bluuebunny/crossref_metadata_2025 huggingface dataset:
Unsupervised classification of the solar wind using Self-Organizing Maps
Authors: Amaya Jorge , Dupuis Romain , Lapenta Giovanni
Published: March 2020

During the past decades different methods of classification of the solar wind have been proposed. These include simple models separating the “fast” from “slow” flows (Arya and Freeman, 1991, Yordanova et al., 2009, among others), complex empirical methods grouping its properties in multiple categories associated to its origin in the solar atmosphere (Xu et Borovsky, 2015), and more recently probabilistic classifications based on Gaussian processes (Camporeale et al., 2017).

Solar wind classification serves four main purposes: 1) statistical analysis of different wind types, 2) interpretation of observations in the magnetosphere, 3) diagnostics of physical processes in the Sun, and 4) identification of solar cycle effects on the Earth’s plasma environment. In this work, instead of using empirical methods, we use the machine learning technique known as Self-Organizing Maps (SOM) to automatically classify the solar wind at 1AU, without human intervention, using observations gathered by the ACE mission.

The ACE spacecraft has been continuously recording solar wind data for the past 22 years. We use hourly averaged solar wind parameters from the ACE Science Center in CalTech for this study. Each entry in this database can be considered as a single point in a multi-dimensional (ND) space. SOM techniques transform all the points in this space into a single 2D space with a small number of L x L nodes. The nodes are the 2D representation of the cloud of points in the ND space, grouping together around each node, points with similar properties. The nodes in this 2D map are interrelated, maintaining a structural topology that is useful for their interpretation. Each one of the nodes in the SOM map can viewed as one of the possible L x L classes. We go one step further, automatically grouping together nodes in the map that are close in the ND space, reducing the total number of classes to only a few. We compare the results obtained using SOM with the methods introduced above, showing the similarities and differences. We show that the SOM technique, which does not rely on human intervention, can be used to properly describe the different types of solar wind conditions observed in a full solar cycle.
Morphology of the Messinian Salinity Crisis surfaces and its related deposits in the Alboran Sea: a continuous Mediterranean-Atlantic connection?
Authors: Do Couto Damien , Estrada Ferran , Gorini Christian , Ercilla Gemma , Suc Jean-Pierre
Published: March 2020

The Messinian Salinity Crisis (MSC), which affected the Mediterranean region during the latest Miocene, is mainly characterized by the deposition of thick evaporites in central basins and strong fluvial erosion of margins. The subaerial fluvial erosion, known as the Messinian Erosional Surface (MES), is for instance continuously followed from the Gulf of Lions up to 360 km from the present-day shoreline upstream the Rhône Valley. Short drainage systems limited by high coastal mountain ranges, must have been significantly affected by the Messinian erosion.

The Alboran Sea is similarly characterized by a geographic context and was the first Mediterranean area concerned by connection-disconnection to the Atlantic Ocean during the last millions years. A recent study suggested that the Alboran Sea remained always connected to the Atlantic Ocean during the MSC, being the marine refuge for the Mediterranean taxa.

In this work, we have performed an extensive research of the MES and MSC-related deposits in the Alboran region, both onshore and offshore, integrating outcrop descriptions, supported by new biostratigraphic data and seismic profile analyses. This study leads to an up-to-date geological and morphological map displaying the actual contours and morphology of the MES in the whole Alboran domain. The MES has a subaerial origin and is continuously followed from land to the offshore domain, sealed by post-MSC marine sediments. Both Spanish and Morrocan sides show three different erosive morphologies: downslope trending paleocanyons cut by a large reflooding channel crossing the entire Alboran basin from the Strait of Gibraltar to Algerian Basin, and alongslope   terraces. The occurrence of all these striking erosive features with basinal extension  questions the hypothesis of the permanent connection with the Atlantic Ocean.
Anisotropy of magnetic susceptibility in alkaline-ultramafic dikes of the Kotuy river valley: Reconstruction of magma transport during the Siberian Traps emplacement
Authors: Latyshev Anton , Chmerev Victor , Zaitsev Victor
Published: March 2020

Products of the Permian-Triassic magmatic activity in the Kotuy river valley consist of two contrasting in composition groups: 1) tholeiitic basalts, similar to the main volume of the Siberian Traps; 2) alkaline-ultramafic rocks which are extremely rare in other regions of the Siberian platform. Alkaline lavas and tuffs in the Kotuy river valley are exposed only in limited area (Arydzhangsky and Khardakhsky formations), however, multiphase circular plutons (Kugda, Odikhincha) and swarms of radial and parallel dikes marks the essentially wider territory of the manifestation of alkaline magmatic activity.

Here we present the preliminary results of the investigation of AMS in the dike complex of alkaline lamprophyres from the Kotuy river valley. The majority of dikes demonstrate I-type of the magnetic fabric, when the medium axes K2 of AMS ellipsoid is orthogonal to the contact of intrusion. In dikes where the minimal axis K3 is subvertical and maximal axis K1 is flat, we interpret this magnetic fabric as a result of cooling of the static magma column after the emplacement in the setting of horizontal extension (Park et al., 1988; Raposo and Ernesto, 1995). Also, N-type and R-type of magnetic fabric were identified as well. In some intrusions, the orientation of the axes of AMS ellipsoid changes from the contact zones to the inner part if intrusion. In this case, we used data from the contact zones for the magma flow reconstruction.

Analysis of the maximal axis K1 orientation in different dikes showed that in majority of bodies it shallowly plunges to the west. This corresponds to the lateral magma flow from west to east during the emplacement. Consequently, formation of the studied dikes is not directly related to Kugda pluton, which is located 8 km eastward. The emplacement of dikes occurred from the magmatic center located westward from the Kotuy river valley and is not associated with any known large massifs. Petrographic similarity of the studied dikes to the lavas of Arydzhangsky formation allows us to suggest that they are coeval. This implies the wider area of manifestation of the Arydzhangsky magmatic stage.

This work was supported by RFBR (projects 18-35-20058, 18-05-70094, 17-05-01121 and 20-05-00573).
Dynamical mechanism of the poleward intensification of the Southern Hemispheric Westerlies due to sea ice extent change
Authors: Kim Hyeong-Gyu , Kim Joowan , Jun Sang-Yoon , Kim Seong-Joong
Published: March 2020

Paleoclimate data shows a good correlation between the concentration of CO2 and atmospheric temperature in the geological timescale. Many studies compare the Last Glacial Maximum (LGM) and the Pre-Industrial era (PI), to understand the coupling processes. A popular mechanism explaining this coupling process is a modulation of the ocean circulation and related CO2 emission over the Southern Ocean due to atmospheric westerly. The atmospheric westerly plays an important role in driving ocean circulation; however, the related processes are not fully understood for the LGM period.

In this study, we examine physical processes determining the characteristics of the atmospheric westerly focusing on the Southern Ocean. Atmospheric states for LGM and PI are reproduced using a coupled earth system model with different sea ice conditions. A poleward intensification of the Southern Hemispheric Westerlies is observed for the LGM experiment. A comparison to PI shows that the meridional temperature gradient largely determines this intensification, and the enhanced meridional gradient is observed due to decreased heat flux from the subantarctic ocean in the LGM experiment. This result suggests that the Antarctic sea ice is a crucial component for understanding the Southern Hemispheric Westerly.
A new molluscan assemblage from the pre-evaporitic Messinian of Crete (Greece)
Authors: Koskeridou Efterpi , Thivaiou Danae
Published: March 2020

The Messinian Salinity Crisis (MSC) was an environmental perturbation with dramatic environmental consequences that greatly affected marine organisms. Messinian deposits are found in several locations around the Mediterranean, but few offer marine faunas rich in molluscs. A section near Heraklion, central Crete, has provided new material that contains a well preserved and rich molluscan fauna that includes many micromorphic species. The section is of early Messinian age, belongs to Agios Miron Formation, and bears several layers of fossiliferous marly sands.

Molluscs from a fossiliferous bed of the section are presented here for the first time. Gastropods and bivalves are most common, but scaphopods and chitons are not infrequent. The assemblage seems to be composed of transported elements from nearby environments and the most frequent species are present in comparable abundances for gastropods and bivalves. The gastropod fauna is represented by Bittium sp. and Gibbula sp., accompanied by Diodora cf. graeca, Turritella sp., Jujubinus sp., species of Pyramidellidae and rarer Homalopoma sp. and Haliotis sp. The presence of Bittium sp. together with Jujubinus sp. suggests vegetated environments. Bivalves are represented by species dwelling mostly in sandy environments such as Glycymeris cf. inflata (also occurring in larger specimens), Spisula sp., Timoclea sp. and various cardiids. Exceptionally well-preserved chitons indicate the presence of hard substrates such as rocks, pebbles or roots of seagrass beds. This is confirmed by the presence of the gastropods Diodora cf. graeca and Haliotis sp.

The assemblage points towards normal salinity shallow marine conditions of sandy bottoms with patches of seagrass-type vegetation before the onset of the MSC.
Tectonic implications of the metamorphic field gradient in the Austrian Drosendorf and Gföhl units, Moldanubian Zone
Authors: Sorger Dominik , Hauzenberger Christoph A. , Linner Manfred , Finger Fritz , Fritz Harald
Published: March 2020

The Moldanubian Zone in Austria is traditionally subdivided into several tectonostratigraphic subunits, which were juxtaposed to their nowadays position during the Variscan orogeny. The Gföhl unit at the highest tectonic position exposes the Moldanubian granulites at the top, underlain by the granitic Gföhl orthogneiss. At its base lies the Raabs unit, a sequence of mafic rocks (amphibolites and sepentinites) accompanied by metasediments. The Drosendorf unit represents a sedimentary sequence mainly consisting of paragneisses, amphibolites and marbles. At the lowest position the Ostrong unit is dominated by low-P paragneisses with local appearances of eclogites.
A comprehensive study along four W–E profiles from the Danube valley (P1) in the south, to the Thaya valley (P4) in the north, revealed a disparate distribution of metamorphic conditions within the Drosendorf and the Gföhl units (Raabs unit and Gföhl orthogneiss). Along P1 several lithologies of the investigated units show similar P–T conditions of 0.8–1.2 GPa and 750–800 °C, followed by a decompression stage to 0.6–0.8 GPa and ~750 °C. Towards the north the temperature within the Drosendorf unit is continuously decreasing to 650–700 °C, at pressure conditions of 0.4–0.8 GPa. P–T conditions for Raabs unit and Gföhl orthogneiss are decreasing as well but are increasing again at P4. At the western end of P4 they reach similar conditions as in P1 (0.6–1.0 GPa and 725–800), but a decrease towards the east can be observed. A slight W–E decreasing trend is also observable in P2 and P3. Th–U–Pb microprobe dating of several metasedimentary and orthogneiss samples resulted in a Carboniferous age (~340 Ma) for metamorphism. At one locality in the south an older monazite generation indicates an incipient collisional metamorphism in the Devonian (~370 Ma).
The observed N–S gradient indicates that the southern parts represent formerly deeper buried lower crustal parts, whereas towards the north middle crustal levels are exposed, which were exhumed in a first stage. In a second stage of exhumation in the northernmost area, the oblique thrusting of lower crustal segment including the Gföhl unit onto the already exhumed lower-middle crustal parts caused the formation of a duplex structure, which is responsible for the present appearance of the area around the Drosendorf window.
The Development of BasinVis: Lessons learned from an open-source collaboration of geoscience and computer science
Authors: Novotny Johannes
Published: March 2020

Geoscience is a highly interdisciplinary field of study, drawing upon conclusions from physics, chemistry and many other academic disciplines. Over the course of the last decades, computer science has become an integral component of geoscientific research. This coincides with the rising popularity of the open-source movement, which helped to develop better tools for collaboration on complex software projects across physical distances and academic boundaries.

However, while the technical frameworks supporting interdisciplinary work between geoscience and computer science exist, there are still several hurdles one must take in order to achieve successful collaborations. This work summarizes the lessons learned from the development of BasinVis from the perspective of a computer science collaborator. BasinVis is a modular open-source application that aims to allow geoscientists to analyze and visualize sedimentary basins in a comprehensive workflow. A particular development goal was to introduce the advances of 2D and 3D visualization techniques to the quantitative analysis of the stratigraphic setting and subsidence of sedimentary basins based on well data and/or stratigraphic profiles.

Development of BasinVis started in 2013 with its first release as a MATLAB GUI application in 2016. Apart from functionality, one of the major problems to solve in this period was the alignment of research goals and methodology, which may diverge greatly between geoscience and computer science. Examples of this would be to clarify the scientific terminologies of each fields early on and to clearly establish the expected results of the application in terms of mathematical accuracy and uncertainty (a concept that may catch computer scientists off guard).
Three-dimensional geometries of relay zones in normal faults
Authors: Camanni Giovanni , Roche Vincent , Childs Conrad , Manzocchi Tom , Walsh John , Conneally John , Saqab Muhammad Mudasar , Delogkos Efstratios
Published: March 2020

Individual normal faults are rarely single planar surfaces and often comprise arrays of fault segments arising from the earliest stages of fault propagation. Current models for the geometry and formation of relay zones between adjacent fault segments have been informed mainly by 2D analysis from either maps or cross-sections observed in outcrop and, to a lesser extent, by the analysis of relay zones from 3D seismic reflection data. Using high quality 3D seismic reflection datasets from a selection of sedimentary basins, we investigate fundamental characteristics of segmentation from the analysis of 67 normal faults with modest displacements (< ca. 190 m) which preserve the 3D geometry of 532 relay zones. Our analysis shows that relay zones most often develop by bifurcation from a single fault surface but can also arise from the formation of segments which are disconnected in 3D. Relay zones generally occur between fault segments that step in either the dip or strike direction, and oblique relay zones with an intermediate orientation are less frequent. This is attributed to the influence of mechanical stratigraphy, and to a tendency for faults to locally propagate laterally and vertically rather than obliquely. Cross-sectional stepping of relay zones typically forms contractional rather than extensional relay zones, a configuration which is attributed to the development of early stage Riedel shears associated with fault localisation. Comparing datasets from different geological settings suggests that the mechanical heterogeneity of the faulted sequence and the influence of pre-existing structure are the underlying controls on the geometrical characteristics of relay zones in normal faults, and different combinations of these two controls can account for the variation in fault zone structure observed between datasets.
Global geodetic parameters obtained from 14 years Lageos 1 Satellite Laser Ranging
Authors: Dimitrov Nikolay , Georgiev Ivan , Ivanov Anton
Published: March 2020

Satellite Laser Ranging (SLR) data of the geodynamic satellite Lageos-1 (LAser GEOdynamics Satellite) for the period January 2000 - June 2013 are processed and analysed through sequential estimation to obtain multiyear solution for global geodetic parameters - coordinates and velocities of 37 stations located on the main tectonic plates. The analysis is carried out with the Satellite Laser Ranging Processor (SLRP) software, version 4.3, developed in the Department Geodesy of the National Institute of Geophysics, Geodesy and Geography at Bulgarian Academy of Sciences. The software consists of two main programs – orbit determination and parameter estimation modules. Total number of 202 447 measurements are processed and analyzed by monthly batches. Arc dependent parameters, geogravitational parameter - GM, Earth Orientation Parameters (pole coordinates and length of the day - LOD), along track and solar radiation pressure coefficients are obtained from monthly solutions. The weighted root mean squares of the monthly station coordinates solution are between 2 and 16 mm. The analysis of monthly GM time series reveal value of the secular trend Ġ/G = -3.31. 10-13yr-1. The results obtained contribute to the monitoring of recent tectonics of the major continental plates and global geodynamic parameters.
Evaluating the impact of different spaceborne land cover distributions on isoprene emissions and their trends using the MEGAN model.
Authors: Opacka Beata , Müller Jean-François , Stavrakou Jenny , Bauwens Maite , Guenther Alex B.
Published: March 2020

The biogenic volatile organic compounds (BVOCs) are emitted globally at about 1100 Tg per year of which almost half of the share is entailed by isoprene. Isoprene is highly reactive in the atmosphere, and its degradation products impact the atmospheric composition through the generation of ozone (in presence of NOx typical of polluted areas) and secondary organic aerosols, and may pose a risk to human health. Isoprene is mainly emitted by plant foliage, with trees being the major contributors due to their relatively high emission factors.

In the modelling framework of biosphere-atmosphere interactions, the representation of land cover and vegetation distributions is a key aspect. We use the state-of-the-art biogenic emission model MEGAN (Guenther et al. 2012) coupled with a multi-layer canopy model MOHYCAN (Müller et al. 2008) to estimate isoprene emissions on the global scale. In its current standard version, the model uses a static plant functional type (PFT) distribution obtained from the Community Land Model (CLM4) for 2000. Our objective is to replace the static map by time-dependent PFT distributions based on satellite global land cover maps, and estimate the resulting biogenic emissions over 2001-2018. To this purpose, we use either the MODIS land cover dataset (Friedl and Sulla-Menashe, 2019), or the MODIS dataset modified to account for tree cover changes from Hansen et al. (2013). Comparisons with the ESA-CCI dataset (Poulter et al. 2015) and the FAOSTAT (www.fao.org) database are performed and the trends over large forested regions are discussed. The comparisons show a large variability in the representation of the tree cover by the available remotely-sensed datasets, leading to different spatial distributions and temporal variability in the estimated isoprene emissions. This gives a measure of the uncertainty associated to this input parameter. This work is conducted in the frame of the ALBERI project that aims at assessing links between biogenic emissions and remotely-sensed photosynthesis indicators, funded by BELSPO through the STEREO III programme.

 

 
Informed water infrastructure design: improving coupled dam sizing and operation by streamflow forecasts
Authors: Castelletti Andrea , Bertoni Federica , Giuliani Matteo , Reed Patrick
Published: March 2020

There is a large body of recent research that is capitalizing on the improved skill of state-of-the-art hydroclimatic services for investigating their value in informing water reservoir operations. Yet, the potential value of these services in informing infrastructure design is still unexplored. In this work, we investigate the added value of hydroclimatic services in the planning of water reservoirs, composed of the joint design of the infrastructure’s size and its operations informed by streamflow forecasts. We demonstrate the potential of our approach through an ex-post design analysis of the Kariba dam in the Zambezi river basin, which is the largest man-made reservoir in Africa. The reservoir is operated for hydropower production and irrigation supply. Specifically, we search for flexible operating policies informed by streamflow forecasts that allow the design of smaller and less costly reservoirs with respect to solutions that do not rely on forecast information. This requires selecting the most informative forecast lead times to use in the dam design phase, which depends on both infrastructural reservoir characteristics and tradeoffs across performance objectives. After estimating the value of perfect forecasts, we analyze its sensitivity with respect to using imperfect synthetic forecasts characterized by different biases. The results show that informing the infrastructure design with perfect streamflow forecasts allows reducing capital costs by 20% with respect to a baseline solution not informed by any forecast, while maintaining the same performance in terms of hydropower production and water supply. Forecast overestimation results in the most critical synthetic forecast bias, reducing their value by 8%. Moreover, our analysis show that forecast value is highly sensitive to reservoir size and operational tradeoffs, ultimately representing a valuable tool for supporting the ongoing planning of 3,700 major dams worldwide.
Future projections of river floods over the European region using EURO-CORDEX simulations
Authors: Di Sante Fabio , Coppola Erika , Giorgi Filippo
Published: March 2020

In a sick world with fever caused by global warming, the hydrological cycle will experience most certainly large changes in intensity and variability. One of the most intense phenomena that will probably be affected by the climate change is the flood hazard. For a long time the stakeholders have been dedicated resources to assess the risk linked to the floods magnitude and frequencies and shaping the public infrastructures based on the assumption of their immutability. Under the effect of the climate change this assumption can be broken and a different approach should be followed to avoid large disasters and threaten to the population health. In this study the biggest ever ensemble of hydroclimatic  simulations has been used to simulate the river floods over the European regions. A river routing model derived from a distributed hydrological model (CHyM) has been forced with 44 EURO-CORDEX, 5 CMIP5 and 7 CMIP6 simulations to assess the effects of the climate change on the floods magnitude under two different scenarios (RCP2.6 and RCP8.5 for EURO-CORDEX and CMIP5, SSP126 and SSP585 for CMIP6). The impact of the climate change has been evaluated using a 100 year return period discharge indicator (Q100) obtained fitting a Gumbel distribution on the yearly peak discharge values. Results show a decrease of magnitude of flood events over the Mediterranean, Scandinavia and the North Eastern European regions. Over these two last regions the signal appear particularly robust and in contrast to the projected mean flow signal that is shown to increase by the end of the century mainly driven by the related increase of mean precipitations. The reduction of snow accumulation during winter time linked to a large increase of late winter temperatures is the main reason behind the decrease of floods over the North Eastern regions. An opposite signal is projected  instead over Great Britain, Ireland, Northern Italy and Western Europe where a robust signal of floods magnitude increase is evident driven by e the increase of extreme precipitations. All these simulation are meant to feed the impact community and to shade the light on the use of climate information for impact assessment studies.
Complex soil mass redistribution along a catena using meteoric and in-situ 10Be as tracers
Authors: Calitri Francesca , Egli Markus , Sommer Michael , Tikhomirov Dmitry , Christl Marcus
Published: March 2020

In hilly and mountainous landscapes, the bedrock is actively converted to a continuous soil mantle. The bedrock-soil interface lowers spatially at the soil production rate, and the soil acts as a layer removing sediment produced locally and transported from upslope. Forested soils of a hummocky ground moraine landscape in Northern Germany exhibit strongly varying soil thicknesses with very shallow soils on crest positions and buried soils at the footslope. We explored the explanatory power of both 10Be forms (in situ and meteoric) for forest soils on a hillslope to shed light into the complex mass redistribution. Our main research questions were: how do meteoric and in-situ 10Be compare to each other? What do they really indicate in terms of soil processes (erosion, sedimentation, reworking)? By using both types of 10Be, the dynamics of soils and related mass transports should be better traceable. Both 10Be forms were measured along three profiles at different slope positions: Hydro1 (summit), Hydro3 (shoulder), Hydro4 (backslope). Furthermore, a buried horizon was found in the profile Hydro4 at 160 cm depth and 14C-dated. The distribution pattern of meteoric 10Be of Hydro4 shows an inverse exponential depth profile, and an almost uniform content of in-situ 10Be along the profile. Meteoric 10Be indicates on the one hand that a new soil was put on top of an older, now buried soil. On the other hand, meteoric 10Be is involved in pedogenetic processes and clearly exhibits clay eluviation in the topsoil and clay illuviation in the subsoil. The uniform content of the in situ 10Be shows soil mixing that must have occurred during erosion and sedimentation. The14C dated buried soil horizon indicates a deposition of eroded soil material about 7 ka BP. Consequently, an increase in the in-situ 10Be content towards the surface should be expect which however was not the case. The reason for this is so far unknown. Radiocarbon dating and 10Be data demonstrate that strong events of soil mass redistribution in Melzower Forest are mainly a result of ancient natural events. Further measurements of fallout radionuclides (239+240Pu) showed no erosion for the last few decades in the same catchment.
Analysis of river training in Qareaqaj River in Iran: Application of RiMARS
Authors: Jalali Shahrood Abolfazl , Torabi Haghighi Ali , Menberu Meseret , Darabi Hamid , Klöve Björn
Published: March 2020

Erosion and sedimentation play a significant role in river morphology and are among the most important issues in river engineering. Riverbank protection is one of the common efforts in river engineering to stop or reduce the rate of side erosion in rivers. Riprap is one of the simplest and most economical river protection methods due to construction material availability, operation simplicity, flexibility, easiness to construct and repair.  Anthropogenic disturbances could have several side effects in rivers and subsequently induce a change in river morphology. Hence, morphological analysis is needed to trace the history of channel formation and forecast future changes. Riprap is widely used in the Southern parts of Iran to save the rural and agricultural areas located along the river. The Qareaqaj River is one of the major rivers in the South of Iran that is affected by side erosion in many places due to its high meandering morphology. Hence, a riprap structure was constructed in 2006 to protect the Qasr Ahmad village located in the right bank of the Qareaqaj River. The objective of this study is to evaluate how the river training has affected the channel morphology for 18 years in a 10 Km stretch (5 km above and 5 km below the riprap structure). Five Landsat multispectral images captured in 1995, 1999, 2003, 2010, and 2013 were used as input in the RiMARS (River Morphodynamics Analysis method based on Remote Sensing data) for morphological analysis. The Sinuosity Index (SI) has been estimated for meanders for 18 years and the results indicated that most meanders along the stretch are classified as twisty (about 36%), meandering (22%) and winding (18%). Furthermore, the river is divided into ten sections along the flow path and temporal migration of each section is separately analyzed. The river in its halfway (where the riprap was constructed) has migrated on average by 12.5 m, 2.2 m, 5.5 m, and 9 m in 1999, 2003, 2010, 2013, respectively, when compared to the year 1995. The maximum rate of river migration was observed (6.5 m per year) during 2010-2013 at the 7th decile of the stretch, which is about 2000 m below the protected area. The results clearly indicated that the migration rates increased in the downstream of the riprap protected area after the construction date.
Communication channels to build a stronger PEEX network
Authors: Buenrostro Mazon Stephany , Borisova Alla , Altimir Nuria , Mahura Alexander , Lappalainen Hanna K.
Published: March 2020

In a transdisciplinary and pan-region programme like PEEX, building a strong communications platform with an efficient reach across countries is vital to foster collaborations, announce local findings or events to a wider audience, and build a sense of international community. In addition to its website, PEEX offers a quarterly e-newsletter and online Blog to its community.

The PEEX e-newsletter is sent to ~650 international subscribers, where the majority of readers come from Russia, China, Northern Europe and the USA. It is particularly important given that China and Russia have their own national social media channels like Weebo, WeChat and VK, which are popular alternatives to Twitter, Facebook or Instagram. Thus, having an online platform that integrates readers from Russia and China is vital for information exchange.

In addition to having an international readership, your article contribution to the PEEX Blog and e-newsletter facilitates your own efforts of dissemination. All articles have their unique web link, hosted in the PEEX blog, and hence can be embedded in your own research group’s website, news, social media accounts, etc.

The PEEX blog and newsletter welcomes articles from early career scientists. Great examples of these include field work stories that communicate the research aim but also the infrastructure or instrumentation available across the PEEX domain. Additionally, it provides a training opportunity for students to write popular scientific articles.

UArctic and FutureEarth are both partner programmes of PEEX. As the PEEX newsletter evolves, the aim is to integrate more overlapping relevant news and opportunities across these partners. Presently, UArctic shares the PEEX newsletter among its channels, as part of the thematic network the Arctic Boreal Hub.

Expanding the offer of channels for dissemination within the PEEX community and overall public will allow us to discuss science in a more collaborative, open and inclusive manner.
Pacific Water Pathways through the Arctic Ocean
Authors: Dodd Paul A. , Hattermann Tore , Karcher Michael , Kauker Frank , Stedmon Colin
Published: March 2020

The volume, characteristics and sources of freshwater circulating in the Arctic Ocean vary in time and are expected to change under a declining sea ice cover, influencing the physical environment and Arctic ecosystem. Relatively fresh (S = 32) Pacific Water, which enters the Arctic Ocean via the Bering Strait makes up a significant part of the liquid freshwater exiting the Arctic Ocean through Fram Strait. If transported to the Nordic Seas and North Atlantic via the East- and West Greenland Currents freshwater from the Pacific could have an effect on convection and dense water formation in those regions.

More than 30 repeated sections of nutrient measurements have been collected across Fram Strait between 1980 and 2019. The fraction of Pacific Water along these repeated sections can be estimated from the ratio of nitrate to phosphate. The time-series of repeated Fram Strait sections indicates that the fraction of Pacific Water passing out of the Arctic Ocean has changed significantly over the last 30 years. Pacific water fractions remained high from 1980 to 1998, but in 1999 Pacific water almost disappeared from Fram Strait, reappearing from 2011 to 2012, when there was a peak in freshwater export though Fram Strait.

Several hypotheses suggest how variations in the large-scale atmospheric circulation over the Arctic Ocean may influence the transport and pathways of Pacific Water. We show how anomalies in reanalysis wind fields are associated with the reappearance of Pacific Water in Fram Strait in recent years. Repeated sections across Fram Strait are compared with sea ice back-trajectories in the Polar Pathfinder 4 product and a simulated Pacific Water tracer in the NAOSIM numerical model to investigate likely Pacific water pathways through the Arctic Ocean and upstream drivers of changes observed in Fram Strait.
What drives the Arctic response to mid-latitude sulphate aerosol emissions?
Authors: Krishnan Srinath , Ekman Annica , Hansson Hans-Christen , Riipinen Ilona
Published: March 2020

Modeling studies have shown that changes in sulphate aerosol emissions from both Europe and North America can have an impact on remote Arctic climate. The bulk of this response is driven by atmospheric changes, rather than through changes in meridional ocean heat transport. However, these simulations have focused on the Arctic response from an equilibrium perspective; i.e. the simulations are run for 200 years and the analyses are based on means of the last 50 years. While these simulations are useful to analyze the extent of contribution of mid-latitude aerosol emission changes, they cannot be used to investigate the mechanistic processes that initiate and drive the high-latitude response. We approach this problem by conducting two sets of initial condition ensemble simulations with >30 members for each set and focus our analysis on the first 30 years. Having a large number of ensemble members improves the signal-noise ratio and allows us to distinguish the model response to emission changes from internal variability. In the first set of simulations (control set), the aerosol emissions are set to year 2000. In the second set of simulations (perturbed set), we increase the European sulphate aerosol emissions to seven times the year 2000 value. We compare the two sets of simulations to evaluate the dynamical response of the atmosphere to the change in aerosol emissions. One of the key parameters that link the mid- and high-latitudes in the equilibrium response is the change in sea-ice area in the sub-polar latitudes. Reduced sea-ice coverage and greater open ocean area with lower mid-latitude aerosol emissions leads to increased ocean-atmosphere energy exchange and impacts the atmospheric meridional heat and energy budgets in the Arctic. We present the extent and seasonality of sea-ice changes for the first 30 years of our ensemble simulations and discuss their implications in the context of the mechanistical links between the mid- and high-latitudes.

 
Simulated hailstorms over Switzerland in May 2018 in current and future climate conditions
Authors: Martynov Andrey , Raupach Timothy , Martius Olivia
Published: March 2020

Several remarkable hailstorms have occurred on the territory of Switzerland during the month
of May, 2018.
This period has been simulated, using the WRF4.0 model at a convection-permitting
resolution (1.5 km), using different microphysical schemes (Thompson, Morrison, P3).
The surrogate climate change approach has been used for imitating the climate conditions,
corresponding to the end of the 21st century (CMIP5 model data, RCP8.5 scenario).
The HAILCAST-1D model output has been used as a measure of simulated hail size and 5-
minute 3-D radar reflectivity field has been used for cell identification and tracking.
Hailstorms produced in the current climate and in surrogate climate change simulations have
been examined using neighborhood methods and a storm-tracking algorithm. Current-climate
simulated hailstorms were compared with the ground observations and MeteoSwiss radar
data.
The influence of microphysical schemes to the characteristics of simulated hailstorms has
been studied. 
High volumes of mineral dissolution by localized fluid pulses in UHPM metasediments of Lago di Cignana, Western Alps
Authors: van Schrojenstein Lantman Hugo , Wallis David , Scambelluri Marco , Alvaro Matteo
Published: March 2020

Fluids play key roles in many geological processes across wide ranges of spatial and temporal scales. A major challenge in establishing the impacts of fluids is that partial replacement of minerals by dissolution-precipitation produces gaps in the rock record. Finding the records of such processes can help in understanding and reconstructing the processes of fluid flow, mineral dissolution and related volume changes.

The ultra-high pressure metamorphic (UHPM) Lago di Cignana Unit (Zermatt-Saas Zone, Western Alps) has been intensively studied because it is a piece of exhumed coesite- and diamond-bearing oceanic lithosphere. In this unit, schistose quartzite hosts coesite-bearing garnet and contains lenses of garnetite, which previously have been attributed to local bulk-compositional differences. Almost the entire quartzite consists of a retrograde mineral assemblage, and therefore processes occurring during subduction are best recorded in garnet.

A combined microstructural and petrological study of the garnetite lenses and their host rock reveals evidence for compaction by dissolution during subduction, partially driven by intergranular pressure solution. As the host rock matrix is removed, garnet is preferentially preserved and concentrated into garnetite. Garnet-garnet contacts then result in pressure solution and grain boundary migration. Different garnet densities and microstructures in the garnetite, alongside dissolution-reprecipitation structures in host rock garnet, suggest a complex process driven by fluid pulses. Linking garnet composition and structures to P-T through barometry on inclusions reveals an evolving fluid pathway during prograde to peak metamorphism, resulting in significant mass removal by pressure solution in metasediments subducted to UHPM conditions.

The occurrence of pressure solution and mass removal at UHPM conditions in combination with the large amounts of fluids produced by slab dehydration suggests that dissolution may play a significant role in metasediments during subduction.

 

Acknowledgements: This project has received funding from the European Research Council under the H2020 research and innovation program (N. 714936 TRUE DEPTHS to M. Alvaro)
Numerical Simulation of Squall line in idealized SINGV and WRF Models
Authors: Rajagopalan Ragi , Dipankar Anurag , Huang Xiang-Yu
Published: March 2020

Squall lines are the prominent feature over Singapore region creating strongly localized rain events due to vigorous localized convective activity. These convective systems have relatively small spatial and temporal scales compared to other atmospheric features like monsoons, thus the prediction of these features lack accuracy. The SINGV numerical weather prediction model is able to provide improved weather forecasts over Singapore region, however, challenges still exist in predicting the thunderstorm/squall line events in onset, location, intensity and lead time. A few real-time case studies of squall lines indicate that SINGV could not capture these features appropriately, while WRF did a better forecasting. To understand the issues with SINGV model, idealized simulations replicating the Weismann & Klemp ‘82 case are conducted keeping similar physics in both the models. Preliminary results indicate that both models behave differently: WRF displays organized convection whereas in SINGV the storm splits at the early stages. Cross-sectional details along the propagating squall line suggest that the updrafts and downdrafts, at the storm development stages, are moderately higher in SINGV compared to WRF. It is speculated that these stronger updrafts in SINGV carry anomalously large amount of liquid water to the upper troposphere where these are converted into rain, which in turn result in stronger downdrafts facilitating the splitting of initial storm. Further analysis is required to conclude our speculation.
Global Glacier Mass Loss estimated from GRACE and GRACE-FO Satellite Observations (2002-2019)
Authors: Wouters Bert , Gardner Alex , Moholdt Geir , Sasgen Ingo
Published: March 2020

Glaciers outside of the ice sheets are important contributors to sea level rise. Although their overall mass balances can be estimated by upscaling local field measurement, direct observations with global coverage are only feasible with satellite remote sensing.  Satellite gravimetry of the Gravity Recovery and Climate Experiment (GRACE) showed that between 2002 and 2016, glaciers lost mass at a rate of 199 ± 32 Gt yr−1, equivalent to a cumulative sea level contribution of 8 mm. After about one year of interruption following the end of the GRACE science operations in June 2017, GRACE Follow-On (GRACE-FO) now allows us to extend the time series of its predecessor starting June 2018.

In this work, we provide updated estimates of the global glacier annual mass balance for 2002 and 2019 based on GRACE/GRACE-FO, and present regional changes with a focus on recent years. Furthermore, we discuss the different uncertainties entering our mass balances and compare our estimates to those based on upscaling in-situ measurements.
Multiphysics of transient deformation processes leading to macroscopic instabilities in geomaterials
Authors: Jacquey Antoine , Regenauer-Lieb Klaus , Parisio Francesco , Cacace Mauro
Published: March 2020

Material instabilities are critical phenomena which can occur in geomaterials at high stress and temperature conditions. They generally result in the degradation of the microstructure organisation, ultimately leading to material failure. These phenomena are relevant to a large variety of geoscientific and geotechnical applications including earthquake physics, fault mechanics, successful targeting of unconventional georesources and mitigation of induced seismicity. Quantifying and predicting the onset of material degradation upon instability remains a major challenge due to our lack of understanding of the physics controlling the behaviour of porous rocks subject to high temperature and pressure conditions.

In the laboratory, rocks gradually transition from a time-independent brittle behaviour to a transient semi-brittle, semi-ductile behaviour upon an increase in pressure and/or temperature. Furthermore, even when subject to constant subcritical stress conditions rocks have been observed to macroscopically fail due to growth of subcritical processes such as stress corrosion. Brittle creep is a phenomenon observed on a variety of rock types (volcanic and sedimentary) and shows a high sensitivity to temperature and stress conditions. In the field, such subcritical transient processes are difficult to detect and can jeopardise the safety of geothermal projects. Transient failure mechanisms in the reservoir have set back geotechnical projects through induced seismicity occurring days or even weeks after stimulation shut in as observed at the Basel geothermal site in Switzerland or at the Pohang geothermal project in South Korea. These observations demonstrate how conventional techniques fail at describing the physics responsible for fault reactivation, which is controlled by dynamic processes resulting from transient multiphysics coupling.

In this contribution, we detail the theory and procedure to develop a constitutive model for rate-dependent damage poro-elasto-plastic material behaviour suitable for porous rocks. To allow for a generic framework for assessing geomaterials instabilities, this model incorporates the potential for microstructure degradation and a path- and rate-dependence. To that purpose, we rely on thermodynamic principles to derive in the frame of the hyperplasticity theory a coupled hydro-mechanical rate-dependent plasticity and damage rheology. We present numerical examples of this new constitutive model at the laboratory scale using experimental data on brittle creep in sandstones and discuss the implications upon upscaling at the reservoir and lithosphere scale.