bluuebunny/crossref_metadata_2025 huggingface dataset:
The impact of crustal structures on multiple frequency and waveform tomography of Antarctica
Authors: Tsekhmistrenko Maria , Lebedev Sergei
Published: March 2020

We present two preliminary tomography models of Antarctica using seismic data recorded globally since 1994. Through combined efforts, several seismic broadband arrays have been deployed in Antarctica in previous decades, enabling the generation of two types of tomography models in this study: a multiple-frequency body-wave tomography and a waveform tomography model. Altogether, more than 2000 global events are collected resolving this region in great detail.

Crustal correction is crucial in seismic tomography, as it can cause the crustal smearing or leakage of shallow heterogeneities into the deep mantle. In global multiple-frequency tomography, synthetic seismograms are calculated on a spherically symmetric earth model (e.g. PREM, IASP91) in which effects of the crust, ellipticity, and topography are neglected. At a later stage, corrections are applied to the measured traveltimes to account for the known deviations from spherically symmetric earth models.

In waveform tomography, the crust has a significant impact on the Rayleigh and Love wave speeds. We invert for the crustal structure and explicitly account for its highly non-linear effects on seismic waveforms. Here, we implement a flexible workflow where different 3D reference crustal models can be plugged in. We test this using the CRUST2.0 and CRUST1.0 models.

In this study, we quantify the effects of these crustal models on two types of inversion techniques with a focus on the mantle structure beneath Antarctica. We compare the mantle structures beneath Antarctica imaged by a multiple-frequency body-wave tomography technique (e.g., Hosseini et al, 2019) and a waveform tomography method (Lebedev et al. 2005; Lebedev and van der Hilst 2008) using CRUST1.0 and CRUST2.0.

References:
K. Hosseini, K. Sigloch, M. Tsekhmistrenko, A. Zaheri, T. Nissen-Meyer, H. Igel, Global mantle structure from multifrequency tomography using P, PPand P-diffracted waves, Geophysical Journal International, Volume 220, Issue 1, January 2020, Pages 96–141, https://doi.org/10.1093/gji/ggz394

S. Lebedev, R. D. Van Der Hilst, Global upper-mantle tomography with the automated multimode inversion of surface and S-wave forms. Geophysical Journal International, Volume 173, Issue 2, May 2008, Pages 505–518, https://doi.org/10.1111/j.1365-246X.2008.03721.x

A. J. Schaeffer, S. Lebedev, Global shear speed structure of the upper mantle and transition zone, Geophysical Journal International, Volume 194, Issue 1, 1 July 2013, Pages 417–449, https://doi.org/10.1093/gji/ggt095
Complex multi-decadal ice dynamical change within the interior of the Greenland Ice Sheet
Authors: Williams Joshua , Gourmelen Noel , Nienow Peter
Published: March 2020

Observations of ice dynamical change in the interior of the Greenland Ice Sheet, at distances >~100 km from the ice-margin, are sparse, exhibiting very low spatial and temporal resolution (e.g. Sole et al., 2013; Doyle et al., 2014; Van de Wal et al., 2015). As such, the behaviour of interior Greenland ice represents a significant unknown in our understanding of the likely response of the ice sheet to oceanic and atmospheric forcing. The observation of a 2.2 % increase in ice velocity over a three-year period at a location 140 km from the ice margin in South West Greenland (Doyle et a., 2014) has been inferred to suggest that the ice sheet interior has undergone persistent flow acceleration. It remains unclear, however, whether this observation is representative of wider trends across the ice sheet.

Here, we investigate changes in ice motion within Greenland’s interior by utilising recent satellite-derived ice velocities covering the period 2013-2018 (Gardner et al., 2019) in conjunction with in-situ velocities collected at 30 km intervals along the 2000 m elevation contour during the mid-1990s (Thomas et al., 2000). Previous observations from the late-1990s/early-2000s through to late-2000s/early-2010s have revealed significant speed-up at many of Greenland’s tidewater glaciers (e.g. Bevan et al., 2012; Murray et al., 2015), in contrast to widespread deceleration within the ablation zone of the South West land-terminating margin (e.g. Tedstone et al., 2015; Van de Wal et al., 2015; Stevens et al., 2016). The recent availability of satellite data enables us to compare annual ice velocities from the period 2013-2018 to those collected at GPS stations in the mid-1990s, thereby enabling us to detect any long-term changes in ice-sheet wide inland ice motion during a period of considerable climatic and potentially significant dynamic change.

We observe multi-decadal interior ice acceleration of >15 % at Jakobshavn Isbrae, with similar inland accelerations at Kangerlugssuaq, Sermiligarssuk Brae and Narsap Sermia, and smaller velocity increases upstream of other marine-terminating outlets; these accelerations suggest that dynamic change at the margins has propagated considerable distances into the ice sheet interior. By contrast, ice velocities have slowed inland of some tidewater outlets such as Helheim Glacier, Umiamako Isbrae and Hagen Brae, confirming complex spatial variability in interior response to oceanic and atmospheric forcing. Furthermore, whilst prior work suggested that South West Greenland’s land-terminating sector experienced persistent interior speed-up between 2009 and 2012 (Doyle et al., 2014), our results reveal a >10% multi-decadal slowdown within the same sector, suggesting this region is resilient to recent increases in surface melt forcing.
Students learning phenology for becoming citizen scientists: an example of Italian High School students and CNR researchers teamwork experience
Authors: Cesaraccio Carla , Canu Annalisa , Pellizzaro Grazia , Masia Pierpaolo , Fadda Maria Leonarda
Published: March 2020

Citizen science is the scientific research that involves the participation of the public assisting professional scientists. This typically occurs in helping to data collection and/or data analysis, and an increasingly popular use of citizen science is the collection of phenological data, like wildflowers blooming in summer or leaves changing color in fall. Studying the life cycles of plants (phenology) reveals some consequences of climate change.

The PCTO (Percorsi per le Competenze Trasversali e per l'Orientamento) is a school-work alternation program and represent an innovative teaching method, introduced in 2015 by the Italian Ministry of Education, University and Research. This program, through practical experience, helps to consolidate the knowledge acquired at school and to enrich the student training. The school-work alternation is compulsory for all the students of the last three years of high school (13-17 years age). This program is a cultural change that incorporates good European practices, aimed at creating a synergy between school and work in order to encourage students to follow program learning inside of a public/private company.

The National Research Council of Italy is a partner of this program and each year students from high school are involved in technical and research activities. During the years 2015-2019, the Institute for the BioEconomy of Sassari, offered a School-Work learning program dedicated exclusively to Phenological and Pollen monitoring to groups of students of High School. While they employed their skills at work, they learnt to implement the specific protocols of a scientific project. These experiences increased their awareness of the essential role they can play by acquiring new knowledge of the environment and skills through scientific tools of citizen science. In this paper, results of the Phenological and Pollen monitoring program held at IBE-CNR Sassari are illustrated.

In the future, citizen scientists can provide reliable observations when following scientific methods and standardized protocols. Phenological monitoring programs based on volunteers support will become increasingly important in providing open‐access, standardized data sets capable of supporting the process of answering ecological and global change questions.
Investigating calving front morphology as a precursor to dynamic behaviour at a large Greenlandic tidewater glacier
Authors: Bunce Charlie , Nienow Pete , Gourmelen Noel , Cowton Tom
Published: March 2020

Successful prediction of the response of the Greenland Ice Sheet to climate warming requires accurate estimation of future ice loss from tidewater glaciers. Patterns of tidewater glacier retreat and advance have acted as an important proxy for understanding the processes associated with frontal ablation. It has not however been possible to effectively constrain commonality in these observed patterns that can then be directly linked to the influence of specific controls on ice loss. Here, we investigate planform changes in calving front morphology, an aspect of glacier dynamics that has received little prior attention; however, an improved understanding and quantification of the role of morphometric change in influencing glacier dynamics and iceberg calving may provide critical insights into tidewater glacier behaviour. We develop a buffer analysis method to quantify changes in calving front morphology at Narsap Sermia, a large tidewater glacier in southwest Greenland that has experienced substantial recent retreat. Our results reveal no distinct temporal or spatial patterns in the timing or magnitude of morphological change. Furthermore, we found no statistically significant relationships between morphological change and a range of forcing factors including air temperatures, modelled estimates of subglacial discharge and variations in glacier bed geometry. Our results therefore suggest that process driven morphological terminus change is not an effective predictor of terminus retreat and instead support the application of generalised parameterisations of tidewater glacier retreat within ice-dynamic models.
Seasonal Hydrometeorological Forecasts for Water Managment in West- and Northeast Africa: Development, Operationalisation and Performance of a Regional Prediction System
Authors: Kunstmann Harald , Lorenz Christof , Portele Tanja , Laux Patrick , Bliefernicht Jan , Salack Seyni , Gaber Ammar , Mohammed Yasir
Published: March 2020

It is the knowledge of the coming months that can be crucial for the management and control of water reservoirs for hydropower generation or for irrigation. This is particularly important in semi-arid regions of Africa that are characterized by distinctive dry seasons, i.e. where rainfall is limited to few months only. In addition, observation data in Africa are usually extremely sparse and computational power for forecasting systems is difficult to access. We present the spatial disaggregation and bias-correction of the globally available ECMWF’s newest seasonal forecast system SEAS5 and its tailored operational processing to support local water resources management and decision-makers. The forecast horizon is up to 7 month lead time, and our final forecasts have 0.1° spatial resolution. For the retrospective years 1981 till 2016 our ensemble consists of 25 members, while for the ongoing forecasts since 2017 there are 51 members available, allowing probabililistic predictions The performance of the regional prediction system is presented for 1) the Tekeze-Atbara and Blue Nile basins in Eithiopia/Sudan, and 2) the Volta and Niger basins in West Africa. The evaluation against the reference ERA5 data shows significant reduction in biases from the monthly averages as well as consistent and lead-independent forecasts characteristics like wet/dry frequencies. The performance metrices considered comprise accuracy (mean absolute error skill score), overall performance (continuous ranked probability skill score), sharpness (interquantile range skill score) and reliability. The operationalized system provides seasonal predictions each month to support water management on regional and local levels.
Mechanisms affecting equilibrium climate sensitivity in the PlaSim Earth System Model with different ocean model configurations
Authors: Angeloni Michela , Palazzi Elisa , von Hardenberg Jost
Published: March 2020

The equilibrium climate sensitivity (ECS) of a state-of-the-art Earth System Model of intermediate complexity, the Planet Simulator (PlaSim), is determined under three tuned configurations, in which the model is coupled with a simple Mixed Layer (ML) or with the full 3D Large Scale Geostrophic (LSG) ocean model, at two horizontal resolutions, T21 (600 km) and T42 (300 km). Sensitivity experiments with doubled and quadrupled CO2 were run, using either dynamic or prescribed sea ice. The resulting ECS using dynamic sea ice is 6.3 K for PlaSim-ML T21, 5.4 K for PlaSim-ML T42 and a much smaller 4.2 K for PlaSim-LSG T21. A systematic comparison between simulations with dynamic and prescribed sea ice helps to identify a strong contribution of sea ice to the value of the feedback parameter and of the climate sensitivity. Additionally, Antarctic sea ice is underestimated in PlaSim-LSG leading to a further reduction of ECS when the LSG ocean is used. The ECS of ML experiments is generally large compared with current estimates of equilibrium climate sensitivity in CMIP5 models and other EMICs: a relevant observation is that the choice of the ML horizontal diffusion coefficient, and therefore of the parameterized meridional heat transport and in turn the resulting equator-poles temperature gradient, plays an important role in controlling the ECS of the PlaSim-ML configurations. This observation should be possibly taken into account when evaluating ECS estimates in models with a mixed layer ocean. The configuration of PlaSim with the LSG ocean shows very different AMOC regimes, including 250-year oscillations and a complete shutdown of meridional transport, which depend on the ocean vertical diffusion profile and the CO2 forcing conditions. These features can be explored in the framework of tipping points: the simplified and parameterized form of the climate system components included in PlaSim makes this model a suitable tool to study the transitions occurring in the Earth system in presence of critical points.
Exploring frictional velocity dependence as a mechanism for slow earthquake rupture
Authors: Krogh Julia , Marone Chris
Published: March 2020

Earthquakes fail through a spectrum of slip modes ranging from slow slip to fast elastodynamic rupture. Slow earthquakes, or slow-slip events, represent fault slip behaviors that involve quasi-dynamic, self-sustained rupture propagation. To better understand the mechanisms that limit the slip speed and propagation rates of slow slip, we focus on a particular parameter: the critical frictional weakening rate of the fault surface, kc. When kc is approximately equal to k, the elastic loading stiffness of the fault, complex fault slip behaviors including slow-slip events are observed. If kc has a negative dependence on slip velocity, acceleration during the coseismic phase could decrease kc until it approximates k, terminating in a slow earthquake. Here, we describe the results of laboratory experiments designed to quantify the dependence of kc on frictional slip velocity. We conducted double-direct shear experiments in a biaxial shearing apparatus with 3 mm-thick fault zones composed of quartz powder to simulate fault gouge. We focus on step decreases in slip velocity from 300 to 3 m/s that were performed for a range of normal stresses, from 10 to 20 MPa, which we know to be near the stability transition from stable to unstable sliding defined by k/kc ~ 1.0. Under stable conditions, rate-state friction modeling was used to determine kc for each velocity step. Our data provide direct insight on the stability transition associated with kc(V), including experiments for which slow-slip instabilities grew larger and faster throughout velocity-step sequences. Ultimately, both numerical modeling and observational data indicate that the velocity dependence of kc is an important parameter when considering the mechanisms of slow earthquake nucleation. 
Assessing the response of forest productivity to climate extremes in Switzerland using model-data fusion
Authors: Trotsiuk Volodymyr ,   QUPFiS team
Published: March 2020

Under unprecedent climate change and increased frequency of extreme events, e.g. drought, it is important to assess and forecast forest ecosystem vulnerability and stability. Large volumes of data from observational and experimental networks, increases in computational power, advances in ecological models, and optimization methodologies are the main measures to improve quantitative forecasting in ecology. Data assimilation is a key tool to improve ecosystem state prediction and forecasting by combining model simulations and observations. We assimilated observations of carbon stocks and fluxes from 271 permanent long-term forest monitoring plots across Switzerland into the 3-PG forest ecosystem model using Bayesian inference, reducing the bias of model predictions from 14% to 5% for forest stem carbon stocks and from 45% to 9% for stem carbon stock changes, respectively. We then estimated the productivity of forests dominated by Picea abies and Fagus sylvatica for the period of 1960-2018 and tested for climate-induced shifts in productivity along elevational gradient and in extreme years. Overall, we demonstrated a high potential of using data assimilation to improve predictions of forest ecosystem productivity. Furthermore, our calibrated model simulations suggest that climate extremes affect forest productivity in more complex ways than by simply shifting the response upwards in elevation.
Quantifying forest growth and uncertainty across Brazil under potential future climates: combing models and Earth Observation
Authors: Smallman Thomas , Milodowski David , Williams Mathew
Published: March 2020

Forest play a major role in the global carbon cycle storing large amounts of carbon in both living and dead organic matter. Forests can be either a sink or source of carbon depending on the net of far larger fluxes of carbon into (photosynthesis) and out of (mortality, decomposition and disturbance) forest ecosystems. Due to the potential for substantial accumulation of carbon in forests, has led to nationally determined commitments (NDCs) by Governments across the world to protect existing and plant large areas of new forest. However, significant uncertainty remains in our understanding of current forest carbon cycling, especially mortality and decomposition processes, and how carbon cycling will change under climate change. These uncertainties present two connected challenges to effective forest protection and new planting; (i) which existing forests are under the greatest risk to climate change and (ii) where are the most climate safe locations for new forest planting to maximise carbon accumulation.

Here we combine a terrestrial ecosystem model of intermediate complexity (DALEC) with Earth observation (e.g. leaf area, biomass, disturbance) and databased information (soil texture and carbon stocks) within a Bayesian model-data fusion framework (CARDAMOM) to retrieve location specific carbon cycle analyse (i.e. parameter retrievals) across Brazil at 0.5 x 0.5 degree spatial resolution between 2001 and 2015. CARDAMOM allows us to retrieve, independently for each location analysed, an ensemble of parameters for DALEC which are consistent with the location specific observational constraints and their uncertainties. These ensembles give us multiple potential, but observation consistent, realisations of forest carbon cycling and ecosystem traits. We directly quantify our uncertainty in forest carbon cycling and ecosystem traits from these ensembles. The DALEC parameterisations are then simulated into the future under a range of climate scenarios from the CMIP6 model dataset. From these simulations we will, with defined uncertainty, quantify the impact on forest carbon accumulation of existing forest and the potential accumulation of new planting. This information can feed into national planning identifying locations which have the greatest confidence of being a net sink of carbon under climate change highlighting forest areas which are most important to protect and suitable for new planting.
Comprehensive evaluation of precipitation analyses using a very dense rain gauge network in southeast Austria
Authors: Ghaemi Esmail , Foelsche Ulrich , Kann Alexander , Kirchengast Gottfried , Fuchsberger Juergen
Published: March 2020

Precipitation is one of the most important inputs of meteorological and hydrological models and also flood warning systems. Thus, accurate estimation of rainfall is essential for improving the reliability of the models and systems. Although remote sensing (RS) techniques for rainfall estimation (e.g., weather radars and satellite microwave imagers) have improved significantly over the last decades, rain gauges are still more reliable and widely used for this purpose and also for the evaluation of RS estimates. Since the characteristics of a rainfall event can change rapidly in space and time, the accuracy of rain gauge estimation is highly dependent on the spatial and temporal resolution of the gauge network.

The main aim of this study is to evaluate the ability of the Integrated Nowcasting through Comprehensive Analysis (INCA) of the Central Institute for Meteorology and Geodynamics (ZAMG) to detect and estimate rainfall events. This is done by using 12 years of data from a very dense rain gauge network, the WegenerNet Feldbach region, as a reference, and comparing its data to the INCA analyses. INCA rainfall analysis data are based on a combination of ZAMG ground station data, weather radar data, and high-resolution topographic data. The system provides precipitation rate data with a 1 km spatial grid resolution and 15 minutes temporal resolution. The WegenerNet includes 155 ground stations, almost uniformly spread over a moderate hilly orography area of about 22 km × 16 km.

After removing outliers and scale WegenerNet data to 1 km, the accuracy of INCA to detect and estimate rainfall events was investigated using 12 years of the dataset. The results show that INCA can detect rainfall events relatively well. It was found that INCA overestimates the rainfall amount between 2012 and 2014, and generally overestimates precipitation for light rainfall events. For heavy rainfall events, however, an underestimation of INCA is prominent in most events. Based on the results, the difference between INCA and WegenerNet estimates is relatively higher during the wet season in the summer half-year (May-September). It is worth pointing out that INCA performs better in detecting and estimating rainfall around the two ZAMG stations located within the study area.
Towards operational NEMO model for the Baltic Sea
Authors: Kärnä Tuomas , Lehtiranta Jonni , Tuomi Laura
Published: March 2020

We are developing a new operational circulation model for the Baltic Sea using NEMO v4.0. The model configuration is derived from the NEMO v3.6 1 nmi NemoNordic setup (Hordoir et al., Geoscientific Model Development, 2019). A pre-operational version of the model has been implemented to produce daily forecasts of water level, temperature, salinity, and currents, as well as sea ice coverage. In this poster we present model validation for a two-year hindcast simulation. The results indicate that daily and seasonal variability of water levels and sea surface salinity are well captured. Sea ice coverage is well represented, although slightly over-estimated. Comparisons at several mooring locations show realistic vertical salinity structure, and verify that the model can simulate Baltic inflow events. Overall, the model skill has significantly improved compared to previous operational models.
Identifying flow transience in the hyporheic zone by Electric Resistivity Tomography
Authors: Riml Joakim , Wu Liwen , Earon Robert , Krause Stefan , Blume Theresa
Published: March 2020

The importance of hydrological interactions between groundwater and surface waters and the consequential transport of mass and energy across the streambed – water interface has gained significant research attention lately. In this phenomenological study we investigated the transient nature of hyporheic exchange as a response to flood events by performing a stream manipulation experiment in a small boreal stream within the Krycklan catchment, Sweden. The stream flow was manipulated in order to create a flood event and investigate the responding dynamically changing spatial extent of the hyporheic zone. The artificial flood caused an approximately 5-fold increase in stream discharge.

The experimental set-up consisted of both geophysical and hydrological methods, including time-lapse Electrical Resistivity Tomography (ERT) along the thalweg of a 6.3 m long stream section, with a 0.1 m longitudinal spacing of the electrodes. A constant stream water electric conductivity (EC) was obtained throughout the experiment by using a variable rate tracer injection of chloride. Additional measurements of background EC in the streambed sediments as well as streambed topography (from a total station) and subsurface structures (from Ground Penetrating Radar) were used to support the results from the ERT.

With combined experimental and numerical modeling approaches, the hyporheic response to transient hydrologic boundary conditions and small scale streambed heterogeneities were investigated. Results indicated that a quick response of the hyporheic zone to the changing pressure distribution on the streambed was strongly controlled by the shape of the flood hydrograph. Moreover, the response resulted in an alteration of the hyporheic flowpaths, which increased the hyporheic zone depth and contributed to a dynamically-changing residence time distribution within the hyporheic zone. This alteration was further complicated by the local streambed heterogeneities. The observed substantial variabilities in the hyporheic fluxes over the time span of a flood hydrograph and longitudinally over the measured stream section has direct consequences on the biogeochemical and hydro-ecological functioning of the hyporheic zone, which would be inadequately estimated using homogenous, steady-state approaches.
Sentinel-3A/3B orbit determination using non-gravitational force modeling and single-receiver ambiguity resolution
Authors: Mao Xinyuan , Arnold Daniel , Jäggi Adrian
Published: March 2020

Sentinel-3 is an Earth observation satellite formation of the European Space Agency (ESA) devoted to oceanography and land-vegetation monitoring. It operates as a crucial segment of the Copernicus Programme coordinated by the European Union. Up until now, two identical Sentinel-3 satellites, Sentinel-3A and -3B, have been launched into a circular sun-synchronous orbit with an altitude of about 800 km. Their prime onboard payload systems, e.g. radar altimeter, necessitate high-precision orbits, particularly in the radial direction. This can be fulfilled by using the collected measurements from the onboard dual-frequency high-precision multi-channel Global Positioning System (GPS) receivers. The equipped laser retro-reflector allows for external and independent validation to the GPS-derived orbits.

This research will outline the recent Precise Orbit Determination (POD) methodology developments at the Astronomical Institute of the University of Bern (AIUB) and investigate  the POD comparison between Sentinel-3A and -3B satellites. On one hand, a refined satellite non-gravitational force modeling strategy is newly implemented into the BERNESE GNSS software. It consists of comprehensive modeling of atmospheric drag, solar radiation pressure and Earth albedo/radiation pressure based on an 8-plate satellite macromodel. Radiation pressure is modeled considering spontaneous re-emission for non-solar plates. Besides, a linear interpolation between monthly Clouds and the Earth's Radiant Energy System (CERES) S4 grid products is specifically done for the Earth albedo/radiation pressure modeling. On the other hand, use is made of the GNSS Observation-Specific Bias (OSB) products provided by the Center for Orbit Determination in Europe (CODE), allowing for the so-called single-receiver ambiguity resolution.

A test period is selected from 7/Jun/2018 to 14/Oct/2018 (Day of Year: 158-287), when Sentinel-3A and -3B satellites operated in a tandem formation maintained at a separation of about 30 s. This foresees nearly identical in-flight environment for both satellites and thereby enables direct POD performance comparison. The single-receiver (zero-difference) ambiguity-fixed orbit solutions can also be compared with the double-difference ambiguity-fixed baseline solution. Results reveal that the implemented non-gravitational force modeling in POD leads to a reduction of empirical acceleration estimates, which are designated to compensate uncertainties in the satellite dynamic models. Single-receiver ambiguity resolution further improves the reduced-dynamic orbits and significant enhancement occurs to the kinematic orbits. This research implies promising benefits to the Sentinel-3 scientific research community.
Boron isotope systematics of lacustrine carbonates: a new approach for tracing the palaeo-hydroclimatic evolution of the Dead Sea
Authors: Jurikova Hana , Neugebauer Ina , Plessen Birgit , Henehan Michael , Tjallingii Rik , Schwab Markus J. , Brauer Achim , Blanchet Cécile
Published: March 2020

Sedimentary sequences of the Dead Sea provide a unique high-resolution archive of past climatic changes in the Mediterranean-Levant, a key region for human migration out of Africa at the boundary of hemispheric climate belts. The well-preserved record of the Holocene Dead Sea and its Last Glacial precursor Lake Lisan is characterised by annual laminations – varves – composed of alternate layers of aragonite and detritus. Past lake level reconstructions suggest large fluctuations in the regional hydrological balance driven by abrupt climatic events, including a pronounced transition from lake level high-stand during the Last Glacial Maximum (LGM) to a low-stand at the onset of the Holocene [1]. On millennial timescales these changes have been associated with temperature variations recorded in the Greenland ice core, underscoring the potential of the Dead Sea to offer both regional and global perspectives on high-amplitude climatic events in the past. However, our ability to fully read the Dead Sea record critically depends on reliable extraction of palaeo-climatic and palaeo-environmental data from lacustrine carbonates, and an improved understanding of their formation. Here we present carbon, oxygen, boron isotope and trace element composition of hand-picked authigenic aragonite from a Dead Sea deep-drilling core (ICDP 5017-1; [2]) and shore outcrops. While traditionally used as a pH-proxy [3], we examine the possibility of applying boron geochemistry for reconstructing the source water and brine composition [4]. Using our innovative combined approach, we elucidate the palaeo-hydroclimatic evolution of the Dead Sea during intervals of major environmental changes since the end of the LGM.

[1] Torfstein A., et al. (2013) Quat. Sci. Rev. 69, 1–7.
[2] Neugebauer I., et al. (2014) Quat. Sci. Rev. 102, 149–165.
[3] Jurikova H., et al. (2019) Geochim. Cosmochim. Acta 248, 370–386.
[4] Vengosh A., et al. (1991) Geochim. Cosmochim. Acta 55, 1689–1695.
Relocation of seismicity of the Pannonian Basin using the Bayesloc multiple event location algorithm between 1996 and 2019
Authors: Czecze Barbara , Bondár István
Published: March 2020

The objective of this work was to relocate the entire seismicity of the Pannonian Basin with the Bayesloc algorithm, a Markov-Chain Monte Carlo inversion scheme using a Bayesian statistical framework.

In the Hungarian National Seismological Bulletin the magnitudes and event locations are determined with the iLoc location algorithm using the 3D global RSTT velocity model, and we used these locations as initial coordinates. In our work, we have used all of the instrumentally registered seismic events between 1996 and 2019 in the Pannonian Basin.

During data preprocessing we used graph theory to measure data connectivity. Similar to all multiple-event location methods, Bayesloc performs better when events are recorded on a common network.

We used several hundreds of ground truth events (quarry blasts, mine explosions, earthquakes) to tie down the seismicity pattern to known ground truth locations by giving them tighter prior distributions.

Based on the day-time peak on the origin-hour distribution of the bulletin earthquakes we assume that there are anthropogenic events labeled as earthquakes in the catalog, therefore we created a „Suspected explosions (SX)” group to set prior constrains.

The results show that the events around the mines are dramatically better clustered. The prior constraints contributed remarkably to the outcome of the relocation. We show that the results present an improved view of the seismicity of the region.
A multi-spacecraft analysis of energy transfer associated with near-Earth magnetic reconnection
Authors: Fadanelli Sid , Lavraud Benoit , Califano Francesco
Published: March 2020

We present an analysis of energy transfers in a reconnecting near-Earth plasma, obtained by interpreting MMS data within the framework of multi-fluid plasma theory. In our analysis, energy transfers are calculated and examined locally. This way, correlations between different mechanisms of energy exchange can be retrieved in all spatial and temporal detail provided by the high-frequency, multi-point sampling capacity of the four MMS satellites.
In particular, compressional effects are separated from effective sources in the energy density evolution equations, allowing to distinguish whether some effective energy transfer is occurring locally. A large database of MMS encounters with reconnecting current sheets is exploited in order to assess the statistical validity of all results presented.
The horizontal circulation, upwelling and heat budget of the Weddell Gyre: an observation perspective
Authors: Reeve Krissy , Kanzow Torsten , Hoppema Mario , Boebel Olaf , Strass Volker , Geibert Walter , Gerdes Rüdiger
Published: March 2020

The Weddell Gyre is an important region in that it feeds source water masses (and thus heat) toward the ice-shelves, and exports locally and remotely formed dense water masses to the global abyssal ocean. Argo float profiles and trajectories were implemented to capture the large-scale, long-term mean circulation of the entire Weddell Gyre, from which the heat budget has been diagnosed for a layer within Warm Deep Water (WDW), the main heat source to the Weddell Gyre. We show that heat is horizontally advected into the southern limb of the Weddell Gyre, and then removed from the southern limb by horizontal turbulent diffusion (1) northwards towards the gyre interior, and (2) southwards towards the ice shelves. Since the gyre is cyclonic, the heat that is turbulently diffused into the gyre interior is subsequently brought closer to the surface by upwelling. Upwelling is thus an important yet poorly understood feature of the dynamics of the Weddell Gyre. This study marks the beginnings of a project focused on improved understanding of the role of upwelling within the Weddell Gyre, and investigating the role of turbulent diffusion in redistributing heat towards the central gyre interior, as well as towards the ice shelves of Antarctica.
Assessment of gravity and magnetic effects of trap formations in Eastern Siberia
Authors: Gvozdik Sonya , Arutyunyan David , Lygin Ivan
Published: March 2020

Research of Eastern Siberia began after the discovery of hydrocarbons. At the same time, ton the territory of a platform there is the largest trap province in the world - the Siberian province with ubiquitous magmatic bodies of the main composition, which complicate the upper part of the section assessment.

To construct geological sections, borehole data are most often used to determine the power and structure of magmatic complexes. However, drilling cannot provide sufficient details.

Magmatic formations are distinguished by large variations in magnetic properties (from 100 to 1000 * 10-5 SI) and density (from 2.65 to 2.95 g/cm3). They create local gravitational anomalies up to 5-10 mGal, and magnetic ones - from dozens to the first hundreds of nanotests.

With the usage of geological sections as the starting model framework, 2D modeling and selection of the physical properties and geometry of the trap bodies was done. The magnetic field along the profile is set according to the digital model EMAG2 (2009). The gravitational effect was calculated based on the final models, which were assigned density properties.

Modeling of typical sections makes the shape of anomalous sources and supply channels positions more precise. This approach allows to restore the upper part of the section, saturated with trap intrusions.
Integration of spatial fire risk model results into a decision support system – A case study at Laugarvatn, South Iceland
Authors: Hrabalikova Michaela , Traustason Björn , Finger David Christian
Published: March 2020

Iceland is well known for its harsh weather, long winters and frequent geologic activity impacting on the build and natural environment. Although wildfires are rather rare in Iceland, their occurrence might reach a disastrous extent as revealed during the wildfire in 2006. Today, one of the main challenges consist of optimisation landscape planning, disaster and risk management by integrating state-of-art fire models, knowledge in geographical information systems (GIS) and remote sensing. In this study, we present the implementation of simulation results in a decision support system for fire protection. For this purpose, the area of Laugarvatn in South Iceland was selected as a pilot area. Lagarvatn is an ideal pilot area with a high concentration of summer houses and camp caravans surrounded by large-scale natural birch forests. The core of the study is forest fire spread analysis using simulation models and the identification of accessible water sources for firefighting. The input parameters were generated from remote sensing data and GIS databases. Forest types, canopy cover, wind direction and speed and other meteorological variables, topographic feature accelerating forest fire were crucial parameters for producing fire spread probability maps. The fire spread scenario maps, water source maps and road network analysis is one of the critical elements in the decision support system.
Statistical Post-Processing with Standardized Anomalies and Variable Selection for Wind Farm Forecasts
Authors: Dabernig Markus , Kann Alexander , Schicker Irene
Published: March 2020

Numerical weather predictions are often too coarse to represent single turbines in a wind park and post-processing of the individual turbines is necessary. However, individual post-processing can lead to inconsistencies in forecasts for a wind farm. Using standardized anomalies allows to forecast all turbines simultaneously. Therefore, a climatological mean is subtracted from observations/predictions and then divided by a climatological spread which eliminates any site-specific characteristics.

Additionally, different sources of input can be used, such as variables from a global model, a mesoscale model or observations to improve forecasts. However, to prevent overfitting a variable selection method is needed to determine the most important predictors. The combination of standardized anomalies and a variable selection method provides a convenient method for good forecasts of wind farms.
Detection of repeating earthquakes in the West Bohemia swarm region
Authors: Salama Ali , Fischer Tomas
Published: March 2020

 

 

 

Repeating earthquakes, sequences of microseismic events with highly similar seismograms and magnitudes, suggest quasi-periodic rupturing of the same asperity. They are observed on creeping fault segments surrounded by aseismic slip area and also in earthquake swarms. However, so far, they have not been documented in the West Bohemia/Vogtland seismic swarm area. These local swarms consist of thousands of ML < 4 events occurring along a small area of fault zone with repeated activation of some patches during the swarms and weak background activity in the intermediate periods. Detecting and analyzing the repeating earthquakes would help revealing the continuing background activity and identifying fault areas that are active permanently. This could point to the possible sources of fluids or aseismic creep that are supposed to play significant role in swarm generation. Repeating earthquakes are identified by waveform cross-correlation analysis comparing waveforms of repeaters with continuous seismic data set. We developed efficient detection algorithm to identify repeating earthquakes using selected event templates to reveal continuing seismic activity along the main Nový Kostel fault zone, namely in the areas with only episodic activity. The results provide a robust basis for routine application to the long-term seismic dataset that will allow also for further applications including analysis of the source parameters of the repeaters and/or detecting possible seismic velocity variations in the focal zone.

 
Statistical post-processing of wind speed forecasts using convolutional neural networks
Authors: Schmeits Maurice , Veldkamp Simon , Whan Kirien
Published: March 2020

Current statistical post-processing methods for providing a probabilistic forecast are not capable of using full spatial patterns from the numerical weather prediction (NWP) model output. Recent developments in deep learning (notably convolutional neural networks) have made it possible to use large gridded input data sets. This could potentially be useful in statistical post-processing, since it allows us to use more spatial information.

In this study we consider wind speed forecasts for 48 hours ahead, as provided by KNMI's Harmonie-Arome model. Convolutional neural networks, fully connected neural networks and quantile regression forests are used to obtain probabilistic wind speed forecasts. Comparing these methods shows that convolutional neural networks are more skillful than the other methods, especially for medium to higher wind speeds.
Modeling the seismoelectric electrokinetic coupling: a new approach to up-scale the frequency-dependent effective excess charge density
Authors: Jougnot Damien , Solazzi Santiago
Published: March 2020

Seismoelectric signals result from an electrokinetic coupling phenomena that can be modeled through two approaches: the coupling coefficient or the effective excess charge density. The traditional approach is based on the frequency dependent coupling coefficient that can relate differences in pressure to differences in electrical potential. The second approach is more recent and is related to the description of the excess charge that is effectively dragged by the pore water displacement relatively to the mineral surface. In this contribution, we propose a new model to obtain the frequency dependent effective excess charge density. The electrokinetic coupling is mechanistically up-scaled considering the pore as a straight capillary. This approach, called flux-averaging, takes into account the inertial term of the Navier-Stokes equation to explain both the dynamic permeability and the effective excess charge density dependence with oscillation frequency. The frequency dependent coupling coefficient can then be calculated from this result. The model results are then successfully compared to previous models and published data. This work is a first step to predict seismoelectric electrokinetic coupling in much more complicated porous media in saturated and partially saturated conditions.
Earth Observation Data for Agricultural Drought Monitoring in the Pannonian Basin
Authors: Crocetti Laura , Fischer Milan , Forkel Matthias , Grlj Aleš , Ng Wai-Tim , Pasik Adam , Petrakovic Ivana , Salentinig Andreas , Trnka Miroslav , Wild Benjamin , Volden Espen , Dorigo Wouter
Published: March 2020

The Pannonian Basin is a region in the southeastern part of Central Europe that is heavily used for agricultural purposes. It is geomorphological defined as the plain area that is surrounded by the Alps in the west, the Dinaric Alps in the Southwest, and the Carpathian mountains in the North, East and Southeast. In recent decades, the Pannonian Basin has experienced several drought episodes, leading to severe impacts on the environment, society, and economy. Ongoing human-induced climate change, characterised by increasing temperature and potential evapotranspiration as well as changes in precipitation distribution will further exacerbate the frequency and intensity of extreme events. Therefore, it is important to monitor, model, and forecast droughts and their impact on the environment for a better adaption to the changing weather and climate extremes. The increasing availability of long-term Earth observation (EO) data with high-resolution, combined with the progress in machine learning algorithms and artificial intelligence, are expected to improve the drought monitoring and impact prediction capacities.

Here, we assess novel EO-based products with respect to drought processes in the Pannonian Basin. To identify meteorological and agricultural drought, the Standardized Precipitation-Evapotranspiration Index was computed from the ERA5 meteorological reanalysis and compared with drought indicators based on EO time series of soil moisture and vegetation like the Soil Water Index or the Normalized Difference Vegetation Index. We suggest that at resolution representing the ERA5 reanalysis (~0.25°) or coarser, both meteorological as well as EO data can identify drought events similarly well. However, at finer spatial scales (e.g. 1 km) the variability of biophysical properties between fields cannot be represented by meteorological data but can be captured by EO data. Furthermore, we analyse historical drought events and how they occur in different EO datasets. It is planned to enhance the forecasting of agricultural drought and estimating drought impacts on agriculture through exploiting the potential of EO soil moisture and vegetation data in a data-driven machine learning framework.

This study is funded by the DryPan project of the European Space Agency (https://www.eodc.eu/esa-drypan/).
Tectonic History of Hoop Fault Complex, Barents Sea/Norway
Authors: Schuller Volker , Dunkl István , Schleder Zsolt , Stueland Eirik
Published: March 2020

The Barents Sea consists of several tectonic elements which were formed at different plate tectonic collisional and rifting stages. This work focuses on the Early Mesozoic to recent events of the central Barents Sea, the eastern edge of the Bjarmaland platform.

We have analysed the clastic deposits of Mid-Triassic to Upper Jurassic to reconstruct the tectonic history of the Hoop Fault Complex, Barents Sea/Norway. Apatite fission track and (U-Th)/He thermochronology were used to determine the maximum burial depths and exhumation history. According to the combined evaluation of results from shale ductility analysis (BIB-SEM), fault kinematic analysis and structural modelling (section balancing based on a 125 km long 2D seismic section line) the following tectonic evolution can be drawn: deflation of late Palaeozoic salt deposits was initiated by the tectonic activity on the early structures of the Hoop Fault zone. The orthogonal faults of the Hoop Fault Complex developed at the early stage, during Late Triassic to Early Jurassic times at relatively shallow depth, below 1000m. Ongoing subsidence related to the extension caused by the opening of the Atlantic Ocean created accommodation space for Upper Jurassic to Cenozoic deposits with maximum burial depth of 2000 m for the analysed Mid-Jurassic rocks. The exhumation of the Hoop Fault complex started around 10 Ma and remained constant until Quaternary times (140 m/Myr).