bluuebunny/crossref_metadata_2025 huggingface dataset:
Drip irrigation affects N2O emission differently depending on soil moisture status in an intensive vegetable production system
Authors: Xu Xiuchun , Wu Di , Zhang Wei , Ni Bang , Yang Xuan , Meng Fanqiao
Published: March 2021

Plastic-shed vegetable production system is becoming the main type of vegetable production in China, while excessive irrigation and fertilization input lead to significant N loss by leaching, runoff, and gaseous N. The current study established a field experiment to investigate the effects of drip irrigation and optimized fertilization on vegetable yield, water and fertilizer efficiencies and N2O emission in a typical intensive plastic-shed tomato production region of China. The treatments include CK (no fertilization, flood irrigation), FFP (farmers’ conventional fertilization, flood irrigation), OPT1 (80% of FFP fertilization, flood irrigation), OPT2 (80% of FFP fertilization, drip irrigation). N2O isotopocule deltas, including δ15Nbulk, δ18O and SP (the 15N site preference in N2O), have been used to investigate microbial pathways of N2O production under different treatments. Our results showed: i) optimized fertilization and drip irrigation significantly improved the fertilizer and water use efficiency without reducing tomato yield, ii) compared with flood irrigation, drip irrigation decreased soil WFPS and soil ammonium content, but increased soil nitrate content. When soil moisture was higher than 60%WFPS, drip irrigation led to a decrease of N2O emission with lower N2O SP signature observed than that of food irrigation, suggesting a reduction of denitrification derived N2O. In contrast, drip irrigation significantly increased N2O emission and N2O SP value when soil moisture status was lower than 55% WFPS, which may be due to the enhanced nitrification or fungal denitrification derived N2O.
Three-dimensional imaging of the Mérida Andes, Venezuela
Authors: Cruces José , Ritter Oliver , Weckmann Ute , Tietze Kristina , Meqbel Naser , Schmitz Michael
Published: March 2021

The Mérida Andes are a 100 km wide mountain chain that extends from the Colombian/Venezuelan border to the Caribbean coast. To the north and south, the Mérida Andes are bound by hydrocarbon-rich sedimentary basins. Uplift of the mountains started in the late Miocene due to oblique convergence of the Caribbean and South American tectonic plates and the north-eastwards expulsion of the North Andean Block (NAB). This tectonic interaction fostered major strike-slip fault systems, with associated high seismicity, and the partitioning of the North Andean Block into smaller tectonic units, whose interaction accelerated the uplift of the Mérida Andes since the Plio-Pleistocene.

We present the three-dimensional inversion results of broadband magnetotelluric (MT) data from 72 sites gathered along a 240 km long profile across the central part of the MA, the Maracaibo (MB), and Barinas-Apure (BAB) foreland basins. Directionality and dimensionality analyses suggested 3D structures for the MA section, with the induction vectors indicating off-profile structures, particularly at long periods. Since the distribution of sites predominantly along a single profile can have adverse effects on the outcome of the 3D inversion, we rigorously tested all model features for robustness and excluded artefacts.

One of the main findings is a deep connection (> 10km) between the most prominent faults of the MA, the Valera and Boconó fault systems, with a deep off-profile conductor to the east of our profile. We interpret this conductive structure as a detachment surface of the Trujillo Block, which is part of the NAB and whose expulsion to the NE significantly influences the present-day geodynamic evolution of western Venezuela. A conductive zone under the Maracaibo Basin correlates spatially with the location of a Bouguer low. Both geophysical anomalies may be caused by a SE tilt of the Maracaibo Triangular Block under the Mérida Andes, bound by the north-western thrust system which could reach depths of 30 km.
Experimental assessment of settling velocity of pristine and biofouled microplastics 
Authors: Jalon-Rojas Isabel , Romero-Ramirez Alicia , Fauquembergue Kelly , Rossignol Linda , Morin Benedicte , Cachot Jerome
Published: March 2021

Understanding and predicting the transport and fate of microplastics (MPs) in aquatic systems is a complex research challenge due to the simultaneous effect of different physical processes and the large variability in MPs dynamical properties. The dynamical behavior of MPs is further complicated by the development of biofilms and weathering processes. However, the effect of these processes on the dynamical properties of MPs is not fully understood. This study aims to evaluate the effect of the particle properties and biofilm on the settling velocity of microplastic sheets and fibers under laboratory conditions. The experiments focus on two types of particles (polyethylene sheets and polyester fibers), of nine sizes (between 1 and 5 mm), two degrees of biological colonization (new and aged during 3 months in the ocean) and three replicas of each type of particles. Density, size, and shape indices were first quantified. The settling velocity was then estimated by image analysis in a sedimentation column with salt- and freshwater. The dynamical behavior of the two types of particles was very different. Interestingly, the settling velocity of sheets increased with size up to a threshold in both salt- and freshwater, from which particle swinging and drag force increased, and settling velocity decreased. The effect of biofilm was also complex, increasing or decreasing the settling velocity of sheets as a result of the combined effect of the enhanced density and the biofilm distribution that influences the particle swinging. The settling velocity of fibers was independent of their length. Biofilms increased densities but their impact on settling velocity increase is less evident due to the high variability of this property for the same type of fiber. The relevance of theoretical drag models to predict the settling velocity of pristine and biofouled particles in salt- and freshwater will be also evaluated.
Petrolgy of the volcanic/subvolcanic members of the volcano-sedimentary Maden Complex in Eastern Turkey
Authors: Özdemir Yavuz , Mercan Çağrı , Oyan Vural , Atakul-Özdemir Ayşe , Güleç Nilgün , Özkan-Altıner Sevinç
Published: March 2021

Maden Complex exposed in Eastern Turkey, is a succession of volcano-sedimentary rocks and tectonically overlain by Bitlis Metamorphics and Cretaceous ophiolitic rocks. The succession includes shallow-water deposits and deep marine pelagic sediments intercalated with pillow lavas ranging from a few centimeters to ten meters in diameter. The planktonic foraminiferal assemblages from micritic limestones and zircon U-Pb ages from selected sedimentary rocks indicate the age of Late Ypresian - Early Lutetian. Plagioclase and  clinopyroxenes are the main mineral phases, olivine rarely found as altered phenocrysts. Clinopyroxenes are augite and diopside, and their compositions are ranging between Wo44-51, En27-43, Fe10-21. The anorthite contents of plagioclases are between 32- 67 % in unaltered grains. The crystallization temperatures and pressures obtained from clinopyroxene chemistry are ranging from 1126 to 1250oC and 3 to 8 Kbar, respectively. The majority of the volcanic/subvolcanic rocks are subalkaline-tholeiitic basalts however; a few andesitic and rhyolitic derivatives are also present. The whole – rock and  Sr-Nd-Pb isotope compositions reveal that the  basaltic rocks are originated from E-MORB like asthenospheric mantle source without a subduction component.
Investigating model nudging as a novel technique to isolate aerosol radiative adjustment mechanisms
Authors: Coleman Max , Collins William , Shine Keith , Bellouin Nicolas , O'Connor Fiona
Published: March 2021

We investigate a novel use of model nudging to interrogate radiative rapid adjustment mechanisms and their magnitudes in response to aerosol emission perturbations in an earth system model. The radiative effects of a forcing agent can be quantified using the effective radiative forcing (ERF). ERF is the sum of the instantaneous radiative forcing, and radiative adjustments – changes in the atmosphere’s state in response to the initial forcing agent that cause a further radiative forcing. Radiative adjustments are particularly important for aerosols, which affect clouds both via microphysical interactions and changes in circulation, stratification and convection. Understanding the different adjustment mechanisms and their contribution to the total ERF of different aerosol emissions is necessary to better understand how their ERF may change with future changes in anthropogenic aerosol emissions. In this work we investigate radiative adjustments resulting from changes in atmospheric temperature (and the resulting changes in stratification and convection) due to anthropogenic sulphate and black carbon aerosol forcing.

We have conducted multiple global atmosphere-only time-slice experiments using the UK Earth System Model (UKESM1). Each experiment has either control, black carbon perturbed, or sulphur dioxide perturbed emissions; and either no nudging, nudged horizontal winds (uv), or nudged horizontal winds and potential temperature (uvθ). The difference between nudged uvθ minus nudged uv simulations determines the atmospheric temperature related adjustments arising from the aerosol perturbation. We have also conducted repeats of each simulation, varying the nudging setup to test sensitivity to different nudging parameters.

We find that nudging horizontal winds affects the resulting ERF very little, whereas nudging potential temperature as well can cause a significant difference from the non-nudged experiments, primarily in the cloud radiative effect. However, this difference is sensitive to the strength of the nudging applied, for which we consider the most appropriate value.
Impacts of El Niño Southern Oscillation on flood risk and insured losses in New Zealand
Authors: Comola Francesco , Scudeler Carlotta , Satyam Saket , Nicotina Ludovico
Published: March 2021

Global warming is expected to enhance El Niño Southern Oscillation (ENSO) with potential impacts on rainfall and flood risk in numerous countries of the Asia-Pacific region. Modeling studies have suggested that positive and negative ENSO phases may intensify by as much as 25% under extreme climate projections. However, the influence of ENSO variability on flood risk in Asia-Pacific countries is still largely unexplored. Here, we aim to shed light into the link between ENSO, flood risk, and insured losses in New Zealand by combining rainfall observations and state-of-the-art flood risk models. We draw on 60 years of daily precipitation measurements to quantify the statistical correlations between the rainfall principal components and the ENSO historical time series. This allows us to generate 50,000 years of stochastic daily rainfall maps correlated with a long-term, synthetic ENSO time series. The stochastic precipitation maps are then used to drive streamflow and flood simulations at 20 m spatial resolution. Our results indicate that positive and negative ENSO phases increase the flood risk in different regions of New Zealand, and that extreme ENSO events tend to cause more severe flood events. We finally investigate the potential differences in economic losses during positive and negative ENSO phases by combining modeled flood footprints with exposure and vulnerability data. These results may guide the implementation of effective adaptation and mitigation strategies against the increasing risk of flood events in warming climate.
Inventory of aerosol episodes in Ny-Ålesund (Svalbard) in the period 2017-2020 by sun photometry
Authors: Herrero Sara , Mateos David , Toledano Carlos , Román Roberto , González Ramiro , Ritter Chistopher , Antuña-Sanchez Juan Carlos , González-Fernández Daniel , Calle Abel , Cachorro Victoria E. , de Frutos Ángel M.
Published: March 2021

Atmospheric aerosols are an important forcing agent in the estimation of radiative budget, being the Arctic an area of special weakness. The Group of Atmospheric Optics, University of Valladolid and the Alfred Wegener Institute for Polar and Marine Research, installed in 2017 a CE-318T Sun-sky-Moon  photometer (Cimel Electronique S.A.S) in the Arctic station Ny-Ålesund (79ºN, 12ºE). This study presents an inventory of all high-turbidity aerosol episodes recorded in the period 2017-2020 (data of level 1.5-validated from AERONET). This inventory is based on the separate analysis of coarse and fine mode aerosol optical depth. Aerosol episodes are attributed to coarse, fine or mixture of aerosols. Complementary information provided by HYSPLIT air mass back trajectories, MODIS images, forecast aerosol models, CALIOP/CALIPSO satellite data, and other collocated instruments on the station are also used. Special focus is given to long-range transport of aerosols from big forest fires in Canada, United States and Russia.
Flood monitoring using passive microwave remote sensing in the Senegal River, Western Mali
Authors: el Khinifri Soufiane , van den Homberg Marc , Kramer Tessa , Beckers Joost , Schellekens Jaap , Kettner Albert , Mounkaila Issaka Abdoul Aziz , Maigary Issoufou , Sarr Mamadou Adama , Reiche Johannes
Published: March 2021

Water supports life, however it does come with hazards. Floods area amongst the most impactful environmental disasters. Accurate flood forecasting and early warning are critical for disaster risk management. Detecting and forecasting floods at an early stage is certainly relevant for Mali, hence crucial in order to prevent a hazard from turning into a disaster. Remotely sensed river monitoring can be an effective, systematic and time-efficient technique to detect and forecast extreme floods. Conventional flood forecasting systems require extensive data inputs and software to model floods. Moreover, most models rely on discharge data, which is not always available and is less accurate in a overbank flow situations. There is a need for an alternative method which detects riverine inundation, while making use of the available state-of-the-art.

This research investigates the use of passive microwave remote sensing with different spatial resolutions for the detection and forecasting of flooding. Brightness temperatures from two different downscaled spatial resolutions  (1 x 1 km and 10 x 10 km) are extracted from passive microwave remote sensing sensors and are converted into discharge estimators: a dry CM ratio and a wet CMc ratio. Surface water has a low emission, thus let the CM ratio increase as the surface water percentage in the pixel increases. Sharp increases are observed for over-bank flow conditions.

Overall, we compared the passive microwave remote sensing model results of the different spatial resolutions to the results of a conventional global runoff model GloFAS. The passive microwave remote sensing model does not require extensive input data when used as an Early Warning System (EWS), as many smaller-scale EWS do, we suggest that when improved, the passive microwave remote sensing method is implemented as part of an integrative EWS solution, including a passive microwave remote sensing model and various other models. This would allow for early warnings in data-scarce regions and at a variety of lead times. In order for this to be effective, we suggest that more research be done on correctly setting the trigger threshold, and into the potential spatial interpretation of CMc.
Drought dynamics and variability over Bundelkhand region of central India: Past, Present and Future
Authors: Saharwardi Md Saquib , Dubey Aditya Kumar , Kumar Pankaj , Sein Dmitry V.
Published: March 2021

In the present study, an evaluation of the past, present, and future variability of droughts in the Bundelkhand region of Central India are analyzed. Bundelkhand is a severe drought-prone region with intense water stress, where in the last five years four were drought. Therefore, understanding the drivers of drought over the region and its future projection is quite crucial for regional water management. The assessment has been made by analyzing the observational dataset from 1951-2018 to understand the regional drought dynamics. The future projection is made using a multi-model ensemble from a regional climate model over the CORDEX South-Asia domain under the highest emission scenario. The Standardized Precipitation Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI) indices are used to understand present drought and its future projection. In addition to this, drought driving parameters like precipitation, temperature, sea-surface temperature wind circulation has been assessed to understand the regional drought dynamics. The composite analysis of drought indicates that the moisture-laden low-level jet from the Arabian Sea branch generally weakened compared to Bay of Bengal branch for monsoon season. Teleconnections of drought over Bundelkhand region shows that nearly half of the droughts are linked to El-Nino events that have become stronger in recent past. The model result reveals that regional climate variability is reasonably captured over the region. In addition, we found increasing drought frequency since the beginning of the 21st century. The detailed results from the analysis will be shown briefly in the general assembly.

Acknowledgement: This work is jointly supported by the Department of Science and Technology (DST), Govt. of India, grant number DST/INT/RUS/RSF/P-33/G and the Russian Science Foundation (Project No.: 19-47-02015). The first author is also thankful to the Department of Science and Technology (DST), Govt. of India for providing DST INSPIRE fellowship (Grant No. IF160281).
Balancing permanent and forecast-based action to lessen wind-induced building damage in the Philippines.
Authors: Vonk Demi , van den Homberg Marc , Kingma Nanette , Alkema Dinand , Teklesadik Aklilu , Riquet Damien , van Aalst Maarten
Published: March 2021

With a global paradigm shift from post-disaster response aid to anticipatory action, the question on how anticipatory action relates to long-term climate adaptation and often government-led actions towards permanent disaster prevention becomes more relevant. With rising disaster risk, a framework that decision-makers can use to select between preventive and preparedness risk reduction efforts would be most useful. A model originally developed to compare permanent interventions to forecast-based action for floods was applied to wind-induced building damage due to tropical cyclones, focusing on a case study from the Philippines. We made use of a typhoon forecasting model based on the ensemble forecast from EMCWF, and modeled the wind footprint to estimate the wind speed in the case study area. A threshold was defined, similar to how it is done in actual operations by the Philippine Red Cross. If the forecasted typhoon exceeds a pre-set threshold in terms of wind speed, action to strengthen light-weight wooden houses with a Shelter Strengthening Kit (SSK) is taken. SSKs temporarily make these houses more resistant to withstand extreme winds, thereby reducing the impacts. This short term action is compared to a scenario in which lightweight wooden houses are permanently upgraded. Results give actors in humanitarian response, anticipatory action as well as permanent disaster prevention insight into which variables affect this balance. and help policymakers to allocate their scarce budgets in a cost-effective way. The framework, although developed for the Philippines, can also be replicated in other cyclone-prone countries. 
Sea surface salinity dipole mode in the tropical Indian Ocean and its relationship with Indo-Pacific climate  
Authors: Zhang Yuhong , Du Yan , Sun Qiwei
Published: March 2021

An atmospheric channel with the monsoon circulation system and the Walker circulation and an ocean channel with Indonesian through-flow, connect the tropical Indian Ocean and the Pacific, which strongly modulate the Indo-Pacific climate change on different time scales. The atmospheric channel transports 0.35 Sv water vapor from the Indian Ocean to the Pacific on the mean state, while the Indonesia throughflow transports ~15 Sv of freshwater from the western Pacific to the Indian Ocean. These two aspects of freshwater transportation play an important role in maintaining the salinity balance in the tropical Indian Ocean (TIO). On the interannual-decadal time scale, a sea surface salinity dipole mode has been revealed in the tropical Indian Ocean (S-IOD) with salinity anomalies in the central equator and the southeastern TIO is opposite, corresponding to significant wind anomaly along the equator and precipitation and thermocline depth anomalies in the southeastern TIO. The ocean advection forced by wind anomalies along the equator and precipitation and thermocline depth anomalies in the southeastern TIO dominating the SSS variations of the S-IOD, respectively. The modulation of the Indo-Pacific Walker Circulation and its related ocean wave processes transported from the western Pacific through the waveguide in the Indonesian Seas are main factors for the development of S-IOD and its variability, which is forced by the Interdecadal Pacific Oscillation (IPO). Further analyses indicate that the long-term trend of SSS in the global ocean with the salty regions getting saltier and fresh regions getting fresher is modulated by the internal variability associated with the IPO, with the most significant regions in the western tropical Pacific and the southeastern Indian Ocean. Specifically, the IPO leads to a ~40% offset of SSS radiative-forced trend in the western tropical Pacific and ~170% enhancement of the trend in the southeastern Indian Ocean since the mid-20th century.      
Is heat a hot topic? – Exploring risk perception, risk communication, and adaptation to heat stress with a household survey
Authors: Heidenreich Anna , Thieken Annegret
Published: March 2021

Due to the ongoing climate change heat waves increase in numbers and in duration in Germany. Extreme heat poses a massive health threat, in particular if no or maladaptive behaviour is shown.

In summer and autumn 2019, we conducted a household survey on personal perceptions of heat stress. In total, 1.417 people from three different German cities participated via telephone or online. Based on the Protective Action Decision Model (PADM), which we adapted to heat hazard, we analysed links between risk perception, different context factors, perceptions of social stakeholders, different heat warning formats, and adaptation behaviour/intention. For statistical evaluation, correlation analyses, ANOVA, and regression analyses were executed.

People with higher climate change beliefs were more aware about heat warnings, reported higher negative impacts of heat stress on their health and everyday life and esteemed stakeholders from the health, care and social sector as responsible to carry out protection measures against heat. ANOVAs showed that the presentation of action recommendations along with official heat warnings leads to higher adaptation intentions. Correlation and regression analyses reveal connections between climate change beliefs and heat risk perceptions, other context factors and adaptation. PADM proves to be a useful framework for heat risk perceptions and behaviour and can be recommended to risk managers. To foster risk awareness and private adaptation measures further, tailored risk communication strategies need to be developed and evaluated.
Constraints on continental subduction in the Dora-Maira massif from rutile and titanite U-Pb geochronology 
Authors: Bonnet Guillaume , Chopin Christian , Kylander-Clark Andrew , Hacker Bradley
Published: March 2021

The Dora-Maira massif (Western Alps) is among the most studied subducted continental terranes in the world. It consists of a tectonic stack of <km-thick units metamorphosed at different grades, from blueschist to Ultra-High-Pressure (UHP) eclogite. While the UHP unit has been extensively studied, little is known about the chronology of subduction and exhumation of other units.

We here present new petrological observations and U-Pb geochronology on rutile and titanite to constrain the prograde, peak and retrograde evolution of distinct units.

 Rutile U-Pb geochronology on peak UHP assemblages is compared to existing results and is examined in light of closure temperatures for Pb diffusion. The results confirm peak metamorphism at ~35 Ma and fast cooling rates. This method is then applied to colder units (where closure temperatures are higher than peak temperatures, as shown by the preservation of the Permian age of pre-Alpine rutiles) and yields peak metamorphic ages of the different units between 39 and 32 Ma.

Rutile and titanite U-Pb geochronology help constrain the age of pervasive retrogression in the Dora Maira massif which is likely synchronous with the early exhumation of the lowermost continental unit and the transition from subduction to collision at 32-31 Ma.

We finally examine the possibility and potential consequences of melt circulation in the UHP unit during subduction.
The Life-Cycle of Cloud and Precipitation Microphysics in Radar Observation and Numerical Model
Authors: Möller Gregor , Ewald Florian , Groß Silke , Hagen Martin , Knote Christoph , Mayer Bernhard , Tetoni Eleni , Zinner Tobias
Published: March 2021

The representation of microphysical processes in numerical weather prediction models remains a main source of uncertainty. To tackle this issue, we exploit the synergy of two polarimetric radars to provide novel observations of model microphysics parameterizations. In the framework of the IcePolCKa project (Investigation of the initiation of Convection and the Evolution of Precipitationusing simulatiOns and poLarimetric radar observations at C- and Ka-band) we use these observations to study the initiation of convection as well as the evolution of precipitation. At a distance of 23 km between the C-band PoldiRad radar of the German Aerospace Center (DLR) in Oberpfaffenhofen and the Ka-band Mira35 radar of the Ludwig-Maximilians-University of Munich (LMU), the two radar systems allow targeted observations and coordinated scan patterns. A second C-band radar located in Isen and operated by the German Weather Service (DWD) provides area coverage and larger spatial context. By tracking the precipitation movement, the dual-frequency and polarimetric radar observations allow us to characterize important microphysical parameters, such as predominant hydrometeor class or conversion rates between these classes over a significant fraction of the life time of a convective cell. A WRF (Weather Research and Forecasting Model) simulation setup has been established including a Europe-, a nested Germany- and a nested Munich- domain. The Munich domain covers the overlap area of our two radars Mira35 and Poldirad with a horizontal resolution of 400 m. For each of our measurement days we conduct a WRF hindcast simulation with differing microphysics schemes. To allow for a comparison between model world and observation space, we make use of the radar forward-simulator CR-SIM. The measurements so far include 240 coordinated scans of 36 different convective cells over 10 measurement days between end of April and mid July 2019 as well as 40 days of general dual-frequency volume scans between mid April and early October 2020. The performance of each microphysics scheme is analyzed through a comparison to our radar measurements on a statistical basis over all our measurements.
Intensification of future low-flow events in relation to projected changes in large-scale climate drivers due to climate change
Authors: Goswami Pallavi , Mondal Arpita , Rüdiger Christoph , Peterson Tim J.
Published: March 2021

Large-scale climate processes such as the El Nino Southern Oscillation (ENSO), Indian Ocean Dipole (IOD) and Southern Annular Mode (SAM) influence the hydro-climatology of Southeast Australia (SEA). In the present study, we show that low-flow events in many catchments in SEA are significantly influenced by variability in these climate drivers. Extreme value distributions and Generalised Linear Models (GLMs) are used here to model low-flow characteristics such as intensity, duration and frequency with respect to these climate drivers. Further, we study how the future projections of ENSO, IOD and SAM are likely to evolve under climate change by examining the projected values of their representative indices and how they will impact low-flow events in the region. It is found that the future dry phases of these climate drivers are likely to be more dry than those in the historic period. This in turn is expected to lead to intensification of low-flow events in the future, resulting in lower availability of fresh water during occurrences of the dry phases of these climate drivers. Thus, climate change in the future is expected to significantly influence future low-flow events in the region thereby making it even more crucial for water managers to adequately manage and ensure water availability.

Keywords: low-flows, ENSO, IOD, SAM, Extreme Value Theory, Generalised Linear Models, Southeast Australia, CMIP5, RCP8.5.
Geology of non-plate tectonic regimes: detrital zircon age records and beyond
Authors: Zuo Jiawei , Webb Alexander , McKenzie Ryan , Johnson Tim , Kirkland Christopher
Published: March 2021

Studying the early evolution of terrestrial bodies in our solar systems is challenging. In part, this is because preserved early records are poorly preserved (e.g., Hadean rocks on Earth) and/or hard to access (e.g., rocks on Mars and Venus). Another commonly underappreciated factor is that the testable predictions for the diverse proposed tectonic regimes for early terrestrial bodies are currently underexplored. A better understanding of the consequences of different tectonic regimes can enhance our ability to constrain the early evolution of terrestrial bodies, including the timing of plate tectonic initiation on Earth. In this contribution, we use the example of detrital zircon geochronology to show how first-order predictions for various tectonic modes can be made based on their basic kinematics via relatively simple tools, and how these predictions can provide 1) abundant additional interpretive probabilities for common datasets, and 2) potentially significant implications for the tectonics of early Earth. Using simple Monte Carlo methods with MATLAB codes, we simulated detrital zircon age predictions for basins predicted by heat-pipe tectonics and cold stagnant-lid tectonics based on their relevant numerical models and/or evolutionary diagrams. We show that the first-order predictions for detrital zircon age patterns can be generated by focusing on simulating key mechanisms (e.g., volcanic resurfacing) that control the detrital zircon age characteristics of these two tectonic regimes. Such simulations can be done by simple codes based on a few parameters reflecting basic kinematics of relevant tectonic regimes. We find that differences between new detrital zircon age predictions and those of plate tectonic settings permit better tectonic discrimination via a globally compiled Archean detrital zircon age dataset. The results indicate a transition from heat-pipe tectonics to plate tectonics within the ca. 3.4-3.2 Ga period. Beyond detrital zircon age patterns, we also summarized other possible categories of first-order predictions for non-plate tectonic models, including metamorphic patterns, structural patterns, and crustal thicknesses. Relevant predictions of these categories are variably explored and can potentially be easily modeled or conceptualized via geological tools.
How to calibrate a solar radiometer
Authors: Finsterle Wolfgang , Haberreiter Margit , Montillet Jean-Philippe
Published: March 2021

Solar radiometers are deployed in many locations on the ground and in space. The radiometers in space are measuring the solar energy input into the Earth system per time and unit area, also known as the Total Solar Irradiance (TSI). TSI radiometers are also used to calibrate Earth Observation instruments and to measure the Total Outgoing Radiation (TOR) at the top of the atmosphere, which is a key component in the Earth Radiation Budget (ERB). Ground-based solar radiometers measure the local irradiance levels, which are used for monitoring of atmospheric properties and solar energy applications.

Traceability of the radiation measurements to SI units is crucial in all of these applications. However, calibrating and characterising a solar radiometer is a technically challenging task. Depending on the requirements for a specific application, different calibration concepts can be employed in the calibration and characterization process.

We will present the currently available calibration concepts, their advantages and disadvantages, and put special focus on recent technical developments, such as the cryogenic standard radiometers for solar irradiance on the ground and in space.
Horizontal and vertical fluid flows as a key control of ore deposition at the basement/cover unconformity: insight from drone imagery of the Vendée coast, France
Authors: Bouat Loïc , Strzerzynski Pierre , Mourgues Régis , Branquet Yannick
Published: March 2021

Basement/cover interfaces are important transfer zones for hydrothermal fluids responsible for ore deposition, such as U and Pb-Zn deposits. Unconformities are peculiarly mixing zone where basement-derived fluids encounter sedimentary- and/or meteoric-derived fluids; leading to precipitation of these ores. Fluids are channelized by permeability contrast, i.e. impermeable barriers, until being trapped in porous units, i.e. intrinsic porosity and/or secondary porosity (dissolution and karstification process). In this configuration fracturing channelize the fluid flow by breaking impermeable barriers allowing external fluids to enter and react with the rocks (precipitation and/or dissolution). In this way, structural studies are crucial to highlight the fracture network and the potential of geological units to be good reservoirs.

In France, many occurrences of sediment-hosted deposits are known in Mesozoic basins (i.e. Aquitaine and Paris Basin) especially above the Variscan basement (Morvan district, SW Massif Central district, Poitou High district). The Vendée coast deposit (South Armorican Massif, France) is known for two Pb-Zn(-Ag) occurrences located in Liassic sediments overlying the Variscan basement. Previous works show that, during the Upper Jurassic extensional event (NNE-SSW horizontal stretching), the ore deposition results from the mixing of two different fluids: (1) low temperature brines following a horizontal path from evaporite to basin borders within Liassic sediments along the unconformity, (2) a high temperature and low salinity fluid rising up through the basement from several kilometres depth by a probable vertical pathway.

However, the permeability architecture leading to such mixing remains poorly constrained. The Vendée ore deposits present favourable outcrop conditions to study the structural control of the fluid plumbing system along the basement/cover unconformity. Structural studies assisted by drone imagery coupled with the characterization of the alteration-mineralization pattern show that:

(1) Horizontal path for basin brines is controlled by the impermeable barrier of the Toarcien layer overlying Liassic hosting karsts.

(2) Vertical path of basement-derived fluids is enhanced by new faults and inherited fractures, respectively generated and reopened by the Jurassic extension.

(3) Relative abundance of faults and veins in the Liassic sedimentary cover and the basement is consistent with a mechanical decoupling in a context of fluid overpressure.
A synthetic study of tidal analysis for satellite altimeter in shallow water
Authors: Guarneri Henrique , Verlaan Martin , Slobbe Cornelis , Klees Roland , Bij de Vaate Inger , Afrasteh Yosra , Keyzer Lennart , Pietrzak Julie , Snellen Mirjam , Zijl Firmijn
Published: March 2021

Tidal constituents obtained from satellite radar altimeter derived water levels are widely used for ocean-related applications. However, in coastal waters, the tidal signal's complexity increases due to non-linear interactions between tidal constituents and other dynamics such as surge, giving rise to higher harmonics. A higher number of constituents increases the chance of pairwise frequency proximity, which creates retrieval time constraints using the typical series' length requirement criterion (Rayleigh criterion). Another issue is that with the lower observation frequency of altimeters, aliasing frequencies have to be considered. These lead to more challenges in shallow waters than its ocean counterpart since it is currently unfeasible to meet the series's time length requirements. In tidal analysis software, the Rayleigh criterion is often defined as fixed default harmonic selection condition. Therefore, many potentially important harmonics are left-out of the satellite radar altimeter based tidal analysis in shallow-waters, limiting derived usage.

To gain more insight into the accuracy of altimeter-derived tidal analysis, we extended the tidal analysis to include a more realistic correlation model for the surge. This model is implemented as a Kalman filter allowing us to obtain information about how the estimates' accuracy improves as more data becomes available. The improved correlation model aims to obtain realistic accuracy estimates for various strategies using synthetic data, i.e., before applying the method. An analysis of the condition number of the covariance information matrix was carried out alongside a twin experiment with simulated data. We demonstrated that the Rayleigh criterion is associated with the condition number of the information matrix and the effects of noise in the retrieval times. It shows that the accumulation of information is constant and proportional to the decrease of uncertainty. Depending on the amount of certainty one is after, the Rayleigh criterion is dispensable. Careful consideration has to be made for the signal to noise ratio of retrievals, especially when a constituent's amplitude is smaller than the variability introduced by noise, in our case, non-tidal variability. Overall, the analysis brings benefits on-top of traditional tidal analysis because it allows testing theoretical retrieval times and tidal analysis accuracy with multiple pairwise proximity issues and aliasing considerations. It also gives a straightforward way of analyzing the retrieval characteristics of semi-regular and irregular observation periods.
Changes in the thermal energy and the diffuse 3He and 4He degassing prior to the 2014-2015 eruption of Pico do Fogo volcano, Cape Verde
Authors: Alonso Mar , Pérez Nemesio M. , Padrón Eleazar , Hernández Pedro A. , Melián Gladys V. , Sumino Hirochika , Padilla Germán D. , Barrancos José , Rodríguez Fátima , Dionis Samara , Asensio-Ramos María , Amonte Cecilia , Silva Sonia , Pereira José Manuel
Published: March 2021

Cape Verde archipelago is a cluster of several volcanic islands arranged in a westward opening horseshoe shape located in the Atlantic Ocean, between 550 and 800 km-west of the coast of Senegal (Africa). Fogo Island is located in the southwest of the archipelago, and as main feature is a 9-km-north to south wide collapse caldera opened toward the east, within Pico do Fogo volcano rises 2,829 m.a.s.l. Pico do Fogo crater has an area of 0.142 km2 and its characterized by a fumarolic field composed by low and moderate temperature fumaroles, with temperatures around 95ºC and reaching 400ºC respectively. The last eruption of Fogo volcanic system took place between November 2014 and February 2015, when four new eruptive vents were formed, and destroyed partially the villages of Portela and Bangaeira (Silva et. al., 2015) forcing the evacuation of 1,300 inhabitants. In this work we present the temporal evolution of 3He/4He isotopic ratio, 3He and 4He emission and thermal energy released data measured from March 2007 to November 2018 in the crater of Pico do Fogo. In all the studied temporal evolutions, we can observe two main increases in the above parameters, the first in early 2010, suggesting a magmatic intrusion, and the second several months before the eruption onset. We have also observed that changes in the 3He emission might be accompanied by a significant increase in thermal output if the system is in an eruptive cycle. Our results confirm 3He emission studies are highly reliable indicator of imminent volcanic eruption and constitute a powerful tool to monitor the activity of volcanic areas around the world.

Silva et al., (2015), Geophysical Research Abstracts Vol. 17, EGU2015-13378, EGU General Assembly.
Impact of chaotic mixing on reactive transport: experiment in porous media at high Pe and Da
Authors: Sanquer Hugo , Heyman Joris , Le Borgne Tanguy , Hanna Khalil
Published: March 2021

Solute transport in porous media plays a key role in a range of chemical and biological processes, including contaminant degradation, precipitation, dissolution and microbiological dynamics. Increasing evidences have shown that the conventional complete mixing assumption at the pore scale can lead to a strong overestimation of reaction rates. Recent 3D imaging experiments of mixing in porous media suggest that these pore scale chemical gradients may be sustained by chaotic mixing dynamics. However, the consequences of such chaotic mixing on reactive processes are unknown.

In this work, we use reactive transport experiments coupled to 3D imaging to investigate the impact of micro-scale chaotic flows on mixing-limited reactions in the fluid phase.  We use optical index matching and laser-induced fluorescence to characterize the pore scale distribution of reactive product concentration for a range of Peclet and Damkhöler numbers. We use these measurements to develop a reactive lamellar theory that quantifies the impact of pore scale chemical gradients induced by chaotic mixing on effective reaction rates. These results provide new perspectives for upscaling reactive transport processes in porous media.
Permanent, seasonal, and episodic seismic sources around Vatnajökull, Iceland from the analyses of correlograms
Authors: Nowé Sylvain , Lecocq Thomas , Caudron Corentin , Jónsdóttir Kristín , Pattyn Frank
Published: March 2021

This study aims at characterizing different seismic sources in the region of the Vatnajökull glacier using seismic interferometry. Vatnajökull is the largest Icelandic icecap, covering 4active volcanic systems. The seismic context is therefore very complex with glacial and volcanic events occurring simultaneously and a classification between the two can become cumbersome. 

We used seismic interferometry or cross-correlation of seismic noise on seismic data from 2011 to 2019). Being based on continuous records, this passive monitoring method is not relying on earthquakes to locate seismic sources. We computed the cross-correlation functions between every pair of seismic stations using MSNoise for different frequency bands, from 0.5 to 8 Hz. The first step towards the location of seismic sources was to calculate the propagation velocities for each frequency range. The total range of velocities is between 1.39 km/s and 3.92 km/s. Then, we used two different location methods based on the calculated propagation velocities. The first method is based on hyperbole’s geometry and provides the location of seismic sources as the intersection between several hyperboles, while the second one, the Ballmer’s method (Ballmer et al. 2013), is based on the calculation of theoretical differential times and provides location probabilities for the seismic sources. We located and characterized persistent oceanic seismic noise located along the southern shoreline of Iceland potentially associated with waves activity and geometry of the shore, as well as a seasonal glacial tremor around outlet glaciers in the west part of the Vatnajökull icecap, potentially linked to glacial processes inside the glacier or in the glacial rivers. The uncertainty of a few kilometers is observed. Some limitations exist for these methods. For example, The Ballmer’s method (Ballmer et al. 2013) is reliable for seismic sources inside the seismic network but can only give an azimuthal direction for seismic sources located outside of it. When using hyperboles, slightly different propagation velocities between pairs of stations can affect the precision of the intersection. Therefore, the association of the two methods is important to diminish the impact of these limitations. 

These results provide a better understanding of the seismic background of this region and will be compared and validated with other localization methods in the future.
Experiments and simulations on extreme waves near reflective beaches
Authors: Chabchoub Amin , He Yuchen , Vila-Concejo Ana , Babanin Alexander
Published: March 2021

Extreme waves events, also referred to as rogue waves, are known to appear in deep-water conditions as well as nearshore zones. The formation of large-amplitude waves in offshore areas has been well-documented and intensively studied in the last decades. On the other hand, wave processes near the coastlines are known to be dominated by wave reflections, which have a significant influence on the incident waves. This experimental study aims to improve understanding of rogue wave formation mechanisms and statistics when waves reflections are at play. To tackle this, several JONSWAP wave trains have been generated in a water wave flume wave while varying the artificial beach inclination to allow several wave reflection conditions. The data collected near the beach confirms an increased formation of extreme waves and attests the decrease of kurtosis with the increase of the beach inclination. Numerical simulations, based on weakly nonlinear wave evolution models, show a very good agreement with the laboratory experiments. 
Advective pathways of nutrients and key ecological substances in the Arctic
Authors: Vredenborg Myriel , Rabe Benjamin , Torres-Valdès Sinhue
Published: March 2021

The Arctic Ocean is undergoing remarkable environmental changes due to global warming. The rise in the Arctic near-surface air temperature during the past decades is more than twice as high as the global average, a phenomenon known as the “Arctic Amplification”. As a consequence the Arctic summer sea ice extent has decreased by more than 40 % in recent decades, and moreover a year-round sea ice loss in extent and thickness was recorded. By opening up of large areas formerly covered by sea ice, the exchange of heat, moisture and momentum between the ocean and the atmosphere intensified. This resulted in changes in the ocean circulation and the water masses impacting the marine ecosystem. We investigate these changes by using a large set of hydrographic and biogeochemical data of the entire Arctic Ocean. To better quantify the current changes in the Arctic ecosystem we will compare our observational data analysis with high-resolution biogeochemical atmosphere-ice-ocean model simulations.