bluuebunny/crossref_metadata_2025 huggingface dataset:
Validation of process-based sand wave models: applying a linear and nonlinear sand wave model to the Netherlands Continental Shelf
Authors: Campmans Geert , Roos Pieter , Van Dijk Thaiënne , Hulscher Suzanne
Published: March 2020

Tidal sand waves are dynamic large-scale bed forms occurring in tide-dominated, sandy shelf seas such as the North Sea. Since they may interfere with various activities, understanding sand wave dynamics is important from a practical point of view. Recently, two process-based model studies were carried out to investigate the influence of storm processes on sand wave dynamics (Campmans et al., CSR2017; JGR2018). While this type of model gives insight in the morphodynamic mechanisms, quantitative comparison with field observations remains a challenge.

 

Here we present a systematic validation of the afore mentioned linear and nonlinear models, against a wide range of sand wave observations from the entire Netherlands Continental Shelf (Damen et al., JGR2018). Specifically, from the available locations with sand wave observations and environmental characteristics, we have chosen a grid for calibration and, staggered to that, a grid for validation. For the so-called calibration locations, we tuned the linear model (using local environmental conditions) in order to minimize the difference between observed and modelled wavelengths. Next, on the validation locations, we used the thus obtained parameter settings (location-independent values of slip parameter and effective wave period) to test our model performance, both in the linear and nonlinear regime. First results demonstrate fair agreement for the wavelengths from the linear model and indicate a systematic overestimation of sand wave heights by the nonlinear model.

 

References

Campmans, G.H.P., Roos, P.C., De Vriend, H.J., Hulscher, S.J.M.H., 2017.  Modeling the influence of storms on sand wave formation: A linear stability approach. Continental Shelf Research 137, 103–116.

Campmans, G.H.P., Roos, P.C., De Vriend, H.J., Hulscher, S.J.M.H., 2018. The influence of storms on sand wave evolution: a nonlinear idealized modeling approach. Journal of Geophysical Research: Earth Surface 123, 2070-2086.

Damen, J.M., Van Dijk, T.A.G.P., Hulscher, S.J.M.H., 2018. Spatially varying environmental properties controlling observed sand wave morphology. Journal of Geophysical Research: Earth Surface 123, 262-280.
Holocene dyke-induced surface deformation at Krafla (Iceland) revealed by UAV-based high resolution 3D models
Authors: Tibaldi Alessandro , Russo Elena , Fallati Luca
Published: March 2020

We analysed at very high detail the surface deformation along a volcanotectonic structure in the Krafla Fissure Swarm, located in the North Iceland Rift. The structure affects the Pleistocene Hituholar volcano and 12 ka old lava flows. The work has been carried out through the Structure from Motion technique (SfM) applied to UAV surveys, integrated with a lithostratigraphic and structural field survey. The resulting Orthomosaic and Digital Surface Model (DSM) have a resolution of 2.6 and 10 cm, respectively. The zone of deformation is characterised by topographic bulging, parallel extension fractures, and narrow grabens with locally floor uplift, which can be explained as the effect of shallow propagation of a dyke northward from the Krafla magma chamber. In fact, the study area has been interested by northward dyke propagation from the central Krafla volcano during several rifting events, among which the recentmost occurred in 1975-1984 (Krafla fire). The analysis of the very wide area covered by our UAV surveys indicates that changes in the pattern of surface deformation occur in correspondence of contacts between deposits with different rheological properties: the transition from very stiff lavas to soft hyaloclastites produces a change from extension fracturing to normal faulting. Moreover, we detected a series of extension fractures with NE-SW strike and left-lateral slip component, and NNW-SSE strike and right-lateral component, which are rotated clockwise and anticlockwise respect to the main NNE-SSW graben trend, and extend outward to the sides of the main deformation zone up to 17 m. We interpret these structures as originated in front of the dyke tip during its propagation and being successively bypassed by the dyke advancement. In case of an active volcanic zone, the comprehension of the surface deformation and of the significance of strike-slip faulting occurrence can help to determine how and where magma is propagating. Thus, these evidences may help to decipher geophysical data and surface structural data during volcano monitoring.
Fog climatology analyses in coastal fog ecosystem at the Atacama Desert/Chile – spatio-temporal analysis of fog water characteristics and variability
Authors: Pastene Juan Carlos , Siegmund Alexander , del Río Camilo , Osses Pablo
Published: March 2020

The coastal Chilean Atacama Desert comprise some of the driest areas of the world with anual mean precipitation partly less than 1 mm/year, like in the Tarapacá region. It is in these environments, where fog plays a relevant role for local ecosystems, like the so called Tillandsia Lomas. These fog ecosystems contain Tillandsia landbeckii as an endemic species, which covers a vertical range of about 800 to 1,250 m, related to fog availability. The study area “Oyarbide” (20°29’ S, 70°03’ W) is situated inland desert, over a range of 300 m elevation where the advective and orographic fog penetrate far enough to reach the east border of the site at around 1,200 m.

On local level, the understanding of the fog climate characteristics and variability is still poor as well as knowledge about the driving parameters, the temporal dynamics and spatial gradients. For this reason, various parameters of fog climate are analysed and characterised on the basis of a local station network in order to determine the local fog climatology.

From 2016, several high quality climatological stations (Thies Clima) were installed in “Oyarbide”, located in a transect from ca. 1,160 m to ca. 1,350 m in a distance between 10.3 km to 10.7 km from the coast. The local network of climate stations is generating a high temporal and spatial acquisition of climatological data of standard fog water (2 m), air temperature & humidity (2 m), surface temperature (5 cm), wind speed & direction (10 m & 2 m), air pressure, global radiation, leaf wetness and dew every 10 minutes until nowadays. Additionally, ten mini fog collectors (Mini FCs) were installed at the beginning 2019, covering a surface of ca. 3 km2, generating a monthly data of ground fog water collected (50 cm).

First spatio-temporal analyses of different parameters of the local fog climate will be presented. The results of the study show a seasonal, monthly and daily variability, with altitudinal and vertical differences and oscillation. The results will serve as input for the understanding of the fog variability into hyperarid zones.
Paleoenvironment of Kuan Kreng peat swamp, Southern Thailand
Authors: Wangritthikraikul Kannika , Leknettip Smith , Chawchai Sakonvan
Published: March 2020

Peatlands have played an important role in the global carbon cycle. Tropical peatlands are one of the largest reserves of terrestrial organic carbon. Present-day tropical peat swamp forests are, however, under the threat of anthropogenic disturbance or have already been widely degraded. In Southeast Asia, very large areas of peatland have been deforested, drained, converted to extensive and intensive agricultural land uses and exposed to regular wildfires. Khuan Kreng peat swamp is the second largest protected wetland in Thailand. Recent studies in Khuan Kreng peat swamp has focused on present day drought and forest fires, but there is still lack of paleoenvironmental data. In this study, sediment and peat sequences were collected from Forest Fire Control Station area in Khuan Kreng peat swamp, and geochemical data (loss on ignition, grain size analysis and carbonate content) were analyzed. The age of early Holocene were determined based on plant macrofossils using Radiocarbon Dating (14C). The preliminary results indicate that this area was Tidal flats. The study of sediment/peat sequences using geochemical data can improve our understanding how past environmental have affected Khuan Kreng peat swamp ecosystems.
Multiphase rotational extension and marginal flexure along a developing passive margin: the Western Afar Margin, East Africa
Authors: Zwaan Frank , Corti Giacomo , Keir Derek , Sani Federico , Muluneh Ameha , Illsley-Kemp Finnigan , Papini Mauro
Published: March 2020

This multidisciplinary study focuses on the tectonics of the Western Afar Margin (WAM), which is situated between the Ethiopian Plateau and Afar Depression in East Africa. The WAM represents a developing passive margin in a highly volcanic setting, thus offering unique opportunities for the study of rifting and (magma-rich) continental break-up, and our results have both regional and global implications.

Earthquake analysis shows that the margin is still deforming under a ca. E-W extension regime (a result also obtained by analysis on fault measurements from recent field campaigns), whereas Afar itself undergoes a more SW-NE extension. Together with GPS data, we see Afar currently opening in a rotational fashion. This opening is however a relatively recent and local phenomenon, due to the rotation of the Danakil microcontinent modifying the regional stress field (since 11 Ma). Regional tectonics is otherwise dominated by the rotation of Arabia since 25 Ma and should cause SW-NE (oblique) extension along the WAM. This oblique motion is indeed recorded in the large-scale en echelon fault patterns along the margin, which were reactivated in the current E-W extension regime. We thus have good evidence of a multiphase rotational history of the WAM and Afar.

Furthermore, analysis of the margin’s structural architecture reveals large-scale flexure towards Afar, likely representing the developing seaward-dipping reflectors that are typical for magma-rich margins. Detailed fault mapping and earthquake analysis show that recent faulting is dominantly antithetic (dipping away from the rift), bounding remarkable marginal grabens, although a large but older synthetic escarpment fault system is present as well. By means of analogue modelling efforts we find that marginal flexure indeed initially develops a large escarpment, whereas the currently active structures only form after significant flexure. Moreover, these models show that marginal grabens do not develop under oblique extension conditions. Instead, the latter model boundary conditions create the large-scale en echelon fault arrangement typical of the WAM. We derive that the recent structures of the margin could have developed only after a shift to local orthogonal extension. These modeling results support the multiphase extension scenario as described above.

Altogether, our findings are highly relevant for our understanding of the structural evolution of (magma-rich) passive margins. Indeed, seismic sections of such margins show very similar structures to those of the WAM. However, the general lack of marginal grabens, which are so obvious along the WAM, can be explained by the fact that most rift systems undergo or have undergone oblique extension, often in multiple phases during which structures from older phases control subsequent deformation.
Using GIS tools for the Play Fairway Analysis in geothermal exploration
Authors: Morales González Francisco Airam , D'Auria Luca , Rodríguez Fátima , Padrón Eleazar , Pérez Nemesio
Published: March 2020

The Canary Islands archipelago, due to their recent volcanism, are the only Spanish territory with high enthalpy geothermal resources. However, there is no evidence in the islands of endogenous fluids manifestations with the exception of the Teide fumaroles, in Tenerife. Although some efforts have been made to investigate the geothermal resources from the 1970s to the 1990s and later during the past decade, the final goal has not yet been achieved, which is to locate and define the size, shape and structure of the geothermal resource, and determine their characteristics and capacity to produce energy (Rodríguez et al. 2015). For this reason it is extremely important to use new tools that allow a better understanding of the geothermal resource. In this work we describe a probabilistic evaluation of the geothermal potential of the island of Tenerife using Geographical Information Systems (GIS) through a collection of geological, geophysical and geochemical data.

The Play Fairway Analysis (PFA) was used, as illustrated by Lautze et al. (2017) in a similar study for an environment having similar characteristics: the Hawaiian Archipelago.  The PFA approach consists of joining information coming from multidisciplinary datasets within a probabilistic framework. Basically, the probabilities related to the presence of heat (H), fluids (F) and permeability (P) are computed quantitatively from the starting datasets and combined to obtain the probability of presence of geothermal resources and its confidence.

In the present study this probabilistic method have been implemented using GIS geoprocessing tools and raster image analysis using geological (Holocene vents, volcano-tectonic structures), geophysical (seismicity, resistivity data, gravity data) and geochemical (hydrogeochemistry, soil gas emission and geochemistry, etc…).

The main result of this work is a cartographic set that allow showing the areas of Tenerife with the greatest potential for geothermal exploration. Furthermore, using the statistical framework of PFA analysis, we obtained also confidence intervals on the retrieved probability maps.
Substantial genetic yield gap estimated for wheat in Europe
Authors: Semenov Mikhail , Senapati Nimai
Published: March 2020

Improving yield potential and closing the yield gap are important to achieve global food security. Europe is the largest wheat producer, delivering about 35% of wheat globally, but European wheat's yield potential from genetic improvements is as yet unknown. We estimated wheat ‘genetic yield potential’, i.e. the yield of optimal or ideal genotypes in a target environment, across major wheat growing regions in Europe by designing in silico ideotypes. These ideotypes were optimised for current climatic conditions and based on optimal physiology, constrained by available genetic variation in target traits. A ‘genetic yield gap’ in a location was estimated as the difference between the yield potential of the optimal ideotype compared with a current, well-adapted cultivar. A large mean genetic yield potential (11–13 t ha−1) and genetic yield gap (3.5–5.2 t ha−1) were estimated under rainfed conditions in Europe. In other words, despite intensive wheat breeding efforts, current local cultivars were found to be far from their optimum, meaning that a large genetic yield gap still exists in European wheat. Heat and drought tolerance around flowering, optimal canopy structure and phenology, improved root water uptake and reduced leaf senescence under drought were identified as key traits for improvement. Closing this unexploited genetic yield gap in Europe through crop improvements and genetic adaptations could contribute towards global food security.
ECOPOTENTIAL Storylines: a whole system approach to Protected Area ecosystems
Authors: Provenzale Antonello , Beierkuhnlein Carl , Giamberini Silvia , Imperio Simona , Marangi Carmela , Viterbi Ramona
Published: March 2020

The EU H2020 ECOPOTENTIAL project was devoted to make best use of Earth observations to improve ecosystem benefits and support conservation strategies. The project followed a whole-ecosystem approach, with special attention to geosphere-biosphere interactions. The project, started in 2015 and ended in 2019, focused its activities on a set of more than 20 protected areas of international relevance in Europe and beyond, many of which are also eLTER and ILTER sites, covering a wide array of biogeographic regions and ecosystems (www.ecopotential-project.eu). The site/sites – specific research activities have been developed within a comprehensive framework (called the project’s “Storylines”) where real-life issues of broad conservation relevance for Protected Areas are linked with research questions. The Storylines specify the needs for remote sensing and in-situ data for ecosystem modelling, ecosystem service assessment, cross-scale interaction estimates, demands for future protections, policy and capacity building. Each storyline has been focused within at least one protected area and has sets the basis for further operational work in the field, adding specifics, defining a work plan and assigning tasks. Storylines have been conceived as iterative processes whose flow of activity and practical implementation evolved with the increase of knowledge and the demands by the users of the scientific findings. After a general introduction to the Storyline approach, here we focus on the case of the Gran Paradiso National Park, considering population dynamics of wild ungulates, biodiversity assessments and Critical Zone exploration. The Storyline concept is now left as a legacy of the ECOPOTENTIAL project to eLTER RI and to the GEO ECO community activities.
Dispersionless and Weakly Dispersed Injections in the Dayside Magnetosphere with Evidence of Mirror Wave Signatures
Authors: Cooper Matthew , Gerrard Andrew , Lanzerotti Louis , Perry Gareth , Soto-Chavez Rualdo
Published: March 2020

We present observational evidence of mirror waves in the dayside inner magnetosphere as measured with instrumentation on the dual NASA Van Allen Probes spacecraft.  While mirror waves near the dayside bow shock have been reported from several spacecraft missions (e.g. Cluster, THEMIS, MMS), their presence in the dayside inner magnetosphere has not been reported.  We speculate that the mirror modes are associated with direct dayside injections under negative Bz conditions, and drift to lower L-shells.  The analyzed event coincides with the main phase of a CME shock-induced space weather storm, with high solar wind speeds in excess of 700 km/s and a sudden drop in Dst occurring approximately eight hours prior to the event.  The highest plasma beta values were measured by spacecraft B at 12:24 at magnetic noon at L ~ 4.5-5.5.  Spacecraft A later measured a similar feature at 13:00 local magnetic time.  The potential presence of such mirror waves would indicate dayside sources of anisotropy inside the magnetopause, or the penetration of bow shock particles into the dayside inner L-shells.  To our knowledge, this is the first time such waves have been reported in the inner magnetosphere.
Source area and emplacement conditions of Riscos Bayos Ignimbrites, Caviahue-Copahue Volcanic Complex (Argentina)
Authors: Haag Maurício , Moncinhatto Thiago , Sommer Carlos , Savian Jairo , Caselli Alberto , Trindade Ricardo , Hartmann Gelvam , Poletti Wilbor
Published: March 2020

The Caviahue-Copahue Volcanic Complex (CCVC, Argentina) composes one of the most active volcanic centers in the Southern Volcanic Zone (SVZ) of the Andes, characterized by the presence of voluminous explosive and effusive deposits. Despite its young age (< 5 Ma), CVCC deposits were strongly affected by two glaciations, leading to the removal of a considerable volume of the original deposits, requiring alternative techniques for the reconstruction of this volcanic center. The Riscos Bayos Ignimbrites (RBI) consist of a sequence of non-welded ignimbrites, located approximately 15 km southeast of the CVCC. This unit is commonly associated with the putative collapse of Caviahue caldera (15 x 20 km, 1 km deep) during the Pleistocene, although the source area and emplacement conditions of RBI still poorly constrained. In this work, we combine fieldwork, anisotropy of magnetic susceptibility (AMS, 23 sites) and rheological analyses (17 samples) in order to trace RBI source region and constrain its emplacement conditions, addressing its relevance to CVCC evolution. Rheological parameters, including viscosity, glass transition temperature, and liquidus temperatures were obtained using numerical models available from the literature, while AMS samples were measured using a Kappabridge MFK1-A (Agico) and the data processed using Anisoft5 (Agico). The magnetic mineralogy was characterized using several experiments, including isothermal remanet magnetization, thermomagnetic curves, hysteresis loops, first-order reversal curves and scanning electron microscopy. Our data indicate liquidus temperatures ranging from 969 to 1100 ºC, glass transition temperatures from 653 to 721 ºC, and viscosity (at liquidus temperature) from 3.4 to 7.3 log Pa.s. The absence of welding features in the samples implies RBI emplacement at temperatures below the glass transition temperature, suggesting a fast and effective cooling of the pyroclasts before their settling. The low crystal content of the samples suggests eruption temperatures close to the calculated liquidus temperature of the melt.  AMS directional analyses indicate a consistent transport sense to SSE (Az of approximately 100º), implying the southern rim of the CVCC as the main source region of RBI. Magnetic experiments show primary, multi-domain, high curie temperature (580 ºC) titanomagnetites as the main carriers of the AMS signal. Most ellipsoids display oblate to triaxial geometry, with a low degree of anisotropy (< 5%) and magnetic susceptibility (1.0 x 10-2 SI). The low welding degree of RBI units and its geographic distribution outside the Caviahue depression contributes to the Caviahue caldera hypothesis in the region, suggesting its emplacement as an ‘extra-caldera’ pyroclastic unit.
Energy and air pollution benefits of household fuel policies in northern China
Authors: Meng Wenjun , Zhong Qirui , Chen Yilin , Shen Huizhong , Tao Shu
Published: March 2020

In addition to many recent actions taken to reduce emissions from energy production, industry, and transportation, a new campaign substituting residential solid fuels with electricity or natural gas has been launched in Beijing, Tianjin, and other 26 municipalities in northern China, aiming at solving severe ambient air pollution in the region. Quantitative analysis shows that the campaign can accelerate residential energy transition significantly, and if the planned target can be achieved, more than 60% of households are projected to remove solid fuels by 2021, compared with less than 20% without the campaign. Emissions of major air pollutants will be reduced substantially. With 60% substitution realized, emission of primary PM2.5 and contribution to ambient PM2.5 concentration in 2021 are projected to be 30% and 41% of those without the campaign. With 60% substitution, average indoor PM2.5 concentrations in living rooms in winter are projected to be reduced from 209 (190-230) μg/m3 to 125 (99-150) μg/m3. The population-weighted PM2.5 concentrations can be reduced from 140 μg/m3 in 2014 to 78 μg/m3 or 61 μg/m3 in 2021 given that 60% or 100% substitution can be accomplished. Although the original focus of the campaign was to address ambient air quality, exposure reduction comes more from improved indoor air quality because approximately 90% of daily exposure of the population is attributable to indoor air pollution. Women benefit more than men.
Indoor and outdoor ambient air temperatures during summer 2019 in Augsburg, Germany
Authors: Beck Christoph , Fritsch Marisa , Linder Marco , Völkel Johanna , Beckmann Sabrina , Hiete Michael , Martin Klaus , Repper Andreas , Schneider Michael
Published: March 2020

The summer of 2019 featured significantly too warm conditions in Germany during all summer months. This included several distinct warm episodes and heat waves, the most pronounced of these appearing around end of July.

Within the framework of the interdisciplinary research project Abc (Augsburg bleibt cool – Augsburg stays cool) – funded by the German Federal Ministry for Environment, Nature Conservation and Nuclear Safety – it is intended to detect and quantify urban thermal hot-spots with respect to outdoor and as well indoor air temperatures in the city of Augsburg (Bavaria, SE Germany). The knowledge of such spatiotemporal patterns of thermal and especially heat-stress exposure are an indispensable basis for any further aspired local climate modeling and adaptation studies.

To this end, in June 2019 around 500 low-cost thermometers and around 50 thermo-hygrometers have been distributed among residents of the central city parts of Augsburg to record ambient indoor temperatures during summer. As high indoor air temperatures are suspected to be health relevant in particular during night, participants placed the thermometers in their bedrooms.

Outdoor temperature and humidity have been recorded simultaneously by an already existing comprehensive urban climate measuring network.

In this contribution we present main features of the data set of indoor temperatures and show and discuss first analyses concerning temporal and spatial variability of indoor air temperatures during summer 2019. This includes a comparison of indoor and outdoor temperatures, analyses of the influence of urban structures (e.g. in terms of local climate zones) and as well the influence of building characteristics (e.g. age, building material, ...) on indoor air temperatures.
When minerals fight back: The relationship between back stress and geometrically necessary dislocation density
Authors: Thom Christopher , Goldsby David , Kumamoto Kathryn , Hansen Lars
Published: March 2020

The dynamics of several geophysical phenomena, such as post-seismic deformation and post-glacial isostatic readjustment, are inferred to be controlled by the transient rheology of olivine in Earth’s mantle. However, the physical mechanism(s) that underlie(s) this behavior remain(s) relatively unknown, and most experimental studies focus on quantifying steady-state rheology. Recent studies have suggested that back stresses caused by long-range elastic interactions among dislocations could play a role in transient deformation of olivine. Wallis et al. (2017) identified an internal back stress in olivine single crystals deforming at 1573 K, which gave rise to anelastic transient deformation in stress dip experiments. Hansen et al. (2019) quantified the room-temperature strain hardening of olivine deforming by low-temperature plasticity and measured a back stress that gave rise to a Bauschinger effect, a well-known phenomenon in materials science wherein the yield stress is reduced upon reversing the sense of direction of the deformation.

To explore deformation at very high dislocation density, we have developed a novel nanoindentation load drop method to measure the back stress in a material at sub-micron length scales. Using a self-similar Berkovich tip, we measure back stresses in single crystals of olivine, quartz, and plagioclase feldspar at a range of indentation depths from 100–1700 nm, corresponding to geometrically necessary dislocation (GND) densities of order 1014–1015 m-2. Our results reveal a power-law relationship between back stress and GND density with an exponent ranging from 0.44-0.55 for each material, with an average across all materials of 0.48. Normalizing back stress by the shear modulus measured during the indentation test results in a master curve with a power-law exponent of 0.44, in close agreement with the theoretical prediction (0.5) derived from the classical Taylor hardening equation (Taylor, 1934). For olivine, the extrapolation of our fit quantitatively agrees with other published data spanning over 5 orders of magnitude in GND density and temperatures ranging from 298-1573 K. This work provides the first experimental evidence in support of Taylor hardening in a geologic material, supports the assertion that strain hardening is an athermal process that can occur during high-temperature creep, and suggests that back stresses from long-range interactions among dislocations must be considered in rheological models of transient creep.
Impacts of water partitioning and polarity of organic compounds on secondary organic aerosol over Eastern China
Authors: Li Jingyi , Ying Qi , Hu Jianlin
Published: March 2020

Secondary organic aerosol (SOA) is an important component of fine particular matter (PM2.5) in China. Most air quality models use an equilibrium partitioning method along with estimated saturation vapor pressure of semi-volatile organic compounds (SVOCs) to predict SOA formation. However, this method ignores partitioning of water vapor to the organic aerosols and the organic phase non-ideality, both of which affect the partitioning of SVOCs. In this study, the Community Multi-scale Air Quality model (CMAQv5.0.1) was used to investigate the above impacts on SOA formation during winter (January) and summer (July) of 2013 over eastern China. The organic aerosol module was updated by incorporating water partitioning into the organic particulate matter (OPM) and considering non-ideality of organic-water mixture. The modified model can generally capture the observed organic carbon (OC), the total organic aerosol (OA) and diurnal variation of PM2.5 at ground sites. SOA concentration shows significant seasonal and spatial variations, with high concentration levels in North China Plain (NCP), Central China and Sichuan basin (SCB) areas during winter (up to 25 μg m-3) and in Yangtze River Delta (YRD) during summer (up to 12 μg m-3). When water partitioning is included in winter, SOA concentrations increase slightly, with the monthly-averaged daily maximum relative difference of 10-20% at the surface and 10-30% for the whole column, mostly due to the increase in anthropogenic SOA. The increase in SOA is more significant in summer, by 20-90% at the surface and 30-70% for the whole column. The increase of SOA over the land is mostly due to biogenic SOA while the increase of SOA over the coastal regions is related with that of anthropogenic origin. Further analysis of two representative cities, Jinan and Nanjing, shows that changes of SOA are favored under hot and humid conditions. The increases in SOA cause a 12% elevation in the aerosol optical depth (AOD) and 15% enhancement in the cooling effects of aerosol radiative forcing (ARF) over YRD in summer. The aerosol liquid water content associated with OPM (ALWorg) at the surface is relatively high over the land in winter and over the ocean in summer, with the monthly-averaged daily maximum of 2-9 and 5-12 μg m-3, respectively. By using the -Köhler theory, we calculated the hygroscopicity of OA with modeled ALWorg, finding that the correlation with O:C ratio varies significantly across different cities and seasons. Water partitioning into OPM only promotes SOA formation, while non-ideality of organic-water mixture only leads to decreases in SOA in most regions of eastern China. Water partitioning into OPM should be considered in air quality models in simulating SOA, especially in hot and humid environments.
Learning missing part of physics-based models within a variational data assimilation scheme
Authors: Filoche Arthur , Brajard Julien , Charantonis Anastase , Béréziat Dominique
Published: March 2020

The analogy between data assimilation and machine learning has already been shown and is still being investigated to address the problem of improving physics-based models. Even though both techniques learn from data, machine learning focuses on inferring model parameters while data assimilation concentrates on hidden system state estimation with the help of a dynamical model. 
 
Also, neural networks and more precisely ResNet-like architectures can be seen as dynamical systems and numerical schemes, respectively. They are now considered state of the art in a vast amount of tasks involving spatio-temporal forecasting. But to train such networks, one needs dense and representative data which is rarely the case in earth sciences. At the same time, data assimilation offers a proper Bayesian framework allowing to learn from partial, noisy and indirect observations. Thus, each of this field can profit from the other by providing either a learnable class of dynamical models or dense data sets.

In this work, we benefit from powerful and flexible tools provided by the deep learning community based on automatic differentiation that are clearly suitable for variational data assimilation, avoiding explicit adjoint modelling. We use a hybrid model divided into 2 terms. The first term is a numerical scheme that comes from the discretisation of physics-based equations, the second is a convolutional neural network that represents the unresolved part of the dynamics. From the Data Assimilation point of view, our network can be seen as a particular parametrisation of the model error. We then jointly learn this parameterisation and estimate hidden system states within a variational data assimilation scheme. Indirectly, the issue of incorporating physical knowledge into machine learning models is also addressed. 

We show that the hybrid model improves forecast skill compared to traditional data assimilation techniques. The generalisation of the method on different models and data will also be discussed.
Alkalinity and CO2 fluxes in a tropical seagrass meadow
Authors: Van Dam Bryce , Fourqurean James , Smyth Ashley
Published: March 2020

Total alkalinity (TA) production in vegetated coastal systems is considered a putative sink for atmospheric CO2, due to the increase in the seawater buffer capacity when TA is produced in excess of DIC. Much of the TA generated in these habitats is derived from the reduction of NO3 and Fe, but in oligotrophic tropical waters dominated by carbonate sediments, these sources of TA may be minimal. To address this uncertainty, we measured a suite of sediment-water fluxes (SO4, N2, TA, DIC, DOC, etc) in a tropical and calcifying seagrass meadow, allowing us to identify the biogeochemical processes responsible for TA generation and consumption. We placed this information into the context of water-air CO2 exchange, which was measured by atmospheric eddy covariance. Net N2 fluxes indicated that denitrification was a negligible TA source in this oligotrophic seagrass meadow, which at times was net N2-fixing. Instead, sediment-water TA fluxes were dominated by the balance between SO2 reduction, H2S oxidation, and carbonate dissolution/precipitation. Air-water CO2 exchange was small and variable, reflecting the highly-buffered seawater chemistry and oligotrophic nature of this seagrass meadow.
Using Convolutional Neural Networks for the prediction of groundwater levels
Authors: Nölscher Maximilian , Häntze Hartmut , Broda Stefan , Jäger Lena , Prasse Paul , Makowski Silvia
Published: March 2020

The temporal prediction of groundwater levels plays an important role in groundwater management, such as the estimation of anthropogenic impacts as well as consequences of climatic changes. Therefore, the modeling of groundwater levels using physics-based approaches is an integral part of hydrogeology. However, data-driven approaches have only recently been used, in particular for the prediction of groundwater levels using machine learning techniques (e.g., Random Forest and Neural Networks). For this purpose, one model per observation well or time series is always set up. In order to further develop this, an approach is presented which uses a single model for the prediction of groundwater levels at several observation wells (n > 200). The model is a three-dimensional Convolutional Neural Net (CNN).
In addition to the time series of groundwater levels meteorological data on precipitation (P) and temperature (T) serves as additional input channels. The CNN "sees" not only the P- or T-value of the grid cell in which the observation well lies, but also surrounding values. This has the advantage that even influences of meteorological patterns in the spatial vicinity of the observation well on the groundwater level can be learned. The forecasts are calculated for periods up to six months. In addition to the comparison with the measured values, a comparison of the error averaged over all observation wells compared to a baseline model is used for the validation. To further improve predictability, the hyperparameters are optimized and other area data (e.g., geology, soil properties, land use) used as input. This model should form the basis for a regionalized forecast of groundwater levels.
Distribution characteristics of gullies with slope gradient in Northeast China
Authors: Fan Hao Ming , Wang Di Chen
Published: March 2020

Twenty selected watersheds were divided into five small watershed sets according to location in Liaoning Province (LN), China. Watersheds and slopes were extracted from a 1:50,000 DEM, and gully data for each watershed were obtained by remote sensing interpretation. The gullies and associated slopes within the small watersheds were identified, and the distributions of gully density, proportion of dissected land, and gully length-width ratio in each small LN watershed and in the five small watershed sets were obtained. The correlations between the small watershed sets and the gully distributions throughout LN demonstrate regional distribution differences, and the watershed area has a great influence on both the area and length of gullies. Regional differences are present in the gully density and the proportion of dissected land in the small watersheds. The distribution of gullies with respect to slope depends on both the gully parameters and the proportion of terrain in the different slope grade ranges. The distribution results for the five small watershed sets are similar to those from a census of the Liaoning-Around Bohai mountainous and hilly sub-region. The gully density and proportion of dissected land in LN showed a single-peak curve with respect to slope, with slope thresholds of 8° and 5°, respectively. The constructed distribution equation has a high degree of fit. The comprehensive distributions of gully density, proportion of dissected land, and length-width ratio with slope indicate that gully erosion in LN is serious within the slope range of 3~8°.
Basal melting over Subglacial Lake Ellsworth and its catchment: insights from englacial layering
Authors: Ross Neil , Siegert Martin
Published: March 2020

Deep-water ‘stable’ subglacial lakes likely contain microbial life adapted in isolation to extreme environmental conditions. How water is supplied into a subglacial lake, and how water outflows, is important for understanding these conditions. Isochronal radio-echo layers have been used to infer where melting occurs above Lake Vostok and Lake Concordia in East Antarctica but have not been used more widely. We examine englacial layers above and around Lake Ellsworth, West Antarctica, to establish where the ice sheet is ‘drawn down’ towards the bed and, thus, experiences melting. Layer drawdown is focused over and around the NW parts of the lake as ice, flowing obliquely to the lake axis, becomes afloat. Drawdown can be explained by a combination of basal melting and the Weertman effect, at the transition from grounded to floating ice. We evaluate the importance of these processes on englacial layering over Lake Ellsworth and discuss implications for water circulation and sediment deposition. We report evidence of a second subglacial lake near the head of the hydrological catchment and present a new high-resolution bed DEM and hydropotential model of the lake outlet zone. These observations provide insight into the connectivity between Lake Ellsworth and the wider subglacial hydrological system.
Non-steady strain in the terrane boundary shear zone of the Ambaji Granulite, NW India: Implications for understanding towards the dynamics of emplacement of the lower-middle crustal rocks.
Authors: Saraswati Ragini , Biswal Tapas Kumar
Published: March 2020

Shear zones in the high-grade terranes represent the tectonic- fossils of strain history. One such shear zones, namely Balaram-Jogdadi shear zones defining the terrane boundary of the Ambaji granulites of the South Delhi terrane Aravalli –Delhi Mobile belt, NW India, provide evidence for strain variation during exhumation of lower-middle crustal rocks. Compilation of field and microscopic analysis of various samples of mylonite from shear zones suggest that the part of shear zone contains high-grade mineral assemblages such as cordierite, sillimanite, spinel, garnet in quartzo-feldspathic mylonite rock and exhibit signature of thrusting in which garnet behaved as brittle phase and quartz and feldspar grain show ductile deformation. 2D and 3D strain analysis estimate a plane to flattening type of strain pattern. Principal strain planes are used to calculate the strain ratios for estimation of variation of strain along the shear zone. This study indicates high-grade mylonite accommodates high strain. The flow of rigid porphyroclasts estimates mean kinematic vorticity number varies from 0.47 to 0.68, which indicates the dominance of pure shear during shearing. Vorticity by the Rs/θ method in quartz grain estimates ranges from 0.7 to 0.95, suggesting a non-steady strain towards the end of deformation. High-grade mylonites were overprinted by low-temperature mylonitisation marked by minerals like quartz, feldspar, biotite in which feldspar porphyroclast shows brittle deformation and quartz, biotite show ductile deformation. Several shear kinematics indicate top-to-NW sinistral strike-slip shearing. Thus it has been interpreted that the shear zone had undergone non-steady strain. The initial thrusting phase was dominated by more pure shear component. The strike-slip shearing part was dominated by more simple shear component. Monazite geochronology sets the age of shearing at 834-778 Ma suggesting the exhumation was a transition event between Grenville to Pan-African orogeny.

Keywords: Shear zone, Deformation, Vorticity, 3D strain analysis, Monazite dating
Investigating hydromechanical and geochemical processes in swelling clay-sulfate rocks - presentation of a new experimental setup
Authors: Röder Katja , Butscher Christoph
Published: March 2020

Due to human interventions such as the construction of tunnels and bridges as well as in geothermal projects, natural groundwater flow paths are disturbed. Within regions of clay-sulfate rock deposits like Southern Germany and Switzerland („Gipskeuper“) as well as Spain („Red Clay“), the mentioned structural interventions may promote the swelling of such rocks. Consequently, damage to buildings and other infrastructure in their vicinity can be triggered.

Until today, the planning of countermeasures that would minimize or prevent the mentioned swelling is difficult, because it is hardly possible to predict the swelling behavior of clay-sulfate rocks connected with geotechnical constructions. One reason is the limited knowledge of geochemical, hydraulic and geomechanical processes taking place during rock swelling.

The swelling process in clay-sulfate rocks is mainly due to the transformation of anhydrite into gypsum, which leads to an increase in rock volume of up to 60 %. The chemical transformation process includes anhydrite dissolution, possibly transport of dissolved sulfate with groundwater flow, and subsequent gypsum precipitation; and has large impact on flow paths within the swelling rock.

To extend the knowledge of hydromechanical and geochemical processes during the swelling of clay-sulfate rocks, a swelling test facility was installed at the chair of Engineering Geology and Environmental Geotechnics (TU Bergakademie Freiberg, Geotechnical Institute). The basis are six independently controllable apparatuses to conduct swelling experiments under oedometric conditions. First experiments with natural rock samples from a tunnel in Southern Germany are currently carried out.

Because groundwater circulation strongly influences swelling processes in clay-sulfate rocks, and vice versa, we developed a modified setup for swelling experiments. To observe and quantify hydraulic, mechanical and chemical processes during rock swelling in the lab, we combine the swelling apparatuses with a flow-through cell (permeameter). The modified setup allows the realization of an active and controlled fluid flow through the rock sample during swelling. As a result, reactive flow processes such as changes in permeability due to swelling can be observed under variable stress and strain conditions. Our contribution presents the experimental setup of the swelling tests with and without fluid flow. Furthermore, first results from the current experimental runs are presented.
Influence of incoming plate relief on overriding plate deformation and earthquake nucleation: Cocos Ridge subduction (Costa Rica)
Authors: Martínez-Loriente Sara , Sallarès Valentí , R. Ranero César , B. Ruh Jonas , Barckhausen Udo , Grevemeyer Ingo , Nangs Nathan
Published: March 2020

We present a 2D p-wave velocity (Vp) model and a coincident multichannel seismic reflection profile mapping the structure of the southern Costa Rica margin and incoming Cocos Ridge. The seismic profiles image the ocean and overriding plates from the trench across the entire offshore margin, including the structures involved in the 2002 Mw6.4 Osa earthquake. The overriding plate consists of three domains: Domain I at the margin front displays thin-skinned deformation of an imbricated-thrust system composed of fractured rocks with relatively low Vp. Domain II under the middle continental shelf is comparatively less fractured, showing ~15 km long landward-dipping reflection packages and discrete active deformation of the shelf sediment and seafloor. Domain III in the inner shelf is little fractured and appears to be dominated by elastic deformation, with inactive structures of an extensional basin consisting of tilted blocks overlain by ~2 km-thick gently landward-dipping strata. The velocity structure supports the argument that the bulk of the margin is highly consolidated rock possibly similar to outcrops in the Osa Peninsula. Thick-skinned tectonics probably causes the uplift of Domains II and III. The incoming oceanic plate shows crustal thickness variations from ~14 km at the trench (Cocos Ridge) to 6-7 km beneath the continental shelf. We combine (1) inter-plate geometry and velocity-derived fracturing degree at the base of the overriding plate, (2) tectonic stresses and brittle strain above the inter-plate boundary extracted from 3D numerical models, and (3) earthquake locations, to investigate potential relationships between structure and earthquake generation. The 2002 Osa earthquake and its aftershocks appear to have nucleated at the leading flank of two subducting seamounts, coinciding with the area of highest tectonic overpressure in numerical models. Both estimated rock fracturing and modelled brittle strain, steadily increase from the leading flank of the subducting seamounts to their top, which we interpret to reflect the progressive damage caused by the incoming plate relief. Therefore, the analysis supports a spatial and temporal relationship between subducting seamount location, upper plate fracturing, brittle strain, tectonic overpressure, and earthquake nucleation.