bluuebunny/crossref_metadata_2025 huggingface dataset:
Methane Estimates in the Northeastern US using Continuous Measurements from a Regional Tower Network
Authors: Mueller Kimberly , Ghosh Subhomoy , Karion Anna , Gourdji Sharon , Lopez-Coto Israel , Murray Lee
Published: March 2020

In the past decade, there has been a scientific focus on improving the accuracy and precision of methane (CH4) emission estimates in the United States, with much effort targeting oil and natural gas producing basins. Yet, regional CH4 emissions and their attribution to specific sources continue to have significant associated uncertainties. Recent urban work using aircraft observations have suggested that CH4 emissions are not well characterized in major cities along the U.S. East Coast; discrepancies have been attributed to an under-estimation of fugitive emissions from the distribution of natural gas. However, much of regional and urban research has involved the use of aircraft campaigns that can only provide a spatio-temporal snapshot of the CH4 emission landscape. As such, the annual representation and the seasonal variability of emissions remain largely unknown. To further investigate CH4 emissions, we present preliminary CH4 emissions estimates in the Northeastern US as part of NIST’s Northeast Corridor (NEC) testbed project using a regional inversion framework. This area encompasses over 20% of the US and contains many of the dominant CH4 emissions sources important at both regional and local scales.  The atmospheric inversion can estimate sub-monthly 0.1-degree emissions using observations from a regional network of up to 37 in-situ towers; some towers are in non-urban areas while others are in cities or suburban areas. The inversion uses different emission products to help provide a prior constraint within the inversion including anthropogenic emissions from both the EDGAR v42 for the year 2008 and the US EPA for the year 2012, and natural wetland CH4 emissions from the WetCHARTs ensemble mean for the year 2010. Results include the comparison of synthetic model simulated CH4 concentrations (i.e., convolutions of the emission products with WRF-STILT footprints + background) to mole-fractions measured at the regional in-situ sites. The comparison provides an indication as to how well our prior understanding of emissions and incoming air flow matches the atmospheric signatures due to the underlying CH4 sources.  We also present a preliminary set of CH4 fluxes for a selected number of urban centers and discuss challenges estimating highly-resolved methane emissions using high-frequency in-situ observations for a regional domain (e.g. few constraints, skewness in underlying fluxes, representing incoming background, etc.). Overall, this work provides the basis for a year-long inversion that will yields regional CH4 emissions over the Northeast US with a focus on Eastern urban areas.
Mixing height derivation from aerosol lidar using machine learning: KABL and ADABL algorithms
Authors: Rieutord Thomas , Aubert Sylvain
Published: March 2020

Atmospheric boundary layer height (BLH) is a key parameter for air quality forecast. To measure it, a common practice is to use aerosol lidars: a strong decrease in the backscatter signal indicates the top of the boundary layer. This work explains and compares two methods of machine learning to derive BLH from backscatter profiles: the K-means algorithm and the AdaBoost algorithm. As K-means is unsupervised, it has less dependency on instrument settings, hence more generalization skills. AdaBoost was used for binary classification: boundary layer/free atmosphere. It has been trained on 2 days, labelled by hand, therefore it has less generalization skills but a better representation of the diurnal cycle. Both methods are compared to the lidar manufacturer's software and to the BLH derived from collocated radiosondes. The radiosondes are taken as reference for all other methods. The comparison is carried out on a 2 years period (2017-2018) on 2 sites (Trappes and Brest). Data come from Meteo-France's operational network. The code and the data that produced these results will be put under a fully open access licence, with the name of KABL (K-means for Atmospheric Boundary Layer) and ADABL (AdaBoost for Atmospheric Boundary Layer).
Pluri-millenial evolution of uranium speciation in lacustrine sediments
Authors: Lefebvre Pierre , Gourgiotis Alkiviadis , Mangeret Arnaud , Le Pape Pierre , Diez Olivier , Sabatier Pierre , Louvat Pascale , Merrot Pauline , Baya Camille , Zebracki Mathilde , Malet Emmanuel , Jézéquel Didier , Reyss Jean-Louis , Bargar John , Gaillardet Jérôme , Cazala Charlotte , Morin Guillaume
Published: March 2020

Uranium (U) is a toxic radionuclide which environmental dissemination must be limited. In this regard, understanding U immobilization mechanisms in reducing environments is essential for improving the management of radioactive waste and the remediation of contaminated sites. In particular, determining the long-term behavior of non-crystalline U(IV) species in (sub-)surface conditions is of growing importance, as these environmentally-relevant species have been recently showed to play a major role in U mobility. For this purpose, we investigated the evolution of U speciation over a pluri-millennial period in naturally U-enriched sediments from Lake Nègre (alt. 2354 m, Mercantour, France) as an analogue of contaminated systems. Several sediment cores were sampled at 24 m of water depth and preserved under anoxic conditions. Bottom sediments were dated back to 8700 cal BP. These organic- and Si-rich sediments display increasing U concentration with depth, from 350 to more than 1000 µg/g. Sequential ultrafiltration of surface waters and uranium isotopic ratios (238U/235U and (234U/238U)) of sediments and waters suggest that the deposition mode of U did not vary significantly with time, thus giving the opportunity to follow the effect of diagenesis on U speciation over more than 1000 years. Uranium LIII-edge X-Ray Absorption Near-Edge Structure (XANES) analysis shows that U is rapidly reduced in the upper sediment layers and is fully reduced at depth. Preliminary Extended X-Ray Absorption Fine Structure (EXAFS) spectroscopy data at the U LIII-edge reveals that U speciation evolved with depth in the sediment core, suggesting an effect of diagenesis in anoxic conditions on U solid speciation. Our results may help to design long-term storage conditions that are able to enhance the formation of poorly soluble U species in U-contaminated soils and sediments.
Soil record of the Holocene paleofires at the north of European Russia
Authors: Mergelov Nikita , Petrov Dmitry , Dolgikh Andrey , Zazovskaya Elya
Published: March 2020

Soils and sediments serve as complementary sources of detailed information on paleofires in various ecosystems. Despite the abundance of charcoal material entrapped in soils they remain relatively less studied pyrogenic archives in comparison to the sedimentary paleofire records (e.g. lacustrine and peat deposits), and that is especially the case for the most territory of Russia. We report here on the numerous soil archives of the Holocene forest fires at the Kola Peninsula (66.347°N, 37.948°E) and the north of Arkhangelsk region (64.747°N, 43.387°E) in Russia. Series of buried Podzols (up to ten successive profiles) separated by the distinct charcoal layers were revealed in specific geomorphological traps like the thermokarst depressions inherited from the early stages of moraine sediments formation (Kola Peninsula), as well as in active and paleokarst sinkholes in carbonate and sulfate rocks (Arkhangelsk region). The maximum temporal depth of archives was estimated as 10261±40 cal yr BP for the key site in Arkhangelsk region, with up to 12 major pyrogenic events recorded at the local scale. Soil formation at the inter-pyrogenic stages maintained a uniform direction for at least 10 thousand years and profiles of Podzols were regularly replicated at all the key sites. We employ here a combination of soil morphological hierarchical analysis, study of geomorphological processes leading to the burial of pyrogenic carbon, 14C dating of charcoal and TOC derived from the soil organic matter, carbon and nitrogen isotope ratio mass spectrometry and anthracomass concentrations analysis to extract a set of paleoenvironmental information from these soil archives. The study of complementary pyrogenic archives in the three-component system of the karst landscape (including bottom and slopes of the funnels, as well as the flat elevated areas between them) helped to mitigate overestimation or underestimation of the anthracomass concentration and allowed to acquire a detailed dataset on paleopyrogenic events at the local scale. This study is supported by the Russian Foundation for Basic Research, Project No. 19-29-05238.
Exploring long-term satellite observations of global 3-D gravity wave characteristics in the stratosphere
Authors: Hindley Neil , Wright Corwin , Hoffmann Lars , Moffat-Griffin Tracy , Alexander M. Joan , Mitchell Nicholas
Published: March 2020

Atmospheric gravity waves are a fundamental component of the Earth’s dynamical system. These mesoscale waves play a key role in the coupling of different atmospheric layers, acting as crucial drivers of the middle atmospheric circulation through the transport and deposition of energy and momentum. As Global Circulation Models (GCMs) achieve ever higher resolution in the stratosphere, there is a need to ensure that the simulated gravity waves resolved in these models are well constrained by observations, which in turn ensures that modelled circulations are realistic and not over-dependent on tuning with parameterisations. However, obtaining 3-D gravity-wave measurements in the real atmosphere is notoriously difficult. Global 3-D observations of wave properties in the stratosphere are required in order to accurately estimate gravity wave fluxes that can be compared to models. Here we analyse a unique long-term satellite dataset of specialised high-resolution 3-D temperature measurements from NASA’s AIRS/Aqua instrument from 2002-2020. By analysing these data with a 3-D Stockwell transform (3DST) using high-performance computing, we can reveal global distributions of gravity-wave amplitudes, wavelengths, intermittency and directional momentum fluxes in the stratosphere across two decades - the largest such 3-D study of stratospheric gravity waves performed yet. This long-term dataset reveals solar-cycle variability of gravity-wave amplitudes in the tropics, significant reductions in gravity-wave fluxes during southern Sudden Stratospheric Warmings (SSWs) and the persistent oblique propagation of wintertime gravity waves into the southern polar vortex around 60S each year, a phenomenon that is not observed in the northern hemisphere. With these new observations we can begin to better constrain simulated gravity waves and their impacts in GCMs, ultimately leading to better forecasts of weather and climate.
Electrojet estimates from mesospheric magnetic field measurements
Authors: Laundal Karl , Gjerloev Jesper , Yee Sam , Merkin Slava , Vanhamäki Heikki , Juusola Liisa , Reistad Jone
Published: March 2020

The auroral electrojet is traditionally measured remotely with magnetometers on ground or in low Earth orbit. The long distance, more than 100 km, means that smaller scale sizes are not detected. Because of this, the spatiotemporal characteristics of the electrojet are not known. Recent advances in measurement technology give hope of remote detections of the magnetic field in the mesosphere, very close to the electrojet. We present a prediction of the magnitude of these disturbances, inferred from the spatiotemporal characteristics of magnetic field-aligned currents. We also discuss how a constellation of small satellites carrying the Microwave Electrojet Magnetogram (MEM) instrument (Yee et al., 2020), could be used to essentially image the equivalent current at unprecedented spatial resolution. 
Nitrogen and phosphorus resorption efficiencies change under drought and shrub encroachment in a Mediterranean ecosystem
Authors: Lobo-do-Vale Raquel , Rodrigues José , Martins Joana , Haberstroh Simon , Alves Ana , Werner Christiane , Caldeira Maria Conceição
Published: March 2020

Mediterranean ecosystems, such as the savannah-type cork oak (Quercus suber) woodlands, are hotspots for climate change, as the highest impacts are forecasted for the Mediterranean region, mainly by more frequent and intense severe droughts. These ecosystems are also threatened by shrub encroachment, which might further decrease tree water availability and affect ecosystem functioning and resilience. Nevertheless, the combined effects of drought and shrub encroachment on ecosystems have seldom been investigated. A precipitation manipulation and shrub removal experiment was established in a cork oak woodland located in SE Portugal and invaded by the native shrub gum rockrose (Cistus ladanifer). Here we present and discuss the combined effects of drought and shrub encroachment on litterfall production of cork oak trees, an evergreen species, over two contrasting years, a wet year (2018) and a dry year (2019) and assess the nitrogen and phosphorus resorption efficiencies from senescent to green leaves.

A previous study reported significant increases in cork oak’s nitrogen resorption efficiency in response to drought. Our preliminary results also indicate changes in nitrogen and phosphorus resorption efficiencies. An increase in nutrient resorption efficiency is likely to mitigate the limitation in nutrient uptake by the roots during drought, improving tree fitness in the short-term. However, it will probably exert a negative feedback on the nitrogen and phosphorus cycles in the long-term which might affect the ecosystem functioning under the forecasted droughts.
Full-waveform inversion at Santorini volcano
Authors: Chrapkiewicz Kajetan , Paulatto Michele , Morgan Joanna , Warner Mike , Heath Benjamin , Hooft Emilie , McVey Brennah , Toomey Douglas , Nomikou Paraskevi , Papazachos Constantinos
Published: March 2020

Detailed knowledge about geometry and physical properties of magmatic systems at arc volcanoes promises to better constrain models of magma differentiation, transit and storage in the crust, and to help assess volcanic hazard.

Unfortunately, low-velocity zones associated with melt accumulation are particularly difficult to image by conventional travel-time tomography due to its limited resolving power, resulting in blurred boundaries and underestimated velocity contrasts.

Here we alleviate these issues by applying full-waveform inversion (FWI) to study a magmatic system of Santorini - an active, semi-submerged volcano with a known record of large, caldera-forming eruptions.

We use a 3D wide-angle, multi-azimuth seismic dataset from the recent PROTEUS experiment acquired with ca. 150 ocean-bottom/land seismic stations and ca. 14,000 air-gun shots. We implement a finite-difference immersed boundary method to simulate reflections off the caldera’s irregular topography, and pressure-velocity conversion to take full advantage of the multi-component data. We perform inversion with careful data-selection, increasing frequency up to 6 Hz, and extensive quality-control based on a phase spatial-continuity criterion.

A final P-wave velocity model of the upper crust offers a high-resolution image of Santorini magmatic and hydrothermal systems with pronounced low-velocity zones due to a high melt and water content respectively. The features are better resolved and the velocity contrasts distinctly sharper than in the starting model obtained with travel-time tomography. We also recover a previously undetected low velocity anomaly of >40% beneath Kolumbo - a submarine volcanic cone to the NE of Santorini caldera. We interpret this anomaly as a magmatic sill.
Re-assessment of airborne radiocesium re-suspended from contaminated ground surface after the Fukushima Nuclear Accident
Authors: Kajino Mizuo , Watanabe Akira , Igarashi Yasuhito , Zaizen Yuji , Kinase Takeshi , Ishizuka Masahide , Kita Kazuyuki
Published: March 2020

Kajino et al. (2016) (doi:10.5194/acp-16-13149-2016) assessed emission, transport, and deposition of airborne radiocesium from contaminated ground surface after the Fukushima nuclear accident for the entire year of 2013 by using numerical simulation, a field experiment on dust emission flux in a contaminated area (town of Namie, Fukushima prefecture), and air concentration measurements inside (Namie) and outside the contaminated area (Tsukuba, Ibaraki prefecture). In this study, additional comparison of the simulation results has been made against the fallout measurements made in Fukushima (city of Fukushima) and Tsukuba and we found that our previous simulation results substantial underestimated the observed fallout by 2 to 3 orders of magnitude. The reason is, in the previous simulation, we assumed the size distributions of aerosols are in the submicron range, even though recent studies indicated that the aerosol sizes should be much larger (i.g., Kinase et al., 2018, doi:10.1186/s40645-018-0171-z, Igarashi et al., 2019, doi:10.1038/s41598-018-37698-x, and this study). By assuming larger sizes of Cs-bearing aerosols, the simulated concentrations and depositions in both Fukushima and Tsukuba were significantly improved. Consequently, the re-assessed emission flux was modified by several ten times more than that previously assessed by Kajino et al. (2016), which was 0.048% per year.
Evaluation of next day fog forecast over Namibia using the WRF model
Authors: Weston Michael , Piketh Stuart , Formenti Paola , Brocardo Stephen , Andersen Hendrik , Voogt Roland
Published: March 2020

The Namibian coast line experiences fog when moist air from the southeast Atlantic is advected
over the desert landscape. We run the WRF model with the Thompson (2008) microphysics scheme,
with a default CCN number concentration of 100 cm-1, to forecast next day fog over the Namib
desert. Model output of liquid water content at the lowest level in the atmosphere is used to
represent fog and is evaluated against in situ observations of visibility and satellite products of
fog/low stratus. Preliminary results indicate that the model captures the spatial pattern of fog
excellently, however, the model over predicts fog occurrence. These results serve as the control run
for a future model sensitivity study.
Quantum sensors for gravimetry and gravity gradiometry
Authors: Schubert Christian , Herr Waldemar , Abend Sven , Gaaloul Naceur , Schlippert Dennis , Ertmer Wolfgang , Rasel Ernst M.
Published: March 2020

Quantum sensors utilising atom interferometry enable absolute measurements of gravity (1) and gravity gradients (2). This contribution will introduce the operation principle of atom interferometers, discuss their current state of the art and limitations, and outline the key techniques for improvements. It will report on our developments for transportable (3) and stationary high-perfomance devices (4) and give a perspective for space-borne quantum sensors in the frame of geodetic missions (5).
The presented work is supported by the CRC 1227 DQmat within the project B07, the German Space Agency (DLR) with funds provided by the Federal Ministry of Economic Affairs and Energy (BMWi) due to an enactment of the German Bundestag under Grant No. DLR 50WP1700, 50WM1952, by "Niedersächsisches Vorab" through "Förderung von Wissenschaft und Technik in Forschung und Lehre" for the initial funding of research in the new DLR-SI Institute, and through the "Quantum and Nano- Metrology (QUANOMET)" initiative within the project QT3.

(1) V. Ménoret et al., Scientific Reports 8, 12300, 2018; A. Trimeche et al., Phys. Rev. Appl. 7, 034016, 2017; C. Freier et al., J. of Phys.: Conf. Series 723, 012050, 2016; A. Louchet-Chauvet et al., New J. Phys. 13, 065026, 2011; A. Peters et al., Nature 400, 849, 1999.
(2) P. Asenbaum et al., Phys. Rev. Lett. 118, 183602, 2017; G. Rosi et al., Nature 510, 518, 2014; J. M. McGuirk et al., Phys. Rev. A 65, 033608, 2002.
(3) S. Abend et al., Proceedings of the International School of Physics "Enrico Fermi" 197, 393, 2019; S. Abend et al., Phys. Rev. Lett. 117, 203003, 2016.
(4) D. Schlippert et al., arXiv:1909.08524; J. Hartwig et al., New J. Phys. 17, 035011, 2015.
(5) A. Trimeche et al., Class. Quantum Grav. 36, 215004, 2019; K. Douch et al., Adv. Space. Res. 61, 1301, 2018.
A new data-driven subgrid 2d turbulence parameterization and comparison with conventional kinetic energy backscatter parameterizations in NEMO ocean model
Authors: Perezhogin Pavel
Published: March 2020

Kinetic energy backscatter (KEB) parameterizations of subgrid 2d turbulence have shown their efficiency in ocean models as they restore activity of mesoscale eddies. Modern KEBs utilize only two properties of badly resolved inverse energy cascade: KEB tendency should be larger than turbulent viscosity in spatial scale and amount of returning energy should compensate energy loss due to eddy viscosity. Typical operators for KEB tendency are Laplace operator with negative viscosity coefficient and stochastic process. Application of artificial neural networks (ANN) to approximate subgrid forces may give rise to new KEB models. The main challenge in this direction is to preprocess subgrid forces in such a way to reveal a part corresponding to returning of energy from subgrid scales. In this work, we propose to define subgrid forces as a term nudging a coarse-resolution model toward high-resolution model. This force is energy-generating and may be approximated with ANN. Conventional KEBs and ANN model are compared in Double-Gyre configuration of NEMO ocean model.
Role of the Arctic Sea Ice melt on the lower latitude Climate
Authors: Chandra Varunesh , Sukumaran Sandeep
Published: March 2020

The melting of polar ice caps and sea ice are of immediate concern in the context of global warming. The observations suggest that the thickness, as well as the areal extent of the Arctic sea ice, have been declining in the last three decades, in large part due to manmade global warming. The effect of faster sea ice melt on lower latitude climate is not well understood as compared to that of mid and high latitudes. It is reported that the mid-Pacific trough (MPT) can be influenced by a stationary wave train triggered in response to a melt of sea ice over the Bering strait (Deng et al., 2018, J. Clim).   The MPT is known to influence Pacific tropical cyclone (TC) activity.

         Here, we investigate the effect of the summer sea ice variability over the Arctic on Pacific TC activity. We have seen in the higher melting Sea Ice years showing the strong wave train toward the lower latitude over the northern pacific in comparison to the lower melting years and also affecting the pacific TCs. The summer Arctic sea ice concentration is regressed on TC track density and accumulated cyclone energy (ACE). Both track density and ACE show an increase with increased sea ice concentration. The wind shear over the tropical Pacific is found to have an opposite relation with the Arctic sea ice concentration that led to a more favorable environment for the TC development when the sea ice concentration is high.

KEYWORDS: Climate Change; Tropical Cylone;
Mapping forest natural disturbances dynamics in the Aosta Valley (Italy) through long-term trends derived from Landsat time series and innovative statistical approaches
Authors: Marzano Raffaella , Morresi Donato , Lingua Emanuele , Motta Renzo , Garbarino Matteo
Published: March 2020

Forest dynamics triggered by natural disturbances occurred in the Aosta Valley region were spatially mapped over time using long-term trends derived from Landsat time series spanning over 35 years, from 1985 to 2019. Among biotic and abiotic disturbance agents, the following were selected: wildfires, windthrows, snow avalanches, landslides and insect outbreaks. Landsat TM, ETM+ and OLI images acquired during the vegetative season (from June to September) with less than 80% cloud cover were employed to create synthetic images at one-year interval using the geometric median approach at the pixel-level. Forest dynamics due to disturbance occurrence and the following vegetation recovery were explored through inter-annual time series of different spectral indices such as normalized vegetation indices (Normalized Burn Ratio, Normalized Moisture Index) and the tasseled cap band transformations (wetness, angle). Changes in the linear trends of the spectral indices time series caused by disturbance occurrence were detected using a novel bottom-up approach in which a wavelet basis is adaptively constructed by merging neighbouring segments of the data. This method doesn’t require a priori knowledge of the time series parameters making it fully automated. Prior to perform the trend analysis, vegetation indices time series were filtered to remove residual invalid pixels and fill gaps of one-year length. Considering abrupt disturbances, this method highlighted sensitivity toward both high and low magnitude events and was able to accurately detect different severity degrees within the perimeter of the affected forest area. Historical wildfire perimeters and crown fires patches provided by the forest fire fighting corps of the Aosta Valley were used to perform preliminary severity maps validation. Considering two severity classes, ‘low to moderate’ and ‘moderate to high’, maps produced using the Normalized Burn Ratio achieved an overall accuracy of 83%. Future work is aimed to validate all the selected natural disturbance agents using historical field data available at the regional scale. Moreover, a rigorous and wide scale-based assessment of the capabilities of the algorithm in tracking post-fire forest recovery will be performed by integrating forest structure data from filed surveys and airborne LiDAR measurements.
A study using multitemporal Sentinel-2 data and Digital Elevation Model for calculating morphometric parameters over the Euphrates River Basin in Syria
Authors: Naaouf Nour , Székely Balázs
Published: March 2020

The Euphrates River is the main river running in Syria and the longest river in Western Asia and has three riparian countries, Iraq, Syria and Turkey. This research focuses on the Syrian part of the basin which makes 22% of total area of the basin.

Analyzing and evaluating the morphometric parameters is very important for understanding the nature of the surface and also for the sustainable territorial planning and management.

The goal of this study is to evaluate morphometric parameters and understand and analyze the nature of the terrain and determine the usability of the satellite images from Sentinel-2 for calculating the morphometric parameters and to compare their usability in the morphometric analysis with Digital Elevation Model.

Different morphometric characteristics have been generated in GIS environment and also remote sensing data (Sentinel-2 and Digital Elevation Model) have been applied used in this research and will be processed and analyzed using geospatial techniques.

The results allow the automated segmentation of the terrain based on derivatives of the input data. This division is compared to the typical land cover/land use of the various governorates in Syria.

As our study area is a long-lasting military conflict zone, this study will also help to better evaluate the river basin in Syria and to understand some practical problems related to the environment, including soil conservation and water conservation in term of irrigation land and drinking water supply which would also be affected by the armed conflict there.
VirES for Swarm – Virtual Research Environment
Authors: Pačes Martin , Santillan Pedrosa Daniel , Smith Ashley
Published: March 2020

VirES for Swarm [1] is a data manipulation and retrieval interface for the ESA Swarm constellation mission data products. It includes tools for studying various geomagnetic models by comparing them to the Swarm satellite measurements at given space weather and ionospheric conditions.

The list of the provided Swarm products is growing and it currently includes MAG (both, LR and HR), EFI, IBI, TEC, FAC, EEF, and IPD products as well as the collection of L2 SHA Swarm magnetic models, all synchronized to their latest available versions.

VirES provides access to the Swarm measurements and models either through an interactive visual web user interface or through a Python-based API (machine-to-machine interface). The latter allows integration of the users' custom processing and visualization.

The API allows easy extraction of data subsets of various Swarm products (temporal, spatial or filtered by ranges of other data parameters, such as, e.g., space weather conditions) without needing to handle the original product files. This includes evaluation of composed magnetic models (MCO, MLI, MMA, and MIO) and calculation of residuals along the satellite orbit.

The Python API can be exploited in the recently opened Virtual Research Environment (VRE), a JupyterLab based web interface allowing writing of processing and visualization scripts without need for software installation. The VRE comes also with pre-installed third party software libraries (processors and models) as well as the generic Python data handling and visualization tools.

A rich library of tutorial notebooks has been prepared to ease the first steps and make it a convenient tool for a broad audience ranging from students and enthusiasts to advanced scientists.

Our presentation focuses on the introduction of the new Virtual Research Environment and recent VirES evolution.

[1] https://vires.services
Unearthing the forgotten record of glacier change in southeast Greenland
Authors: Cooper Michael , Lewinska Paulina , Dowdeswell Julian , Hancock Edwin , Smith William , Rippin David
Published: March 2020

Prior to the satellite era (pre-1970s) knowledge of long-term glacier change is sparse. Although some glacier-wide mass balance datasets are available, few records extend beyond twenty years in length, or indeed, start prior to the 1980s; as such, identifying long-term trends between glacier change and global temperatures is difficult. As a result, extending the record of glacier change will not only help to identify such trends, but may also facilitate more robust understanding of future glacier response under a perturbed and varying climate.

Since the ‘heroic age of Arctic (and Antarctic) exploration’, many photographs of polar environments have been captured and stored for historic interest. These photographs, depicting images of past glaciers and ice sheet margins, have, as of yet, untapped potential to provide important insights into past glacier extent, and long-term behaviour.

Using computer-vision methodologies, we present a unique record of georeferenced 3-D elevation models using declassified aerial imagery dating from the 1930s—1980s at quasi-regular time steps. This study focusses upon two sections (ca. 190 km total length) of the southeast margin of the Greenland Ice Sheet (in the vicinity of Kangerlussuaq Glacier), capturing the history of both land- and marine-terminating outlet glaciers, and local glaciers. We examine quantitative information extracted from these reconstructions, allowing us to ‘back extend’ the record of glacial change in this region, by measuring changes in glacial extent, surface profiles and height (elevation), and calculating volume estimates.
The simulated transition from a hard snowball Earth
Authors: de Vrese Philipp , Stacke Tobias , Brovkin Victor , Caves Rugenstein Jeremy
Published: March 2020

Geological evidence suggests that Earth's past featured periods during which the planet was largely or even entirely covered by ice, a state termed "snowball Earth".  Model based studies confirm that one of Earth's equilibrium states is a fully glaciated planet (hard snowball) but it is not clear how this state could have been left once it had been established. We use simulations with the Max-Planck-Institute for Meteorology's Earth system model to investigate the conditions that enable the transition out of the snowball-state. We show that the high albedo of pure snow would have prevented deglatiation, even for extremely high atmospheric CO2 concentrations. Terminal deglaciation is only triggered for surface albedos corresponding to old, darkened snow or sea-ice. Here, increasing snowfall rates, resulting from the intensification of the hydrological cycle with rising CO2 concentrations, would have prohibited the gradual build-up of dust that leads to a darkening of the surface.  Only when assuming dust deposition fluxes at least similar to present-day fluxes, can the deglation be triggered for plausible atmospheric CO2 concentrations.
Regional stress field computation along the West Svalbard margin (Vestnesa ridge): Effect of the glacial isostatic adjustment.
Authors: Vachon Rémi , Schmidt Peter , Lund Bjorn , Patton Henry , Beaussier Stefan , Plaza-Faverola Andreia , Hubbard Alun
Published: March 2020

Release of greenhouse gasses is of major concern when it comes to climate change. Large amount of those gases are released through faults and fractures at the ocean floor, forming pockmarks at the surface. Understanding the formation of pockmarks and the fracture - fault network underlying them, is thus of first importance to apprehend the dynamics of gas seepages. We suggest that such fractures are closely related to the regional stress field and thus control by the combination of large scale tectonic processes, sedimentation - erosion mechanism and reactivation of inherited structures in the underlying basement.

The present study focus on the calculation of the regional stress field along Vestnesa ridge, a key location for methane seepage and pockmarks study. This area is located in a tectonically active region, boarded in the west by the Atlantic ridge and two major transform faults. In addition, deglaciation since the last glacial maximum (LGM), has induced a rebound of the lithosphere which also affects the stress field of the area including Fennoscandia, Svalbard and Greenland. However, it is difficult to estimate the effect of post-glacial rebound on the regional stress field, especially in a zone where the stress is mostly dominated by the effect of the Atlantic ridge push. To assess this problem, we built a time-dependent mechanical model of an elastic crust and viscoelastic mantle underlying the area of interest. We apply an ice cover on the surface of the model that varies according to the time-dependent ice-thickness model of Patton et al., 2016; 2017. The model runs for 50 000 yrs which includes 1) a glaciation phase till the last glacial maximum (LGM) at about -16000 yrs and 2), a deglaciation phase from the last LGM up to present time.

Preliminary results show that the amplitude of the stress change resulting from glacial adjustment, can be of the order of -2 MPa to 2 MPa along Vestnesa ridge. Moreover, the orientation of the maximum horizontal stress (σH) is modified according to the geometry and evolution of the ice cover, just as to the topography of the region affected by the lithospheric adjustment.
Global storm surges during a past warm climate, the Last Interglacial
Authors: Bakker Pepijn , Scussolini Paolo , Muis Sanne , Dullaart Job , Rovere Alessio , Stocchi Paolo , Aerts Jeroen
Published: March 2020

We present here a novel application of state-of-the-art surge modeling on a past climate of special interest. The Last Interglacial (LIG; 125,000 years ago) was the latest instance of a climate (slightly) warmer than present: for this reason its study can inform on the response of several climate components to a climate state with partial resemblance to possible futures. Climate variables like temperature and precipitation have been extensively studied for the LIG. Here, we calculate for the first time the implications of the altered LIG atmospheric circulation (both in mean state and extremes) for storm surges along the global coastline. This presents particular interest since it is often claimed that a warmer climate may imply enhanced storminess in some ocean basins. We use sub-daily results from simulations of the LIG and of the pre-industrial periods with the climate model CESM1.2 (equipped with atmosphere module CAM5, with ca. 1 degree horizontal resolution) to force the Global Tide and Surge Model (GTSM) for 30-years at climate equilibrium conditions. We analyze patterns of storminess and of storm surges, and report on the anomalies in those metrics between the LIG and the pre-industrial climate. These results can help contextualize proxy-based reconstructions of storms of the LIG, as well as projections of storm surges in a future warmer climate. Finally, we also reconstruct tides of the LIG, aiming to provide useful constrains to paleo sea-level reconstructions.
The Petermann Ice Shelf Estuary and its impact on ice-shelf stability
Authors: Boghosian Alexandra , Pitcher Lincoln , Smith Laurence , Bell Robin
Published: March 2020

In a warming world, increased meltwater will form on Antarctica’s ice shelves. The fate of this meltwater will be critical to future ice-shelf and ice-sheet stability. Two main observations define the current theoretical framework for understanding the influence of surface hydrology on ice-shelf stability. The first is the collapse West Antarctica’s Larsen B Ice Shelf that was triggered by the formation of thousands of surface ponds atop the ice shelf. The second is the observation of a waterfall on the Nansen Ice Shelf, in East Antarctica, that is hypothesized to protect the ice shelf from hydrofracture by removing meltwater from the ice-shelf surface.

We present a third process that couples ice-shelf hydrology to atmospheric and ocean forcing: the development of an ice-shelf estuary on the Petermann Ice Shelf in northwest Greenland.  High-resolution imagery and digital elevation models (DEMs) shows that channelized surface meltwater on the Petermann Ice Shelf in northwest Greenland incises into underlying ice to form an estuary that propagates fractures along the ice shelf. The estuary at the front of the Petermann Ice Shelf is indicated by the convergence of sea ice at the river mouth, the upstream transport of sea ice in the channel as far as 460 m from the calving front, and the persistence of water in the channel following the end of seasonal surface melt. Between 2013 and 2018, the estuarine reach of the river tripled in width and a 1.5 km longitudinal crack propagated along the bottom of the channel. The Petermann Ice Shelf Estuary forms on top of a basal channel, where basal melting has led to ice-shelf thinning, and the creation of the linear surface depression in which the estuary forms.

The Petermann Estuary may be the first of several ice-shelf estuaries to develop in a warming climate. Widespread surface melting on ice shelves in Greenland and Antarctica increases the urgency to determine the influence of surface hydrology on ice-shelf stability. We hypothesize that surface rivers may initially buffer ice shelves from collapse by terminating in waterfalls and preventing the formation of damaging lakes. However, with increased meltwater transport across ice shelves, channels can incise to sea level and establish estuaries. Once an estuary is established, estuarine weakening can lead to fracture propagation and enhanced calving, destabilizing ice-shelves, and increased ice-sheet mass loss.
Perceiving and managing the 2018 & 2019 droughts in Europe: is there a need for macro-governance in Europe?
Authors: Blauhut Veit , Teutschbein Claudia , Andersen Mathias N. , Brunner Manuela , Cammalleri Carmelo , Cindrić Kalin Ksenija , Finger David C. , Huysmans Marijke , Manevski Kiril , Osuch Marzena , Romanowicz Renata J. , Stahl Kerstin , Stoelzle Michael , Van Loon Anne F. , Van Vliet Michelle T.H. , Wanders Niko , Vogt Jürgen , Vidal Jean-Philippe , Williams Patrick
Published: March 2020

In recent years, the adverse effects of drought have been experienced and perceived more severely and frequently all over Europe. These impacts are a result of the drought hazard and the socio-economic and ecological vulnerability. Due to the heterogeneity of Europe’s hydro-climatology and its cultural, political, social and economic diversity , the socio-economic and ecological impacts vary not only with respect to the extent, duration and severity of the drought, but also with the characteristics of affected societies, economic sectors and ecosystems. 

The lack  of understanding the spatio-temporal differences in the drivers of drought risk hinders the successful mitigation of future impacts, and the design of suitable reactive and proactive drought action plans. Therefore, this study describes the European drought events of 2018 and 2019 beyond the hazard. The hypothesis to be proven is that similar hazard conditions result in different impacts due to national and sub-national differences in drought vulnerability, perception and drought-risk management. Based on research in 35 European countries, comparable national datasets on drought management and perception are established. For each of these countries, a uniform questionnaire was distributed to water management-related stakeholders at different administrative levels. A major focus of the questions was the perception and impacts of the recent droughts and current management strategies on a national and sub-national scale. The results of the questionnaires are also compared to country-scale profiles of past drought events for different drought types, i.e. meteorological, soil moisture, hydrological and vegetation drought, which were established based on information derived from the European Drought Observatory indicator system.

The results highlight a large diversity in the national perception of drought as a natural hazard and its impacts; but also a different spatial extent of 2018/2019 drought events At the same time,  existing drought management strategies are shown to increase national and sub-national resilience. The study, therefore, calls for international exchange and mutual learning to improve national and international drought governance and management.
The Alpine Environmental Data Analysis Centre (www.alpendac.eu) – A Component of the Virtual Alpine Observatory (VAO) (www.vao.bayern.de)
Authors: Bittner Michael , Laux Dominik , Goussev Oleg , Wüst Sabine , Handschuih Jana , Götz Alexaner , Heller Helmut , Munke Johannes , Mair Roland , Wittmann Bianca , Beck Inga , Neumann Markus , Rehm Till
Published: March 2020

The “Alpine Environmental Data Analysis Centre” (AlpEnDAC) is a research data management and analysis platform for research facilities around the Alps and similar mountain ranges. It provides the computational infrastructure for the Virtual Alpine Observatory (VAO), which is a research network of European high-altitude research stations (http://www.vao.bayern.de).

 

Within the scope of previous work, the platform was developed with the focus on research data and metadata management as well as analysis and simulation tools. It offers the possibility to store and retrieve data securely (data-on-demand), to share it with other scientists and to interpret it with the help of computing-on-demand solutions via a user friendly web-based graphical user interface. The AlpEnDAC allows the analysis and consolidation of heterogeneous data sets from ground-based to satellite instruments.

 

In a further development phase, launched on 1 August 2019, the existing services of the AlpEnDAC will be supplemented by new components in the fields of user support and quality assurance. Furthermore, the modelling and analysis software portfolio will be extended, focusing on the development of innovative services in the fields of service-on-demand and operating-on-demand as well as the integration of new data sources and measurement instruments.

 

The AlpEnDAC helps environmental scientists to benefit from modern data management, data analysis, and simulation techniques. The VAO network, now including ten countries (Austria, France, Germany, Georgia, Italy, Norway, Slovenia, Switzerland, Bulgaria, and the Czech Republic) is an ideal and exciting context for developing the AlpEnDAC with researchers.

 

This project receives funding from the Bavarian State Ministry of the Environment and Consumer Protection.
Drivers of interannual sea ice variability on the Arctic continental margin north of Svalbard
Authors: Lundesgaard Øyvind , Sundfjord Arild , Renner Angelika H. H.
Published: March 2020

Sea ice concentration along the Arctic continental margin north of Svalbard is in decline, but superimposed on this trend is considerable interannual variability. Many factors impact sea ice in this region, including atmospheric cooling and heating, winds, sea ice advection, and oceanic heat transport associated with the inflow of Atlantic Water, and regional sea ice cover remains difficult to predict. We present observations of upper ocean temperature between 2012 and 2017 from an ocean mooring located on the continental shelf break north of the Barents Sea, together with concurrent time series of atmospheric variables and sea ice concentration, drift, and thickness, derived from satellite and reanalysis data. While the inflow of Atlantic Water undoubtedly plays a key role in maintaining the area north of Svalbard ice-free through much of the year, variations in upper ocean temperature do not explain major interannual sea ice anomalies during the study period. Instead, we find that the magnitude of sea ice advection from the north and east was a major driver of interannual sea ice variability during our study.
Calving Front Machine (CALFIN): Automated Calving Front Dataset and Deep Learning Methodology for East/West Greenland, 1972-2019
Authors: Cheng Daniel , Mohajerani Yara , Wood Michael , Larour Eric , Hayes Wayne , Velicogna Isabella , Rignot Eric
Published: March 2020

We present Calving Front Machine (CALFIN), an automated method for extracting calving fronts from satellite imagery. We generate results for 66 glaciers along East/West Greenland from 1972 to 2019. We output these results as a dataset, and provide new constraints on glacial evolution over the time period. This method is uniquely robust to clouds, illumination differences, ice mélange, and Landsat-7 Scan Line Corrector errors. The current implementation offers a new opportunity to explore previous trends, and validate existing models moving forward.

This method utilizes deep learning, in the form of the Google DeeplabV3+ Xception derived CALFIN Neural Network. This approach builds on existing work by Mohajerani et al., Zhang et al., and Baumhoer et al. Additional post-processing techniques allow our method to achieve accurate and useful segmentation of raw images into Shapefile outputs. 

We achieve are often indistinguishable from the manually-curated fronts, deviating from such test data by 1 pixel (about 80 meters) or less XXX% of the time across 162 test images.

CALFIN excels among the current state of the art. We show this by performing a model inter-comparison to evaluate CALFIN's performance against existing methodologies. We also showcase CALFIN's ability to generalize to SAR and MODIS imagery. We achieve a mean error of 2.25 pixels (86.76 meters) from the true front on a diverse set of 162 testing images.