bluuebunny/crossref_metadata_2025 huggingface dataset:
A toolbox for convenient calculation of anisotropy of magnetic remanence
Authors: Chadima Martin , Jezek Josef
Published: March 2021

The growing interest in ferromagnetic fabric, i.e. magnetic fabric carried solely by ferromagnetic (sensu lato) grains, creates the need for a simple way to obtain anisotropy of magnetic remanence (AMR) tensors from a set of laboratory imparted, spatially distributed vectors of remanent magnetization (RM). Here, we present a simple, user-friendly toolbox embedded into Anisoft software which facilitates AMR tensor fitting from an array of RM vectors acquired according the prescribed data acquisition protocol (6, 9, 12, 15, 18 magnetizing directions). As these protocols are usually quite laborious involving a series of demagnetizations and directional magnetizations, this toolbox provides a graphical visualization of the measured RM vectors in terms of their directional comparison with the respective magnetizing directions and their intensity in comparison with the intensity of demagnetized state (background magnetization). This visualization provides a convenient way to check whether there are no evident missteps and the measured vectors correspond to the acquisition protocol. Prior to tensor fitting, the correction for the background magnetization is optionally done by a direct subtraction of the measured background or by mutual subtraction of antipodally magnetized RM vectors, if available. The AMR tensors are fitted by the least-square algorithm using two slightly different approaches involving either (1) all three orthogonal components of magnetized RM vectors (Vector Method) or (2) their projections to the respective magnetizing directions (Projection Method). The differences between these two approaches are discussed. The calculated AMR tensors, including their confidence limits, are stored in the same file format as AMS data and can be thus instantly visualized and further processed using Anisoft software.
Contrasting dynamics of short and long blocks in the Northern Hemisphere
Authors: Drouard Marie , Woollings Tim , Sexton David , McSweeney Carol
Published: March 2021

In this study, we aim at identifying dynamical differences between short blocks, which last only five days, and long blocks, which last at least ten days, to better characterise long blocks. We show that long blocks often involve cyclonic Rossby wave breaking, while short blocks are equally associated with cyclonic and anticyclonic wave breaking. This main result is reproduced in several coupled climate models. We propose three mechanisms that might explain the lower number of long anticyclonic blocks: 1/ a downstream reinforcement of the anticyclone during anticyclonic blocks might be associated with a stronger downstream advection of the block; 2/ the mean zonal wind is reinforced by synoptic eddies towards a more northward position during anticyclonic blocks, whereas synoptic eddies force the mean zonal wind to the south of the block during cyclonic blocks, which has been previously shown to be associated with more persistent weather patterns; 3/ strong and/or sustained eddy feedback is needed to maintain long anticyclonic blocks. All these parameters combined might explain why blocks last longer and why anticyclonic blocks are less present at extreme durations.
Influence of Southern Ocean dynamics on Antarctic temperatures and on the global carbon cycle over the past two millennia.
Authors: Goosse Hugues , Lyu Zhiqiang , Menviel Laurie , Meissner Katrin , Mouchet Anne
Published: March 2021

Reconstructions of Antarctic surface temperature covering the past millennia display a large centennial variability that is not synchronous with fluctuations recorded on other continents and which is generally not well simulated by models. Many processes can be at the origin of these temperature variations such as teleconnections with tropical oceans and changes in the Southern Ocean. The focus here will be on the latter, in particular on the influence of westerly winds that have a large impact on the exchange of heat and carbon between the ocean and atmosphere. Changes in the Southern Ocean circulation and stratification also influence the carbon cycle at global scale. It is generally suggested that atmospheric CO2 variations over the past two millennia were mainly controlled by land processes but the Southern Ocean might have also played a role. We will thus test whether the joint analysis of Antarctic temperature and atmospheric CO2 concentration fluctuations can inform us on the origin of the observed changes over this period. In this purpose, we use the climate model LOVECLIM which includes a representation of the global carbon cycle. Experiments over the last two millennia will address the sensitivity to realistic perturbations of the wind stress. Finally, experiments with data assimilation will allow assessing what constraints are needed for model results to better reproduce the atmospheric CO2 concentration and reconstructed temperature history.
Risk evaluation of radionuclides contamination on soil and groundwater under different scenarios simulating by HYDRUS-1D
Authors: Wenxiang Liu , Hanqing Yu , Yang Lu
Published: March 2021

A large number of radionuclides, produced by nuclear accidents or nuclear waste, may cause radioactive contamination in the agricultural and aquatic ecosystems. Under these circumstances, it is necessary to optimize the remediation of agricultural areas polluted by radionuclides using innovative monitoring and prediction techniques. To mitigate radioactive contamination in farmland soil and effectively protect groundwater, some measures should be taken against on field investigation, laboratory experiment and model prediction. In this study, the HYDRUS-1D model was used to simulate the vertical migration of 137Cs and 60Co in farmland soil in northern China calibrating by the soil lysimeter experiment, and the scenario simulations of 137Cs and 60Co migration were conducted under different radioactive levels. Results showed that the order of sensitivity in saturated water content (θs), residual water content(θr), saturated hydraulic conductivity(Ks) and distribution coefficient (Kd) applied in HYDRUS 1D model was Kd > θs > θr >Ks. The simulated concentrations ​​of 137Cs and 60Co in Brown soil and Aeolian sandy soil on day 175 and 355 were significantly positively correlated with the measured values​​ (r>0.90, p<0.01). The verification results showed that the predictive values on the 577th day were also significant positive correlated with the measured values ​​(r>0.90, p<0.01). The RMSE, CRM and NRMSE calculating by simulated and measured values ​​of 137Cs and 60Co in soil were very small, indicating that HYDRUS 1D can be used to simulate the migration of radionuclides in farmland soil. Scenarios simulation results revealed that radionuclides were concentrated in the surface layer within 5 cm, but the migration depth has exceed 10 cm soil depth, and even reaches up to 23.5 cm depth at high concentration level. The surface soil should be cleaned timely to protect groundwater with high level from radioactive contamination and further study should be done about horizontal transport and numerical simulation.
Decarbonising UK transport: Implications for electricity generation, land use and policy
Authors: Logan Kathryn G. , Nelson John D. , Chapman James D. , Milne Jenny , Hastings Astley
Published: March 2021

Transitioning away from internal combustion engine private vehicles in favour of public transport, including electric and hydrogen alternatives, is recognised as an essential part of the solution to reduce the scale of climate change and meet net zero in the UK by 2050. This decarbonisation transition to low carbon transport will likely result in an increase in energy demand which will have impacts on both ecosystem services (ES) and natural capital (NC). Robust projections of societal energy demands post low carbon transition are therefore required to ensure adequate power generation is installed. In this study, we project the energy demand for electric and hydrogen cars, buses and trains between 2020 and 2050 based on the number of vehicles and distance travelled using the Transport Energy Air Pollution UK (TEAM-UK) model outputs. In this work, the spatial requirements of additional renewable energy (onshore/offshore wind and solar), nuclear and fossil fuels, on ES and NC was predicted by considering the expected electricity generation mix expected by 2050, the number of generation installations and energy density of each energy source. The outcomes of this analysis can assist policymakers in better understanding what energy types and transport networks need to be prioritised to efficiently meet net zero. Legislation requires increased low carbon electricity generation, though the impact on ES and NC are not currently quantified.

Energy demand was lower for electric transport (136,599 GWh) than hydrogen transport (425,532 GWh) for all vehicle types in 2050, however a combination of both power types will be needed to accommodate the full range of socioeconomic requirements. In addition, to power electrical transport, 1,515 km2 of land will be required for solar, 1,672 km2 for wind and 5 km2 for expansion of the average nuclear power station by 2050. This will be approximately doubled for hydrogen provision due to the additional energy and conversions required to generate hydrogen.

In reality the finer scale mix between hydrogen and electric transport types in the future will depend on geographical location and resource availability. Rural areas may favour hydrogen power due to range restrictions, with electric transport more readily suited to urban areas with greater installed infrastructure. To reduce the requirements for additional electricity and maximise carbon output decreases, minimising the impact on NC and ES, policymakers need to focus on encouraging a modal shift towards low carbon public transport from private vehicles and to ensure a more sustainable route to decarbonising transport.
Observed Transport Variability of the Atlantic Subtropical Cells and Their Connection to Tropical Sea Surface Temperature Variability
Authors: Tuchen Franz Philip , Lübbecke Joke F. , Brandt Peter , Fu Yao
Published: March 2021

The shallow meridional overturning cells of the Atlantic Ocean, the subtropical cells (STCs), consist of poleward Ekman transport at the surface, subduction in the subtropics, equatorward flow at thermocline level and upwelling along the equator and at the eastern boundary. In this study, we provide the first observational estimate of transport variability associated with the horizontal branches of the Atlantic STCs in both hemispheres based on Argo float data and supplemented by reanalysis products.

Thermocline layer transport convergence and surface layer transport divergence between 10°N and 10°S are dominated by seasonal variability. Meridional thermocline layer transport anomalies at the western boundary and in the interior basin are anti-correlated and partially compensate each other at all resolved time scales. It is suggested that the seesaw-like relation is forced by the large-scale off-equatorial wind stress changes through low-baroclinic-mode Rossby wave adjustment. We further show that anomalies of the thermocline layer interior transport convergence modulate sea surface temperature (SST) variability in the upwelling regions along the equator and at the eastern boundary at time scales longer than 5 years. Phases of weaker (stronger) interior transport are associated with phases of higher (lower) equatorial SST. At these time scales, STC transport variability is forced by off-equatorial wind stress changes, especially by those in the southern hemisphere. At shorter time scales, equatorial SST anomalies are, instead, mainly forced by local changes of zonal wind stress.
Dissipation in the Bay of Bengal from a Seaglider
Authors: Damerell Gillian , Sheehan Peter , Hall Rob , Matthews Adrian , Heywood Karen
Published: March 2021

In July 2016, a Seaglider equipped with a microstructure sensor system was deployed in the southern Bay of Bengal at 7° 54.0′ N, 89° 4.5′ E.  162 profiles (of which 146 were to 1000 m) of microstructure shear and temperature were collected as a time series at the same location.  Dissipation is calculated independently from both shear and temperature.  The time-average profile shows high dissipation (nearly 1×10-5 W kg-1) near the surface, dropping rapidly over the uppermost 50 m to ~1×10-7 W kg-1, followed by a more gradual decrease to ~5×10-10 W kg-1 at 300m.  A band of slightly higher dissipation around 500 m (~8×10-10 W kg-1) could facilitate an increased vertical flux of nutrients, heat, salinity, etc at these depths.  From 600 to 1000 m dissipation remains roughly constant at ~1×10-10 W kg-1.  Variability of the near surface dissipation in response to atmospheric forcing is also discussed.
Pathogen persistence in fine particle standing stocks in an intermittent urban stream
Authors: Drummond Jen , Gonçalves José , Aquino Tomás , Bernal Susana , Gacia Esperança , Gutierrez-Aguirre Ion , Turk Valentina , Ravnikar Maja , Krause Stefan , Martí Eugènia
Published: March 2021

Rivers transport pathogenic microorganisms (including fecal indicator bacteria and human enteric viruses) from point and non-point sources over long distances, posing a direct risk for human health. Yet, pathogens in surface waters can be deposited and transitorily immobilized and accumulated together with other fine particles in streambed sediments, mostly within the top few centimeters. These dynamic fine particle standing stocks retain and delay downstream transmission of pathogens during baseflow conditions, but contribute to their resuspension and transport downstream during stormflow events. Direct measurements of pathogen accumulation in streambed sediments are rare. Further, it is unknown whether pathogen accumulation is constrained near to the point source inputs or if the continuous deposition and resuspension of pathogens results in the transmission of active pathogens further downstream. 

In this study, we analyze fine particle standing stocks along a 1 km reach of an intermittent Mediterranean stream receiving inputs from the effluent of a wastewater treatment plant (WWTP), during a summer drought when the effluent constituted 100% of the stream flow, and thus, large accumulation and persistence of pathogens along the streambed was expected. We measured abundance of total bacteria, Escherichia coli (as a fecal indicator bacteria), and presence of enteric rotavirus (RoV) and norovirus (NoV). We also monitored environmental variables such as water temperature, dissolved oxygen, total benthic particulate matter, and fraction of organic matter.  Abundance of E. coli, based on qPCR detection, was high  (~ 1 ng/μL) along the first 100 m downstream of the WWTP effluent input, and we found trace amounts of RoV and NoV.  Furthermore, E. coli was present along the first km downstream of the WWTP effluent input with a logarithmic decline in concentration with distance. These results were combined with a particle tracking model that uses stream water velocity as an input and accounts for hyporheic exchange, pathogen immobilization, degradation and resuspension during baseflow and stormflow conditions.  Model results indicate that even at very low flows (<20 L/s), pathogens can be transported over long distances (> 1km), but that the extent of longitudinal transport varies among pathogen types.  These results demonstrate that benthic standing stocks of fine particles act as hot spots of pathogen accumulation in streams, and that the interplay between immobilization, degradation, the extent of resuspension and downstream transport during storms and time between storms determine pathogen concentrations in the streambed. 

 
Ground motion detection in a salt solution mining area, an application of Multi-Temporal Satellite Interferometry
Authors: Solari Lorenzo , Montalti Roberto , Barra Anna , Monserrat Oriol , Bianchini Silvia , Crosetto Michele
Published: March 2021

Subsurface mining is one of the human activities with the highest impact in terms of induced ground motion. The excavation of the mining layers creates a geotechnically and hydrogeologically unstable context. The generation of chimney collapses and sinkholes is the most evident surface consequence of underground mining which, in general, creates the optimal conditions for the development of subsidence bowls. Considering this, the need for ground motion monitoring tools is evident. Topographic measurements have been the obvious choice for many years. Nowadays, the flourishing of Multi-Temporal Satellite Interferometry (MTInSAR) algorithms and techniques offers a new way to measure ground motion in mining areas. MTInSAR fully covers the accuracy requirements asked by mining companies and authorities, adding new potentialities in term of area coverage and number of measurement points. The technique has some intrinsic limitations in mining areas, e.g. coherence loss, but the algorithms are being pushed to their technical limits in order to provide the best coverage and quality of measures.

This work presents a detailed scale MTInSAR approach designed to characterize ground deformation in the salt solution mining area of Saline di Volterra (Tuscany Region, central Italy). In summary, salt solution mining consists in the injection at the depth of interest of a dissolving fluid and in the extraction of the resultant saturated brine. In Saline di Volterra, this mining activity created ground motion, sinkholes and groundwater depletion. The MTInSAR processing approach used is based on the direct integration of interferograms derived from Sentinel-1 images and on the phase splitting between low and high frequency components. Phase unwrapping is separately performed for the two components that are then recombined to avoid error accumulation. Before generating the final deformation map, a classical atmospheric phase filtering is applied to remove the residual low frequency signal. The results obtained reveal the presence of several subsidence bowls, sometimes corresponding to sinkholes formed in the recent past. These moving areas register velocities up to -250 mm/yr with different spatial and temporal patterns according to the distribution and age of formation of sinkholes. This is the first time an interferometric analysis is performed here. It is hoped that such information could increase the awareness of local entities on the ground effects induced by this mining activity.
Late Holocene climate record from Sırtlanini Cave (central west Anatolia) stalagmite: implications from U-series dating, mineralogy and isotope data 
Authors: Ünal İmer Ezgi , Yılmaz İsmail Ömer , Baykara Mehmet Oruç , Zhao Jian-Xin
Published: March 2021

Turkey lies along the transition zone between northerly and southerly climate regimes such that it provides opportunity for a good understanding of Holocene climate that impacted ancient Eastern Mediterranean civilizations. Within the scope of the EU-funded SPELEOTOLIA project, 7 caves from western and southwestern Anatolia were visited and several stalagmite samples were collected. Detailed mineralogical and geochemical analyses performed on samples from one of the target caves, the Sırtlanini Cave (Karacasu, Aydın), helps to reconstruct the regional Holocene climate and gives insights on living conditions of Anatolian civilizations, mainly including Roman and Ottoman Empires.   

The 450 m-long Sırtlanini Cave (max. depth of ~40 m; ~1060 m a.s.l.) developed within the Mesozoic marbles of the Menderes Massif. We focus on the first set of U-series age, stable and radiogenic isotope (C, O, and Sr) and mineralogical data performed on the stalagmite (SRT-5) from this cave. The drip water isotope data (δ18OVSMOW = -7.8‰, δDVSMOW = -41.6‰) indicated depletions in O and H isotopes compared to other cave waters in the region. The U-series age results of SRT-5 show that the 423 mm-long stalagmite was deposited fast (0.25 mm/y) between 0.111±0.034 kyr and 1.825±0.421 kyr (BP) spanning the Roman, Byzantine and Ottoman periods. SRT-5 seems to have grown intermittently with at least two possible hiatuses (at around 291 and 401 years BP) based on mineralogical studies. It is mainly composed of fine- to medium-grained columnar calcite, with occasional dendritic fabric and visible annual layering, particularly at the older bottom section of the stalagmite. Stable isotope profiles (δ13C: -10.5 to -8‰ VPDB, δ18O: -7 to -5.5‰ VPDB) constructed using 423 sub-sample analyses along the stalagmite demonstrate significant hydroclimatic variability through the Little Ice Age and Medieval Warm Period between 195 and 1909 CE. This variation correlates well with previously documented drought and related famine and migration events in western Anatolia primarily in the 19th century. Further investigations (e.g., high-resolution LA-ICPMS trace element analyses) will be performed specifically to constrain the anthropogenic sources and distinguish these from recent Aegean or possible global (e.g., southeast Asian) volcanogenic signals. 

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No: 842403.
Representation of the Scandinavia-Greenland Pattern and its Relationship with the Polar Vortex in S2S Models
Authors: Lee Simon , Charlton-Perez Andrew , Furtado Jason , Woolnough Steven
Published: March 2021

The strength of the stratospheric polar vortex is a key contributor to subseasonal prediction during boreal winter. Anomalously weak polar vortex events can be induced by enhanced vertically propagating Rossby waves from the troposphere, driven by blocking and wave breaking. Here, we analyse a tropospheric pattern—the Scandinavia–Greenland (S–G) pattern—associated with both processes. The S–G pattern is defined as the second empirical orthogonal function (EOF) of mean sea‐level pressure in the northeast Atlantic. The first EOF is a zonal pattern resembling the North Atlantic Oscillation. We show that the S–G pattern is associated with a transient amplification of planetary wavenumber 2 and meridional eddy heat flux, followed by the onset of a persistently weakened polar vortex. We then analyse 10 different models from the S2S database, finding that, while all models represent the structure of the S–G pattern well, some models have a zonal bias with more than the observed variability in their first EOF, and accordingly less in their second EOF. This bias is largest in the models with the lowest resolution, and consistent with biases in blocking and Rossby wave breaking in these models. Skill in predicting the S–G pattern is not high beyond week 2 in any model, in contrast to the zonal pattern. We find that the relationship between the S–G pattern, enhanced eddy heat flux in the stratosphere, and a weakened polar vortex is initially well represented, but decays significantly with lead time in most S2S models. Our results motivate improved representation of the S–G pattern and its stratospheric response at longer lead times for improved subseasonal prediction of the stratospheric polar vortex.
The effects of solar flare-driven ionospheric electron density change on Doppler Flash
Authors: Chakraborty Shibaji , Qian Liying , Ruohoniemi J. Michael , Baker Joseph , McInerney Joseph
Published: March 2021

Trans–ionospheric high frequency (HF) signals experience a strong attenuation following a solar flare, commonly referred to as Short–Wave Fadeout (SWF). Although solar flare-driven HF absorption is a well-known impact of SWF, the occurrence of a frequency shift on radio wave signal traversing the lower ionosphere in the early stages of SWF, also known as "Doppler Flash", is newly reported and not well understood. Some prior investigations have suggested two possible sources that might contribute to the manifestation of Doppler Flash: first,  enhancements of plasma density in the D and lower E regions; second, the lowering of the reflection point in the F region. Observations and modeling evidence regarding the manifestation and evolution of Doppler Flash in the ionosphere are limited. This study seeks to advance our understanding of the initial impacts of solar flare-driven SWF. We use WACCM-X to estimate flare-driven enhanced ionization in D, E, and F-regions and a ray-tracing code (Pharlap) to simulate a 1-hop HF communication through the modified ionosphere. Once the ray traveling path has been identified, the model estimates the Doppler frequency shift along the ray path. Finally, the outputs are validated against observations of SWF made with SuperDARN HF radars. We find that changes in the refractive index due to the F-region's plasma density enhancement is the primary cause of Doppler Flash.
Lagrangian tracing and analysis of the South Asian summer monsoon precipitation
Authors: Dey Dipanjan , Döös Kristofer
Published: March 2021

The water-mass sources and their variability responsible for the South Asian summer monsoon precipitation were investigated using Lagrangian atmospheric water-mass trajectories. The results indicated that water-masses from the Central and South Indian Ocean are the dominant contributors to the total South Asian summer monsoon rainfall, followed by the contribution from the local recycling, the Arabian Sea, remote sources and the Bay of Bengal. It was also found that although the direct contribution originating from the Bay of Bengal is small, it still provides a route for the water-masses that come from other regions. The outcomes further revealed that the water-masses originating from the Central and South Indian Ocean are responsible for the net precipitation over the coastal regions of the Ganges-Brahmaputra-Meghna Delta, Northeast India, Myanmar, the foothills of the Himalayas and Central-East India. Water-masses from the Arabian sea are mainly contributing to the rainfall over the Western coast and West-Central India. Summer monsoon precipitation due to the local recycling is primarily restricted to the Indo-Gangetic plain. No recycled precipitation was observed over the mountain chain along the West coast of India (Western Ghats). The inter-annual variability of the South Asian summer monsoon precipitation was found to be mainly controlled by the water-masses from the Central and South Indian Ocean.
Characteristics of Sunquake Events Observed in Solar Cycle 24
Authors: Kosovichev Alexander , Sharykin Ivan
Published: March 2021

Helioseismic response to solar flares ("sunquakes") occurs due to localized force or/and momentum impacts observed during the flare impulsive phase in the lower atmosphere. Such impacts may be caused by precipitation of high-energy particles, downward shocks, or magnetic Lorentz force. Understanding the mechanism of sunquakes is a key problem of the flare energy release and transport. Our statistical analysis of M-X class flares observed by the Solar Dynamics Observatory during Solar Cycle 24 has shown that contrary to expectations, many relatively weak M-class flares produced strong sunquakes, while for some powerful X-class flares, helioseismic waves were not observed or were weak. The analysis also revealed that there were active regions characterized by the most efficient generation of sunquakes during the solar cycle. We found that the sunquake power correlates with maximal values of the X-ray flux derivative better than with the X-ray class. The sunquake data challenge the current theories of solar flares.
On the role of the Antarctic Slope Front on the occurrence of theWeddell Sea polynya under climate change
Authors: Lockwood Joseph , Dufour Carolina , Griffies Stephen , Winton Michael
Published: March 2021

This study investigates the occurrence of the Weddell Sea Polynya under an idealized

climate change scenario by evaluating simulations from climate models of different

ocean resolutions. The GFDL-CM2.6 climate model, with roughly 3.8 km

horizontal ocean grid spacing in the high latitudes, forms a Weddell Sea Polynya at

similar time and duration under idealized climate change forcing as under pre-industrial

forcing. In contrast, all convective models forming the fifth phase of the Coupled Model

Intercomparison Project (CMIP5) show either a cessation or a slowdown of Weddell

Sea Polynya events under climate warming. The representation of the Antarctic Slope

Current and related Antarctic Slope Front is found to be key in explaining the

differences between the two categories of models, with these features being more

realistic in CM2.6 than in CMIP5. In CM2.6, the freshwater input driven by sea ice melt

and enhanced runoff found under climate warming largely remains on the shelf region

since the slope front restricts the lateral spread of the freshwater. In contrast, for most

CMIP5 models, open ocean stratification is enhanced by freshening since the absence

of a slope front allows coastal freshwater anomalies to spread into the open ocean.

This enhanced freshening contributes to the slow down the occurrence of Weddell Sea

Polynyas. Hence, an improved representation of Weddell Sea shelf processes in

current climate models is desirable to increase our ability to predict the fate of the

Weddell Sea Polynyas under climate change.
Volcano dynamics vs tectonics on Mars: evidence from Pavonis Mons
Authors: Pozzobon Riccardo , Orlandi Diana , Pagli Carolina , Mazzarini Francesco
Published: March 2021

Volcanic activity is widespread within the inner Solar system and it can be commonly observed on rocky planets.
In this work, we analyse the structures of Pavonis Mons, which is one of the three large volcanoes in the Tharsis volcanic province of Mars, by performing structural mapping, azimuth, and topographic distribution of linear features on the flanks of Pavonis, such as grabens and pit chains. We tested whether their formation is to be ascribed to the internal volcano dynamics and magmatic activity or the tectonics related to the Tharsis volcanic province activity.
Through the length size distribution and fractal clustering analyses of the structural features, we found that large grabens are vertically confined in the upper mechanical layers of the brittle crust whereas pit chains penetrate the whole crust up to the magmatic source, indicating that they can be considered the main feeders of Pavonis Mons. We inverted the topography with dykes and faults models to test whether grabens at the surface are the expression of intrusions at depth and we suggest that thin dykes inducing normal faulting is the most likely mechanism. Furthermore, two azimuthal distribution of the grabens are identified: concentric grabens occur on the volcano summit while linear grabens at its base show NE-SW trend as the Tharsis Montes volcanoes alignment. The analyses show that faults related to large grabens are confined in a mechanical layering in the upper layers of the brittle crust, whereas deeper structures such as pit chains are most likely associated to magma injection/dykes and therefore, connected to the subcrustal magma source at a depth of ~80–100 km.
Therefore, based on our results, we infer that Pavonis Mons recorded active rifting at the initial stages of development with the formation of the large linear graben and faults at its base followed by a phase of volcano growth and concentric magma intrusions when volcano and magma chamber dynamics prevailed
Detection and tracking of atmospheric blocks: a Lagrangian flow network approach
Authors: Ehstand Noémie , Donner Reik , López Cristóbal , Hernández-García Emilio
Published: March 2021

In the past decades, boreal summers have been characterized by a number extreme weather events such as heat waves, droughts and heavy rainfall periods with significant social, economic and environmental impacts. One of the most outstanding examples occurred in the summer of 2010 when an anomalously strong heatwave persisted over Eastern Europe for several weeks while extreme rainfalls struck Pakistan, leading to the country’s worst floods in record history. Both events were related to the presence of an anomalously persistent atmospheric blocking situation - that is a large-scale, nearly stationary, atmospheric pressure pattern - over Eastern Europe.

The high impact of blocking events has motivated numerous studies. However, there is not yet a comprehensive theory explaining their onset, maintenance and decay and their prediction remains a challenge.

In this work, we employ a Lagrangian dynamics based, complex network description of the atmospheric transport to study the connectivity patterns associated with atmospheric blocking events. The network is constructed by associating nodes to regions of the atmosphere and establishing links based on the flux of material between these nodes during a given time interval, as described in Ser-Giacomi et al. [1]. One can then use the tools and metrics developed in the context of graph theory to explore the atmospheric flow properties. In particular, we demonstrate the ability of measures such as the network degree, entropy and harmonic closeness centrality to trace the spatio-temporal characteristics of atmospheric blocking events.

[1] E. Ser-Giacomi, V. Rossi, C. López, E. Hernández-García, Chaos 25(3), 036404 (2015)

 

This research was conducted as part of the CAFE Innovative Training Network (Climate Advanced Forecasting of sub-seasonal Extremes, http://www.cafes2se-itn.eu/) which has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 813844.
Observational evidence of solar activity interaction with chlorine chemistry curbing Antarctic ozone loss
Authors: Seppälä Annika , Gordon Emily , Funke Bernd , Tamminen Johanna , Walker Kaley
Published: March 2021

We present the impact of the so-called energetic particle precipitation (EPP), part of natural solar forcing on the atmosphere, on polar stratospheric NOx, ozone, and chlorine chemistry in the Antarctic springtime, using multi-satellite observations covering the overall period of 2005–2017. We find consistent ozone increases when high solar activity occurs during years with easterly phase of the quasi biennial oscillation. These ozone enhancements are also present in total O3 column observations. We find consistent decreases in springtime active chlorine following winters of elevated solar activity. Further analysis shows that this is accompanied by increase of chemically inactive chlorine reservoir species, explaining the observed ozone increase. This provides the first observational evidence supporting the previously proposed mechanism relating to EPP modulating chlorine driven ozone loss. Our findings suggest that solar activity via EPP has played an important role in modulating Antarctic ozone depletion in the last 15 years. As chlorine loading in the polar stratosphere continues to decrease in the future, this buffering mechanism will become less effective and catalytic ozone destruction by EPP produced NOx will likely become a major contributor to Antarctic ozone loss.
Damage coalescence controls slow and fast faulting: Insights from dynamic X-ray microtomography experiments
Authors: Renard Francois , McBeck Jessica , Cordonnier Benoît
Published: March 2021

During fast and slow earthquakes deformation localizes along narrow and quasi-planar fault surfaces. However, processes controlling the localization process develop not only on the fault surface but also in the volume surrounding the fault zone. How these processes transition from a dispersed to more localized distribution of damage remains controversial. Moreover, to what degree the localization process controls the speed of coseismic slip is an open question. We perform a series of 4D X-ray microtomography experiments on crystalline rocks (granite, marble), with and without a pre-existing slip surface, and image the development of damage while each sample is loaded until system-size brittle failure. We image and deform the samples under in situ stress conditions of a few kilometers depth using the Hades deformation apparatus installed on the tomography beamline ID19 at the European Radiation Synchrotron Facility. By imaging all the microfractures that develop in the samples, we characterize their individual geometry and the geometry of the entire microfracture network. The results show that, when a pre-existing slip surface exists in the sample, slow earthquakes can generate damage in the volume around the fault, leading to catastrophic faulting. When no pre-existing fault is present, microfractures accumulate and can lead to two end-member types of earthquakes. One type is a catastrophic failure of the sample that occurs when the microfractures link into a macroscopic fault, producing a fast earthquake. Alternatively, the microfractures can grow without significant fracture coalescence, leading to the slow development of a fault network with a transient increase of macroscopic deformation rate that resembles that of a slow earthquake. We conclude that damage coalescence influences the slow and fast behaviours of earthquake slip.
A tracking algorithm to identify slab and weak layer combinations for assessing snow instability and avalanche problem type
Authors: Reuter Benjamin , Viallon-Galinier Léo , Mayer Stephanie , Hagenmuller Pascal , Morin Samuel
Published: March 2021

Snow cover models have mostly been developed to support avalanche forecasting. Recently developed snow instability metrics can help interpreting modeled snow cover data. However, presently snow cover models cannot forecast the relevant avalanche problem types – an essential element to describe avalanche danger. We present an approach to detect, track and assess weak layers in snow cover model output data to eventually assess the related avalanche problem type. We demonstrate the applicability of this approach with both, SNOWPACK and CROCUS snow cover model output for one winter season at Weissfluhjoch. We introduced a classification scheme for four commonly used avalanche problem types including new snow, wind slabs, persistent weak layers and wet snow, so different avalanche situations during a winter season can be classified based on weak layer type and meteorological conditions. According to the modeled avalanche problem types and snow instability metrics both models produced weaknesses in the modeled stratigraphy during similar periods. For instance, in late December 2014 the models picked up a non-persistent as well as a persistent weak layer that were both observed in the field and caused widespread instability in the area. Times when avalanches released naturally were recorded with two seismic avalanche detection systems, and coincided reasonably well with periods of low modeled stability. Moreover, the presented approach provides the avalanche problem types that relate to the observed natural instability which makes the interpretation of modeled snow instability metrics easier. As the presented approach is process-based, it is applicable to any model in any snow avalanche climate. It could be used to anticipate changes in avalanche problem type due to changing climate. Moreover, the presented approach is suited to support the interpretation of snow stratigraphy data for operational forecasting.
“Application of Hydrological Simulation models to solve pollution impacts in the water management decision-making processes. Measures for the recovery of Mar Menor sea lake and “Campo de Cartagena” aquifer (Spain)”
Authors: Gómez Martínez Gabriel , Pérez-Martín Miguel Ángel , Estrela Segrelles Clara Eugenia
Published: March 2021

The use of fertilizers and pesticides in agriculture activity is a worldwide extended practice since decades for improving crops performance, which can cause, however, with excessive dosage rates, aquifers’ pollution and water quality problems, like the study case hereby presented of Mar Menor sea-lake waterbody and “Campo de Cartagena” aquifer, in the southern coast of Spain.

Due the agricultural practices, the Campo de Cartagena aquifer presents in this moment high values of nitrate, around 150 mgNO3 / l, appearing also these high values of nitrogen in soil in this area. This situation produces a great contribution of nitrogen to the Mar Menor lake, by two mainly processes, firstly, continuously through groundwater returns to the waterbody’s surface and secondly, through the precipitation events when a large amount of nitrogen is washed from soil by the rainfall. Finally, the large amount of nitrogen incomes to the Mar Menor sea lake contributes to deteriorate the status of this waterbody and also promotes the eutrophication processes that have been taking place during last years.

A large watershed scale nitrates’ transport simulation model, Patrical Model (Perez-Martín et al., 2016), is used to estimate the measures to recovery the “Campo de Cartagena” aquifer. The model establishes, mathematically, the relationship between nitrogen application, nitrogen surplus (excess), and nitrate concentration in groundwater and surface waterbodies.

Model results show that it is necessary to reduce around 80% of the current nitrogen surplus in the “Campo de Cartagena” aquifer to recovery the good status in the aquifer. This reduction of nitrogen surplus can be obtained by reducing the fertilizers dosage and consequently the nitrates contribution, with a maximum dose of nitrogen applied by farmers of 170 kgN /ha. Applying this measure could reduce significantly the nitrogen retained in soil in 1-2 years, so the nitrogen contribution during rainfall events also could be reduced significantly. Nitrogen levels in groundwater will gradually decrease in the following years, reaching values around 50 mgNO3 / l in 7-9 years after the application of these measures.
EarthNet2021: Self-supervised impact predictions of extreme weather.
Authors: Requena Mesa Christian , Benson Vitus , Denzler Joachim , Runge Jakob , Reichstein Markus
Published: March 2021

Climate changes globally, yet its impacts strongly vary between different locations in the same region. Today, numerical weather models are able to forecast weather patterns on a scale of several kilometers. However, the extreme weather impacts materialize at a finer scale, interacting with highly local factors such as topography, soil or vegetation type. The relationship between driving variables and Earth’s surface at such local scales remains unresolved by current physical models and is partly unknown; hence, it is a source of considerable uncertainty. Most current efforts to predict the local impacts of extreme weather rely on weather downscaling as an intermediary step. However, weather impacts at high resolution are observed and analyzed on satellite imagery. Thus, we can bypass the weather downscaling step by directly forecasting satellite imagery. This is inherently similar to video prediction, a computer vision task that has been tackled with machine learning models. Here we introduce EarthNet2021, a machine learning challenge to forecast the spatio-temporal evolution of the Earth’s terrestrial surface. The task can be summarized as translating coarse weather projections into high-resolution Earth surface imagery encompassing localized climate impacts. EarthNet2021 is a carefully prepared dataset containing target spatio-temporal Sentinel-2 imagery at 20 m resolution, matching with high resolution topography and mesoscale (1.28 km) weather variables. Comparing multiple Earth surface forecasts is not trivial. Thus, we design the EarthNetScore, a novel ranking criterion for Earth surface models. EarthNet2021 comes with multiple test tracks for evaluation of model validity and robustness as well as model applicability to extreme events and the complete annual vegetation cycle. In addition to forecasting directly observable weather impacts through satellite-derived vegetation indices, capable Earth surface models will enable downstream applications such as crop yield prediction, forest health assessments, coastline management or biodiversity monitoring.
Rise and fall of the Acadian altiplano: Evidence for a Paleozoic orogenic plateau in the northern Appalachian Orogen
Authors: Hillenbrand Ian , Williams Michael , Li Cong , Gao Haiying , Jercinovic Michael
Published: March 2021

High elevation orogenic plateaus are formed by a complex interplay of deep and surficial processes yet understanding of the deeper processes is limited by few recognized exposures of the lower levels of plateaus. We present evidence for the existence of an orogenic plateau during and after the Devonian Acadian orogeny (sensu lato), the mid-crustal roots of which are exposed in the New England Appalachians. The four-dimensional crustal evolution of this paleo-plateau is constrained by the integration of petrochronology, petrologic and geochronologic databases, and geophysical imaging. Doubly thickened crust, widespread amphibolite to granulite-facies metamorphic conditions, a paleo-isobaric surface, and protracted mid-crustal anatexis all indicate the presence of a high elevation (~5 km), low relief plateau by 380 Ma. 40Ar/39Ar thermochronology shows a distinct signature with very slow cooling rates of 2-4°C/m.y. following peak metamorphic conditions. Thermochronologic data, trace element and Nd isotope geochemistry, and monazite and xenotime petrochronology suggest a 50 m.y. lifespan of the plateau (380-330 Ma). Orogen parallel ductile flow and extrusion of gneiss domes resulted in plateau collapse, crustal thinning, and block-like exhumation at ca. 330-300 Ma. Thinning of the plateau crust may have led to the sharp 12-15 km step in Moho depth in western New England, possibly by reactivating the suture between Laurentia and accreted Gondwanan-derived terranes. The formation of the Acadian altiplano may have influenced Li-pegmatite genesis and Paleozoic paleoclimate, while its recognition may provide a window into the deeper processes of orogenic plateaus including partial melting, plutonism, and collapse by ductile extension.