bluuebunny/crossref_metadata_2025 huggingface dataset:
The rise of high mountain peaks: Feedbacks between orographic precipitation, fluvial erosion and flexural isostasy
Authors: Robl Jörg , Hergarten Stefan
Published: March 2020

The majority of the highest mountain peaks on Earth is located at the dissected rim of large orogenic plateaus such as the Tibetan Plateau or the Altiplano. The striking spatial coexistence of deep, incised valleys and extraordinary high peaks located at the interfluves led to the idea of a common formation even a hundred years ago: focused erosion in valleys triggers the rise of mountain peaks due to erosional unloading and isostatically driven uplift. Ridgelines rise at the interfluves parallel to major rivers, but an additional ridgeline forms perpendicular to the principal flow direction separating the dissected rim from the undissected center of the plateau. As major rivers originate within the plateau and bypass the highest peaks, the latter rigdeline does not form a principal drainage divide. However, it forms a strong orographic barrier with wet conditions at the windward and dry conditions towards the plateau center at the leeward side. The height of the ridgeline is controlled by valley incision via erosional unloading and isostatic uplift.  If the precipitation pattern responsible for localized valley incision is controlled by the geometry of orographic barriers, a series of complex feedbacks between precipitation, erosion and ridgeline uplift (including the evolution of the highest peaks) occurs.

In this study, we present first results of a novel numerical model, which couples (a) fluvial erosion based on the stream power law, (b) flexural isostasy including viscous relaxation and (c) orographic precipitation based on the advection and diffusion of moisture and its reaction on topographic barriers. Originating from a simple model setup with a plateau in the center of the model domain and moisture transported along a predominant wind direction, we explore the co-formation of valleys and the rise of ridgelines including the growth of extraordinary high peaks. As the evolving topography controls the precipitation pattern, erosion rates are high at the wet windward side of the ridgeline, which parallels the plateau rim, while the leeward side towards the plateau center is characterized by low precipitation and very low erosion rates. As it prevents elevated low-relief areas from dissection, we suggest that this mechanism is a principal cause for the longevity of orogenic plateaus.
Impacts of hydrogeological heterogeneity on groundwater transit time
Authors: Rahman Mostaquimur , Hartmann Andreas
Published: March 2020

Groundwater transit time refers to the travel time of a water molecule through an aquifer from recharge at the water table to discharge at a surface water body (e.g., river). Analysing transit times provides a primary way to understand the overall transport characteristics of a hydrological system and is of interest in many aspects of environmental management. For example, studying transit time distribution can facilitate the mitigation of pollutant transport risks and ecosystem restoration. Hydrogeological heterogeneity of an aquifer is a major controlling factor for groundwater flow paths and transit time distributions. In this study, we investigate the impacts of spatial variability of hydrogeological properties on transit times by combining measurements and a new semi-analytical numerical modelling scheme. Passive tracer transport data from several catchments in Europe are obtained from open databases. Groundwater transit time in these catchments are inferred from both tracer transport data and numerical modelling. Comparing the results in different catchments provides a comprehensive way of understanding the impact of hydrogeological heterogeneity on groundwater transit time.
An objective definition of seasons for the Mediterranean region based on synoptic weather types
Authors: Kotsias George , Lolis Christos , Hatzianastassiou Nikolaos , Lionello Piero , Bartzokas Aristides
Published: March 2020

An objective definition of seasons for the Mediterranean region is performed based on the intra-annual variation of the frequencies of eight (8) objectively defined synoptic Weather Types (WTs). The data used for the determination of the 8 WTs are daily NCEP/NCAR Reanalysis grid point values of 2m air temperature, total cloud cover, 2m zonal and meridional wind components, 500hPa and 1000hPa geopotential height, 500hPa and 850hPa air temperature, 850hPa specific humidity and precipitable water over the Mediterranean region, for the period 1949-2018. Firstly, Principal Component Analysis (PCA) is applied to the inter-annual variations of the above parameters in order to reduce the dimensionality and then k-means Cluster Analysis (CA) is applied to the resultant Principal Components (PCs) in order to group dates with similar patterns of the above parameters, resulting in 8 synoptic WTs. Then, PCA and CA are applied again, now on the intra-annual variations of the frequencies of the resultant WTs and group dates of the year (seasons) with similar frequency distribution among the 8 WTs. According to the results, four (4) seasons are defined for the 70-year period 1949-2018. The same methodology is applied also for the five overlapping 30-year sub-periods 1949-1978, 1959-1988, 1969-1998, 1979-2008 and 1989-2018, leading to 4 seasons too. Although the characteristics of these seasons generally correspond to the ones of the four conventional seasons, there are differences regarding the onset and cessation dates and the duration. In general, it is found that winter and summer last about 4 months (115 and 114 days respectively), spring has a duration of about 2.5 months (72 days) and autumn lasts about 2 months (64 days). The most remarkable long-term changes of the seasons’ characteristics are: (i) the colder winters and warmer autumns during the last decades, (ii) the shortening of winter and spring due to later onset and earlier cessation dates, respectively, and (iii) the extension of autumn and summer due to later cessation and earlier onset dates, respectively.
Combined use of Sentinel SAR and optical data for soil moisture estimation
Authors: Graldi Giulia , Bignotti Simone , Bezzi Marco , Vitti Alfonso
Published: March 2020

This work investigates the performance of two soil moisture retrieval methods using optical and radar satellite data. The study was conducted in areas with predominant agricultural land use since soil moisture is one of the parameters of interest in a wider study for water resource optimization in agricultural practices such as irrigation scheduling.
The two methods considered are based on the identification of changes in the investigated parameter between two acquisition dates. The implemented methods have been applied to study areas characterized by different orographic complexity and land use heterogeneity. Data from the European Space Agency (ESA) Sentinel 1 and Sentinel 2 missions were used, and results were validated with field measurements from the International Soil Moisture Network (ISMN).
At first, the methods were applied in a mountainous area of an irrigation consortium in Trentino (Italy), where the results pointed out the complexity of the study and the limitations of the current models in these contexts. Factors such as orographic complexity, type and physiological state of crops make the reduction of SAR data particularly complex to model.
The methods were then tested in a simpler orographic context such as that of the Po Valley in Bologna (Italy), also characterized by agricultural land use.
Finally, the methods were applied in a lowland with agricultural vocation located in Spain, for which an extended archive of soil moisture measurements distributed by the ISMN is available. In this context, the models were analyzed and were evaluated both functional and parametric adjustments of the models on the basis of the previous case studies.
Some of the results obtained are of high quality, while others highlight the complexity of the problem faced and the need for further investigation: increasing the number of case studies and using optical or SAR vegetation index different from the mainly used NDVI, could enhanced the models used for soil moisture retrieval.
Multifractal analysis of velocity and temperature fluctuations in the atmospheric surface layer
Authors: Sahoo Ganapati , Bhattacharjee Soumak , Vesala Timo , Pandit Rahul
Published: March 2020

The characterization of the structure of non-stationary, noisy fluctuations in a time series, e.g., the time series of the velocity components or temperature in turbulent flows, is a problem of central importance in fluid dynamics, nonequilibrium statistical mechanics, atmospheric physics and climate science. Over the past few decades, a variety of statistical techniques, like detrended fluctuation analysis (DFA), have been used to reveal intricate, multiscaling properties of such time series. We present an analysis of velocity and temperature time series, which have been obtained by measurements over the canopy of Hyytiälä Forest in Finland.
In our study we use DFA, its generalization, namely, multifractal detrended fluctuation analysis (MFDFA), and the recently developed multiscale multifractal analysis (MMA), which is an extension of MFDFA. These methods allow us to characterize the rich hierarchy or multi- fractality of the dynamics of the time series of the velocity components and the temperature. In particular, we can clearly distinguish these time series from white noise and the signals that display simple, monofractal, scaling with a single exponent (also called the Hurst exponent). It is useful to recall that monofractal scaling is predicted for fluid turbulence at the level of the Kolmogorov’s phenomenological approach of 1941 (K41); experiments and direct numerical simulations suggest that three-dimensional (3D) fluid turbulence must be characterised by a hierarchy of exponents for it is truly multifractal.

We present an analysis of multifractality of velocity and temperature fields that have been measured, at different heights, over the canopy of Hyytiälä Forest in Finland. In particular, we carry out a detailed study of velocity and temperature time series by using MFDFA and MMA. Results from both these methods are consistent, as they must be; but, of course, the MMA results contain more information because they account for the dependence of the multifractality on the time intervals.
Integrating less represented countries into the mainstream of European geosciences
Authors: Dósa Melinda , Timár Anikó , Heward Anita
Published: March 2020

In order to build a diverse, inclusive community of geoscientists within Europe, a statistical study is carried out based on participation statistics of different conferences in Europe over the past five years. Data of geoscience conferences (EGU, IUGG), planetary (EPSC) and solar-terrestrial science conferences (ESWW, ESPM) are investigated. Special focus is given to the historical division between Eastern and Western Europe and senior and junior scientists. The aim is to show that the geographical division continues to exist and does not show a general improving trend, while the position of the younger generation seems to improve. Some “success cases” defying the usual trend are shown and analysed in detail. We suggest some reasons behind the statistics and draw some lessons that can help integrating less represented researchers into the mainstream of European geosciences.
What makes a rock glacier? Insights into the structure and dynamics of an active rock glacier on the Tibetan Plateau
Authors: Buckel Johannes , Reinosch Eike , Krebs Nora , Voigtländer Anne , Dietze Michael , Schroeckh Ruben , Bücker Matthias , Hördt Andreas
Published: March 2020

Rock glaciers are typically regarded as periglacial features and their dynamics are supposed to be driven by ice content. Under ongoing global warming we expect these structures and dynamics to change and at least decay. This would be especially the case of rock glaciers in climate-sensitive high mountains of the Tibetan plateau, like in the Nyainqêntanglha range. Despite the similar past and present periglacial climatic conditions in this region, rock glaciers are only formed in a few, specific valleys. With this study, we aim to provide insights into the environmental conditions under which rock glaciers are formed and maintained, to be able to better understand how they will respond to changing boundary conditions, imposed by global warming.

To assess “what makes a rock glacier?” we studied such a feature in the Qugaqie basin, at 5500 m a.s.l. To describe the structure and the dynamics of this active rock glacier we applied several methods (geomorphological mapping, geophysics, remote sensing) and we incorporated catchment area properties such as geology, water and sediment sources. Mapping of the geomorphology, the geology and surface material properties characterizes the external structure of the rock glacier. The internal structure, like the active layer zone and the existence of ice, is described by electrical resistivity tomography (ERT). To investigate the surface dynamics of the rock glaciers, we quantify displacement rates using Interferometric Synthetic Aperture Radar (InSAR) time-series analysis. To gain insight to internal deformation dynamics we use environmental seismology, allowing for detection and location of crack signals within the rock glacier. The seismic network also allows tracking rock falls at the head scarp and continuously monitoring glaciofluvial patterns. We find that the singularity of the presence of the studied rock glacier is most likely related to a specific melange of the geological structures, former glaciation of the valley, catchment size and shape and especially water availability.
Earth System Music: music generated from the first United Kingdom Earth System model
Authors: de Mora Lee , Sellar Alistair , Yool Andrew , Palmieri Julien , Smith Robin S. , Kuhlbrodt Till , Parker Robert J. , Walton Jeremy , Blackford Jeremy C. , Jones Colin G.
Published: March 2020

With the ever-growing interest from the general public towards understanding climate science, it is becoming increasingly important that we present this information in ways accessible to non-experts. In this pilot study, we use time series data from the first United Kingdom Earth System model (UKESM1) to create six procedurally generated musical pieces and use them to explain the process of modelling the earth system and to engage with the wider community. 

Scientific data is almost always represented graphically either in figures or in videos. By adding audio to the visualisation of model data, the combination of music and imagery provides additional contextual clues to aid in the interpretation. Furthermore, the audiolisation of model data can be employed to generate interesting and captivating music, which can not  only reach a wider audience, but also hold the attention of the listeners for extended periods of time.

Each of the six pieces presented in this work was themed around either a scientific principle or a practical aspect of earth system modelling. These pieces demonstrate the concepts of a spin up, a pre-industrial control run, multiple historical experiments, and the use of several future climate scenarios to a wider audience. They also show the ocean acidification over the historical period, the changes in circulation, the natural variability of the pre-industrial simulations, and the expected rise in sea surface temperature over the 20th century. 

Each of these pieces were arranged using different musical progression, style and tempo. All six pieces were performed by the digital piano synthesizer, TiMidity++, and were published on the lead author's YouTube channel. The videos all show the progression of the data in time with the music and a brief description of the methodology is posted alongside the video. 

To disseminate these works, links to each piece were published on the lead author's personal and professional social media accounts. The reach of these works was also analysed using YouTube's channel monitoring toolkit for content creators, YouTube studio.
Autumn Arctic predictors and predictions for winter marine cold air outbreaks over the Barents Sea
Authors: Polkova Iuliia , Afargan-Gerstman Hilla , Domeisen Daniela , King Martin , Ruggieri Paolo , Athanasiadis Panos , Dobrynin Mikhail , Baehr Johanna
Published: March 2020

The air temperature over Arctic sea ice can fall strongly below 0°C, while for adjacent areas of open water, sea surface temperature remains close to freezing. This creates a strong temperature gradient across the sea ice edge. Transports of cold air masses from the sea ice toward open ocean water, known as marine cold air outbreaks (MCAOs), modify vertical stability of the atmospheric column and thus can create conditions favorable for the formation of hazardous maritime cyclones (polar lows), which pose risks to marine and coastal infrastructure and society. For marine management, MCAO predictions would be highly beneficial. Previous studies analyze the genesis of MCAOs, while predictability and large-scale drivers of MCAOs remain poorly understood. 

We investigate (i) the ability of the Earth System Model from the Max-Planck Institute for Meteorology (MPI-ESM) to predict MCAOs at a seasonal timescale and (ii) options to improve predictability of MCAOs through their large-scale drivers. To identify MCAO preconditions, we utilize the atmospheric reanalysis ERA-Interim using lagged cross-correlation analysis, composite analysis, and causal effect network (CEN).

Our results show that the MPI-ESM has high prediction skill for MCAOs over the Barents Sea (BS), Greenland-Iceland-Norwegian Seas and the Labrador Sea for about 2-2.5 weeks ahead starting from the November and February initial conditions. This holds for the prediction skill analyzed from daily model output. For MCAO properties such as extreme MCAO values occurring during a month, or the frequency of MCAO events per month, we find high prediction skill for up to a month ahead. Whereas the lagged cross-correlation analysis indicates a relationship between September and October atmospheric circulation and sea ice conditions with November BS-MCAOs, the CEN identifies the causal link only from the Arctic sea ice cover.
Photosynthesis - Solar Induced Fluorescence relationships in polar ecosystems
Authors: Maseyk Kadmiel , Croft Holly , Rogers Cheryl , Zenone Terenzio , Oechel Walter , Zona Donnatella
Published: March 2020

The rapid warming of polar regions is having a demonstrable impact on ecosystem composition and there is a pressing need to understand the carbon cycle implications of these changes. A promising approach for investigating photosynthesis at ecosystem and regional scales involves the remote sensing of Solar Induced Fluorescence (SIF). However, ground-validation of SIF and its association with carbon assimilation and other ecophysiological parameters is largely missing from the polar regions. We will present results of measurements of ground-level SIF and hyperspectral reflectance that were coupled with CO2 exchange measurements in three contrasting polar regions: shrub and bog ecosystems in northern Sweden, wet coastal tundra in Alaska and moss turf in Antarctica. We show good agreement between SIF and photosynthesis across scales, from leaf-level to surface fluxes, but with variable relationships between ecosystem types. Our results show strong potential for using SIF to help understand the impact of change in these regions.
Relating polarimetric radar measurements of ice fabric to ice-flow enhancement of Rutford Ice Stream
Authors: Jordan Thomas , Brisbourne Alex , Martin Carlos , Schlegel Rebecca , Schroeder Dustin , Smith Andrew
Published: March 2020

Lateral shear margins provide resistance to ice flow within ice streams and play an important role in the overall dynamics of ice sheets. The strength and location of shear margins are known to be influenced by both subglacial factors (e.g. bed roughness, meltwater availability) and ice rheology (ice temperature, ice fabric, and damage). Assessing the relative contribution of these factors upon ice-stream flow is complex but can be aided by geophysical measurements (e.g. radar-sounding and seismic imaging) of the ice-stream subsurface. There are, however, ongoing challenges in obtaining geophysical information in an appropriate form to be incorporated into ice-flow models. This is true of ice fabric, and its direction-dependent effect upon ice viscosity is typically neglected in models of ice streams.

Here we develop a framework to relate ice fabric measurements from polarimetric radar sounding to ice-flow enhancement within ice streams. First, we extend a `polarimetric coherence’ radar method to automate the extraction of ice fabric using quad-polarized data.  Second, using a previously developed anisotropic flow-law formulation, we relate the radar fabric measurements to direction-dependent enhancement factors of glacier ice. We demonstrate the approach using a radar ground survey, collected by the British Antarctic Survey, which traverses between the centre and shear margin of Rutford Ice Stream. The data indicate that a vertical girdle fabric is present in the near-surface of the ice stream (approximately the top 300 m) which azimuthally rotates and strengthens toward the shear margin. We then assess the effect that the girdle fabric has upon shear and compression and the impact upon ice-flow models of Rutford Ice Stream.

 

 

 
Laser Ablation radiocarbon analysis of a high alpine stalagmite - a hint to an old organic carbon pool?
Authors: Welte Caroline , Fohlmeister Jens , Wacker Lukas , Wertnik Melina , Spötl Christoph , Yeman Christiane , Hattendorf Bodo , Christl Marcus , Eglinton Timothy I. , Synal Hans-Arno
Published: March 2020

A novel technique making use of laser ablation coupled online to accelerator mass spectrometry (LA-AMS) allows analyzing the radiocarbon concentration (F14C) in carbonate samples at a spatial resolution down to ~100 µm within very short analysis times [1]. This new technique can provide radiocarbon data close to the spatial resolution of stable carbon isotope measurements and, thus, can help to interpret δ13C signatures, which otherwise are difficult to understand [2]. Conventional analytical methods applied to stalagmite samples for 14C analysis, where a micro-sample is drilled or milled and carbon is liberated by the addition of phosphoric acid provide exclusively the isotope composition of the CaCO3, but not of organic matter also captured in stalagmites. LA-AMS allows accessing the 14C concentration of both materials opening up new opportunities for gaining insights into vegetation and soil dynamics.

SPA-127 is a stalagmite from Spannagel cave (W Austrian Alps) that grew between 8500 and 2500 a BP at an average rate of 25 μm/a [3]. δ13C and 14C were analyzed with high resolution along the full range of the 15 cm long specimen. During LA-AMS 14C analysis, positive anomalies in ion currents were observed in the older stalagmite section. These comparably higher CO2 conversion efficiencies are associated with organic materials compared to CaCO3 during LA. Lower F14C were observed along with these anomalies. The signal structure could be reproduced both after removing ~0.5 mm of the carbonate surface layer and on the stalagmite’s archive slab making possible contamination unlikely. So far, we deduce that the observed anomalies are caused by several flushing events in the early Holocene, in which 14C dead organic components (acids) entered the cave and were incorporated into the stalagmite matrix. Due to the high elevation of the cave and cold conditions during the glacial, the ancient organic acids most likely stem from the Eemian and were stored in the host rock.

[1] C. Welte, et al., (2016). Anal. Chem., 88, 8570– 8576.

[2] F. McDermott, (2004). Quat. Sci. Rev., 23, 901-918.

[3] Fohlmeister J. et al., (2013). Holocene, 23, 749–754.

 
Jupiter dayside as seen by JIRAM-Juno: current status and examples of spectral data analysis
Authors: Grassi Davide , Sindoni Giuseppe , Adriani Alberto , Mura Alessandro , Plainaki Christina , Bolton Scott
Published: March 2020

The JIRAM instrument on board of the Juno spacecraft includes a spectrometer that operates in the range 2-5 μm with a spectral resolution of about 15 nm.
The signal measured between 2 and 3.1 um is due to the scattering of solar photons by aerosols in the daytime Jupiter atmosphere and, as such, it has been partially exploited in [1] to study the structure of "white ovals" vortexes in the southern hemisphere.
This contribution reviews the current status and issues of analysis of JIRAM data in this solar-dominated spectral range, with several examples from different latitudes. Modeling of vertical density profile of clouds is largely based on recent results of [2].
In JIRAM spectra, the region between 2.7 and 3.1 does not show any firm evidence of ammonia ice, that would be expected to produce clear spectral features here even when massively coated with contaminants such as tholines. It is therefore difficult to properly model the data assuming the optical properties of aerosols of any given realistic composition.

[1] Sindoni, G., et al. (2017) doi: 10.1002/2017GL072940
[2] Braude, A. S., et al. (2020) doi: 10.1016/j.icarus.2019.113589
Analysis of Clay-Induced Land Subsidence in Uppsala City Using Sentinel-1 SAR Data and Precise Leveling
Authors: Nilfouroushan Faramarz , Fryksten Jonas
Published: March 2020

Land subsidence and its subsequent hazardous effects on buildings and urban infrastructure are important issues in many cities around the world. The city of Uppsala in Sweden is undergoing significant subsidence in areas that are located on clay. Underlying clay units in parts of Uppsala act as mechanically weak layers, which for instance, cause sinking of the ground surface and tilting buildings. In this study, a Persistent Scatterer InSAR (PSI) analysis was performed to map the ongoing ground deformation in Uppsala. The subsidence rate measured with PSI was validated with precise leveling data at different locations. Two ascending and descending data sets were analyzed using SARPROZ software, with Sentinel-1 data from the period March 2015 to April 2019. After the PSI analyses, comparative permanent scatterer (PS) points and metal pegs (measured with precise leveling) were identified creating validation pairs. According to the PSI analyses, Uppsala was undergoing significant subsidence in some areas, with an annual rate of about 6 mm/year in the line-of-sight direction. Interestingly, the areas of great deformation were exclusively found on postglacial clay.
Geodetic deformation rates and driving processes in metropolitan France and neighboring Western Europe
Authors: Mazzotti Stephane , Grosset Juliette , Masson Christine , Vernant Philippe
Published: March 2020

We constrain present-day deformation rates and styles in metropolitan France and neighboring Western Europe using a dataset of ca. 1200 GNSS horizontal and vertical velocities from continuous and semi-continuous stations. The characterization and correction of network-scale common-mode noise, combined with two independent network analysis technics allow the resolution of very small horizontal velocities (resp. strain rates) with a 95% confidence ca. 0.1–0.2 mm/yr (resp. ca. 1 x 10-9 yr-9) on a spatial scale of 100–200 km. The resulting velocity and strain rate fields show regional coherent patterns that can be associated with features that have been previously identified (e.g., orogen-normal extension in the Pyrenees and Western Alps), but also with new deformation patterns such as North-South shortening in northeastern France - southwestern Germany north of the Alpine Front (Vosges - Rhine Graben - Black Forest). A joint analysis of these new geodetic data with seismicity and focal mechanism catalogs allows the definition of regional seismo-tectonic models that can be compared with the numerous models of deformation processes proposed for Western Europe, from plate tectonics to erosion or Glacial Isostatic Adjustment. We show that plate and micro-plate tectonics play a minor (probably negligible) role in present-day deformation in metropolitan France and that alternative non-tectonic processes must be considered to better understand the origin of recent moderate earthquakes such as the March 2019 Ml=4.9 Montendre earthquake in the Aquitaine Basin or the Nov. 2019 Mw=4.8 Teil earthquake in the Rhone Valley.
Dynamical Evolution of Troughs and Ridges within Rossby Wave Packets: A Composite Study
Authors: Teubler Franziska , Riemer Michael
Published: March 2020

Rossby wave packets (RWPs) are a fundamental ingredient of midlatitude dynamics and organize the formation, propagation and decay of midlatitude weather systems. They may also constitute precursors to high-impact weather events. It is often expected that RWPs, as large-scale flow features obeying balanced dynamics, exhibit a large degree of predictability. Recent work, however, has shown that there is increased forecast uncertainty, in particular associated with the impact of moist processes, which may compromise medium-range predictability in the downstream region.

As a contribution to an improved understanding of these inherent uncertainties, we employ a quantitative potential vorticity (PV) – potential temperature framework to quantify different processes governing the evolution of troughs and ridges. This PV framework allows to fully separate the dynamics into four processes, namely the group propagation of Rossby waves, baroclinic growth, the impact of upper-tropospheric divergent flow, and direct diabatic PV modification.

The dynamical evolution of the amplitude of troughs and ridges within RWPs is examined from a composite perspective. The composite is based on the new ERA5 dataset and comprises 7164 RWPs. The direct diabatic contribution is estimated by the physical tendencies of the ‚Year of tropical convection‘ (YOTC) data. Additional to baroclinic downstream development, the composite analysis reveals a first-order impact of upper-level divergent flow for the amplification of ridges and the decay of troughs. We interpret divergent outflow as an indirect diabatic process associated with latent heat release below. Based on these results, we suggest extending the prevailing paradigm of downstream baroclinic development to include the systematic impact of moist processes. In the end potential implications for the predictability of RWPs are shown.
Trans-lithospheric diapirism documented in the Variscan Bohemian Massif – comparison with numerical models
Authors: Maierová Petra , Schulmann Karel , Štípská Pavla , Gerya Taras , Lexa Ondrej
Published: March 2020

In the easternmost part of the European Variscan collisional belt, the Bohemian Massif, strongly metamorphosed felsic rocks crop out at several locations in a current distance of up to several hundreds of kilometers from the supposed contact of the subducting and overriding plates. These rocks were interpreted to originate from the subducting plate (now the Saxothuringian domain), which means that the orogenic root (the Moldanubian domain) consists of rocks that originate from both upper and lower plate. More specifically, the root domain is composed of (U)HP granulites and orthogneiss, garnet peridotites, eclogites and ultra-potassic plutons that alternate with the less metamorphosed rocks of the upper plate.

Such a process of subduction and emplacement of the subducted crust into the upper plate is called relamination. In order to better constrain the dynamics of relamination, we set up a numerical thermal-mechanical model and compare the modeling results with the data from the Bohemian Massif. The model simulates oceanic and continental subduction and takes into account non-linear visco-plastic rheology, percolation of fluids, melting and melt extraction. For different parameter values, the models show different styles of behavior, namely (i) exhumation of the subducted crust along the plate interface, and (ii) flow of the subducted crust beneath the upper plate and then incorporation into its crust (i.e. relamination).

In the former case, the material records heterogeneous peak metamorphism sampling the conditions along the subduction zone, and cooling during decompression. Similar features are typical for the metamorphic complex in the Saxothuringian domain of the Bohemian Massif.

In the latter case, the typical feature is the development of diapirs that grow from the subducted continental crust, pierce the overlying lithosphere and intrude into the middle crust of the upper plate. We show that growth of such trans-lithospheric diapirs results in a similar rock assemblage as observed in the orogenic root in the Bohemian Massif. The pressure-temperature-time paths obtained in the modeled diapirs mimic those of the Moldanubian granulites. The flow of crustal material through the mantle wedge results into mixing, hydration of the mantle and melting of both materials. Emplacement of the resulting melt into crust can explain formation of the Moldanubian ultra-potassic plutons.
Slip-sense inversion in Iran: Implications for Eurasian tectonics
Authors: Guest Bernard
Published: March 2020

The left-lateral Doruneh Fault System (DFS) bounds the north margin of the Central Iranian microplate, and has played an important role in the structural evolution of the Turkish-Iranian Plateau and of Afghanistan. The western termination of the DFS is a sinistral synthetic branch fault array that shows clear kinematic evidence of having undergone recent slip sense inversion from a dextral array to a sinistral array in the latest Neogene or earliest Quaternary. Similarly, kinematic evidence from the Anarak Metamorphic complex at the southwestern most branch of the DFS terminal fault array suggests that this core complex formed at a transpressive left stepping termination and that it was inverted in the latest Neogene to a transtensional fault termination. The recognition that the DFS and possibly other faults in NE Iran were inverted from dextral to sinistral strike slip in the latest Neogene, and the likely connection between the DFS and the Herat Fault of Afghanistan suggests that the evolutions of Afghanistan and the Indo-Asian collisional system are linked to the tectonic evolution of the Turkish-Iranian Plateau. This speculative model explains the Late Neogene tectonic realignment of the Arabia-Eurasia collision zone in terms of the interaction between the Afghan blocks that were extruding west from the Indo-Asian collision and the Turkish Iranian collision zone that was evolving to the east as Arabia sutured diachronously with Eurasia. The collision of the Afghan blocks with East Iran effectively locked the respective eastern and western free boundaries for the Arabia-Eurasia, and Indo-Asian collisional belts and forced them to diverge away from one another. If confirmed, this explains the Late Miocene to Pliocene tectonic reorganization that is recognized across the Middle East and has implications for geologic process models across the region. Regional tectonic reorganization and/or inversion may (1) invert and possibly breach older Cenozoic structures while forming a younger generation of post-Miocene structures, (2) reorganize drainage and sediment supply networks, and sealing and obscuring older structural and stratigraphic bodies under younger sediments, (3) rejuvenate existing structures and trigger secondary fluid migration, and (4) increase exhumation, sediment supply, and subsidence in late Neogene basins across the region.
A criteria-set for the construction of a model cascade for fall-to-flow landslide chains
Authors: Marlovits Nina , Mergili Martin , Preh Alexander , Glade Thomas
Published: March 2020

Some of the most destructive landslide events in history have evolved through cascading effects where, for example, a rock fall in High Alpine areas transforms into a flow of rock, debris, ice, or snow. Amplification effects often result in high velocities and energies. As a result, such events can destroy private properties, infrastructure or can even lead to loss of life even in areas distant from the source.

In order to reduce the negative consequences of cascading landslide processes, numerical modelling can enrich the efficiency of risk management strategies. Unfortunately, most landslide run-out simulation models are designed either for fall or flow processes. However, it is presumed that, at least in some cases, cascading effects cannot be properly represented by only one single process model. Due to the complexity of combining and comparing models for fall and flow processes, not many attempts to do so have been documented.

In an attempt to fill this gap, the primary goal of this study is to define a criteria-set on how and when to couple the models, based on appropriate key parameters. Hence, we analyse computer models for fall and flow processes and evaluate whether their combination can provide an appropriate description of cascading landslides. A set of well-documented fall-flow events is back-calculated. Fall and flow are first simulated separately, with some overlap, each with a tool tailored for the corresponding process, based on detailed information on the case study. The input and output parameters for the overlapping areas are then analysed to investigate how and when process chains are linked. Thereby, one of the key challenges consists in the spatial transformation of the output of fall models to the input of flow models.

The findings will be used to develop a simulation framework allowing for the automated combination of fall and flow models In order to efficiently perform simulations which can be used as input for the design of hazard and risk management measures.
NEMO - The NEar real-time MOnitoring system for bright fireballs
Authors: Ott Theresa , Drolshagen Esther , Koschny Detlef , Drolshagen Gerhard , Pilger Christoph , Mialle Pierrick , Vaubaillon Jeremie , Poppe Björn
Published: March 2020

Fireballs are very bright meteors with magnitudes of at least -4. They can spark a lot of public interest. Especially, if they can be seen during daytime over populous areas. Social Media allows us to be informed about almost everything, worldwide, and in all areas of life in real-time. In the age of intensive use of these media, information is freely available seconds after the sighting of a fireball.

This is the basis of the alert system which is part of NEMO, the NEar real-time MOnitoring system, for bright fireballs. It uses Social Media, mainly Twitter, to be informed about a fireball event in near real-time. In addition, the system accesses various data sources to collect further information about the detected fireballs. The sources range from meteor networks, the data from weather satellites or lightning detectors to the infrasound data of the IMS (International Monitoring System) operated by the CTBTO (Comprehensive Nuclear-Test-Ban Treaty Organisation).

Since large meteoroids or asteroids can be detected by these infrasound sensors when they enter the Earth's atmosphere, this network provides the possibility to detect fireballs worldwide and during day and night. From the infrasound data the energy of the object that caused the fireball can be determined and hence, its size and mass can be calculated. By combining all available information about the fireball from different data sources the amount of scientific knowledge about the event can be maximized.

NEMO was under development for about 2.5 years. Since the beginning of the year the system is in operation at the European Space Agency, as part of its Space Safety Programme. In this presentation we will give an overview about NEMO, its working principle and its relation to the IMS.
Observed early-warning signals for a Greenland-ice-sheet tipping point
Authors: Rypdal Martin , Boers Niklas
Published: March 2020

Nonlinear feedbacks, such as the melt-elevation feedback, may produce a critical temperature threshold beyond which the current state of the Greenland Ice Sheet loses stability. Hence, the ice sheet may exhibit an abrupt transition under ongoing global warming, with substantial impacts on global sea level and the Atlantic Meridional Overturning Circulation. Melting rates across Greenland and solid ice discharge at the ice sheet's margins have recently accelerated. In this work, we analyze ice sheet runoff reconstructions and process-based simulations using new methods. We compare the acceleration in the runoff with the statistical properties of fluctuations around the system's equilibrium. The analysis uncovers significant early-warning signals for an ongoing destabilization and substantial further mass loss in the near future. 

 
A review of the impacts of land use change, climate zone, forest type and age on soil organic carbon and other soil quality indicators following afforestation
Authors: Guo Yang , Abdalla Mohamed , Espenberg Mikk , Hastings Astley , Hallett Paul , Smith Pete
Published: March 2020

The main aim of this global review and systematic analysis was to investigate the impacts of previous land use system, climate zone and forest type and age on soil organic carbon (SOC), total nitrogen (TN) and total phosphorus (TP), in the different soil layers (0-20, 20-60 and 60-100 cm), following afforestation. We collected 85 publications on SOC, TN and TP stock changes, covering diﬀerent countries and climate zones. The data were classified into groups depending on these investigated parameters and analyzed using R version 3.6.1. We found that afforestation significantly increased SOC and TN stocks in the 0-20 and 20-60 soil layers, with values of 45% and 44% for SOC, 30% and 22% for TN, respectively, but had no impact on TP stock. Previous land use systems had the largest influence on SOC, TN and TP stocks, with greater accumulations on barren land compared to cropland and grassland. Climate zone influenced SOC, TN and TP stocks, with significant accumulations in the moist than in the dry climate zone. Afforestation with broadleaf deciduous and broadleaf evergreen forests led to greater SOC, TN and TP accumulations in each soil layer throughout the investigated profile (0-100 cm), compared to coniferous forests. Afforestation for <20 years had significantly increased SOC and TN stocks only at the soil surface (0-20 cm) whilst afforestation for ≥ 20 years had significantly accumulated them up to 100 cm soil depth. TP stock did not change with the forest age, suggesting that it may become a limiting factor for carbon sequestration under the older-age forest. Following afforestation, the change of soil bulk density had inverse relationships with SOC or TN stocks changes but had no effect on TP stock change.
Changes in hydroclimate during last deglaciation lake-level fall in the Dead Sea sediment record
Authors: Schwab Markus J. , Müller Daniela , Neugebauer Ina , Tjallingii Rik , Ben Dor Yoav , Enzel Yehouda , Brauer Achim
Published: March 2020

The drainage basin of the Dead Sea is the largest hydrological system in the Levant and spans across the boundary between the sub-humid to semi-arid Mediterranean and the arid to hyper-arid Saharo-Arabian climate zones. As a terminal lake, precipitation changes due to climatic variations result in extensive fluctuations of lake level and sediment deposition.

A unique sediment record from the deepest part of the Dead Sea Basin was obtained as part of the ICDP Dead Sea Deep Drilling Project. Here we analyze the partially annually laminated sediments of Core 5017-1-A between 88.5-99.2 m core depth, which comprise the period between ~16.5 and ~11 ka and document a lake level drop of ca 160 m. In the sediments of Core 5017-1-A, this marks the transition from MIS2 aad (alternating aragonite and detritus) sediments to MIS1 halite deposits and ld (laminated detrital marl) sediments, coinciding with increased drying in the Dead Sea watershed.

Microfacies analyses show the occurrence of several lithological facies that accumulated during MIS2: aad, gd (massive gypsum deposit within marl), native sulfur concretions (associated with greenish colored aad), mtd (mass-transport deposits, typically graded) and homogenites consisting of clay and silt. Further, flood layers have been identified, potentially indicating rainstorms associated with specific eastern Mediterranean synoptic systems. To complement the microfacies analyses, XRF scanning provides continuous Ti/Ca and S/Ca records to reconstruct relative detrital input and gypsum occurrence, respectively. Additionally, to study potential early signs of hydroclimatic change, the deep lake sediments are correlated to the Lisan Formation of the marginal Masada outcrop using distinct gypsum marker layers, indicative of pronounced lake level drops. However, due to a significant lake level decline, the Masada outcrop sediments terminate at around 14.5 ka and the subsequent lake level lowering is solely recorded in the deep lake sediments.

This study was funded by the German Science Foundation (DFG Grant BR 2208/13-1/-2). Further, it is a contribution to the Helmholtz Association (HFG) climate initiative REKLIM Topic 8 “Abrupt climate change derived from proxy data”.
Pyroxene low-temperature plasticity and fragmentation as a record of seismic stress evolution in the lower crust
Authors: Campbell Lucy , Menegon Luca
Published: March 2020

Seismic rupture of the lower continental crust requires a high failure stress, given large lithostatic stresses and potentially strong rheologies. Several mechanisms have been proposed to generate high stresses at depth, including local amplification of stress heterogeneities driven by the geometry and rheological contrast within a shear zone network. High dynamic stresses are additionally associated with the subsequent slip event, driven by propagation of the rupture tips. In the brittle upper crust, fracturing of the damage zone is the typical response to high stress, but in the lower crust, the evolution of combined crystal plastic and brittle deformation may be used to constrain in more detail the stress history of rupture, as well as  additonal parameters of the deformation environment. It is crucial to understand these deep crustal seismic deformation mechanisms both along the fault and in the wall rock, as coseismic damage is an important (and sometimes the only) method of significantly weakening anhydrous and metastable lower crust, whether by grain size reduction or by fluid redistribution.

A detailed study of pyroxene microstructures are used here to characterise the short-term evolution of high stress deformation experienced on the initiation of lower crustal earthquake rupture. These pyroxenes are sampled from the pseudotachylyte-bearing fault planes and damage zones of lower crustal earthquakes linked to local stress amplifications within a viscous shear zone network, recorded in an exhumed granulite-facies section in Lofoten, northern Norway. In orthopyroxene, initial low-temperature plasticity is overtaken by pulverisation-style fragmentation, generating potential pathways for hydration and reaction. In clinopyroxene, low-temperature plasticity remains dominant throughout but the microstructural style changes rapidly through the pre- and co-seismic periods from twinning to undulose extinction and finally the formation of low angle boundaries. We present here an important record of lower crustal short-term stress evolution along seismogenic faults.