bluuebunny/crossref_metadata_2025 huggingface dataset:
Primary and Secondary Gold Sources of Quaternary Placers of Western Spain: a Morphotextural and Compositional Analysis of the Fresnedoso Deposit.
Authors: Dos Santos Alves Kelvin , Barrios Sánchez Santos , Gómez Barreiro Juan , Merinero Palomares Raul , Pablo Lozano Fernández Rafael , Manuel Compaña Prieto José
Published: March 2021

In this contribution we have investigated the Fresnedoso Quaternary gold placer (Western Spain), analyzing the morphotextural and microchemical evolution of gold particles. The statistical analysis has revealed the presence of two populations of particles being consistent with primary sources situated at a distal [20 - 50 km] and a proximal [2.5 - 10 km] range. The gold morphology and chemistry point to a recycling (and potentially undiscovered) Tertiary paleoplacers. The discovery of primary laminar morphologies points to lode deposits in small-flat veins hosted in Precambrian metasediments (Schist Greywacke Complex). All these findings suggest that the Fresnedoso gold deposit is formed by mono and polycyclic particles. We have tested previous transport distance vs Flattening indexes (CFI, Shilo) models resulting in useful framework for exploration of undiscovered ores, even with a small sample dimension. Chemical analysis of the different gold morphologies depicted that the Fresnedoso gold is a AuAg bimetallic alloy. Three groups were identified based on the texture and composition of the gold particles: Type 1 (Au1= Au89-94Ag11-6), Type 2 (Au2= Au99 Ag1) and Type 3 (Au3~ Au >99). Particle's cores (gold Type 1) show a compositional range that could be interpreted as differences in primary sources, spatial dispersion of sources or the actuation of secondary processes, probably in an orogenic gold context. Microchemical heterogeneity in the particles is probably due to secondary processes. A conceptual model has been elaborated to explain particle's microchemical domains represented by gold Type 2 (rim) and Type 3 (micro-aggregates) as the result of two different de-alloying stages: A) initial Ag-leaching at the rim and/or through microcracks and grainboundaries (Type 2), B) Total reset of the primary chemical fingerprint, with porous microtexture and the precipitation of gold with iron oxyhydroxides and clays (Type 3). This model suggests a silver de-alloying mechanism favored in a chlorine-iron-rich environment as in the case of laterites. Deformation and eventually recrystallization mechanisms associated with the fluvial transport (mechanical cold-work), cooperated in the evolution of the particles (Dos Santos et al. 2020).

References 

Dos Santos Alves, K., Barrios Sánchez, S., Gómez Barreiro, J., Merinero Palomares,R. and Compaña Prieto, J.M. (2020). "Morphological and compositional analysis of alluvial gold: The Fresnedoso gold placer (Spain)." Ore Geology Reviews : 103489.
Impact of Land Management on Available Water Capacity of Peat Soil
Authors: Liu Haojie , Tanneberger Franziska , Lennartz Bernd
Published: March 2021

In Central Europe, about 90% of fen peatlands have been drained for agriculture and forestry leading to greenhouse gas emissions and soil degradation. Soil available water capacity (AWC) is one of the most important soil properties regulating the water balance at a given site and plays, thus, a pivotal role in plant growth. Compared with that of mineral substrates, our understanding of the AWC of peat is limited. In this study, we aimed to deduce possible alterations of the AWC of peat following soil degradation. We analysed a comprehensive database (674 measurements from boreal and temperate peatlands) to seek relations between bulk density (BD) and total porosity, field capacity, wilting point, and AWC. Bulk density was used as a proxy for peat degradation as it is closely correlated with the soil organic matter content. The AWC increases gradually with BD up to a value of 0.2 g cm−3; a further increase in BD leads to a considerable decrease in AWC. The increase in AWC occurs within the first 15 to 30 years of land drainage, depending on the initial soil BD before drainage. The function between BD and AWC enables us to upscale the AWC to a regional scale. The average AWC of agricultural peatlands in Germany is estimated to be 37 ± 11 vol% (mean ± standard deviation). In Germany, the AWC decreases with increasing soil depth for highly degraded peatlands, which are characterised by BD values of 0.4 g cm−3 > BD > 0.2 g cm−3. However, for extremely degraded peatlands (BD > 0.4 g cm−3), the AWC increases with increasing soil depth. For those highly and extremely degraded peatlands, we estimated that 1 wt% organic carbon loss causes a drop of 1.25 vol% in AWC. Peatland rewetting may increase soil AWC, however, plants may still suffer from a water deficit under extreme dry weather conditions.
Using Earth Observation to track lithium movements in the Salar de Uyuni region, Bolivia
Authors: Rossi Cristian , Ford Jonathan , Bayaraa Maral , Bateson Luke , Butcher Andrew , Petavratzi Evi , Huges Andrew
Published: March 2021

The increasing global effort to overcome the reliance on fossil fuels is driving the demand for ‘green’ metals such as lithium. This study aims to develop a repeatable and seamless workflow to track the mass of lithium from its source in the watershed surrounding South American salt lakes (“salars”) to the nucleus of the salar itself. The area of interest is in and around the Salar de Uyuni, Bolivia, the largest salt flat in the world. We aim to create an understanding of how Li brine deposits develop, where the water and solute comes from, how the brines are created and how does abstraction affect the mass balance within the salar. For this research, open source Earth observation (EO) data is analysed to support geological and hydrological research. We explore the potentials of EO data for several research aspects, such as (1) Jointing: it may influence fracture-flow of groundwater and also be significant in terms of surface-area for water-rock interaction, i.e. potentially increasing the ‘leaching’ rates of Li from the bedrock into the water; (2) Weathering: the degree and style of weathering may influence the liberation of Li from rocks into the water; (3) Distribution of clays: the distribution of clays that may restrict the liberation of Li from weathered rock, or may scavenge Li from passing water; (4) Water and moisture: the distribution of water-bodies and sources, including active streams, springs etc. We are building a groundwater recharge model having as input soil moisture content; (5) Geological structure: the presence of neotectonic faults that may disrupt the salar, as well as structures that may provide pathways for the flow of fluids; (6) Lithological mapping and classification: possible refinement of existing geological maps. This workflow will support the sustainable management of lithium in the region. Moreover, the provision of “fit for purpose” systems of tracking Li helps in filling gaps in existing methods to enable Li brines resources to be correctly reported.
Ore fluid characteristics at Gadag Gold Field, Dharwar Craton, southern India: Evidences from tourmaline chemistry and fluid inclusion study
Authors: Pal Debasis , Chinnasamy Sakthi Saravanan , Rekha Sukumari
Published: March 2021

Dharwar Craton in southern India hosts several gold bearing greenstone belts including the well-known Kolar and Hutti. Among them, the Gadag greenstone belt in the western part of Dharwar Craton contains many potential gold mines. It has three different lode systems named western, central and eastern lodes. These lodes are spatially distributed as linear groups along the shear zone with distinct lithological assemblages. Tourmaline is one of the most common hydrothermal minerals present in the alteration zones apart from chlorite, muscovite and sericite. These tourmalines show two textural association (i) occur as isolated, euhedral grains along the mylonitic foliation defined by chlorite, muscovite, sericite, quartz and carbonates (ii) occurrences of anhedral bizarre shaped tourmaline grains along with carbonate and quartz. Though texturally different, compositionally both the tourmalines are similar. They are dravite in nature with high Altot (6.02 to 6.56 apfu), low Na (0.42 to 0.88 apfu) and medium X-vacancies (0.08 to 0.57 apfu). The predominance of Fe2+ (high Fe2+/Fe3+) and low Na in the tourmaline crystal structure indicates low saline, reduced ore fluid of metamorphic origin that is responsible for gold mineralization in Gadag.

Microthermometric study of aqueous, carbonic and aqueous-carbonic inclusions from the auriferous lodes at Gadag reveal low to medium saline (0.04 to 9.59 NaCl equiv.)  H2O-NaCl-CO2±CH4 ore forming fluid. Presence of trace amount of methane content within the carbonic inclusion indicates mineralization occurred at reducing environment. Thus, fluid inclusion results consistent with the tourmaline chemistry and strongly supports the metamorphic origin of ore fluids that responsible for gold mineralization at Gadag.
Analysis of magnetotelluric data from Las Cañadas caldera (Tenerife, Spain)
Authors: Martínez van Dorth David , Di Paolo Federico , Slezak Katarzyna , Cabrera-Pérez Iván , Piña-Varas Perla , Ledo Juanjo , Bidaurrazaga Aguirre Garazi , Sáez Gabarrón Lucía , Przeor Monika , Hernández William , D'Auria Luca , Pérez Nemesio M.
Published: March 2021

Tenerife is the second-largest island in the Canarian archipelago with an area of 2034 km2. It consists of three ancient volcanic massifs (Anaga, Adeje and Teno) located at the edges of the island connected by rift zones to the centre of the island, in correspondence of Las Cañadas caldera. The caldera hosts the most relevant topographic element of Tenerife, the volcanic edifice of Teide – Pico Viejo. Previous studies already suggested the presence of geothermal resources inside and around the caldera. For this reason, in the present study, we have applied the magnetotelluric method (MT) in the central part of the island to better understand subsurface structures in this area.

The MT method is a useful tool successfully applied to detect conductive and resistive structures located in the subsoil. It is commonly used in volcanic areas to detect volcano-tectonic features and geothermal systems to evaluate exploitable geothermal resources. Furthermore, continuous magnetotelluric measurements can also be employed for volcanic monitoring, allowing tracking temporal changes of the resistivity because of fluid transfer processes in the volcanic system.

Between 2019 and 2020 we realised a detailed study of Las Cañadas caldera resistivity structure thought 45 magnetotelluric soundings. The instrumentation consisted of four Metronix ADU-08e, equipped with EPF-06 electrodes and MFS-06e magnetic coils, which registered electric and magnetic fields along the N-S and E-W directions. We also installed three remote stations at different times inside the caldera. Depending on the station quality, we obtained the MT response functions for periods of 0.001 – 1000 s. The dimensionality of the data has been analysed using the phase tensor.  The first preliminary results of dimensionality and strike analysis indicate a 1D/2D behaviour for the first layers which present a decreasing resistivity, evolving to a 3D behaviour from 1s and with an increase of resistivity with depth.

Furthermore, we present some results obtained by a permanent MT station to check the possibility of temporal changes in the electrical resistivity. During the time this station was recording two electrical blackouts which took place on the island. This allowed quantitatively estimating the level of anthropogenic electromagnetic noise in the recorded time series.
The effects of the Syrian civil war on atmospheric NH3 as seen from IASI
Authors: Abeed Rimal , Safieddine Sarah , Clarisse Lieven , Van Damme Martin , Coheur Pierre-François , Clerbaux Cathy
Published: March 2021

The Syrian civil war started in 2011, with dramatic social, political, economic, and environmental consequences over the whole area of Syria and nearby countries. Agriculture, in particular, suffered massively. Several studies used satellite-retrieved data and imagery to examine the spatio-temporal changes in the region, due to the civil war. For instance, open-source satellite imagery could show the damage in urban areas, and provide an estimate of the number of people affected by the crisis.

In this study, we investigate the impacts of the Syrian civil war on atmospheric ammonia (NH3) emitted from industrial and agricultural activities during the 2008-2019 period. Our analyses are based on the NH3 measurements from the IASI instruments onboard the Metop satellites. Firstly, land-use changes and a decrease in agricultural emissions are explored over the country. We also investigate the changes in atmospheric NH3 over an ammonia plant, which activities have been suspended due to several conflict-related events. We show that the NH3 columns retrieved from IASI are directly affected by the war, and those periods of intense conflict and siege are reflected in lower NH3 concentrations, which are not driven by meteorology. The interpretation of the identified changes in atmospheric NH3 is supported by the analyses of NO2 columns from GOME-2 as well as satellite imagery and land cover data. The latter is used to highlight the change in croplands’ area over the years, and the satellite images are used to show the activity of the ammonia plant.
Relating biomolecular data to denitrification rates in infiltrating river water – insights from enzyme-based reactive transport modelling
Authors: Störiko Anna , Pagel Holger , Mellage Adrian , Cirpka Olaf A.
Published: March 2021

Biomolecular quantities like gene, transcript or enzyme concentrations related to a specific reaction promise to provide information about the turnover of nutrients or contaminants in the environment. Particularly transcript-to-gene ratios have been suggested to provide a measure for reaction rates but a relationship with rates currently lacks validation.
We applied an enzyme-based reactive transport model for denitrification and aerobic respiration at the river-groundwater interface to simulate the temporal and spatial patterns of transcripts, enzymes and biomass under diurnal dissolved oxygen fluctuations.
Our analysis showed that transcript concentrations of denitrification genes exhibit considerable diurnal fluctuations, whereas enzyme concentrations and biomass are stable over time. The daily fluctuations in denitrification rates yielded a poor correlation between rates and transcript and enzyme concentrations. Daily averaged reaction rates, however, show a close-to-linear relationship with enzyme concentrations and mean transcript concentrations.
Our findings suggest that, under dynamic environmental conditions, single-event sampling may result in the misinterpretation of biomelucular quantities as these relate to reaction rates. A better representation of rates can be achieved via sampling that captures the temporal variability of a particular system.
Long-term evolution of fracture permeability in slate as potential target reservoirs for Enhanced Geothermal Systems (EGS)
Authors: Cheng Chaojie , Herrmann Johannes , Rybacki Erik , Milsch Harald
Published: March 2021

The long-term sustainability of fractures in Variscan metamorphic rocks will determine whether it is reasonable to utilize such formations as potential unconventional EGS reservoirs. During long lasting fluid flow within fractures, dissolution, precipitation, and chemical reactions between the fluid and the rock matrix may alter the flow pathway structure and flow properties. Within the framework of the European Union's Horizon 2020 initiative "MEET (Multi-Sites EGS Demonstration)", we performed long-term fracture permeability experiments on saw-cut slate samples from the Hahnenklee drill site, Harz Mountains, Germany, under constant pressure and temperature conditions. Two experiments were performed using deionized water as pore fluid with intermittent flow for more than one month at 10 MPa confining pressure and 1 MPa pore pressure. Three sequential investigations were performed, including (1) an initial continuous flow tests at room temperature, (2) temperature cycles between room temperature and up to 70 °C or 90 °C, and (3) measurement of the time-dependent permeability evolution at 70 °C or 90 °C. During stage (3), the effluents were sampled in time intervals of 6 days and analyzed using inductively coupled plasma optical emission spectrometry (ICP-OES). The results show that (1) sample permeability first continuously decreases, but progressively converges within about three days, (2) increasing temperature leads to an additional permeability decline that is irreversible, and (3) the time-dependent permeability reduction is much more pronounced at 90 °C in comparison to that at 70 °C. The effluents are enriched with Na, Fe, K, Ca, Si, where the Na concentration is always an order of magnitude higher than the others. Except for Si, concentrations are progressively decreasing with time. During the entire experimental period, sample permeability was reduced by approximately 90% at 90 °C and 60% at 70 °C compared to their initial values. In contrast, both samples showed a negligible permeability decline with time at room temperature after cooling. Our results demonstrate that thermally-enhanced fluid-rock interactions lead to a permanent and at least partial closure of fracture aperture, which is unfavorable for geothermal exploitation. However, the degree of permeability reduction may strongly depend on initial fracture roughness, which remains to be investigated.
Finding appropriate boundary conditions for high frequency forcing of Regional Simulations – California Current System as a case study.
Authors: Siyanbola Oladeji , Buijsman Maarten , Barkan Roy , Arbic Brian
Published: March 2021

Quite a handful of past studies have reported lack of energy near the tidal bands in high-resolution, regional model simulations’ frequency-wave number spectra when compared to observations. A plausible reason for this discrepancy could be the lack of remotely generated internal tides in regional simulations. In this study, we consider the impact of remote internal tides on the energetics in regional simulations of the California Current System (CCS). The CCS is an eddy-rich mid-latitude region, where energetic NIWs and internal tidal waves coexist. We run high-resolution realistic regional simulations using the Regional Ocean Modelling System (ROMS). The ROMS simulations are boundary-forced with high-frequency offline data from the Hybrid Coordinate Ocean Model (HYCOM). We consider a year-long HYCOM expt_06.1 simulation with 8-km horizontal grid resolution and 41 depth layers. The HYCOM simulation is realistically forced with tides and atmospheric forcing.

Time-mean and depth-integrated internal tidal flux computed for the parent HYCOM domain shows radiation of remotely generated internal tide beams into the ROMS domain. These beams comprise mainly of modes 1 & 2. To ensure that we provide satisfactory open boundary conditions (OBCs) for our regional simulation, we conduct sensitivity runs using two main types of OBCs (clamped and adaptive OBCs). For the runs with clamped OBCs, we varied the sponge layer viscosities at the open boundaries from 100 to 800 m2/s. Both nudging parameters and sponge layer viscosities are varied for simulations with the adaptive OBCs.  Although, we observe remotely generated internal tides in all our simulations, we find that the amount of internal tidal energy that is transmitted through the open boundaries and the internal tidal energetics in the interior of the domain depend on the nudging time scales, sponge layer width and/or viscosity values.

In the future, we plan to nest down to increasing high-resolution horizontal and vertical grids and perform simulations with different boundary forcings e.g. with total internal tides, stationary internal tides, and no internal tides. We will also force the ROMS model with unidirectional internal tides. We will evaluate the impacts of these scenarios on the internal tide energetics in the ROMS domain.
On the connection between coastal Ekman upwelling and wind-stress-curl-driven upwelling off the southwest African coasts
Authors: Bordbar Mohammad Hadi , Mohrholz Volker , Schmidt Martin
Published: March 2021

Spatial and temporal variations of nutrient-rich upwelled water across the major eastern boundary upwelling systems are primarily controlled by the surface atmospheric flow with different, and sometimes contrasting, impacts on coastal and open-ocean upwelling systems. Here, concurrently measured wind-fields, satellite-derived Chlorophyll-a concentration along with a state-of-the-art ocean model simulation spanning 2008-2018 are used to investigate the connection between coastal and offshore physical drivers of the Benguela Upwelling System (BUS). Our results indicate that the spatial structure of long-term mean upwelling derived from Ekman theory and the numerical model are fairly consistent across the entire BUS and closely followed by the Chlorophyll-a pattern. The variability of the upwelling from the Ekman theory is proportionally diminished with offshore distance, whereas different and sometimes opposite structures are revealed in the model-derived upwelling. Our result suggests the presence of sub-mesoscale activity (i.e. filaments and eddies) across the entire BUS with a large modulating effect on the wind-stress-curl-driven upwelling off Lüderitz and Walvis Bay. In Kunene and Cape Frio upwelling cells, located in the northern sector of the BUS, the coastal upwelling and open-ocean upwelling frequently alternate each other, whereas they are modulated by the annual cycle and mostly in phase off Walvis Bay. Such a phase relationship appears to be strongly seasonal dependent off Lüderitz and across the southern BUS. Thus, our findings suggest this relationship is far more complex than currently thought and seems to be sensitive to climate changes with short- and far-reaching consequences for this vulnerable marine-ecosystem.
New insight of the West Tropical Atlantic Circulation based on 25 years of satellite altimetry, PIRATA data and GLORYS ocean reanalysis
Authors: Hernandez Fabrice , Dimoune Djoirka M. , Birol Florence , Leger Fabien , Araujo Moacyr
Published: March 2021

Satellite altimetry offers a mesoscale description of the ocean surface circulation worldwide since 1993. The Mercator Océan GLORYS12 reanalysis complement this description with a consistent 3-dimensional estimation of ocean physical parameters over the same period, with a reliability supported by the assimilation of available in-situ and satellite data. This information is used to revisit the ocean circulation description over the West Tropical Atlantic and in particular the seasonal and interannual variability of the western boundary current system from 20°S to 20°N connected to the tropical Atlantic basin scale circulation. PIRATA data since 2000 are used to validate the ocean reanalysis, and complement the description at depth of the main currents. The variability pattern and main characteristics of the North Brazil Undercurrent, the North Brazil Current and its Retroflection (NBCR), and the connections with the Equatorial Undercurrents, the South and North Equatorial Currents (SEC/NEC) and CounterCurrents (NECC) show seasonal changes. Both of their main pattern and the associated mesoscale field are dominated by the seasonal regimes. This circulation is linked to the tropical Atlantic Climate variability and the coupled pattern of wind and ocean dynamics. In particular, we show that the interannual variability of NECC, depending on the NBCR and SEC/NEC water transport exhibits different branches in relation with Tropical Atlantic Zonal and Meridional Mode of variability.
Hydrosedimentary connectivity in a disturbed forested catchment: toward a temporally dynamic index of connectivity
Authors: Maltais Maxime , Jautzy Timothée , Buffin-Bélanger Thomas
Published: March 2021

Hydrosedimentary connectivity refers to the potential fluxes of water and sediment moving throughout a catchment. In forested catchments, these fluxes are altered by anthropogenic and natural disturbances. In this study, we modelled the interannual spatiotemporal evolution of hydrosedimentary connectivity influenced by forest cover change over the last four decades in the Mont-Louis catchment, a snow-dominated mountainous catchment in eastern Canada, which had 62% of its total surface affected by forest disturbances (mainly logging, but also wildfires and diseases) between 1979 and 2017. Using a geomorphometric index of connectivity (IC) and a historical forest cover database, we produced one IC map per year that considered anthropogenic and natural disturbances affecting the forest cover of the studied catchment. To account for vegetation recovery, forest disturbances were weighted with local hydrological recovery rates. Over the four decades, the mean IC of the Mont-Louis catchment dramatically increased by 35% in response to different types of disturbances. The spatial evolution of IC over the whole catchment and at the sub-catchment scale revealed that disturbance location has a strong influence on hydrosedimentary connectivity to the main channel. Our results also highlight the sharp contrast between IC computed from topography-based impedance to those computed from vegetation-based impedance. Forest disturbances appear to connect hillslopes with the hydrological network by producing pathways for sediment and water. The proposed reproducible framework might be used as a tool to assess and predict the potential impact of harvesting on rivers morphological dynamics and eventually preventing damage to fish habitat and sensitive river reaches.
Large volcanic eruptions as a natural hazard: The impact of the 536/540 CE double event on the atmospheric circulation, surface climate, vegetation and society in Scandinavia
Authors: van Dijk Evelien , Gundersen Ingar Mørkestøl , Bajard Manon , Høeg Helge , Løftsgård Kjetil , Iversen Frode , Timmreck Claudia , Jungclaus Johann , Krüger Kirstin
Published: March 2021

Large volcanic eruptions that reach the stratosphere cool the surface climate and impact the atmospheric circulation, feeding back on the local climate. The mid-6th century is an outstanding period in climate history that featured an extreme cold period, including one of the coldest decades in the past 2000 years. It was triggered by the 536/540 CE volcanic double event, creating the strongest decadal volcanic forcing in the last two millennia. During this period societal changes are recorded around the world, like the Great Migration period and the outbreak of the Justinian Plague. However, not a lot is known about the causal relationships between global cooling and societal change. Less is known also, about the impact of the large-scale atmospheric circulation on the regional climate, vegetation and society in Scandinavia after this volcanic double event. Here we aim to improve this understanding by combining global climate and regional growing-degree-day (GGD) modeling with climate proxies and archaeological records from Southeastern Norway.

We use PMIP4 past2k runs and the MPI-ESM ensemble simulation of the 6th/7th  century (520-680 CE), to analyze the atmospheric circulation, surface climate and vegetation changes as a response to the volcanic double event of 536/540 CE, over Scandinavia, specifically Southeastern Norway. Thereby we focus on the response of the major circulation patterns that influence the climate over Northern Europe: the positive and negative North Atlantic Oscillation, the Scandinavian blocking and the Atlantic ridge. The results of the GDD model, driven with the MPI-ESM model input, are compared to local pollen and climate records and archaeological data (e.g. grave density and settlement records) to shed more light on the local climate, vegetation and society impact. This comparison allows us to better understand how a natural hazard influenced local areas and climate records in Southeastern Norway. This study is part of the VIKINGS project, which focuses on the impact of volcanic eruptions on climate, environment and society in Norway/ Scandinavia.
Recovery processes in coastal wind farms
Authors: Gupta Tanvi , Baidya Roy Somnath
Published: March 2021

Wind turbines in a wind farm extract energy from the atmospheric flow and convert it into electricity, resulting in a localized momentum deficit in the wake that reduces energy availability for downwind turbines. Atmospheric momentum convergence from above, below, and sides into the wakes replenish the lost momentum, at least partially, so that turbines deep inside a wind farm can continue to function. In this study, we explore recovery processes in hypothetical offshore wind farms with particular emphasis on comparing the spatial patterns and magnitudes of horizontal and vertical recovery processes and understanding the role of mesoscale phenomena like sea breezes in momentum recovery in wind farms.

For this study, we use the Weather Research and Forecasting (WRF) model, a state-of-the-art mesoscale model equipped with a wind turbine parameterization, to simulate deep offshore and coastal wind farms with different wind turbine spacings under realistic initial and boundary conditions. The wind farms consist of 10000 turbines rated 3 MW spread over a 50 km x 50 km area. We conduct experiments with various background conditions, including low wind, high wind, and sea breeze cases identified using Borne’s method.

Results show that for deep offshore wind farms, power generation peaks at the upwind edge and monotonically decreases downwind into the interior due to cumulative wake effects of multiple rows of turbines. Vertical turbulent transport of momentum from aloft is the main contributor to recovery except in cases with strong background winds and high inter-turbine spacing where horizontal advective momentum transport can also contribute equally. Coastal wind farms behave similarly in the absence of sea-breezes.  However, under sea breeze conditions, the power production is high at the upwind edge and decreases thereafter but starts to increase again towards the downwind edge of the wind farm because of the sea breeze. The results further show that the contribution of horizontal (vertical) recovery in case of sea breeze conditions increases (decreases) to around 14% (86%) as compared to the non-sea breeze conditions where the horizontal (vertical) recovery contributes 9% (90%) to the momentum recovery in the wind farms. Vertical recovery shows a systematic dependence on wind farm density and wind speed. This relationship can be quantified using low-order empirical equations that can perhaps be used to develop parameterizations for replenishment in linear wake models. Overall, this study is likely to significantly advance our understanding of recovery processes in wind farms and wind farm-ABL interactions.
The effect of plastic leachates on respiration and foraging behaviour in hermit crabs
Authors: Scott Victoria F. , Hardege Jorg D. , Wollenberg Valero Katharina C.
Published: March 2021

Plastic production has soared since the 1950s, with the last decade seeing an  increase of 43% from 250Mt (million tonnes) in 2009 to 368Mt in 2019. Plastics and their associated chemical congeners (variants of chemical structures) which enter the environment further exacerbate pollution within already contaminated ecosystems. In this study, we investigated the effect of plastic leachate on the common littoral marine hermit crab Pagurus bernhardus,  a species  at great risk from potential adverse effects of microplastics. The effects of  plastic additives released into the environment via microplastic leaching, and of contaminants adsorbed and accumulated onto the surface of microplastics on marine organisms is understudied. This study sought to (I) investigate whether plastic leachate has an effect on the respiration rate of hermit crabs and, (II) investigate whether plastic leachate has an effect on the foraging behaviour of hermit crabs. We found that within repeated measures design hermit crabs exposed to plastic leachate had different levels of oxygen consumption when compared to their control; with there being an increase or decrease dependent on the leachate type. This is potentially problematic due to high concentrations of microplastics along coastlines which may lead to impaired filtration within crustaceans resulting in lethality and reduced food intake.
COSMIC project: COnvective-Scale Modelling In China
Authors: Schiemann Reinhard , Turner Andrew , Muetzelfeldt Mark , Volonté Ambrogio , Klingaman Nicholas , Vidale Pier Luigi
Published: March 2021

The East Asian Summer Monsoon (EASM) is an inherently multiscale phenomenon and new generations of global convection-permitting climate models hold great promise in representing such multiscale monsoon interactions.

Motivated by the recent availability of multi-year simulations with the HadGEM3 global climate model at about 10km resolution and different treatments of convection, the COSMIC project has delivered new process-based and decision-relevant metrics of diurnal and intraseasonal variability, and of the seasonal progression of the EASM: The newly developed BASMATI (Basin-Scale Model Assessment ToolkIt) tool is used for the scale-selective evaluation of the diurnal cycle of precipitation over Asian river basins and it is used to show that the phase of the diurnal cycle is much better represented in a convection-permitting setup of the global model, whereas mean precipitation biases in this setup are substantial and point to the need for further tuning of this new model version. Furthermore, a new automated method for identifying the EASM front has been developed and applied to ERA5 reanalysis data in a detailed description of the seasonal progression of the front. Lagrangian trajectory analysis is employed to identify air-mass convergence at the EASM front and highlights the specific conditions of converging warm and moist tropical and cooler subtropical air masses during the Mei Yu season. These results offer a new framework for studying the seasonal EASM progression and its representation in models. Finally, the different metrics developed in COSMIC are used for a statistical and dynamical characterisation of the exceptional precipitation and flooding affecting different parts of Asia, and the Yangtze river basin in particular, in June/July 2020.This poster provides a project overview and complements two separate conference papers discussing COSMIC results in greater detail.
Modeling underwater sound from future offshore wind farms southeast of Gran Canaria Island
Authors: Cubas Armas Melania , Hernández-Guerra Alonso , Delory Eric , Dellong David , Caínzos Verónica , Pérez-Hernández M. Dolores , Santana-Toscano Daniel , Arumí-Planas Cristina , Casanova-Masjoan María
Published: March 2021

The European Union aims to achieve carbon neutrality by 2050. Therefore, it is crucial to increase the use of renewable energy. One clean energy source is the wind, and during the last decades, several countries have developed wind farms, not only on land but also in the ocean. Most offshore wind farms have been installed in shallow waters; however, recently, open ocean offshore floating wind farms are being installed in deep waters due to stronger and steadier wind occurring in these areas. Thus, offshore wind turbines are a potential new source of underwater noise. Noise can propagate underwater having the potential to affect marine mammals and fish, among others. Floating wind turbines are known to reduce the installation and decommissioning noise in contrast to fixed-bottom turbines but, nevertheless, the noise produced by the operation of the turbines and the anchoring systems have been scarcely studied, and it is still unknown whether added noise could significantly affect behavior or even hearing capacity in the long term. In the framework of the JONAS European project we anticipate a regional use case with a future installation of a commercial offshore wind farm, to determine how noise would propagate in the region, from installation to operation, and potentially impact (or not) local fauna, focusing initially on mammal groups. In this study, we use the RAM model (Range-dependent acoustic model) which is a parabolic equation (PE) code that calculates the propagation of sound in the ocean using the split-step Padé solution. RAM needs information about the temperature and salinity in the water column to calculate sound speed profiles, as well as the bathymetry and a geo-acoustic model of the bottom. It returns the transmission loss depending on the depth and distance to the source. We have applied the RAM model to an area located in the southeast of Gran Canaria Island, where a plan for a floating wind farm is under consideration. Results and suggestions about the negative impact on marine mammals known to live in this location are presented.
Topographic characteristics of rainfall triggered landslides from a newly compiled set of inventories
Authors: Emberson Robert , Kirschbaum Dalia , Amatya Pukar , Tanyas Hakan , Marc Odin
Published: March 2021

Landslides triggered by rainfall or seismic activity are a significant source of loss of life and property damage in mountainous regions. In these settings, it is critical to plan development and infrastructure to avoid impact from landslides. To do so, it is necessary to have a clear understanding of the topographic characteristics of areas both where landslides are initially triggered but also the down-slope areas where debris and bedrock fragments are deposited. Recent research has investigated the characteristics of landslide locations triggered by seismic motion, providing guidelines about the most hazardous parts of a given landscape. In this contribution, we report on a set of analyses conducted on a large compilation of landslide inventories associated with major rainfall events around the world. This compilation includes a number of previously published inventories together with 6 newly mapped inventories of landslides created using high-resolution imagery and machine learning techniques. To our knowledge, together these form the most comprehensive compilation of rainfall triggered landslide inventories gathered to date.

We analyse a number of topographic characteristics associated with these landslides using the 30m resolution SRTM DEM, including local slope, average upstream slope, relief, topographic roughness, wetness index, and topographic position index. We analyse these parameters for both the scar of the landslide as well as the area of deposition. While there is significant dispersion across inventories for several of these parameters, there are consistent relationships between landslide likelihood and roughness, slope, and wetness index. Although the relationships identified with slope and roughness are consistent with prior work, the relationship between wetness index and landslide likelihood suggests that the calculation of wetness index from topography alone may not effectively represent the saturation state of the hillslopes. We anticipate that these findings could be useful for other regional and global landslide modelling studies and local calibration of landslide susceptibility assessment.
Evaluating convection-permitting ensemble forecasts of precipitation over Southeast Asia 
Authors: Ferrett Samantha , Frame Thomas , Methven John , Holloway Christopher , Webster Stuart , Stein Thorwald , Cafaro Carlo
Published: March 2021

Forecasting extreme rainfall in the tropics is a major challenge for numerical weather prediction. Convection-permitting (CP) models are intended to enable forecasts of high-impact weather events. Development and operation of these models in the tropics has only just been realised. This study describes and evaluates recently developed Met Office Unified Model CP ensemble forecasts of varying resolutions over three domains in Southeast Asia, covering Malaysia, Indonesia and the Philippines.

Fractions Skill Score is used to assess the spatial scale-dependence of skill in forecasts of precipitation during October 2018 - March 2019. CP forecasts are skilful for 3-hour precipitation accumulations at spatial scales greater than 200 km in all domains during the first day of forecasts but all ensembles have low spread relative to forecast skill. Skill decreases with lead time and is highly dependent on the diurnal cycle over Malaysia and Indonesia. Skill is largest during daytime when precipitation is over land and is constrained by orography, but is lower at night when precipitation is over the ocean. Comparisons of CP ensembles using 2.2, 4.5 and 8.8 km grid spacing and an 8.8km ensemble with parameterised convection are made to examine the role of resolution and convection parameterisation on forecast skill for the three domains.
The late-Holocene records of sediment provenance/weathering in the Wular Lake catchment, Northwest Himalaya
Authors: Ahmad Nafees , Singh Satinder Pal , Lone Aasif Mohmad
Published: March 2021

The Wular Lake (area ~189 km2) in the Kashmir Valley (area ~16,000 km2) is fed by the Jhelum River, which is a large Himalayan tributary of the Indus River. The lake catchment seasonally receives precipitation from tropical (Indian Summer Monsoon, ISM) and subtropical (Western Disturbances, WD) moisture sources. Thus, the lake sediments provide a unique opportunity to explore the high-resolution archive of the synoptic-scale weathering intensity and pattern in the Northwest Himalaya under past hydroclimatic conditions. In this study, radiogenic Sr and Nd isotope compositions and lithic fractions (sand, silt, and clay) have been determined on detrital phases of a 2.2 m long sediment core retrieved from the Wular Lake. The 14C-AMS chronology of this core presents the sedimentary records of the last 4.2 ka. The Sr and Nd isotope data indicate that the lake sediments deposited during the late-Holocene are mostly sourced from the Tethyan Himalaya rather than other major lithologies. The marginal downcore variations of ±1.5 εNd unit (except two anomalous datapoints with large uncertainties at 0.8 ka and 2.0 ka) reveal no major shifts in the sediment provenance during the late-Holocene. On the other hand, the significant downcore variations are observed in 87Sr/86Sr (>0.001–0.004) showing well-resolved periods of higher and lower values than the late-Holocene average. The 87Sr/86Sr data unbiased by the grain-size sorting and carbonate contents seem to indicate a temporal dominance of chemical and physical modes of silicate weathering in the Northwest Himalaya before and after ~2 ka, respectively. Interestingly, an abrupt shift in the 87Sr/86Sr data during the Little Ice Age (~0.4–0.1 ka) reveals a multi-decadal response of the silicate weathering intensity in synchrony with the northern hemisphere temperature anomaly.

 
Investigating the dynamics of thermally driven up-slope flows: analysis of data from measurements in the Inn Valley (Austria) and comparison with a simple model
Authors: Marchio Mattia , Farina Sofia , Zardi Dino
Published: March 2021

Diurnal wind systems typically develop in mountainous areas following the daytime heating and nighttime cooling of sloping surfaces. While down-slope winds have been extensively treated in the literature, up-slope winds have received much less attention. In particular, the physical mechanisms associated with the development of these winds, as well as the search for appropriate parameterization of turbulent fluxes of mass, momentum, and heat over slopes in numerical weather prediction models are still open research topics.

Here we present some preliminary results from the analysis of turbulence data (sonic wind speed, temperature, humidity, and turbulent fluxes) collected at two slope stations which are part of the i-Box initiative. The i-Box project (Rotach et al. 2017) aims at studying turbulent exchange processes in complex terrain areas. The experimental setup is composed of six stations disseminated in the surroundings of the alpine city of Innsbruck, in the Inn Valley. The two stations adopted for the present study are located at different points on the valley sidewalls, one with a slope angle of 27° (labelled NF27) and one with a slope angle of 10° (NF10). Both stations are located over slopes covered by alpine meadow and at an altitude of about 1000 m MSL (400 m above the valley floor). The station NF27 has two measurement points, 1.5 and 6.8 m AGL, while the station NF10 has one measurement point, at 6.2 m AGL.

The analysis shows that criteria proposed in the literature for the selection of valley-wind days may not apply for the identification of slope-wind days. Furthermore, from the analysis of second order moments, scaling relationships are derived for up-slope flow conditions. In addition, measurements representing the evolution of the up-slope flow structure from the early morning to the mid-afternoon are compared with an existing, simplified, analytical model, which provides the evolution of the vertical profiles of temperature and along-slope wind velocity as generated by a sinusoidal forcing representing the daily cycle of surface temperature. An improvement of the existing model, where the surface energy budget is considered as the boundary condition for the surface temperature, is also tested.
FFproc - an improved multivariate robust statistical data processing software for the estimation of MT transfer functions
Authors: Castro César Daniel , Hering Philip , Hogg Colin , Junge Andreas
Published: March 2021

The presence of cultural electromagnetic (EM) noise hampers the estimation of Magnetotelluric (MT) transfer functions and therefore distorts the imaging of subsurface resistivity structures. Many advanced processing approaches are available to improve the quality of EM signals. However, very few of them are capable to identify and remove time segments contaminated by correlated (anthropogenic) electromagnetic noise.

We present FFproc, an MT multi-site/multi-device robust remote reference processing code, that is implemented as a MATLAB© Graphical User Interface (GUI). The presented processing software builds on the eigenvalue decomposition method by Egbert (1997) and includes a robust estimation of the spectral density and the noise covariance matrices. The multivariate approach accounts for the statistical dependence between regression residuals related to the data channels at a single site (Advanced Noise Model, ANM) and therefore significantly reduces the impact from locally coherent noise signals.

The code also provides a semi-automatic algorithm, that analyzes the number of source-field processes in the multivariate data space. Here, an eigenvalue criterion, calculated for each single time window, favors time segments with high MT signal-to-noise ratio and simultaneously reduces the influence of regional coherent noise signals.

The modular software package allows the user to apply uni- or multi-variate processing routines to data collected with most of the common commercial data loggers (e.g. Metronix, Phoenix). The results can be exported to different data formats and can be analyzed and manipulated within the visualization environment of our MT software package - FFMT.

The processing algorithm is validated using simulated MT signals related to a 3-D resistivity benchmark model. Additionally, MT data from the Azores are used to compare the code to well established processing codes and to highlight its efficiency. See presentation “Three-Dimensional Interpretation of Broadband Magnetotelluric data at Fogo Volcano, Azores Islands” (Hogg et al.).