bluuebunny/crossref_metadata_2025 huggingface dataset:
Hygroscopic properties of saline mineral dust from different regions in China
Authors: Tang Mingjin , Zhang Huanhuan , Gu Wenjun
Published: March 2020

Saline mineral dust particles, emitted from saline topsoil in arid and semi-arid regions, contribute significantly to tropospheric aerosol particles. However, hygroscopic properties of saline mineral dust particles, especially for those found in regions other than North America, are poorly understood. In this work we investigated hygroscopic properties of thirteen saline mineral dust samples collected from different locations via measuring sample mass change as different relative humidity (RH, up to 90%), and measured their chemical and mineralogical compositions using ion chromatography and X-ray diffraction. The mass growth factors at 90% RH, defined as the sample mass at 90% RH relative to that at <1% RH, were found to display large geographical variations, spanning from ~1.02 to 6.7, and the corresponding single hygroscopicity parameters (κ) were derived to be in the range of <0.01 to >1.0. The saline components (mainly Na+, Cl- and SO42-) contained by saline mineral dust particles largely determined their hygroscopicity, and the predicted mass growth factors at 90% RH using an aerosol thermodynamic model (ISORROPIA-II), agreed with measured values within 20% for most of samples examined, though larger discrepancies also occurred for three samples. Our results improve our understanding in hygroscopicity of saline mineral dust particles and thus their heterogeneous chemistry and ability to serve as cloud condensation nuclei to form cloud droplets.
Magmatic centers and rift segmentation: insights from the Late Quaternary Menengai Caldera, Central Kenya Rift
Authors: Riedl Simon , Melnick Daniel , Mibei Geoffrey K , Njue Lucy , Strecker Manfred R
Published: March 2020

In magmatically active continental rifts, crustal deformation is often accompanied by caldera volcanism along the rift axis. These caldera volcanoes help to characterize the spatiotemporal relationship between regional tectonic extension, the development of normal faults, and the role of magmatism during the long-term evolution of continental rifts. In the Kenya Rift, magmatic activity has been focused at regularly spaced Quaternary volcanoes, each located within an extensional sub-basin of the rift. We document the structural characteristics of the c. 36-ka-old Menengai Caldera and adjacent regions located within such a young zone of extension, to gain insight into the role of regional-scale structures and volcanism in a rift zone subjected to oblique extension, and discuss the role of magmatic centers in the context of advanced stages of rift-basin differentiation.

Our field mapping and high-resolution digital surface models in the greater Menengai area located in the Central Kenya Rift show that the interior rift sectors are dominated by NNE-striking Holocene normal faults perpendicular to the regional ESE-WNW extension direction. Inside the caldera, these structures continue, but are overprinted by post-collapse doming and faulting of the magmatic center, resulting in obliquely slipping normal faults bounding a resurgence horst. Radiocarbon dating of faulted units as young as 5 ka cal BP and the paleo-shorelines of a lake formed during the African Humid Period in the Nakuru Basin that we use as strain markers indicate that volcanism and faulting inside and in the vicinity of Menengai must have been sustained during the Holocene.

Our analysis confirms that the caldera is located at the center of an extending rift segment that is kinematically linked with adjacent zones of extension; similar volcano-tectonic relationships apply to virtually all larger volcanic centers in the Kenya Rift. These zones of extension in the inner sectors of the rift are arranged in en échelon patterns and are linked by transfer zones. In contrast to punctiform spreading centers in much more advanced extensional regions (e.g., the Red Sea) normal faulting in the Kenya Rift is not focused at these volcanic centers. We suggest that the magmatic centers in the segmented Kenya Rift are precursors of a more evolved rifting stage, where magmatic centers may constitute nucleation points of faulting in future magma-assisted rifting that will ultimately lead to the final stages of continental break-up.
Impact study of scatterometer observations with improved representation error in an Arctic data assimilation system
Authors: Mile Máté , Randriamampianina Roger , Marseille Gert-Jan
Published: March 2020

Nowadays, satellite observations are providing primary information for initial conditions of state-of-the-art numerical weather prediction (NWP) systems and the amount of remote sensing data in the Global Observing System increases rapidly. However, the way such data are assimilated is usually conservative and sub-optimal especially in high resolution limited-area models. Our objective is to improve the use of scatterometer observations from polar-orbiting satellites by taking into account the observation footprint and reducing the observation representation error through the observation operator.

 

The variational assimilation system (including 3D- and 4D-Var) of HARMONIE-AROME is widely used for research and operational NWP purposes by many European countries. In most cases, the HARMONIE-AROME model and its data assimilation are run on higher resolution (corresponding to around 2.5km grid size or smaller) than the effective resolution of some satellite observations (e.g. the effective resolution of scatterometer instruments). The use of ASCAT scatterometer observations is studied in an Arctic data assimilation system (AROME-Arctic) and a new observation operator (called supermodding) is evaluated in terms of scatterometer representation error. The results are demonstrated through data assimilation diagnostics, observing system experiments and case studies focusing on the challenges of the Arctic weather forecasting as well.
Study of groundwater vulnerability in three unconfined aquifers in Slovenia
Authors: Curk Miha , Glavan Matjaž , Adu-Gyamfi Joseph , Halder Janine , Cerar Sonja , Zupanc Vesna
Published: March 2020

Groundwater is the main source of drinking water in Slovenia, but nitrate pollution originating from agriculture and urban areas is threatening its quality in several areas of the country. The aim of this study is to assess the vulnerability of three different unconfined aquifers in Slovenia (Ljubljansko polje, Dravsko-ptujsko polje and Krško-brežiško polje). All three study areas are located on alluvial plains with shallow groundwater levels and similar soil types, but different ratios of urban and agricultural land use. Soil types and land use were analyzed in each area as they contribute strongly to leaching of nitrate. Along with this we performed the analysis of stable isotopes of O, H and N to determine the origin of groundwater recharge and trace the possible sources of nitrate pollution. Results will give us an overview of nitrate pollution pathways through better understanding of nitrate sources, vulnerable areas, and groundwater recharge characteristics.
A model for the longitudinal patterns shaped by water on erodible rocks
Authors: Bertagni Matteo Bernard , Camporeale Carlo
Published: March 2020

The interactions between water and rocks create an extensive variety of marvelous patterns, which span on several classes of time and space scales. In this work, we provide a mathematical model for the formation of longitudinal erosive patterns commonly found in karst and alpine environments. The model couples the hydrodynamics of a laminar flow of water (Orr-Somerfield equation) to the concentration field of the eroded-rock chemistry. Results show that an instability of the plane rock wetted by the water film leads to a longitudinal channelization responsible for the pattern formation. The spatial scales predicted by the model span over different orders of magnitude depending on the flow intensity and this may explain why similar patterns of different sizes are observed in nature (millimetric microrills, centimetric rillenkarren, decametric solution runnels).
Lost in the waters: contemporary dilemmas in examining transboundary water interaction
Authors: Grünwald Richard , Feng Yan , Wang Wenling
Published: March 2020

The presented paper examines current dilemmas in transboundary water interaction and debates about the reconceptualization of the Transboundary Water Interaction Nexus (TWINS). The new TWINS framework provides a theoretical alternative how to (1) evaluate the interstate relations between two or more actors regardless their legal status; (2) calculate the transboundary water interaction based on process tracing analysis rather than milestone analysis; (3) distinguish more intensities of cooperation and conflict, (4) clarify broader hydropolitical context in transboundary water interaction, and (5) debate about dual water event phenomenon where one event may possess both cooperation and conflict features. Currently, the new TWINS model serves as an indicator for evaluating cooperation and conflict intensity of water-related events in the Lancang-Mekong River Basin. The data are then recorded in the Lancang-Mekong Cooperation and Conflict Database (LMCCD) designed by authors which already comprise more than 1600 water-related events in the last 30 years (1990-2020). To proof the viability of the presented concept, we will illustrate the new TWINS model on a case study related to the Xayaburi hydropower dam. Although there are still several methodological limitations, the new TWINS model can be adapted to any interstate water-related issue and be able to fill the information gaps about the interdisciplinary understanding of the transboundary water interaction.
Olive husks biochar application in microbial remediation of pyrene polluted soil: a possible win-win solution
Authors: Piscitelli Lea , Malerba Anna Daniela , Mezzapesa Giuseppe Natale , Dumontet Stefano , Mondelli Donato , Miano Teodoro , Bruno Giovanni Luigi
Published: March 2020

Human activities are negatively affecting ecosystems through the erosion and impoverishment of natural resources. Considering soil, global warming and unsustainable agricultural practices are reducing soil organic matter with consequent loss of fertility. An issue of major concern is also the soil pollution by organic and inorganic compounds affecting soil ability to generate ecosystem services. Polycyclic aromatic hydrocarbons are a large group of pollutants, made of two or more aromatic rings, widespread in the environment, soil included, and extremely toxicity for human and environmental health. Polycyclic aromatic hydrocarbons persistence in soil is an issue great concern that could be effectively faced by microbial remediation techniques.

In this work we studied the remediation of pyrene polluted soil through two parallel tests: bioremediation and biostimulatin techniques. The first involves inoculation into soil of exogenous microorganisms, in our case Trichoderma harzianum, whereas the latter was aimed at promoting the degrading ability of endogenous microorganisms. Moreover, in order to sustain microorganisms growth, we incorporated olive husk biochar in the two tested bioremediation systems.

Biochar is currently considered an excellent soil conditioner and its incorporation into soil seems to promote PAHs adsorption and to interact positively with soil microorganisms. Biochar is a carbonaceous matrix produced through thermal processing of organic biomasses at high temperature and at very low oxygen partial pressure. Here we converted olive husks, that is a potentially toxic by-product of olive oil extraction, by slow pyrolysis process with the aim of deprived this waste biomass of its noxious characteristics.

Soil samples were spiked with 50 ppm of pyrene, biochar was incorporated at a concentration of 13 g·kg–1 d.w. of soil and endogenous microbial growth, T. harzianum growth and microbial pyrene-degradation activity were measured weekly up to 28 days.

Pyrene concentration was reduced of approximately 70% in 28 days in both bioaugmentation and biostimulation remediation systems. T. harzianum did not display a distinctive ability in degrading pyrene and partially inhibited the endogenous soil microflora from degrading pyrene. Olive husks biochar application did not limited pyrene bioavailability or neither affected microbial pyrene degrading activity. However, our results underline that olive husks biochar increases T. harzianum growth and stimulates soil endogenous microorganisms.
Mechanisms and predictability of Sudden Stratospheric Warming in winter 2018
Authors: Erner Irene , Karpechko Alexey , Järvinen Heikki
Published: March 2020

In this study, we investigate the Sudden Stratospheric Warming that took place on 12 February 2018 (SSW2018), its predictability and teleconnection with the Madden-Julian Oscillation (MJO) by analysing ECMWF ensemble forecast initialised on 1 February 2018. Several days prior to that date MJO was in Phase 6 and had a strong amplitude potentially contributing to triggering the SSW. Two wave trains can be identified in the upper troposphere over the northern Atlantic and Pacific regions. Starting from the 3 February, the amplitude of planetary wave with wavenumber 2 (PW2) started to increase and reached record high values, while the PW1 amplitude decreased.In order to better understand the sources of uncertainties, we divided the forecast ensemble members into two groups. The first group predicted the SSW onset in time while the second group of ensemble members did not capture the wind reversal at 60°N 10 hPa. The results obtained with the ensemble forecast data were compared with the ECMWF’s reanalysis ERA-Interim (ERA-I). The analysis of the two groups of ensemble forecasts shows that in the first group of forecasts PW2 prevailed with ridges over the Ural and Alaska and troughs over the west Siberia and Canada, as observed. Instead, PW1 is seen in the second group of ensemble members with a broad ridge over Eurasia. Calculations of wave activity fluxes show that there is less zonal wave energy propagation in the second group compared to the first group and ERA-I over Eurasia, which can be associated with the errors in the forecasted location of the Ural high. There is also wave energy propagation towards an area of high pressure over Alaska, as seen in ERA-I. Here, wave energy propagation is similarly underestimated by both groups. Overall, the structure of the geopotential anomalies averaged for 5-7 February for the first group and ERA-I is more consistent with the climatological response from MJO phase 6 taken with lag 5-9 days than that in the second group.
Nitrate-driven high PM2.5 episodes in Seoul during pre-monsoon season
Authors: Park Joonhyoung , Lim Saehee , Lee Meehye , Lee Taehyung , Park Moon-soo , Heo Gookyoung , Kim Cheol-hee
Published: March 2020

Ammonium nitrate (NH4NO3) is the main driver of high PM2.5 episodes in Seoul, but its formation processes are not fully understood yet. Intensive experiments were conducted at the Korea University campus in Seoul during June ~ August 2018 and April ~ June 2019, when the chemical composition of PM2.5 including Na+, SO42-, NH3, NO3-, Cl-, Ca2+, K+, Mg2+, OC and EC, and its gaseous precursors including NOX, HNO3 and SO2 were continuously measured. The concentrations of PM2.5 and its major constituents were noticeably higher in pre-monsoon (June) than summer monsoon (July~August) period. In particular, nitrate concentration was much higher (6.9 μg/m3) during the high PM2.5 episode (24-hr average PM2.5 > 35 μg/m3) in June compared to those of non-episode (3.1 μg/m3) and the other two months (0.74 μg/m3). Aerosol liquid water content (ALWC) was calculated using ISORROPIA II model, ALWC was higher during the episode than non-episode and the highest ALWC was found concurrently with the highest NO3- concentration (18.2 μg/m3) at night. Concurrent increases of nitrate and ALWC cause aqueous-phase formation and hygroscopic growth of aerosol, which lead to high PM2.5 concentration. In addition, ALWC was more rapidly increased with the number of accumulation mode particles larger than 100 nm in diameter at higher RH and nitrate concentration. In this study, PM2.5 mass and nitrate were elevated after the NOX peak in the morning as well as at dawn. The surface of pre-existing particles was found to be prerequisite for nitrate driven PM2.5 episode.
New insights and best practices for the succesful use of Empirical Mode Decomposition, Iterative Filtering and derived algorithms in the decomposition of nonlinear and nonstationary signals
Authors: Cicone Antonio , Stallone Angela , Materassi Massimo , Zhou Haomin
Published: March 2020

Nonlinear and nonstationary signals are ubiquitous in real life. Their time–frequency analysis and features extraction can help in solving open problems in many fields of research. Two decades ago, the Empirical Mode Decomposition (EMD) algorithm was introduced to tackle highly nonlinear and nonstationary signals. It consists of a local and adaptive data–driven method which relaxes several limitations of the standard Fourier transform and the wavelet Transform techniques, yielding an accurate time-frequency representation of a signal. Over the years, several variants of the EMD algorithm have been proposed to improve the original technique, such as the Ensemble Empirical Mode Decomposition (EEMD) and the Iterative Filtering (IF).

The versatility of these techniques has opened the door to their application in many applied fields, like geophysics, physics, medicine, and finance. Although the EMD– and IF–based techniques are more suitable than traditional methods for the analysis of nonlinear and nonstationary data, they could easily be misused if their known limitations, together with the assumptions they rely on, are not carefully considered. Here we call attention to some of the pitfalls encountered when implementing these techniques. Specifically, there are three critical factors that are often neglected: boundary effects; presence of spikes in the original signal; signals containing a high degree of stochasticity. We show how an inappropriate implementation of the EMD and IF methods could return an artefact–prone decomposition of the original signal. We conclude with best practice guidelines for researchers who intend to use these techniques for their signal analysis.
The role of repeat photography in establishing theories of transition in high mountain environments
Authors: Fischer Andrea
Published: March 2020

Today, photos play an important role in geoscience and public discussion. When photographical techniques developed during the second half of the 19th century, it took several decades uuntil high mountain areas and specific features could be captured with this technique, as a follow upt o traditional paintings and drawings. In European geography, Friedrich Simony developed the idea of tackling geomorphological processes by time lapse photography. Contemporary literature shows that his technique of combining photography with empirical data and theories was convincing, and that he established a new style of scientific discussion. Still, the comparison of historical with contemporary photography offers scientific insights and information which is not covered by any other type of empirical evidence as measurements, maps or descriptions. For example not only extent, but also firn and debris cover of glaciers, information on type and extent of vegetation,  the width and style of roads, details of infrastructure and cultural practices can be tackled from early photographs.  Several archives do allow not only acess to photographic documents, but also to metadata. Interdisciplinary effort has to be taken to further analyse this wealth of information.
Multi-band imaging of seismic source rupture process
Authors: Du Hailin , Zhang Xu , Wang Yongzhe
Published: March 2020

The standard method to image the source rupture process of a large earthquake is finite fault inversion, which uses the low-frequency signal to invert the slip distribution of the fault. However, in different stages of the source rupture process of a large earthquake, the seismic waves radiated by the source have different dominant frequencies, such as high frequency seismic waves excited by the rupture front. If we can analyze seismic waves in different frequency bands, it is expected to obtain a more detailed source rupture process of large earthquakes. Therefore, we respectively adopted the high frequency signal back-projection imaging method and the low frequency signal finite fault inversion method, and took the 2016 Kaikoura MW7.8 earthquake as an example to obtain the history of rupture propagation and fault slip distribution.The calculated results show that the high-frequency energy radiation of the earthquake can be divided into three stages, and the low-frequency energy radiation can be divided into two stages. The energy release process in different frequency bands is complementary in time and space. The rupture process of the whole source can be explained by the asperity model and the barrier model.
Cooperative use of non invasive sensing methodologies for the geophysical monitoring of the archaeological park of Paestum
Authors: Capozzoli Luigi , Soldovieri Francesco , Rizzo Enzo , Catapano Ilaria , Ludeno Giovanni , Gennarelli Gianluca , De Martino Gregory , Scelza Francesco Uliano , Zuchtriegel Gabriel
Published: March 2020

The deployment of non-invasive sensing methodologies capable of providing information useful to characterize, monitor and manage archaeological sites represents a fundamental step for the conservation/preservation of cultural heritage assets. In the framework of the national project VESTA (funded by the Campania Region), several non invasive activities have been carried out for testing a novel approach of analysis including in situ methodologies, drone and satellite technologies.

This communication deals with a case study carried out at the monumental archaeological site of Paestum, sited in the southern Italy, where Greek settlers founded the ancient city of Poseidonia (6th century B.C.) [1]. At this site, geophysical surveys based on the combined use of magnetometric analyses [2], geoelectrical surveys [3] and ground-penetrating radar measurements [4] have been performed. Specifically, the areas immediately close to the temples of Ceres and Neptune have been investigated to identify unknown and buried archaeological features and characterise the paleo-morphological context. The different resolution and depth of investigations related to the application of each one of the considered methodologies as well as the use of tomographic methodologies for the data processing allowed the collection of images showing different subsurface features of the investigated area at different spatial scale. These images made possible the identification of anomalies of the subsoil, which were useful both to respond to the questions of the archaeologists and give new perspectives for managing the site. At the conference, the results of the integrated geophysical surveys, as well as their archaeological interpretation, will be presented with a focus on the cultural and social value of the “water resource” for the ancient city of Poseidonia.

 

[1] https://www.museopaestum.beniculturali.it/?lang=en

[2] A. Aspinall, C. Gaﬀney, A. Schmidt, A Magnetometry for archaeologists. Geophysical methods for archaeology, Altamira Press, Lanham (2008).

[3] A. Binley, A. Kemna, DC resistivity and induced polarization methods. InHydrogeophysics Water and Science Technology Library; R. Yuram, S.S- Hubbard, S.S., Eds.; Springer: New York, NY, USA (2005).

[4] D. J. Daniels, Ground penetrating radar, IET (2004).
The Rise And Fall Of An Oyster Bed In The German Bight (North Sea) Before The Dawn Of Industrial Fishery
Authors: Hass H. Christian , Michaelis Rune , Sander Lasse , Hausen Tanja , Pogoda Bernadette
Published: March 2020

The European flat oyster (Ostrea edulis, EFO) has been common in the North Sea at least throughout the late Holocene. Aside from its important ecological function as a reef builder the EFO has been of high economic value ever since man invented commercial fishery. During first half of the 20th century CE the EFO became functionally extinct in the German Bight. It is commonly agreed that industry-style overexploitation using dredges and trawls destroyed the habitats and eventually caused the extirpation of the EFO. Today, the EFO is a severely endangered and protected species.

Recently, an as yet uncharted fossil EFO bed was encountered close to the island Helgoland (German Bight, SE North Sea), that does not reveal any obvious signs of the physical disturbances typical for heavily harvested sites. This suggests possible environmental forcing behind the decline of this particular EFO bed, which could also have contributed to the fall of the entire oyster population of the German Bight.

The area was surveyed using drift videos along with grab samples to locate the EFO bed, measure its perimeter and evaluate characteristics, such as the density of shells. A total of 590 shells from 17 locations were measured (length, width) and weighed. A total of 19 shell samples from 17 locations were AMS radiocarbon dated to obtain absolute age control.

The EFO bed is located on a rocky slope to the west of Helgoland, its area is about 0.6 km2 and the water depth ranges between 32 and 43 m. The shallower parts are characterized by rubble whereas the EFO bed disappears under muddy sediments in the deeper parts. A rough estimation reveals around 200,000,000 single oyster shells in this bed. The oldest shell dated to about 4000 years BP, the youngest age dates to the beginning of the 19th century CE. Most shell ages are between 2700 and 2000 years BP. A hiatus occurs between 1300 and 300 years BP, and only one measurement reveals an age younger than 1300 years.

This EFO bed had perished already 1300 years ago, hence intense fishery as a reason can be ruled out. Today, the deeper part of the EFO bed is affected by muddy sediment that temporally buries the seafloor and occasionally forms turbid clouds of suspended matter. The sediment likely originates from large rivers (e.g. Rhine, Weser, Elbe) and the mudflats of the Wadden Sea. Climatic/oceanographic fluctuations that had modified the discharge and transport of muddy sediments in combination with increased influx of sediment from fluvial sources as a result of land-use changes in early medieval central Europe may have been a major stressor for the oyster habitats, albeit biological stressors cannot be ruled out.
A Study of MODIS-Based Ecosystem Respiration Model in a Semi-Arid Grassland of Inner Mongolia
Authors: Jiang Haimei , Ye Haotian , Hao Yong
Published: March 2020

Eddy covariance data from Xilinhaote National Climatological Observatory in Xilin Gol League during growing seasons of 2010—2013 as well as MODIS data were used to validate an ecosystem respiration model based on enhanced vegetation index (EVI), land surface water index (LSWI) and land surface temperature (LST) in a semi-arid grassland of Inner Mongolia. The limitations of this remote sensing respiration model were also discussed. The results indicate that this model can successfully simulate the variations of nocturnal ecosystem respiration (Reco) in the growing seasons and between different years. The simulated nocturnal Reco also agreed remarkably with the observed Reco (R2=0.90, RMSE=0.02 mgCO2/(m2·s)). Moreover, the observed nocturnal Reco showed a good linear correlation with EVIs×Ws (R2=0.63), in which EVIs and Ws are response functions of EVI and LSWI on photosynthesis, respectively. The response of nocturnal Reco to LST was also found following the L-T equation (R2=0.39). In addition, the difference between responses of nocturnal Reco to EVIs×Ws and LST in the early, middle and late stages of the growing season is indicated as one principal source of the deviations of model results.
Comparison of seismic velocities derived from crystal orientation fabrics and ultrasonic measurements on an ice core
Authors: Hellmann Sebastian , Kerch Johanna , Grab Melchior , Löwe Henning , Weikusat Ilka , Bauder Andreas , Maurer Hansruedi
Published: March 2020

Understanding the internal structure of glacier ice is of high interest for studying ice flow mechanics and glacier dynamics. The micro-scale deformation mechanisms cause a reorientation and alignment of the ice grains resulting in a polycrystalline structure with a strong anisotropy. By studying the crystal orientation fabric (COF), details about past and ongoing ice deformation processes can be derived. Usually, obtaining COF requires a work-intensive ice core analysis, which is typically carried out only at a few ice core samples. When similar information can be obtained from geophysical, for example, seismic experiments, a more detailed and more continuous image about the ice deformation would be available.
For checking the suitability of seismic data for such purposes, we have analysed the COF of several ice core samples extracted from Rhone Glacier, a temperate glacier located in the Central Swiss Alps. The COF analysis yield a polycrystalline elasticity tensor for a given volume of ice, from which we predicted seismic velocities for acoustic waves originating from any azimuth and inclination. The seismic data predicted were then verified with ultrasonic experiments conducted along the ice core in the vicinity of the analysed COF. Additional X-ray tomographic measurements yield further constraints about the microstructure, especially about the air bubble content in the ice affecting the data of the ultrasonic experiments. Predicted and measured velocities generally show a good match. This is a very encouraging result, because it suggests that in-situ measurements of seismic velocities can be employed for studying ice deformation. A possible option is to perform seismic cross-hole measurements within an array of boreholes drilled into the glacier ice.
Estimation of Vertical Land Motion at the Tide Gauges in Turkey
Authors: Erkoç Muharrem Hilmi , Doğan Uğur , Özarpacı Seda , Yildiz Hasan , Sezen Erdinç
Published: March 2020

This study aims to estimate vertical land motion (VLM) at tide gauges (TG), located in the Mediterranean, Aegean and the Marmara Sea coasts of Turkey, from differences of multimission satellite altimetry and TG sea level time series. Initially, relative sea level trends are estimated at 7 tide gauges stations operated by the Turkish General Directorate of Mapping over the period 2001-2019. Subsequently, absolute sea level trends independent from VLM are computed from multimission satellite altimetry data over the same period. We have computed estimates of linear trends of difference time series between altimetry and tide gauge sea level after removing seasonal signals by harmonic analysis from each time series to estimate the vertical land motion (VLM) at tide gauges. Traditional way of VLM determination at tide gauges is to use GPS@TG or preferably CGPS@TG data. We therefore, processed these GPS data, collected over the years by several TG-GPS campaigns and by continuous GPS stations close to the TG processed by GAMIT/GLOBK software. Subsequently, the GPS and CGPS vertical coordinate time series are used to estimate VLM. These two different VLM estimates, one from GPS and CGPS coordinate time series and other from altimetry-TG sea level time series differences are compared.

 

Keywords: Vertical land motion, Sea Level Changes, Tide gauge, Satellite altimetry, GPS, CGPS
Ending the Cinderella Status of Terraces and Lynchets in Europe
Authors: Fallu Daniel , Brown Tony , Walsh Kevin , Cucchiaro Sara , Tarolli Paolo , Zhao Pengzhi , van Oost Kristof , Snape Lisa , Lang Andreas , Albert Rosa-Maria , Alsos Inger , Waddington Clive
Published: March 2020

Terraces and lynchets are not only ubiquitous worldwide and within Europe but can provide increasingly important Ecosystem Services (ESs), which may be able to mitigate aspects of climate change. They are also probably a major cause of non-linearity between climate and erosion rates in agricultural systems as noted from alluvial and colluvial studies. In this paper we review the theoretical background of terraces and lynchets, present a modified classification, and show how new techniques are transforming the study of these widespread and often ancient anthropogenic landforms. Indeed the problems of dating terraces and also the time-consuming nature and costly surveys has held back the archaeological study of terraces until now. The applicable suite of techniques available now includes the creation of Digital Terrain Models (DTMs) from Structure from Motion (SfM) photogrammetry, Airborne and Terrestrial Laser Scanning (ALS-TLS); the use of OSL and pOSL, pXRF, FTIR, phytoliths, calcium oxalates from plants and potentially sedaDNA. Examples will be drawn from a recently started ERC project (TerrACE; ERC-2017-ADG: 787790, 2018-2023; https://www.terrace.no/) which is working at over 10 sites in Europe ranging from Norway to Greece.

This paper explains the development of a new holistic approach to terrace archaeology driven by a modern conceptualisation of human-landscape relationships, and facilitated by new scientific developments. We explain the rationale for our choice of case study areas, for example, the range of bio-climatic zones. In addition, this multi-regional approach allows us to address contingent regional and local historical/socioeconomic processes; from demographic fluctuations to the development of specific forms of agricultural techniques. Examples of DTM creation, field analyses and selected results will be given from Martleburg in Belgium and sites in Italy. We will then move on to explain how this combination of a comprehensive suite of modern field and laboratory methods and an interpretive strategy informed by the environmental humanities will yield exciting and groundbreaking results.
3D forest model-assisted validation of the Sentinel-2 SNAP fAPAR product
Authors: Origo Niall , Nightingale Joanne , Calders Kim , Disney Mathias
Published: March 2020

fAPAR is a radiometric quantity describing the fraction of photosynthetically active radiation (PAR) absorbed by a plant canopy. It is an important component of carbon cycle and energy balance models and has been named as one of the 50 Global Climate Observing System (GCOS) essential climate variables (ECVs). Space agencies such as the ESA and NASA produce satellite fAPAR products in order to address the need for spatially explicit global data to address environmental and climate change issues. Given the derived nature of satellite fAPAR products it is essential to independently verify the results they produce. In order to do this, validation sites (or networks of sites) are needed that directly correspond to the measurands. Further to this, in order to understand divergences between product and validation data, uncertainty information should be provided with all measurement results.

The canopy radiative transfer models which are used in satellite-derived fAPAR products implement simplistic assumptions about the state of the plant canopy and illumination conditions in order to retrieve an fAPAR estimate in a computationally feasible time. This contribution assesses the impact of the assumptions made by the Sentinel-2 SNAP-derived fAPAR and includes it in a validation of the product over a field site (Wytham Woods, UK), which also has concurrent fAPAR measurements. This is achieved using a 3D model of Wytham Woods which is used to simulate biases associated with specific assumption types. These are used to convert the in situ measurements to the same quantity assumed by the satellite product. The measurement network which provides the fAPAR data is also traceable to SI through sensor calibrations and has associated uncertainty estimates. To our knowledge, these latter points have not been implemented in the biophysical product validation literature, which may explain some of the large discrepancies seen between validation and satellite-derived fAPAR data.

The ultimate aim of this work is to demonstrate a validation framework for derived biophysical variables such as fAPAR which properly considers the quantity estimated by the satellite and that measured by the in situ sensors, whilst providing metrologically derived uncertainties on the in situ data. This will help to properly inform users as to the quality of the data and determine whether the GCOS requirements set for fAPAR are attainable, ultimately improving carbon cycle and energy balance estimates.
Uncertainty in soil hydraulic properties limits the predictability of global water and carbon dynamics
Authors: Paschalis Athanasios , Bonetti Sara , Moustakis Yiannis , Fatichi Simone
Published: March 2020

Water transport at the land surface and in the soil – the critical zone - is highly dependent on the soil hydraulic properties. Such properties influence simultaneously the terrestrial water and carbon cycles as they determine the water fluxes in the soil and the soil’s water holding capacity, ultimately affecting runoff production, groundwater recharge, and the amount and temporal variability of plant available water (i.e. plant water stress). Despite their paramount importance, limited global information concerning the spatial distribution of soil hydraulic properties currently exists. Information at the global scale, commonly used in Earth System Models, mostly originates from pedotransfer functions (PTFs). PFTs are empirical relations that express the dependence of soil hydraulic properties on easily measured attributes as soil properties. Several PFTs currently exist, which adopt different formulations, spanning from simple linear regressions to elaborate machine learning, and are trained with different datasets, yielding different soil hydraulic properties for the same soil texture.   

The question we ask in this study is: how does uncertainty in the soil hydraulic parameters propagate in global ecosystem responses? To achieve this, we deploy a numerical experiment covering many different ecosystems. The terrestrial ecosystem model T&C is used to model energy, water, and carbon dynamics at 80 locations worldwide, spanning all climatological regimes, major biomes and soil types. Soil hydraulic properties at each site were estimated using six widely used PTFs starting from local soil textural information. Uncertainty propagation from soil hydraulic properties to modelled ecosystem dynamics was evaluated for all sites and its dependence on soil textural properties and local topography was quantified.

Our results highlight that uncertainty propagation from hydraulic properties to ecosystem dynamics is much stronger for hydrological fluxes (e.g. infiltration, groundwater recharge and runoff production) than carbon dynamics (e.g. gross and net primary productivity and leaf area dynamics) or energy fluxes (net radiation, sensible and latent heat). Uncertainty in hydrological fluxes can be up to 400% using different PTFs, whereas uncertainties in carbon and energy fluxes are typically less than 20%. The largest uncertainties were observed for slow draining soils, containing large fractions of clay, located in regions with intermediate values of wetness (i.e. annual precipitation ≈ annual potential evapotranspiration). Complex topographic features further enhance the role of uncertainty in soil hydraulic properties. Lateral water redistribution affects both runoff production and soil moisture dynamics increasing the effects on both hydrological and carbon dynamics.
Responses of Mediterranean-climate vegetation to drought and climate change across scales in California
Authors: Dong Chunyu , MacDonald Glen , Okin Gregory , Gillespie Thomas
Published: March 2020

California's climate is projected to have more droughts and heatwaves in the future. A combination of heat and drought stress may significantly affect vegetation health of the Mediterranean ecosystems than drought stress alone. Based on multi-source remote sensing and surface data, we investigated the impacts of drought and climate change on the Mediterranean-climate vegetation of California at different scales, i.e. the entire state, southern California, and Los Angeles urban area. For entire California, we find that a hydroclimatic dipole regulated by El Niño-Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) intensifies the aridity in southern California compared to the north. At a regional scale of southern California, we utilized a bootstrapping regression model to analyze the geographical influences on the relationships between vegetation and drought. Results suggest a warmer climate can significantly increase vegetation sensitivity to drought. In addition, soil texture and elevation seem to also play an important role in adjusting the wildland vegetation susceptibility to drought. In the Los Angeles urban area, we find socioeconomic conditions is the decisive influence in intensifying or mitigating the vegetation response to water-scarce seasons and years. The projected hotter climate in the 21st century may reshape the future landscapes of the coupled human-natural system in California by exacerbating drought severity and duration, differentiating mortality, and increasing wildfires.
Space weather at Mercury as observed by the THEMIS telescope from Earth
Authors: Dósa Melinda , Mangano Valeria , Milillo Anna , Massetti Stefano , Bebesi Zsofia , Timár Anikó
Published: March 2020

The dynamic changes of Mercury’s Na exosphere are investigated here, in relation to space weather conditions. Sodium plays a special role in Mercury’s exosphere: due to its strong resonance D lines at 5890-95Å it has been observed and monitored by Earth-based telescopes for decades. Different and highly variable patterns of Na-emission have been identified. In addition to the release processes already studied extensively in the past, we aim here to investigate the following factors more in detail: the distance to the Sun, position in relation to the ecliptic plane and solar wind magnetic field strength and direction. In order to better investigate the relationship of these factors, we have studied the intensity of Na-emission as a function of solar wind dynamic pressure and TAA of Mercury by means of the extended dataset images collected from 2009 to 2013 by Earth-based observations performed at the THEMIS solar telescope. Solar wind velocity and density values are propagated with the magnetic lasso method to the position of Mercury from nearby space probes and compared with Na emission intensity. Data of either ACE or one of the two STEREO spacecraft were used, depending on which spacecraft had a smaller angular distance to Mercury. Single cases are studied qualitatively, and a longer-term quantitative comparison is shown, including further parameters (solar wind magnetic field strength and direction, TAA).
Socio-hydrological approach to understand conflict and cooperation dynamics in transboundary rivers
Authors: wei jing , Ghoreishi Mohammad , Souza Felipe , Lu You , Tian Fuqiang
Published: March 2020

Transboundary river basins share a complex network of environmental, economic, political, social and security interdependencies. Consequently, transboundary river systems are characterized by evolving conflict and cooperation dynamics between riparian states. The current literature on transboundary watersheds does not identify the key feedback loops between interconnected political, cultural, institutional and socioeconomic factors. This work compares sociohydrological models of three transboundary rivers (Nile River, Columbia River, and Lancang-Mekong River) with distinct characteristics in terms of hydrological processes and socioeconomic conditions. Conflict/cooperation dynamics within these three models were found to be driven by hydrological regime, economic benefits, power imbalance and institutional capacity. By comparing the contextual factors of the emergent conflict/cooperation dynamics across these three river basins, our synthesis study aims to present a general framework that explains how conflict/cooperation dynamics emerge from the interaction between human and hydrological systems.
Molecular fossils inferring Quaternary sea-level changes
Authors: Conti Martina , Bates Martin , Barlow Natasha , Preece Richard , Penkman Kirsty , Keely Brendan
Published: March 2020

Targeted analysis of organic matter in soils and sediments is useful for evaluating past environmental conditions, as specific compounds may be directly linked to organisms and hence to the conditions in which they inhabited the environment.  Variations in molecular fossil distributions have become a powerful tool for understanding changes in palaeoclimate conditions.  This work uses molecular fossils to give an insight into the impact of transgressive events on primary producers inhabiting the studied basin, and hence a more detailed record of sea-level change.

The cores studied consisted of unconsolidated immature sediments from the mid-late Pleistocene (< 500,000 years) and the Holocene.  Molecular fossils, such as chlorophyll pigments and lipids, exhibit fluctuations as a response to changes in palaeoenvironmental conditions, providing a useful marker for sea-level changes.  Fluctuations in the pigment and n-alkane distribution reflect changes in primary producer activity, while the GDGT-based index of branched and isoprenoid tetraether lipids (BIT) differentiates between terrigenous and marine organic matter inputs.  Lipids were analysed by GC-FID and HPLC-MS while analysis of chlorophyll pigments was carried out using a new UHPLC-DAD method.

The results from biomarker analyses show excellent time-resolved agreement with previous lithological and ecological studies, but enabled a more sensitive response of different primary producers to changing conditions to be observed.  The molecular fossils were able to detect the onset and cessation of the studied transgressions earlier than it was possible with microfossil evidence.  Linking the pigment and lipid record with more secure dating will enable a more accurate record of Quaternary relative sea-level change.