bluuebunny/crossref_metadata_2025 huggingface dataset:
Particle energisation and transport at collisionless shocks propagating through turbulent media.
Authors: Trotta Domenico , Valentini Francesco , Burgess David , Servidio Sergio
Published: March 2021

Shocks and turbulence are spectacular, ubiquitous phenomena and are crucial ingredients to understand the production and transport of energetic particles in several astrophysical systems. The interaction between an oblique, supercritical shock and fully developed plasma turbulence is here investigated by means of kinetic simulations, for different turbulence amplitudes. The role of pre-existing, upstream turbulence on plasma transport is addressed using a novel technique, relying on the coarse-graining of the Vlasov equation. We find that the upstream transport properties strongly depend on upstream turbulence strength, with patterns modulated by the presence of turbulent structures. These results are relevant for a variety of systems, ranging from the Earth's bow shock interacting with solar wind turbulence, to the largest scales of radio relics in galaxy clusters.
Can GNSS-R help us to monitor the effects of inverse barometer in coastal areas ?
Authors: Gravalon Théo , Seoane Lucia , Darrozes José , Ramillien Guillaume
Published: March 2021

The GNSS Reflectometry is an innovative technique, largely developed in the last years, to monitor local sea level heights. The agreement between sea level measurements derived from SNR-based GNSS-R and tide gauges observations have demonstrated the performance of this approach. In the presented study, we are interested in a subtidal scale phenomenon, the Local Inverse Barometer effect (LIB) which consists in the response of the sea surface to atmospheric pressure changes. The LIB is, in fact, not well modelled in coastal regions where GNSS-R provide continuous observations. The sea level anomaly obtained as the difference between GNSS-R sea level measurements and a tide model, T_TIDE developed by Rich Pawlowicz, is analyzed in order to detect the local inverse barometer effect. For this purpose, we have used 1-year of GNSS data of two antennas of the existing national network, Port-Tudy (Groix island, France) and Lyttelton (eastern coast of the South Island, New-Zealand), where the LIB effect is expected to be significant due to their location outside the equatorial band.

On the whole time series, a trend between the sea level anomaly and the LIB effect can be observed at mid to low frequencies (lower than 0.5 cycle per day). Moreover, high barometric variations caused by the passage of strong depressions lead to good correlations (> 0.7) between these two parameters.

Our results suggest that the GNSS reflectometry allows the observation of subtidal scale phenomena such as the impact of atmospherical variations in complex coastal environments.
Middle Holocene environmental reconstruction and climatic inferences through multi-proxy records from Seymareh lake sediments (Zagros Mts., Iran)
Authors: Delchiaro Michele , Iacobucci Giulia , Troiani Francesco , Della Seta Marta , Ballato Paolo , Aldega Luca
Published: March 2021

The Seymareh landslide is the largest rock slope failure (44 Gm3) ever recorded on the exposed Earth surface. It detached ∼10 ka BP from the northeastern flank of the Kabir-Kuh anticline (Zagros Mts., Iran) originating the natural dam responsible for the formation of a three-lake system (Seymareh, Jaidar, and Balmak lakes, with an area of 259, 46, and 5 km2, respectively). The lake system persisted for ∼3000 yr during the Holocene before its emptying phase due to overflow. A sedimentation rate of 21 mm yr−1 was estimated for the Seymareh lacustrine deposits, which increased during the early stage of lake emptying because of enhanced sediment yield from the lake tributaries. 

To reconstruct the climatic and environmental impact on the lake infilling, we reviewed the geomorphology of the basins and combined the results with multi-proxy records from a 30 m thick lacustrine sequence in Seymareh Lake. Major analyses comprise grain size analysis, carbon and oxygen stable isotopes of carbonate-bearing sediments, and X-ray diffraction analysis of clay minerals.

Lake overflowing is largely accepted as the main response to variations in water discharge and sediment supply since the alternation from dry to wet phases enhances sediment mobilization along hillslopes decreasing the accommodation space in the downstream sedimentary basins. In this regard, during the early-middle Holocene, the Seymareh area, as well as the entire Middle East, was affected by short-term climate changes at the millennial-scale, as testified by both paleoecological and archaeological evidence. Indeed, several records from Iranian lakes (i.e., Mirabad, Zeribar, Urmia) well documented the temperature and the moisture conditions of the western Zagros Mountains during the Holocene. During the early Holocene, the precipitation remained low up to 6 ka BP, reaching the driest condition around 8-8.2 ka BP. The impact of this abrupt climate change is evident across West Asia, where the first large villages with domesticated cereals and sheeps disappeared, converting to small hamlets and starting habitat-tracking. As regards the Seymareh area, a more irregular distribution of rainfalls and their increasing seasonality may support rhexistasy conditions, during which the scarce vegetation cover enhances both the hillslope erosion and sedimentation rate in the basins, most likely contributing to the overflow of Seymareh Lake. 
New constraints on Quaternary slip partitioning near the eastern termination of the Altyn Tagh Fault 
Authors: Wieler Nimrod , Mushkin Amit , Shelef Eitan , Zhang Huiping , Sagy Amir , Porat Naomi , Ren Zhikun , Huang Feipeng , Liu Jinrui
Published: March 2021

Slip partitioning along the northern boundary of the Tibetan Plateau is essential for understanding regional deformation and the seismic potential of the different faults that accommodate it. Within this framework the Altyn Tagh Fault (ATF) is commonly viewed as the primary structure that separates the Tibetan Plateau from the stable Gobi-Alashan block to the north. Late Quaternary sinistral slip rates of 8-12 mm/yr across the central ATF between 86° and 93°E decrease eastwards to zero as the fault approaches its mid-continental termination at ~97°E. To better understand how late Quaternary slip is partitioned along the ATF’s eastern termination we obtained new slip-rate measurements  for the ~200-km-long left-lateral ENE striking Sanweishan Fault (SSF) located ~60 km north of the ATF between 94°-96°E near the town of Dunhuang.

Multiple sinistral offsets ranging up to 600 m were identified by linking the clast assemblage of offset alluvial fan remnants with their provenance upstream of the fault.  Luminescence dating revealed depositional ages ranging from 100 - 200 ka for the offset features and time-invariant minimum sinistral slip of 2.5±1 mm/yr during the last ~200 ka, which is approximately an order of magnitude higher than previously reported slip-rates for the SSF. Our results indicate that the SSF and the eastern segment of the ATF accommodate comparable magnitudes of late Quaternary slip. Considering this substantial transfer of lateral slip as far as 60 km north of the eastern ATF we propose that the SSF may represent juvenile northeastward expansion of the Tibetan Plateau into previously stable parts of the Gobi-Alashan block.
Application of Machine Learning for the operational Cloud Product of the Copernicus Satellite Sensors Sentinel-4 (S4) and TROPOMI / Sentinel-5 Precursor (S5P)
Authors: Romahn Fabian , Molina Garcia Victor , Argyrouli Athina , Lutz Ronny , Loyola Diego
Published: March 2021

The increasing amount of Earth observation data provided by the Copernicus Satellite Sensors, the already operational Sentinel-5 Precursor (S5P) and the upcoming Sentinel-4 (S4), that has to be processed within strict near real time (NRT) requirements demands the use of new approaches to cope with this challenge.

In order to solve the inverse problems that arise in atmospheric remote sensing, usually complex radiative transfer models (RTMs) are used. These are very accurate, however also computationally very expensive and therefore often not feasible in combination with the time requirements of operational products. With the recent significant breakthroughs in machine learning, easier application through better software and more powerful hardware, the methods of this field have become very interesting as a way to improve the classical remote sensing algorithms.

In this presentation we show a general approach in order to replace the RTM of an inversion algorithm with an artificial neural network (ANN) with sufficient accuracy while at the same time increasing the performance by several orders of magnitude. The several steps, sampling and scaling of the training data, the selection of the ANN architecture and the training itself, is explained in detail. This is then demonstrated at the example of the ROCINN (Retrieval of cloud information using neural networks) algorithm for the operational cloud product of S5P. It is then shown how this approach can also be easily applied to the upcoming S4 mission and how the current algorithm for S5P can be improved by replacing or adding new physical models (e.g. for ice-clouds) in the form of ANNs.

The procedure has been continuously developed and evaluated over time and the most important results, in terms of sampling, architecture selection, activation functions and training parameters, are presented.

Finally, the huge performance benefits of using an ANN instead of the original RTM also allow for improvements in the inversion algorithm. Several ideas regarding this, e.g. global optimization techniques, are also shown.
The Frontiers of Deep Learning for Earth System Modelling 
Authors: Hall David
Published: March 2021

This talk gives an overview of cutting-edge artificial intelligence applications and techniques for the earth-system sciences. We survey the most important recent contributions in areas including extreme weather, physics emulation, nowcasting, medium-range forecasting, uncertainty quantification, bias-correction, generative adversarial networks, data in-painting, network-HPC coupling, physics-informed neural nets, and geoengineering, amongst others. Then, we describe recent AI breakthroughs that have the potential to be of greatest benefit to the geosciences. We also discuss major open challenges in AI for science and their potential solutions. This talk is a living document, in that it is updated frequently, in order to accurately relect this rapidly changing field.
Lower plate extension of a retreating subduction zone: case study of the Sicily Channel Rift Zone
Authors: Le Breton Eline , Carlini Mirko , Neumeister Robert , Ecke Jessica , Chizzini Nicolo , Torelli Luigi , Artoni Andrea
Published: March 2021

The Alpine-Mediterranean belt is remarkable because of the strong arcuation of its subduction front and the abundance of extensional basins developed within an overall compressional setting. Both resulted from rapid slab rollback and trench retreat especially in Neogene time, accompanied by upper-plate extension and the opening of the Western Mediterranean basins. The Strait of Sicily is a very interesting geological area in the Western-Central Mediterranean, as it has undergone tectonic extension and opening of a rift zone (Sicily Channel Rift Zone, SCRZ) on the lower plate (Africa) of the subduction zone, marked by the Gela Front and the Calabrian Accretionary Wedge, located south and south-east of Sicily, respectively. Furthermore, the SCRZ is important for understanding and quantifying the independent motion and counter-clockwise rotation of the Adriatic plate in Neogene time (Le Breton et al. 2017). However, the exact timing, tectonic style and amount of deformation along the SCRZ remain unclear.

To tackle these questions, we re-evaluate multichannel seismic reflection profiles across the SCRZ (CROP seismic lines M24 and M25), as well as a series of seismic lines correlated with boreholes data from the VIDEPI project (www.videpi.com). Main stratigraphic horizons and tectonic structures are mapped in a 3D database using the MOVE Software (provided by Petex). Preliminary results indicate ~30 km of NE-SW extension through the Pantelleria Rift and onset of syn-rift deposition during the upper Messinian, which could be related with the fast slab retreat of the Calabrian Arc.

 

References:

Le Breton E., M.R. Handy, G. Molli and K. Ustaszewski (2017). Post-20 Ma motion of the Adriatic plate – new constrains from surrounding orogens and implications for crust-mantle decoupling, Tectonics, doi:10.1002/2016TC004443
Ocean wave spectra estimation with the Earth Explorer 10 candidate Harmony
Authors: Kleinherenbrink Marcel , Lopez-Dekker Paco , Chapron Bertrand , Mouche Alexis
Published: March 2021

Tropical cyclones are commonly linked to devastation by hurricane-force winds, storm surges and rainfall. They are also responsible for large exchanges of heat in the upper ocean and the atmosphere, and the transport of large quantities of water from ocean to land. Due to the limited coverage of microwave observations from airplanes and the limited resolution of spaceborne scatterometers, the dynamics inside these extremes are poorly sampled and understood. Synthetic Aperture Radar (SAR) overcomes these limitations, but is only able to recover one-dimensional information, which limits the accuracy of estimated quantities like wind speed, total surface current and wave spectra. Waves radiating outward are, during their development, affected by wind and currents inside of the tropical cyclone and therefore contain information about the structure and dynamics of the system. Wave spectra in tropical cyclones can only partly be recovered, as the quickly changing sea surface limits the resolution of SAR in the azimuth direction. This presentation shows the benefit of having Harmony's bi-static receivers flying in a StereoSAR configuration with Sentinel-1D for the retrieval of wave spectra. Harmony's data allows for the retrieval of a larger fraction of the wave spectra. In the periphery of tropical cyclones Harmony will primarily enhance the recovery of medium-length (100-300 m) swell and wind waves, while Harmony also improves the recovery of long (swell) waves (>200 m) near the eye of the storm.
Improvements to an intermediate complexity atmospheric model for high-resolution downscaling in very complex terrain.
Authors: Reynolds Dylan , Kruyt Bert , Gutmann Ethan , Jonas Tobias , Lehning Michael , Mott Rebecca
Published: March 2021

            Snow deposition patterns in complex terrain are heavily dependent on the underlying topography. This topography affects precipitating clouds at the kilometer-scale and causes changes to the wind field at the sub-kilometer scale, resulting in altered advection of falling hydrometeors. Snow particles are particularly sensitive to changes in the near-surface flow field due to their low density. Atmospheric models which run at the kilometer scale cannot resolve the actual heterogeneity of the underlying terrain, resulting in precipitation maps which do not capture terrain-affected precipitation patterns. Thus, snow-atmosphere interactions such as preferential deposition are often not resolved in precipitation data used as input to snow models. To bridge this spatial gap and resolve snow-atmosphere interactions at the sub-kilometer scale, we couple an intermediate complexity atmospheric model (ICAR) to the COSMO NWP model. Applying this model to sub-kilometer terrain (horizontal resolution of 50 and 250 m) required changes to ICAR’s computational grid, atmospheric dynamics, and boundary layer flow. As a result, the near-surface flow now accounts for surface roughness and topographically induced speed up. This has been achieved by using terrain descriptors calculated once at initialization which consider a point’s exposure or sheltering relative to surrounding terrain. In particular, the use of a 3-dimensional Sx parameter allows us to simulate areas of stagnation and recirculation on the lee of terrain features. Our approach maintains the accurate large-scale precipitation patterns from COSMO but resolves the dynamics induced by terrain at the sub-kilometer scale without adding additional computational burden. We find that solid precipitation patterns at the ridge scale, such as preferential deposition of snow, are better resolved in the high-resolution version of ICAR than the current ICAR or COSMO models. This updated version of ICAR presents a new tool to dynamically downscale NWP output for snow models and enables future studies of snow-atmosphere interactions at domain scales of 100’s of kilometers.
Preliminary results of a multidisciplinary study of the buried peatland and host sediments of the Moscow-Valdai age (Dmitrov, Moscow region, Russia)
Authors: Ershova Ekaterina , Sycheva Svetlana , Kuzmina Svetlana , Zuganova Inna , Panin Pavel , Meteleva Margarita
Published: March 2021

The poster presents preliminary results of multidisciplinary studies of a 5-m section of Middle and Late Pleistocene deposits found in a quarry near the town of Dmitrov, Moscow region. The section includes Moscow fluvioglacial sands, alluvium, lake sapropels, and a layered lens of peat overlain by Valdai cover loams with large cryogenic deformations. The sediments were described and analyzed for pollen, plant macrofossils, and insect remains. The results of pollen analysis suggest that the deposits were formed during the second half of the Mikulino (Eemian) interglacial and during the transition to the Valdai (Weichselian) Glaciation (MIS 5e to MIS 5d). The pollen diagram reflects the replacement of deciduous forests by coniferous forests and the subsequent replacement of closed dark coniferous forests by open communities dominated by birch, shrubs, light-demanding grasses, and Artemisia. Seeds and fruits of wetland and aquatic plants, including endocarps of the extinct species Potamogeton sukaczevii, were found in samples from peat and underlying lake sediments. This may indicate the Mikulino or Early Valdai age of the studied deposits. The entomological fauna indicates the predominance of coastal and marsh species. Environmental conditions were relatively cool, rather characteristic of the late Interglacial. It is expected to obtain micromorphological, physicochemical characteristics of the sediments, as well as OSL dates to clarify the age of the sediments. This work was supported by RFBR, grant N19-29-05024 mk.
Long-term temporal structure analysis of sediment fluxes in the Upper Changjiang (Yangtze River) using a wavelet transformation
Authors: Garijo Noelia , Juez Carmelo , Hassan Marwan , Nadal-Romero Estela
Published: March 2021

Temporal fluctuations of suspended sediment fluxes are highly related with the flow and sediment regime of river networks. Flow dynamics are mainly triggered by climatic forces. Conversely, sediment regime is majorly controlled by land cover/land use changes and by human infrastructures (e.g. dams). Resulting sediment fluxes thus show a non-linear and non-stationary nature.  The wavelet transformation technique emerges as a skilful tool capable of dealing with this type of data. It allows to distinguish within the full spectrum of time-scales, those which are dominant and thus govern the overall trend of the time-series. Furthermore, the temporal multiresolution wavelet technique allows to accurately denoise the discharge and SSC time-series, filtering out the high frequency intermittent physical processes which are superimposed on the main signal. In this research, we analyse a long-term dataset of discharge and sediment fluxes time-series for the Upper Changjiang (Yangtze River, China).
Evaluation of the land use evolution near solid waste landfills using a new weighted environmental index based on GIS techniques
Authors: Rodrigo-Ilarri Javier , Romero-Hernández Claudia P. , Rodrigo-Clavero María-Elena
Published: March 2021

Land use in the nearby of a Municipal Solid Waste (MSW) landfill can be strongly affected by the waste management tasks (transport, landﬁlling and closure). Effects extend from the phases prior to the construction of the landﬁll until years after the completion of the landﬁlling process in areas located beyond the perimeter of the plot occupied by the landﬁll. In this work a new methodology for the analysis of land use change over time is presented. The methodology is based on the use of a new environmental index named WEI (Weighted Environmental Index). WEI is based on the use of GIS techniques accounting for different information sources (digital cartography, aerial photographs and satellite images). WEI assigns environmental values to land use based on the degree of anthropogenic intervention and its occupation surface. A georeferenced multitemporal statistical analysis is performed considering the values of WEI previously assigned to every land use. The methodology has been applied to analyze the land use change near the main MSW landﬁlls of Valencia Region (Spain) where landﬁlling is currently the only waste disposal technique available. Data have been obtained from the Spanish Land Occupation Information System (SIOSE) public database and integrate GIS information about land use/land cover on an extensive, high-detailed scale. Results demonstrate the application of the WEI to real case studies and the importance of integrating statistical analysis of WEI evolution over time to arrive at a better understanding of the socio-economic and environmental processes that induce land-use change.
Assessing heat wave mitigation strategies in a Mediterranean coastal city: how effective are cool roofs and urban green? 
Authors: Ventura Sergi , Badia Alba , Segura Ricard , Gilabert Joan , Llasat Carme , Martilli Alberto , Villalba Gara
Published: March 2021

Heat waves (HW) are expected to become more frequent and intense in urban areas, where currently 54% of the population resides (United Nations, 2018) and 60% are expected to do so by 2030. Urban policy makers are proposing various mitigation strategies, but currently lack the tools to determine how effective they will be in terms of the city´s geography climate and urban morphology. We use the Weather and Research Forecasting Model (WRF)  with the multi-layer Urban Scheme Building Effect Parametrization (BEP) and Building Energy Model (BEP+BEM) (Martilli et al., 2002), to simulate three scenarios proposed by the Urban Master Plan of the Metropolitan Area of Barcelona (AMB) for potential implementation. We include detailed input data using cartography at 10 m resolution and eleven urban classes.  We simulate a HW episode that occurred in July-August 2015 when temperatures reached 40°C during the day and did not go below 25°C at night, for more than five consecutive days. The three potential scenarios simulated are: 1) Increasing the albedo of rooftops to 0.85 for certain urban classes, 2) Increasing the urban green by an additional 255.64 ha according to the proposal of the Master Urban Plan for 2030 with two different irrigation schemes and 3) a combination of these two complementary mitigation strategies. We find that the cool roofs reduce temperatures best during the day (average reductions of 2.22°C), while the additional green areas help moderate temperatures evenly during the day and nighttime (average reductions of 0.15°C and 0.17°C, respectively). However, when irrigation is increased from 2 to 5L/m2day, the temperature reduction potential during the day is intensified due to the cooling effect of more evapotranspiration. The thermal regulation potential of the combined scenario is the most propagated over the AMB and has the highest impact with average daytime reductions of 1.26°C and maximum reduction of 4.73°C at 13:00 UTC.
Morphological rejuvenation on tectonic seamounts: insights from the Gorringe Bank, SW Iberian Margin
Authors: Gamboa Davide , Omira Rachid , Piedade Aldina , Terrinha Pedro , Roque Cristina , Zitellini Nevio
Published: March 2021

Seamounts are spectacular bathymetric features common within volcanic and tectonically active continental margins. During their lifecycles, they evolve through stages of construction and destruction. Seamount chains on the Southwest Iberian Margin are prone to instability and collapse due to regionally complex tectonism with moderate to high seismicity. In this work we investigate collapse episodes during the lifecycle of the tectonic Gorringe Bank (GB), the largest submarine seamount offshore European margins, based on recurrence patterns of MTDs on the active thrust flank. Eight MTDs with relevant expression on the seismic data were analysed, four of estimated Miocene age and four on a Pliocene-Quarternary interval. Miocene MTDs are overall larger and correlate with the main uplift stages of the GB structure. Their distribution and relative timing suggest that failure-triggering earthquakes were common along the whole length of the GB. Pliocene to Quarternary MTDs tend to cluster along the northern half of the GB flank and are generally smaller. Based on our observations, we propose that the lifecycle of tectonic seamounts is marked by morphological rejuvenation episodes driven by tectonic activity between major collapse events or cycles. Tectonic-driven rejuvenation is thus key to hinder or obliterate evidence of past high-magnitude destructive events on tectonic seamount morphology.
Extrinsic anisotropy of two-phase Newtonian aggregates: fabric characterisation and parametrisation, and application to global mantle convection.
Authors: de Montserrat Navarro Albert , Faccenda Manuele , Pennacchioni Giorgio
Published: March 2021

Rocks of the Earth's crust and mantle commonly consist of aggregates of different minerals with contrasting mechanical properties. During progressive, high temperature (ductile) deformation, these rocks tend to develop an extrinsic mechanical anisotropy related to the strain competition of the different minerals, the amount of accumulated bulk strain and the bulk strain geometry. Extrinsic anisotropy is thought to play an important role in a wide range of geodynamic processes up to the scale of mantle convection. However, the evolution of grain-scale and rock-scale associated with this anisotropy cannot be directly implemented in large-scale numerical simulations. For two-phase aggregates -a good rheological approximation of most Earth's rocks- we propose a methodology to indirectly approximate the extrinsic viscous anisotropy by a combination of (i) 3-D mechanical models of rock fabrics, and (ii) analytical effective medium theories. The resulting 3-D mechanical models, confirm that the weak least abundant phase induces substantial rock weakening by forming an inter-connected network of thin layers in the flow direction. 3-D models further suggest, however, that the lateral inter-connection of these weak layers is quite limited, and the maximum structural weakening is considerably less than previously estimated. Ont the other hand, presence of hard inclusions does not have a profound impact in the effective strength of the aggregate, with lineations developing only at relatively low compositional strength contrast. When rigid inclusions become clogged, however, the aggregate viscous resistance can increase over the theoretical upper bound. We show that the modelled grain-scale fabrics can be parameterised as a function of the bulk deformation and material phase properties and can be combined with analytical solutions to approximate the anisotropic viscous tensor. At last, the resulting parameterisation of the extrinsic viscous tensor is implemented in a bi-dimensional global mantle convection code. Preliminary results show that extrinsic is responsible for an increase of the upwelling speed of hot material from the lowermost mantle, different convective cell shapes, and deflection of mantle plumes at the uppermost mantle.
Observation and modelling of whistlers in the ELF as observed by Swarm satellites during regular ASM burst sessions
Authors: Coïsson Pierdavide , Truhlik Vladimir , Mlynarczyk Janusz , Hulot Gauthier , Brocco Laura , Bonnot Olivier , Vigneron Pierre , Burešová Dalia , Chum Jaroslav , Rzonca Pawel , Kulak Andzej
Published: March 2021

The magnetic component of electromagnetic signals in the Extremely Low Frequencies (ELF) has been rarely observed from space. The Swarm satellites have the capability of observing part of this spectral band during burst sessions of the Absolute Scalar Magnetometer (ASM), when the sampling frequency of the instrument is raised to 250 Hz. Burst sessions of one week duration have been acquired regularly since 2019. Swarm satellites drift slowly in local time, therefore it has been possible to progressively acquire burst data to cover all hours at all latitudes. This is a unique opportunity at Low Earth Orbits (LEO) in recent years.

This study focuses on whistlers excited by lightning strikes generated by strong storm systems in the troposphere. The ELF component of the lightning signal propagates in the neutral atmosphere at very long distances. We used data from the ground stations of the World ELF Radiolocation Array (WERA) in order to estimate lightning locations and intensity for remarkable events. Part of the lightning signal penetrates into the ionosphere, where the ionospheric plasma produces its dispersion, depending on the spatial distribution of the plasma and the direction of the magnetic field.

We selected events to simulate their propagation through the ionosphere, using ionosonde data, IRI Real-Time Assimilative Mapping (IRTAM) and International Reference Ionosphere (IRI) model as backgrounds, along with the latest version of the International Geomagnetic Reference Field (IGRF). This technique allows to use these signals to sound the ionosphere and validate ionospheric models.

A database of whistler occurrences and parameters has been constructed and a new Swarm L2 product has been defined to make this data accessible to the scientific community.
Ambient seismic noise monitoring and imaging at the Theistareykir geothermal field (Iceland)
Authors: Toledo Tania , Obermann Anne , Jousset Philippe , Verdel Arie , Martins Joana , Erbas Kemal , Júlíusson Egill , Mortensen Anette , Krawczyk Charlotte
Published: March 2021

The Theistareykir geothermal field is located at the intersection between the active Northern Rift Zone and the active Tjörnes Fracture Zone in NE Iceland, and its study is of vital importance for further development of local and regional geothermal resources. Since autumn 2017, a seismic network consisting of 21 stations was deployed to monitor the high temperature Theistareykir geothermal field (Iceland). This seismic network belongs to a set of multiparameter networks installed to better understand the underlying structure and behavior of the geothermal reservoir under exploitation.

In this framework, we use the continuous ambient noise seismic records between October 2017 and October 2019 to compute a 3D shear wave velocity model of the geothermal field and to detect possible stress changes due to the injection and production activities. We compute the phase auto- and cross-correlations of the vertical component recordings, measure the Rayleigh wave group velocity dispersion curves, and obtain 2D group velocity maps between 1 and 5 s.  The 2D group-velocity maps are used to construct regionalized dispersion curves which are then inverted using a Neighborhood Algorithm to retrieve the 3D Vs model of Theistareykir. We observe various underground structures and identify the locations of possible magmatic or hydrothermal bodies in light of available and newly acquired geological and geophysical data. In addition, we analyze the short and long term temporal evolution of the phase auto-correlations using coda wave interferometry and discuss their relationship to the geothermal field operations. We notice a slightly stronger velocity reduction around the production site in comparison to the surrounding regions.
Distribution of archaeological material scatters and soils at the site of Abila of the Decapolis, northern Jordan
Authors: Lucke Bernhard , Birk Jago , Zech Michael , Voss Nora , Schörner Günther , al-Sababha Hussein
Published: March 2021

Patterns and intensities of past land use are mostly unknown. However, soils in the vicinity of archaeological sites usually carry significant amounts of material culture (mostly pottery sherds) which testify to past human activity. We surveyed surface transects of material culture and soil distribution, radiating from the city center of ancient Abila of the Decapolis. The city had been abandoned during the Medieval and was never resettled, which minimizes the presence of material culture from younger periods. In addition, earlier studies suggested that soil erosion of the rather level limestone plateau surrounding the site was rather limited, indicating that actual land surfaces largely represent those of antiquity. Our survey encountered strongly varying quantities of material culture, which correspond to some soil properties such as concentrations of faeces biomarkers of pork excrements. As the material culture mainly dates to Late Antiquity, and as pork consumption during the Islamic periods is rather unlikely, this indicates that the distribution of the archaeological material was to some degree connected with pig breeding during Antiquity. A possible practice leading to sherd deposition on fields could be manuring, such as from applying dung including pork excrements, but ratios of N-isotopes do not suggest that fields surrounding Abila were subject to application of larger amounts of manure. Therefore, it seems very likely that material culture deposition on the land surrounding Abila was partly connected with the herding of pigs, a land use practice that is attested in Biblical sources on the region.
Can soils act as environmental sponges to help reduce flooding?
Authors: Ahmed Joshua , Thomas Robert E. , Johnson Joshua , Rollason Edward , Skinner Christopher , Parsons Daniel R.
Published: March 2021

Flooding presents a serious socioeconomic challenge to riverine communities across the world, impacting >300 million people each year and causing loss of life, damage to infrastructure, long-term mental and physical health problems, and threatening food security. Across many parts of the globe, including north-west Europe, climate change is projected to increase the magnitude, frequency, and intensity of rainfall events, thus exacerbating future flood risk and increasing the demand for flood alleviation schemes. Historically, flood prevention strategies have focused on constructing hard defences that restrict the overbank flows and aim to convey them downstream. However, as floods become larger and more difficult to predict, the construction of ever-higher defences becomes unfeasible. As such, natural-based solutions are being adopted as a more cost-effective and sustainable approach to managing flood waters through upland attenuation in leaky dams and offline storage in reservoirs in the lowlands. Here we demonstrate the feasibility and efficacy of using agricultural soils as “environmental sponges” to retain moisture and reduce downstream flood peaks in a heavily-managed lowland catchment. We use combined field, laboratory, and modelling approach to quantify how increases in soil organic matter – introduced through cover crops – can increase soil moisture retention at the field scale and perform groundwater and catchment modelling scenarios to assess how these changes can be extrapolated up to the catchment scale and used to forecast changes in downstream flood risk across a suite of future hydro-climatic and soil management scenarios.
Increasing Mobility of High Arctic Sea Ice Increases Marine Hazards off the East Coast of Newfoundland
Authors: Babb David , Barber David , Ehn Jens , Chan Wayne , Mathes Lisa , Dalman Laura , Campbell Yanique , Harasyn Madison , Lukovich Jennifer , Zagon Tom , Papakyriakou Tim , Capelle David , Gariepy Alain
Published: March 2021

As the Arctic ice cover has transitioned to a younger and thinner state it has become weaker and therefore increasingly mobile. One of the key indicators of this change is the increase in ice flux through Nares Strait, which connects the central Arctic to Baffin Bay and is an export pathway for some of the oldest and thickest sea ice remaining within the Arctic. Historically ice flux through the narrow Strait was seasonally limited by the formation of an ice arch, however as the ice cover has thinned the arch no longer forms every winter, and when it does form it tends to break up earlier. An increase in ice flux through Nares Strait not only affects the retention of old thick ice within the central Arctic, but also affects the icescape downstream of the Strait that extends from Baffin Bay, through the Labrador Sea and towards the southern ice edge around Newfoundland. While an ice cover does form annually around Newfoundland, it is typically a thin seasonal ice cover, which forms in January and is gone by May. However, during spring 2017 the ice conditions were considerably heavier, presenting hazardous conditions for the local maritime industry into June and requiring the Canadian Coast Guard research ice breaker Amundsen be pulled off of its scientific cruise and used to escort vessels and conduct search and rescue operations along Newfoundland’s northeast coast. The ice cover was considerably thicker and more extensive than previous years and sank two fishing vessels that became beset within the ice pack. Using a unique suite of in situ observations we confirmed that multiyear sea ice from the central Arctic was present within this anomalous ice cover. Using satellite imagery and regional ice charts we tracked the source of this multiyear ice back to Nares Strait and the central Arctic. While regional in focus, this work highlights how the decline of the Arctic ice pack has implications for downstream areas where risk may be increasing as the ice pack declines.
Using the depth of the centre of gravity as an indicator on the state of the general ocean circulation
Authors: Schmiedel Benjamin , Roquet Fabien
Published: March 2021

An approach is here investigated that uses the depth of the centre of gravity as a central ocean property, thought to give a clear and practical indicator on the state of the general ocean circulation. The depth of the gravity centre can be directly linked to the volume-integral of potential energy, or of dynamic enthalpy when making the Boussinesq approximation, and therefore to the strength of the global mean stratification. Because the stratification is directly linked to the global overturning circulation, it is hypothesized that the depth of the centre of gravity can be used to assess the state of global circulation. In order to test this hypothesis, the depth of the centre of gravity is diagnosed in an ocean model simulation for an idealized square basin configuration with the NEMO model. The centre of gravity is compared to the value it would have if the ocean was perfectly well mixed, giving a state of maximum potential energy. We find in our idealized simulation that the centre of gravity is lowered by only 22 cm compared to the reference well-mixed state, reflecting the potential energy that would be required to destroy the ocean stratification. The smallness of that number highlights the inefficiency of the ocean engine. Furthermore, the dynamic balance setting the depth of the gravity centre is investigated, diagnosing separately the tendency terms on the equation of conservation of potential energy. A positive change (sinking) of the centre of gravity indicates an input of high density water into lower levels or low density water in upper levels, essentially enhancing the global mean stratification, while for a negative change (lifting) it is reversed. The goal is to compare the relative role of the wind stress, surface buoyancy forcing and internal mixing in setting the general circulation.
Evaluation of interannual variability of Arctic and Antarctic ozone loss since 1989
Authors: Goutail Florence , Pazmino Andrea , Pommereau Jean-Pierre , Lefevre Franck , Godin-Beekmann Sophie , Hauchecorne Alain , Lecouffe Audrey , Clerbaux Cathy , Boynard Anne , Hadji-Lazaro Juliette , Chipperfield Martyn , Feng Wuhu , VanRoozendael Michel , Jepsen Nis , Hansen Georg , Kivi Rigel , Bognar Kristof , Strong Kimberly , Walker Kaley , Colwell Steve
Published: March 2021

Ozone depletion over Polar Regions is monitored each year by satellite and ground-based instruments. The first signs of healing of the ozone layer linked to the decrease of ozone destructive substances (ODSs) were observed in Antarctica using different metrics (ozone mean values, ozone mass deficit, area of the ozone hole) and simple or sophisticated models. Chemistry climate models predict that climate change will not affect expected ozone recovery over Antarctica but will accelerate recovery in the Arctic due to the possible enhancement of the Brewer Dobson circulation. However, ozone loss observations by SAOZ UV-Vis spectrometers do not show a clear sign of recovery in the latter region. In addition, a record of 38% ozone loss in 2010/2011 and 2019/2020 was estimated.

In this study, the vortex-averaged ozone loss in the last three decades will be evaluated for both Polar Regions using the passive ozone tracer of two chemical transport models (REPROBUS and SLIMCAT CTMs) and total ozone observations from SAOZ and satellite observations (IASI/METOP and Multi-Sensor Reanalysis (MSR-2)).

The tracer method allows us to determine the evolution of the daily rate of ozone destruction, and the amplitude of the cumulative loss at the end of the winter. The cumulative ozone destruction in the Artic varies between 0-10% in relatively warm winters with short vortex duration to up to 25-38% in colder winters with longer vortex persistence, while in Antarctica it is mostly stable, around 50%.

Interannual variability of 10-days average rate will be analyzed and compared between both hemispheres as well as the timing to reach different thresholds of absolute ozone loss values. Finally, linear trend of ozone loss and temperature since 2000 will be estimated in both Polar Regions in order to evaluate possible ozone recovery.
Using an Extreme Gradient Boosting Learner for Mapping Hydrogeochemical Parameters in Germany
Authors: Nölscher Maximilian , Broda Stefan
Published: March 2021

Information on the spatial distribution of hydrogeochemical parameters is crucial for decision making. Machine learning based methods for the mapping of hydrogeochemical parameter concentrations have been already studied for many years to evolve from deterministic and geostatistical interpolation methods. However, the reflection of all relevant processes that the target variable depends on is often difficult to achieve, because of the mostly insufficient determination and/or availability of features. This is especially true if you limit yourself to freely accessible data.

In this study, we apply an extreme gradient boosting learner (XGB) to map major ion concentrations across Germany. The training data consist of water samples from approximately 50K observation wells across Germany and a wide range of environmental data as predictors. The water samples were collected between the 1950s and 2005 at anthropogenically undisturbed locations.

The environmental data includes hydrogeological units and parameters, soil type, lithology, digital elevation model (DEM) and DEM derived parameters etc. The values of these features at the respective water sample location were extracted on the basis of a polygon, approximately representing the area that has an impact on the target variable (ion concentration). For a comparison, different polygon shapes are used.

The model was set up as chained multioutput regression, meaning that the prediction of the previous model in a linear sequence of single-output models is used as input for the subsequent model.

The results are planned to serve for a comparison with state-of-the-art deep learning architectures.
Surface fractures and deformation of the magnitude 5.6 earthquake near Reykjavík on 20 October 2020
Authors: Jónsson Sigurjón , Cao Yunmeng , Vasyura-Bathke Hannes , Li Xing
Published: March 2021

On 20 October 2020, Reykjavík was rocked by the largest earthquake in southwest Iceland in over a decade when a magnitude 5.6 event occurred only 25 km from the city. The earthquake caused movement on multiple surface fractures, distributed over an 8-km-long north-south oriented area, indicating the location of the underlaying right-lateral strike-slip fault rupture. We mapped the coseismic surface fractures and deformation using Sentinel-1 and TerraSAR-X InSAR data, selecting with a new method the best pre- and post-earthquake SAR scenes from analyzing the tropospheric signals on each SAR image. This method does not require masking out deformed areas when determining the InSAR covariance structure and thus yields better earthquake source estimations. As the InSAR data are primarily sensitive to east-west and vertical displacements, we additionally used split-beam interferometry to obtain more information about north-south displacements. For this, we used burst-overlap interferometry (BOI), in the case of Sentinel-1 data, and multiple-aperture interferometry (MAI) on the TerraSAR-X data. Together with the standard InSAR data, we estimated the full 3D coseismic surface displacement field of the earthquake. The results show that most of the fractures had limited surface offsets, apart from a 2-3 km long north-south trending segment just north of the epicenter that was right-laterally offset by about 15 cm. Source modeling of the earthquake shows that the deformation is consistent with a near vertical north-south striking fault with up to ~30 cm of slip located at roughly 3 km depth below the surface. The estimated geodetic moment of the model amounts to a magnitude 5.6 earthquake, consistent with seismological estimates. Most of the modeled fault slip and mapped surface fractures are located north of the earthquake epicenter, indicating that the earthquake ruptured unilaterally from south to north, which agrees with the more severe surface effects and shaking reported from near the northern end of the earthquake rupture.
Comparison of complementary methods of melt pond depth retrieval on different spatial scales
Authors: Linhardt Felix , Fuchs Niels , König Marcel , Webster Melinda , von Albedyll Luisa , Birnbaum Gerit , Oppelt Natascha
Published: March 2021

Pond bathymetry and average pond depth on Arctic sea ice are important for characterizing and quantifying the distribution of  surface melt water volume. Melt pond models that take depth into account used to be based on manual in situ measurements; however, the capability of measuring pond depth through other means have increased substantially in recent years .

We take advantage of the extensive sampling and data recorded during the 2019-2020 MOSAiC campaign to compare different melt pond depth retrievals from a unique case study involving a melt pond in the center of the MOSAiC floe.  Thus, we are able to present the most recent upscaling cascade of pond depth measurement methods. 

The methods we examine in our contribution include in-situ echo sounder and hyperspectral measurements, airborne hyperspectral and photogrammetry-based measurements, as well as spaceborne multispectral measurements. Each method is assessed regarding its spatial resolution, retrieval accuracy, technical prerequisites and limitations.