bluuebunny/crossref_metadata_2025 huggingface dataset:
Not back to their old selves – rewetted peatlands require functional understanding for sound management
Authors: Kreyling Jürgen , Tanneberger Franziska , Jansen Florian , van der Linden Sebastian , Joosten Hans , Jurasinski Gerald , Many Others many
Published: March 2021

Peatlands, in particular temperate, groundwater-fed fens, have widely been drained for agriculture. However, draining peatlands turns them into globally relevant carbon sources, diminishes water holding capacity and nutrient removal at landscape scales, and threatens their native biodiversity. Consequently, formerly drained peatlands are now being re-wetted in large numbers for mitigating climate change, combating eutrophication, managing water and preserving biodiversity. A comparison between >300 rewetted peatlands to > 260 close to natural peatlands across temperate Europe, however, indicates that rewetting drained peatlands induces a helophytization (a dominance of tall, graminoid wetland plants) with no trend back to their former biodiversity (vegetation) and function (geochemistry, hydrology) for at least several decades. An understanding of these locally novel ecosystems is required for sound and sustainable management of their ecosystem services.
Constraining anthropogenic carbon and excess heat uptake in climate projections
Authors: Bourgeois Timothée , Goris Nadine , Schwinger Jörg , Tjiputra Jerry
Published: March 2021

The North Atlantic and Southern Oceans are major sinks of anthropogenic carbon and excess heat. The Earth system model projections of these sinks provided by the CMIP5 and CMIP6 scenario experiments remain highly uncertain, hindering an effective development of climate mitigation policies for meeting the ambitious climate targets laid down in the Paris agreement. A recent study identified an emergent coupling between anthropogenic carbon and excess heat uptake, highlighting the dominant passive-tracer behavior of these two quantities under high-emission scenarios. This coupling potentially allows for the use of a single observational constraint to reduce these projection uncertainties. As a first step, we investigate the causes of these uncertainties in the Southern Ocean (30°S-55°S) by looking regionally at different contemporary physical and biogeochemical quantities. We find that the variations in model´s contemporary water-column stability over the first 2000 m is highly correlated to both its future anthropogenic carbon uptake and excess heat uptake efficiency. Using an observation-based estimate of contemporary water-column stability, this allows us to reduce the uncertainty of future estimates of (1) the cumulative anthropogenic carbon uptake by up to 50% and (2) the excess heat uptake efficiency by 23%. Our results show that improving representation of water-column stratification in Earth system models should be prioritized to constrain future carbon budget and climate change projections.
Sulfidization of ferrihydrite in the presence of organic ligands
Authors: ThomasArrigo Laurel K. , Bouchet Sylvain , Kaegi Ralf , Kretzschmar Ruben
Published: March 2021

In soils and sediments, short-range order (SRO) iron minerals constitute one of the most abundant and reactive mineral components. With high surface areas and points of zero charge near pH 7-8, SRO minerals like ferrihydrite (Fe10O14(OH)2+mH2O) are often linked to high adsorption of nutrients (C, N, P, S) and trace elements (e.g. As, Zn). However, under oxygen-limiting conditions, microbially derived sulfide (S(−II)) may cause the rapid reductive dissolution of ferrihydrite and the release of associated nutrients and trace elements, thus influencing the biogeochemical cycling of trace elements and nutrients, particularly in redox dynamic environments.

Sulfidization of ferrihydrite occurs rapidly, whereby electron transfer between surface complexed sulfide and the ferrihydrite surface results in (partially) oxidized sulfur species and Fe(II). Depending on the S(-II):Fe molar ratios, secondary reactions then lead to mackinawite (FeS) or pyrite (FeS2) precipitation. In nature, however, ferrihydrite is often found associated with natural organic matter (NOM). Because coprecipitation of ferrihydrite with NOM decreases particle size, alters the surface charge, and may block surface sorption sites, we speculated that kinetics and pathways of sulfidization of organic-associated ferrihydrite may differ from those of the pure mineral. Therefore, in this study, we followed iron mineral transformations and sulfur speciation during sulfidization of a pure ferrihydrite over one year and compared this to ferrihydrite coprecipitated with model organic ligands (polygalacturonic acid, galacturonic acid, and citric acid). Using a combination of solid- and aqueous phase Fe and S speciation techniques, we show that the impact of OM on ferrihydrite sulfidization kinetics and pathways varies with the chemical structure of the organic ligand, and that secondary reactions continue well past the initial rapid consumption of S(-II).
Comparison of Key Characteristics of Remarkable SSW Events in the Southern and Northern Hemisphere
Authors: Kozubek Michal , Krizan Peter
Published: March 2021

An exceptionally strong sudden stratospheric warming (SSW) in the Southern Hemisphere (SH) during September 2019 was observed. Because SSW in the SH is very rare, comparison with the only recorded major SH SSW is done. According to World Meteorological Organization (WMO) definition, the SSW in 2019 has to be classified as minor. The cause of SSW in 2002 was very strong activity of stationary planetary wave with zonal wave-number (ZW) 2, which reached its maximum when the polar vortex split into two circulations with polar temperature enhancement by 30 K/week and it penetrated deeply to the lower stratosphere and upper troposphere. On the other hand, the minor SSW in 2019 involved an exceptionally strong wave-1 planetary wave and a large polar temperature enhancement by 50.8 K/week, but it affected mainly the middle and upper stratosphere. The strongest SSW in the Northern Hemisphere was observed in 2009. This study provides comparison of two strongest SSW in the SH and the strongest SSW in the NH to show difference between two hemispheres and possible impact to the lower or higher layers.
Simulation of the mid-Pliocene Warm Period using HadGEM3-GC31-LL: Pliocene climate relative to the pre-industrial era, previous model versions, other climate models and proxy data
Authors: Williams Charles , Lunt Daniel , Sellar Alistair , Roberts William , Smith Robin , Hopcroft Peter , Stone Emma
Published: March 2021

To better understand the processes contributing to future climate change, palaeoclimate model simulations are an important tool because they allow testing of the models’ ability to simulate very different climates than that of today.  As part of CMIP6/PMIP4, the latest version of the UK’s physical climate model, HadGEM3-GC31-LL (hereafter, for brevity, HadGEM3), was recently used to simulate the mid-Holocene (~6 ka) and Last Interglacial (~127 ka) simulations and the results were compared to the preindustrial era, previous versions of the same model and proxy data (see Williams et al. 2020, Climate of the Past).  Here, we use the same model to go further back in time, presenting the results from the mid-Pliocene Warm Period (~3.3 to 3 ma, hereafter the “Pliocene” for brevity).  This period is of particular interest when it comes to projections of future climate change under various scenarios of CO2 emissions, because it is the most recent time in Earth’s history when CO2 levels were roughly equivalent to today.  In response, albeit due to slower mechanisms than today’s anthropogenic fossil fuel driven-change, during the Pliocene global mean temperatures were 2-3°C higher than today, more so at the poles.

 

Here, we present results from the HadGEM3 Pliocene simulation.  The model is responding to the Pliocene boundary conditions in a manner consistent with current understanding and existing literature.  When compared to the preindustrial era, global mean temperatures are currently ~5°C higher, with the majority of warming coming from high latitudes due to polar amplification from a lack of sea ice.  Relative to other models within the Pliocene Modelling Intercomparison Project (PlioMIP), this is the 2nd warmest model, with the majority of others only showing up to a 4.5°C increase and many a lot less.  This is consistent with the relatively high sensitivity of HadGEM3, relative to other CMIP6-class models.  When compared to a previous generation of the same UK model, HadCM3, similar patterns of both surface temperature and precipitation changes are shown (relative to preindustrial).  Moreover, when the simulations are compared to proxy data, the results suggest that the HadGEM3 Pliocene simulation is closer to the reconstructions than its predecessor.
Indoor Radon in public schools, a preliminary study in Central Portugal
Authors: Candeias Carla , Pereira Alcides , Rocha Fernando
Published: March 2021

Good air quality is considered to be a basic condition for human health and well-being. Exposure to air contamination is undoubtedly associated with diverse adverse health effects, particularly in vulnerable population subgroups such as children. Regions with natural Radon gas (Rn) emissions are of major concern worldwide, due to the negative impacts on Air Quality. Being colorless and odorless, Rn cannot be detected by humans. Natural/geogenic Rn contribution to indoor air is considered a leading cause of lung tumors by the World Health Organization. Portugal implemented the 2013/59/Euratom directive in 2018, establishing ionizing radiation guidelines with an indoor air Rn maximum of 300 Bq/m3.

Guarda district (Portugal) is known for the natural geogenic Rn emissions and its impact on indoor Air Quality. A preliminary indoor Rn gas monitoring study was undertaken in 2019 (3 months period, March to May) in all the public schools (nursery to high school) of of Guarda city. A mean concentration of 1145 Bq/m3 was monitored, with a maximum value of 3604 Bq/m3 in a nursery school. From the twenty schools monitored, only five schools presented indoor Rn concentration bellow the Portuguese legislation and none bellow the WHO guideline of 100 Bq/m3. These results displayed an urgent and mandatory need for advanced and intensive air monitoring campaigns and assessment of implications on human health, especially in children during school hours, where they can stay up to 10 h/day.
Comparison and generalization of GNSS satellite attitude models
Authors: Strasser Sebastian , Banville Simon , Kvas Andreas , Loyer Sylvain , Mayer-Gürr Torsten
Published: March 2021

Global navigation satellite system (GNSS) constellations such as GPS, GLONASS, Galileo, and BeiDou and the Japanese regional system QZSS apply various satellite attitude modes during eclipse season, which is the period when the Sun is close to the orbital plane of the satellite. Due to different satellite manufacturers and technological advances over time, these modes can vary between constellations but also between different satellite types within a constellation. For some constellations, namely Galileo and QZSS, the satellite attitude law has been officially published by the satellite operator. For most other GNSS satellite types, researchers have developed attitude models, for example using reverse kinematic precise point positioning, that approximate the actual attitude behaviour.

Outside of eclipse seasons, GNSS satellites generally apply either a nominal yaw-steering or an orbit normal attitude law. While both modes point the antennas towards Earth, the former yaws the satellite around the antenna axis to point the solar panels towards the Sun, while the latter always keeps a fixed yaw angle. When a satellite applying a yaw-steering law is in eclipse season and close to the orbit noon or midnight point, it may have to yaw faster than physically possible to keep the nominal attitude. The various attitude modes used by the satellites aim to prevent this scenario by applying a modified attitude law during this period, for example by yawing at a constant rate around orbit noon/midnight or by switching to orbit normal mode.

Comparisons of attitude files generated by analysis centers of the International GNSS Service (IGS) within the scope of its 3rd reprocessing campaign show significant differences in some cases. This contribution compares all available attitude models with the aim of finding similarities that allow for generalization, which in turn simplifies the implementation of the various attitude modes into GNSS software packages. The developed functions have been implemented into the open-source software GROOPS (https://github.com/groops-devs/groops), which makes them publicly available and documented.
Optimization of snow density parameter of Noah Land Surface Model using micro-genetic algorithm for estimating snow depth
Authors: Lee Ebony , Park Seon Ki
Published: March 2021

The Noah Land Surface Model (Noah LSM) estimates snow depth using snow water equivalent and snow density. The snow density is determined by snow compaction, snowmelt water storing, and density of fresh snowfall. The Noah LSM usually underestimates snow depth compared to the ground observations in Korea, which occurs from the beginning of snowfall. We performed an optimal estimation of parameters related to the density of fresh snowfall, using micro-genetic algorithm (μ-GA) that uses the evolution process concept through natural selection and mutation mechanism. Ground observations from 36 sites of the Korea Meteorological Administration, for the recent 10 years (May 2009 – April 2019), are used for offline forcing of the Noah LSM and evaluating the fitness function in μ-GA. Optimized parameters reduced the density of fresh snowfall, and improved the simulated snow depth. The root-mean-square error of snow depth decreased from 8.1 cm to 7.1 cm.
How spatial vegetation distribution affects soil erosion and sediment transport
Authors: Kuegler Malte , Hoffmann Thomas , Eichel Jana , Schrott Lothar , Schmidt Juergen
Published: March 2021

There are a multitude of factors that affect soil erosion and the process of sediment movement. One particular factor known to have a considerable impact is vegetation coverage within catchment areas.  Previous studies have examined the impact of vegetation cover on erosion. However, there is a lack of research on how the spatial distribution of vegetation influences erosion rates.

A greater understanding of hillslope erosion is fundamental in modelling previous and future topographic changes under various climate conditions. Here, the physical based erosion model EROSION 3D © is used to evaluate the impact of a variety of vegetation patterns and degrees of vegetation cover on sediment erosion and transport. The model was applied on a natural catchment in La Campana (Central Chile). For this purpose, three different vegetation patterns were created: (i) random distribution, (ii) water-dependent distribution (TWIR) and (iii) banded vegetation pattern distribution. Additional to this, the areas covered by vegetation generated in the first step were expanded by steps of 10% [0...100%]. The Erosion3D © model then was applied on all vegetation patterns and degrees of cover.

Our results show an initial increase of soil erosion with increasing plant coverage within the catchment up to a certain cover threshold ranging between 10 and 40%. At larger vegetation cover soil erosion rates decline. The strength of increase and decline, as well as the cover-threshold is strongly conditioned by the spatial vegetation pattern. In the light of this, future research should pay particular attention to the properties of the plants and their distribution, not solely on the amount of biomass within catchment areas.
Can Biochar retain water in arid climates?  
Authors: Al Nofeli Naeema , Worrall Fred
Published: March 2021

Many studies have indicated that biochar could retain water for an extended period of time. Very little has been demonstrated the behaviour of biochar in arid environments where water retention is vital. The United Arab Emirates is one of the warmest countries in the World where farmers enjoy harvesting more crops during winter, however, during summer date palm trees is one of the main sources of food.  About 44 million date palm trees produce approximately 20 Kilograms of palm frond waste per year per tree (which is around 0.88 million tons of date palm biomass annually). This waste is currently sent to landfills. In this study, we proposed that in the arid soil conditions found in the UAE, this date palm waste could be converted to biochar and used to improve the water holding capacity of UAE soils. Therefore, this study aimed to compare the water holding capacity of amendments of date palm frond (DPF) and its biochar in UAE soils in different local weather conditions (winter and summer). A mesocosm experiment was used to assess the treatments at summer and winter temperature conditions. For the mesocosm, there were 6 different biochar and DPF treatments (1%, 3%, 6%, 12%, 15% and 18% biochar or DPF in soil) along with the controls (sharp sand, DPF biochar and DPF). The experiment was divided into 3 cycles with varying modified humidity. The impact of the experimental treatments was assessed using ANOVA. Both biochar and DPF had no significant effect during the first two cycles (wet and dry) but during the third cycle, the DPF had a 1% better water holding capacity than biochar. Given the mass loss of 5.7% during the production of biochar from DPF. It would seem that the best option is simply use collected date palm fronds. Therefore, further investigations are being processed to assess water binding capacity and physiochemical properties of the biochar, DPF and soil. 

 

 

 

 
ULF wave transmission across collisionless shocks: 2.5D local hybrid simulations
Authors: Kajdič Primož , Pfau-Kempf Yann , Turc Lucile , Dimmock Andrew , Palmroth Minna
Published: March 2021

We study the interaction of upstream ultra-low frequency (ULF) waves with collisionless shocks by analyzing the outputs of eleven 2.5D local hybrid simulation models. Our simulated shocks have Alfvénic Mach numbers between 4.29-7.42 and their θBN angles are 15º, 30º, 45º and 50º. Thus all are quasi-parallel or marginally quasi-perpendicular shocks. Upstream of all of the shocks the ULF wave foreshock develops. It is populated by transverse and compressive ULF magnetic field fluctuations that propagate upstream in the rest frame of upstream plasma. We show that the properties of the upstream waves reflect on the properties of the shock ripples. We also show that due to these ripples, as different portions of upstream waves reach the shocks, they encounter shock sections with different properties, such as the downstream magnetic field and the orientation of the local shock normals. This means that the waves are not simply transmitted into the downstream region but are heavily processed by the shocks. The identity of upstream fluctuations is largely lost, since the downstream fluctuations do not resemble the upstream waves in their shape, waveform extension, orientation nor in their wavelength. However some features are conserved. For example, the Fourier spectra of upstream waves present a bump or flattening at wavelengths corresponding to those of the upstream ULF waves. Most of the corresponding compressive downstream spectra also exhibit these features, while transverse downstream spectra are largely featureless.
3-D Qp and Qs Seismic Attenuation for the Central Alps and their Foreland
Authors: Lanza Federica , Diehl Tobias , Eberhart-Phillips Donna , Herwegh Marco , Fäh Donat , Wiemer Stefan
Published: March 2021

In the framework of the SeismoTeCH project, which aims at advancing our understanding of seismotectonic processes in Switzerland, we present the first 3-D attenuation model of the upper crust for the Central Alps and their northern foreland. The 3-D inversions derive the quality factor Q (1/attenuation) using path attenuation t∗ observations for 4,192 distributed earthquakes recorded on permanent and temporary stations, including both velocity and acceleration records for the period 2002-2019. We followed a procedure of gradational inversions, in which a series of inversions with increasingly grid complexity are performed, with the goal of obtaining a useful Q model everywhere despite the varied data distribution. The Qs and Qp results show large-scale features in the upper crust, which are consistent with a recently improved high-resolution velocity models of the same region and serve to refine the interpretations of crustal structures from Vp and Vp/Vs. For example, the foreland region of southern Germany and northern Switzerland show a low Q crustal block bounded by high Q regions in the uppermost layer between -2.5 and 2.0 km depth. This markedly correlates with the overlying surface geology, where low Q areas coincide with the Molasse Basin, and the transition between low and high Q regions outline the geological boundary between the Molasse and the Mesozoic sediments towards north and the Alpine front to the south. At depths ranging between 2.0 - 6.5 km, low Q is imaged along the Rhone valley in the Valais in southwest Switzerland. This region presents the transition between the Centrals and Western Alps and hosts the presently seismically most active fault zones. As the attenuation of fractured areas is enhanced by fluids, low Q values may relate here to distributed microfractures that produce greater fracture connectivity and permeability in a relatively higher strain-rate zone. These geophysical constraints seem to support crustal scale fluid flow along fracture networks as manifest by the prominent occurrence of hot springs in this area. On the other hand, the moderate-to-high Qs and Qp (400-800) along with low Vp/Vs ratio and high Vs observed in the external Aar Massif could be indicative of metamorphic processes leading to different Vp/Vs ratios compared to the basement in the northern foreland (Black Forest Massif), and possibly image the continuation of the massif 20-30 km further to the northeast. In combination with recently developed Vp and Vs velocity models, the developed 3-D attenuation models provide additional constraints in terms of composition and physical properties of the uppermost crust of the central Alps as well as crucial input for next generation seismic hazard models of Switzerland, allowing for a more realistic prediction of earthquake related ground motions.
Topographic stress influences on bedrock landslides
Authors: Li Gen , Moon Seulgi
Published: March 2021

Bedrock landslides are a major hazard, with influences on erosion, weathering, and organic carbon transfer. Understanding the controls of the magnitudes of bedrock landslides is central for predicting and managing landslide hazards. Previous studies hypothesize that the geometric sizes of bedrock landslides are controlled by bedrock fractures that set the strength of subsurface materials. Recent studies show that topographic stress, resulted from the interplay between tectonics stress and topography, sets the extent of subsurface open-fracture zones, but how topographic stress affects bedrock landslides remains less well understood. Here, we investigate whether topographic stress influences the magnitudes of bedrock landslides in a granitic terrain in the eastern Tibetan mountains where landslides prevail. We constructed two new landslide inventories of earthquake- and rainfall-induced landslides in the study area. We examine the relationships between landslide sizes and the proxies for topographic stress, topography, and landslide triggers (i.e. seismic shaking and rainfall). We demonstrate that topographic stress exerts a dominant control on the sizes of large bedrock landslides. Our study provides new insights into how landslides occur in different topographic and tectonic conditions, as well as how topographic stress influences earth surface processes.
Cyclic soil-root mechanical interaction
Authors: Leung Anthony , Karimzadeh Ali Akbar , Wu Zhaoyi
Published: March 2021

Plant roots have been considered to be effective to reinforce shallow soil slopes under rainfall conditions. Recent evidence from geotechnical centrifuge modelling shows that plant roots could improve earthquake-induced slope stability and reduce slope crest settlement. However, the underlying fundamental mechanisms of soil-root mechanical interaction against seismic loading are unclear. Although there has been a large volume of studies focusing on root reinforcement, cyclic soil-root mechanical interaction has rarely been investigated. Moreover, whether plant roots could reduce the liquefaction potential of rooted soil. This presentation will present some new test data and evidence about (1) cyclic root biomechanical behaviour and (2) cyclic responses of root-reinforced soil. In part (1), results of cyclic uniaxial tensile tests on roots of a wide diameter range will be presented, including any root hardening or softening and change in the size of hysteresis loops under displacement-controlled loading condition. Special attention will be paid on any observation of cyclic-induced root mechanical fatigue. In part (2), results of a comprehensive set of monotonic and cyclic triaxial tests on rooted soil will be presented. The cyclic behaviour observed will be interpreted through the monotonic behaviour observed along both the triaxial compression and extension paths. Any change in soil failure mechanism from limited flow failure to cyclic mobility due to plant roots, and how/when this change occurs at different root volume and cyclic stress ratio, will be discussed in detailed. A new attempt to interpret the liquefaction resistance through an energy-based approach will be made to evaluate the energy dissipation mechanism in rooted soils.
Significant sources of bias in temperature measurements by rotational Raman lidar, and mitigation in the French mobile system WALI
Authors: Totems Julien , Chazette Patrick , Baron Alexandre
Published: March 2021

Lidars using rotational Raman backscattering to monitor the temperature profile in the low troposphere offer enticing perspectives for applications in weather prediction, as well as studies of aerosol and water vapor interactions, when deriving simultaneously relative humidity and aerosol optical properties. We describe the technical choices made during the design and calibration of the new temperature Raman channels for the mobile Weather and Aerosol Lidar (WALI), going over the sources of bias and uncertainty stemming from the different optical elements of the instrument. The impacts of interference filters and non-common-path differences between Raman channels, and their mitigation, are particularly investigated; without countermeasures, we find the theoretical magnitude of the highlighted biases can be much larger than the targeted absolute accuracy of 1°C defined by the World Meteorological Organization (WMO). Effective measurement errors are quantified using numerical end-to-end simulations and numerous radiosoundings launched close to the lidar location. Our aim is to fully discuss design choices and sources of bias which have been little reported in the literature. An application of the WALI measurements during heat wave conditions in the summer of 2020 will also be presented, and compared to ERA5 weather model reanalyses.
Analysis of potential seismic sources of tsunamis in the Black Sea region, using data from various catalogues
Authors: Oynakov Emil , Dimitrova Liliya , Pashova Lyubka , Dragomirov Dragomir
Published: March 2021

Low-laying territories along the Black Sea coastal line are more vulnerable to the possible high (long) waves due to tsunami events caused by strong earthquakes in the active seismic regions. Historically, such events are rare in the Black Sea region, despite some scientific evidence of tsunamis and their recordings through continuous sea-level observations with tide gauges built in certain places along the coast. This study analyses seismic data derived from different international earthquake catalogues - NEIC, ISC, EMSC, IDC and Bulgarian national catalogue (1981 - 2019). A catalogue of earthquakes within the period covering the historical to the contemporary seismicity with magnitudes M ≥ 3 is compiled. The data are processed applying the software package ZMAP, developed by Stefan Wiemer (http://www.seismo.ethz.ch/en/research-and-teaching/products-software/software/ZMAP/index.html). The catalogues' completeness is calculated to assess the reliability of the historical data needed to assess the risk of rare tsunami events. The prevailing part of the earthquakes' epicentres are in the seismically active regions of Shabla, the Crimean peninsula, the east and southeast coast of the Black Sea forming six main clusters, which confirmed previous studies in the region. In these areas, several active and potentially active faults, which can generate tsunamigenic seismic events, are recognized.

Acknowledgements: The authors would like to thank the Bulgarian National Science Fund for co-funding the research under the Contract КП-СЕ-КОСТ/8, 25.09.2020, which is carried out within framework of COST Action 18109 “Accelerating Global science In Tsunami HAzard and Risk analysis” (AGITHAR; https://www.agithar.uni-hamburg.de/).
Millet arrived in the South China Coast around 5,500 years ago
Authors: Dai Jinqi , Cai Xipeng , Jin Jianhui , Ge Wei , Huang Yunming , Wu Wei , Xia Taoqin , Li Fusheng , Zuo Xinxin
Published: March 2021

Crop dispersal has long been recognised as an important topic in agricultural archaeology and food globalisation. One of most pressing questions facing archaeologists is determining when and where millet arrived in the South China Coast. Our study focused on the millet phytoliths remains from three Neolithic sites in southeast coastal Fujian. Multiple dating methods, including charred carbon dating, phytolith carbon dating, and optically stimulated luminescence were used to construct the chronologies of the sites. The dating results showed that BTS was initially occupied at approximately 5,500 cal a BP. The millet phytoliths recovered in this study are likely the earliest millet remains found in Fujian, suggesting that millet arrived in the South China Coast at least 5,500 years ago. However, questions about whether millet agriculture in northern China dispersed southward through the inland or coastal routes remain unanswered. Given that millet remains were found in Jiangxi and northern Fujian – two important gaps in the inland route – no earlier than 5,000 cal a BP, it seems that the millet remains recovered from the coastal sites of Fujian might have dispersed following a coastal route from northern China. Nevertheless, Fujian is an important junction of the coastal route for the dispersal of millet from northern China. These findings not only provide new insights to millet dispersal routes in China, but also have significant implications for crop communications between Taiwan and mainland China during the Neolithic age.

 

 
Novelly discovered post-mid-Eocene sinistral slip in the eastern Oman Mountains: widely distributed shear with wrench-fault assemblage related to Arabia-India convergence
Authors: Mattern Frank , Bolhar Robert , Scharf Andreas , Scharf Katharina , Mattern Paul , Callegari Ivan
Published: March 2021

The geology of the Oman Mountains was shaped by the SW-directed obduction of allochthonous deep-sea rocks (Hawasina), trench-facies rocks (Haybi) and oceanic lithosphere (Semail Ophiolite) onto Arabian autochthonous shelf carbonates during the Late Cretaceous. Locally, the resulting obduction orogen was overprinted by significant post-obductional extension. NNE-directed extension occurred during at least two episodes which took place from the latest Cretaceous to early Eocene and late Eocene to Oligocene/Miocene, respectively. Moreover, the Oman Mountains, between the eastern Batinah Coastal Plain and the Sur area (Qalhat Fault) display numerous ~N/S-oriented folds and reverse faults. These structures overprinted mid-Eocene to at least Oligocene/Miocene formations (i.e., the Seeb to Barzaman formations).

Detailed structural/field work and satellite image analyses provide ample evidence that these ~N/S-compressional features are cogenetic with ~WNW to NW-striking sinistral faults. All these post-mid-Eocene structures are part of one major left-lateral WNW- to NW-striking shear zone from the Batinah Coastal Plain in the NW to the Batain area in the SE. Sinistral shearing is localized along the southwestern margin of the Saih Hatat Dome, crosses the Fanja area and continues to the northern part of the Jabal Akhdar Dome (Jabal Nakhl Subdome). The straight southwestern margin of the Saih Hatat Dome may correlate with a Permo-Triassic major extensional fault, active during the Pangea rifting. Shearing also affected rocks northeast of this zone, i.e., within the Salma Plateau and the Rusayl Embayment. Thus, shearing affected an area of 250 km by 40 km in width. We term this shear zone hereafter the “Hajar Shear Zone” (HSZ). The amount of sinistral shearing is unknown due to the absence of markers and wide strain distribution, but is likely to be at the order of a few tens of kilometers.

The cause for the WNW-directed sinistral shearing is the overall E/W-directed shortening between the Arabian and Indian plates. During shortening, a pre-existing WNW-striking basement fault zone was reactivated, creating the HSZ. A G-Plates reconstruction between the two plates reveals an ~8° counter-clockwise rotation of India (with respect to fixed Arabia) between 32.5 and 20 Ma, resulting in ~150 km E/W-shortening between both plates at the easternmost tip of Arabia. The area northeast of the HSZ underwent most E-W-shortening. The 150 km interplate E/W-shortening is the maximum value for sinistral shearing along the HSZ and other faults. Some of the shortening may have been absorbed offshore Oman across the Owen Basin and/or along the continental/oceanic transitions of both plates.
Vegetation responses to climate extremes recorded by remotely sensed atmospheric formaldehyde
Authors: Morfopoulos Catherine , Müller Jean-François , Stavrakou Trissevgeni , Bauwens Maite , De Smedt Isabelle , Friedlingstein Pierre , Prentice Ian Colin , Regnier Pierre
Published: March 2021

Accurate monitoring of vegetation stress is required for better modelling and forecasting of primary production, in a world where heatwaves and droughts are expected to become increasingly prevalent. Variability in formaldehyde (HCHO) concentrations in the troposphere is dominated by local emissions of short-lived biogenic (BVOC) and pyrogenic volatile organic compounds. BVOCs are emitted by plants in a rapid protective response to abiotic stress, mediated by the energetic status of leaves (the excess of reducing power when photosynthetic light and dark reactions are decoupled, as occurs when stomata close in response to water stress). Emissions also increase exponentially with leaf temperature. New analytical methods for the detection of spatiotemporally contiguous extremes in remote-sensing data are applied here to satellite-derived atmospheric HCHO columns. BVOC emissions are shown to play a central role in the formation of the largest positive HCHO anomalies. Although vegetation stress can be captured by various remotely sensed quantities, spaceborne HCHO emerges as the most consistent recorder of vegetation responses to the largest climate extremes, especially in forested regions.
Microplastics in the water of the Volga River: the results of a summer 2020 field survey
Authors: Lisina Anastasia , Platonov Maxim , Lomakov Oleg , Frolova Natalia , Sazonov Alexey , Shishova Tatiana
Published: March 2021

In spite of the fact that present day Russia makes only a small contribution to the global industry of polymers and polymer products, their production increases steadily, which leads to a rise in the concentration of microplastics (MP) in the surface waters including rivers, where MP enters with surface runoff and waste water. 

Since the problem of microplastics pollution of freshwater bodies in Russia has not received sufficient attention, in July-August 2020 the non-profit foundation “Clean Hands, Clean Rivers” together with the Faculty of Geography of M.V. Lomonosov Moscow State University, conducted a comprehensive hydrological and environmental survey along the entire Volga river, from its source to its mouth. It included water sampling and determination of microplastics, nutrients and heavy metals. The main hydrochemical indicators of river water were also monitored.

Water samples were taken upstream and downstream of several large cities - Tver, Nizhny Novgorod, Cheboksary, Kazan, and Volgograd. To collect water samples for MP, a specialized device "manta" with nets for filtration at 300 µm was used; further analysis of MP fragments was carried out by the method of differential scanning calorimetry.

The analysis of 34 water samples allowed us to determine the average concentration of MP in the surface water layer of the Volga river which accounted for 0.901 part./m3.

MP particles were found in all samples taken. The concentrations ranged from 0.156 to 4.100 part./m3. The maximum MP concentrations were recorded in large cities downstream of the sewage treatment plants. For Kazan, Tver, Nizhny Novgorod and Volgograd they reached 4.100,  3.769, 1.907, and 1.344 part./m3, respectively. The role of large settlements as sources of MP in the Volga water was revealed.

The minimum MP concentrations were recorded upstream of the large cities showing relatively stable levels of 0.25 part./m3. The lowest MP content (0.156 part./m3) was revealed in the downstream area of the Cheboksary reservoir near Cheboksary. The results of weighing MP particles showed that their average concentration in the Volga water is 0.212 mg/m3.

In each of the investigated samples, particles of three determined fractions - fragments, fibers and films - were found, however, their ratio was not constant. On average, the proportion of fragments and films in the Volga water was 41% and 37%, respectively, and share of fibers accounted for 22%.
Testing the synchronicity of Pleistocene biostratigraphic events in the central Arctic – Do we have a consistent biostratigraphic framework?  
Authors: Vermassen Flor , Coxall Helen K. , West Gabriel , O'Regan Matt
Published: March 2021

Harsh environmental and taphonomic conditions in the central Arctic Ocean make age-modelling for Quaternary palaeoclimate reconstructions challenging. Pleistocene age models in the Arctic have relied heavily on cyclostratigraphy using lithologic variability tied to relatively poorly calibrated foraminifera biostratigraphic events. Recently, the identification of Pseudoemiliania lacunosa in a sediment core from the Lomonosov Ridge, a coccolithophore that went extinct during marine isotope stage (MIS) 12 (478-424 ka), has been used to delineate glacial-interglacial units back to MIS 14 (~500 ka BP). Here we present a comparative study on how this nannofossil biostratigraphy fits with existing foraminifer biohorizons that are recognised in central Arctic Ocean sediments. A new core from the Alpha Ridge is presented, together with its lithologic variability and down-core compositional changes in planktonic and benthic foraminifera. The core exhibits an interval dominated by Turborotalita egelida, a planktonic foraminifer that is increasingly being adopted as a marker for MIS11 in sediment cores from the Amerasian Basin of the Arctic Ocean. We show that the new age-constraints provided by calcareous nannofossils are difficult to reconcile with the proposed MIS 11 age for the T. egelida horizon. Instead, the emerging litho- and coccolith biostratigraphy implies that Amerasian Basin sediments predating MIS5 are older than the egelida-based age models suggest, i.e. that the T. egelida Zone is older than MIS11. These results expose uncertainties regarding the age determination of glacial-interglacial cycles in the Amerasian basin and point out that future work is required to reconcile the micro- and nannofossil biostratigraphy of the Amerasian and Eurasian basin.
Bicovariance and Bispectrum of ENSO index and its impact in nonlinear predictability 
Authors: Pires Carlos , Hannach Abdel
Published: March 2021

El Niño Southern Oscillation (ENSO) index has been shown as a non-Gaussian and nonlinear stochastic process. Here we assess the statistical significance of non-Gaussianity and non-linearity through the analysis of third-order statistics of El Niño 3.4 index in the period 1870–2018, namely the bicovariance (lagged third-order moments) and bispectrum (its 2D Fourier transform). The analysis of bicovariance reveals a tendency for extreme (weak) ENSO signal in the Boreal Spring to be followed by la Niñas (El Niños) in the forthcoming Boreal Winter, thus contributing for a nonlinear attenuation of the ENSO Spring Predictability Barrier. The bispectrum provides a spectral decomposition of skewness in a similar way of the spectral decomposition of variance.  Positive and negative real bispectrum values identify triadic phase synchronizations (at frequencies f1, f2 and f1+f2, mostly in the period range 2–6 years) contributing respectively to extreme El Niños and La Niñas. The known positive ENSO skewness and the main features of the ENSO bicovariance and bispectrum are shown to be well reproduced by fitting a bilinear stochastic model where the influence of non-observed variables is simulated by a delayed multiplicative noise, being able to generate non-Gaussianity and non-linearity. The model shows improved forecasts, with respect to benchmark linear models, up to four trimesters ahead, especially of the amplitude of extreme El Niños. The authors would like to acknowledge MISU (Meteorological Institute at Stockholm University) and the financial support FCT through project   UIDB/50019/2020 – IDL and project JPIOCEANS/0001/2019 (ROADMAP: ’The Role of ocean dynamics and Ocean–Atmosphere interactions in Driving cliMAte variations and future Projections of impact–relevant extreme events’).
Capturing watershed water balance with a physically-based two-hydrological-variable model: Application to the Little Washita basin
Authors: Picourlat Fanny , Mouche Emmanuel , Mugler Claude
Published: March 2021

Hydrological processes import across scales is known to constitute a key challenge to improve their representation in large-scale land surface models. Since these models describe continental hydrology with vertical one dimensional infiltration and evapotranspiration, the challenge mainly resides in the dimensionality reduction of the processes. Departing from the catchment three-dimensional scale, previous work has shown that an equivalent two-dimensional hillslope model is able to simulate long term watershed water balance with good accuracy. This work has been done on the Little Washita basin (Ok, USA) using the integrated code HydroGeoSphere. Following this framework, we show that hillslope hydrology can be described by using realistic simplifying assumptions, such as linear water table profile. These assumptions allow the writing of an analytical model relying on two hydrological variables: the seepage face extension, which describe the intersection length between the water table and the land surface, and the water table slope. The last step of the work will be to use these key variables and this simplified description of the driving processes for importing small-scale hydrological processes into large-scale models.
A new IoT geosensor network for cost-effective landslide early warning systems
Authors: Gamperl Moritz , Singer John , Thuro Kurosch
Published: March 2021

Worldwide, cities in mountainous areas struggle with increasing landslide risk as consequence of global warming and population growth, especially in low-income informal settlements. For these situations, current monitoring systems are often too expensive and too difficult to maintain. Therefore, innovative monitoring systems are needed in order to facilitate low-cost landslide early warning systems (LEWS) which can be applied easily.

Based on technologies such as micro-electro-mechanical systems (MEMS) sensors and the LoRa (Long Range) communication standard, we are currently developing a cost-effective IoT (Internet of Things) geosensor network. It is specifically designed for local scale LEWS in informal settlements.

The system, which is open source and can be replicated without restrictions, consists of versatile LoRa sensor nodes which have a set of MEMS sensors (e.g. tilt sensor) on board and to which various additional sensors can be connected. The nodes are autonomous and can operate on standard batteries or solar panels. The sensor nodes can be installed on critical infrastructure such as house walls or foundations. Two of the possible additions are the Subsurface Sensor Node and the Low-Cost Inclinometer. Both are installed underground and offer tilt- and groundwater-measurements of the subsurface.

Complemented with further innovative measurement systems such as the Continuous Shear Monitor (CSM) and a flexible data management and analysis system, the newly developed monitoring system offers a great cost to benefit ratio and easy application for similar sites and LEWS, especially in urbanized areas in developing countries.

This work is being developed as part of the project Inform@Risk, where the monitoring system will be installed as part of an early warning system in Medellín, Colombia. It is funded by the German Ministry of Education and Research (BMBF).
Seasonal Variability of Relationship between Main Ionospheric Characteristics and Solar/Geomagnetic Indices via Graphical Models of Conditional Independences
Authors: Podolská Kateřina , Koucká Knížová Petra , Chum Jaroslav
Published: March 2021

We investigated seasonal variations of relationships between main ionospheric characteristics and solar and geomagnetic indices in longitudinal perspective. We consider statistically significant differences in connections of ionospheric response to the F10.7cm, R, and Kp indices on seasonal time-scales during years 1975 – 2010 covering 21st – 23rd Solar Cycles. The periods of 21 days before and after Winter/Summer Solstices and Vernal/Autumnal Equinoces are considered as season. The foF2 time series in our analysis represent measurements of daily observational data which were obtained using mid-latitude (41.4°N – 54°N) ionosondes (Chilton, Slough RL052/SL051, Juliusruh/Rugen JR055, Boulder BC840). We used local time noon 5-hour foF2 averages. For the investigation, we used seasonal differences method of conditional independence graphs (CIG) models. Significant seasonal variations are visible during ascending and descending phases of Solar cycles.