bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetic mirror structures associated with magnetopause flux ropes investigated with Mangnetospheric Multiscale misson (MMS)
Authors: Robertson Sadie , Eastwood Jonathan , Stawarz Julia , Hietala Heli , Phan Tai , Lavraud Benoit , Burch James , Giles Barbra , Gershman Daniel , Torbert Roy , Lindqvist Per Arne , Ergun Robert , Russell Christopher , Strangeway Robert
Published: March 2020

Magnetic reconnection is a fundamental plasma physics process which governs energy and mass transfer from the solar wind into the Earth’s magnetosphere. Electron acceleration during reconnection has been widely investigated with multiple mechanisms proposed. Many of these mechanisms involve flux ropes: twisted magnetic field structures formed during reconnection. Drake et al. 2006 suggest that contracting magnetic islands (or flux ropes in 3D) could trap and energise electrons by a Fermi acceleration process.

Whilst previous missions have observed and characterised flux ropes, the temporal resolution of the data was typically not great enough to study structures in detail, particularly on electron scales. Here we investigate magnetopause flux ropes using data from NASA’s four spacecraft Magnetospheric Multiscale mission (MMS). MMS measures the thermal electron and ion 3D distribution at 30 msec and 150 msec time resolution, respectively, and at spacecraft separations down to a few kilometers.

We focus on electron pitch angle distributions and examine how they can be used to investigate magnetopause flux ropes. In particular, the distributions are used to identify electron trapping in magnetic mirror structures on the magnetospheric edge of the flux ropes. These features are found to have extended 3D structure along the body of the flux rope. We evaluate possible formation mechanisms, such as the mirror instability, and potential electron acceleration mechanisms, such as betatron and Fermi acceleration. Magnetic mirror structures could represent an important particle acceleration feature for flux ropes and magnetic reconnection.
An Integrated Feasibility Study of Reservoir Thermal Energy Storage in Portland, OR, USA
Authors: Bershaw John , Burns Erick R. , Cladouhos Trenton T. , Horst Alison E. , Van Houten Boz , Hulseman Peter , Kane Alisa , Liu Jenny H. , Perkins Robert B. , Scanlon Darby P. , Streig Ashley R. , Svadlenak Ellen E. , Uddenberg Matt W. , Wells Ray E. , Williams Colin F.
Published: March 2020

In regions with long cold overcast winters and sunny summers, Deep Direct-Use (DDU) can be coupled with Reservoir Thermal Energy Storage (RTES) technology to take advantage of pre-existing subsurface permeability and storage capacity to save summer heat for later use during cold seasons. Many aquifers worldwide are underlain by permeable regions (reservoirs) containing brackish or saline groundwater that has limited beneficial use due to poor water quality. We investigate the utility of these relatively deep, slow flowing reservoirs for RTES by conducting an integrated feasibility study in the Portland Basin, Oregon, USA, developing methods and obtaining results that can be widely applied to groundwater systems elsewhere. As a case study, we have conducted an economic and social cost-benefit analysis for the Oregon Health and Science University (OHSU), a teaching hospital that is recognized as critical infrastructure in the Portland Metropolitan Area. Our investigation covers key factors that influence feasibility including 1) the geologic framework, 2) hydrogeologic and thermal conditions, 3) capital and maintenance costs, 4) the regulatory framework, and 5) operational risks. By pairing a model of building seasonal heat demand with an integrated model of RTES resource supply, we determine that the most important factors that influence RTES efficacy in the study area are operational schedule, well spacing, the amount of summer heat stored (in our model, a function of solar array size), and longevity of the system. Generally, heat recovery efficiency increases as the reservoir and surrounding rocks warm, making RTES more economical with time. Selecting a base-case scenario, we estimate a levelized cost of heat (LCOH) to compare with other sources of heating available to OHSU and find that it is comparable to unsubsidized solar and nuclear, but more expensive than natural gas. Additional benefits of RTES include energy resiliency in the event that conventional energy supplies are disrupted (e.g., natural disaster) and a reduction in fossil fuel consumption, resulting in a smaller carbon footprint. Key risks include reservoir heterogeneity and a possible reduction in permeability through time due to scaling (mineral precipitation). Lastly, a map of thermal energy storage capacity for the Portland Basin yields a total of 87,000 GWh, suggesting tremendous potential for RTES in the Portland Metropolitan Area.
Efficiency assessment of seismological information, monitoring system and seismicity study for the Republic of Armenia
Authors: Karapetyan Jon , Ghazaryan Karlen , Sargsyan Rudolf , Karapetyan Roza
Published: March 2020

To study the deep structure of the earth it is important to have an optimal monitoring network and reliable seismic baseline database for the investigated area. In addition, the territory of Armenia according to its geology and seismological conditions is a full-scale experimental polygon for seismic problems, in particular the study of Earth's deepest structure by seismic methods. For this purpose, the work aims to assess the effectiveness of the existing seismic monitoring system in Armenia, to offer optimal solutions for the station layout, to evaluate the accuracy of seismic information registered in the RA by performing hypocenter recalculation. Then, within of the work organized modern seismic stations in Armenia and Russia towns with seismic equipment made and produced in Armenia (IGES NAS RA). The work was supported by MESCS Science Committee of the Republic of Armenia (grant № 18SH-1E012).
Single vs. concurrent extreme events: Economic resonance of weather extremes increases impact on societal welfare loss
Authors: Kuhla Kilian , Willner Sven , Otto Christian , Geiger Tobias , Levermann Anders
Published: March 2020

Weather extremes such as heat waves, tropical cyclones and river floods are likely to intensify with increasing global mean temperature. In a globally connected supply and trade network such extreme weather events cause economic shocks that may interfere with each other potentially amplifying their overall economic impact.

Here we analyze the economic resonance of concurrent extreme events, that is the overlapping of economic response dynamics of more than one extreme event category both spatially and temporally. In our analysis we focus on the event categories heat stress, river floods and tropical cyclones. We simulate the regional (direct) and global (indirect via supply chains) economic losses and gains for each extreme event category individually as well as for their concurrent occurrence for the next two decades. Thus we compare the outcome of the sum of the three single simulations to the outcome of the concurrent simulation. Here we show that the global welfare loss due to concurrent weather extremes is increased by more than 17% due to market effects compared to the summation of the losses of each single event category. Overall, this economic resonance yields a non-linearly enhanced price effect, which leads to a stronger economic impact. As well as a highly heterogeneous distribution of the amplification of regional welfare losses among countries.

Our analysis is based on the climate models of the CMIP5 ensemble which have been bias-corrected within the ISIMIP2b project towards an observation-based data set using a trend-preserving method. From these we use RCP2.6 and 6.0 for future climate projections. We transfer the three extreme weather event categories to a daily, regional and sectoral production failure. Our agent-based dynamic economic loss-propagation model Acclimate then uses these local production failures to compute the immediate response dynamics within the global supply chain as well as the subsequent trade adjustments. The Acclimate model thereby depicts a highly interconnected network of firms and consumers, which maximize their profits by choosing the optimal production level and corresponding upstream demand as well as the optimal distribution of this demand among its suppliers; transport and storage inventories act as buffers for supply shocks. The model accounts for local price changes, and supply and demand mismatches are resolved explicitly over time.

Our results suggest that economic impacts of weather extremes are larger than can be derived from conventional single event analysis. Consequently the societal cost of climate change are likely to be underestimated in studies focusing on single extreme categories.
Using neural networks for postprocessing of numerical weather predictions in complex terrain
Authors: Bhend Jonas , Spirig Christoph , Hürlimann Max , Moret Lionel , Liniger Mark
Published: March 2020

Weather forecasts have been steadily improving in quality over the last decades. These ongoing improvements are due to advances in numerical weather prediction (NWP) and the advent of ever more powerful supercomputers that allow simulating future weather and its uncertainty with increasing resolution and using ensemble approaches. Such physics-based computer models, however, are not free of systematic errors. Statistical postprocessing can be used to calibrate NWP forecasts to further improve forecast quality and better exploit the available information. Here we present results from several explorative deep learning studies using artificial neural networks (ANN) to calibrate high resolution forecasts of temperature, precipitation, wind, and cloud cover in Switzerland. These first attempts at ANN-based postprocessing help us to understand the strengths and weaknesses of machine learning and are the basis to build more complex and comprehensive statistical models accounting for local effects in complex terrain such as the Swiss Alps. In all cases, ANN leads to significant improvements over the direct NWP output. While the improvement is comparable in magnitude with improvements achieved with conventional postprocessing approaches, ANN-based postprocessing is easier to generalize in space for a calibration of forecasts also at unobserved sites. In addition to the results of the postprocessing, we will also discuss the lessons learned so far in using machine learning for this particular problem.
Modelling the dielectric properties of the geyser deposited snow layer on Enceladus
Authors: Friend Pia , Kyriacou Alexander , Helbing Klaus
Published: March 2020

Saturn’s icy moon Enceladus is with its roughly 500 km diameter a differentiated geological active body that harbours a liquid ocean between its rocky core and icy mantle. This ocean is among the most promising places to host extraterrestrial life in our solar system.

At Enceladus’ south pole terrain, active geysers form a passage from the ocean to the surface; erupting ice, dust and gas particles. Most of those particles escape the moon’s gravity, but some portion falls back to the surface. Considering the current output, about 10 m of snow gets sedimented at a distance of about 100 m away from the geyseres within 105-106 years. Hence, depending on the timescale the geysers are active at the same location, the snow layer would have a thickness of some km already, assuming no densification.

A first model of the density profile of the snow layer as a function of the ice/vacuum ratio will be provided at the conference. To investigate the density at the surface, mainly the distribution of the ice grain shapes and the grain sizes have to be considered and put into a state equation. For modelling the density change in respect to the depth, also the pressure from the overlying weight has to be accounted for. As temperatures at Enceladus’ surface are too low, neither sintering nor processes such as melting and re-freezing can thereby contribute to densification. These processes however are acting in terrestrial glaciers. We propose therefore, because the temperatures on Enceladus are far below the melting point of ice, to consider the ice grains on Enceladus rather as sand than as snow in respect to these materials on Earth, when modelling the density within the snow layer.

After obtaining the ratio between ice and vacuum, it is possible to define the dielectric properties of the snow layer. The dielectric profile in turn is the primary diagnostic property for radar based geophysical investigation. It determines the velocity of radio waves in a medium as well as their reflection and refraction at interfaces.
Because of the above mentioned possibility that primitive extraterrestrial life might exist in Enceladus’  hidden ocean, there will likely be future space missions with the aim to reach a water reservoir and probe it. A well-defined density profile could then help to radar navigate a melting probe through the ice.

 
The effects of wind and waves on in-situ surface drift in the Baltic Sea
Authors: Delpeche-Ellmann Nicole , Giudici Andrea , Soomere Tarmo
Published: March 2020

Wind and waves often have a strong influence on surface drift, especially in the strongly stratified Baltic Sea. However due to the limitations of wave models and analytical solutions, the quantification of the influence of the waves is a complicated problem. In this study we employ a more observational approach by utilizing one of the longest time series of in-situ surface drifters deployed in the Gulf of Finland, Baltic Sea for the period of 2011−2019. Analysis is performed both qualitatively and quantitatively to understand the effects of the wind and waves on surface drift. The forty-seven in-situ surface drifters utilized were designed to follow the uppermost 2 m layer of currents. In addition, a web-based software (DrifterTrack) was specifically developed for real time data monitoring, data collection, storage and access solution. The wind and wave data were obtained by wave buoys and meteorological stations located in the central part of the gulf.  
Several hypothesis tests combined with statistical analysis of drifter trajectories, wind and wave data were utilized for the analysis. Qualitatively the drifter trajectories displayed a variety of shapes and maneuvers, hinting the complexity of the surface drift. Nevertheless, drifter trajectory maps showed for most years a predominance of surface drift towards the east which also coincides with the predominant wind and wave direction. Interestingly the results also suggest that when surface drift towards the west occurred it was generally quicker than the drift to the east. The average current speed was in the range of 0.05−0.15 m/s for approximately 45% of the occurrences. The drifter speed within the range of 0.3−0.5 m/s accounted for approximately 9% of the occurrences. The drifter speed was found to vary between 1.5−2.5 % of the wind speed. Hypothesis tests show that wave heights of >1 m (created by >10 m/s wind speed) have the most significant effect on the drifter speed within the range of 0.15−0.3 m/s. These tests also demonstrated that wind and waves effects are not the only forces influencing strong surface drift in the gulf. Several other processes (e.g. eddies, density gradients, upwellings, downwellings etc.) can substantially contribute to the surface drift.
Rapid and Precise Carbon Dioxide Clumped Isotope Composition Analysis by Tunable Infrared Laser Differential Absorption Spectroscopy
Authors: Nelson David , Wang Zhennan , Dettman David , McManus Barry , Quade Jay , Yanay Nitzan , Huntington Katharine , Schauer Andrew
Published: March 2020

Carbon dioxide clumped isotope thermometry is one of the most developed applications of the geochemistry of multiply substituted isotopologues. The degree of heavy isotope clumping (e.g., 16O13C18O) beyond an expected random distribution can be related to the temperature of calcite precipitation. This provides an independent temperature estimate that, when combined with carbonate δ18O values, can constrain paleowater δ18O values. However, the use of isotope ratio mass spectrometry (IRMS) to do these measurements remains relatively rare because it is time-consuming and costly. We have developed an isotope ratio laser spectrometry method using tunable infrared laser differential absorption spectroscopy (TILDAS) and describe our latest results using both gaseous carbon dioxide samples and CO2 derived from carbonate minerals. The TILDAS instrument has two continuous wave lasers to directly and simultaneously measure four isotopologues involved in the 16O13C18O equilibrium calculation. Because each isotopologue is independently resolved, this approach does not have to correct for isobaric peaks. The gas samples are trapped in a low volume (~250 ml) optical multi-pass cell with a path length of 36 meters. Raw data are collected at 1.6 kHz, providing 96,000 peak-area measurements of each CO2 isotopologue per minute. With a specially designed sampling system, each sample measurement is bracketed with measurements of a working reference gas, and a precision of 0.01‰ is achieved within 20 minutes, based on four repeated measurements. The total sample size needed for a complete measurement is approximately 15 μmol of CO2, or 1.5 mg of calcite equivalent. TILDAS reported ∆16O13C18O values show a linear relationship with theoretical calculations, with a very weak dependence on bulk isotope composition. The performance of the TILDAS system demonstrated in this study is competitive with the best IRMS systems and surpasses typical IRMS measurements in several key respects, such as measurement duration and isobaric interference problems. This method can easily be applied more widely in stable isotope geochemistry by changing spectral regions and laser configurations, leading to rapid and high precision (0.01‰) measurement of conventional stable isotope ratios and δ17O in CO2 gas samples.
MMS Observations of Ion Cyclotron Waves in the Solar Wind
Authors: Wei Hanying , Jian Lan , Gershman Daniel , Russell Christopher
Published: March 2020

Although electromagnetic ion cyclotron waves (ICWs) have been observed in the solar wind by multiple missions at heliocentric distances from 0.3 to 1 AU, there are still open questions on the generation mechanisms for these waves. Detailed analysis of the plasma distribution is needed to examine whether these waves are possibly generated locally.

In the solar wind, there are mainly three types of ion-driven instabilities responsible for parallel-propagating ICWs: ion cyclotron instabilities driven by ion component with temperature anisotropies greater than 1, parallel firehose instabilities driven by ion temperature anisotropies smaller than 1, and ion/ion magnetosonic instabilities driven by the relative drift between two ion components. In the solar wind frame, the waves due to ion cyclotron instability have left-handed polarization, while the waves due to firehose and ion/ion magnetosonic instabilities have right-handed polarization. Depending on the wave propagation parallel or anti-parallel to the magnetic field, the wave frequencies in the spacecraft frame are Doppler shifted higher or lower even with reversed handness. With the plasma data from Magnetospheric Multiscale (MMS) mission, we can examine the possible unstable mode with dispersion analysis and check if the prediction agrees with the observed wave mode. If the plasma measurements of the local solar wind do not support the wave growth, the waves could be possibly generated remotely close to the Sun and propagate away from the source region and are also carried outward by the solar wind flow. If these waves are generated remotely closer to the Sun, the wave properties at different heliocentric distances would help us better understand their sources.

The MMS spacecraft spends long periods of its orbit in the “pristine” solar wind starting end of 2017. From the 2017 December data we find over a hundred events and 42 of them last longer than 10 minutes which are called ICW storm events, and the longest event captured lasted over 2 hours. Although only about 17 of them have the plasma data available, we can perform case studies on these events first to investigate the wave properties and possible plasma instabilities, which will help us investigate the wave generation mechanisms due to local or remote sources.
Detecting Greenland Melt with the SMAP L-band Radiometer
Authors: Colliander Andreas , Mousavi Mohammad , Miller Julie , Entekhabi Dara , Johnson Joel , Shuman Christopher , Courville Zoe , Kimball John
Published: March 2020

Complex processes within the ice govern and record the evolution of the Greenland Ice Sheet. Low frequency microwave measurements have been used to gain insight into what happens deep inside the ice for some time now. NASA’s SMAP mission offers a valuable additional set of observations. SMAP covers virtually the entire ice sheet twice a day with its L-band radiometer. The overpasses center on morning and evening hours as the satellite is on a 6 AM/6PM equator-crossing orbit, and the spatial resolution of the instrument is about 40 km.

In this study, we investigated the response of L-band (1.4 GHz) measurements to surface melting of the ice sheet from the 2015 through 2019 melt seasons. The changes in brightness temperature caused by surface melt differs in the ablation zone, the active melt areas, and the interior’s dry snow zone. The melt area can be tracked with SMAP when accounting for these differences. SMAP’s frequent revisit time enables tracking of the melt events with comparatively high temporal fidelity. The evolution of the seasonal melt area derived from SMAP is consistent with other methods used for tracking ice sheet melt area.

Most notably, Greenland experienced an unusually strong melt event at the end of July 2019, which extended the melt area to the dry snow zone of the ice sheet over a period of two days. In-situ temperatures measured at Greenland’s Summit station show above-freezing temperatures during this event, and subsequent in-situ ice analyses have revealed ice structure changes associated with melt on these dates and subsequent refreezing. SMAP was able to record the extent of this unusual melt event on both days, and to show the anomalous extent of the melt event compared to the past 4 years of operational measurements.

This presentation will discuss the SMAP signal sensitivity to ice structure changes, the seasonal melt extent evolution and its inter-annual variation, and the comparison of the results to other data sources.
Shallow Asthenospheric Volumes in the Circum-Mediterranean and their Relation to Intraplate Volcanism and Topography
Authors: Meier Thomas , El-Sharkawy Amr , Lebedev Sergei , Behrmann Jan
Published: March 2020

Based on a high-resolution Rayleigh-wave tomography of the Mediterranean region, shallow asthenospheric volumes are identified characterized by low S-wave velocities between about 70 km and 250 km depth. We distinguish between five major shallow asthenospheric volumes in the Circum-Mediterranean: the Middle East, the Anatolian-Aegean, the Pannonian, the Central European, and the Western Mediterranean Asthenospheres. Remarkably, they form an almost closed circular belt of asthenospheres interrupted only by thick Triassic oceanic lithosphere in the eastern Mediterranean. Shallow asthenosphere beneath the Rhone and Rhine Grabens connects the Western Mediterranean with the Central European Asthenosphere. Beneath the Serbian and Rhodope Mountains shallow asthenosphere forms a link between the Pannonian and the Anatolian-Aegean Asthenosphere.

Cenozoic intraplate volcanic fields are found above all areas underlain by shallow asthenosphere, and is absent in areas of thick lithosphere. Thus, anorogenic intraplate volcanism in the circum-Mediterranean appears to be associated with shallow asthenospheric volumes. Specifically, this applies to volcanic fields in the central Apennines and Sicily underlain by the Western Mediterranean Asthenosphere. Regions without significant tectonic extension above shallow asthenosphere are characterized by elevated topography. Examples are the Anatolian Plateau, the Western Carpathians, the Atlas Mountains and the low mountain ranges in Central Europe and Iberia. In back-arc regions like the Aegean and Pannonian Basins, and the western Mediterranean, strong tectonic extension leads to low topography above shallow asthenosphere. High continental shoulders are present in transition regions towards thinner lithosphere. Examples are the Levantine coast, the Moesian platform and the Bohemian Massif or the southern Atlas Mountains. We further note that in regions of past volcanism continental lithosphere is thickening by long-term cooling. The showcase for this is the North-German Basin where sedimentation and an about 100 km thick lithosphere developed after extensive Permian volcanism. These observations hint at considerable  variability in time of the continental lithosphere-asthenosphere boundary: Thinning of continental lithosphere may be caused by extension and/or thermal erosion whereas cooling may lead to thickening of continental lithosphere as is evident from the Mesozoic evolution of continental lithosphere in central Europe.  

 
Thermal behavior of polyhalite: A combined high-temperature synchrotron XRD and calorimetric study
Authors: Hongwu Xu , Xiaofeng Guo
Published: March 2020

As an accessory mineral in marine evaporites, polyhalite, K2MgCa2(SO4)4·2H2O, coexists with halite (NaCl) in salt formations, which have been considered as potential repositories for permanent storage of high-level nuclear wastes. However, because of the heat generated by radioactive decays in the wastes, polyhalite may dehydrate, and the released water will dissolve its neighboring salt, potentially affecting the repository integrity. Thus, studying the thermal behavior of polyhalite is important. In this work, a polyhalite sample containing a small amount of halite was collected from the Salado formation at the WIPP site in Carlsbad, New Mexico. To characterize its thermal behavior, in situ high-temperature synchrotron X-ray diffraction was conducted from room temperature to 1066 K with the sample powders sealed in a silica-glass capillary. At ~506 K, polyhalite started to decompose into water vapor, anhydrite (CaSO4) and two langbeinite-type phases, K2CaxMg2-x(SO4)3, with different Ca/Mg ratios. XRD peaks of the minor halite disappeared, presumably due to its dissolution by water vapor. With further increasing temperature, the two langbeinite solid solution phases displayed complex variations in crystallinity, composition and their molar ratio and then were combined into the single-phase triple salt, K2CaMg(SO4)3, at ~919 K. Rietveld analyses of the XRD data allowed determination of structural parameters of polyhalite and its decomposed anhydrite and langbeinite phases as a function of temperature. From the results, the thermal expansion coefficients of these phases have been derived, and the structural mechanisms of their thermal behavior been discussed. In addition, to determine stability relations, standard enthalpies of formation of polyhalite from constituent oxides and elements were measured using high-temperature oxide-melt drop-solution calorimetry.
GNSS-based remote sensing: Innovative observation of key hydrological parameters in the Central Andes
Authors: Antonoglou Nikolaos , Bookhagen Bodo , Dadamia Danilo , de la Torre Alejandro , Wickert Jens
Published: March 2020

The Central Andes are characterized by a steep climatic and environmental gradient with large spatial and temporal variations of associated hydrological parameters. In this region, important hydrological components are integrated water vapor (IWV) and soil moisture. Both parameters can be monitored in parallel by using Global Navigation Satellite System - Reflectometry (GNSS-R) techniques. Soil moisture can furthermore be estimated using Synthetic Aperture Radar (SAR) data.

As part of International Research Training Group-StRATEGy project, our research aims at monitoring IWV and soil moisture with new station data in the Central Andes. According to the needs of the research, four independent GNSS ground stations and in-situ soil-moisture sensors were installed in spring 2019. Each station is located at different altitude along the climatic gradient and contains various quality GNSS receivers. It has been shown that high-quality receivers provide precise measurements, while low-quality receivers have not been widely tested for these applications. A goal of this project is the direct comparison of data quality from each site and receiver type. Additionally, soil moisture sensors were installed at each site. This set-up will help to evaluate the quality of the GNSS receivers. Moreover, the GNSS-based remote sensing approaches are directly compared to traditional Time-Domain Reflectometry (TDR) techniques. Meteorological data are used for studying the relation between the magnitude of precipitation events and soil moisture, as well as the time needed to spot a significant change in soil moisture after a precipitation event.

GNSS-R soil moisture estimations and in-situ measurements were compared with estimations derived from SAR data. More specifically, we used data from Sentinel-1 and Satélite Argentino de Observación COn Microondas (SAOCOM) missions. Sentinel-1 is a fully operational mission that uses C-band wavelengths, while SAOCOM relies on L-band wavelength, but is still in a calibration phase. We analyze both wavelengths and estimate the potential for soil-moisture measurements in the Argentinean Andes.
Understanding the regional submarine groundwater discharge and the associated nutrient inputs - an assessment from the southwest coast of India
Authors: Ramasamy Murugan , Babu Suresh , Srinivas Reji
Published: March 2020

Submarine groundwater discharge (SGD) is a possible source for nutrients and anthropogenic pollutants that flow from the land to the ocean. The coastal zone of southwest (SW) India is capped with Tertiary sandstone-limestone-clay intercalations, Quaternary sediments, and laterites up to 600 m thickness above bedrock, which are considered as productive aquifer belts. The signatures of freshwater discharge to sea are not entirely vivid on the SW coast of India due to different constraints on investigation techniques and coastal dynamics. Hence, an onshore and offshore sampling and monitoring were carried out from Kanyakumari to Mangalore (∼640 km) along the SW coast of India to understand the groundwater discharge from the coastal aquifer system. The combined techniques used make it possible to identify groundwater outflows using satellite thermal infrared images to monitor physico-chemical anomalies in the sea (from 7 October – 5 November 2019 onboard the Sakar Kanya research vessel). Surface-to-bottom CTD (conductivity, temperature, depth) profiling and sampling of radium and nutrients were performed during fieldwork. The conventional water balance method and radium isotopic analyses were used to quantify the SGD. The findings of the water balance method show that the average of all fresh SGD is 790 m3/y/m with a minimum of 72 m3/y/m and a maximum of 2070 m3/y/m exported by SW coast to the sea. Regional precipitation patterns and coastal drainage geometry control local variation in fresh SGD. Nutrient concentrations have apparently followed conservative and non-concentrative mixing between fresh, high nutrient groundwater and saline, low-nutrient seawater at coastal ocean sites. Further investigations are in progress for flux estimation using radium isotopes in offshore and deployment of seepage meters in specific known areas along the shore.
Integrated regional scale view of Milos submarine hydrothermalism
Authors: Puzenat Valentine , Martelat Jean-Emmanuel , Escartin Javier , Barreyre Thibaut , Gracias Nuno , Vallicrosa Guillem , Garcia Rafael , Magí Lluís , Nomikou Paraskevi , Grandjean Philippe , Allemand Pascal , Schouw Anders , Le Moine Bauer Sven , Jørgensen Steffen Leth , Antoniou Varvara , Vlasopoulos Othonas , Polymenakou Paraskevi , Mandalakis Manolis , Coskun Omer , Orsi William
Published: March 2020

Submarine hydrothermal activity is common at the flanks of volcanic islands, and in some cases, occurring at very shallow water (0-100 meter depth). These sites are a key target for systematic seafloor mapping to understand the location, geometry and nature of hydrothermal discharge. These data are also critical for monitoring the temporal variability of these dynamic systems, while providing a context for instrumental measurements, sampling and other observations (e.g., temperature of outflow, chemistry, etc.). Here we present a systematic mapping of the Milos hydrothermal system in the Hellenic volcanic Arc, characterized by submarine gas emissions, high-temperature outflow, bacterial mats, precipitation of hydrothermal minerals, and small hydrothermal constructs and edifices. We have mapped this site at regional scales using satellite imagery (World-View2 images from the DigitalGlobe foundation), complemented with aerial photography acquired with drones, and high-resolution seafloor photomosaics (<1 cm resolution) from underwater imagery acquired by the autonomous underwater vehicle Sparus II (University of Girona). 

Our drone and AUV mapping ground truths the correlation between patterns in satellite imagery and hydrothermal outflow, associated to mineral precipitates and/or bacterial mats at the seafloor. This mapping also reveals a clear organization of the hydrothermal outflow in sandy areas. In particular, polygonal patterns are common and often associated with inactive or actively bubbling pockmarks. These areas, showing white bacterial mats and hydrothermal precipitates, are rippled, suggesting that the hydrothermal precipitates do not consolidate the sediment. White precipitates display subseafloor temperatures >50°C at depths of 10 to 50 cm. The white areas are bound by bands of seafloor with a hummocky structure due to intense bioturbation, that obliterates the ripples, with widths of up to a few meters. This area shows subseafloor temperatures of 20-40°C, and corresponds to a transition from the high-temperature white zones and the seafloor with ripples and no hydrothermal precipitates. This area exhibits subseafloor temperatures similar to those of seawater, and can be associated with seagrass. These patterns reveal a clear organization of a narrowly focused hydrothermal outflow that controls the biological communities at the seafloor and subseafloor. We will discuss the implications of these observations to quantify hydrothermal fluxes in the study area.
Effects on hydrodynamics and ecological costs of climate change and tidal stream energy extraction in a shelf sea
Authors: De Dominicis Michela , Wolf Judith , Sadykova Dina , Scott Beth , Sadykov Alexander , O’Hara Murray Rory
Published: March 2020

The aim of this work is to analyse the potential impacts of tidal energy extraction on the marine environment. We wanted to put them in the broader context of the possibly greater and global ecological threat of climate change. Here, we present how very large (hypothetical) tidal stream arrays and a ''business as usual'' future climate scenario can change the hydrodynamics of a seasonally stratified shelf sea, and consequently modify ecosystem habitats and animals’ behaviour.

The Scottish Shelf Model, an unstructured grid three-dimensional ocean model, has been used to reproduce the present and the future state of the NW European continental shelf. While the marine biogeochemical model ERSEM (European Regional Seas Ecosystem Model) has been used to describe the corresponding biogeochemical conditions. Four scenarios have been modelled: present conditions and projected future climate in 2050, each with and without very large scale tidal stream arrays in Scottish Waters (UK). This allows us to evaluate the potential effect of climate change and large scale energy extraction on the hydrodynamics and biogeochemistry. We found that climate change and tidal energy extraction both act in the same direction, in terms of increasing stratification due to warming and reduced mixing, however, the effect of climate change is ten times larger. Additionally, the ecological costs and benefits of these contrasting pressures on mobile predator and prey marine species are evaluated using ecological statistical models.
Magnetostratigraphy and Carbon isotopes of Ediacaran Avellaneda Formation, Rio de La Plata Craton, Argentina
Authors: Afonso Jhon , Trindade Ricardo , Franceschinis Pablo , Rapalini Augusto
Published: March 2020

The Ediacaran Period (635-542 Ma) witnessed a series of extraordinary events. It arises with the end of the Marinoan Glaciation and deposition of worldwide enigmatic cap carbonate deposits. This abrupt shift in paleoclimatic conditions coincides with major fluctuations in the  isotope ratios of carbon and sulfur, and with significant changes in the concentration of redox-sensitive elements in marine sediments. The Ediacaran is also a period marked by rapid changes in geomagnetic polarity. Magnetostratigraphy may therefore provide high-resolution correlation between Ediacaran successions worldwide. Here, we combine stratigraphy logs, carbon isotopes and magnetostratigraphy on the Avellaneda Formation (590-560 Ma) which at the Rio La Plata Craton, eastern Argentina. We investigated two drill cores (TSE-34 and TSE-7) with a 0.3-0.7 m resolution covering the entire Avellaneda Formation, corresponding to 98 standard specimens (25 mm in diameter). The basal contact of the Avellaneda Formation with the underlying mudstone rocks from Loma Negra Formation (~ 590 Ma) is present in both cores. The upper contact with the Alicia Formation, only observed in TSE-34 core, is transitional. The TSE-7 displays an erosional contact between Avellenda and Cerro Negro Formations (~ 560 Ma). After stepwise thermal demagnetization up to 600°C, almost all samples provided a characteristic magnetization between 350°C and 600°C, therefore Ti-poor magnetite or titanohematite is likely the main carrier of the stable remanence in these rocks. A high-temperature, dual-polarity component is persistent and coherent in the two drill cores. The base of the unit is marked by normal polarity, followed by a reverse interval, followed by persistent normal polarity across to the upper part of the Avellaneda Formation. This magnetostratigraphic framework, together with the carbon isotope signal, will be compared with results recently obtained for potentially coeval successions in China, Canada and United States.
The Importance of the NAO for the ENSO - Tropical Atlantic Teleconnection
Authors: Casselman Jake , Domeisen Daniela
Published: March 2020

El Niño-Southern Oscillation (ENSO) influences the weather around the globe. These so-called ‘teleconnections’ occur on sub-seasonal-to-seasonal timescales, and can be useful for weather and climate predictions. ENSO teleconnections can reach as far as the North Atlantic-European (NAE) region, where ENSO influences remain insufficiently understood. ENSO teleconnections to the NAE region can travel through a range of different pathways, with differences in seasonality for each pathway. We here focus on determining the importance of the North Atlantic Oscillation (NAO) for establishing the connection between the tropical Pacific and the tropical Atlantic, following an ENSO event. We use reanalysis data in combination with a simplified atmospheric global circulation model with ENSO-like sea surface temperature (SST) forcing to investigate both the isolated and combined influences from these different pathways. Initial results suggest that the NAO’s influence onto the tropical Atlantic may play a minor role, as surface wind impacts are likely too far north to contribute to a wind-evaporation-SST (WES) feedback within the tropical Atlantic. Shifts in the longitudinal position of ENSO may, however, cause changes in the influence from the NAO onto the tropical Atlantic. Such changes may help in explaining the presence of significantly different spatial patterns of SST in the tropical Atlantic, following different ENSO flavors.
Soil Biogeochemical Response to Drought Conditions in the Biosphere 2 Rainforest
Authors: Shorter Joanne , Roscioli Joseph , Meredith Laura , Gil-Loaiza Juliana
Published: March 2020

The direct measurement of soil gases provides insight into the biogeochemical processes responsible for micro- and macro-nutrient cycling, respiration, signaling, and environmental responses.  The concentrations and isotopic signatures of soil gases are effective messengers of the microbial pathways active in the soil.  We have developed and deployed a high frequency sensor consisting of new diffusive soil probes coupled with a Tunable Infrared Laser Direct Absorption Spectrometer (TILDAS) to monitor a range of soil gas species to investigate biogeochemical soil processes.

An array of soil probes was deployed at the Tropical Rainforest at Biosphere 2 in Arizona as part of the Water Atmosphere and Life Dynamics (WALD) experiment in 2019-2020.  Probes were located in a root zone and nearby control area, and at several depths via a soil pit.  These probes were coupled with a TILDAS to monitor isotopologues of nitrous oxide (N2O) including 14N15NO, 15N14NO, N218O, and methane (13CH4 and 12CH4), as well as CO2. During the WALD experiment, the probe-TILDAS system followed the impact on the soil biome of a 2 month induced drought in the rainforest and the subsequent return of rain.  The high temporal resolution of the system allowed us to monitor each probe every 2 hours and thus observe changes in the composition of soil gases that reflect biogeochemical processes and pathways.  CO2 and thus respiration decreased significantly during the drought and was slow to recover.  Differences in N2O mixing ratios and isotopic signatures (both site preference and bulk 15N) in the root zone versus a controlled soil region were observed during both drought and rewetting periods.  Changes in nitrogen and carbon cycles and the microbial pathways during the induced drought and rewetting as reflected in these observations will be discussed.
Greenhouse gas emissions mitigation with alternate wetting and drying irrigation of rice agriculture
Authors: Runkle Benjamin R.K. , Adviento-Borbe Arlene , Reba Michele L. , Moreno-García Beatriz , Karki Sandhya , Iseyemi Oluwayinka , Suvočarev Kosana , Reavis Colby W. , Barr Bennett E.
Published: March 2020

Rice production contributes roughly 11% of global CH4 anthropogenic emissions while producing food for over 3 billion people. The alternate wetting and drying (AWD) irrigation practice for rice has the potential to conserve water while reducing CH4 emissions through the deliberate, periodic introduction of aerobic soil conditions. Our work in the US Mid-South rice production region has demonstrated, using the eddy covariance method on adjacent fields, that AWD can reduce field CH4 emissions by about 66% without impacting yield. In any strategy, CO2 and N2O emissions should also be monitored to take advantage of the high carbon sequestration potential of rice and low potential N2O emissions. Careful water and fertilizer management can theoretically keep N2O emissions low. All three gases should be managed together, while sustaining or improving harvest yield, to create a sustainable rice production system.

 

We now present 5 years of closed chamber measurements of N2O and CH4 and compare them to the eddy covariance measurements of CH4 and CO2 to derive a more thorough perspective on the net greenhouse gas (GHG) emissions or global warming potential basis of rice production from the highly productive, mechanized, humid, US Mid-South. Global warming potential of GHG emissions from rice systems was dominated by CH4 emissions (74 to 100%), hence mitigating efforts need to focus on CH4 emissions. Greater reduction of CH4 emissions can be achieved by proper AWD management practice combined with adequate N fertilization. We end with a comment on the upcoming challenge of how to sequester CO2 uptake as soil organic matter via litter incorporation without increasing CH4 emissions. 
A textural approach to snow depth distribution on Antarctic sea ice
Authors: Mei M. Jeffrey , Maksym Ted
Published: March 2020

Understanding the distribution of snow depth on Antarctic sea ice is critical to estimating the sea ice thickness distribution from laser altimetry data, such as from Operation IceBridge or ICESat-2.  One major uncertainty in converting laser altimetry data to ice thickness is knowing the proportion of snow within the surface measurement. Snow redistributed by wind collects around areas of deformed ice, but it is not known how different surface morphologies affect this distribution. Here, we apply a textural segmentation algorithm to classify and group similar textures to infer the distribution of snow-ice ratios using snow surface freeboard measurements from Operation IceBridge (OIB) campaigns over the Weddell Sea. We find that texturally-similar regions have similar snow/ice ratios, but not similar snow depth measurements. This allows for the extrapolation of nadir-looking snow radar data using two-dimensional surface altimetry scans, providing a two-dimensional estimate of the snow depth. Using a convolutional neural network on an in-situ dataset, we find that local (~20 m) snow depth and sea ice thickness can be estimated with errors of < 20%, and that the learned convolutional filters imply that different surface morphologies have different proportions of snow/ice within the measured surface elevation. For the OIB data,  we show that at slightly larger scales (~180 m), snow depths can be estimated using the snow surface texture, and that the learned filters are comparable to standard textural segmentation filters. We also examine the statistical variability in the distribution of snow/ice ratios across different years to determine if snow distribution patterns on sea ice exhibit universal behaviour, or have significant interannual variations. These results suggest that surface morphological information can improve remotely-sensed estimates of snow depth, and hence sea ice thickness, compared to current methods. Such methods may be useful for reducing errors in Antarctic sea ice thickness estimates from ICESat-2.
A meta-analysis of paleolimnological records reveals the sensitivity of lacustrine carbon burial rates to carbon sources and preservation conditions during the Anthropocene
Authors: Jenny Jean-Philippe , Niemman Christoph , Francus Pierre , Noren Anders , Carvalhais Nuno
Published: March 2020

Inland waters are sites of active carbon (C) processing and transport along the land to ocean aquatic continuum (LOAC) that need to be accounted for closing the global C budget1,2. However, monitoring data are lacking and do not extend back as far as few decades, limiting our comprehension of the LOAC C cycle for the last centuries. Lake sediments provide a key archive for assessing C transport and transformation that occurs in lake catchments. Here, the analysis of large numbers of samples was performed on 420 lakes sediment records of the world to assess C burial rates and sources during the last 300 years. C and N (organic and mineral forms) on discrete samples were analyzed using a Variomax elemental analyzer to assess total C sequestration by lakes, C sources, and long-term changes in the contribution of allochtonous vs autochtonous sources to C transfers in lake-watersheds. Continuous sediment records were generated using core scanners (i.e. micro-XRF) and computed tomography to provide near-annual trends on terrigenous elements, here used as proxies of allochtonous sources (e.g. Al, Ti, K, Fe), and Mn:Fe ratio to infer past oxygen conditions3. Our results suggest that establishing a morphology-relevant lake typology that better characterises the types and distribution of oxygen conditions and terrigenous supplies across our sites is therefore the first step in providing a more robust evidence base for explaining the spatial-temporal variation in lake C burial rates.