tr), and gs was influenced by SLA, LN and soil water content at a depth of 30cm (SWC30). In autumn, Pmax was significantly positively correlated with gs, while was significantly negatively correlated with air temperature (Ta). This simulation based on situ ecophysiological research suggest that Pmax of A. ordosica responded to the environment factors of seasonal and interannual variations, which is not the inherent genetic characteristics. Soil water content is the major environmental factor influencing Pmax in spring and summer, while Ta is the major one in autumn. Knowledge of how environmental change will affect the photosynthesis of A. ordosica in the future is essential for their protection, adaptation strategies and carbon fixation prediction in shrub ecosystems.
Expected impact of the 2016 central Italy earthquakes on the local gravity field
Authors: Riguzzi Federica , Tan Hongbo , Shen Chong-yang
Published: March 2020

We have modelled the surface volume and gravity changes caused by the three mainshocks (moment magnitudes Mw 6.0, 5.9, 6.5) occurred during the last seismic period started on 2016, August 24 in central Italy. Our calculations start from the source parameters estimated by the inversion of the largest dataset of InSAR and GNSS observations ever managed in Italy after earthquake occurrences, based on the half-space elastic dislocation theory. The vertical displacements modelled after the 2016 events allow to infer a substantial unbalance between the subsided and uplifted volumes. In particular, we detected ~106∙106 m3 of hangingwall subsidence against ~37∙106 m3 of footwall uplift, that accounts for ~74% of the total volume mobilization. From the ratio between the footwall and total deformed volumes, we have computed an average fault dip of ~47°, in line with the values retrieved by seismological methods. The total gravity variations which affected the study area are of the order of ~1 μGal (1 μGal = 10−8 ms−2) in the far field, and ~170 μGal in the near field.
The area affected within a gravity change of 1 μGal is ~140 km long and ~57 km wide, parallel to the Apennines chain. The larger contribution is given by positive variations which account for the tensional style of deformation and larger subsided area.
Climate impact on Earth rotation speed from CMIP6 model simulations
Authors: Böhm Sigrid , Salstein David
Published: March 2020

The Coupled Model Intercomparison Project (CMIP) is an effort to investigate the past, present and future state of a number of Earth system variables, using a variety of models developed by research centers around the globe. This broad initiative aims at understanding climate signals due to both natural variability and in response to changing radiative forcing. One of the so-called endorsed MIPs of the CMIP phase 6, the ScenarioMIP, is dedicated to providing multi-model climate projections based on alternative scenarios of future emissions and land use changes linked to socioeconomic factors. The climate of the 21st century is simulated based on different forcings, which are defined from a combination of possible future pathways of societal development, the Shared Socioeconomic Pathways (SSPs), and the Representative Concentration Pathways (RCPs), identified by what radiative forcing level might exist in 2100.

Our study will examine the integrated effect of atmosphere and ocean variability on the Earth rotation speed, represented as changes in the length of day (LOD). Angular momentum variations due to mass and motion terms will be calculated from different models for the four most prominent scenarios as well as for historical simulations. We will also analyze spatial patterns of the respective variables in order to identify those regions in the atmosphere and oceans that contribute the most to LOD excitation. Finally, we will compare trends in the total axial angular momentum functions among each other and to trends in the global temperature to show the influence of global warming on the rotation rate.
The role of calcium diffusion on high temperature SO2 uptake by volcanic glasses
Authors: Casas Ana S. , Wadsworth Fabian B. , Ayris Paul M. , Delmelle Pierre , Vasseur Jérémie , Cimarelli Corrado , Dingwell Donald B.
Published: March 2020

Glass-SO₂ reactions occurring at high temperatures in (terrestrial and extraterrestrial) volcanic environments have received increasing attention in the past years (e.g., Renggli and King 2018; Casas et al. 2019; Renggli et al. 2019), based on both natural and experimental observations. Laboratory studies carried out at high temperatures (>200 °C) demonstrate that volcanic glass in the presence of SO₂ reacts to form surficial sulfate-bearing minerals (e.g., Ayris et al. 2013; Delmelle et al. 2018), mostly calcium sulfate salts (CaSO₄). Thus, high temperature glass-SO₂ interaction acts as a sink for the magmatic S released during explosive volcanic activity, potentially impacting the S budget of large explosive eruptions. Here, we present the results of new experiments aimed at assessing the influence of the glass Ca content on SO2 uptake in the temperature range of 600-800 °C. We exposed haplogranitic glasses to SO₂ for diverse time exposures (5-30 minutes). Rhyolitic composition was chosen due to the ubiquity of Si-rich magmas in large explosive eruptions (Cioni et al. 2000).

The experimental glasses were synthesized with an initial HPG8 composition (see Holtz et al. 1992), doped with 1 and 2 wt.% CaO. Furthermore, the role of Fe was tested by doping the glasses with 0, 0.1, 1, 1.5, 2 and 2.5 wt.% FeO and equilibrating them at 1500 °C. Leachates of post-treated glasses were analyzed by ion chromatography in order to determine SO2-uptake and the nature of the sulfate-bearing minerals formed by solid-gas reactions. The bulk redox state of iron (Fe³⁺/Fetotal), was obtained by the K₂Cr₂O₇ potentiometric titration method. Our results show a strong correlation between the amount of Ca in the glasses and the formation of CaSO₄ surficial deposits (i.e. SO₂ uptake), i.e. the HPG8 + 2 wt.% CaO treated samples produced up to 40 % more CaSO₄ than the samples containing 1 wt.% CaO. Higher Fe content in the glass also enhanced formation of CaSO₄. In contrast, the absence of Fe oxide resulted in preferential formation of Na₂SO₄ and K₂SO₄, when compared to the Fe-bearing specimens. Our experiments confirm that high temperature SO₂ uptake by glass is strongly dependent on the Ca content and temperature, with the optimal reaction temperatures being ≥600 °C. Increasing the amount of FeO in the glasses seems to enhance SO2 uptake, although this effect appears to be different for Ca than for Na or K, pointing out a more complex influence of redox dynamics on cation diffusion.

 
Flood trends in Africa
Authors: Tramblay Yves , Villarini Gabriele
Published: March 2020

African countries are highly vulnerable to floods, with the fatalities and economic impacts associated with this hazard that have increased over the last decades. Despite the importance of the topic, little is known about the changes in the flood hazard over the second half of the 20th and the first two decades of the 21st century. Here we quantify the temporal changes in flooding using a newly assembled database of daily river discharge observations. The dataset contains over 700 stations having at least 20 years of daily data between 1950 and 2017. The database includes rivers from most sub-regions of Africa and sample a wide range of catchment sizes. Flood analyses are based on both annual maxima and peak-over-threshold to examine the changes in the frequency and magnitude of these events. Seasonal patterns of flood occurrence are also investigated through a regionalization based on directional statistics and monthly flood occurrence. Results indicate that, at the continental scale, there are more rivers with statistically significant downward trends. Yet, the spatial patterns exhibit regional variations, with several rivers showing increasing trends in central and South Africa. These findings are robust when considering longer times series or different sampling strategies for extremes.  
Treasure maps, sustainable development, and the billion-year stability of cratonic lithosphere
Authors: Hoggard Mark , Czarnota Karol , Richards Fred , Huston David , Jaques Lynton , Ghelichkhan Sia
Published: March 2020

Sustainable development and transition to a clean-energy economy is placing ever-increasing demand on global supplies of base metals (copper, lead, zinc and nickel). Consumption over the next ~25 years is set to exceed the total produced in human history to date, and it is a growing concern that the rate of exploitation of existing reserves is outstripping discovery of new deposits. Therefore, improvements in the effectiveness of exploration are required to reverse this worrying trend and maintain growth in global living standards.

Approximately 70% of known lead, 55% of zinc and 20% of copper has been deposited between 2 Ga and recent by low temperature hydrothermal circulation in shallow sedimentary basins. These basins are formed by extension and rifting, which are key manifestations of the plate-mode of tectonics. Despite 150 years of research, the relationship between deposit locations and local geological structure is enigmatic and there remains no accurate technique for predicting their distribution at continental scales.

Here, we show that modern surface wave tomography and recent parameterisations for anelasticity at seismic frequencies can be used to map lithospheric structure, and that sediment-hosted base metal deposits occur exclusively along the edges of thick lithosphere. Approximately 90% of the world's sediment-hosted copper, lead and zinc resources lie within 200 km of these boundaries, including all giant deposits (>10 megatonnes of metal). Incorporation of higher resolution regional seismic studies into global lithospheric thickness models further enhances the robustness of this relationship. 

This observation implies that lithospheric architecture imparted by the plate-mode of tectonics is stable over billion-year timescales, and that there is a genetic link between lithospheric scale  processes and near-surface hydrothermal mineral systems. Our new maps provide an unprecedented global means to identify fertile regions for targeted mineral exploration, and provide a clear economic justification for funding targeted seismic arrays, theoretical advances in imaging techniques, and geodynamic studies that improve our understanding of deep-time plate tectonics.
Satellite altimetry for hydraulic model calibration: potential of single and multi-mission series
Authors: Molari Giada , Domeneghetti Alessio , Tourian Mohammad , Tarpanelli Angelica , Moramarco Tommaso , Sneeuw Nicolaas
Published: March 2020

The recent improvement of satellite products has provided an increasing data availability with an unprecedented coverage, stimulating their usage in hydraulic and hydrological fields. Notwithstanding, regarding the satellite water level monitoring, the limited temporal resolution (i.e. revisit time varying from 10 to 35 days) and decimeter accuracy of  altimetry satellites strongly restrict their applications. Recently proposed multi-mission (MM) densified time series might represent a possible alternative to ensure higher spatial and temporal coverage. However, an assessment of the potential of different altimetry products, including MM series, for hydrodynamic model calibration is still missing. The goal of this study is the assessment of remotely sensed water surface elevations usefulness for the calibration of a hydraulic model implemented for a 140-km stretch of the Po River (Italy). In particular this study presents: i) a comparison of altimetry satellite data collected from different missions (ENVISAT (E), ENVISAT extended (EX), TOPEX/Poseidon (TP), SARAL/AltiKa (SA), Jason-2 (J2) and Jason-3 (J3); ii) insights to the effects of satellite series length on hydraulic model calibration; iii) the analysis of how data uncertainty influences model accuracy; iv) the potential of multi-mission (MM) densified time series as possible alternative to overcome spatial and temporal limitations of single mission. The results highlight a good agreement among satellite and in-situ observations for all the series, excluding EX series. J2 provides the best outcome in terms of calibration error (about 30 cm) and number of measurements required to achieve a reliable calibration (less than 1 year of data). In case of frequent and accurate satellite data (i.e. J2 and TP), the MM series seem unable to provide additional benefits in calibrating the hydraulic model. On the other hand, MM series outperform low frequency products (i.e. E and SA) when the latter are available only for short period. This research offers a wide overview of the potential of altimetry products, providing a general comparison of different satellite missions series and showing the potential, as well as limitations, offered by multi-mission series.
Connecting big data from climate and biology using statistics and machine learning techniques
Authors: Pfeifer Susanne , Bülow Katharina , Marien Lennart
Published: March 2020

Within the Hamburg Cooperation project „HYBRIDS – Chances and Challenges of New Genomic Combinations“ (https://www.biologie.uni-hamburg.de/en/forschung/verbundvorhaben/hybride-mehr-infos.html), one subproject deals with the problem of finding relations between the existance of hybrid plant species and the climate and its variability at the same location. For this, biological and climatic data is brought together and statistical and machine learning techniques are applied to derive climatic differences between those regions where both parent species, but no hybrid species are found, and those regions where both parent species and the hybrid species were found.

Both the climate data (here daily gridded E-OBS temperature (mean, min, max) and precipitation on ~10 km grid resolution for the period of 1970 to 2006 (Haylock et al.,2008, Cornes et al., 2018)) and the plants data (Hybrid Flora of the British Isles, 700 taxa, 6 112 847 lines of data, (Stace et al., 2015)) can be considered as „big data“. However, the peculiarities of both data are very different and so are the issues to be considered when tackling the data.

We will present the first results of this interdisciplinary effort, discuss the methodological issues and elaborate on the chances and challenges of interpreting the findings.

 

Cornes, R., G. van der Schrier, E.J.M. van den Besselaar, and P.D. Jones. 2018: An Ensemble Version of the E-OBS Temperature and Precipitation Datasets, J. Geophys. Res. Atmos., 123.

Haylock, M. R., Hofstra, N., Klein Tank, A. M. G., Klok, E. J., Jones, P. D. & M. New (2008): A European daily high-resolution gridded data set of surface temperature and precipitation for 1950-2006. Journal of Geophysical Research Atmospheres, 113(20). https://doi.org/10.1029/2008JD010201

Stace, C.A., Preston, C.D. & D.A. Pearman (2015): Hybrid flora of the British Isles. Botanical Society of Britain & Ireland. 501pp.
Sentinel products assimilation in a complete hydro/fire-meteorological chain: nearly operational experiments in the framework of the E-SHAPE project
Authors: Lagasio Martina , Meroni Agostino N. , Pulvirenti Luca , Squicciarino Giuseppe , Parodi Antonio , Tsouni Alexia , Kontoes Haris , Bartsotas Nikos
Published: March 2020

In the framework of the E-SHAPE “EuroGEO Showcase: Applications Powered by Europe” project, the Pilot 2 application of the Disasters Resilience Showcase concerns the disasters in urban environment. Starting from the results and methodologies analyzed in the framework of the STEAM project, the E-SHAPE pilot exploits the new capacities for designing and delivering innovative services for extreme-scale fire/hydro-meteorological modelling chain assimilating Copernicus data and core services directly ingested through the Copernicus Open Access Hub APIS, and the DIAS platform, as well as citizen scientists data, to enable more precise predictions and decision-making support for high impact events in urban and peri urban environment. Contributing to the Disaster Resilience SBA, one of the main activities listed in the GEO Space and Security Community Activity is to get maximum benefit from the use of large and heterogeneous datasets to potentially fill in the observational and capability gaps at EU decision making level. To this end, the application proposes also the integration of the datasets and tools made available in the frame of the pilot application (weather, citizen science, hydrological and fire models included in CIMA’s Platforms Dewetra and RASOR and NOA’s BEYOND Systems FireHub and FloodHub) for the impact assessment of natural hazards over areas of interest with regard to human security issues. An example of innovative service is the ingestion of high-resolution Copernicus remote sensing products in Numerical Weather Prediction (NWP) models. The rationale is that NWP models are presently able to produce forecasts with a spatial resolution in the order of 1 km, but unreliable surface information or poor knowledge of the initial state of the atmosphere may imply an inaccurate simulation of the weather phenomena. It is expected that forecast inaccuracies could be reduced by ingesting high resolution Earth Observation products into the models. In this context, the Copernicus Sentinel satellites represent an important source of data, because they can provide a set of high-resolution observations of physical variables (e.g. soil moisture, land/sea surface temperature, wind over sea, columnar water vapor) used in NWP model runs. The possible availability of a spatially dense Personal Weather Stations network could also be exploited to allow NWP models to assimilate timely updated data such as temperature, humidity and pressure. In this work a preliminary experiment design and methodology will be presented.
Comprehensive Analysis of the Magnetic Signatures of Small‐Scale Traveling Ionospheric Disturbances, as Observed by Swarm
Authors: Yin Fan , Lühr Hermann , Park Jaeheung , Wang Ling
Published: March 2020

Based on Swarm satellite data from 2015 through 2018, we present the mean characteristics of

magnetic fifield flfluctuations at midlatitudes and low latitudes. It is the fifirst comprehensive study focusing on

small‐scale variations (<10 km). Events are observed on about 35% of the orbits. The highest occurrence

rates are detected after sunset, in the East Asian/Australian sector, and during months around June solstice.

Low occurrence rates are found at low magnetic latitudes (below ±10° quasi‐dipole latitude), in the region

of the South Atlantic Anomaly, and during equinox seasons. All these occurrence features compare well

with those of medium‐scale traveling ionospheric disturbances. We therefore term our small‐scale events

small‐scale traveling ionospheric disturbances (SSTIDs). SSTIDs exhibit high fifield‐aligned current (FAC)

densities connected to narrow current sheets with meridional width of typically 4 km. The intense FACs of

several μA/m2 flflow typically between the hemispheres. Return currents are distributed over larger scales

and thus have smaller amplitudes. Peak current densities get larger toward lower latitudes. There are two

groups of events, around morning‐noontime and evening‐night, which are separated by demarcation lines

near 04 and 15 magnetic local time. The magnetic amplitudes of the small‐scale flfluctuations are larger in

sunlight than in darkness, indicating larger total currents in the loops. But the FAC peak current densities

are larger in darkness, inferring a stronger squeezing of the current sheet under low‐conductivity conditions.

We suggest that our SSTIDs are an evolutional state of medium‐scale traveling ionospheric disturbances.
Analyzing different ways of assimilating volume change estimates for surface water bodies into a hydrological model
Authors: Engels Olga , Schulze Kerstin , Kusche Jürgen , Deggim Simon , Eicker Annette , Mayr Stefan , Klein Igor , Ellenbeck Laura , Dettmering Denise , Schwatke Christian , Elmi Omid , Tourian Mohammad , Döll Petra
Published: March 2020

To better understand global freshwater resources, we combine the state-of-the-art global hydrological model WGHM with Total Water Storage Anomalies (TWSA) derived from the Gravity Recovery and Climate Experiment (GRACE) satellite mission in an ensemble-based calibration and data assimilation (CDA) framework. However, when dealing with GRACE data, their limited horizontal resolution represents a major challenge. Filtering and/or ’destriping’ is the usual approach for suppressing GRACE-specific spatial noise, which causes spatial leakage and in turn attenuation of signal and reduction of spatial resolution. In GlobalCDA project, we derive altimetry-based storage variations along with corresponding uncertainties of surface water bodies, such as lakes and reservoirs, that feature significantly higher spatial resolution compared to GRACE-based TWSA. These can, additionally, be incorporated into the CDA framework.

In this study, we investigate several possibilities on how to use the additional remote sensing observations within the CDA over the Mississippi basin for the time span 2003 - 2016. For this, we run the CDA (i) using GRACE-based TWSA only, (ii) removing altimetry-based storage variations of surface water bodies from GRACE-TWSA, (iii) removing and restoring altimetry-based storage variations for GRACE-TWSA, and (iv) directly using altimetry-based storage variations. New observation operators are constructed for (ii) and (iv). The results are validated against independent discharge observations.
Can seafloor voltage cables be used to study large scale transport? An investigation in the Pacific Ocean.
Authors: Schnepf Neesha , Nair Manoj , Velimsky Jakub , Thomas Natalie
Published: March 2020

Marine electromagnetic (EM) signals largely depend on three factors: oceanic transport (i.e., depth-integrated flow), the local main magnetic field, and the local seawater conductivity (which depends on the local temperature and salinity). Thus, there is interest in using seafloor telecommunication cables to isolate marine EM signals and study ocean processes because these cables measure voltage differences between their two ends. Data from such cables can provide information on the depth-integrated transport occurring in the water column above the cable. However, these time-varying data are a superposition of all EM fields present at the observatory, no matter what source or process created the field. The main challenge in using such submarine voltage cables to study ocean circulation is properly isolating its signal.

 

Our study utilizes voltage data from retired seaoor telecommunication cables in the Pacific Ocean to examine whether such cables could be used to monitor transport on large-oceanic scales. We process the cable data to isolate the seasonal and monthly variations, and evaluate the correlation between the processed data and numerical predictions of the electric field induced by ocean circulation. We find that the correlation between cable voltage data and numerical predictions strongly depends on both the strength and coherence of the transport owing across the cable. The cable within the Kuroshio Current had the highest correlation between data and predictions, whereas two of the cables in the Eastern Pacific gyre (a region with both low transport values and interfering transport signals across the cable) did not have any clear correlation between data and predictions. Meanwhile, a third cable also located in the Eastern Pacific gyre did have correlation between data and predictions, because although the transport values were low, it was located in a region of coherent transport flow across the cable. While much improvement is needed before utilizing seafloor voltage cables to study and monitor oceanic transport across wide oceanic areas, we believe that the answer to our title's questions is yes: seafloor voltage cables can eventually be used to study large-scale transport.
Transport of formaldehyde in water unsaturated laboratory columns packed with quartz sand: Effect of colloid-sized clay particles.
Authors: Fountouli Theodosia V. , Chrysikopoulos Constantinos V.
Published: March 2020

Colloid-sized clay particles are in great abundance in the unsaturated or vadose zone and are capable of binding a variety of contaminants, which in turn either facilitate or hinder their migration in the subsurface. Also, FA has relatively strong affinity for kaolinite colloid particles (Fountouli et al., 2019). This study examines the effects of two representative colloid-sized clay particles (kaolinite, montmorillonite) on the transport of formaldehyde (FA) in unsaturated porous media. Transport experiments were performed in columns packed with quartz sand, under unsaturated conditions. The transport of FA was examined with and without the presence of suspended clay particles under various flow rates and various levels of saturation. DLVO interaction energies and the capillary potential energy associated with colloid retention at air-water and solid-water interfaces were calculated. The experimental results clearly suggested that the presence of suspended clay particles hindered the transport of FA in unsaturated packed columns. Moreover, as expected, it was shown that clay particle retention in the packed column increased with decreasing level of water saturation.

 

Reference

Fountouli, T.V., C.V. Chrysikopoulos, and I.K. Tsanis, Effect of salinity on formaldehyde interaction with quartz sand and kaolinite colloid particles: batch and column experiments. Environmental Earth Sciences 78, 152, 2019.

 
Seismic expressions of the Yongle Atoll and the Sansha Yongle Blue Hole in the Xisha Islands, Northwestern South China Sea
Authors: Gao Jinwei , Zhang Hanyu , Wu Shiguo , Ma Benjun , Chen Wanli , Han Xiaohui , Liu Gang , Tian Liyan
Published: March 2020

Sansha Yongle Blue Hole is an oceanic blue hole and is located at the northeastern edge of the Yongle Atoll, in the Xisha Islands of the northwestern South China Sea. The 301.19 m deep makes it to be the deepest known blue hole in the world. Despite the 3-D morphology, hydrochemical properties and chemocline of the blue hole have been comprehensive investigated, its karst formation process is still enigmatic. This study presented new acquired multi-channel seismic data across the Yongle Atoll and seismic data across the Sansha Yongle Blue Hole to describe the seismic reflection characteristics of the carbonate platform and the blue hole in extensive detail. Combined with the scientific wells drilled on the atoll, our results show that carbonate sequences including Lower Miocene, Middle Miocene, Upper Miocene, Pliocene and Quaternary developed on the platform. The magmatically intrusive activity and related magmatic hydrothermal fluid flows have been very active since 5.5 Ma around/on the Yongle Atoll, and may remain active on both slopes and the carbonate platform of the Yongle Atoll at present. Seismic profiles also show that the blue hole is characterized by chaotic seismic reflections which are easily distinguished from surrounding carbonate rocks with sub-parallel, continuous, low to medium amplitude, and low to medium seismic reflections. It seems that the depth of the blue hole is deeper than that measured according to the seismic images. The results of δ18O from scientific wells show that the phreatic extent in the Xisha Islands is from 14.75 – 38.89 m to 152.06 – 183.29 m. Therefore, different from other classic karstological blue holes formed by the phreatic dissolution processes, a hydrothermal – phreatic model with magmatic hydrothermal pipes and collapse of deep seated phreatic dissolution voids was proposed to describe the formation of the Sansha Yongle Blue Hole.
Sensitivity of soil moisture to climate variability in the Mediterranean region
Authors: Mimeau Louise , Tramblay Yves , Brocca Luca , Massari Christian , Camici Stefania , Finaud-Guyot Pascal
Published: March 2020

Studies on future precipitation trends in the Mediterranean region show a possible decrease in annual precipitation amounts with an intensification of extreme events in the coming years. A major challenge in this region is to evaluate the impacts of changing precipitation patterns on extreme hydrological events such as droughts and floods. For this, it is important to understand the effects of changing temperature and precipitation on soil moisture since it is a good proxy for drought monitoring and it plays a key role on flood runoff generation. This study focuses on 11 sites located in the South of France, with soil moisture, temperature, and precipitation observations over a 10 year time period. Soil moisture is simulated at the hourly time step for each site using a soil moisture model based on the Green-Ampt infiltration scheme. The elasticity of the simulated soil moisture to different changes in precipitation and temperature is analyzed by simulating the soil moisture response to temperature and precipitation changes, generated using a delta change method for temperature and a stochastic model (Neyman-Scott rectangular pulse model) for precipitation. Results show that soil moisture is more impacted by changes in precipitation intermittence than precipitation intensity and temperature. Although there is variability in the soil moisture response to the considered forcing scenarios, increased temperature combined to increased precipitation intensity and intermittency leads to decreased median soil moisture and an increased number of dry days.
Magnetic to the Core - Communicating paleomagnetism with hands-on activities
Authors: van der Boon Annique , Paterson Greig , Kavanagh Janine , Biggin Andy
Published: March 2020

With geoscience student numbers dwindling, there is a strong need for Earth scientists to enthuse a new generation of prospective students. We created several hands-on activities to introduce members of the general public of all ages to the fundamentals of, and current research in paleomagnetism. We developed these activities at different outreach events in the UK, such as a family science fair (at the Ness Gardens) and a holiday workshop (at the Victoria Gallery & Museum). In the first week of July, 2019, we contributed to the Royal Society Summer Science Exhibition, a science exhibition in London with almost 14,000 visitors of the general public, including many school groups. Visitors came from all educational backgrounds. We had a stand that consisted of 4 hands-on experiments, and an informative backdrop. The four activities allowed visitors to explore the range of tasks that a paleomagnetist does, from the collection and measurement of samples to understanding the behaviour of the Earth’s magnetic field. Visitors could measure real lavas from Iceland on a custom-built magnetometer that was designed specifically for outreach, and determine the magnetic polarity of the samples. We also created an information booklet with ’10 things you might not know about Earth’s magnetic field’, which is openly available under a CC-license. To measure the impact of our stand on visitors’ knowledge of paleomagnetism, we designed a quiz. Our results show that especially for school kids, our stand had a significant impact on their knowledge of the Earth’s magnetic field. In this contribution we share lessons learned through designing the ‘Magnetic to the Core’ stand, hands-on activities and evaluations.
Fracture reactivation for permeability enhancement in geothermal systems
Authors: Kushnir Alexandra , Heap Michael , Baud Patrick , Reuschlé Thierry
Published: March 2020

While the deep granitic basement in the Upper Rhine Graben is currently being exploited as a geothermal reservoir at numerous geothermal sites, the Permo-Triassic sandstones that lie directly above the granite are critical to continued regional hydrothermal convection. Here we investigate the propensity for variably sealed fractures to be reactivated during deformation and the role this fracture reactivation plays on permeability enhancement in geothermal reservoirs. We source un-fractured, bedded sandstones and the same bedded sandstones containing a single, variably-sealed fracture from a 400 m-thick unit of Permo-Triassic sandstone sampled from the EPS-1 exploration well near Soultz-sous-Forêts (France) in the Upper Rhine Graben.

31 cylindrical samples (20 mm in diameter and 40 mm long) were cored such that their dominant structural feature (i.e. bedding or natural fracture) was oriented parallel, perpendicular, or at 30° to the sample axis. The initial permeability of the un-fractured samples ranged between 2.5×10-17 and 5.6×10-16 m2 and between 3.6×10-16 and 3.3×10-14 m2 for naturally fractured samples. In un-fractured samples, permeability decreases as a function of increased bedding angle; fracture orientation, however, does not appear to have a discernable influence on permeability. Samples were water-saturated and deformed until failure under pressure conditions appropriate to the Soultz-sous-Forêts geothermal system - Peff of 14.5 MPa - and at a strain rate of 10-6 s-1. All samples developed through-going shear fractures, however, only in samples containing partially sealed fractures did the experimentally produced fractures take advantage of the pre-existing features. In samples containing a fully-sealed fracture, the experimentally induced fracture developed in a previously undeformed part of the sandstone matrix. Further, post-deformation permeability measurements indicate that while sample permeability increased by up to one order of magnitude for a given sample, this increase is generally independent of feature orientation.

Therefore, formations containing sealed fractures may not necessarily be weaker and, as a consequence, may not be more apt to significant permeability increases during stimulation than un-fractured formations. These data can contribute to the development and optimization of stimulation techniques used in the Upper Rhine Graben.
Estimating global mean sea-level rise and its uncertainties by 2100 and 2300 from expert assessment
Authors: Horton Benjamin , Khan Nicole , Cahill Niamh , Lee Janice , Shaw Tim , Garner Andra , Kemp Andrew , Engelhart Simon , Rahmstorf Srefan
Published: March 2020

Sea-level rise projections and knowledge of their uncertainties are vital to make informed mitigation and adaptation decisions. To elicit expert judgments from members of the scientific community regarding future global mean sea-level (GMSL) rise and its uncertainties, we repeated a survey originally conducted five years ago. Under Representative Concentration Pathway (RCP) 2.6, 106 experts projected a likely (at least 66% probability) GMSL rise of 0.30–0.65 m by 2100, and 0.54–2.15 m by 2300, relative to 1986–2005. Under RCP 8.5, the same experts projected a likely GMSL rise of 0.63–1.32 m by 2100, and 1.67–5.61 m by 2300. Expert projections for 2100 are similar to those from the original survey, although the projection for 2300 has extended tails and is higher than the original survey. Experts give a likelihood of 42% (original survey) and 45% (current survey) that under the high emissions scenario GMSL rise will exceed the upper bound (0.98 m) of the likely (i.e. an exceedance probability of 17%) range estimated by the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Responses to open-ended questions suggest that the increases in upper-end estimates and uncertainties arose from recent influential studies about the impact of marine ice cliff instability on the meltwater contribution to GMSL rise from the Antarctic Ice Sheet.
Seismic characterization of clays blocks ruptures in a clayey landslide, the Harmaliere landslide.
Authors: Fiolleau Sylvain , Jongmans Denis , Bièvre Gregory , Chambon Guillaume , Baillet Laurent
Published: March 2020

Many regions of the world are exposed to landslides in clayey deposits, which pose major problems for land management and human safety. Clayey landslide activity is complex, showing a succession of periods of inactivity and reactivation phases that can evolve into sudden acceleration and catastrophic landslides and/or flows. Understanding the processes that control this activity therefore requires the continuous monitoring of specific parameters. At the end of June 2016, the Harmalière clayey landslide (located 30 km south of the city of Grenoble in the French Alps) was dramatically reactivated at the headscarp after 35 years of continuous but limited activity. The total volume involved, which moved in the form of tilted blocks of different sizes, was estimated at about 3,106 m3. Several sensors, including seismometers and GNSS stations, were installed immediately behind the main escarpment in early August 2016. They recorded a rupture involving a block of a few hundred cubic meters in November 2016. Additional data (seismology, meteorology, piezometer, etc.) were provided by a permanent observatory located a few hundred meters away in the nearby Avignonet landslide (RESIF2006). Two three-component seismic sensors were placed on the collapsed block and 10 meters aft on the stable part respectively.

Thus, four seismic parameters were monitored for 4 months until the clay block rupture: the cumulative number of microseisms, the resonance frequency of the block, the relative variation in Rayleigh wave velocity (dV/V) and the correlation coefficient (CC) in the range 1-12 Hz. All these parameters showed a significant precursor signal before the rupture, but at very different times. During the monitoring period, they also showed different responses to environmental parameters and in particular to precipitation. The resonance frequency increased slightly but steadily from 8 to 9 Hz (+12%) during the pre-break period, then decreased from 9 Hz to 7 Hz (-22%) just one hour before the break. However, the other three parameters showed significant variations a few weeks before failure. The dV/V and CC parameters reacted 1.5 month before the failure, during a very heavy rain event. The CC showed a general decrease over time, first affecting the high frequencies, then gradually spreading to the low frequencies. Finally, seismic activity is almost constant during the first three months, with only slight temporary increases during precipitation. One month before the rupture, a significant increase in the number of events is observed.

This study shows the potential of monitoring different seismic parameters over time in order to predict the slip of blocks in a clay material.