bluuebunny/crossref_metadata_2025 huggingface dataset:
Monitoring offshore CO2 storage projects, aligning capabilities with regulations and public expectations.
Authors: Alendal Guttorm , Blackford Jerry , Carpentier Stefan , Cremer Holger , Dankel Dorothy J. , Dewar Marius , Fagerås Bjarte , Gasda Sarah E. , Gundersen Kristian , Heffron Raphael , Lien Martha , Oleynik Anna , Omar Abdirahman , Pawar Rajesh , Romanak Katherine , Snee Darren , Schütz Sigrid E. , Torabi Parisa
Published: March 2020

We will report on preliminary results and present plans for the continuation of an international project, ACTOM. The overall objective of ACTOM is to develop internationally applicable capabilities to design and execute adequate, rigorous and cost-effective monitoring of offshore carbon storage projects, aligning industrial, societal and regulative expectations with technological capabilities and limitations.

At the core of the project is a web based pre-operational tool-kit that will deliver new abilities to design a site specific marine monitoring program that will ultimately:

enable regulators to quantifiably assess that a proposed monitoring strategy delivers an acceptable standard of assurance,

enable operators to properly plan, cost and adapt monitoring strategies to site specific circumstances,

enable regulators and operators to communicate to the effectiveness of proposed monitoring strategies to enable informed societal consensus in view of marine spatial planning.

Responsible Research and Innovation (RRI) is an approach to anticipate and assess implications and expectations of new technologies on the society, a framework increasingly being used in marine environmental studies and in biotechnology and innovation. We use this framework on Carbon Capture Usage and Storage (CCUS), considering the technology in view of the UN Sustainable Development Goals. In an extension of this, potential legal conflicts between storage projects or other uses of the seas, will be addressed in view of marine spatial planning. 

By viewing CCUS and offshore storage in view of Sustainable Development Goals (SDG) and in the RRI framework, the aim is to ease communicating the benefits of the technology while addressing the uncertainties and risks in a coherent way.

This work is part of the project ACTOM, funded through the ACT programme (Accelerating CCS Technologies, Horizon2020 Project No 294766). Financial contributions made from; The Research Council of Norway, (RCN), Norway, Netherlands Enterprise Agency (RVO), Netherlands, Department for Business, Energy & Industrial Strategy (BEIS) together with extra funding from NERC and EPSRC research councils, United Kingdom, US-Department of Energy (US-DOE), USA. In-kind contributions from the University of Bergen are gratefully acknowledged.
Changes in soil carbon stocks and distribution under perennial and annual bioenergy crops
Authors: Ferchaud Fabien , Mary Bruno , Rupngam Thidarat , Chenu Claire
Published: March 2020

Bioenergy crops are expected to provide biomass to replace fossil resources and reduce greenhouse gas emissions. In this context, their effect on soil carbon sequestration is of primary importance. There is a wide range of candidate crops including perennial C4 crops or annual crops but their impact on soil organic carbon (SOC) stocks remain very uncertain as shown by the wild variability in published experimental results.

In this study, we measured the changes in SOC stocks under perennial (miscanthus and switchgrass), semi-perennial (fescue and alfalfa) and annual (triticale and sorghum or maize) bioenergy crops managed with two N fertilisation rates. The experiment called “Biomass & Environment” is located in northern France on a deep loamy soil (Haplic Luvisol) and was set up in 2006. The soil was sampled at the start of the experiment, in 2011-2012 and again in 2018 (0-60 cm, 5 layers). SOC stocks were calculated at equivalent soil mass and δ13C was systematically measured and used to calculate changes in new and old SOC stocks. In 2018, the SOC distribution in different soil particle-size fractions was also characterized for some treatments.

After 12 years, there was a large increase in SOC concentration (+7.6 g kg-1 on average) under perennial crops in the surface layer (≈ 0-5 cm) but a slight decrease in deeper layers. Changes in δ13C also showed that more than half of the new SOC accumulated in the surface layer. In addition, the additional SOC storage in the first layer was found in coarse organic fractions (50-200 and 200-2000 μm) but also in the more stabilised 0-50 μm fraction. SOC concentration under semi-perennial crops increased in the two first layers (≈ 0-20 cm), from 10.2 g kg-1 in 2006 to 11.6 g kg-1 in 2018 on average and slightly decreased below. Under annual crops, a decrease in SOC concentration was observed in all layers and particularly in the third layer (≈ 20-33 cm). There was no significant effect of the N fertilisation. Over the old ploughed layer (≈ 0-33 cm), SOC stocks increased between 2006 and 2018 under perennial and semi-perennial bioenergy crops (by 3 and 2 t C ha-1 on average respectively) and decreased by 7 t C ha-1 on average under annual crops.

This study show that different bioenergy crops can have contrasted impacts on SOC stocks but also on SOC distribution in the soil profile.
Coda-wave interferometry and the Marchenko method
Authors: Wapenaar Kees , van IJsseldijk Johno
Published: March 2020

Coda-wave interferometry, introduced by Snieder and co-workers, employs the relative high sensitivity of the scattering coda in an acoustic or seismic response to time-lapse changes of the propagation velocity and/or structure. It has been successfully applied at many scales, ranging from inferring temperature changes in granite samples, via structural health monitoring of bridges, to monitoring the minute changes in the interior of a volcano prior to eruption. Whereas in most situations the velocity changes are assumed to take place in a large region, it has been shown that coda-wave interferometry can also be used to image a local perturbation of the propagation velocity or structure. The latter approach assumes diffuse waves and employs an array of receivers that surrounds the perturbation.

We investigate the application of coda-wave interferometry for monitoring of fluid-flow processes in aquifers, geothermal reservoirs, CO2-storage reservoirs and hydrocarbon reservoirs. In these applications the velocity perturbation is local, but the medium is probed with deterministic seismic body waves from the surface only. The location of the velocity perturbation is usually reasonably well known, but it is practically impossible to identify events in the coda that are directly related to the local perturbation. Recently we introduced the Marchenko method, which retrieves information about multiple scattering from reflection data at the surface in a data-driven way. Here we propose to use the Marchenko method to remove the response from the areas above and below the local velocity perturbation. In this way we isolate the scattering coda of the local velocity perturbation, which enables the application of coda-wave interferometry to monitor the fluid-flow process.
Investigating the dynamics of Lake Kivu with quantum technology
Authors: Schmidt Maximilian , Wachs David , Arck Yannis , Bärenbold Fabian , Ringena Lisa , Robertz Julian , Kersting Arne , Schmid Martin , Oberthaler Markus K. , Aeschbach Werner
Published: March 2020

Lake Kivu, located on the border of Rwanda and the Democratic Republic of Congo, is a very peculiar lake in several aspects. The meromictic lake shows a vertical stratification dominated by high salt concentrations of up to 6 ‰ resulting in a very thick monimolimnion of 420 m (max depth ~492 m). This extremely large non mixing part of the lake functions as a reservoir for very high concentrations of volcanogenic gases like methane and carbon dioxide (up to 20 and 100 mmol/l respectively) resulting in a growing hazard for millions of local residents. Our aim of this study is to get insights into the hydrological dynamics, solute transport and the lakes mixing behavior utilizing radiometric dating with 39Ar.

The noble gas isotope 39Ar (t1/2 = 269 a) covers a unique time span for studying the dynamics of aquatic and glacial systems of the last millennium. Although this tracer has been acknowledged for decades, studies so far are limited by its low abundance, little radioactivity and hence huge required sample sizes (~1000 L water). Until today environmental routine measurements are mainly confined to groundwater reservoirs, where nearly unlimited sampling is possible. The application of techniques from atomic physics using a magneto optical atom trap (MOT) solves the problem by reducing sample volume requirements by several orders of magnitude. The problem of the very low isotopic abundance of 10-16 is resolved by resonant multi-photon scattering of 39Ar in the MOT. This technique named Argon Trap Trace Analysis with its very low minimal sample size of 0.5 cm³STP pure argon enables easy sample handling in the field as well as common sampling procedures like Niskin bottles for aquatic systems, drill core sampling for glacial systems or as in the case of Lake Kivu spray chamber gas sampling in remote places. It is thus a door opener for new geophysical research fields that were excluded from radio-argon dating so far.

Here we present our most recent results of sampling campaigns in 2018 and 2019 using samples of about 25 – 40 L gas-water mixtures corresponding to 0.5 – 10 cm³STP pure argon showing surprisingly high ages for the lake water.
Slow subduction initiation forces fast ophiolite formation
Authors: Soret Mathieu , Bonnet Guillaume , Agard Philippe , Larson Kyle , Cottle John , Dubacq Benoit , Button Mark
Published: March 2020

Metamorphic soles are m to ~500 m thick tectonic slices welded beneath most large- scale ophiolites (usually ~20 km thick). They typically show a steep inverted metamorphic structure where the pressure and temperature (T) conditions of crystallization increase upward, from the base of the sole (500 ± 100°C at 0.5 ± 0.2 GPa) to the contact with the overlying peridotite (800 ± 100°C at 1.0 ± 0.2 GPa). The inverted  T gradient was historically interpreted as a result of heat transfer from the incipient mantle wedge toward the nascent slab synchronously with the overlying ophiolite formation (within only 1-2 Myrs). Their mineralogical assemblage and deformation pattern provide major constraints on the nature and the timing of the processes controlling the dynamics of the plate interface during early subduction.

Soret et al. (2017, 2019) recently reappraised the tectonic–petrological model for the formation of metamorphic soles below ophiolites, showing that the present-day structure of the sole results from the successive stacking of several homogeneous oceanic crustal slivers (without internal T gradient). This stacking marks the evolution of rheological properties of slab material and peridotites of the upper plate as the plate interface progressively cools (Agard et al., 2016). These findings outline the thermal and mechanical complexity of early subduction dynamics, and highlight the need for refined numerical modelling studies.

Lu-Hf geochronology on garnet from the Oman metamorphic sole has recently shown that the earliest accreted subunit, found directly against the upper plate mantle, was initially buried ≥ 8 Ma earlier than previously estimated (Guilmette et al., 2017). These results imply initiation ≥ 8 Ma before the formation of the ophiolite, which underscores the common belief that ophiolite-sole couples record spontaneous subduction initiation and rather indicates far-field forcing long before upper plate extension and mantle upwelling.

We herein present new U-Pb titanite and monazite petrochronology across the different sub-units of the Oman metamorphic sole. Our results confirm the time lag of several million years between subduction initiation and the ophiolite formation, therefore supporting the recently proposed model of far-field forced subduction initiation. They also reveal a significant time lag between the underplating and exhumation of each sub-unit of the sole.
On the horizontal currents over the Martian magnetic cusp
Authors: Majeed Tariq , Al Mutawa Shahad , Al Aryani Omar , Bougher Stephan , Haider Syed
Published: March 2020

Localized crustal magnetization over heavily cratered southern hemisphere at Mars gives rise to open magnetic field configurations which interact with the solar wind magnetic field to form magnetic cusps.  The downward acceleration of energetic electrons in these cusps can produce aurora and an extended topside ionospheric structure over regions of magnetic anomalies.  We report plasma collisions with the neutral atmosphere at one of the Martian cusps located at 82oS and 108oE, where the crustal field is strong with a radial component ~30o from the local zenith.  We find that the dynamo region in the upper ionosphere of Mars is located between altitudes of 102 km and 210 km. The electrons in this region are constrained to gyrate along magnetic field lines while ions are dragged by neutrals and move along the direction of applied force.  In the absence of the electric field, the horizontal current in the Martian dynamo is generated by the differential motion of ions and electrons.  We find that the bulk of the current density is equatorward and confined within the Martian dynamo near the ionospheric peak with a magnitude of ~3.5 µA/m2.  We also find that the westward current density of magnitude ~0.4 µA/m2 peaking near the upper boundary of the Martian dynamo is generated by magnetized ions in the -F x B direction.  The model details and results in comparison with other studies will be presented.       
Alkane autoxidation and aerosol formation: new insights from combustion engines to the atmosphere
Authors: Ehn Mikael , Wang Zhandong , Rissanen Matti , Garmash Olga , Quéléver Lauriane , Monge-Palacios Manuel , Rantala Pekka , Donahue Neil , Berndt Torsten , Sarathy Mani
Published: March 2020

Autoxidation is a process whereby organic compounds become oxidized by molecular oxygen (O2). It is ubiquitous in various reaction systems, contributing to the spoilage of food and wine, ignition in internal combustion engines, and formation of atmospheric secondary organic aerosol (SOA) from volatile emissions. Autoxidation thus greatly influences both engine operation and efficiency, and, via SOA, climate and air quality. Recent progress in atmospheric chemistry has identified double bonds and oxygen-containing moieties as structural facilitators for efficient autoxidation, and subsequent OA formation. Lacking either of these functionalities, alkanes, the primary molecular class in fuels for combustion engines and an important class of urban trace gases, have been expected to have low susceptibility to undergo autoxidation. In this work, we show that alkanes can indeed undergo efficient autoxidation both under combustion-relevant and atmospheric temperatures, consequently producing more highly oxygenated species than previously expected. By bridging methodologies and knowledge from both combustion and atmospheric chemistry, we mapped the autoxidation potential of a range of alkane structures under various conditions, from the combustion domain to the atmospheric domain. We identified the importance of isomerization steps driven by both peroxy and alkoxy radicals, and show that isomerization and production of low-volatile condensable vapors is efficient even under highly polluted ([NO]>10ppb) conditions. Our findings, currently under review, provide insights into the underlying chemical mechanisms causing highly variable SOA yields from alkanes, which were observed in previous atmospheric studies. The results of this inter-disciplinary effort provide crucial new information on oxidation processes in both combustion engines and the atmosphere, with direct implications for engine efficiency and urban air quality.
First results of a comparison study of multi-domain REMO CORDEX simulations between 0.11° and 0.22° resolution with ERA-Interim forcing
Authors: Schubert-Frisius Martina , Pfeifer Susanne , Reca Remedio Armelle , Teichmann Claas , Buntemeyer Lars , Sieck Kevin , Weber Torsten , Rechid Diana , Jacob Daniela
Published: March 2020

Within the framework of WCRP CORDEX, the CORE (CORDEX Coordinated Output for Regional Evaluations) experiment provides a homogeneous ensemble of regional climate projections for 9 domains covering all land areas of the globe with the exception of the Arctic and Antarctic regions (http://www.cordex.org/experiment-guidelines/cordex-core/). CORDEX-CORE provides data from two regional climate models (REMO2015 and RegCM), driven by 3 GCMs and under 2 RCP scenario conditions at a resolution of about 25 km. In addition, within the same framework, simulations of the current climate, driven by ERA-Interim, were carried out for all areas with REMO2015 at a grid resolution of approx. 25 km.

Within the German Project ViWA (Virtual Water Values, https://viwa.geographie-muenchen.de), simulations with the regional climate model REMO2015, driven by ERA-INTERIM analyses were carried out for the same regions globally, but on a significantly higher spatial resolution of approx. 12.5 km. These simulations cover the time period from 2015 to 2018. Comparing these highly resolved simulations to the coarsely resolved CORDEX-CORE simulations, can give indications, in which regions and for which processes the CORDEX-CORE resolution of 25 km is sufficient and where a higher resolution brings a clear added value.

We will show first results of this comparison, focusing on selected regions and processes which potentially benefit from higher spatial resolution of the simulations.
Multitemporal analysis of change of soil use and vegetable coverage for the development of a probabilistic prospective model and estimation of carbon stock in the capucuy river basin
Authors: Salazar Jose , Campos Carolina , Chamorro Pablo , Fernández De Arroyabe Pablo
Published: March 2020

The main objective of this research is to build a simulation model of land use change and coverage (LULC) of the Capucuy River Basin (Ecuadorian Amazon Region) by the year 2026 through the use of official historical cartographic information to estimate changes in LULC and carbon stock. First, it was quantified and defined the most representative anthropic drivers that have been affected LULC in the basin and modeled with historical LULC cartography from the years 1990 to 2016 with the help of DYNAMIC EGO program. Second, forest biomass was determined using an indirect method where 3 forest plots were established to obtain dasometric parameters and estimated the carbon stock of each different type of forest of the basin. Finally, agricultural carbon stock was determined with surveys and secondary data through the use of DNDC program. The results obtained show that the simulation of the maps of 2008 - 2016 allows us to obtain a simulated map of 2026 with an error of less than 5%, presenting the most significant error in the anthropic area with a 3.18% difference. It is expected that by 2026 the forest, the body of water, agricultural land and the anthropic zone occupy 56.83 %, 2.14 %, 40.09 % y 1.34 % of the total area of the Capucuy River Basin, respectively. Also, this model allowed to estimate the carbon stock reduction and its impact on climate change.
Acceleration of particles in different parts of erupting Coronal Mass Electrons
Authors: Zharkova Valentina , Xia Qian , Dahlin Joel , Antiochos Spiro
Published: March 2020

We examine particle energisation in CMEs generated via the breakout mechanism and explore both 2D and 3D MHD configurations. In the breakout scenario, reconnection at a breakout current sheet (CS) initiates the flux rope eruption by destabilizing the quasi-static force balance. Reconnection at the flare CS triggers the fast acceleration of the CME, which forms flare loops below and triggers particle acceleration in flares. We present test-particle studies that focus on two selected times during the impulsive and decay phases of the eruption and obtain particle energy gains and spatial distributions. We find that particles accelerated more efficiently in the flare CS than in the breakout CS even in the presence of large magnetic islands. The maximum particle energy gain is estimated from the energization terms based on the guiding-center approximation. Particles are first accelerated in the CSs (with or without magnetic islands) where Fermi-type acceleration dominates. Accelerated particles escape to the interplanetary space along open field lines rather than trapped in flux ropes, precipitate into the chromosphere along the flare loops, or become trapped in the flare loop top due to the magnetic mirror structure. Some trapped particles are re-accelerated, either via re-injection to the flare CS or through a local betatron-type acceleration associated with compression of the magnetic field. The energy gains of particles result in relatively hard energy spectra during the impulsive phase. During the gradual phase, the relaxation of the shear in magnetic field reduces the guiding magnetic field in the flare CS, which leads to a decrease in particle energization efficiency.
Decreasing hydrothermalism at Pamukkale- Hierapolis (Anatolia) since the 7th century
Authors: Ghaleb Bassam , Hillaire-Marcel Claude , Ozkul Mehmet , Kulali Feride
Published: March 2020

The dating of travertine deposition and groundwater / hydrothermal seepages in relation to late Holocene climatic changes can be achieved using short-lived isotopes of the 238U decay series, as illustrated by the present study of the Pamukkale travertine system, at the northern edge of the Denizli and Baklan graben merging area (see Özkul et al., 2013; https://doi.org/10.1016/j.sedgeo.2013.05.018. The strongly lithified self-built channels and modern pools where analysed for their 238U, 234U, 230Th, 226Ra, 210Pb and 210Po contents, whereas 238U, 234U and 226Ra were measured in modern hydrothermal waters. When corrected for detrital contamination, 230Th-ages of travertine samples range from 1215±80 years, in the oldest self-built hydrothermal channels, to the Present (modern pool carbonate deposits) thus pointing to the inception of the existing huge travertine depositional systems during the very late Holocene, probably following the major Laodikeia earthquate of the early 7th century (cf. Kumsar et al., 2016; DOI 10.1007/s10064-015-0791-0). So far, the available data suggest three major growth phases of the travertine system: an early phase (7th to 8th centuries CE), an intermediate phase (~ 14th century CE) and a modern one, less than one century old. A more detailed survey of the travertine system would be needed to strengthen these age clusters, however, worth of mention is the fact they they broadly fit with the timing of humid episodes as reconstructed from a southern Turkey paleolake study (Jones et al., 2006; doi: 10.1130/G22407.1). Despite nearly identical 234U/238U activities in modern waters and travertines (1.132±0.006), the latter show decreasing 226Ra concentrations through time, from ~ 0.2 dpm/g in the oldest shelf-built channels to ~ 0.07 dpm/g in present day pool carbonates, thus pointing to a significant decrease in the hydrothermal activity since the inception of the travertine complex, and raising concerns about the response of the Pamukkale hydrothermal system to the present climatic trend. Indeed, the predicted decrease in precipitation of up to 30% in the forthcoming decades (Lelieveld et al., 2012; DOI 10.1007/s10584-012-0418-4) is likely to result in a lesser meteoritic water recharge of the aquifer system feeding the springs (Dilsiz, 2006; DOI 10.1007/s10040-005-0001-4).
Moving towards a fully probabilistic, end-to-end, impact-based, flood forecasting and warning system
Authors: Pilling Charlie
Published: March 2020

Set up in 2009, the UK Flood Forecasting Centre (FFC), is a successful partnership between the Environment Agency and the Met Office to provide national, operational, flood risk guidance. At the same time, we have a development programme to continuously improve flood forecasting. Operational for over a decade, the FFC has a strong portfolio and reputation amongst its users and customers. For example, the 2019 Responder Survey reported that 94% of those who have had contact with the FFC within the last 12 months are satisfied with the services provided.  

High impact, low probability events have been a feature of the first 10 years of the Flood Forecasting Centre. Probabilistic forecasting and risk-based approaches provide approaches to identify, forecast and warn for such events. Indeed, whilst these are currently successfully employed by various National Meteorological Hydrological Centres, there is also recognition (for example, World Meteorological Organisation) that effective forecasting and warning systems should be:

‘impact-based’;

driven by ensembles or realistic scenarios through an ‘end-to-end’ system (rather than precipitation ranges being simplified);

more objective, so using new tools such as ensemble ‘sub-setting’, pattern recognition and machine learning to extract most value.

The Environment Agency is implementing a new Delft-FEWS forecasting system this year, termed Incident Management Forecasting System (IMFS). This will introduce a step change in capability for probabilistic impact-based forecasting. Initially, rainfall and coastal scenarios (termed ‘best-estimate’ and ‘reasonable worst case’) will be used to drive end-to-end forecasting, which includes for example impact data bases for property, infrastructure and communities. This is very much a stepping stone in the technical (systems) and adaptive (people, culture) transformation to a fully probabilistic, end-to-end, impact-based, flood forecasting.

I will share some of our recent approaches to:

objective, ensemble based, forecasting, including the Natural Hazards Partnership surface water hazard impact model (driven by the Met Office MOGREPS precipitation ensembles) which goes live this year;

scenario generation and ensemble sub-setting to provide input to end-to-end, impact-based forecasting (IMFS);

next steps in moving to a fully probabilistic, end-to-end, impact-based, flood forecasting and warning system

I will also highlight some of our current challenges that we would love to work with others to solve.
Twelve-Year Landslide Risk Assessment in Villa de Independencia, Bolivia, with Sentinel-1 and ALOS-1/2 InSAR Observations
Authors: Song Chuang , Li Zhenhong , Utili Stefano , Yu Chen
Published: March 2020

Monitoring of slow landslide movement on a local scale with Interferometric Synthetic Aperture Radar (InSAR) observations can provide long-term deformation information and assist in identifying failure triggers. We combined three different tracks of satellite radar images spanning 12 years from ALOS-1 PALSAR-1, ALOS-2 PALSAR-2, and Sentinel-1 to assess the evolution of a landslide in Bolivia where the village of Independencia lies at the slope foot. For ALOS-1 PALSAR, SAR data was acquired on 15 dates during the period from 28 February 2007 to 11 March 2011 in ascending mode. For ALOS-2 PALSAR-2, eight acquisitions between 07 October 2015 and 29 November 2017 were available in ascending mode. The low temporal resolution of ALOS images makes the detection of deforming signal difficult though the L-band data captures more coherent pixels on vegetation areas than C-band. Sentinel-1 data with a minimum time interval of six days from 16 October 2014 to 08 September 2019 (144 images) is collected and processed to recover the dynamic behaviour of the landslide movement.

To explore the sensitivity of different InSAR time series analysis methods on revealing the deformation pattern of the landslide, we respectively used Persistent Scatterer Interferometry (PSI), Small Baseline Subset (SBAS) algorithm and Distributed Scatterer Interferometry (DSI) based on phase eigenvalue-decomposition to process the mentioned multiple satellite radar observations. Overlapping valid pixels from these three methods share similar temporal evolution while SBAS and DSI trace more measurement points than PSI in spatial distribution. Preliminary results show that the village central exhibits extremely slow movements (<= 10 mm/yr) with seasonal oscillation. The north edge of the village in the middle of the landslide body retains stable until 2018. Deformation time series after early 2018 perform an acceleration from about 5 mm/yr to 15 mm/yr. Such acceleration may result from artificial irrigation activities, precipitation or internal landslide reactivation, and we expect to collect more ground evidence to interpret the acceleration. To conclude, the failure risk of this landslide is relatively higher since 2018 and is more noteworthy than before.
Microrefugia - limiting factors and unique synergy of environment
Authors: Słowińska Sandra , Słowiński Michał , Noryśkiewicz Agnieszka M. , Lamentowicz Mariusz , Kołaczek Piotr
Published: March 2020

Peatlands are a very important ecosystem which are characterized by distinctive vegetation, hydrology, and local climate. In the last decades, much effort was made a better understanding of microrefugia and their importance. Nevertheless, we still have little knowledge about the histories of the refugia. In the day of rapid climate change and increasing anthropogenic pressure, knowledge about the history of sites that represent a refugium of flora or fauna is a key aspect. The aim of this study is reconstructing the history of the glacial relict Betula nana in northern Poland located far from the southern range of its natural distribution. We suppose that the persistence of Betula nana is driven by a) the morphology and geology of the catchment, b) the maintenance of open vegetation on the peatland surface and c) exceptional microclimatic and hydrological conditions. Here, based on recent eco-hydrological monitoring and long-term palaeoecological proxy we try to be understated postglacial refugia of Betula nana from Central Europe (Linje mire). Detailed research was carried out on the peat profile using pollen analysis, to reconstruct the presence of open habitat on the mire during the Holocene. Pollen and macrofossils analysis revealed a continuous presence of Betula nana in the postglacial history of the peatland. Palaeoecological results show the variable situation of the Betula nana population in the peatland over the past 12 ka, indicating a strong relationship between paleohydrology and changes in the occurrence of this species. Our results of 12 years of local monitoring indicated that the mire is characterized by specific local climate and diverse water table depth. A synergy of local relief, microclimates, hydrology, and geology of the catchment affects the Betula nana population during the post-glacial history.
Effect of drop size distribution on microwave link rainfall retrieval at E-band
Authors: Fencl Martin , Bares Vojtech
Published: March 2020

Rainfall retrieval with commercial microwave links (CMLs) relies on the relation between radiowave attenuation and rainfall intensity. The CMLs used to operate predominantly at 15-40 GHz frequency region where the relation between rainfall and attenuation was close-to-linear and only slightly dependent on drop size distribution (DSD) (Berne and Uijlenhoet, 2007). New generation of CMLs operated within cellular backhaul utilizes increasingly the E-band frequencies, specifically frequency region 71 - 86 GHz. The attenuation-rainfall relation at this region is, however, substantially more dependent on DSD.

One year of DSD data retrieved from Parsivel OTT disdrometer is used to simulate theoretical attenuation and quantify the effect of DSD on CML rainfall estimates. The results show that E-band CMLs are highly sensitive to DSD. The relative error related to DSD variability reaches up to 40%, which is about two to three times higher value compared to errors by CMLs operated at 15-40 GHz. These errors can be, however, reduced to approx. 20% when distinguishing between stratiform and convective rainfalls and introducing two different parameter sets for attenuation-rainfall relation, accordingly.  The improvement of CML rainfall estimates when adapting parameters of attenuation-rainfall relation is demonstrated on real attenuation data acquired from 4.8 km long E-band CML operated within cellular backhaul in Prague (CZ).

Variable drop size distribution represents a significant source of uncertainty in rainfall estimates retrieved from E-band CMLs. This uncertainty can be substantially reduced by adapting parameters of attenuation-rainfall model to rainfall type (DSD).

 

References:

Berne, A., Uijlenhoet, R., 2007. Path-averaged rainfall estimation using microwave links: Uncertainty due to spatial rainfall variability. Geophys. Res. Lett. 34, L07403. https://doi.org/10.1029/2007GL029409
The choice of grass species to combat desertification in semi‐arid Kenyan rangelands is greatly influenced by their forage value for livestock
Authors: Nyariki Dickson , Musimba Nashon , Nyangito Moses , Mwang'ombe Agnes , Mganga Kevin
Published: March 2020

Livestock production is the main source of livelihood in the arid and semi‐arid lands in Africa. However, desertification characterized by vegetation degradation and soil erosion is a major threat to the sustainability of land‐based production systems. Native rangeland forage species Cenchrus ciliaris L. (Buffel grass/African foxtail grass), Eragrostis superba Peyr. (Maasai love grass) and Enteropogon macrostachyus (Hochst. Ex A. Rich.) Monro ex Benth. (Bush rye grass) have been used to combat desertification. The objectives of the study were to identify the best‐suited native grass species to combat desertification in a semi‐arid environment in Kenya and to identify the preferred grass species among the agropastoralists in the area. Percentage basal cover, plant densities and frequencies of the three grasses in pure stands and mixtures were estimated. Grass species preferences were through household survey and focus group discussion. Results showed a significant difference (P < 0·05) in plant densities and cover estimates: E. macrostachyus was ranked first; C. ciliaris and E. superba were ranked second and third respectively. The agropastoral farmers, however, preferred E. superba followed by C. ciliaris and E. macrostachyus, a reverse trend. These results suggest that the choice of grass species to combat desertification is influenced more by its contribution as a source of forage for livestock than its contribution for rehabilitation purposes.
Offsets and inputs of natural uranium isotopes in the Mediterranean Sea
Authors: Border Evan , Frank Norbert , van Beek Pieter , Henderson Gideon , Tamborski Joseph
Published: March 2020

High precision measurements of natural uranium isotopes in the Atlantic Ocean, Mediterranean Sea,
and Black Sea reveal isotopic makeups which differ significantly from the well-known oceanic
composition. In the Mediterranean, water masses are strongly differentiated to the extent that they
are able to be fingerprinted on the basis of δ234U. Mediterranean deep water masses show the
highest enrichment, with an offset with respect to oceanic δ234U values of just over 1 ‰. The Black
Sea shows an even higher offset of up to ~40 ‰.
This offset provides an opportunity to look into the as of yet largely unstudied uranium inputs to the
Mediterranean, in particular rivers and submarine groundwater discharge (SGD), which are thought
to play key roles in uranium input to the global ocean. A simple box model, incorporating the
Mediterranean and Black Sea data from this study is constructed to provide a first estimate of the U
concentration and δ234U signature of rivers and SGD necessary for this offset to arise. These
estimates are then compared with new measurements of various coastal and submarine springs from
along the French Mediterranean Coast as well as with existing riverine data exists to speculate on
which inputs may be most responsible for this offset.
Understanding the relationship between extremes of wind and inland flooding in the UK
Authors: Halliday Oliver , Shaffrey Len , Tsaknias Dimosthenis , Cloke Hannah , Siddaway Alexander
Published: March 2020

Windstorms and flooding pose a significant socio-economic threat to the United Kingdom andcan cause significant financial loss. For example, the great October storm of 1987 damaged whole elements of the national electricity grid in the west of the UK. Storms can also be associated with heavy precipitation, for example, extensive inland flooding was caused by a series of slow-moving storms in the case of the winter floods of 2013/14 in the South East of England. The UK Met Office and Environment Agency estimated the financial loss attributable to the 1987 and 2013/14 events at €6.4bn and €1.5bn respectively. The question of correlations between windstorm and flood events remains open, for example the risk of a 1987-scale event "colluding" with the economically adverse meteorology of the 2013/14 season being poorly unquantified. If wind and flood risk is correlated then insurers are under-estimating both capital requirements and risk policy price, exposing them to very substantial liabilities.

Here, a collaborative project between academics and insurers has been undertaken to improve our understanding of the spatial-temporal distribution of risk from extreme, compounded windstorm and inland flood events in the UK. Statistical analysis of different data sets (~40 years of winter ERA5 reanalysis daily maximum winds, as well as observational precipitation and river flow gauge data) reveals wind and inland flooding are modestly correlated across the UK. In addition, we find substantially more compound events than expected by chance, some of which can be linked to named UK storms.

In terms of the large-scale atmospheric drivers, there appears to be no particular preferred path for the storms associated with compound wind and flood events. However, we find that compound events appear to be moderated by the amount of rainfall in the days preceding a windstorm, rather than the overall storminess of any given year. Further, we investigate the relationship in very extreme (200-year return period) windstorms and precipitation from the 1000-years of high-resolution HiGEM climate simulations.

 

 

 

 
The role of afterslip in driving aftershock sequences
Authors: Churchill Robert , Werner Maximilian , Biggs Juliet , Fagereng Ake
Published: March 2020

Aftershock sequences following large tectonic earthquakes exhibit considerable spatio-temporal complexity and suggest causative mechanisms beyond co-seismic, elasto-static Coulomb stress changes in the crust. Candidate mechanisms include dynamic triggering and postseismic processes such as viscoelastic relaxation, poroelastic rebound and aseismic afterslip, which has garnered particular interest recently. Aseismic afterslip – whereby localized frictional sliding within velocity-strengthening rheologies acts to redistribute lithospheric stresses in the postseismic phase – has been suggested by numerous studies to exert dominant control on aftershock sequence evolution, including productivity, spatial distribution and temporal decay.

As evidence is based overwhelmingly on individual case study analysis, we wish to systematically compare key metrics of aseismic afterslip and corresponding aftershock sequences to investigate this relationship. We specifically look for any empirical relationship between the seismic-equivalent moment of aseismic afterslip episodes and the corresponding aftershock sequence productivity. We first compile published afterslip models into a database containing moment estimates over varying time periods, as well as spatial distributions, temporal decays and modelling methodology as a supplementary resource. We then identify the corresponding aftershock sequence from the globally comparable USGS PDE catalog. As expected, coseismic moment exerts an obvious control on both afterslip moment and aftershock productivity – an effect we control for by normalising by mainshock moment and expected productivity (the Utsu-Seki law) respectively. Preliminary results suggest broad variability of both afterslip moment and aftershock productivity with no obvious control of afterslip on aftershocks beyond the scaling with mainshock size, including when separated by mainshock mechanism or region. As this study is insensitive to spatial and temporal distributions, we cannot rule out the potential influence afterslip exerts in these but find no evidence that afterslip drives overall productivity of aftershock sequences.
Mapping sediment carbon in a large tropical reservoir: burial of terrestrial and aquatic organic carbon, and occurrence of potential methane ebullition hot spots
Authors: Sobek Sebastian , Mendonça Raquel , Isidorova Anastasija , Grasset Charlotte
Published: March 2020

Reservoirs efficiently trap the riverine sediment flux, and therefore rapidly accumulate sediment. Since the sediments contain organic carbon (OC), reservoirs globally store significant amounts of OC in their sediments. The source of the OC buried in reservoir sediments is currently not well-known, but has important implications for the accounting of reservoir C burial as a new anthropogenic C sink. On the other hand, sediment OC can be degraded to the greenhouse gas methane (CH4) in anoxic sediment layers, and at high sediment accumulation rates, CH4 reaches oversaturation and forms gas bubbles which efficiently transport CH4 to the atmosphere. Accordingly, CH4 ebullition (bubble emission) is the main pathway of the globally significant CH4 emission by reservoirs. Both sediment OC accumulation and CH4 production is spatially extremely heterogeneous in reservoirs, and we currently lack understanding of the drivers of this spatial variability. We therefore mapped the spatial variability of sediment OC accumulation and of gas bubble-rich, CH4-oversaturated sediments in a large (1300 km2) tropical reservoir in Brazil, using both seismic sub-bottom profiling and sediment coring. In addition, we performed analyses of the sediment stable isotopic signature (13C and 15N) and lipid biomarkers (alkanes, alkanols, and acids) in order to discern the origin of the buried OC. We found that the OC accumulation rate was strongly dependent on the sedimentation rate, which in turn varied with water depth, bottom slope and proximity to river inflows. The spatially-resolved mean OC burial rate was 44 g C m-2 yr-1, twice as high as the global average for natural lakes, but lower than the global average for reservoirs. Gas bubble-containing sediment was detected in 30% of the sub-bottom survey length and occurred along the whole reservoir, but was most abundant in areas of high primary productivity, high sediment accumulation rate, and < 25 m water column depth. Evidence from stable isotopes and lipid biomarkers indicates that a significant share of the OC accumulating in the reservoir sediment is of aquatic origin, and therefore is accountable as a new C sink that results from reservoir construction. These results indicate that the spatial variability of both the burial of OC from terrestrial and aquatic origin, and of gas bubble-rich sediments prone for CH4 ebullition can be understood from the reservoir characteristics.
Lithostratigraphic Mapping Through Saprolitic Regolith Using Soil Geochemistry and High-Resolution Aeromagnetic Surveys.
Authors: Twigg Helen , Hitzman Murray
Published: March 2020

The Neoproterozoic Central African Copperbelt located in southern Democratic Republic of Congo (DRC) and the northwestern Zambia and contains 48% of the world’s cobalt reserves and significant resources of copper, zinc, nickel and gold. A good understanding of the geology is critical for successful mineral exploration. However, geological mapping is hindered by low topographic relief, limited outcrop, and a generally deep (10-100m) weathering profile developed since the Late Miocene.  Multielement soil geochemistry provides a means for conducting geological mapping.   Areas with outcrop or containing drill holes and/or trenches were utilized to relate known geological lithologies with soil geochemical results using major element and trace element ratios.

The lithostratigraphy within a study area along the DRC-Zambia border can be geochemically sub-divided into three units. Mixed carbonate and siliciclastic lithologies of the lower portion of the local stratigraphy are typically characterised by elevated V, Ti, and Nb. Mudstones and siltstones are dominated by elevated Al, Fe and Ba. The upper portion of the local stratigraphy is geochemically neutral with regards to trace elements.  Lithological discrimination through analysis of soil geochemical data is limited in some areas by intense weathering. A A-CNK-FM diagram exhibits how complete weathering of carbonate rocks and carbonate-rich breccias (after evaporites) results in the somewhat counter intuitive outcome that residual soils above carbonate rocks are amongst the most aluminum rich in the study area with >80% Al2O3 (mol%) or >80% combined Al2O3 (mol%) and FeO + MgO (mol%). The weathering of siliciclastic rocks (siltstones, mudstones, and diamictites) result in a shorter weathering path across a A-CNK-FM diagram, probably due to their higher original proportion of resistate phases.

An area specific geochemical database of baseline lithostratigraphy weathering paths allows the identification of atypical geochemistry which could indicate facies change, alteration or mineralization.
Unification of the Australian cratons before the formation of Nuna
Authors: Kirscher Uwe , Mitchell Ross , Liu Yebo , Nordsvan Adam , Cox Grant , Pisarevsky Sergei , Li Zheng-Xiang
Published: March 2020

The paleogeography and chronology of the Paleoproterozoic supercontinent Nuna are highly debated. To further test the paleogeography of Australian cratons in the leadup to Nuna formation, we present new paleomagnetic results from two Paleoproterozoic rock formations in North Australia. First, we obtained paleomagnetic directions from the 1825±4 Ma, bimodal Plum Tree Creek Volcanics sequence located within the Pine Creek Inlier of the North Australian Craton. Second, we studied the 1855±2 Ma layered mafic-ultramafic ‘Toby’ intrusion from the Kimberley Craton (KC). Samples from both study areas reveal high quality, stable, magnetite related characteristic remanent magnetization directions. Combining within-site clustered mean directions, we obtained two paleopoles, which plot proximal to each other in the present day central Pacific Ocean, off the east coast of Australia. These results agree with previous interpretation that the Kimberly Craton was amalgamated with the rest of the North Australian Craton (NAC) prior to ca. 1.85 Ga. Comparing these new results with slightly younger poles from the NAC and slightly older, rotated poles form the West Australian Craton (WAC) reveal a high degree of clustering suggesting very minimal absolute plate motion between ca. 1.9-1.85 and 1.6 Ga before the final amalgamation of Nuna. All available paleomagnetic poles agree with an assembly, or close juxtaposition, of the two major Australian cratons (NAC and WAC) before 1.8 Ga. Furthermore, the individual virtual geomagnetic poles from the potentially slow cooled Toby intrusion show a non-fisherian distribution along a great circle. This spread might be related to previously interpreted major true polar wander events based on Laurentian data, which would be global if such an interpretation is correct. The assembly of proto-Australia prior to ca. 1.85 Ga roughly 250 to 300 Myr before the final stage of supercontinent Nuna’s amalgamation ca. 1.6 Ga suggests that assembling of major building blocks, such as Australia and Laurentia for the supercontinent Nuna and Gondwana for the supercontinent Pangea, is an important step in the formation of supercontinents.