bluuebunny/crossref_metadata_2025 huggingface dataset:
Fault Damage Scaling: Insights from field data in carbonate rocks and analogue modelling
Authors: Mayolle Sylvain , Soliva Roger , Dominguez Stephane , Caniven Yannick , Wibberley Christopher , Ballas Gregory
Published: March 2020

Fault damage zones present a renewal of interest to better understand stress perturbations around faults, earthquake’s ground motions and fluid flow in the upper crust. Although numerous studies provide significant amounts of data from a broad variety of rocks, the processes controlling fault damage development are not clearly understood and scaling properties in carbonate rocks remain poorly studied. D-T (displacement - DZ thickness) data compilations show strong scattering and are acquired using different methods and at different places along the faults (including tip, wall, link, or inner and outer damages), therefore rendering difficult a proper definition of the scaling relationship.

 

First, we analyse fault/fracture systems at the outcrop and map scale and define displacement - thickness (D-T) scaling of fault damage zones using scanlines, in carbonate rocks in France and Spain. We determine fault displacement and damage zone thickness perpendicular to fault planes and far from fault tips for 12 selected faults in four study sites. The data show a logarithmic decrease of fracture frequency from the fault cores. This decrease is characterized by local frequency peaks corresponding to variably-linked secondary fault segments and abandoned tips within the fault damage zone. D-T data comprised between 0 and 100 m of net fault displacement show a nearly linear scaling with very little scattering. Including two additional data for D > 100 m, the best fit corresponds better to a power law. The linear scaling is explained by well-known processes of fault growth such as stress perturbations around faults and fault segment linkage. The non-linear trend shown by the largest faults suggests that at this scale the faults become restricted at their lower tips by the base of the brittle crust.

 

Secondly, we analyse fault damage growth using analogue modelling of normal faults in a sand box. The model is composed by a 5 cm thick layer of dry sand deposited above a 2 cm thick ductile “kinetic sand” (sand and silicone) layer. The experiment is analysed in cross-section using image correlation allowing to calculate the velocity field and strain tensor over the fault zones including their damage pattern. Fault damage thickness obtained using the strain field appears to grow linearly with respect to shear displacement when the fault is contained into the dry sand layer. When the fault lower tip reaches the kinetic sand, fault damage begins to growth non-linearly with shear displacement, revealing that the brittle layer thickness is the main parameter governing the non-linear scaling.

 

 
Estimation of VGOS Station Coordinates
Authors: Mikschi Markus , Böhm Johannes , Schartner Matthias
Published: March 2020

With the number of available VGOS (VLBI Global Observing System) sessions rising, precise coordinates for the participating stations become more important. While station coordinates can be estimated during the VLBI (Very Long Baseline Interferometry) analysis, the definition of the geodetic datum via Not-Net-Rotation (NNR) and No-Net-Translation (NNT) conditions requires at least three participating stations with precise a priori coordinates. The VGOS station network is currently independent of the International Terrestrial Reference Frame (ITRF), as none of the stations have participated in a solution for the ITRF in VGOS mode. By estimating the VGOS station coordinates based on ITRF coordinates, originating from local surveying and solutions of S/X observations by now converted stations, a link to the ITRF can be established. First a global solution, which is the combination of individual sessions on the normal equation level, of the five VGOS CONT17 sessions was calculated. The datum was defined by WESTFORD, ISHIOKA and WETTZ13S whereby the coordinates of the first two stations are known from S/X observations and of the latter from local surveying. With velocities from adjacent stations, the estimated coordinates were used to calculate a global solution of the 2019 VGOS sessions. The obtained coordinates were assessed on basis of formal errors, coordinate repeatability and comparisons of estimated Earth Orientation Parameters (EOP) time series with fixed station coordinates to the 14 C04 a priori dataset.
The mechanism of sapropel formation in the Mediterranean Sea: Insight from long duration box-model experiments
Authors: Dirksen Jan Pieter , Meijer Paul
Published: March 2020

Periodic bottom water oxygen deficiency in the Mediterranean Sea has led to the deposition of organic rich sediments during geological history, so called sapropels. Although a mechanism linking the formation of these deposits to orbital variability has been derived from the geological record, physics-based proof is limited to snapshot and short time-slice experiments with (Oceanic) General Circulation Models. Specifically, previous modelling studies have investigated atmospheric and oceanographic equilibrium states during orbital extremes (minimum and maximum precession).

In contrast, we use a conceptual box model that allows us to focus on the transient response of the Mediterranean Sea to orbital forcing and investigate the physical processes causing sapropel formation. The model is constrained by present day measurement data, while proxy data offers constraints on the timing of sapropels.

The results demonstrate that it is possible to describe the first order aspects of sapropel formation in a conceptual box model. A systematic model analysis approach provides new insights on features observed in the geological record, such as timing of sapropels, intra-sapropel intensity variations and interruptions. Moreover, given a scenario constrained by geological data, the model allows us to study the transient response of variables and processes that cannot be observed in the geological record. The results suggest that atmospheric temperature variability plays a key role in sapropel formation, and that the timing of the midpoint of a sapropel can shift significantly with a minor change in forcing due to nonlinearities in the system.
The aging process of ambient black carbon and brown carbon from biomass burning emission during MOYA-2017 aircraft campaign
Authors: Wu HuiHui , Taylor Jonathan , Langridge Justin , Yu Chenjie , Williams Paul , Flynn Michael , Coe Hugh
Published: March 2020

The biomass burning over West Africa during the dry season (December – February) is a globally significant source of trace gases and carbonaceous aerosol particles in the atmosphere. The MOYA-2017 (Methane Observations Yearly Assessments 2017) campaign were conducted using the UK FAAM Bae-146 airborne research aircraft, to investigate biomass burning emissions in this region. Research sorties were flown out of Senegal, with some flights directly over terrestrial fires and others sampling transported smokes over the Atlantic ocean.

The aircraft was equipped with a variety of aerosol-related instruments to measure submicron aerosol chemical properties (aerosol mass spectrometer, AMS and single-particle soot photometer, SP2) and absorption at different wavelengths (Photoacoustic spectrometer, PAS, measure at 405, 514 and 658 nm). In this study, we focus on the aging process of ambient black carbon (BC) and brown carbon (BrC) from biomass burning, in time scale from (<0.5) h to (9 – 15) h. The transport age of smokes was estimated using Met Office's Numerical Atmospheric-dispersion Modelling Environment (NAME).

The sampled smokes during MOYA-2017 were controlled by flaming-phase combustion. The enhancement ratios of BC with respect to CO ranged from 14 to 26 (ng m–3 / ppbv) at sources. Our measurements show that count and mass median diameters of BC core size were relatively stable, which were around 106 and 190 nm respectively. Average BC coating thickness increased from (1.16 ± 0.03) to (1.71 ± 0.06) after approximately half-day transport. Average absorption angstrom exponents (AAE405-658) increased from (1.1 ± 0.1) to (1.8 ± 0.3), suggesting that BrC contributed little in the very freshly emitted aerosols (<0.5 h) and were formed during aging process. In order to investigate the importance of BrC in this area, we also attributed the measured aerosol absorption into BC and BrC separately. By linking AAE405-658 with organic (OA) composition measured by the AMS, we found that the increasing AAE405-658 is positively correlated with O/C ratio (oxygenation) of the OA. These data indicate that BrC in smokes controlled by flaming combustion is likely to be from the condensation of semi-volatile OA during cooling stage of smokes, and from the aged primary OA or secondary OA formation.
Assessing soil moisture constraint on soil evaporation and plant transpiration fractioning
Authors: Ait Hssaine Bouchra , Merlin Olivier , Ezzahar Jamal , Er-raki Salah , Khabba Saïd , Chehbouni Abdelghani
Published: March 2020

Over semi-arid agricultural regions, detecting the crop water need at the onset of water stress is of paramount importance for optimizing the use of irrigation water. Evapotranspiration (ET) is a crucial component of the water cycle, it strongly impacts the water resource management, drought monitoring, and climate. Remote sensing observations provide very relevant information to feed ET models. In particular, the microwave-derived surface (0-5 cm) soil moisture (SM), which is the main controlling factor of soil evaporation, the visible/near-infratred-derived vegetation cover fraction (fc), which provides an essential structural constraint on the fractioning between vegetation transpiration and soil evaporation, and - thermal-derived land surface temperature (LST), which is a signature of both available energy and evapotranspiration (ET) rate. The aim of this work is to integrate those independent and complementary information on total ET within an energy balance model. As a state-of-the-art and commonly used model, we chose the TSEB modelling as a basis for developments. An innovative calibration procedure is proposed to retrieve the main parameters of soil evaporation (soil resistance, rss) and plant transpiration (Priestly Taylor coefficient, αPT) based on a threshold on fc. The procedure is applied over an irrigated wheat field in the Tensift basin, central Morocco. Overall, the coupling of the soil resistance formulation with the TSEB formalism improves the estimation of soil evaporation, and consequently, improves the partitioning of ET. Analysis of the retrieved time series indicates that the daily αPT mainly follows the phenology of winter wheat crop with a maximum value coincident with the full development of green biomass and a minimum value reached at harvest. The temporal variations of αPT before senescence are attributed to the dynamics of both the root zone soil moisture and the amount of green biomass.
Rainfall trends in hindsight and in foresight
Authors: Iliopoulou Theano , Koutsoyiannis Demetris
Published: March 2020

Trends are customarily identified in rainfall data in the framework of explanatory modelling. Little insight however has been gained by this type of analysis with respect to their performance in foresight. In this work, we examine the out-of-sample predictive performance of linear trends through extensive investigation of 60 of the longest daily rainfall records available worldwide. We devise a systematic methodological framework in which linear trends are compared to simpler mean models, based on their performance in predicting climatic-scale (30-year) annual rainfall indices, i.e. maxima, totals, wet-day average and probability dry, from long-term daily records. Parallel experiments from synthetic timeseries are performed in order to provide theoretical insights to the results and the role of parsimony in predictive modelling is discussed. In line with the empirical findings, it is shown that, prediction-wise, simple is preferable to trendy.
Investigation of spatial and temporal salinity distribution in river deltas through idealized numerical modelling
Authors: Matsoukis Constantinos , Amoudry Laurent , Bricheno Lucy , Leonardi Nicoletta
Published: March 2020

The world's river deltas are increasingly vulnerable due to pressures from human activities and environmental change. In deltaic regions, the distribution of salinity controls the resourcing of freshwater for agriculture, aquaculture and human consumption; it also regulates the functioning of critical natural habitats. Despite numerous insightful studies, there are still significant uncertainties on the spatio-temporal patterns of salinity across deltaic systems. In particular, there is a need for a better understanding of the salinity distribution across deltas’ channels and for simple predictive relationship linking salinity to deltas’ characteristics and environmental conditions. We address this gap through idealized three-dimensional modelling of typical delta configurations (river, tide dominated etc.) and by investigating the relationship between salinity, river discharge and channels’ bifurcation order. Model results are then compared with data from real delta cases. Results demonstrate the existence of simple one-dimensional and analytical relationships describing the salinity field in a delta. Salinity and river discharge are exponentially and negatively correlated. There is a correlation between salinity and channels bifurcation order and salinity increases linearly with decreasing stream order. These useful parametrizations of salinity distribution following deltas’ features and geometry might be applied to real case scenarios to support the investigation of deltas vulnerability to environmental change and the management of deltaic ecosystems.

 

Keywords: salinity, salt intrusion, river deltas, numerical modelling, idealized river delta models
Revision of the current theory of unstably stratified turbulence and its potential implications for PEEX
Authors: Zilitinkevich Sergej , Repina Irina
Published: March 2020

Turbulence in unstably stratified flows is traditionally considered as chaotic eddies generated on equal terms by the two very different mechanisms: mean velocity shears, and buoyancy forces. By this means, vertical buoyant plumes comprising “convective turbulence” are not distinguished form 3-dimensional shear-generated eddies comprising “mechanical turbulence”. The latter are dynamically unstable and, hence, break down to produce smaller eddies, thus performing direct cascade of turbulent kinetic energy (TKE) and other properties of turbulence from larger to smaller scales towards their molecular dissipation. The conventional theory does not distinguish convective plumes from mechanical eddies and, factually, postulates that plumes also perform the direct cascade. 

We declare that this conventional vision is erroneous except for the trivial case of domination of dynamic instability, when mechanical eddies destroy convective plumes and violently involve them into direct cascade. In geophysical convective boundary layers (CBLs), this condition is satisfied in the thin near-surface sublayer comprising usually less than one per cent of CBL. Beyond this sublayer, dominant role belongs to convective plumes that do not break down but merge to form larger plumes, thus, performing inverse cascade culminated in the conversion of convective TKE into kinetic energy of the CBL-scale self-organised structures: cells or rolls. Therewith, weak mechanical turbulence generated by the mean-flow shears performs usual direct cascade. Hence, horizontal TKE is fully mechanical, whereas vertical TKE is almost fully convective. The key role in this unorthodox picture play the rates of conversion of TKE or another property of convective turbulence into kinetic energy or anther property of the CBL-scale self-organised structures. We define this vision of unstably stratified turbulence theoretically and prove it experimentally by the example of TKE budget in horizontally homogenous atmospheric surface-layer flow.
How to stabilize nonlinear solvers for rate-independent plasticity problems?
Authors: Popov Anton , Reuber Georg
Published: March 2020

Plastic strain localization in a rate-independent limit is a physical phenomenon that demands robust and reliable nonlinear solves to be modeled in a computer. It is quite common on practice that standard iterative algorithms (e.g. Newton-Raphson), being applied to this demanding problem, lead to  convergence issues or even fail. From the physical viewpoint the problem can be attributed to the difference between the dilatation and friction angles for the pressure-sensitive materials, which gets worse as this difference gets larger.

Common remedies include deriving consistent Jacobian matrix, or switching to the equivalent rate-dependent visco-plastic formulation. Both methods have their specific side effects. A very high condition number of a heavily unsymmetrical Jacobian matrix renders it nearly useless in the context of an iterative linear solver, such as multigrid. Hence, the use of the Jacobian matrix is essentially limited to a 2D formulation, for which a direct solver is practical. The visco-plastic formulation is confusing form the conceptual viewpoint. It strives to achieve the convergence by modifying the physics of the problem. Hence, the stabilization viscosity is not a pure numerical parameter that can be freely selected, but it is a physical parameter that must be determined in the laboratory. The advantages of the visco-plastic formulation vanish, if rate-independent limit is considered, or if affordable grid size is (much) larger than the intrinsic localization length-scale. The latter condition is a dominant limiting factor for a 3D model. 

In this work we share a few recipes, that can potentially improve the convergence of the rate-independent plasticity problems, without relying on the availability of a direct solver, or perturbing the physics.
Using remote sensing to monitor peatland fire occurrence and recovery
Authors: Lees Kirsten , Buxton Josh , Boulton Chris , Lenton Tim
Published: March 2020

Many peatland areas in Great Britain are managed as grouse moors, with regular burns as part of management practice to encourage heather growth. Remote sensing has the potential to monitor the size, location, and impact of these burns using new fine resolution satellites such as Sentinel-2. Google Earth Engine allows large areas to be analysed at small scale over several years, building up a visual record of fire occurrence. This study uses satellite data to map managed burns on several areas of moorland around Great Britain, and uses remote sensing methods to assess the impact of this management strategy on vegetation cover. The project also considers how areas subject to managed burns react to wildfire occurrence, with the 2018 Saddleworth wildfire as a case study.
Photoinduced Production of Chlorine Molecules from Titanium Dioxide Surfaces Containing Chloride
Authors: Yuanyuan Li
Published: March 2020

Titanium dioxide (TiO2) is extensively used with the process of urbanization and potentially inflfluences atmospheric chemistry, which is yet unclear. In this work, we demonstrated strong production of Cl2 from illuminated KCl-coated TiO2 membranes and suggest an important daytime source of chlorine radicals. We found that water and oxygen were required for the reactions to proceed, and Cl2 production increased linearly with the amount of coated KCl, humidity of the carrier gas, and light intensity. These results suggested that water promotes the reactivity of coated KCl via interaction with the crystal lattice to release free chloride ions (Cl−). The free Cl− transfer charges to O2 via photoactivated TiO2 to form Cl2 and probably the O2− radical. In addition to Cl2, ClO and HOCl were also observed via the complex reactions between Cl/Cl2 and HOx. An intensive campaign was conducted in Shanghai, during which evident daytime peaks of Cl2 were observed. Estimated Cl2 production from TiO2 photocatalysis can be up to 0.2 ppb/h when the TiO2-containing surface reaches 20% of the urban surface, and this is highly correlated to the observed Cl2. Our results suggest a non-negligible role of TiO2 in atmospheric photochemistry via altering the radical budget.
Detecting non-linear sea-level variations in tide gauge records: a study case along the Dutch coast.
Authors: Riva Riccardo , Steffelbauer David , Kwakkel Jan , Timmermans Jos , Bakker Mark
Published: March 2020

Tide gauges are the main source of information about sea-level changes in the Industrial Age. When looking at global mean values, century-long reconstructions produce rates between 1-2 mm/yr, while estimates over the last three decades reveal a much faster rise of about 3 mm/yr, as also indicated by satellite altimetry observations. In spite of this evidence for a recent acceleration, its quantification remains a challenging and relevant task, because results are highly dependent on the length of the record and on the reconstruction technique, whereas decision makers require clear proof to legitimise action.

While global mean results are very important to understand climate change, regional to local variations are more relevant for the purpose of planning mitigation and adaptation measures. However, mainly due to natural variability, looking at individual tide gauge stations hampers the accurate determination of linear and non-linear trends.

We analyse tide gauge records along the Dutch coast by means of advanced statistical techniques, with the main objective of determining whether and under which conditions it is possible to detect departures from secular trends. We particularly focus on how to handle noise in the natural system, which for the Dutch coast is mainly represented by local atmospheric effects and by variability in ocean dynamics in the NE Atlantic.
Changes in radiative forcing due to clear-cutting in Sweden
Authors: Mužić Iris , Vestin Patrik , Lindroth Anders , Mölder Meelis , Biermann Tobias , Heliasz Michal , Rinne Janne
Published: March 2020

Land cover conversion affects climate by imposing perturbations in the surface properties and greenhouse gas fluxes. Forest management systems often disregard that modification in surface albedo influences the exchange of energy and greenhouse gases. In this study, we examine the net climatic effect of clear-cutting in high-latitude regions by comparing the importance of biogeophysical (albedo) and biogeochemical (carbon dioxide release) changes in Sweden. The hypothesis is that the albedo effect of high-latitude clear-cutting can reduce climate warming.

Data on incoming and reflected shortwave radiation was obtained from four-component net radiometers installed in the forest and neighbouring clear-cut sites, in southern (56°N), central (60°N) and northern (64°N) Sweden. The study site pairs along a latitudinal gradient were chosen to account for different climatic conditions. Data at these station pairs covered a continuous period of three (2016-2018), five (2014-2018) and one year (2014), respectively. Due to lack of clear-cut measurement stations in close vicinity to the northernmost forest site, the shortwave radiation data was retrieved from an open mire, where albedo and its temporal dynamics are similar to a clear-cut. All the forest stations and the mire station are part of ICOS Sweden network. Data on carbon dioxide release from clear-cutting was estimated as a difference in the aboveground carbon stock of the standing biomass between forest and clear-cut sites. The estimated carbon dioxide release was translated into an equivalent change in absorbed shortwave radiation and compared to the radiative forcing by albedo difference between forest and clear-cut sites.

Our results underline results from previous studies showing that the magnitude of the net radiative forcing by clear-cutting varies considerably depending on the latitudinal position of the examined sites. Based on available data, clear-cutting in southern and central Sweden had a warming effect on the climate while in northern Sweden clear-cutting had a net cooling effect. However, large inter-annual variability (central Sweden) and lack of available continuous data (northern Sweden) resulted in high uncertainty of the climatic effects of changes in net radiative forcing due to clear-cutting. Our study indicates that the albedo effect has an essential role in the estimation of the climatic effect of clear-cutting and should thus be incorporated in future forest management strategies.
ESM-Tools: A common infrastructure for modular coupled earth system modelling
Authors: Barbi Dirk , Wieters Nadine , Cristini Luisa , Gierz Paul , Khosravi Sara , Chegini Fatemeh , Kjellson Joakim , Wahl Sebastian
Published: March 2020

Earth system and climate modelling involves the simulation of processes on a large range of scales, and within very different components of the earth system. In practice, component models from different institutes are mostly developed independently, and then combined using a dedicated coupling software.

This procedure not only leads to a wildly growing number of available versions of model components as well as coupled setups, but also to a specific way of obtaining and operating many of these. This can be a challenging problem (and potentially a huge waste of time) especially for unexperienced researchers, or scientists aiming to change to a different model system, e.g. for intercomparisons.

In order to define a standard way of downloading, configuring, compiling and running modular ESMs on a variety of HPC systems, AWI and partner institutions develop and maintain the OpenSource ESM-Tools software (https://www.esm-tools.net). Our aim is to provide standard solutions to typical problems occurring within the workflow of model simulations such as calendar operations, data postprocessing and monitoring, sanity checks, sorting and archiving of output, and script-based coupling (e.g. ice sheet models, isostatic adjustment models). The user only provides a short (30-40 lines) runscript of absolutely necessary experiment specific definitions, while the ESM-Tools execute the phases of a simulation in the correct order. A user-friendly API ensures that more experienced users have full control over each of these phases, and can easily add functionality. A GUI has been developed to provide a more intuitive approach to the modular system, and also to add a graphical overview over the available models and combinations.

Since revision 2 (released on March 19th 2019), the ESM-Tools were entirely re-written, separating the implementation of actions (written in Python 3) from any information that we have, either on models, coupled setups, software tools, HPC systems etc. into nicely structured yaml configuration files. This has been done to reduce maintenance problems, and also to ensure that also unexperienced scientist can easily edit configurations, or even add new models or software without any programming experience. Since revision 3 the ESM-Tools support four ocean models (FESOM1, FESOM2, NEMO, MPIOM), three atmosphere models (ECHAM6, OpenIFS, ICON), two BGC models (HAMOCC, REcoM), an ice sheet (PISM) and an isostatic adjustment model (VILMA) as well as standard settings for five HPC systems. For the future we plan to add interfaces to regional models and soil/hydrology models.

The Tools currently have more than 70 registered users from 5 institutions, and more than 40 authors of contributions to either model configurations or functionality.
Impact of sea level data assimilation on the storm surge and seiche forecasts
Authors: Bajo Marco , Međugorac Iva , Umgiesser Georg , Orlić Mirko
Published: March 2020

This work assesses the impact of assimilating the sea level data, with an Ensemble Kalman Filter, on storm surge and seiche modelling. The study area is the Adriatic Sea, where seiches are always present after a storm surge, and often overlap on a new storm surge with a possible amplification of the total sea level. Due to errors in the wind and pressure forcing, the forecast of such extreme events is rather challenging in the Adriatic Sea, and a wrong reproduction of such pre-existing seiches reflects on a bad sea-level forecast. Here we show, by two case studies, that the assimilation of sea-level data along the coasts of the Adriatic basin is able to correct the initial state of the hydrodynamic model. Since the initial state is particularly important in the case of pre-existing seiches, the reduction of the initial error propagates several days into the forecast. The two cases here presented were between the most extreme storm surge events in the last years and they both included the pre-existing seiches. The initial forecast was very poor, due to the fact that the wind was underestimated. The assimilation of 3-day long hourly sea level data at eleven stations distributed along the Adriatic coasts produces a better forecast in both cases. Moreover, the ensemble spread allows the uncertainty of the forecast to be estimated, even if the estimate should be calibrated over time in order to be more reliable.
Study on the application of rock slope protection and ecological restoration technique based on vegetation membrane
Authors: Liang Zhishui , Wu Zhiren , Gao Haiying
Published: March 2020

Due to the hard surface and the lack of necessary soil environment for vegetation growth, the rock slope protection and ecological restoration is one of the research focuses nowadays. In this paper, we proposed a flexible slope protection method based on the vegetation membrane to protect the rock slopes including river and road slope. The vegetation membrane is a kind of organic bags which is perfused by a mechanical equipment with plant seeds, soil, sand, vermiculite, rice husk, adhesive material, water retaining agent with water in a certain proportion, forming a suitable environment for vegetation growth. Then the membrane is fixed on the rock slope by the anchor bolt in different specifications and quantities according to the different slope conditions. The results show that the minimum proportions of total nitrogen, phosphoric acid, potassium in the vegetation membrane are 5%, 25% and 10%, respectively. The tension load of the anchor bolt can reach 50 ~ 100 kg in different lengths. The vegetation coverage rate on the rock slope by this method can reach more than 80% in three months and the rock slope is much more stable. Additionally, two demonstrations of different rock slopes protected by this technique are briefly described and the good control effects are obtained. It will provide a new method for protecting steep and rock slopes.
Comparison of varve preservation and characteristics between remote and urban lakes in Finland
Authors: Salminen Sarianna , Uotinen Mikko , Saarni Saija
Published: March 2020

Comparison of varve preservation and characteristics between remote and urban lakes in Finland

 

Sarianna Salminen1, Mikko Uotinen1, and Saija Saarni2

1Department of Geography and Geology, University of Turku, Finland

2Ecosystems and Environment Research Programme, Faculty of Biological and Environmental Sciences, University of Helsinki, Finland

 

The occurrence of varved sediments in Finnish lakes is known to be dependent on certain features, such as morphometry of the lake and its catchment. However, varve preservation triggered by recent hypoxia has been observed in Finnish lakes of which sediments are not naturally laminated. In these lakes human-induced eutrophication and hypoxia might have been the major factor triggering varve preservation.

Here we compare varve preservation, varve characteristics, and varve qualities between one remote and naturally laminated (Lake Lehmilampi in Eastern Finland) and two lakes close to urban areas (Lake Vesijärvi in Southern Finland and Lake Kallavesi in Eastern Finland) with recent start of varve preservation.

Surplus of organic matter leading to hypoxia seems to have triggered the start of varve preservation in Lake Vesijärvi and possibly in Lake Kallavesi in the 20th century. In these two lakes several varve microfacieses were identified representing human-induced changes in the catchment. In the remote Lake Lehmilampi sedimentation rate is lower compared to the two urban lakes and the number of identified microfacieses is lower. The results suggest that in these three lakes varve characteristics, varve quality, and the cause of varve preservation as well as the continuity of varve preservation differ between lakes as a result of regional and local factors. In Lake Lehmilampi varve preservation seems to be dependent on lake and catchment morphometry as well as climate, whereas in Lake Vesijärvi and Lake Kallavesi varve preservation mainly seems to be dependent on anthropogenic factors. For instance, in Lake Vesijärvi rehabilitation actions seem to have affected varve preservation turning the sediment non-laminated. Furthermore, varve characteristics and quality seem to be sensitive to climate in Lake Lehmilampi, whereas in Lake Vesijärvi and Lake Kallavesi they correspond to anthropogenic changes.
Hydroclimate variability of western Thailand during the last 1400 years
Authors: chawchai sakonvan , Liu Guangxin , Bissen Raphael , Scholz Denis , Riechelmann Dana F.C. , Vonhof Hubert , Mertz-Krause Regina , Tan Liangcheng , Chiang Hong-Wei , Wang Xianfeng
Published: March 2020

Mainland Southeast Asia is located on the route of moisture transport of the Indian summer monsoon where hydroclimate records from speleothems have rarely been investigated. Here we present a new multi-proxy data set (δ18O, δ13C, trace elements and grayscale values) of stalagmite KPC1 from Khao Prae cave in western Thailand spanning from approximately 500 CE to 1900 CE. Our multi-proxy data reveal high variability between wet and dry periods during 500-850 CE and 1150-1350 CE, a stable condition between 850-1150 CE, and an overall trend towards dry conditions since 1350 CE. The δ13C, trace elements and grayscale values suggest centennial-scale fluctuations driven by local hydrological process at the cave site. In contrast, variations in stalagmite δ18O reflect integrated changes in rainfall amount from the Indian summer monsoon, supported by two-year monitoring rainfall data. In comparison with other Asian Monsoon records for the last millennia, the KPC1 record shows similarity with speleothem δ18O records from India, as well as lakes and tree-ring data from mainland Southeast Asia but diverges from records from equatorial regions and the western Pacific. We conclude that hydroclimate variability in the western side of Mainland Southeast Asia is mainly driven by changes in moisture transport from the Indian summer monsoon and modulated by expansion and contraction of the Intertropical convergent zone (ITCZ). However, Pacific Walker circulation (PWC) may have been the overriding control on precipitation on the eastern sides of Mainland Southeast Asia located closely to the western Pacific.
The compost from the wine industry as a source of nitrogen in vulnerable areas
Authors: Villena Gordo Raquel
Published: March 2020

The compost from the wine industry as a source of nitrogen in vulnerable areas

 

Raquel Villena1, M. Teresa Castellanos1, M. Carmen Cartagena1,2*, Ana M. Tarquis2 and. Augusto Arce1,2.

1 Departamento de Química y Tecnología de Alimentos. ETSIAAB-UPM. Avda. Puerta de Hierro 4. 28040 Madrid

2 CEIGRAM-UPM. Senda del Rey 13. 28040 Madrid

*mariacarmen.cartagena@upm.es

 

Abstract

            The use of organic waste in agriculture, from the agri-food industry, is one of the most important outlets for this type of waste. Once that it is stabilized, it plays an important role in the context of circular economy. The application of this in vulnerable areas, where it is produced, is a possible substitute for traditional fertilization (fertirrigation) avoiding continuous contamination of aquifers.

 

            Spain is the third world producer of wine. This industry generates between two and three million tons of organic waste annually being more than half generated in Castilla - La Mancha. The residues of the wine industry, can be valued in many ways. One of them could be the agricultural application as a source of organic matter and nutrients, given its chemical characteristics. These residues aerobically treated can be used in horticultural crops in the same area, as a source of nitrogen substituting traditional inorganic fertilization.

 

            In this work, a three years’ field experiment was carried out in a drip-irrigated melon crop, traditionally grown in the area where also, these wastes are generated in Mediterranean climatic conditions in Castilla – La Mancha. The area is designated as “vulnerable zone” by the Nitrates Directive (91/676/CEE). The objective was to compare the behavior environmental and nutritional of organic fertilization versus fertirrigation. Due to the slow rate of mineralization of these residues in the soil, it is essential to know their residual effect on it. This effect was studied using wheat as a capture crop.

 
Direct observations of a dynamic earthquake rupture in the lower crust
Authors: Petley-Ragan Arianne , Ben-Zion Yehuda , Austrheim Håkon , Ildefonse Benoit , Renard Francois
Published: March 2020

A significant number of studies in recent years have demonstrated that earthquakes in the lower crust are more abundant than previously thought. Specifically in continental collision zones, earthquakes are suggested to play a crucial role in permitting fluid infiltration and driving metamorphic transformation processes in crustal portions that are typically considered dry and metastable. However, the mechanisms that trigger brittle failure in the lower crust remain debated and the sequence of events that ultimately lead to seismic slip is unclear. To further understand this process we performed field and microstructural observations on an amphibolite facies fault (0.9-1 GPa) in granulite facies anorthosite from the Bergen Arcs, Western Norway. The fault preserves an exceptional record of brittle deformation and frictional melting that allows us to constrain the temporal sequence of deformation events. Most notably, the fault is flanked on one side by a damage zone where wall rock minerals are fragmented with little to no shear strain (pulverization). The fault core consists of a zoned pseudotachylyte bound on both sides by fine-grained cataclasites. Spatial relationships between these structures reveal that asymmetric pulverization of the wall rock and comminution preceded the seismic slip required to produce melting. These observations are consistent with the propagation of a dynamic shear rupture. Our study implies that high differential stress levels may exist within the dry lower crust of orogens, causing brittle faulting and earthquakes in a portion of the crust that has long been assumed to be characterized by ductile deformation.
Post-Little Ice Age retreat of glaciers triggered rapid paraglacial landscape transformation in Sørkapp Land (Spitsbergen)
Authors: Dudek Justyna , Strzelecki Mateusz Czesław
Published: March 2020

Contemporary climate warming in the Arctic affects the dynamics of the entire environment, including components of the cryosphere: permafrost and glacier systems. The change in the structure of the polar landscape since the termination of the Little Ice Age (ca. 1900) was expressed by widespread retreat of glaciers, progressive exposure of glacial landforms at ice margins and opening ice marginal zones to increasing paraglacial and periglacial processes operating synchronously in adjacent areas.

The main aim of the presented study was to determine the course and spatial diversity of landscape transformation in the Sørkapp Land peninsula (Spitsbergen) as a result of glacier recession in the periods 1961-1990-2010 based on existing remote sensing data. Using photogrammetric methods of data processing combined with GIS techniques, the rates of proglacial and ice-marginal terrain change following deglaciation have been determined.

For the mentioned research period, the area of the marginal zones almost doubled from 53 km² to 99 km². The dynamics of landscape transformation in these zones manifested in rapid reduction in the surface elevation of ice-cored moraines (with mean decrease of 0,18-0,22 m per year) and the forms underlain by the dead-ice. This process was enhanced by mass movements and debris flows. Within marginal zones, the area of subglacial landforms and sediments increased by 31 km² from 8 km² in 1961 to 39 km² in 2010.

Larger volume of proglacial waters and associated intensification of denudation, transport and accumulation of sediments entailed area increase of sandurs and proglacial riverbeds (which almost tripled from 3,5 km² to over 10 km²). Further redeposition and remobilization of material in some places also promoted enhanced sediment aggradation in coastal environment forming new beaches and spit systems.
Ancient to modern metallurgical slags: evolving smelting techniques and their interaction with the environment
Authors: Rocchi Irene , Rocchi Sergio , Masotta Matteo
Published: March 2020

The discovery of metals and how to extract and use them was a turning point in human history, because it changed the economy and socio-cultural structure of ancient civilisations and started to severely affect the impact of human activities on the environment. In fact, a lot of societies developed near extraction sites and founded their economy on the use and trade of metals.
In Tuscany (Italy) there has been a long history of mining and metal extraction. From archaeological studies it has been reconstructed that the earliest records of these activities date back to the Etruscan period (VII century B.C.). Exploitation continued intermittently until a few decades ago. This extended period of mining exploitation left a wealth of both iron and copper metallurgical slags that can usually be found as abandoned and unsupervised heaps.
These slags, apparently just a waste from the metallurgical process, actually carry information about the evolution of the metallurgical process through which they were generated. Information about the charge, flux and fuel can be inferred from chemical and mineralogical composition of the slags.
Slags from three different smelting districts, ranging from ancient Etruscan-Roman period to modern age (1900 A.D.)  were studied macroscopically, identifying distinctive features related to the smelting process in different time periods. Then, thin sections obtained from representative samples were examined, using optical microscopy and electron microscopy. Chemical analyses were performed for major and trace elements by X-ray fluorescence spectroscopy and by inductively coupled plasma mass spectrometry, respectively.
Leaching experiments on some carefully selected samples were also completed, to investigate the release of potentially toxic elements during the interaction of the slags with the surrounding environment.
This kind of investigation allows to reconstruct part of the history of metal utilisation as well as to predict the impact that these remains will have on the environment.
Large-scale Mapping of Arctic Coastal Infrastructure using Copernicus Sentinel Data and Machine Learning and Deep Learning Methods
Authors: Pointner Georg , Bartsch Annett , Ingeman-Nielsen Thomas
Published: March 2020

The climate change induced increased warming of the Arctic is leading to an accelerated thawing of permafrost, which can cause ground subsidence. In consequence, buildings and other infrastructure of local settlements are endangered from destabilization and collapsing in many Arctic regions. The increase of the exploitation of Arctic natural resources has led to the establishment of large industrial infrastructures that are at risk likewise. Most of the human activity in the Arctic is located near permafrost coasts. The thawing of coastal permafrost additionally leads to coastal erosion, which makes Arctic coastal settlements even more vulnerable.

The European Union (EU) Horizon2020 project “Nunataryuk” aims to assess the impacts of thawing land, coast and subsea permafrost on the climate and on local communities in the Arctic. One task of the project is to determine the impacts of permafrost thaw on coastal Arctic infrastructures and to provide appropriate adaptation and mitigation strategies. For that purpose, a circumpolar account of infrastructure is needed.

During recent years, the two polar-orbiting Sentinel-2 satellites of the Copernicus program of the EU have been acquiring multi-spectral imagery at high spatial and temporal resolution. Sentinel-2 data is a common choice for land cover mapping. Most land cover products only include one class for built-up areas, however. The fusion of optical and Synthetic Aperture Radar (SAR) data for land cover mapping has gained more and more attention over the last years. By combining Sentinel-2 and Sentinel-1 SAR data, the classification of multiple types of infrastructure can be anticipated. Another emerging trend is the application machine learning and deep learning methods for land cover mapping.

We present an automated workflow for downloading, processing and classifying Sentinel-2 and Sentinel-1 data in order to map coastal infrastructure with circum-Arctic extent, developed on a highly performant virtual machine (VM) provided by the Copernicus Research and User Support (RUS). We further assess the first classification results mapped with two different methods, one being a pixel-based classification using a Gradient Boosting Machine and the other being a windowed semantic segmentation approach using the deep-learning framework keras.
Vertical distribution, seasonality and troposphericity of ice-supersaturated air masses in the northern mid-latitudes from regular in-situ observations by passenger aircraft
Authors: Petzold Andreas , Rohs Susanne , Rütimann Mihal , Neis Patrick , Florian Berkes , Herman Smit , Martina Krämer , Nicole Spelten , Peter Spichtinger , Philippe Nedelec , Andreas Wahner
Published: March 2020

The vertical distribution and seasonal variation of water vapour volume mixing ratio (H2O VMR), relative humidity with respect to ice (RHice) and particularly of regions with ice-supersaturated air masses (ISSR) in the extratropical upper troposphere and lowermost stratosphere are investigated at northern mid-latitudes over the regions Eastern North America, the North Atlantic and Europe for the period 1995 to 2010.

Observation data originate from regular and continuous long-term measurements of H2O VMR, temperature and RHice by instrumented passenger aircraft in the framework of the European research program MOZAIC which is continued as European research infrastructure IAGOS (from 2011; see www.iagos.org). The observation data are analysed with respect to the thermal and dynamical tropopauses, as provided by ERA-Interim. Additionally, collocated O3 observations from MOZAIC are used as tracer for stratospheric air masses.

Our key results provide in-depth insight into seasonal and regional variability and tropospheric nature of ice-supersaturated air masses at various distances from the tropopause layer. For the vertical distribution and seasonal variation of ISSR occurrence we show a comparison of our results to radio soundings and to satellite observations of cirrus cloud occurrence from AIRS and TOVs Path B instruments. Finally, for all three regions, we investigate the trends and the dependencies of ISSR occurrence on the North Atlantic Oscillation (NAO) index.