bluuebunny/crossref_metadata_2025 huggingface dataset:
Daily Satellite Observations of Methane from Oil and Gas Production Regions in the United States
Authors: Levelt Pieternel , Veefkind Pepijn , Roosenbrand Esther , Lin John , Landgraf Jochen , Dix Barbara , de Gouw Joost
Published: March 2020

Production of oil and natural gas in North America is at an all-time high due to the development and use of horizontal drilling and hydraulic fracturing. Methane emissions associated with this industrial activity are a concern because of the contribution to climate radiative forcing. We present new measurements from the space-based TROPOspheric Monitoring Instrument (TROPOMI) launched in 2017 that show methane enhancements over production regions in the United States. Using methane and NO2 column measurements from the new TROPOMI instrument, we show that emissions from oil and gas production in the Uintah and Permian Basins can be observed in the data from individual overpasses. This is a vast improvement over measurements from previous satellite instruments, which typically needed to be averaged over a year or more to quantify trends and regional enhancements in methane emissions. In the Uintah Basin in Utah, TROPOMI methane columns correlated with in-situ measurements, and the highest columns were observed over the deepest parts of the basin, consistent with the accumulation of emissions underneath inversions. In the Permian Basin in Texas and New Mexico, methane columns showed maxima over regions with the highest natural gas production and were correlated with nitrogen-dioxide columns at a ratio that is consistent with results from in-situ airborne measurements. The improved detail provided by TROPOMI will likely enable the timely monitoring from space of methane and NO2 emissions associated with regular oil and natural gas production.
The NASA Operation IceBridge Sea Ice Freeboard, Snow Depth and Thickness Product
Authors: Harbeck Jeremy , Kurtz Nathan , Petty Alek
Published: March 2020

Over the eleven-year lifetime of NASA’s Operation IceBridge, the Project Science Office has released an along-track sea ice freeboard, snow depth and thickness product in varying forms. Multiple versions of archival products are available for a number of the project’s early years and more recently quicklook versions, rapid-turnaround products primarily produced for summer sea ice forecasting, have been available for Arctic campaigns. During 2020, the mission’s close-out year, we are producing a final archival version of the product that will fill gaps in data availability and incorporate multiple improvements in the processing chain. These improvements include laser altimetry and snow radar pre-processing and ingestion upgrades, improved image analysis, updated tide and atmospheric models, updated gridding methodology and enhanced product outputs. The final result will constitute a state-of-the-art, internally self-consistent data product for all springtime Arctic and Antarctic Operation IceBridge campaigns.
Tsunami-derived sediments identified in the destruction sequence of an 8th century warehouse in Caesarea Maritima, Israel
Authors: Everhardt Charles , 'Ad Uzi , Barkai Ofra , Jaijel Roi , Robins Lotem , Roskin Joel , Goodman-Tchernov Beverly
Published: March 2020

Preserved on land coastal tsunami deposits onshore have rarely been reported for the coastline of Israel. According to offshore sedimentological records, a tsunami struck the coast of early Islamic Caesarea Maritima, likely coinciding with a major earthquake in 749 AD. Anomalous sand layers from the same time period were reported by archaeologists in structures near the shore, but they were recorded with varied interpretations (construction fill, dune development, general abandonment). Unfortunately, no sediments were collected nor analyzed from those excavations. Recently, an area with this same deposit was freshly excavated. This allowed it to be studied to determine its taphonomic history. The deposit is comprised of a thick, well-sorted sand layer with semi-articulated sequences of building stones followed by independent matrix-supported building stones, the entire deposit sandwiched between an early-eighth century abandonment layer and a late-eighth century floor. Two sediment cores from the deposit, as well as reference samples representative of other depositional environments, have been analyzed for grain size distribution, foraminiferal abundance, diversity, taphonomic characterization, relative age by portable luminescence (POSL), and loss on ignition. In tandem, reference samples from modern beach, dunes, an eighth century archaeological construction fill, and shallow marine sands were analyzed as reference samples for comparison. The combination of results indicates that the sandy deposit formed during a high-energy event, and does not resemble other known types of sand deposits in the area, including those suggested as possible interpretations by the excavators. The results of this study will contribute to the understanding of tsunami deposits preserved on land in Caesarea Maritima, provide geographical constraints to enhance coastal inundation models and hazard/risk area maps, and more broadly contribute to the understanding of tsunami sedimentological studies in geoarchaeological contexts. 
Perspective of the rehabilitation of marginal areas: the case of Lablab purpureus (L.) Sweet
Authors: Vidigal Patrícia , Santos Erisa S. , Correia Augusto Manuel , Monteiro Fernando , Abreu Maria Manuela
Published: March 2020

It is estimated that the world population reach 9.1 billion in 2050 resulting in increasing food demand and consumption, but also waste production. Moreover, to help achieve the goals set by the 2030 Agenda for Sustainable Development, it is imperative to develop sustainable strategies for the recovery marginal lands (e.g. landfills or abandoned mining areas) and create conditions for agriculture activities. Thus, there is a need to increase agricultural production and to create sustainable waste management approaches. Several landfills pose health and environmental concerns associated to non-selective deposition of wastes, which present potentially hazardous elements (PHE), and inexistence of environmental management systems. Therefore, leachates rich-in PHE can spread to adjacent areas leading to soil and water contamination. This is particularly concerning considering the growing rate of Sub-Saharan African (SSA) population that will be living in urban or peri-urban areas, and practice subsistence farming in those areas. For SSA it is estimated that by 2050 about 50% of the population will be living in towns and cities. The recovery of landfills, in addition to other environmental management measures, can involve the development of a secure plant cover that creates conditions for agriculture activities, while protecting the food-chain, but also improve environmental and landscape impacts. Plant species selected for green cover should have the ability to decrease the mobility or immobilize PHE in the rhizosphere. Furthermore, these plant species should also have low PHE translocation factors from the soil/roots to the shoots. Plants with these characteristics are not common, and it is necessary to increase our efforts to identify them. Moreover, in the scope of SSA it is important that these species should be native and known by the population. The study of African crops behaviour, such as Lablab purpureus (L.) Sweet, can be a promising option since Lablab shows the ability to accumulate PHE in the roots and low translocation factors from the soil/roots to the shoots, resulting the concentrations present in the shoots safe for animal consumption. It is important to point that the characteristics of each landfill can be totally different as well as climatic conditions where is located the landfill, thus the initial and multidisciplinary characterization of the study area is crucial. Moreover, the ecophysiological plant behaviours, namely PHE accumulation in the edible part, depends on plant species and edafoclimatic conditions, so more studies should be done in order to assess the impact in the food-chain.
The importance of static and dynamic head drivers for hyporheic exchange: evaluation of a spectral modelling approach
Authors: Morén Ida , Riml Joakim , Wörman Anders
Published: March 2020

Groundwater surface water interactions can greatly impact the ecohydrology on a wide range of spatial scales, ranging from biogeochemical reactions under local bedforms to alteration of regional groundwater discharge patterns. Hyporheic exchange fluxes (HEF) are controlled by the streambed geology and driven by hydraulic head fluctuations at the stream bottom, consisting of a static and a dynamic part. Currently, few studies have investigated the relative importance of these two drivers of HEF in the field, which hinder a holistic understanding of the governing processes and may affect predictions of hyporheic exchange intensities.

This study is based on an extensive field survey of 9 stream reaches located in small, pristine streams in Sweden, with varying hydromorphological characteristics such as slope, bottom material, morphological complexity and stream discharge. The field survey included distributed measurements of the hydraulic head and the hydraulic conductivity along the streambed, as well as tracer tests with Rhodamine WT. The overall aim of the study was to evaluate the relative importance of HEF driven by dynamic and static head fluctuations in streams by usage of a spectral model that decomposes the observed hydraulic head fluctuations on distinctive spatial scales. As a validation, the advective storage path (ASP) transport model was calibrated against the conducted in-stream tracer tests and its parameters compared to the equivalent gained from the spectral model.

The results showed that the average exchange velocity evaluated by the two models were comparable in most observed cases, validating the usage of the spectral model in small alluvial streams with high slope, and low discharge and stream depth. However, a sensitivity analysis of the two models revealed some degree of equifinality for some of the independent model parameters. Detailed results from the spectral model indicated that the static head was dominating the HEF in all reaches, both on average and when distributed over separate spatial scales. Uncertainty in the results was found, predominantly effecting calculations of the dynamic HEF and connected to (1) the approximation of streambed topography at spatial scales <0.5 m, where the dynamic exchange is assumed to dominate and (2) the use of Fehlman’s constant for estimating the hydrodynamic exchange under complex streambed topographies. Despite those uncertainties, the spectral model approach gives a deeper understanding of the phenomena of HEF by incorporating its multiscale nature and illustrating the fact that static and dynamic drivers might be equally important, only acting on different scales.
Automatic high-resolution mapping and classification of avalanche terrain regarding potential release, triggering and run-out zones
Authors: Harvey Stephan , Schmudlach Günter , Bühler Yves , Lukas Dürr , Stoffel Andreas , Christen Marc
Published: March 2020

Terrain characteristics are one of the main factors contributing to avalanche formation as well as affecting the runout. Hence, terrain assessment is crucial for planning and decision making when travelling in the backcountry. So far, terrain is mainly interpreted manually from topographic maps or by observations in the field. Recent support for interpreting avalanche terrain is given by slope angle layers derived from digital elevation models or the Avalanche Terrain Exposure Scale (ATES) for classifying avalanche terrain manually. While digital elevation models and numerical simulations are used as standard for mapping avalanche hazard threatening settlements and key infrastructure, this is hardly the case when planning tours in the backcountry. Thus, our scope was to classify and map terrain of maximum size class 3 avalanches, which typically threaten backcountry recreationists. We present a new methodology for a high-resolution automatic classification of the avalanche terrain specifically for recreational backcountry travel by taking into account: a) potential avalanche release areas, b) remote triggering of avalanches, c) possible runout zones of max. size 3 avalanches.

Potential release areas were specified by computing a density estimate based on terrain characteristics of observed avalanche starting zones in the Davos region. The potential of remote triggering was estimated with a least-cost path analyses depending on the triggering distance from remotely triggered avalanches. Avalanche runout zones were performed with the avalanche simulation model RAMMS::EXTENDED. Combining all these methods and out of many simulations a classified avalanche terrain map for the entire Swiss Alps and the Jura was created characterizing potential release areas and runout zones. A validation of 870 accidental avalanches in the backcountry of Switzerland shows that only 2% of the mapped avalanche perimeters do not overlap with the simulations. The distribution of the terrain characteristics within both the release areas of the training dataset and the validation data was almost identical. Thus, the extrapolation from the calculated density estimate to the whole of Switzerland is feasible and appropriate. The created map assists the interpretation of avalanche terrain for travelling in the backcountry considering release areas and runout zones. Although the focus is on Switzerland, the methods can also be applied to other mountain areas worldwide.
Impacts of strong surface winds on Antarctic Polynya
Authors: McDonald Adrian
Published: March 2020

This study investigates the impacts of strong wind events on the sea ice concentration within polynya regions, with a focus on the Ross Sea Polynya (RSP). In particular, this work quantifies the sensitivity of sea ice concentrations to surface winds and whether there are threshold wind speeds required for regions of the polynya  to open up with subsequent impacts on air-sea heat fluxes. To analyse these processes, we examine version 3.1 of the Bootstrap sea ice concentration (SIC) satellite data set derived from SSM/I brightness temperatures and how they are connected to the surface winds from the ERA5 reanalysis over the period 1979 to 2018. While we examine these relationships around the entire Antarctic continent, we focus on the RSP and low-level jets in the Ross Sea. In particular, we examine how strong wind events which impact SIC in the RSP are linked to Ross Ice Shelf Air Stream events (strong low-level jets in the region). The hypothesis that the increase in Ross Ice Shelf Air Stream events, associated with a strengthening of the Amundsen Sea Low, has contributed to trends in sea ice production in this region is examined.
Making radioactivity measurements on building materials accessible to everyone
Authors: Serafini Andrea , Alberi Matteo , Carconi Pierluigi , Chiarelli Enrico , De Felice Pierino , Deserventi Andrea , Donati Massimiliano , Fanchini Erica , Giordano Ferdinando , Grignani Paolo , Iovene Alessandro , Luciani Luciano , Manessi Giacomo , Mantovani Fabio , Marini Marco , Morichi Massimo , Pepperosa Andrea , Raptis Kassandra Giulia Cristina , Rogo Francesco , Strati Virginia ,   CORSAIR
Published: March 2020

The CORSAIR (Cloud Oriented Radiation Sensor for Advanced Investigation of Rocks) project was born to meet the EU guidelines 2013/59/EURATOM on safety standards for protection against ionizing radiations. The project designed an automated system capable of providing a real-time measurement of the radioactive activity concentration index for building materials according to regulations of more than 20 different countries. Measurements are conducted through in situ gamma-ray spectroscopy techniques on 3 x 3 x 3 m3 blocks of rock at quarries and processing centers, and quantify the activities, the abundances and the related effective dose-rates of natural radionuclides (40K, 232Th, 238U and their progenies) in stone materials for the building industry. The detector comprises a 2” x 2” cylindric CeBr3 crystal having a 2.5% energy resolution at 1461 keV. A lateral lead shield of 1.3 cm enables a ~60% reduction of the gamma signal coming from above and beside the detector. The system is designed for providing the radiometric index in less than 30 min with an overall uncertainty of the order of 5%.

The innovative aspects of the detector are in its autonomous operation and the easy fruition of the results of the material characterization. Energy calibration and peak recognition are automatically performed onâ€‘board through an innovative stochastic method based on simulated annealing. The computation of the results is fully-automated and requires no intervention of the operator. The battery-powered detector is equipped with GPS, LoRa, Bluetooth and Wi-Fi connectivity and can be remotely controlled thanks to a dedicated Android app. Acquired data and activity indexes are synced through LoRa connectivity to a cloud database, where they can be easily accessed by sellers and buyers, thus preventing the placing on the market of blocks hazardous to public health.
Effect of shock ripples on electron acceleration and reflection at the quasi-perpendicular bow shock
Authors: Graham Daniel , Khotyaintsev Yuri , Vaivads Andris , Andre Mats , Lalti Ahmad , Dimmock Andrew , Johlander Andreas
Published: March 2020

At Earth’s bow shock electrons can be reflected and accelerated along magnetic fields lines, which can then form electron beams and excite Langmuir and beam-mode waves. These electron beams form when the shock normal angle is close to 90 degrees. However, recent observations have shown that quasi-perpendicular shocks can be non-stationary and exhibit ripples, which can modify the local shock-normal angle and cross-shock potential. We use Magnetospheric Multiscale (MMS) data to investigate the effects of shock ripples on the accelerated electrons observed in the electron foreshock. We compare the results with test-particle simulations to determine the effect of shock ripples on electron acceleration. We discuss the implications of these results for the generation of plasma frequency waves and radio emission in the electron foreshock region. 
The mutual impact of weather regimes and the stratospheric circulation on European surface weather
Authors: Grams Christian M. , Beerli Remo , Büeler Dominik , Domeisen Daniela I. V. , Papritz Lukas , Wernli Heini
Published: March 2020

Extreme states of the winter stratosphere, such as sudden stratospheric warmings (SSWs) or an extremely strong stratospheric polar vortex (SPV), can affect surface weather over the North-Atlantic European region on subseasonal time scales. Here we investigate the occurrence of Atlantic-European weather regimes during different stratospheric conditions in winter and their link to large-scale weather events in European sub-regions. We further elucidate if the large-scale flow regime in the North Atlantic at SSW onset determines the subsequent downward impact.

Anomalous stratospheric conditions modulate the occurrence of weather regimes which project strongly onto the NAO and the likelihood of their associated weather events. In contrast weather regimes which do not project strongly onto the NAO are not affected by anomalous stratospheric conditions. These regimes provide pathways to unexpected weather events in extreme stratospheric polar vortex states. For example, Greenland blocking (GL) and the Atlantic Trough (AT) regime are the most frequent large-scale flow patterns following SSWs. While in Central Europe GL provides a pathway to cold and calm weather, AT provides a pathway to warm and windy weather. The latter weather conditions are usually not expected after an SSW. Furthermore, we find that a blocking situation over western Europe and the North Sea (European Blocking) at the time of the SSW onset favours the GL response and associated cold conditions over Europe. In contrast, an AT response and mild conditions are more likely if GL occurs already at SSW onset. An assessment of forecast performance in ECMWF extended-range reforecasts suggests that the model tends to forecast too cold conditions following weak SPV states.

In summary, weather regimes and their response to anomalous SPV states importantly modulate the stratospheric impact on European surface weather. In particular the tropospheric impact of SSW events critically depends on the tropospheric state during the onset of the SSW. We conclude that a correct representation of weather regime life cycles in numerical models could provide crucial guidance for subseasonal prediction.

 

References:

Beerli, R., and C. M. Grams, 2019: Stratospheric modulation of the large-scale circulation in the Atlantic–European region and its implications for surface weather events. Q.J.R. Meteorol. Soc., 145, 3732–3750, doi:10.1002/qj.3653.

Domeisen, D. I. V., C. M. Grams, and L. Papritz, 2020: The role of North Atlantic-European weather regimes in the surface impact of sudden stratospheric warming events. Weather and Climate Dynamics Discussions, 1–24, doi:https://doi.org/10.5194/wcd-2019-16.
Transport of polyamide microplastics at the sediment-water interface – First results from mesocosm studies
Authors: Schneidewind Uwe , Nel Holly , Kukkola Anna , Sambrook Smith Greg , Lynch Iseult , Krause Stefan
Published: March 2020

The occurrence of microplastics in the environment has become a major research interest in the last years. Aside from the marine environment, microplastic particles in various amounts, forms and compositions have now also been identified in freshwater bodies, groundwater, soils and interfaces connecting these compartments such as the hyporheic zone. Their transport and fate in these compartments has thus become the focus of recent field and laboratory studies.

Here we present first results from mesocosm studies performed at the Environmental Change Outdoor Laboratory (ECOLAB) facility of the University of Birmingham, UK. In a series of experiments conducted in recirculating flumes (12 setups in total, flume dimensions are 200 by 42 by 15 cm) we studied the behaviour of polyamide fragments and fibers in two different types of sediments and under different flow conditions. Polyamide fragments (diameter < 600 μm) were obtained from crushing larger pellets using a ball mill and liquid nitrogen while fibers (Flock Depot, Germany, fiber length of 500 μm, 1.7 dtex) were obtained commercially. Sand and gravel of known particle diameter ranges were used to represent natural sediments. Flow experiments were conducted over several days in duplicate by injecting a known concentration of microplastic particles into the flumes and taking samples (20 mL) at three flume locations at predefined intervals. Target particles were stained with Nile red before injection for better visibility and further analyzed using a stereomicroscope after filtering. First results show significant differences in fiber and fragment particle concentrations suspended in the water column/retained in the sediments as well as between different fragment sizes.

Further studies are planned as to the long-term behaviour of these microplastics in freshwater sediments experiencing biofilm growth as well as regarding possible chemical additives. The information generated with these flume experiments improves our understanding of microplastic distribution and immobilization at the sediment-water interface.
Synthetic sampling for spatio-temporal land cover mapping with machine learning and the Google Earth Engine in Andalusia, Spain
Authors: Bindereif Laura , Rentschler Tobias , Batelheim Martin , Díaz-Zorita Bonilla Marta , Gries Philipp , Scholten Thomas , Schmidt Karsten
Published: March 2020

Land cover information plays an essential role for resource development, environmental monitoring and protection. Amongst other natural resources, soils and soil properties are strongly affected by land cover and land cover change, which can lead to soil degradation. Remote sensing techniques are very suitable for spatio-temporal mapping of land cover mapping and change detection. With remote sensing programs vast data archives were established. Machine learning applications provide appropriate algorithms to analyse such amounts of data efficiently and with accurate results. However, machine learning methods require specific sampling techniques and are usually made for balanced datasets with an even training sample frequency. Though, most real-world datasets are imbalanced and methods to reduce the imbalance of datasets with synthetic sampling are required. Synthetic sampling methods increase the number of samples in the minority class and/or decrease the number in the majority class to achieve higher model accuracy. The Synthetic Minority Over-Sampling Technique (SMOTE) is a method to generate synthetic samples and balance the dataset used in many machine learning applications. In the middle Guadalquivir basin, Andalusia, Spain, we used random forests with Landsat images from 1984 to 2018 as covariates to map the land cover change with the Google Earth Engine. The sampling design was based on stratified random sampling according to the CORINE land cover classification of 2012. The land cover classes in our study were arable land, permanent crops (plantations), pastures/grassland, forest and shrub. Artificial surfaces and water bodies were excluded from modelling. However, the number of the 130 training samples was imbalanced. The classes pasture (7 samples) and shrub (13 samples) show a lower number than the other classes (48, 47 and 16 samples). This led to misclassifications and negatively affected the classification accuracy. Therefore, we applied SMOTE to increase the number of samples and the classification accuracy of the model. Preliminary results are promising and show an increase of the classification accuracy, especially the accuracy of the previously underrepresented classes pasture and shrub. This corresponds to the results of studies with other objectives which also see the use of synthetic sampling methods as an improvement for the performance of classification frameworks.
Preliminary Positioning Results From NGS’s Upcoming Multi-GNSS Processing Software
Authors: Stressler Bryan , Heck Jacob , Bilich Andria , Ogaja Clement
Published: March 2020

The U.S. National Geodetic Survey (NGS) is undertaking a project to replace and modernize its global navigation satellite system (GNSS) processing software that has been in use for several decades. The goals of this project are to: 1) transition from dual-frequency GPS-only to multi-constellation multi-frequency data processing, 2) develop well-documented modular and extensible software written in modern programming and scripting languages, and 3) replace the operational PAGES software suite as the processing engine responsible for monitoring the NOAA Continuously Operating Reference System Network (NCN), orbit production for the International GNSS Service (IGS) combinations, and the Online Positioning User Service (OPUS). To date, the GNSS software team at NGS has developed the foundational software libraries and tools needed for GNSS data processing (e.g, RINEX readers, standard GNSS models) and has begun to produce double-difference baseline solutions with the new software. This valuable first step enables us to compare solutions from the new software with those of the legacy PAGES software. Here we present our preliminary solutions, compare them with those of PAGES, and discuss the next steps to improve the positioning accuracy and to take full advantage of multi-GNSS observations.
Crustal structure of Sri Lanka derived from joint inversion of surface wave dispersion and receiver functions using a Bayesian approach
Authors: Dreiling Jennifer , Tilmann Frederik , Yuan Xiaohui , Haberland Christian , Seneviratne S.W. Mahinda
Published: March 2020

We study the crustal structure of Sri Lanka by analyzing data from a temporary seismic network deployed in 2016-2017 to shed light on the amalgamation process from the geophysical perspective. Rayleigh wave phase dispersion from ambient noise cross-correlation and receiver functions were jointly inverted using a transdimensional Bayesian approach.

The Moho depths range between 30 and 40 km, with the thickest crust (38-40 km) beneath the central Highland Complex (HC). The thinnest crust (30-35 km) is found along the west coast, which experienced crustal thinning associated with the formation of the Mannar Basin. Vp/Vs ratios lie within a range of 1.60-1.82 and predominantly favor a felsic composition with intermediate-to-high silica content of the rocks.

A major intra-crustal (18-27 km), slightly westward dipping (~4.3°) interface with high Vs (~4 km/s) underneath is prominent in the central HC, continuing in the eastern Vijayan Complex (VC). The dipping discontinuity and a low velocity zone in the central Highlands can be related to the HC/VC contact zone and is in agreement with a well-established amalgamation hypothesis of a stepwise collision of the arc fragments, including deep crustal thrusting processes and a transpressional regime along the suture between the HC and VC.
The Evolution and Role of Solar Wind Turbulence in the Inner Heliosphere
Authors: Chen Christopher ,   PSP FIELDS and SWEAP Teams
Published: March 2020

The first two orbits of the Parker Solar Probe (PSP) spacecraft have enabled the first in situ measurements of the solar wind down to a heliocentric distance of 0.17 au (or 36 Rs). Here, we present an analysis of this data to study solar wind turbulence at 0.17 au and its evolution out to 1 au. While many features remain similar, key differences at 0.17 au include: increased turbulence energy levels by more than an order of magnitude, a magnetic field spectral index of -3/2 matching that of the velocity and both Elsasser fields, a lower magnetic compressibility consistent with a smaller slow-mode kinetic energy fraction, and a much smaller outer scale that has had time for substantial nonlinear processing. There is also an overall increase in the dominance of outward-propagating Alfvenic fluctuations compared to inward-propagating ones, and the radial variation of the inward component is consistent with its generation by reflection from the large-scale gradient in Alfven speed. The energy flux in this turbulence at 0.17 au was found to be ~10% of that in the bulk solar wind kinetic energy, becoming ~40% when extrapolated to the Alfven point, and both the fraction and rate of increase of this flux towards the Sun is consistent with turbulence-driven models in which the solar wind is powered by this flux.
ICEBEAR: Recent Results from a Bistatic Coded Continuous-Wave E-region Coherent Scatter Radar
Authors: Huyghebaert Devin , Lozinsky Adam , Hussey Glenn , McWilliams Kathryn , Galeschuk Draven , St. Maurice Jean-Pierre , Urco Miguel , Chau Jorge , Vierinen Juha
Published: March 2020

The Ionospheric Continuous-wave E-region Bistatic Experimental Auroral Radar (ICEBEAR) is located in Canada and has a field of view centered at (58°N, 106°W) overlooking the terrestrial auroral zone.  This 49.5 MHz coherent scatter radar measures plasma density irregularities in the E-region ionosphere using a pseudo random noise phase modulated continuous-wave (CW) signal.  ICEBEAR uses this coded CW signal to obtain simultaneous high temporal (1 s) and spatial (1.5 km) resolutions of E-region plasma density turbulence over a 600 km x 600 km field of view, providing insights into the Farley-Buneman plasma density instability and wave-like structures evident in the coherent scatter.  The initial results from ICEBEAR were obtained with a 1D receiving array, providing azimuthal angle of arrival details of the incoming scattered signal.  This azimuthal determination, along with the range determined using the coded signal, allowed the scatter to be mapped in 2D.  A recent reconfiguration of the receiving array has allowed the elevation angle of the received signal to be calculated, providing 3D determination of the location of the plasma density irregularities.  This presentation will demonstrate the capabilities of ICEBEAR, displaying measurements of highly dynamic plasma density irregularities with wave-like behaviour on 1 second time scales.
Monitoring Seismicity on Mars - the Marsquake Service for InSight
Authors: Clinton John , Giardini Domenico , Ceylan Savas , van Driel Martin , Stähler Simon , Banerdt Bruce , Böse Maren , Charalambous Constantinos , Euchner Fabian , Horleston Anna , Kawamura Taichi , Garcia Raphael , Kedar Sharon , Khan Amir , Lognonnne Philippe , Mainsant Guenole , Panning Mark , Pike Tom , Scholz John-Robert , Smrekar Sue ,   ERP Gurus
Published: March 2020

InSight landed on Mars in late November 2018, and the SEIS seismometer package was fully deployed by February 2019. By January 2020, SEIS continues to exceed performance expectations in terms of observed minimum noise. The Marsquake Service (MQS) has been setup to create and curate a seismicity catalogue for Mars over the lifetime of the InSight mission. Seismic waveforms are downloaded daily from the station and are analysed and processed by the MarsQuake Service, with the goal of detecting seismic vibrations not due to local ambient sources. To this end, every precaution is applied to eliminate possible non-seismic sources, such as noise induced by atmospheric phenomena, lander vibrations and orbiter activity. At the date of submission, we have detected 365 events, of different quality and SNR levels. Signal amplitudes remain small and signal can generally only be detected at night. Some events show only low-frequency waves in the 1-10 sec band, others have a high-frequency content up to several Hz, and others have a more broad-band character. A special class of events involves the excitation of a very prominent ambient vibration at 2.4Hz. Despite the scattered nature of the energy, in many cases, distinct phases can be inferred in the waveforms. Body wave character, and back-azimuth, can only be confirmed for 3 broadband events so far.  The MQS approach for determining distances from broadband events identifies phases as mantle P and S-phases and uses an a priori set of several thousand martian models, derived from geophysical, mineralogical and orbital constraints. High frequency events are currently located assuming phases are trapped crustal Pg and Sg and using a simple crustal layer. The MQS works in conjunction with the Mars Structural Service (MSS) on building and adopting updated models. The MQS consists of an international team of seismologists that screen incoming data to identify and characterise any seismicity. In this presentation, we present the MQS, demonstrate how we detect and characterise marsquakes, and describe the challenges we face dealing with the Martian dataset.
Study of Intra-plate Movement in the Indian Subcontinent along Narmada Son Lineament by Baseline Processing
Authors: Dhar Sujata , Balasubramanian Nagarajan , Dikshit Onkar
Published: March 2020

India extends from 8° 4’ N to 37° 6’ N latitude and 68° 7’ E to 97° 25’ E longitude. It lies largely on the Indian plate. Major earthquakes generally happen along tectonic plate boundaries. But, Indian subcontinent has experienced some of the largest earthquakes, with magnitude more than 7, within it. This directs the possibility of significant intraplate movement in the Indian plate. Narmada river flows through the central part of India and is considered as the boundary between northern and southern India. It is tectonically active, which is not found in other river basins. Geophysical studies in the Son Narmada Fault (SNF) zone reveal that this is a zone of intense deep-seated faulting which has been reactivated and hence, this is the cause of major earthquakes and various tectonically induced landforms in that region recently. Estimates of intraplate strain across Narmada Son Lineament (NSL) from early campaign-mode GPS data and geological studies suggested movement of 2-3 mm per year. The Indian Plate is currently moving northeast at 5 cm/year, while the Eurasian Plate is moving northeast at only 2 cm/yr. Most of the research has been done with geological studies to determine the rate of the movement along NSL. We are considering Global Navigation Satellite System (GNSS) data for around 16 continuously operating and well distributed sites in India. We are using BERNESE and GAMIT software’s for GNSS data processing. Both are scientific GNSS processing software with single differencing for ambiguity resolution. This is the first time in India that movement across NSL, with ITRF14 reference frame, will be determined from any space geodetic technique dominantly. In this study, several continuous GNSS stations in India along with nearby IGS sites from 2013 to 2018 are used to examine the distribution and magnitude of intraplate movement across the active SNF.

Keywords: Indian plate, Son Narmada Fault, GNSS, BERNESE, GAMIT, ITRF14
Modelling lake-groundwater interactions in preparation of future SWOT mission: the case of the gravel pit lakes in the Seine River alluvial plain, France.
Authors: Jost Anne , Verbeke Thomas , Ottlé Catherine , Flipo Nicolas , Wang Shuaitao , Colleoni François , Bernus Anthony , Rivière Agnès
Published: March 2020

Gravel pit lakes created by sand and gravel mining are structural landscape elements in alluvial plains. As they create openings through the aquifer, they provide direct access to groundwater and make it possible for remote sensing to offer an integrated vision of water resources at the alluvial plain scale. Indeed the Surface Water and Ocean Topography (SWOT) satellite mission will soon map near weekly the surface water elevation of reservoirs with areal extent greater than 6 ha. Using the CNES large scale simulator, we evaluated the SWOT water level errors on gravel pits in La Bassée alluvial plain, in the middle reach of the Seine River (France). Despite their rather small size, the elevation accuracy over the artificial lakes should be centimetric. Using as input in-situ lake level measurements, SWOT-like outputs were generated. The full exploitation of these data requires a modelling tool for gravel pit lake simulation, which includes groundwater interaction. We also present the development of our lake module, imbedded in the CaWaQS platform, its validation using benchmark test problems and numerical experiments illustrating its performance in simulating gravel pit lake stage fluctuations.
Crustal structure of the Barents Sea from 3D active seismic tomography.
Authors: Shulgin Alexey , Lie Jan Erik , Nilsen Espen Harris , Faleide Jan Inge , Planke Sverre
Published: March 2020

The Barents Sea shelf has been covered by numerous wide-angle seismic profiles aiming to resolve the crustal structure of the shelf. However, the overall structural architecture of the crystalline crust is still not fully understood, due to limited and sparse distribution of deep-sampling seismic profiles. 

The petroleum related seismic exploration in Norwegian waters has been ongoing for decades. The recent increase of the seismic broadband stations onshore (including temporal deployments) provokes the idea to use these stations and the active seismic sources from the regional seismic reflection surveys, including academic and industry seismic projects, to reveal the crustal-scale structure of the western Barents Sea.

We have analyzed seismic records from 8 permanent seismic stations from Norway, Sweden and Finland, and 12 temporally deployed broadband seismic stations from the ScanArray seismic network, which recorded more than 100’000 marine airgun shots from academic and oil industry campaigns in the south-western quarter of the Barents Sea.

The overall quality of the seismic records is exceptionally good. We observe clear phases recorded from offsets reaching 750 km. The identified phases include refracted crustal and mantle arrivals as well as Moho reflections, including both P and S waves. The overall quantity, quality, and the geometry of the seismic data makes it perfect for the application of the 3D joint refraction/reflection travel time seismic tomography to study the crustal structure of the Barents Sea. In this work we would like to present our first results from the 3D seismic tomography.
A detailed study of the initiation process of a small (Mw4.4) normal fault earthquake in the middle lower crust
Authors: Sanchez-Reyes Hugo , Essing David , Beauce Eric , Poli Piero
Published: March 2020

Our knowledge about the physics behind the initiation process of large or small earthquakes remains limited. The current understanding of this process suggests that an earthquake occurs when increasing stress causes a pre-existing fault to fail suddenly (e.g. Dieterich 1992). Models such as the pre-slip instability growth or the triggered cascade of events have been proposed in order to theoretically explain this preparation stage (Dodge and Beroza, 1996; Ellsworth and Bullut, 2018; Bouchon et al., 2011). However, the mechanisms behind this process are still unknown. This debate is mainly due to the lack of direct observations of the subsurface shear stress evolution at the area of interest before and after an earthquake.

Considering that the shear stress evolves through time until the moment of failure, indirect observations of this change might be available but hidden inside the continuous seismic data. In this work, we analyze in detail the evolution of the seismic activity of a small (Mw 4.4) normal fault earthquake which occurred in Central Italy on 7th November 2019 at the middle lower crust (16 km depth). We first analyze the available continuous data using the Fast Matched Filter (Beauc\'e et al., 2017). Then, every new detected event is spatially localized with respect to the other events through the Double Difference algorithm (DD). As a result, we obtain the spatio-temporal evolution of the foreshock and aftershock sequences of that event.

The results from this analysis shed light on the patterns that the shear-stress spatio-temporal evolution follows before and after a given event. Therefore, we expect that this study will contribute to improve our understanding of the physics behind the earthquake initiation process.
Orbital CO2 cycles and the Mid-Pleistocene Transition
Authors: Chalk Thomas , Hain Mathis , Foster Gavin , Nuber Sophie , Rohling Eelco , Barker Stephen , Cherry Soraya , Wilson Paul
Published: March 2020

Over the past 1.5 million years, Earth’s climate has shifted from a predominantly 41 thousand year (kyr) dominated climate cycle to one dominated by longer and larger glacial-interglacial cycles, known as the Mid-Pleistocene Transition (MPT). The MPT occurs over a period of several hundreds of thousands of years, with little change to Earth’s external orbital forcing, thus implicating internal climate feedbacks. Here we interrogate the current capacity, and future potential, of boron isotope records to provide high quality carbon cycle information for the Pleistocene. We also present a compilation of boron isotope-derived pH-CO2 records from low-latitude ocean drill cores which closely follow the evolution of atmospheric CO2 over the ice core interval but extend it to 1.5 million years ago with a resolution of up to ~1 sample per 3 kyr. This new, near continuous δ11B-derived CO2 record is compared against other independent CO2 data from blue-ice cores and records of ocean and climate change., This confirms there is a decline in mean CO2 across the MPT which manifests as a lengthening and deepening of glacial CO2, and highlights the distinct difference in the nature of CO2 cycles in the 41-kyr world.

 
Gravity Field Estimation from GRACE Follow-On Data: Results from CSR Analyses
Authors: Bettadpur Srinivas , Save Himanshu , Nagel Peter , Pie Nadège , Poole Steven , Kang Zhigui , Wang Furun
Published: March 2020

At the time of presentation, nearly two years of flight data from the joint NASA/GFZ GRACE Folllow-On mission will have been collected. In this time, gravity field models have been produced using two independent inter-satellite tracking systems - the MWI and the LRI using radio and optical interferometry, respectively. The data have been analyzed over more than two complete cycles of the sun relative to the orbit plane, allowing a characterization of the environmental impacts on the flight data. Extended duration of analyses have also permitted an assessment of the GRACE-FO data relative to the corresponding GRACE data.

This poster presents the status and lessons learned from two years of estimation of Earth gravity field models from the GRACE-FO data at the science data system component at the University of Texas Center for Space Research.
Effects of the sea state in the momentum flux over the ocean atmosphere interface
Authors: Larios Diego , Ocampo-Torres Francisco J. , Osuna Pedro
Published: March 2020

The sea surface wind stress is relevant in processes of different scales of space and time such as the exchange of gases and heat, the surface currents, the depth of the mixed layer, the turbulence injection into the ocean. The wind waves are the key component in the coupling of the lower layer of the the atmosphere and the surface layer of the ocean, and various studies have shown the direct and indirect effects on the surface wind stress. In the present study, we present the measurements of the momentum flux and the results meteorological variables at the interface between the ocean and the atmosphere, by using and Oceanographic and Marine Meteorology Buoy (BOMM1) between November 2017 and February 2018. The analysis of the results during moderate wind conditions (U10N > 8 ms-1) in which mixed sea state conditions occur (swell that interacts with locally generated wind waves) we found a decrease of the roughness length (z0), related to developing waves with higher steepness (ak), the data suggest that the presence of swell alters the wind sea part of the spectrum, which leads a reduction of the energy level of the wind-generated waves, hence reducing the wind sea associated roughness. For well developed waves conditions, the roughness length is greater than the parametrization proposed by Drennan al., (2003) for pure wind sea conditions, the data suggest that this is due direct interaction of the wind airflow and swell with higher steepness.  The data of this work suggests that during these conditions (U10N > 8 ms-1) , the mechanism of reduction of the drag of the wind sea due to the presence of swell, and the increase of the wind stress by direct interaction of swell with the airflow causes the net effect of wave field to behave as expected under pure wind sea conditions, and there seems to be no swell effect.