bluuebunny/crossref_metadata_2025 huggingface dataset:
Microinstabilities and plasma waves at Near-Sun Solar Wind collisionless Shocks: Predictions for PSP and SO
Authors: Yang Zhongwei , Matsukiyo Shuichi , Xie Huasheng , Guo Fan , Liu Mingzhe , Gao Xinliang , Lu Quanming , Wang Chi
Published: March 2021

Microinstabilities and waves excited at perpendicular interplanetary shocks in the near-Sun solar wind are investigated by full particle-in-cell simulations. By analyzing the dispersion relation of fluctuating field components directly issued from the shock simulation, we obtain key findings concerning wave excitations at the shock front: (1) at the leading edge of the foot, two types of electrostatic (ES) waves are observed. The relative drift of the reflected ions versus the electrons triggers an electron cyclotron drift instability (ECDI) that excites the first ES wave. Because the bulk velocity of gyro-reflected ions shifts to the direction of the shock front, the resulting ES wave propagates obliquely to the shock normal. Immediately, a fraction of incident electrons are accelerated by this ES wave and a ring-like velocity distribution is generated. They can couple with the hot Maxwellian core and excite the second ES wave around the upper hybrid frequency. (2) From the middle of the foot all the way to the ramp, electrons can couple with both incident and reflected ions. ES waves excited by ECDI in different directions propagate across each other. Electromagnetic (EM) waves (X mode) emitted toward upstream are observed in both regions. They are probably induced by a small fraction of relativistic electrons. The impact of shock front rippling, Mach numbers, and dimensions on the ES wave excitation also will be discussed. Results shed new insight on the mechanism for the occurrence of ES wave excitations and possible EM wave emissions at young coronal mass ejection–driven shocks in the near-Sun solar wind.
Towards the consideration of soil-root resistances in root water uptake models with macroscopic representations of hydraulic root architecture
Authors: Vanderborght Jan , Couvreur Valentin , Meunier Felicien , Schnepf Andrea , Vereecken Harry , Bouda Martin , Javaux Mathieu
Published: March 2021

Plant water uptake from soil is an important component of terrestrial water cycle with strong links to the carbon cycle and the land surface energy budget. To simulate the relation between soil water content, root distribution, and root water uptake, models should represent the hydraulics of the soil-root system and describe the flow from the soil towards root segments and within the 3D root system architecture according to hydraulic principles. We have recently demonstrated how macroscopic relations that describe the lumped water uptake by all root segments in a certain soil volume, e.g. in a thin horizontal soil layer in which soil water potentials are uniform, can be derived from the hydraulic properties of the 3D root architecture. The flow equations within the root system can be scaled up exactly and the total root water uptake from a soil volume depends on only two macroscopic characteristics of the root system: the root system conductance, Krs, and the uptake distribution from the soil when soil water potentials in the soil are uniform, SUF. When a simple root hydraulic architecture was assumed, these two characteristics were sufficient to describe root water uptake from profiles with a non-uniform water distribution. This simplification gave accurate results when root characteristics were calculated directly from the root hydraulic architecture. In a next step, we investigate how the resistance to flow in the soil surrounding the root can be considered in a macroscopic root water uptake model. We specifically investigate whether the macroscopic representation of the flow in the root architecture, which predicts an effective xylem water potential at a certain soil depth, can be coupled with a model that describes the transfer from the soil to the root using a simplified representation of the root distribution in a certain soil layer, i.e. assuming a uniform root distribution.
Analysing the intrinsic time scale of river bifurcations
Authors: Barile Gabriele , Redolfi Marco , Tubino Marco
Published: March 2021

River bifurcations play a crucial role in the morphodynamics of multi-thread channel systems such as braided or anastomosed rivers, deltas and alluvial fans, as they guide the downstream distribution of water and sediment fluxes. Several experimental and theoretical studies have highlighted the unstable character of bifurcations, which tend to produce a differential erosion/deposition in the downstream channels, even in the case of symmetric planform configuration and boundary conditions. This leads to equilibrium states where the flow distribution can be highly unbalanced, depending on the channel width-to-depth ratio. The analyses performed so far have mainly focused on equilibrium configurations, while little information exists about the time evolution of the instability process. In particular, there is no systematic analysis of how the bifurcation timescale depends on the controlling parameters, such as the channel aspect ratio, and the length of the downstream channels. Evaluation of this “intrinsic” time scale is fundamental to study the response of river bifurcations to time variations of any “external” factor that influences the bifurcation dynamics, such as the water discharge, the downstream conditions, or the presence of migrating bedforms. In this work we consider a simple bifurcation, consisting of a straight channel with mobile bed but fixed banks, which splits in two bifurcates that diverge with the same angle. We employ a 1-D shallow-water model for the upstream channel and downstream bifurcates, which are connected by means of the nodal point relation proposed by Bolla Pittaluga et al. (2013). We then numerically analyse the development of the bifurcations instability, starting from an initially-small perturbation of the bed elevation. Finally, we extensively investigate the effect of the key controlling parameters, including the model calibration coefficients, also allowing them to vary in time. The evolution of water discharge asymmetry shows a first exponential growth stage, followed by an asymptotic behaviour that leads to the equilibrium configuration. Model results reveal the key role of the width-to-depth ratio in determining the speed of the bifurcation evolution. Specifically, the evolution is very slow when the system is close to marginal stability conditions, while it becomes increasingly fast when increasing the width-to-depth ratio. Moreover, the timescale of the bifurcation increases with the length of the downstream channel, unless their length-to-depth ratio is sufficiently high.
Hemispheric asymmetry in future seasonal wave power changes
Authors: Patra Anindita , Min Seung-Ki
Published: March 2021

Wind-waves exert stress on coastal environment and wave power is a better representative of that stress rather than wave height alone. This study inspects the global changes in seasonal wave power by the end of the 21st century, compared to the 1979–2005 period as a result of projected climate change. We use multi-model wave climate simulations from WAVEWATCH-III, forced with surface winds simulated by 7 different CMIP5 Models. Our analysis of wave power reveals decreases over the Northern Hemisphere and increases over the tropics and Southern Hemisphere, with substantial seasonal and regional variations. We analyzed five different terms of differential wave power representing contribution from wave height and/or period. Although wave height changes dominantly control wave power change, contribution of wave period is pronounced over Southern hemisphere extra-tropics, remarkably over Indian Ocean sector during austral winter. Wave period increase is strikingly higher in austral winter than summer, which resembles with wave height of swells components generated in the Southern Ocean. Strong positive inter-model relationship between future change in wave power and SAM over the Southern Hemisphere is consistent with previously reported intensification of wind belt related to more frequent occurrences of positive SAM in future.  Northern Hemisphere decrease can be attributed to reduced storm activity rising from lowered meridional temperature gradient, and lacked swell activity owing to smaller fraction of sea with respect to land than the Southern Hemisphere.  
The Synoptically-Influenced Extreme Precipitation Systems over Asian-Australian Monsoon Region observed by TRMM Precipitation Radar
Authors: Chen Wei-Ting , Jian Hong-Wen , Chen Peng-Jen Chen , Wu Chien-Ming , Rasmussen Kristen L.
Published: March 2021

This study investigates the synoptic-scale flows associated with extreme rainfall systems over the Asian–Australian monsoon region (90°E–160°E and 12°S–27°N). On the basis of the statistics of the 17-year Precipitation Radar observations from Tropical Rainfall Measurement Mission, a total of 916 extreme systems, with both the horizontal size and maximum rainfall intensity exceeding the 99.9th percentiles of the tropical rainfall systems, are identified over this region. The synoptic wind pattern and rainfall distribution surrounding each system are classified into four major types: vortex, coastal, coastal with vortex, and none of above, with each accounting for 44%, 29%, 7%, and 20%, respectively. The vortex type occurs mainly over the off-equatorial areas in boreal summer. The coast-related types show significant seasonal variations in their occurrence, with high frequency in the Bay of Bengal in boreal summer and on the west side of Borneo and Sumatra in boreal winter. The none-of-the-above type occurs mostly over the open ocean, and in boreal winter, these events are mainly associated with the cold surge events. The environment analysis shows that coast-related extremes in the warm season are found within the areas where high total water vapor and low-level vertical wind shear occur frequently. Despite the different synoptic environments, these extremes show a similar internal structure, with broad stratiform and wide convective core (WCC) rain. Furthermore, the maximum rain rate is located mostly over the convective area, near the convective–stratiform boundary in the system. Our results highlight the critical role of the strength and direction of synoptic flows in the generation of extreme rainfall systems near coastal areas. With the enhancement of the low-level vertical wind shear and moisture by the synoptic flow, the coastal convection triggered diurnally has a higher chance to organize into mesoscale convective systems and hence a higher probability to produce extreme rainfall.
Genomic variation of microbial populations on a continuous 10,000-year sediment sequence from Lake Cadagno (Piora Valley, Switzerland)
Authors: Rodriguez Ramirez Paula Catalina , Berg Jasmine , Deng Longhui , Vogel Hendrik , Lever Mark A. , Magnabosco Cara
Published: March 2021

Lake Cadagno is a meromictic Alpine lake located in the Piora Valley, Switzerland. In 2019, a 10,000-year (10 m)sediment sequence was collected and found to contain three main lithological units: glacial sediment deposited under oxic conditions; a Mn-rich and organic-matter-rich sediment layer deposited during the transition from an oxic late-glacial lake to the onset of anoxia, and dark, sulfidic sediments deposited during the period of euxinia to the present. This study investigates the relationships between the physical-chemical properties and microorganisms of the sediment sequenceusing genome-resolved and targeted metagenomics.   

Results show that 16S rRNA gene abundance peaks in upper 1-32 cm of the sediment core (108 copies per gram of sediment) and decreases with depth. The abundance of a marker gene for sulfate reduction, dsrB, is positively correlated to 16S rRNA gene copy numbers, decreasing with depth from approximately 108 copies per gram of sediment in the top 30 cm to 104 gene copies per gram of sediment at 900 cm below the sediment depth.  These results suggest that sulfate-reducing microbial communities in surface sediments harvest the bioavailable oxidized sulfur inorganic species. In contrast, the presence of sulfate-reducing genes in sediments with sulfate concentrations below detection may indicate the engagement of microbial populations in sulfur cycling using alternative metabolic strategies (e.g. secondary fermentation).

 

Moreover, a clear differentiation between surface and deep sediment communities is observed. Sequencing of dsrB amplicons show a decrease in dsrB sequence richness with depth and sediment age. A clear transition from a surface section dominated (>80% relative abundance) by Deltaproteobacteria-related dsrB sequences from well-studied groups, to a deeper section below 40 cm dominated by a group of unclassified dsrB sequences most likely related to Firmicutes or Chloroflexi is also observed. The identity of these unclassified dsrB sequences will be determined by genome-resolved metagenomic sequencing (currently in progress). Furthermore, these analyses will give information on the presence of complete sulfate-reduction pathways and/or genes related to sulfur cycling in these microbial groups. By reconstructing the genomes of sulfate reducers and other microbial populations throughout the core, we will investigate whether there are genomic changes associated with the main geochemical trends. This work will enable us to assess the influence of a changing lake with the evolution of sediment-dwelling prokaryotic populations over thousands of years.

 

 

 
Where do the buds get their water from during budburst? New perspectives from temperate forest species using water stable isotopes
Authors: Martín Gómez Paula , Ogée Jérôme , Burlett Régis , Barbeta Adrià , Devert Nicolas , Dubois Sabrina , Frejaville Bastien , Wingate Lisa
Published: March 2021

During winter dormancy in deciduous species, water stops flowing in the xylem and buds become isolated from the stem xylem conduits by a physical barrier made of callose deposits. During bud break, the plant builds new vascular connections between the growing buds and the xylem to support sap flow and transpiration in the developing leaves. However, little is known about the exact timing when these new vascular connections are made, or about the origin of the water supporting bud swelling prior to bud break. This information is particularly limited in forest tree species. We aimed to clarify the origin of the water entering the buds at different developmental stages in temperate forest tree species using water stable isotope tracing techniques to track water movement between soil, stem and buds. More specifically, we developed a method to collect sap water separately from water in other stem tissues (Barbeta et al. 2020). At different leaf phenological stages during the 2018 growing season, we collected soil, stem, bud and leaf samples from 5 adult trees and 3 species (Fagus sylvatica, Quercus robur, Pinus pinaster) growing in a riparian forest in Southwest France. We estimated the relative water content in each sample by extracting bulk water by cryogenic vacuum distillation, and also extracted sap water from stem samples using our new method. All water samples were then analysed for their stable isotope composition (δ18O, δ2H). These results, complemented by some additional labelling experiments, provide key information about the timing of hydraulic reconnection between the buds and the xylem and about the source of water supporting bud swelling and bud break, demonstrating the usefulness of water stable isotope measurements to understand water transport pathways during bud development and canopy leaf out.

 

Reference:

Barbeta, A., Burlett, R., Martín-Gómez, P., Fréjaville, B., Devert, N., Wingate, L., Domec, J.-C., et al. (2020). Evidence for distinct isotopic composition of sap and tissue water in tree stems: Consequences for plant water source identification. BioRxiv, 2020.06.18.160002.
Lessons learned from working with windstorm-related impact data
Authors: Láng Ilona , Mäkelä Antti
Published: March 2021

Strong wind related to extratropical cyclones causes severe socioeconomic impacts every year in Europe. Especially in highly forested countries, such as Finland, the civil protection, insurance companies and energy sector are strongly affected by windstorms. Falling trees cause damage to the properties and transmission lines, interrupt the traffic and in the worst case can even cause fatalities. With better preparedness measures, such as highly developed early warning systems (EWSs), windstorm impacts can be reduced significantly.

For better preparedness and mitigation of storm impacts, it is essential to understand the windstorm and environmental features which contribute to the damages. Wind speed and gusts alone do not always explain why the windstorm is or is not causing disturbances in the society. To increase the understanding of the processes that lead to windstorm impacts, it is crucial to use additional data alongside the traditional meteorological data sources. There is high potential in combining wind impact data (e.g. electricity interruption records or emergency calls) with meteorological parameters to develop tools, for instance as a part of EWSs for crisis decision making. Such tools can help the civil protection or energy companies to prepare for the windstorm with sufficient human resources and other precautionary measures, which ultimately reduces impacts and increases the resilience of the society. Additionally, impact database can benefit the forecasters in their daily work with weather warnings or researchers with easier access to impact data. 

Impact database development has been done for instance on a national scale in SILVA project (2020-2021, Finnish National Emergency Supply Agency and Finnish Meteorological Institute) and on a pan-European scale in LODE project (2018-2021, the European Commission – DG ECHO). In this work we aim to share the lessons we learned in the impact data collection and processing, and the possibilities to connect the socioeconomic impacts with windstorms. We highlight especially how the quality and comprehensiveness of the impact data are the key factors in the development of wind impact tools. For example, to be able to identify significant trends in windstorm impacts, a sufficient temporal coverage and data homogeneity of the datasets are essential. The centralisation of the data collection is an additional important aspect: a centralised impact database maintained by one research organisation can be a solution to store and combine different types of impact data and connect it with the relevant meteorological or environmental data (e.g. forest or land use data).
Using different solutions for radiative transfer of solar-induced fluorescence in a land surface model
Authors: Thum Tea , Pacheco-Labrador Javier , Magney Troy , Migliavacca Mirco , Quaife Tristan , Zaehle Sönke
Published: March 2021

Chlorophyll fluorescence (ChlF) takes place in green leaves of the plants during photosynthesis. It has therefore been proposed that ChlF can be used to track the photosynthetic activity of plants and the current possibility to observe sun-induced chlorophyll fluorescence (SIF) via remote sensing provides an unprecedented tool to monitor terrestrial photosynthesis at global scale. However, the relationship between photosynthesis and ChlF is not linear at all scales and is partly controlled by the non-photochemical quenching - which dissipates excess energy as heat. The relationship between the photochemical and fluorescence yields changes when the photochemical quenching is dominating at low irradiance conditions or at high stress conditions. Interpretation of observed SIF is complicated by its dependence on incoming absorbed radiation, observation geometry and radiative transfer of SIF photons within the canopy. To fully exploit remotely sensed SIF to estimate photosynthesis at ecosystem and global scales, it is important to account for these aspects through modelling that include ecosystem processes.

In this work we have implemented a ChlF model into a state-of-the-art land surface model QUantifying Interactions between terrestrial Nutrient CYcles and the climate system (QUINCY) simulating the terrestrial energy, water and biogeochemical cycles of carbon, nitrogen and phosphorus. The simulation of radiative transfer is highly influential for the simulated SIF signal, but the complex solutions of radiative transfer are computationally too heavy, making them impractical approaches at global scale. Therefore, we have investigated different radiative transfer techniques for the SIF signal of varying complexity at site scale in Niwot Ridge, U.S. <!-- we have now one clean growing season of data in a beech forests if you want to compare a deciduous and a evergreen, and of course a coule of years of grasslands (even if you don't want to put it in the abstract) -->The most complex solution is based on the mSCOPE and Fluspects model, that explicitly calculates signal transfer. The intermediate solution is based on a two-stream flux approach and the most simple is using a simple fraction for the escape ratio of SIF. Our aim is to assess which solution is most suitable for simulating the SIF signal at different scales and also test different formulations for modelling of non-photochemical quenching.
Near and far-field seismo-acoustic analysis of mb 4.9 mining induced earthquake nearby Kiruna, Sweden
Authors: Turquet Antoine , Brissaud Quentin , Näsholm Sven Peter , Kero Johan , Kværna Tormod , Listowski Constantino , Le Pichon Alexis
Published: March 2021

An earthquake happened in 18 May 2020 early morning in the Kiruna underground iron ore mine, Northern Sweden having a magnitude Mw 4.9. Following the earthquake, the mine was immediately evacuated because of the risk of aftershocks. This event is the largest mining-induced earthquake that has ever taken place in Scandinavia and it produced signals recorded by three infrasound arrays at distances of 7 km (KRIS, Sweden), 155 km (IS37, Norway) and 286 km (ARCI, Norway). We explore seismo-acoustic features of this event recorded in near and far-field. This procedure allows us to track how the signal propagated in the solid earth until the seismometers located at various distances or transmitted to the atmosphere and propagated further to the infrasound stations. Our study also provides a detailed comparison between observed and predicted wave front characteristics at the arrays. We conduct a comparison of amplitude corrected for propagation effect versus magnitude and ground shaking amplitude. These results show that this mine-quake having “unconventional” source mechanism generated infrasound recorded up to ~300 km and provided ground shaking information as well as local amplification caused by topographic and geological features.
Method to obtain optimum number of clusters in geo-spatial data using stability analysis of cluster centres
Authors: O Leary Dave , Daly Eve , Brown Colin
Published: March 2021

Recently the availability of large geo-spatial datasets has increased. These range from soil, quaternary, and geology maps to airborne geophysical and satellite remote sensing data. Such datasets may provide a means to spatially map hydrologically relevant properties (porosity, permeability, texture, depth etc), traditionally mapped via in-situ measurements. However, such datasets, and the relationship between them, is often complex.

Clustering of multidimensional data offers a means to simplify our understanding of the relationships in the data by dividing it into groups containing similar relationships. Clustering can be used as a form of initial exploratory analysis when little is known about how the data relates to the underlying processes in its creation. Such analysis can be useful for geo-spatial datasets whereby the resulting clusters can be re-projected back to the original spatial coordinates and the spatial distribution of the clusters can be visualised.

There are various clustering algorithms available and the choice of algorithm is often as important as choosing the clustering parameters within it. This work shows a comparison between a more traditional K-Means clustering and a more modern machine learning technique known as Self-Organising Maps (SOMs). The choice of number of clusters for such an analysis is also ambiguous, requiring a priori knowledge of the result. This undermines the general idea behind unsupervised clustering, whereby the result should be driven by the data.

Here, a method is proposed to allow the choice of clusters to be dependent on a metric derived from within the cluster analysis itself. The method presented uses the variation in (dataspace) distance between each data point and its cluster centre over 100 runs, for increasing number of clusters. The number of clusters at which this variation remains low is then determined to be the natural optimum number of clusters for a particular dataset.

This method is tested on a dataset where the cluster number is already known and a real-world example. Dataset 1 is the “Rice Grain Model” with four known clusters, which the method can accurately reconstruct. The real-world dataset is a combination of airborne radiometric geophysical data and a digital elevation model over peatland in the Republic of Ireland. The method outputs three as the optimum number of clusters and the result divides the peatland into three zones (confirmed with a ground geophysics survey) which are to be used in the creation of hydrological units within Soil and Water Assessment Tool (SWAT) modelling.
Ophiolitic peridotites in Xigaze (Tibet): Constraints on modes of melt transport in the mantle
Authors: Zhao Lingquan , Chakraborty Sumit , Schertl Hans-Peter
Published: March 2021

The Xigaze ophiolite (Tibet), which occurs in the central segment of the Yarlung Zangbo Suture Zone, exposes a complete portion of a mantle sequence that consists essentially of fresh as well as serpentinized peridotites. We studied a sequence beneath the crustal section that exposes fresh, Cpx-bearing harzburgites and dunites that are underlain by serpentinized Cpx-bearing harzburgites and dunites. The rocks at the bottom are crosscut by dykes that have undergone different degrees of rodingitization. The modal compositions of peridotite from both fresh and serpentinized sections plot in abyssal upper mantle fields, with clinopyroxene modes less than 5 vol. %. Although harzburgites and dunites indicate that melt has been lost relative to primitive mantle compositions, the trace element patterns carry signatures of enrichment in incompatible elements, such as (i) “bowl-shaped” patterns of trace elements in silicate-Earth normalized spider diagrams, (ii) positive anomalies in highly incompatible trace elements such as Rb, Th, U, Ta, and (iii) enrichment of LREE in the clinopyroxenes from dunites and harzburgites. These features are indicative of complex melt transfer processes and cannot be produced by simple melt extraction. Petrographic studies reveal that harzburgite and dunite contain interstitial polyphase aggregates of olivine + Cpx + spinel + Opx and olivine + Cpx + Spinel, respectively. Experimental studies (e.g. Morgan and Liang, 2003) suggest that these aggregates represent frozen melt-rich components, indicating that fertile melt was percolating through the depleted harzburgite – dunite matrix. Presence of such “melt pods” would explain the trace element enrichment patterns of the bulk rock, as well as features such as reverse zoning (core: Cr, Fe2+ rich, rim: Al, Mg rich) of spinels in polyphase aggregates in fresh dunites. These results show that melt extraction from the mantle is not a single stage process, and that evidence of multiple melt pulses that propagated through a rock are preserved in the petrographic features as well as in the form of chemical signatures that indicate refertilization of initially depleted rocks.
On the effect of different moss species on soil erosion, percolation and carbon relocation
Authors: Gall Corinna , Grabherr Lena , Nebel Martin , Scholten Thomas , Thielen Sonja M. , Seitz Steffen
Published: March 2021

For decades, soil erosion has been a major environmental problem as it degrades the most productive soil layers, which threatens, among other things, food production worldwide. Although these effects have been known for a long time, there are still a variety of challenges to mitigating soil erosion in different ecosystems. As climate change progresses, the risk of soil loss increases, making the preparation of effective solutions very urgent. A current research focus is on the restoration of a protective soil cover following disturbances in the vegetation layer, e.g., through the reestablishment of biological soil crust communities. These are often dominated by bryophytes in humid climates. So far, several studies examined the general protective influence of bryophytes against soil erosion, however only few of them addressed how individual species affect specific erosion processes in detail.

To fill this research gap we investigated the impact of six moss species on soil erosion, percolation and carbon relocation by means of rainfall simulations. Therefore, we used topsoil substrate from four sites in the Schönbuch Nature Park in South Germany which covers different kinds of bedrock and varying soil texture and pH. Subsequently, they were sieved by 6.3 mm and filled into metal infiltration boxes (40 x 30 cm) up to a height of 6.5 cm. The moss species differ in origin (either collected in the field or cultivated in the lab) as well as growth form (pleurocarpous or acrocarpous). Rainfall simulations were performed for bare soil substrates, as well as for moss-covered soil substrates six months later and both in dry and wet conditions. Additionally, we conducted rainfall simulations with leaf and coniferous litter on bare soil substrates. During the simulations we monitored soil moisture in two position - 3 cm depth plus soil surface - with biocrust wetness probes (BWP) and quantified surface runoff, percolation and sediment discharge. Afterwards we determined carbon contents of the sediment and dissolved organic carbon in the liquid phase of runoff and percolated water.

While surface runoff was increased by 5% due to the litter cover compared to the bare soil substrate, sediment discharge decreased to 97%. Runoff rates could also be mitigated by 90 % as a result of the moss cover. Furthermore, due to the dense moss cover sediment rates were almost reduced to zero. Preliminary results show that there are differences between the moss species in terms of sediment discharge, but not in context with runoff. The analyses of carbon contents in surface runoff and the percolated water are still in progress, as is the evaluation of the BWP measurements. These outcomes will be presented at vEGU21.
Calcium-sulfate wedges in the Atacama Desert as indicators for subsurface dynamics
Authors: Zinelabedin Aline , Ritter Benedikt , Albert Richard , Brill Dominik , Gerdes Axel , Reimann Tony , Riedesel Svenja , Dunai Tibor J.
Published: March 2021

Polygonal patterned grounds are common surface expressions of subsurface dynamics in periglacial and Martian environments. In the Periglacial these structures are typically associated with vertically laminated wedges in the subsurface being the product of cryogenic processes. These landscape features similarly occur in arid to hyperarid environments, such as in the Atacama Desert. Due to the salt-dominated soil of the Atacama Desert, haloturbation and salt heave mechanisms control the formation of wedges and polygons under arid conditions. We present x-ray diffraction and x-ray fluorescence analyses of wedges from the central Atacama Desert that contain various calcium-sulfate phases as potential drivers for the wedge-growth activity. The formation of these wedges is connected to varying water activity. Hydration- and dehydration-induced phase transitions of calcium-sulfate phases result in significant volumetric changes in the soils. In combination with crystallisation pressure of (re-)precipitated salts from infiltrated solutions, these processes significantly contribute to the subsurface stress field. The upward stress release is assumed to express in a microtopographic signature of the surface, such as the polygonal patterned ground. In order to investigate the polygon-wedge system under arid conditions, we will present a combination of sedimentological, mineralogical, and geochemical analyses of subsurface wedges from the central Atacama Desert. We also present data constraining the formation age of calcium sulfate-dominated wedges that formed within the El Diablo Formation of Miocene age.
Tropical rainfall linked to stronger future ENSO-NAO teleconnection in CMIP5 models
Authors: Fereday David , Chadwick Rob , Knight Jeff , Scaife Adam
Published: March 2021

The El Niño-Southern Oscillation (ENSO) has previously been shown to influence the winter North Atlantic Oscillation (NAO).  In this presentation we investigate the ENSO-NAO teleconnection in historical and RCP8.5 scenario CMIP5 simulations, and show a future strengthening of the teleconnection under RCP8.5.  The teleconnection strength is associated with increased tropical east Pacific rainfall variability.  Stratospheric and tropospheric teleconnection pathways are examined, with both pathways having stronger links in future.  The stratospheric pathway involves the Aleutian Low and the stratospheric polar vortex, with a downward influence on the NAO.  This pathway is clearest in the high-top models that better resolve the stratosphere.  The tropospheric pathway is driven by the Pacific subtropical jet strengthening and extending further into the Atlantic in future, generating increased baroclinicity in the Caribbean and influencing the Atlantic storm track.  Our results suggest increasing influence of tropical rainfall on extratropical circulation in future.
Future climate change scenarios shaped by inter-model differences in Atlantic Meridional Overturning Circulation response 
Authors: Bellomo Katinka , Angeloni Michela , Corti Susanna , von Hardenberg Jost
Published: March 2021

In climate model simulations of future climate change, the Atlantic Meridional Overturning Circulation (AMOC) is projected to decline. However, the impacts of this decline, relative to other changes, remain to be identified. Here we address this problem by analyzing 30 idealized abrupt-4xCO2 climate model simulations. We find that in models with larger AMOC decline, there is a minimum warming in the North Atlantic, a southward displacement of the Inter-tropical Convergence Zone (ITCZ) and a poleward shift of the mid-latitude jet. The changes in the models with smaller AMOC decline are drastically different: there is a relatively larger warming in the North Atlantic, the precipitation response exhibits a wet-get-wetter, dry-get-drier pattern, and there are smaller displacements of the mid-latitude jet. Our study indicates that the AMOC is a major source of inter-model uncertainty, and continued observational efforts are needed to constrain the AMOC response in future climate change.
The combination and contribution of different gravity measurements in regional quasi-geoid determination based on spherical radial basis functions
Authors: Liu Qing , Schmidt Michael , Sánchez Laura
Published: March 2021

In this study, we investigate the optimal combination of local gravity observations and their contributions to the regional quasi-geoid model. The study area is located in Colorado, USA, with two types of regional data sets, namely terrestrial gravity data and airborne gravity data, available within the “1 cm geoid experiment”. The approach based on series expansions in terms of spherical radial basis functions (SRBF) is applied, which has been developed at DGFI-TUM in the last two decades. We use two different types of basis functions covering the same spectral domain separately for the terrestrial and the airborne measurements. The Shannon function is applied to the terrestrial data, and the Cubic Polynomial (CuP) function which has smoothing features is applied to the airborne data for filtering their high-frequency noise.

To assess the contributions of the regional terrestrial and airborne gravity data to the final quasi-geoid model, four solutions are compared, namely the combined solution, the terrestrial only, the airborne only, and finally the model only solution, i.e., only the global gravity model and the topographic model are used without any gravity data from regional measurements. By adding the terrestrial data to the GGM and the topographic model, the RMS error of the quasi-geoid model w.r.t the validation data (the mean solution of independent computations delivered by fourteen institutions from all over the world) drops from 4 to 1.8 cm, and it is further reduced to 1 cm by including the airborne data.
Annual displacements, strain partitioning and pore pressure variation in the Triesenberg Earthflow
Authors: Maissen Jasmin , Löw Simon , Aaron Jordan
Published: March 2021

Large landslide complexes in flysch are among the largest landslides on earth. These landslides often feature a rotational landslide at the head, the weathering and downslope transport of which produces one or more earthflows that terminate in a bulging toe at a valley bottom. These landslide complexes typically undergo ductile movements, on the order of mm/year to cm/year, and thus loss of life risk is typically low. However, the earthflow portions of these complexes can surge, which can result in significant infrastructure damage. Thus, understanding annual landslide displacements, the partitioning of strain within the landslide body, as well as subsurface groundwater recharge are crucial factors for understanding and managing these landslide complexes.

In the present work we present and analyze a uniquely detailed dataset collected for the Triesenberg Landslide, a landslide complex in Flysch located in Liechtenstein. This dataset contains accurate measurements of surface displacements that occurred between 1978 and 2012, InSAR displacement time series from 2011 to 2020, periodic measurements (once or twice a year) of over 30 inclinometers since 1995, continuous and periodic pore pressure measurements at a number of locations since 2001 as well as climatic data from nearby climate stations. We combine the surface and subsurface displacement measurements to understand how strain is partitioned in the landslide, as well as seasonal and annual landslide displacement rates. We then combine pore-pressure measurements and climatic data to investigate groundwater recharge mechanisms, as well as the water balance of our study area. The analysis of the InSAR data, as well as its comparison to previous displacement measurements, reveals annual displacement rates up to 4.5 cm/year. Additionally, the inclinometer data shows that the depth to the rupture surface varies throughout the landslide body, and is measured as deep as 70 m in some locations. Surprisingly, very few internal shear planes were noted within the earthflow portion of the landslide. We find that recharge into the landslide body is complex, and that the water mass balance is potentially influenced by the adjacent Valuna valley. By combining these analyses, we are able to gain preliminary insights into the behavior of the Triesenberg landslide, which has important implications for understanding this landslide as well as many other landslide complexes in flysch.
Deformation patterns in Canary Islands volcanic area from GNSS data analysis
Authors: Riccardi Umberto , Arnoso Josè , Benavent Maite , Tammaro Umberto , Montesinos Fuensanta G. , Blanco-Montenegro Isabel , Vélez Emilio
Published: March 2021

We present a study of the deformation pattern along the Canary archipelago through the analysis of continuous GNSS data. We use data spanning 2011–2017 period to retrieve precise horizontal displacements and a broad calculation of the strain. Geodetic data are interpreted in light of the regional tectonics, which is proven to play a key role in the volcanic eruptions that take place in the archipelago. The common-mode component filtering technique is applied to improve the signal-to-noise ratio of the time series of the GNSS daily solutions before retrieving the geodetic velocities. Through a triangular segmentation approach, we retrieve the 2D infinitesimal strain from the velocities along the Canaries and map deformation patterns in various sectors of the volcanic archipelago. We found areas of maximum deformation west of Tenerife, Gran Canaria and Fuerteventura Islands. A sharp change in shear strain between Tenerife and Gran Canaria is recognized, delineating a sector of intense seismicity, which is mostly associated with a well-known major submarine fault that separates the two insular edifices. On this submarine tectonic structure, we have performed a tentative simulation of the horizontal deformation and strain caused by one of the strongest (mbLg 5.2) earthquakes of the region. Our strain analysis supports the possibility that the main tectonic lineaments are being influenced by the regional stress field. Furthermore, the seismic areas between islands seem mainly influenced by the regional tectonic stress, rather than by the local volcanic activity. This is in accordance with the extensional and compressional tectonic regimes, already identified by other authors, which might favour episodes of volcanism in this volcanic archipelago.
The Global Precipitation Climatology Project Version 3 Products
Authors: Huffman George J. , Behrangi Ali , Adler Robert F. , Bolvin David T. , Nelkin Eric J. , Song Yang , Wang Jian-Jian
Published: March 2021

The Global Precipitation Climatology Project (GPCP) is currently providing a next-generation Version 3.1 Monthly product, which covers the period 1983-2019.  This modernized product includes higher spatial resolution (0.5°x0.5°); a wider coverage (60°N-S) by geosynchronous IR estimates, now based on the Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks-Climate Data Record (PERSIANN-CDR) algorithm, with monthly recalibration using Goddard Profiling (GPROF) algorithm retrievals from selected passive microwave sensors; and improved calibrations of Television-Infrared Operational Satellite (TIROS) Operational Vertical Sounder (TOVS) and Advanced Infrared Sounder (AIRS) precipitation, used outside 60ºN-S.  The merged satellite estimate is adjusted to the Tropical Combined Climatology (TCC) at lower latitudes, and the Merged CloudSat, TRMM, and GPM (MCTG) climatology at higher latitudes.  Finally, V3.1 provides a merger of the satellite-only estimates with the Global Precipitation Climatology Centre (GPCC) monthly 1°x1° gauge analyses. 

As well, the GPCP team is advancing a companion global Version 3 Daily product, in which the Integrated Multi-satellitE Retrievals for Global Precipitation Measurement (GPM) mission (IMERG) Final Run V06 estimates are used where available (initially restricted to 60°N-S), and rescaled TOVS/AIRS data in high-latitude areas, all calibrated to the GPCP V3.1 Monthly estimate.  Since IMERG currently extends back to June 2000, daily PERSIANN-CDR data will be used for the period January 1983–May 2000 to complete the record.

This presentation will provide early results for, and the latest status of, the Monthly and Daily GPCP products as a function of time and region.  Key points include examining homogeneity over time and across time and space boundaries between input datasets.  One key activity is to refine the V3 products while we continue to produce the Version 2 GPCP products for on-going use.
The national seismic network for the Maltese islands: Update 2021
Authors: Galea Pauline , Agius Matthew , Bozionelos George , D'Amico Sebastiano , Farrugia Daniela
Published: March 2021

The Maltese islands are a small country 15 km wide by 30 km long located about 100 km south of Sicily, Italy. Since 2015 Malta has set up a national seismic network. The primary aim of this network is to monitor in real-time and to locate more accurately the seismicity close to the islands and the seismicity in the Sicily Channel, offshore between Sicily, Tunisia and Libya. This Channel presents a range of interesting and complex tectonic processes that have developed in response to various regional stress fields mainly as a result of the collision between the African plate with Europe. The Maltese islands are known to have been affected by a number of earthquakes originating in the Channel, with some of these events estimated to be very close to the islands.

The seismotectonic characteristics of the Sicily channel, particularly south of the Maltese islands, is not well understood. This situation is being partially addressed through an increase in the number of seismic stations on the Maltese archipelago. The Malta Seismic Network (FDSN code ML), managed by the Seismic Monitoring and Research Group, within the Department of Geosciences, University of Malta, currently comprises 8 broadband, 3-component stations over an area slightly exceeding 300 km2. We present a technical description of the MSN including quality control tests such as spectral analysis (Power Spectral Density and HVSR), station orientations and timings as well as examples of local and regional earthquakes recorded on the network. We describe the upgrades to real-time data transmission and archiving, and automated epicentre location for continuous seismic monitoring using the local network amalgamated with a virtual seismic network to monitor the seismicity in the extended Mediterranean region. Such a dense national network, besides improving epicentral location in the Sicily Channel, is providing valuable information on microearthquake activity known to occur in close proximity to the islands, which has been very difficult to study in the past. It also provides an important tool for analysing site response and site amplification related to underlying geology, which constitutes a major component of seismic hazard analysis on the islands. Furthermore, the increase in seismic stations to the seismic monitoring system provides more robust earthquake estimates for the tsunami monitoring/simulation system.

Funding for stations was provided by Interreg Italia-Malta projects (SIMIT and SIMIT-THARSY, Codes B1-2.19/11 and C1-3.2-57) and by Transport Malta.