bluuebunny/crossref_metadata_2025 huggingface dataset:
Hyaloclastite formation during the effusion of the first lava flows of Siberian traps into a shallow freshwater basin
Authors: Polozov Alexander G. , Planke Sverre , Millett John A. , Zastrozhnov Dmitrii A. , Jerram Dougal A. , Svensen Henrik H.
Published: March 2020

Hyaloclastites have long been described within numerous volcaniclastic sequences in the Siberian Traps Large Igneous Province. They are typical for the southern and central parts of the Tunguska basin, and we inspected them in 2004-2010. In recent years, we have focused our attention on the northwestern region of the Tunguska basin (Norilsk area) with a volumetric manifestation of basaltic lava flows. We have completed fieldwork in this region from 2006 to 2019, with a recent focus on the understanding of the emplacement environments for the lowermost lava flow erupted directly on the end-Permian boggy surface. We studied pillow basalt at the basal part of the lowermost lava flow in the Norilsk region (Ivakinskaya Formation). In the upper part of this pillow basalt horizon, hyaloclastite is very common, and at the basal part, several tree trunks occur. The hyaloclastite includes black equant angular clasts and rusty red matrix and easily recognize at any outcrops. We studied hyaloclastite with optical microscopy and SEM-EDS. Black clasts composed of sideromelane cracked and altered to palagonite. Sideromelane fragments include crystals of olivine (Fo70), plagioclase (An63-70), and likely OPx altered to chlorite. Sideromelane glass has a basalt composition with elevated P2O5, CaO, and decreased amount of MgO and minor halogens (F, Cl). Some sideromelane clasts bear round inclusions (blobs) entirely infill with dolomite, siderite, and calcite. Every single carbonate inclusion has a specific structure and minerals infill.

We interpret these hyaloclastite rocks formations with carbonate inclusions as a result of lava flow effusion onto the shallow freshwater basin or boggy surface. Water and organic-rich sediments transferred with an explosion to steam and carbon dioxide gas, and this gas mixture was formed a hyaloclastite horizon at the basal part of a lava flow. We suppose that these sideromelane clasts with carbonate blobs are additional evidence of greenhouse gas generation during the early stage of the Siberian Traps lavas eruption.
Environmental and rock magnetic investigations into provenance and processes of west Iberian margin sediments
Authors: Nichols Matthew , Xuan Chuang , Hodell David A. , Richter Carl , Acton Gary D. , Wilson Paul A.
Published: March 2020

Ocean sediment records from the West Iberian margin can be correlated to both Antarctic and Greenland ice cores as well as to European terrestrial pollen data. Previous studies have focussed on comparatively short sediment cores collected from relatively deep-water sites (i.e. >~2500mbsl). Here we present magnetic mineralogy and grain size from Integrated Ocean Drilling Programme Sites U1385 (2585mbsl) and U1391 (1085mbsl) to further understand magnetic sediment provenance and palaeocurrent evolution on the west Iberian margin dating back to ~416 ka. The gradient of IRM acquisition curves, shape of hysteresis loops, and marked decrease in magnetic susceptibility at ~580°C indicate that magnetite is the dominant magnetic phase at Site U1391. At depth, increased contributions of a higher coercivity component are seen at intervals where the concentration of magnetic material is low. FORC diagrams indicate the presence of a narrow ridge elongated along the Bc axis consistent with a higher coercivity component observed in IRM acquisition data. Magnetic grain size proxy (kARM/k) records from Site U1391 also show a significant difference in pattern of variability at depth. After ~130 ka kARM/k closely follows relative sea level, however prior to ~130 ka there is higher frequency variability with apparent coarser magnetic grain size, suggesting the higher coercivity component could have resulted from diagenetic processes. This is particularly apparent during warm intervals where magnetic material concentration is low (MIS 7, 9 and 11). This behaviour differs from that observed at either Site U1385, or in the younger portion of the record at Site U1391. We infer that the intervals of diagenetically effected sediments at U1391 could have resulted from increased productivity, vertical migration of the Mediterranean outflow water and associated changes in bottom water ventilation. Further understanding of sediment composition, redox conditions, transport and provenance through the last few glacial cycles underpins much of the other palaeoclimatic investigation at these sites. Results from our analysis of rock magnetism will be used to guide the reconstruction of reliable relative palaeointensity records from the Iberian Margin sediments to assess past geomagnetic changes in the region.
Comparing simulated and manual snow profiles to derive thresholds for modeled snow instability metrics
Authors: Mayer Stephanie , van Herwijnen Alec , Bavay Mathias , Richter Bettina , Schweizer Jürg
Published: March 2020

Numerical snow cover models enable simulating present or future snow stratigraphy based on meteorological input data from automatic weather stations, numerical weather prediction or climate models. To assess avalanche danger for short-term forecasts or with respect to long-term trends induced by a warming climate, the modeled vertical layering of the snowpack has to be interpreted in terms of mechanical instability. In recent years, improvements in our understanding of dry-snow slab avalanche formation have led to the introduction of new metrics describing the fracture processes leading to avalanche release. Even though these instability metrics have been implemented into the detailed snow cover model SNOWPACK, validated threshold values that discriminate rather stable from rather unstable snow conditions are not readily available. To overcome this issue, we compared a comprehensive dataset of almost 600 manual snow profiles with simulations. The manual profiles were observed in the region of Davos over 17 different winters and include stability tests such as the Rutschblock test as well as observations of signs of instability. To simulate snow stratigraphy at the locations of the manual profiles, we obtained meteorological input data by interpolating measurements from a network of automatic weather stations. By matching simulated snow layers with the layers from traditional snow profiles, we established a method to detect potential weak layers in the simulated profiles and determine the degree of instability. To this end, thresholds for failure initiation (skier stability index) and crack propagation criteria (critical crack length) were calibrated using the observed stability test results and signs of instability incorporated in the manual observations. The resulting instability criteria are an important step towards exploiting numerical snow cover models for snow instability assessment.
Interactive exploration of fluvial futures
Authors: Straatsma Menno , Sutanudjaja Edwin , Schmitz Oliver
Published: March 2020

The World Economic Forum ranked extreme weather events, natural disasters, and failure of climate-change mitigation and adaptation in the top five risks in terms of likelihood as well as in terms of environmental and socioeconomic impact. Managing and adapting densely populated fluvial areas to the combined impacts therefore presents a major challenge for their sustainable development in this century. Common landscaping measures need to be evaluated to compensate for changes in discharge or sea level rise, for example, floodplain lowering, side channel recreation, embankment relocation, roughness lowering, groyne lowering, or removal of minor embankments. Decisions for adaptations require an overview of cost and benefits, and the number of stakeholders involved. For a rational and convincing decision-making process it is desired that stakeholders and planning professionals get easy access to source data, model code, intervention plans and their evaluation.

We used a set of open-source models and software packages to create an interactive tool enabling the exploration of possible futures of fluvial areas in a quantitative manner. The measures are planned and evaluated using RiverScape (Straatsma, 2019) and implemented in the spatio-temporal modelling environment PCRaster (http://www.pcraster.eu). For the seamless integration of explanatory text, user-defined parameterization of measures, executing RiverScape model code, and interactive visualization of spatial data we use Jupyter Notebooks (https://jupyter.org/). The notebooks provide an interactive working and teaching environment for integral river management, where professionals, stakeholders or scholars can explore different measures from different disciplinary backgrounds: flood hazard reduction, biodiversity, vegetation succession, and implementation costs. In our presentation we illustrate our integral river management workflow of creating own measures, evaluating them in isolation, and interpreting the results by example of the Waal River in the Netherlands.

References:

Straatsma, M. W., Fliervoet, J. M., Kabout, J. A. H., Baart, F., and Kleinhans, M. G.: Towards multi-objective optimization of large-scale fluvial landscaping measures, Nat. Hazards Earth Syst. Sci., 19, 1167–1187, https://doi.org/10.5194/nhess-19-1167-2019, 2019.
Robust Infrastructure Sequencing and Management for Growing Food Energy and Water Demands in the Zambezi River Basin
Authors: Zatarain Salazar Jazmin , Bertoni Federica , Giuliani Matteo , Castelletti Andrea
Published: March 2020

Fast population growth and economic development in several African countries is driving large infrastructure investments for growing energy, food and water demands which will likely strain existing ecosystem services.  To minimize negative impacts and guarantee long-term success and sustainability of these investments,  careful management and temporal planning of existing and new infrastructure is required. Our study focuses on the Zambezi River Basin (ZRB), a transboundary system supporting key economic growth and poverty reduction across its multiple riparian countries, while sustaining essential ecosystem services.  The ZRB currently encompasses five hydropower dams, with three additional dams planned. The goal of this study is to generate efficient pathways that allow the temporal sequencing of planned dam projects along with robust management strategies that balance food, energy and environmental demands. A participatory approach is adopted at an early stage by running a Negotiation Simulation Lab (NSL) to elicit stakeholders’ preferences and concerns supporting both model development and formulation of the optimization problem. Specifically, the pathway design is structured in three stages: first, optimal control policies are generated using Evolutionary Multi-objective Direct Policy Search for all possible combinations of dams projects; the time of construction is subsequently optimized, including the update of the system operation when a new dam is built, by balancing the benefits and the costs of additional infrastructure investments which are activated by projections of population growth triggering higher water and energy demands, finally promising policies are tested under a broad set of irrigation demand and streamflow scenarios. Our analysis shows that the rising demands cause all the planned dams to be built within the planning horizon from 2020-2060.  The study also indicates that the operational preferences are key since they dictate the system’s performance across multiple objectives and this behavior prevails under a larger suite of plausible future scenarios.  Overall, our study provides a novel approach that integrates infrastructure investment planning that can be coupled with cooperative operations to meet growing regional demands while involving stakeholders in crucial stages of the decision making process.

 
Evidence of long-term improvements in the quality and completeness of UK river flow data
Authors: Muchan Katie , Tindall Isabella , Dixon Harry , Turner Stephen , Sefton Catherine , Hannaford Jamie
Published: March 2020

Globally, access to hydrometric data of adequate record length, quality and geographical coverage to answer research questions and manage freshwater systems remains a major issue. The UK National River Flow Archive (NRFA) provides stewardship of river flow data from over 1,500 locations across the UK. Data are acquired and displayed as ‘provisional’ in real-time for 500 stations, however the NRFA also undertake a full update to the quality controlled dataset on an annual basis. Upon submission, river flow records are subject to both automated data screening and manual methods of quality control by a team of trained hydrologists to ensure the data disseminated by the Archive to its broad user community are of the highest quality and fit-for-purpose for a range of applications. In the 1990s, an increasing number of gaps in river flow records and emerging declines in data quality resulted in the introduction of a Service Level Agreement (SLA) in 2002 to protect the UK’s hydrometric network and resulting data. Here, we present the results from 15 years application of the SLA system through the use of a set of quantifiable indicators of data quality, completeness and provision. The improvements shown demonstrate the benefits of such a system to the overall utility of the nationally archived river flow data and an example of quality control and performance indicator systems that can be used as a best practice model for other monitoring networks around the world. They also demonstrate one method of helping to ensure hydrological databases provide information of high quality to meet pressing research and water management needs today and into the future.
Non-climatic factors affecting glacier mass balance (on the example of avalanche nourishment)
Authors: Turchaninova Alla , Sokratov Sergey , Seliverstov Yury , Petrakov Dmitry , Lazarev Anton , Bashkova Ekaterina
Published: March 2020

Glacier mass balance is affected by non-climatic factors such as topography, debris cover and geometric parameters of glaciers themselves, avalanche activity, volcanism, etc. The contribution of snow avalanches to the snow accumulation on a glacier is still among the least studied components of the glacier’s mass balance. We propose a possible approach for the numerical assessment of snow avalanche contribution to accumulation at mountain glaciers. The approach consists on the following steps: terrain analysis; weather data analysis; snow avalanche volume assessment during an analyzed balance year; numerical simulation of snow avalanches using RAMMS; evaluation of snow avalanche contribution to glacier accumulation. The proposed methodology was tested on three glaciers (Batysh Sook, № 354, Karabatkak) with an area up to 6,5 km2 in the Inner Tien Shan and Kolka glacier with an area 1,2 km2 in the Central Caucasus. To evaluate snow avalanche contribution to the winter accumulation, we reconstructed avalanche release zones that were most probably active during the analyzed balance year and corresponding snow fracture height in each zone. The numerical simulations of most probable released snow avalanches during the analyzed year using avalanche dynamics RAMMS software were performed and compared with the field observations and UAV orthophoto images. The outlines of avalanches deposits were realistically reproduced by RAMMS according to the results of field observations. The estimated contribution of snow avalanches to the accumulation on the studied glaciers during the analyzed balance year was as follows: Batysh Sook – 7,4±2,5%; № 354 – 2,2±0,7%; Karabatkak– 10,8±3,6% of the winter mass balance. In strong contradiction to the benchmark glaciers in the Tien Shan, the Kolka glacier demonstrates rapid mass gain in the Caucasus. It might be explained by significant, up to 80% share of avalanche nourishment to glacier mass gain. We note that avalanche-fed glaciers seem to be more stable at current stage of regional warming observed both in the Caucasus and the Tian Shan. The obtained results show the importance of the non-climatic factors for glacier surface mass balance control.
Source Investigation of the 2018 Lombok (Indonesia) Earthquake Sequences
Authors: Sianipar Dimas Salomo Januarianto , Huang Bor-Shouh , Ma Kuo-Fong , Setiadi Tio Azhar Prakoso , Hsieh Ming-Che , Haridhi Haekal Azief , Daryono Daryono
Published: March 2020

The western extension and deformation mechanism of Flores back-arc thrust in eastern Sunda-Banda Arc (Indonesia) are poorly investigated, and, thus, poorly constrained. From late July to August 2018, a sequence of large earthquakes (M6.4+) took place in the north of Lombok Island that marked the previously westernmost termination of the continuous zone of the back-arc thrusting. The 2018 Lombok earthquake sequences that began with Mw 6.4 (28 July 2018), and followed by Mw 6.9 (5 August 2018), and Mw 6.9 (19 August 2019) with massive subsequent aftershocks claimed on more than 500 casualties, nearly 500,000 people displaced and serious damages on Lombok Island. Here we relocate the aftershocks and perform the finite fault inversions of M6.4+ earthquake sequences constrained with teleseismic body and surface waves. Both refined hypocenters of aftershocks and rupture processes of large earthquakes provide detail kinematic descriptions of the source mechanisms of the sequences. The aftershocks distributions and slip model suggest that the earthquakes occurred on south-dipping low angle thrust faulting that striking to the east while it also activated aftershocks on surrounding complex shallow faulting with distinguishing distributions. The source inversions of large earthquakes over the entire of the western part of Flores back-arc thrust resulted as simple circular rupture propagations initiated from ~15 km depth for all events except the westernmost events (Mw 6.9 on 5 August 2019) that had a more complex rupture and initiated from shallower depth, and with slip distributed cross over the former identified westernmost termination of the Flores back-arc thrust. Our study suggests the further extension of back-arc thrusting and the possible structures revealed from the subsequence aftershocks. The source characterizations revealed in this study would be important for further seismic hazard analysis in this region.
Tools for fast analysis of InSAR based displacement maps
Authors: Monserrat Oriol , Barra Anna , Tomás Roberto , Navarro José , Solari Lorenzo , Herrera Gerardo , Crosetto Michele
Published: March 2020

The use of satellite interferometry (InSAR) is exponentially growing for the detection and monitoring of geohazard related movements. InSAR technique allows to process large areas and to extract high number of displacement measurements at low cost. By the way, the outputs consist of high volumes of information whose interpretation can be complex and time-consuming, mostly for users who are not familiar with radar data. Moreover, the use of InSAR have been moving from local to national, and now we are going towards a European application. In this scenario, the development of methodologies and tools to automatize the extraction of significant information and to facilitate the interpretation of the results, is more and more needed in order to increase their operational use. In this work we present a series of tools developed in the framework of the projects DEMOS (CGL2017- 83704-P), Momit (S2R-H2020/777630), Safety (ECHO/SUB/2015/718679) and U-Geohaz (UCPM-2017-PP-AG/783169). The so-called ADA (Active Displacement Areas) tools have been developed with the aim of ease the management, the use and the interpretation of wide areas results. Starting from the semi-automatic extraction of the most significant Active Displacement Areas (ADAFinder tool) we move to an automatic preliminary assessment of the phenomena that is behind the detected movement (ADAClassifier tool). All these tools go in the same direction of the European Ground Motion Service (EU-GMS) project, which will provide consistent, regular and reliable information regarding natural and anthropogenic ground motion phenomena all over Europe.
Disentangling the impact of global change on freshwater biodiversity decline
Authors: Kiesel Jens , Vu Tinh , Kakouei Karan , Sami Domisch , He Fengzhi , Guse Björn , Fohrer Nicola , Jähnig Sonja
Published: March 2020

Freshwater ecosystems have higher proportions of extinct and threatened species than terrestrial and marine ecosystems, with populations of vertebrates declined by 83% between 1970 and 2018. The pressing question is: what are the main drivers for this decline? Here we investigate the reasons for the loss of freshwater biodiversity using globally available gridded datasets at 0.5° spatial resolution on precipitation and temperature, land cover and land use, water use and dams as well as daily hydrological streamflow simulations from the ISIMIP initiative.

Across the past 50 years, we constructed annual change maps of the environmental variables along the global river networks and calculated time-variant indicators of hydrologic alteration (IHA) to depict hydrological change. We then calculated normalized indicators (e.g. proportion of threatened species) describing the current freshwater biodiversity status through species data aggregation of the International Union for Conservation of Nature's Red List of Threatened Species (IUCN Red List) categories.

By applying classification and regression trees (CART), we highlight the importance of environmental- and hydrological change on the freshwater biodiversity status based on IUCN Red List assessments on each grid cell globally. Our results reveal a large-scale spatial classification of the environmental variables and their potential impact on the ongoing freshwater biodiversity crisis.
Kinetic models of current sheets in the solar wind
Authors: Neukirch Thomas , Vasko Ivan , Artemyev Anton , Allanson Oliver
Published: March 2020

Current sheets in the collisionless solar wind usually have kinetic spatial scales. In-situ measurements (e.g. by Artemis) show that these current sheets are often approximately force-free, i.e. the directions of their current density and magnetic field are aligned, despite the fact that the plasma β is found to be of the order of one. The measurements also often show systematic asymmetric spatial variations of the plasma density and temperature across the current sheets, whilst the plasma pressure is approximately uniform. We present analytical equilibrium distribution functions of self-consistent force-free collisionless current sheets which allow for asymmetric plasma density and temperature gradients.
Different mechanisms of the pre- and co-eruptive tremor during the 2018 eruption at Sierra Negra volcano, Galapagos
Authors: Li Ka Lok , Rezaeifar Meysam , Bean Christopher J. , Grannell James , Bell Andrew , Ruiz Mario , Hernandez Stephen , Möllhoff Martin
Published: March 2020

Volcanic tremor are persistent seismic signals observed near active volcanoes. They are often associated with eruptions, although the exact relationships are not well constrained. To gain a better insight into the generation mechanisms of volcanic tremor, we study tremor that occurred during the 2018 eruption at Sierra Negra volcano, Galapagos. Located 1000 km west of continental Ecuador, Sierra Negra is a shield volcano with a large summit caldera and is one of the most active volcanoes in the Galapagos archipelago. The 2018 eruption started at about 19:55 UTC on 26th June and lasted about two months. Two tremor phases with very different frequency characteristics are identified before and after the eruption onset. The pre-eruptive phase is characterized by a narrow frequency band (2.5 – 4 Hz) and the co-eruptive phase has a broad frequency band (1 – 15 Hz). Location of the two phases by a seismic amplitude ratio method suggests that they are likely to be generated by different physical processes. The pre-eruptive phase is likely generated by dike opening while the co-eruptive phase is associated with lava flow. This interpretation is consistent with a time-lapse P-wave velocity structure of the volcano imaged by local-earthquake travel-time tomography.
Time-lapse CSAMT measurements to record the hydrological response of the Lodève landslide to heavy meteorological events
Authors: Lajaunie Myriam , Malet Jean-Philippe , Denchik Nataliya , Gautier Stéphanie , Delhaye Robert , Flores-Orozco Adrian , Sailhac Pascal
Published: March 2020

The Lodève landslide is a slow moving (3 to 4 mm/yr) and deep (60 m) rotational instability, located in the South-East of France, 60 km North from Montpellier (Hérault department). It is located in the Lodève basin, a set of connected steep head valleys marking the southern limit of the karstic Larzac plateau, and particularly prone to hydraulically triggered landslides. The unstable slope was progressively formed by the erosion of the upper limestone and sandstone units. The local tectonics build up resulted in a series of vertical North/South faults and fissures, allowing the water to infiltrate down to the deeper Triassic clay and evaporite layers. During heavy rainfall events, an amount of the meteoritic water infiltrates along these flow paths, down to the clay and evaporite layers from the Norian and Rhaetian era, leading to the rapid recharge of the units, the onset of high pressure in the confined layers and the decrease of the cohesion of the rock material and of the shear strength.

The Controlled Source Audio-frequency Magneto-Telluric (CSAMT) method is a low-impact, non-invasive active frequency domain electromagnetic sounding technique, deriving from the Magneto-Telluric (MT) method. An electromagnetic signal is produced a few km away from the studied site, and the electric and magnetic transfer functions of the plane wave signal are recorded at multiple frequencies, permitting the computation of far-field MT impedance tensor. CSAMT is characterized by a good vertical resolution and large depths of investigation, but poor sensitivity to the first tens of meters. For these reason, it is expected to be a good candidate method to conduct time-lapse studies in the context of pseudo-1D layered subsurface.

CSAMT data were acquired at the landslide from November 2018 to March 2019 at 8 different stations. The landslide is assumed to be a pseudo-1D medium with a tilted flat surface topography. The aim was to observe the variations of electrical resistivity related to the hydrogeological response to the heavy rains observed during the monitoring period. Sensitivity tests were realized with the software custEM. Measurements were taken at ten fundamental frequencies ranged from 510 to 9600 Hz with a Phoenix’s System-2000.net equipment and were repeated every months except in February.

The data quality is uneven from one station to another next. Most station showed significant variations in apparent resistivity. The observed variations were interpreted in a one-dimensional context, revealing lateral variations in the hydrogeological response of the slide. Complementary TDIP and DC data and high temporal geochemical and geophysical monitoring of properties at two boreholes were used to constraint the CSAMT interpretation.
Molecular signatures of kerogens and bitumens from the Lower Devonian Rhynie chert: Insights into the botanical affinity of the earliest land plants
Authors: Tewari Anuradha , Lepot Kevin , Dutta Suryendu , Cascales-Miñana Borja , Riboulleau Armelle
Published: March 2020

The Lower Devonian Rhynie chert of Scotland is an iconic geological formation that preserves the earliest known terrestrial ecosystem. This assemblage contains key evidence of earliest lineages of land plants, e.g., protracheophytes and paratracheophytes (former Rhyniaceae), together with animals, fungi, algae, and bacteria (Edwards et al., 2017). The exquisite preservation of this early biota provides an ideal scenario to explore the basal evolution of the land biosphere.

The Rhynie chert has been vastly studied from multiple viewpoints, however, the biomolecular composition, i.e., “molecular signature”, of the Rhynie flora, including the early detection of fossil lignin, remains clearly unresolved. Lignin biosynthesis has been considered as one of the crucial influences behind the survival and proliferation of land plants in terrestrial ecosystems. Here, we characterize the molecular fossils to help decipher the botanical affinities of the Rhynie flora.

Kerogens were isolated by the standard HF/HCl extraction procedure, and bitumens were extracted from the kerogens using organic solvents. The bitumens were studied with GC-MS, and the kerogens were analysed using Py-GC-MS and Py-GC×GC–TOFMS in the presence of TMAH reagent. The bitumens are characterized mainly by some aliphatic compounds such as a series of n-alkanes, pristane, phytane, and a series of diterpanes in very low abundance, as well as a set of aromatic compounds such as naphthalene and methylnaphthalenes, phenanthrene and methylphenanthrenes and retene. The pyrolysates, obtained using Py-GC-MS are dominated by benzene and methyl benzenes, phenol and methylphenols, Polycyclic Aromatic Hydrocarbons (PAHs) like naphthalene and methylnaphthalenes, phenanthrene and methylphenanthrenes, anthracene and methylanthracene, fluoranthene, pyrene, etc. Series of fatty acid methyl esters (FAME) and of n-alkane/alkene doublets were also detected. The thermochemolysates acquired from Py-GC×GC–TOFMS include the same compounds; additional methoxybenzene derivatives, methoxy toluene, methoxy benzaldehydes, and benzoic acid methyl esters, generated by reaction with TMAH, were also identified. Phenols and methoxybenzenes in the pyrolysates and thermochemolysates originate from lignin, and this is the first time that lignin monomers are formally identified from Rhynie chert samples.

References:

Edwards, D., Kenrick, P., Dolan, L., 2017. History and contemporary significance of the Rhynie cherts—our earliest preserved terrestrial ecosystem. Philosophical Transactions B Royal Society 373: 20160489.
Does soil disturbance result in soil carbon losses? – A case study on bioturbation effects of wild boar
Authors: Don Axel , Hagen Christina , Grüneberg Erik , Vos Cora
Published: March 2020

Soil disturbance and disruption is assumed to enhance mineralisation and cause losses of soil organic carbon. Therefore, no tillage is promoted as soil carbon sequestration measure. However, the experimental evidence of enhanced carbon turnover due to soil disturbance is rare.  We investigated soil disturbance in forest ecosystems with simulated bioturbation of wild boar. Wild boar are effective at mixing and grubbing in the soil and wild boar populations are increasing dramatically in many parts of the world. In a six-year field study, we investigated the effect of wild boar bioturbation on the stocks and stability of soil organic carbon in two forest areas at 23 plots. The organic layer and mineral soil down to 15 cm depth were sampled in the disturbed plots and adjacent undisturbed reference plots.

No significant changes in soil organic carbon stocks were detected in the bioturbation plots compared with non-disturbed reference plots. However, around 50% of forest floor carbon was transferred with bioturbation to mineral soil carbon and the stock of stabilised mineral-associated carbon increased by 28%. Thus, a large proportion of the labile carbon in the forest floor was transformed into more stable carbon. Carbon saturation of mineral surfaces was not detected, but carbon loading per unit mineral surface increased by on average 66% due to bioturbation. This indicates that mineral forest soils have non-used capacity to stabilise and store more carbon.

Our results indicate that soil disturbance and bioturbation alone does not affect soil carbon turnover and stocks, but only change the distribution of carbon in the soil profile. This is in line with results from no-tillage experiments. The prevailing effect is a redistribution of carbon in the soil profile with no changes in total soil carbon stocks. We discuss these findings in the light of soils as potential sinks for carbon.

 
‘Water’ content as a tool to estimate rheological differences in the lithosphere of young extensional basins
Authors: Liptai Nóra , Lange Thomas P. , Patkó Levente , Berkesi Márta , Szabó Csaba , Kovács István J.
Published: March 2020

Nominally anhydrous minerals in the lithospheric mantle, such as olivine and pyroxenes can host a small amount (tens to hundreds of ppm) of structurally bound hydroxyl (‘water’). Numerous studies pointed out that water has a strong effect on the rheological properties of the lithospheric mantle, such as melting temperature, electrical conductivity, viscosity and seismic wave propagation speed. Water content of mantle xenoliths can thus be used to estimate such rheological properties which can then be compared with geophysical observations.

In this study we present effective viscosities and electrical resistivities calculated with the use of ‘water’ contents of upper mantle xenoliths from the Carpathian-Pannonian region (CPR). The CPR is a young extensional basin in Central Europe, where intraplate alkali basalts sampled the lithosphere in five areas, including locations from both the central and marginal regions. ‘Water’ contents are generally higher in xenoliths from the marginal areas compared with those from the central areas of the CPR, due to significant hydrogen loss during the extension in the Miocene (Patkó et al., 2019). It is demonstrated that due to the different ‘water’ contents, the lithospheric mantle in the central areas can be characterized with higher effective viscosity and electrical resistivity, and thus can be considered as more rigid than the marginal areas. This relative rigidity induced by lithospheric thinning may be a general feature of extensional basin systems worldwide, and can be regarded as a ‘self-healing’ mechanism of the extending lithosphere.

 

References:

Patkó, L., Liptai, N., Kovács, I. J., Aradi, L. E., Xia, Q.-K., Ingrin, J., Mihály, J., O’Reilly, S. Y., Griffin, W. L., Wesztergom, V., Szabó, C., 2019. Extremely low structural hydroxyl contents in upper mantle xenoliths from the Nógrád-Gömör Volcanic Field (northern Pannonian Basin): Geodynamic implications and the role of post-eruptive re-equilibration. Chemical Geology, 507, 23-41.
Magnesium, calcium, strontium and radiocarbon in the shell of the brachiopod Pajaudina atlantica: implications for growth, biomineralisation and palaeo-proxy application
Authors: Liebetrau Volker , Jurikova Hana , Gutjahr Marcus , Henkel Daniela , Hiebenthal Claas , Krause Stefan , Eisenhauer Anton
Published: March 2020

Brachiopods present a key taxon for Phanerozoic palaeo-climatic and palaeo-environmental reconstructions, owing to their good preservation and abundance in the geological record. Yet to date, only little is known on the mechanisms that control the incorporation of some key elements into their calcitic shells, as well as the mechanisms behind the biomineral formation itself, especially in thecideid brachiopods. To evaluate the distribution and controls on Mg, Ca, and Sr we examined the composition of natural Pajaudina atlantica Logan, 1988 (Thecideidae, Brachiopoda) originating from Canary Islands, Spain as well as specimens cultured experimentally under various pH-pCO2 and temperature conditions [1]. At a high-spatial resolution, electron microprobe analyses (EMP) revealed substantial intrashell and intraspecific Mg and Ca heterogeneities that seemed to be principally linked to growth features and different microstructures rather than changes in temperature. Strontium, on the other hand, appeared uniform across the shell and related to the culture medium or seawater Sr content. After almost two years of culturing, however, the new shell production was only minimal and cryptic, and difficult to evaluate by visual inspections. By combining culture-specific geochemical fingerprints with radiocarbon dating of natural samples, we estimated the growth rates to be on the order of several tens to few hundreds of µm per year, which may potentially suggest a large life span and slow growth of this species, and if true, would certainly make them a highly interesting archive for inferring past ocean variabilities.

[1] Jurikova H., et al. (2019) Geochim. Cosmochim. Acta 248, 370–386.
Visual approach to clustering large-scale meteorological datasets
Authors: Barnes Andrew , Kjeldsen Thomas , McCullen Nick
Published: March 2020

Identifying the atmospheric processes which lead to extreme events requires careful generalisation of the meteorological conditions surrounding such events such as sea-level pressure and air temperature. Through the case study of clustering the processes behind extreme rainfall events (annual maximum 1-day rainfall totals) in Great Britain, this presentation shows how visualising the iterative processes used by clustering algorithms can aid in algorithm selection and optimisation. Here two big data datasets, namely the CEH-GEAR (gridded observed rainfall) and NCEP/NCAR Reanalysis datasets are synthesised and clustered using different methods such as k-means, linkage methods and self-organising maps. The performances of these methods are compared and contrasted through analysis of the clusters created at each iteration, highlighting the importance of algorithm selection and understanding. The key findings of this clustering process result in three large-scale meteorological condition types which lead to extreme rainfall in Great Britain as well as a novel approach to comparing clustering mechanisms when using meteorological data.
Crystallisation of REE carbonates from aqueous solutions
Authors: Price Dylan , Butler Ian , Ngwenya Bryne , Kirstein Linda
Published: March 2020

Low temperature aqueous synthesis of Rare Earth Element (REE) carbonates show extensive variability in the resulting minerals. Precipitated mineral phases and crystallisation rates vary depending, in part, on the REE used. Indeed, much of the work to date on REE aqueous geochemistry focuses on the individual behaviour of discrete REEs. 

We present a low temperature aqueous geochemical investigation of REE carbonate crystallisation pathways, which takes into consideration the influence of multiple REEs in solution. This serves to mimic more realistic conditions that are found in natural geological settings propitious to REE mineralisation. Our experiments focus on the behaviour of La, Ce, Nd, Dy carbonates at 30oC.

Concordant with previous studies, our results suggest that the crystallisation process of REE carbonates begins with the formation of an amorphous phase that transitions into a crystalline phase after a lag time that depends on the element and the proportions in the mixture. 

This lag time is REE specific and is shorter for lighter REE compared to their heavier counterparts. In particular, the presence of another REE in the system affects the crystallisation timings and the morphology of the resulting crystals. For example, samples of mixed La/Nd carbonates begin their phase transition at lag times in between that of the two end-members (i.e. La and Nd) carbonate compositions. Furthermore, we find that the resulting growth rates and crystal habits are unique to the ratio of the REE mixture, with the underlying ionic potential of the mixture linked to the growth rates. In addition, observations throughout the crystallisation process also show that growth begins with flocculation of nanoparticles followed by crystal growth via Ostwald ripening.

REEs are sought after due to their unique properties and are integral to modern technologies such as lasers, catalytic converters, batteries, electro-magnets and wind turbines. Considering how the crystallisation behaviour with REE mixtures differs from that of discrete REE in solution, this work gives insights into the fundamental chemistry of REEs in aqueous solutions - relevant for studies of REE mineralisation and materials processing. 
A methodology for the bivariate hydrological characterisation of the overtopping failure for river levees
Authors: Isola Matteo , Caporali Enrica , Garrote Luis
Published: March 2020

This research presents a methodology for the hydrological characterisation of the overtopping failure for an existing river levee. Conventional procedures usually consider only one variable for the hydrologic forcing, e.g. peak discharge Q. Such an approach might fail if also the volume of the hydrograph V is a significant factor.  The proposed procedure is based on the generation of a set of plausible hydrographs. Each hydrograph has a couple of Q and V resulting from an approximated bivariate distribution. The shapes of the hydrographs are classified according to their tendency to produce overtopping, introducing the new Overtopping Hydrograph Shape Index (OHSI). The levee of a river reach located in Tuscany Region, Italy, was tested. As a preliminary result, it was found that the hydrographs that produce overtopping failure lay in a zone in the Q-V space, delimited by the Critical Overtopping Flood Hydrograph (COFH) curve. The existence of the COFH demonstrates that overtopping failure is not determined by a unique variable Q but rather by the combination of both Q and V. The limiting case corresponds to a family of hydrographs with varying Q and V values. The COFH allows dividing the Q-V space into two zones: the no-failure zone and the failure zone, which simplify the evaluation of the failure probability for a river levee.  This procedure is based on tools that are widely known and it is replicable by the public administrations or public entities that are interesting in the hydrologic and hydraulic risk assessment.
Impact of the North Atlantic Warming Hole on Sensible Weather
Authors: Gervais Melissa , Shaman Jeffrey , Kushnir Yochanan
Published: March 2020

In future climate projections there is a notable lack of warming in the North Atlantic subpolar gyre, known as the North Atlantic warming hole (NAWH). The NAWH has been previously shown to contribute to a poleward shift and eastward elongation of the North Atlantic jet that constitutes an additional important driver of future changes in the North Atlantic jet using a set of large-ensemble atmosphere simulations with the Community Earth System model.  The current study investigates the impact of the warming hole on sensible weather, particularly over Europe using the same simulations. North Atlantic jet regimes are classified within the model simulations by applying self-organizing maps to winter daily wind speeds on the dynamic tropopause. The NAWH is found to increase the prevalence of jet regimes with stronger and more poleward jets.  A previously identified transient eddy-mean response to the NAWH that leads to downstream enhancements of wind speeds is found to be dependent on the jet regimes. These localized regime-specific changes vary by latitude and strength, combining to form the broad increase in seasonal mean wind speeds over Eurasia. Impacts on surface temperature and precipitation within the various North Atlantic jet regimes are also investigated. A large decrease in surface temperature over Eurasia is found to be associated with the NAWH in regimes where air masses are advected over the subpolar gyre.  Precipitation is found to be locally suppressed over the warming hole region and increased directly downstream. The impact of this downstream response on coastal European precipitation is dependent on the strength of the NAWH.
Phytoplankton communities influence the dissolved organic matter composition of the sea-surface microlayer
Authors: Oeljeschlaeger Lea , Hintz Nils , Niggemann Jutta , Wurl Oliver , Dittmar Thorsten
Published: March 2020

The sea surface microlayer (SML) is the boundary layer at the ocean and atmosphere interface and plays a crucial role in air-sea gas exchange processes and global climate. It is enriched in dissolved organic matter (DOM) compared to the underlying water, but the chemical composition of this material has been insufficiently studied. For improved understanding of the exchange processes it is of utmost importance knowing the molecular composition of the SML. Studying the microlayer is very challenging due to its thinness and strong influence of external forces as wind, UV light and atmospheric deposition on the chemical and microbial composition. The complex and dynamic nature of the microlayer and the enrichment of hydrophobic substances led to the assumption that we find unique chemical composition and distinct compound groups. SML samples of the Indo-Pacific Ocean from R/V Falkor cruise FK161010 (October 2016) were studied with respect to molecular composition of DOM. We analyzed solid-phase extracted DOM with high resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). The results were compared to the underlying water (ULW, 1m depth). We found similar molecular DOM composition in the ULW, whereas microlayer extracts were more variable and diverse. This can be related to the influence of changing weather conditions during the cruise on the SML. To reveal molecular changes without interfering external forces, a 5-week indoor mesocosm experiment with induced marine phytoplankton blooms was conducted. A modified solid-phase extraction approach was used to chemically fractionate the microlayer DOM prior to molecular analysis. Our experiment showed that the DOM enrichment in the SML is linked to different phytoplankton communities. In addition, it revealed that depending on the predominant community the DOM concentration can be even depleted in the SML compared to the ULW. Based on the outcome of our field and laboratory studies we conclude that molecular level analysis of surface microlayers is essential to understand the chemical diversity of this highly dynamic boundary layer.
Self-aggregation conceptualized by cold pool organization
Authors: Nissen Silas Boye , Haerter Jan O.
Published: March 2020

In radiative-convective equilibrium (RCE) simulations, self-aggregation is the spontaneous emergence of one or several long-lasting convective clusters from an apparently homogenous atmosphere (Wing, 2019). This phenomenon may implicate the formation of tropical cyclones (Wing et al., 2016; Muller et al., 2018) and large-scale events such as the Madden-Julian Oscillation (Arnold et al., 2015; Satoh et al., 2016; Khairoutdinov et al., 2018). However, it remains poorly understood how cold pools (CPs) contribute to self-aggregation. Using a suite of cloud-resolving numerical simulations, we link the life-cycle and the spatial organization of CPs to the evolution of self-aggregation. By tracking CPs, we determine the maximal CP radius Rmax ≈ 20 km and show that cloud-free regions exceeding such radii always grow indefinitely. Besides, we identify a minimum CP radius Rmin ≈ 8 km below which CPs are too cold, hence negatively buoyant, to initialize new convective cells. Finally, we suggest a simple mathematical framework that describes a mechanism, where cloud-free areas are likely to form when CPs have small Rmax, whereas large Rmax hampers cavity formation. Our findings imply that interactions between CPs crucially control the dynamics of self-aggregation, and known feedbacks may only be required in stabilizing the final, fully-aggregated state.