bluuebunny/crossref_metadata_2025 huggingface dataset:
Prebiotic synthesis in volcanic discharges: lightning, porous ash and volcanic gas atmospheres
Authors: Springsklee Christina , Steiner Thomas , Geisberger Thomas , Scheu Bettina , Huber Claudia , Eisenreich Wolfgang , Cimarelli Corrado , Dingwell Donald Bruce
Published: March 2020

The emergence of the first organic molecules as a fundamental step in the prebiotic assembly of life remains enigmatic. Lightning has been considered as a potential energy source for the synthesis for first organic molecules. The iconic abiotic synthesis experiments: the discharge experiments performed in 1953 by Miller and Urey [1] under simulated reducing atmosphere conditions were conducted in the absence of any geomaterial substrate. Further, new views about the composition of the Early Earth’s atmosphere have been developed which require a revisiting of the Miller experiment.

Volcanic lightning associated with volcanism provides a possible energy source, a variety of different volcanic gases and possible catalysts to synthesize a variety of primitive organic molecules. Volcanic ash particles are known for their porosity, high surface area and significant surface reactivity. Volcanic plumes themselves provide a high variety of volcanic gases including, but not limited to reducing ones, and therefore may enlarge the spectrum for possibly available gas compositions in the Early Earth atmosphere.

Recent laboratory studies have successfully recreated near-vent volcanic lightning under laboratory conditions [2,3]. We will present first insights from volcanic discharge experiments under different atmospheric compositions, varying in CO2, and N2 composition to mimic some first Early Earth conditions. Special focus is given to the role of ash particles as a catalyst and container as well as the influence of gas composition on the yield of organic compounds.

 

[1] Miller, S.L. (1953). A production of amino acids under possible primitive earth conditions. Science, 117, 528-529.  

[2] Cimarelli, C., Alatorre-Ibargüengoitia, M.A., Kueppers, U., Scheu, B. and Dingwell, D.B. (2014). Experimental generation of volcanic lightening. Geology, 42, 79-82.

[3] Gaudin, D. and Cimarelli, C. (2019). The electrification of volcanic jets and controlling parameters: A laboratory study. EPSL, 513, 69-80.

 
Dynamics of moving knots in a solar prominence observed by New Vacuum Solar Telescope
Authors: Bi Yi
Published: March 2020

In this report, we present a prominence observed by New Vacuum Solar Telescope (NVST) in Hα wavelength.  We use morphological approach to identify the rising or descending knots in the prominence. The rising knots are often found on the top of the prominence, while more knots are seen to descend from anywhere of the prominence.

The optical flow, referring to the apparent proper motion of a feature across the image plane, may be used to determine the velocity field from two images. The technique of local correlation tracking (LCT) optical flow has been widely used in the solar research. The Demon algorithm, which has been  used to match medical image, performs image-to-image matching by determining the optical flow between two images. We have examined the performance of the two methods applying the Hα images, and we noted that the Demon algorithm outperforms traditional LCT  methods.

The result of Demon optical flow allows us to estimate the velocity and acceleration of the moving knots. The descending speed of the knots near the solar surface is higher than that far away from the solar surface. This indicate that most of knots are more possible to descend across the horizontal magnetic field.
Evolution of brittle structures in plagioclase-rich rocks at high-grade metamorphic conditions – Linking laboratory results to field observations
Authors: Incel Sarah , Renner Jörg , Jamtveit Bjørn
Published: March 2020

Plagioclase-rich lower crustal granulites exposed on the Lofoten archipelago, N Norway, display pseudotachylytes, reflecting brittle deformation, as well as ductile shear zones, highlighting plastic deformation. Pristine pseudotachylytes often show no or very little difference in mineral assemblage to their host-rocks that exhibit limited, if any, metamorphic alteration. In contrast, host-rock volumes that developed ductile shear zones exhibit significant hydration towards amphibolite or eclogite-facies assemblages within and near the shear zones. We combine experimental laboratory results and observations from the field to characterize the structural evolution of brittle faults in plagioclase-rich rocks at lower crustal conditions. We performed a series of deformation experiments on intact granulite samples at 2.5 GPa confining pressure,  a strain rate of 5×10-5 s-1,  temperatures of 700 and 900 °C, and total strains of either ~7-8 % or ~33-36 %. Samples were either deformed ‘as-is’, i.e. natural samples without any treatment, or with ~2.5 wt.% H2O added. Striking similarities between the experimental and natural microstructures suggest that the transformation of precursory brittle structures into ductile shear zones at eclogite-facies conditions is most effective when hydrous fluids are available in excess.
Thickness of talus deposits on Fugleberget hillside (SW Spitsbergen) in the light of the theories of slope development in periglacial areas
Authors: Dolnicki Piotr , Grabiec Mariusz
Published: March 2020

Periglacial areas are very sensitive to contemporary climate change. Rate of morphogenetic processes depends on numerous factors, including the most important: warming of air and ground, increase of precipitation (extreme rainfalls in particular) and shortening of snow cover duration. The dynamics of above mentioned processes may effectively modify conventional slope development models. The paper shows structure of selected talus slopes on Fugleberget hillside based on field observations and radar (GPR) sounding. Then the results have been compared to the classical slope models. The radar survey in April and May 2014 used RAMAC CU II Malå GeoScience system equipped with 30 MHz RTA antenna (Rough Terrain Antenna). Six GPR profiles of various length have been collected along the talus axes and transversally on Fugleberget hillside and partly on Hansbreen lateral moraine. According to the radar sounding maximum thickness of the debris deposits is 2530 m. Weathered material is getting thicker towards terminal part of the screes and debris deposits overlap marine sediments. The morphometry of the talus slopes shows that their current forms differ from conventional slope models, what can result from significant acceleration of geomorphic processes due to climate change
Benthic Foraminifera as indicative of Austral Summer monsoon precipitation and winter monsoon wind-driven upwelling
Authors: Eichler Patricia , Billups Katharina , Ravelo Ana Christina , Vital Helenice
Published: March 2020

During IODP Expedition 363, a hemipelagic sediment succession was retrieved for the first time off NW Australia (Site U1483: 13°5.24ʹS, 121°48.25ʹE, water depth: 1733 m, sedimentation rate: ~10 cm/kyr). This carbonate- and clay-rich sequence provides an ideal archive to monitor intensity and variability of the Australian Monsoon (AM) and to better constrain monsoon sensitivity to changes in radiative forcing. Due to the location at the southern edge of the largest amplitude seasonal swing of the Intertropical Convergence Zone (ITCZ) within the large-scale Asian-Australian monsoon system, the AM subsystem is sensitive to tropical hydroclimate variability. However, this sensitivity to changing climate boundary conditions such as ice volume and greenhouse gas concentrations remain poorly understood across the Calabrian, in the Pleistocene Epoch (add ages?). Here we report on benthic foraminiferal assemblages as a tracer for terrigenous runoff (Austral Summer monsoon precipitation). We find shallow, fresh water-tolerant to transitional environments species Bolivina striatula, Buliminella elegantissima, Dentalina spp., Oolina sp., and paleo productivity indicator Melonis spp (winter monsoon wind-driven upwelling) from 1.34 Ma. through 1.61Ma. Principl component analysis (PCA) indicates that Melonis is present in 4 out of 5 PCA axes. It prefers organic matter in a more altered form, and migrates in the sediment depending on the quality of the organic matter supply and remineralization, which indicates surface upwelling during this time. The genera Stilostomella spp. is present in 3 out of 5 axes, and it is indicative of intermediate water temperature. These records will be compared to C org wt (%), TN wt (%) and a benthic foraminiferal stable isotope record to related faunal patterns to carbon cycling and global climate.

 

 
Comparing the discrimination power of contrasted sediment tracing techniques to quantify the impact of nickel mining on river and lagoon siltation in New Caledonia
Authors: Sellier Virginie , Evrard Olivier , Navratil Oldrich , Laceby J. Patrick , Allenbach Michel , Lefèvre Irène
Published: March 2020

Open-cast mining has strongly increased soil erosion and the subsequent downstream transfer of sediments in river systems. New Caledonia, a French island located in the south-west Pacific Ocean and currently the world's 6th largest nickel producer, is confronted in particular to unprecedented sediment pollution of river systems: hyper-sedimentation. A significant fraction of this sediment is likely originating from tributaries draining nickel mining sites. Nevertheless, the contribution of this sediment source has not been quantified and this estimation is required to guide the implementation of efficient management measurements to mitigate fine sediment supply to New Caledonian river systems and lagoons. To this end, a pilot sediment tracing study has been conducted in one of the first areas exploited for nickel mining, the 397-km² Thio River catchment.

Sediment deposits were collected after two major floods (~10 yr return period): the tropical depression of February 25, 2015 and Cyclone Cook on April 10, 2017. Sources (n=25) were sampled on (i) tributaries draining mines, and (ii) tributaries draining ‘natural’ areas affected by landslides occurring frequently in the region, and sediment (n=19) on (iii) the main stem of the Thio River. In addition, (iv) a 1.60 m long sediment core was collected in the Thio river deltaic floodplain in April 2016. Six sediment tracing techniques were tested based on the following properties: fallout radionuclides, geogenic radionuclides, elemental geochemistry, colorimetric parameters and reflectance spectra.

Several of these methods were identified as relevant to the New Caledonian context and allowed to estimate the contributions of both mining and non-mining sources according to their variations both in space and time. In particular, the sedimentary contributions of mining sources were estimated between 65-68 % for the 2015 flood and 83-88 % for the 2017 flood. The impact of the spatial variability of precipitation was highlighted to explain the variations in the spatial contributions of the sources. The temporal variations in the contributions of the sources deduced from the analysis of the sediment core were interpreted at the light of the mining history in the Thio River catchment (pre-mechanization, mechanization, post-mechanization of mining activity). The contributions of mining sources were again dominant with an average contribution along the sedimentary profile of 74 ± 13 %.

In the future, similar studies should be carried out in other catchments draining mines in New Caledonia and potentially across similar South Pacific and other tropical islands.
Assessing climate change effects on the occurrence of hydrological landslides in Emilia Romagana ( Italy) region
Authors: Liu Yuexiao , Han Dawei , Pregnolato Maria
Published: March 2020

Over the past few decades, clear evidence has underlined that global climate has changed and this trend is projected to continue in the future. As a consequence, climate change concerns an increase in temperature and variations in rainfall patterns, which may be responsible for changes in landslide occurrences. In principle, landslide is supposed to respond to climate change correspondingly. However, the influence of climate change on landslide occurrences has not been defined quantitatively yet and whether the effect could exacerbate or reduce landslides impact on a regional scale is still unclear. Thus, this study aims to employ several meteorological factors to serve as a bridge to explore the intrinsic correlation between climate change and landslide occurrences.

To demonstrate the methodology, this paper illustrates the Emilia-Romagna region (Italy, historic data from 1979 to 2019) as a case study due to its high quality observation over past decades Firstly, we carry out an explorative temporal and spatial distribution characteristic analysis of meteorological factors including temperature, precipitation, evaporation and soil moisture to explore its change rule. In addition, data derived from the ERA5 dataset is calibrated with the observed data in the targeted zones in order to yield thresholds to estimate landslide risk. By using two types of thresholds, relationships between climate parameters and consequences such as landslide triggering, landslide event frequency, and landslide event magnitude are established. Furthermore, we calculate the exceedance probabilities and forecast the overall trend of occurrence of landslide influenced by climate change in the future.

The results show that there is an overall upward trend in the annual average temperature and soil moisture is found to decrease throughout these years; Hilly areas are more sensitive to changes in both temperature and precipitation compared with the coastal areas which is consistent with the variation of landslides occurence . The results provide useful foundation for further hydrological landslide risk management in the region.
Imaging the Sicily Channel Rift Zone (Central Mediterranean) with seismic ambient noise tomography.
Authors: Agius Matthew , Cammarano Fabio , Magrini Fabrizio , Faccenna Claudio , Funiciello Francesca , van der Meijde Mark
Published: March 2020

The tectonics of the Sicily Channel, located in the Central Mediterranean, are thought to be driven by the Calabrian back-arc system moving south-eastwards and the north moving African plate. The Channel is characterized by a seismically and volcanically active rift zone, which extends for more than 600 km in length offshore from the south of Sardinia to the south-east of Malta. Much of the observations we have today are either limited to the surface and the upper crust, or are broader and deeper from regional seismic tomography, missing important details about the lithospheric structure and dynamics. The project GEOMED () addresses this issue by processing all the seismic data available in the region in order to understand better the geodynamics of the Central Mediterranean.

We use seismic ambient noise recorded on more than 50 stations located on Algeria, Italy (Lampedusa, Linosa, Pantelleria, Sardinia (LISARD seismic network), Sicily), Libya, Malta, and Tunisia to generate high-resolution seismic tomography maps for the region at different depths. We measure Rayleigh-wave phase velocities with periods ranging from 5 to 100 seconds sampling through the entire lithosphere. We find that at short periods (<25 s), paths of station-pairs crossing across Africa and Italy have slower velocities than those crossing the Tyrrhenian and Ionian basins indicating that these paths are sampling thick continental crust. However, station pairs limited to the Sicily Channel Rift Zone (SCRZ) have faster phase velocities for periods > 20 s comparable to those beneath the basins suggesting that the SCRZ has a thinner crust. The seismic velocity maps are compared with the regional tectonics, seismicity, volcanic activity and other geophysical studies to present a more holistic understanding of the processes involved.

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 843696.
Estimation of Evapotranspiration using the Modified Hargreaves Equation by Genetic Algorithm
Authors: Kim Deokhwan
Published: March 2020

In this study, the Hargreaves monthly correction factor is presented to estimate the reference evapotranspiration. For the analysis, I used daily weather data from 1989 to 2018, at 67 meteorological stations located throughout the Korean peninsula.

A large number of more or less empirical methods have been developed over the last 50 years by numerous scientists and specialists worldwide to estimate evapotranspiration from different climatic variables. The FAO Penman-Monteith method is recommended as the sole ETo method for determining reference evapotranspiration. However, the Penman-Monteith method has the disadvantage of inputting a lot of weather data. In addition, there is a lack of meteorological data when using old historical data or as a test bed for developing countries.

In the case of the Hargreaves method, the reference evapotranspiration can be estimated only if the latitude, maximum and minimum temperatures of the meteorological station are known. However, the accuracy of the results is not as good as that of the Penman-monteith method. Thus, using the genetic algorithm method suggested the monthly correction factor of the Hargreaves method each station. The reference evapotranspiration amount calculated by Penman-Monteith was set as the true value, and the learning period of genetic algorithm was set from 1989 to 2013, and the validation period was set from 2014 to 2018.

In order to verify the model efficiency, the root mean square error decreased and the correlation coefficient increased when the monthly correction coefficient was applied to the reference evapotranspiration calculated by the Hargreaves method.

It is very important to estimate the reference evapotranspiration amount in order to develop the water long-term plan.

With the development of measuring equipment and technological capabilities, it is now possible to simulate the state of nature as if it were real, but many problems arise when using historical data or analyzing developing countries.

If the monthly correction coefficient suggested in this study is applied, it is possible to estimate the standard evaporation amount with a more approximate value.

 

Acknowledgements

 This research is supported by the Research Program (20200041-001) of Korea Institute of Civil Engineering & Building Technology 
The selection of adaptive region of geomagnetic map based on PCA and GA-BP neural network
Authors: Chong Yang , Zhao Dongqing , Xiao Guorui , Xiang Minzhi , Li Linyang , Gong Zuoping
Published: March 2020

The selection of adaptive region of geomagnetic map is an important factor that affects the positioning accuracy of geomagnetic navigation. An automatic recognition and classification method of adaptive region of geomagnetic background field based on Principal Component Analysis (PCA) and GA-BP neural network is proposed. Firstly, PCA is used to analyze the geomagnetic characteristic parameters, and the independent characteristic parameters containing principal components are selected. Then, the GA-BP neural network model is constructed, and the correspondence between the geomagnetic characteristic parameters and matching performance is established, so as to realize the recognition and classification of adaptive region. Finally, Simulation results show that the method is feasible and efficient, and the positioning accuracy of geomagnetic navigation is improved.
Digital mapping of soil information at a broad-scale: A review on GlobalSoilMap
Authors: Chen Songchao , Mulder Vera Leatitia , Poggio Laura , Roudier Pierre , Libohova Zamir , Minasny Budiman , Shi Zhou , Hannam Jacqueline , Arrouays Dominique
Published: March 2020

In the 21st century, soils are at the crossroads of global issues (i.e., food security, water security, biodiversity protection, climate change, and ecosystem services) and essential to achieve some of the Sustainable Development Goals. Although soils are central to these global issues, their management requires local actions and knowledge, which requires fine-resolution soil information. With an emphasis on broad-scale studies (>10,000 km2), this review outlines recent progress in the development of GlobalSoilMap, an initiative to provide a global fine-resolution grid of soil properties with quantified uncertainties using the bottom-up approach. This review provides an overview related to the soil data source, environmental covariates, spatial prediction, modelling and mapping techniques, uncertainty qualification, and target soil properties. The main findings of this review are: (1) A great increase of publication was observed after 2012, reaching a peak in recent years; (2) Australia and China were the most active countries; (3) Geoderma was the most frequent journal that was preferred by authors to publish related studies; (4) More than a half of the studies did not report soil sampling design; (5) Data splitting was the most frequent strategy for model evaluation, and independent validation was rarely used; (6) Nonlinear predictive model (i.e., machine learning) was becoming popular than ever before; (7) Relief, organisms and climate were the top three SCORPAN factors used in modelling; (8) Soil organic carbon (or soil organic matter) was the top soil property of interest.

This review also highlights the perspectives of GlobalSoilMap for further improving the quality of soil information globally and making it practical in decision making.
Influence of seasonally frozen ground on hydrological partitioning – a global systematic review
Authors: Ala-aho Pertti , Autio Anna , Bhattacharjee Joy , Isokangas Elina , Kujala Katharina , Marttila Hannu , Menberu Meseret , Meriö Leo-Juhani , Postila Heini , Rauhala Anssi , Ronkanen Anna-Kaisa , Rossi Pekka M. , Saari Markus , Torabi Haghighi Ali , Klöve Björn
Published: March 2020

Seasonally frozen ground (SFG) occurs on ~25% of the Northern Hemisphere’s land surface, and the influence of SFG on water, energy, and solute fluxes is important in cold climate regions.  The hydrological role of permafrost is now being actively researched, but the influence of SFG has been receiving less attention. Intuitively, water movement in frozen ground is blocked by ice forming in soil pores that were open to water flow prior to freezing. However, it has been shown that the hydrological influence of SFG is insignificant in some cases, with soil remaining permeable to water even when frozen. There is a clear knowledge gap concerning (1) how intensively and (2) under what physiographical and climate conditions SFG influences hydrological fluxes. We conducted a systematic literature review examining the hydrological importance of SFG we found reported in 143 publications. We found a clear hydrological influence of frozen ground in small-scale laboratory measurements, but a more ambiguous effect when the spatial scale under study increased to hillslopes, catchments, or watersheds. We also found that SFG may be hydrologically less important in forested areas or in regions with deep snow cover. Our systematic review suggests that hydrological influence of SFG may become more important in a future warmer climate with less snow and intensified land use in high-latitude areas.
Local microclimatic impacts of utility scale photovoltaic solar parks
Authors: Armstrong Alona , Hernandez Rebecca R , Blackburn George A , Davies Gemma , Hunt Merryn , Whyatt James D , Guoqing Li
Published: March 2020

Solar photovoltaic (PV) capacity has risen exponentially, with the majority deployed as ground-mounted solar parks, across the world. Deployments are projected to continue, leading to further land use change with implications for the hosting environment, including perturbations in ecological processes that underpin the supply of natural capital and ecosystem services. Whilst alterations to within solar park climate of magnitudes known to effect ecosystems processes have been quantified, the spatial extent remains unclear. In this study, we use remote sensing and field data to provide evidence of a solar park land surface temperature (LST) cool island. Specifically, we quantify a LST cooling of up to 2.3 ℃ outside the solar park boundary, with the effect declining rapidly with distance from the solar park but extending up to 730 m away. The magnitude of cooling observed is sufficient to alter ecosystem processes, including greenhouse gas emissions with implications for the carbon intensity of the electricity produced. Consequently, we need to better understand the local climatic impacts of solar parks and associated cascading impacts on ecosystem function to establish the broader environmental co-benefits and costs of this rapidly growing means of low carbon electricity production.
Typhoon and weathering processes on particles export to the ocean from a small river on the oceanic island of Taiwan
Authors: Chen Wei-rong , Hsieh IJy , Lien Kelly , Lin Saulwood
Published: March 2020

Huge quantity of terrigenous particles was exported from oceanic island small rivers in delivering to the ocean (Dadson et al., 2003; Milliman and Syvitsky, 1992).  Quantity of river particles entering the ocean could be related to river basin area, elevation, erosion rate, and seismic activity.  However, limited data are available regarding differences between physical and chemical weathering on erosion and their effects on particles export from oceanic type of small rivers nor data on extreme event, the typhoon, and its effect on weathering at this setting. Here we report and quantify particles as well as dissolved materials export from an oceanic small river, the Lanyang River at the northeastern Taiwan, during typhoon period and those under normal weather condition.  Our objectives are to quantify river particles and dissolved components export during normal and typhoon period; to understand factors controlling their variations; to compare efficiency of chemical and physical weathering under extreme weather condition and those at normal condition.  River particles and dissolved components were sampled monthly and during typhoons at every four hours frequency and filtered, weighted for particle concentrations as well as chemical analyses of particle and dissolved compositions in lab.  Chemical analyses include solid and dissolve silica, aluminum, iron, sodium, calcium, magnesium, and potassium as well as dissolved chloride, sulfate, and alkalinity. River discharge data were from Taiwan Water Resources Agency and precipitation data from Taiwan Central Weather Bureau.

 

Our results demonstrated that typhoon is the primary mechanism in driving concentration variations of both dissolved phases and solid components in the study river.  Huge amount of precipitation flushed into river during typhoon, resulting in rapid dilution of dissolved components as well as rapid increase of suspended particles concentration in reaching hyperpycnal level.  During the period of rapid increase of particles in the river, shift of types of particles as well as dissolve components were observed.  TDS (total dissolved solid) represent a small portion of the materials export to the ocean.  TSM (total suspended matter) flushed out of river during typhoon represent a major fraction (85%) of the annual total particles, however, the amount of particles for each typhoon varied significantly (from ~10 to ~45%). 
Plant hydraulics accentuates the effects of atmospheric moisture stress on transpiration
Authors: Konings Alexandra , Liu Yanlan , Kumar Mukesh , Feng Xue , Katul Gabriel
Published: March 2020

Transpiration directly links the water, energy and carbon cycles. It is commonly restricted by soil (through soil moisture) and atmospheric (through vapor pressure deficit, VPD) moisture stresses governed by the movement of water through plants, also known as plant hydraulics. These sources of moisture stress are likely to diverge under climate change, with globally enhanced VPD due to increased air temperatures but more variable and uncertain changes in soil moisture. In most Earth system and land surface models, the ET response to each of the two stresses is evaluated through independent empirical relations, while neglecting plant hydraulics. Comparison of these two models is challenged by the difficulty of ensuring any perceived differences are due to the model structure, not an imperfect parametrization. Here, we use a model-data fusion approach applied to long-term ET records collected at 40 sites across a diverse range of biomes to demonstrate that the widely used empirical approach underestimates ET sensitivity to VPD, but compensates by overestimating the sensitivity to soil moisture stress. The bias originates from the joint control of leaf water potential on plant response to soil moisture and VPD stress. To a lesser degree, it also overestimates from increased sensitivity to VPD under dry (low leaf water potential) conditions in the plant hydraulic model. As a result, a hydraulic model captures ET under high-VPD conditions for wide-ranging soil moisture states better than the empirical approach does. Our findings highlight the central role of plant hydraulics in regulating the increasing importance of atmospheric moisture stress on biosphere-atmosphere interactions under elevated temperatures.
Southern African hydroclimate during the Late Quaternary: integrating source to sink and multi-archive studies
Authors: Hahn Annette , Cawthra Hayley , Andrew Green , Marc Humphries , Enno Schefuß , Matthias Zabel
Published: March 2020

Southern Africa is located at the interface of sub-tropical and temperate climate zones as well as between two major warm and cold ocean current systems (Agulhas and Benguela), respectively. This makes it a key region for understanding global climate dynamics and highly sensitive to future climatic change. A growing number of paleo-archives have revealed small-scale climatic dipoles in this region and the driving mechanisms of the complex climatic variability often in this region remain unclear. Several regional studies have suggested a synchronicity with the southern hemisphere and thus inferred a direct insolation forcing while others have observed a synchronicity with northern hemispheric climate and associated this with a teleconnection mechanism. In order to decipher the complex climatic processes affecting this region it is necessary to integrate on- and offshore paleo-archives as well as various paleo-environmental indicators (proxies). For the correct interpretation of the various proxies a source to sink approach is necessary determining the origin of the different terrestrial sedimentary components and their potential alterations during transport and deposition. With a focus on marine and lacustrine sedimentary archives along the west, south, and east coast of southern Africa we are now able to reconstruct Late Quaternary climate variability on regional scales. We propose a new conceptual model describing latitudinal shifts of rainfall zones as tropical and temperate climate systems shift over glacial and interglacial cycles. New insights allow us to resolve some of the apparent contradictions between paleoclimate records from the region. 

 
The major factors of seismic-gravity modeling limits of applicability determination
Authors: Shirokova Tatiana , Lygin Ivan , Sokolova Tatiana
Published: March 2020

Currently, the integration of seismic and "non-seismic" geophysical research methods is increasingly demanded by the practice of exploration. Further improvement of the efficiency of the complex of seismometry and gravimetry, its wide introduction into practice, requires both the creation of recommendations on the methodology of joint interpretation of these methods, and the determination of limitations on the scale of surveying and the specifics of the considered cross-sections, affecting the effectiveness of the methods of the studied geological structures. The aim of the presented work is to identify the main factors that determine the limits of applicability of seismic-gravity modeling.

The possibilities of seismic-gravity modeling in conditions of different physical and geological structure of the considered environment, scale, level and quality of the initial data were investigated on real objects. It is shown that it is impossible to totally formalize a single approach (algorithmize) to the creation of a seismic-gravity model. The modeling technique inevitably changes, adapts to the physical and geological situation and the completeness and detail of a priori information. Against the background of numerous positive examples of use, the situations difficult for seismic-gravity modeling are given and analyzed carefully and the reasons for the low efficiency of the method are revealed.

The experience of practical research has shown that the effectiveness of seismic-gravity modeling is primarily influence by such features of geological structure as the extent of compartmentalization of the reflector horizons’ geometry, contrast and depth of the density boundaries, the accordance of seismic and gravity exploration (both field survey and target exploration intervals), the intricacy of the geological history of the region.

The findings are important at the design stage of field work to compile a set of geophysical methods, the most effective for this area of study.
Smallholder Irrigation and Pathways to Food Security
Authors: Burney Jennifer , Alaofè Halimatou , Naylor Rosamond , Taren Douglas
Published: March 2020

Irrigation can facilitate the expansion of agricultural production in multiple dimensions – including increasing crop yields, extending the production calendar to previously unmanageable dry periods, and facilitating production of a diverse array of higher-valued crops like fruits and vegetables. For poor smallholder farmers, this productivity boost is assumed to lead an array of benefits, including improved economic conditions and better food and nutrition security, but results from many irrigation studies in developing regions of the world have been underwhelming. Here we explore the simple and intuitive hypothesis that the benefits to farmers and their families of using irrigation depend on how increases in production are utilized, including whether crops are consumed in the home, monetized, or put to other uses. We use data from a solar irrigation project in Benin, West Africa, and show how the same irrigation technology resulted in a range of impacts on hundreds of beneficiaries. This variation is largely explained by how much individual families either consumed or sold products, and how those changes in consumption and sales then translated into a broad range of benefits. These findings have important implications for work at the food-energy-water nexus, including design and evaluation of irrigation-based projects targeted at smallholders. Importantly, they suggest that historical evaluations of irrigation impacts have likely missed important pathways, and have thus under-estimated the total benefits of irrigation to smallholders in contexts like the semi-arid tropics.
Vegetation Coverage change and its influencing factors in the Mu Us Sandy Land from 2000 to 2015
Authors: Gao Yan
Published: March 2020

Introducing and establishing sand-binding vegetation, as one of important approaches for combating desertification, has already applied in the ecological restoration and recovery in Mu Us sandy land for more than 60 years. Study on the dynamics of vegetation coverage in Mu Us Sandy Land and its influencing factors is thus a crucial requirement for guiding and establishing sand-binding vegetation. Based on MOD13A2 NDVI time-series data from 2000 to 2015，annual average temperature, annual precipitation, annual growth season precipitation, the land-use/land-cover (LULC) data, and topographic data, explored its dynamics during 2000–2015 and detected their influencing factors by the geo-detector method. The results showed that: (1) the vegetation coverage decrease from east to west in the Mu Us sandy land; (2) from 2000 to 2015，the vegetation coverage in the Mu Us sandy land has been increasing generally, the growth rate was 0.006 /a; (3) the number of pixels with significant increase in vegetation coverage accounted for 33.24% of the study area, meanwhile there was obvious spatial difference, the areas with significant or extremely significant increase of vegetation coverage were mainly distribute in eastern parts; (4) the main influencing factors of vegetation coverage change were annual precipitation, annual growth season precipitation, annual average temperature and LULC. Results indicate that, the influence of climate factors on Mu Us sandy land vegetation coverage was higher than LULC. It is necessary to put forward a suitable vegetation restoration plan under the projected climate change.
Challenging Intraplate Orogens: from geomorphology to lithospheric dynamic. The French Massif Central Case study
Authors: Malcles Oswald , Vernant Philippe , Ritz Jean-François , Fink David , Cazes Gaël , Fujioka Toshiyuki , Braucher Régis , Chéry Jean , Camps Pierre
Published: March 2020

In the 60’s, the formulation of the plate tectonic theory changed our understanding of the Earth dynamics. Aiming at explaining the earth first order kinematics, this primary theory of plate tectonic assumed rigid plates, a necessity to efficiently transfer stress from one boundary to another. 

If successful to explain, at first order, the plate-boundary evolutions, this theory fails when compared to the unpredicted but identified deformation located inside the plate-domains: the intraplate orogens. Indeed, the intraplate regions are thought to be slowly, if at all, deforming. Therefore, it is expected that intraplate regions do not show important finite deformation, that is to say, no mountains. Some intraplate regions, however, have important relief: the Snowy Mountains (Australia), the Ural Mountains (Russia) or the Massif Central (France) for examples. Traditionally, such regions are interpreted as old structures that are slowly eroded, interpretations that are most of the time weakly constrained. 

 

Our study is aiming at providing stronger constraints and then a better understanding of such challenging area that are the intraplate orogen domains. Because direct measurements of deformations (e.g. GNSS: Global Navigation Satellite System or InSAR: Interferometric Synthetic Aperture Radar) are most of the time below the precision level, it is necessary to derive this information from the landscape evolution. To do so, terrestrial cosmogenic nuclide (TCN) technics are a key method, allowing to constraint the temporal landscape evolution. Classically, two TCN-based approaches are used to quantify the landscape evolution rate: burial ages and watershed-wide denudation rates, based on measurement in quartz sediment of 10Be and 26Al concentrations, two radioactive cosmogenic isotopes.

 

Using the Massif Central (France) as study area, we show that this region is currently deforming.

From new geochronological constraints and a geomorphometric study, we propose that the region undergoes an active uplift encompassing the last c.a. 4 Ma. It can be explained by the combination of at least two phenomena: the first one is the uplift triggering event, that has yet to be clearly identified, and the second one: the erosional isostatic adjustment enhancing the first one and possibly continuing after the end of the first one. 
What's af(Fe)cting OC-Fe interactions? An experimental approach to understanding iron bound organic carbon in sediments.
Authors: Fisher Ben , März Christian , Faust Johan , Moore Oliver , Peacock Caroline
Published: March 2020

Drawdown of atmospheric CO2 over geologic timescales is largely controlled by imbalances in the carbonate-silicate cycles and the preservation of Organic Carbon (OC) in marine sediments. Up to 85% of this OC is buried in continental shelf sediments of which ~20% is associated with reactive iron (Fe) (hydr)oxides. Association with Fe (hydr)oxides may enhance OC preservation yet despite the importance of this, little is known about which Fe (hydr)oxide phase(s) is involved in OC uptake or the binding mechanism of OC to these reactive iron minerals.  

To estimate the importance of this OC-Fe association, a citrate-dithionite-bicarbonate (CDB) extraction method is commonly used to dissolve an operationally defined ‘easily reducible iron oxide’ fraction and release the associated OC from the sediment. However, natural samples often contain a range of Fe (hydr)oxide phases extractable by CDB, and the Fe phases extracted are defined entirely on the susceptibility of their pure forms to chemical reduction. This suggests that factors affecting mineral stability, including association with OC, could lead to incomplete or excessive phase extraction, which would affect estimates of OC bound to these Fe phases.

To address these issues, we simplified the geochemical system by synthesising OC-iron (hydr)oxide composites with known Fe (hydr)oxide phases and OC moieties with differing chemical structures, added them to OC-free sediment, and then applied the CDB extraction method to determine i) the precise Fe phases extracted; ii) the impact of OC moiety on Fe release and iii) the optimal experimental conditions for the extraction.

We show that reduction of our composites by CDB results in only partial dissolution of the most easily reduced Fe phase (ferrihydrite) and a recovery of only ~20% of total Fe. We also find that the recovery is likely controlled by the functional groups present in the OC and the handling/storage/preparation of samples prior to analysis. These factors could lead to misidentification of the mineral phases extracted and an underestimation of the amount of OC associated with Fe. A change in the estimates for OC associated with Fe would have widespread implications for our understanding of the role of OC-Fe interactions in global carbon cycling.
Unravelling the process controls of the spatial coherence of precipitation
Authors: Müller-Thomy Hannes , Breinl Korbinian , Lun David , Blöschl Günter
Published: March 2020

Precipitation is a key input variable for precipitation-runoff models. For catchments without precipitation observations generating rainfall fields is a possibility to enable precipitation-runoff simulations. These synthetic precipitation fields have to reproduce the spatial precipitation distribution adequately, especially at large catchment scales. Since the spatial precipitation coherence in ungauged catchments is unknown, it has to be transferred from an existing observational network. Ideally, the meteorological regime of the area of the observational network should be similar to that of the ungauged catchment in terms of the processes and factors controlling the spatial precipitation coherence.

This study identifies these processes and conceptualises them for rainfall modelling. We analyse precipitation time series of 1200 stations in the Greater Alpine Region (including Austria and Southern Germany, ~300,000 km²). Precipitation data subsets are constructed based on space-dependent (including climate zone, land use, altitude, slope, exposition) and time-dependent factors (seasons, circulation patterns, temperature). The analyses are carried out for different temporal resolutions (1, 12 and 24 hours) to unravel possible time-dependencies. The spatial precipitation coherence is represented by bivariate characteristics (Pearson’s correlation coefficient, continuity ratio, probability of occurrence) as a function of station separation distance. Uncertainty and variability of the spatial coherence are quantified via function spaces. Self-organizing maps are applied to translate the multi- dimensional results into low-dimensional maps.

In the low lands of the study domain, time-dependent factors are expected to influence the spatial precipitation coherence stronger than space-dependent factors, while in the mountainous regions the space-dependent factors will have a stronger influence due to the air movement being forced by the topography.
Environmental and climate dynamics in northeastern Siberia according to diatom oxygen isotopes
Authors: Kostrova Svetlana , Meyer Hanno , Pestryakova Luidmila , Biskaborn Boris , Fernandoy Francisco , Baumer Marlene
Published: March 2020

The sedimentary sequence from Lake Emanda (65°17′N; 135°45′E; 675 m a.s.l), one large freshwater body (33.1 km2) in the continuous permafrost of the Verkhoyansk Mountains, has been investigated within the German-Russian ‘Paleolimnological Transect’ (PLOT) project. It provided important insight into the environmental and climate dynamics in northeastern Siberia.

Well preserved diatoms occur only in the upper 125-cm interval of a 6.1-m sediment core (Co1412) covering the last ca. 13.4 cal. ka BP, and are mostly dominated by Cyclotella iris (up to 84%). The diatom succession is enriched by fragilarioid assemblages in the interval from ca. 11.0 to 13.0 cal. ka BP, while Aulacoseira ambigua is more frequent between 8.5 and 6.5 cal. ka BP. Diatoms were purified to > 98% SiO2 and < 0.8% Al2O3 suitable for oxygen isotope (δ18Odiatom) analysis. The δ18Odiatom values were corrected for contamination and range between +22.5‰ and +27.3‰. Maximum δ18Odiatom values (+26.7 to +27.3‰) are registered between 9.0 and 9.9 cal. ka BP and probably reflect a thermal maximum and/or very dry conditions in Early Holocene. The absolute minimum (+22.5‰) in the δ18Odiatom record is marked at 0.4 cal. ka BP and likely corresponds to the Little Ice Age. In general, a gradual depletion of 4.8‰ in δ18Odiatom is observed within the last 10 cal. ka, in line with an overall Holocene temperature decrease.

Our conclusions are based on a comprehensive investigation of both the modern hydrological system and diatom species analyses. The most recent δ18Odiatom = +24.2‰ combined with the present day lake water isotope composition (mean δ18Olake = −16.5‰), indicates a reasonable water−silica isotope fractionation (α = 1.0414) yielding a water temperature of 12 °C. The data demonstrate that the δ18Odiatom variability is associated with changes in the lake water isotopic composition rather than with lake temperature. The present water isotopic composition of Lake Emanda displays substantial evaporation effects, likely further influenced by air temperature and atmospheric circulation.