bluuebunny/crossref_metadata_2025 huggingface dataset:
SiDroForest  Siberian Drone-mapped Forest inventory
Authors: van Geffen Femke , Heim Birgit , Herzschuh Ulrike , Pestryakova Luidmila , Zakharov Evgenii , Hänsch Ronny , Demir Begüm , Kleinschmit Birgit , Förster Michael , Kruse Stefan
Published: March 2021

To gain a better understanding of global carbon storage and albedo feedback mechanisms it is important to have insights into high latitude vegetation change. Boreal forest compositions are changing in response to changes in climate, which in turn can lead to feedbacks in regional and global climate through altered carbon cycles and albedo dynamics. Circumpolar boreal forests represent close to 30% of all forested area on the planet, between 900 and 1,200 million ha. These forests are located primarily in Alaska, Canada, and Russia. Due to the remote location of these forests and the short seasons without snow, data collected on the boreal vegetation is limited. 

The proposed dataset is an attempt to remedy data scarcity whilst providing adjusted data for machine learning practices.We present a dataset containing diverse formats of forest structure information that covers two important vegetation transition zones in Siberia: the Evergreen - Summergreen transition zone in Central Yakutia and the northern treeline in Chukotka (NE Siberia).

This dataset contains data from the locations covered by fieldwork was performed by the Alfred Wegener Institute for Polar and Marine research, (AWI) and the North-Eastern Federal University of Yakutsk​ (NEFU). The fieldwork upscaled through the addition of Red Green Blue(RGB) UAV (Unmanned Aerial Vehicle) camera data and Sentinel-2 satellite data cropped to a 5 km radius around the fieldwork sites. The dataset is created with the aim of providing ground truth validation and training data to be used in various vegetation related machine learning tasks .

The dataset contains:

1.Labelled individual trees per 30x30 m plot assigned in field work with additional data on species, height, crown width, and biomass.

2.Structure from Motion (SfM)point clouds that provide 3D information about the forest structure, included generated Canopy Height Model (CHM), Digital Elevation Model (DEM) and a Digital Surface Model (DSM) per 50x50 m.

3.Multispectral Sentinel-2 satellite data (10 m ) cropped to a 5km radius with generated a NDVI(normalized difference vegetation index), available in three seasons: Early Summer, Peak Summer and Late Summer.

4.Extracted tree crowns with species information and a synthetically generated large (10.000 samples) dataset for training machine leaning algorithms.

The dataset will be made publicly available on the data repository PANGAEA.
New high precision U-Pb CA-ID-TIMS zircon ages from the Ediacaran in Namibia
Authors: Messori Fabio , Linnemann Ulf , Hofmann Mandy , Zieger Johannes , Geyer Gerd , Vickers-Rich Patricia , Ovtcharova Maria
Published: March 2021

The Ediacaran records a transition from a planet largely dominated by microscopic organisms to macroscopic multicellular organisms during the Phanerozoic. Temporal calibration of the record of changing climates and coevally diversifying biota is crucial to understand how metazoan life gained an early foothold on Earth.

A causal link between climate-driven environmental perturbations and biotic changes is generally accepted. However, a chronological relationship is needed to prove which event acted as a trigger for the biological turnover, i.e. extinction or the development of new organizational levels. A connection between environmental perturbations associated with the appearance and disappearance of the Ediacaran biota is profoundly complicated because of the scarcity of available geochronological and chemostratigraphical records. Therefore, it is crucial to expand existing datasets for this period, particularly through additional chronology.

The Nama Group in southern Namibia serves as a unique archive for major geobiological changes across the Ediacaran–Cambrian transition exemplified by a near complete section through the terminal Ediacaran. The region exposes the full stratigraphic range of the Nama assemblage and records several environmental perturbations. Establishing a precise timeframe of the terminal Ediacaran environmental and biological changes in Nama group enables a much-enhanced understanding of the nature and rates of the evolutionary changes.

Following pioneering research by Grotzinger et al. (1995), the Ediacaran–Cambrian boundary in Namibia has recently been dated ca. 2 Ma younger than previously assumed [1]. Additional high-precision U-Pb CA-ID-TIMS zircon ages from silicified tuffs of the Nama Group allow additional insights for the timeframe of the entire terminal Nama. Our results indicate that (i) the oldest ash bed in the Zaris subbasin is 547.3 Ma old, which makes it more than 0.5 Ma younger than the previously dated tuff in the same subbasin; (ii) a newly explored section at the base of the terminal Ediacaran Spitskop Member near the MTC tower (Witpütz Nord farm) revealed a slightly younger age of 539 Ma, which permits a precise correlation of this section with the Swartpunt section and indicates the position of the Ediacaran-Cambrian boundary.

[1] Linnemann, U. et al., (2019) Terra Nova 31(1) 49-58.
Long-term observations of δ13C-CO2, δ18O-CO2, δ17O-CO2 and “excess” 17O-CO2 by Quantum Cascade Dual-Laser Absorption Spectrometry in whole air flask samples from Lutjewad station, the Netherlands
Authors: Steur Farilde , Scheeren Bert , Peters Wouter , Meijer Harro
Published: March 2021

We present long-term results of δ13C-CO2, δ18O-CO2, δ17O-CO2 and “excess” 17O-CO2 or Δ17O-CO2 measurements in whole air flask samples collected at Lutjewad monitoring station in the Netherlands using an Aerodyne Quantum Cascade Dual-Laser Spectrometer system (QCDLAS). The station is located at the Dutch Wadden sea coast (6.353°E, 53.404°N) in a rural environment. The flask samples have been collected at 60 m altitude at a bi-weekly rate, spanning from July 2016 until the end of 2020. The location of Lutjewad station allows to measure clean marine background air from the north-northwest (~15% of the time) in contrast to continental air from a prevalent south-westerly direction (~50% of the time). Our observations include the summers of 2018 and 2019 which saw exceptionally hot and dry conditions in large parts of Europe, including the Netherlands.

The Δ17O-CO2 anomaly is defined as the deviation from normal mass dependent fractionation reflected in CO2 equilibrated with water, occurring over water bodies, but mainly in plant leaves. Atmospheric Δ17O-CO2 has been used as a parameter to study gross primary production (GPP), notably as a function of water availability. Here, the determination of Δ17O-CO2 is derived from the direct measurement of δ17O-CO2 next to δ18O-CO2 (Δ17O = ln(δ17O +1)-0.5229×ln(δ18O +1)). Using the summer 2018 and 2019 results we investigate the potential of using the Δ17O-CO2 signal derived from QCDLAS measurements from Lutjewad as a tracer for suppressed plant assimilation due to water stress.
High-resolution topography of the uplifting Huon Peninsula (Papua New Guinea) reveals high interstadial sea-levels over the past ~400 ka
Authors: de Gelder Gino , Husson Laurent , Pastier Anne-Morwenn , Chauveau Denovan , Fernández-Blanco David , Pico Tamara , Authemayou Christine , Pedoja Kevin
Published: March 2021

Quaternary sea-level curves provide crucial insights to constrain tectonic and climatic processes, but require calibration with geological constraints that are particularly scarce for cold periods prior to the last glacial-interglacial cycle. To derive such constraints, we re-visit the Huon Peninsula in Papua New Guinea, which is a classic coral reef terrace (CRT) site that was used for the earliest relative sea-level (RSL) curves. We use digital surface models calculated from 0.5m Pleiades satellite imagery to improve RSL constraints, and unlike previous studies, we find that large-scale tilting of the terrace sequence is generally N-directed. This implies that RSL estimates are several meters higher than previously thought for most highstands over the past ~125 ka. We use the large-scale geometry of the terrace sequence to estimate sea-level highstands up to ~400 ka, and our results suggest that global mean sea-level curves derived from oxygen isotopes consistently underestimate sea-level during the relatively cold Marine Isotope Stages 3, 5a, 5c, 6, 9a and 11a, up to ~10-20 m. We use coral reef models to show that our age interpretation is consistent with the overall terrace sequence morphology, and fits between models and topography improve when adjusting sea-level highstands according to our findings.
Representation of model error through process-based perturbations for ensemble prediction : application to turbulence and shallow convection parametrisations
Authors: Fleury Axelle , Bouttier François
Published: March 2021

The boundary layer is the place of many complex physical processes spanning various time and space scales, part of which need to be parametrised in NWP models. These parametrisations are known sources of uncertainty in the models, due to the difficulty of accurately representing the processes, and the resulting simplifications and approximations that have to be done. Model uncertainty is part of what ensemble prediction systems seek to represent. This can be achieved in particular by using stochastic perturbation methods, where noise is introduced during model computations to change its state and produce different simulations. Well-known and widely used perturbation schemes like the Stochastically Perturbed Parametrisation Tendencies (SPPT) scheme have shown their effectiveness and their interest in building ensembles. However, part of the model uncertainty is not yet well represented in current ensemble systems, while some of the assumptions made by SPPT can be questioned. This argues for a diversity of approaches to represent model errors. In this active research field, alternative perturbation methods are investigated, such as the Stochastically Perturbed Parametrisations (SPP) method, or other methods focusing on the perturbation of particular physical processes. The work presented here focuses on the last ones. Based on two examples of methods published in the literature, perturbations have been applied to the turbulence and shallow convection parametrisation schemes of the mesoscale NWP model Arome from Météo-France. The perturbation of turbulence is based on the use of subgrid-scale variances to regulate the amplitude of an additive noise, while shallow convection is perturbed through a stochastic closure condition of the scheme. A simplified 1D framework has been used, in order to assess the ability of the method to produce an ensemble with sufficient dispersion and to compare its results with those from existing methods like SPPT.
An integrated thermo-compositional model of the African cratonic lithosphere from gravity and seismic data
Authors: Finger Nils-Peter , Kaban Mikhail K. , Tesauro Magdala , Mooney Walter D. , Thomas Maik
Published: March 2021

The presented model describes the lithospheric state of the cratonic regions of Africa in terms of temperature, density and composition based on joint analysis of gravity and seismic data. In addition, a new model of depth to the Moho was calculated from available seismic data. It was then used in combination with data on topography, sediments, and deep mantle anomalies to obtain residual mantle gravity and residual topography. These residual fields were corrected for thermal effects based on S-wave tomography and mineral physics constraints, assuming a juvenile mantle. Afterwards, the thermally corrected fields are jointly inverted to uncover potential compositional density variations. Following the isopycnic hypothesis, negative variations in cratonic areas are interpreted to be caused by iron depletion. Adapting the initially juvenile mantle composition allows to iteratively improve the thermal and compositional variations, culminating in a self-consistent model of the African lithosphere. Deep depleted lithospheric roots exist under the Westafrican, northern to central Congo, and Zimbabwe Cratons. The temperatures in these areas range from below 800 °C at 100 km depth to 1200 °C at 200 km depth. Higher temperatures and absence of depletion at depths below 100 km in wide areas of the eastern to southern Congo and the Kaapvaal Cratons indicate a thinner and strongly reworked lithosphere.
Collision and reactivation along the South Tianshan Orogen (NW China) through late Paleozoic to Mesozoic time
Authors: Han Yigui , Zhao Guochun
Published: March 2021

The South Tianshan Orogenic Belt in NW China marks the suturing site between the Tarim Craton and the Central Asian Orogenic Belt (CAOB) during late Paleozoic-Mesozoic time. Despite numerous investigations, the amalgamation history along the South Tianshan Orogen remains controversial, especially on the timing and process of the final continental collision between the Tarim Craton and the Central Tianshan (CTS)-Yili Block. We inquire into this issue on the basis of a compiled dataset across the Tarim, South Tianshan and CTS-Yili regions, comprising elemental and isotopic data of magmatic rocks and radiometric ages of regional magmatism, detrital zircons, (ultra-)high pressure metamorphism and tectonothermal events. The data support a continental collision along the South Tianshan belt in 310-300 Ma, in accord with a contemporaneous magmatic quiescence and a prominent decrease of εNd(t) and εHf(t) values of magmatic rocks in the CTS region, and a main exhumation stage of (U)HP rocks in the South Tianshan region. The collisional orogeny along the South Tianshan have most likely been influenced by a mantle plume initiated at ca. 300 Ma underneath the northern Tarim Craton, as evidenced by temporal and spatial variations of geochemical proxies tracing magma source characteristics. The new model of plume-modified collision orogeny reconciles the absence of continental-type (U)HP rocks in the orogen and the insignificant upper-plate uplift during continental collision. In the mid-Triassic (ca. 240 Ma), the Chinese western Tianshan underwent intense surface uplift and denudation, as indicated by sedimentary provenance analysis and tectonothermal events. Paleocurrent and detrital zircon age data from Triassic strata in northern Tarim suggest a provenance change from a single source of the Tarim Craton to multiple sources including the CTS-Yili Block to the north and the Western Kunlun Orogen to the south. We suggest that the mid-Triassic uplifting in Chinese western Tianshan was an intracontinental orogeny caused by far-field effects of the collision between the Tarim Craton and the Qiangtang Block. This research was financially supported by NSFC Projects (41730213, 42072264, 41902229, 41972237) and Hong Kong RGC GRF (17307918).
Drying out conifers classification employing TripleSat satellite data
Authors: Litvinovich Hleb , Guliaeva Sviatlana , Bruchkouski Ilya , Siliuk Volha , Katkouski Leanid
Published: March 2021

Drying out of coniferous trees (Picea abies) due to bark beetle infestation and other diseases leads to a high rate of conifers mortality. The coniferous forests in Belarus are largely exposed to damage by the bark beetle, the early symptoms of which are the changes in the color and loss of shine of the needles.  

Purpose of the work is to identify drying out stages combining the TripleSat multispectral satellite data (spatial resolution 3.2 m MS, 0.8 m PAN, bands R, G, B, NIR) for the test coniferous forest area in Belarus (53.65419º N, 27.640213º E) with quasi-synchronous airborne photo-spectral measurements which have been used as a reference data. Airborne measurements of reflectance coefficient function of underlying coniferous trees have been carried out by employing two spectrometers (wavelength range 400-900 nm, spectral resolution 4.3 nm) and photo-camera (visible range, FOV 50º) mounted on board of Diamond DA40NG aircraft in nadir geometry.  

Airborne RGB-images have been used for visual identification of the type of underlying surface and for subsequent training data set formation. Training data consist of several sets (10 – 20) of vegetation indexes for each type of underlying surface. The linear discriminant analysis (LDA) classification algorithm has been applied in this study for distinguishing the conifers drying out stages. A set of vegetation indices evaluated for each reflectance coefficient function has been applied as input data for LDA classification algorithm.

LDA classification algorithm has been employed to the TripleSat image for identification drying out stages of coniferous trees. The reference data for LDA classification algorithm of the TripleSat image included the combination of coordinates and corresponding types of underlying surface obtained from the results of the airborne experiment classification. A set of vegetation indices has been derived for each pixel of the image and used as input data for LDA algorithm; also vegetation indices calculated for the reference pixels have been applied for training data set formation.

The classification accuracy of three conifers drying out stages based on the airborne experiment is estimated to be in a range of 27 - 74%. The verification of TripleSat classification results has been performed by visual comparison with high resolution aerial images.
Evolution of chemical weathering processes and CO2 sequestration in the glaciated basins of Western Himalayas
Authors: biswal Kalyan , kumar Naveen , soheb Mohd , al Ramanathan
Published: March 2021

Understanding of chemical weathering process involved in ionic elution helps in distinguishing the CO2 sequestration rate at the different micro-climatic setup of Himalayan catchments. In the present study, we have selected three glaciated basins from two different climatic zones of Western Himalayas (Lato and Phutse from the cold-arid zone of Ladakh and Chhota Shigri from the monsoon-arid zone of Himachal Pradesh, India) for determining various solute sources, CO2 sequestration rate and its control over melt-water quality. Solute sourcing models used in this work shows major cations like Ca2+  and Mg2+ are from crustal rock-weathering while Na+ and K+ sourced out from the sea-salt origin. However, major anions like SO42- (> 85%) were derived from the crustal origin and HCO3- mostly derived from atmospheric sources (39% to 45 %) in all catchments except HCO3- contribution from carbonation dissolution and silicate weathering is ~29% and ~16% for Ladakh catchments compared to ~9 % and ~29% in Chhota Shigri respectively. The solute model also reveals that the contribution of sulphate oxidative mediated carbonate dissolution (SOCD) in HCO3- flux is relatively higher in Chhota Shigri (~16%) than others (~9%). It is also observed that catchment like Chhota Shigri having a combined network of channelized and distributed drainage patterns with lower specific discharge, more glacierized area, low pH, high pCO2, Low molar ratio [Ca2+ + Mg2+]/[ Na+ + K+], high SMF (~ 0.4), low CO2 carbonate/CO2 silicate ratio (~1.3) show relatively more sulphide oxidative and silicate weathered products than other catchments. Conversely, presence of excess non-glaciated areas in Stok and Phutse having well-channelized subsurface discharge with high CO2 carbonate/CO2 silicate ratio (~10 to ~5) show enhanced carbonation via atmospheric CO2 (CAC) and carbonate dissolution with high annual CO2 sequestration. Thus, varying subglacial drainage system, specific discharge pattern and reactive rock-types with distinct hydro-micro-climatic set up alters the chemical weathering mechanism in these catchments and control meltwater quality.
Impact of the stochastic model of the ocean tides on GRACE monthly gravity field solutions
Authors: Panafidina Natalia , Koenig Rolf , Neumayer Karl , Dahle Christoph , Flechtner Frank
Published: March 2021

In GRACE data processing the geophysical background models, which are needed to compute the monthly gravity field solutions, usually enter as error-free. This means that model errors could influence and distort the gravity field solution.

The geophysical models which influence the solution the most are the atmosphere and ocean dealiasing product (AOD1B) and the ocean tide model. In this presentation we focus on the ocean tide model and on incorporating its stochastic information in data processing.

We use the FES2014 ocean tide model presented as a spherical harmonic expansion till degree and order 180. The information about its uncertainties and the correlations between different spherical harmonics is provided by the research unit NEROGRAV (New Refined Observations of Climate Change from Spaceborne Gravity Missions). In a first step, the stochastic properties of the tide model are considered to be static and are expressed as variance-covariance matrices (VCM) of the spherical harmonics of the 8 main tidal waves till degree and order 30. The incorporation of this stochastic information is done by setting up the respective ocean tide harmonics as parameters to be solved for. Since ocean tides cannot be freely estimated within monthly GRACE solutions, the provided VCMs for the 8 tidal waves are used for constraining the tidal parameters.

This procedure was used to compute monthly gravity field solutions for the year 2007. For a comparison, we computed also monthly gravity fields without taking into account the stochastic information on ocean tides. In this contibution we present and discuss the first results of this comparison.
Energetic electron precipitation via oblique whistler mode chorus emissions in the outer radiation belt
Authors: Hsieh Yikai , Omura Yoshiharu
Published: March 2021

Whistler mode chorus emissions in the Earth’s magnetosphere cause energetic electron precipitation and the associated pulsating aurora. First-order cyclotron resonance in parallel whistler mode wave-particle interactions is the main mechanism of the precipitation. Not only cyclotron resonance but also Landau resonance and higher-order cyclotron resonances occur in the oblique whistler mode wave-particle interactions. Especially, electrons can be accelerated and scattered to lower equatorial pitch angles rapidly via Landau resonance. We apply test particle simulation and the Green’s function method to check the energetic electron precipitation caused by oblique chorus emissions. We simulate the wave-particle interactions around L=4.5 for electron ranges from 10 keV to a few MeV. We further compare the precipitation fluxes between parallel and oblique chorus emissions. Our simulation result reveals that oblique chorus emissions lead to more electron precipitation than parallel chorus emissions. At kinetic energy E < 100 keV, the electron precipitation ratio (oblique case/parallel case) is about 1.3. At 100 keV < E < 0.5 MeV, the ratio is greater than 2. At E > 0.5 MeV, the ratio is greater than 2 orders. Multiple resonances effect in the oblique whistler mode wave-particle interactions is the reason for the greater precipitation.
The role of methane transport from the active layer in sustaining methane emissions and food chains in subarctic ponds
Authors: Olid Carolina , Zannella Alberto , Lau Danny C.P.
Published: March 2021

Shallow groundwater flow from the seasonally thawed active layer is increasingly recognized as an important pathway for delivering methane (CH4) into Arctic lakes and streams, but its contribution to CH4 emissions from thaw ponds has not been evaluated. Furthermore, the potential influence of the shallow groundwater-derived CH4 on the trophic support and nutritional quality of thaw pond food chains remains unexplored. In this study, we used a radon-mass balance approach to quantify the CH4 transport from the active layer into thaw ponds in a sub-Arctic catchment. We analysed stable isotopes and fatty acids of pond macroinvertebrates to evaluate the potential effects of CH4 inputs through active layer groundwater flows on the aquatic food chains. Our results indicate that CH4 fluxes from the active layer can sustain CH4 emissions from the ponds. Consumers in ponds receiving greater CH4 inputs from the active layer had lower stable carbon isotope signatures that indicates a greater trophic reliance on methane oxidizing bacteria (MOB), and they had lower nutritional quality as indicated by their lower tissue concentrations of polyunsaturated fatty acids. Accurate predictions of CH4 release from small thaw ponds will thus require improved knowledge of the contributions from various processes including internal production, flow paths of active layer groundwater, and MOB-consumer interactions.
Global soil mapping with Neural Networks 
Authors: Genova Giulio , de Sousa Luis , Mimmo Tanja , Borruso Luigi , Poggio Laura
Published: March 2021

High quality global soil maps are crucial to face several challenges such as reducing soil erosion, climate change adaptation and mitigation, ensuring food and water security, and biodiversity conservation planning. To obtain accurate and robust soil properties maps, research and development are necessary to identify the most appropriate prediction models and to develop efficient and robust workflows. A few recent studies used Artificial Neural Networks (ANN) in Digital Soil Mapping, in some cases improving the accuracy of the predicted maps compared to other methods like Random Forest (RF). In this study we tested different ANN architectures on a global top-soil dataset of ca. 110 000 samples, comparing the results for the different architectures with the more traditional approach of RF. The target variables considered are pH, Soil Organic Carbon, Sand, Silt, and Clay. We selected 40 environmental covariates from a pool of over 400 to represent the most important soil forming factors. We tried simpler architectures (single input – single target) using point observations for one target variable with corresponding raster cell values for spatially explicit environmental covariates. We also used more complex architectures (multi input - multi target) incorporating contextual information surrounding an observation (convolutional) and with multiple target variables. Preliminary results show that increasing the number of hidden layers in the neural network does not significantly influence the results, while changing the type of architecture can play a bigger role in the overall accuracy of the model. The overall prediction accuracy of the ANN was comparable with the RF model. We conclude that ANN are a promising, relatively new, approach for Global Digital Soil Mapping and that further research is needed to improve performance.
Clogging mechanisms of filter barriers against debris-flow hazard
Authors: Mauro Filippo , Leonardi Alessandro , Pirulli Marina
Published: March 2021

Debris flows are amongst the most hazardous landslide phenomena (Jakob & Hungr, 2005). They are mixtures of flowing water and granular materials, which range in size from microscopic soil particles to massive rock boulders. Due to their unpredictability and rapidity, they pose severe hazard on infrastructure, structures, and human lives. To dissipate the destructive kinetic energy of debris flows and induce deposition of the coarsest fraction of the flow, mitigation systems often include the use of filter barriers. Filter barriers are built both in steel and reinforced concrete, and their openings should be designed according to a reference grain diameter. This key parameter is often chosen arbitrarily due to the difficulties in considering the full grain size distribution of the deposit. Sufficiently small outlets, however, leads to premature clogging of the barriers, blocking further outflow (Ashour et al., 2017). This can result in excessive maintenance costs.

This work focuses on the clogging mechanism of three different kinds of filter barriers: nets, slit dams, and slot dams. The aim is to evaluate the influence of grainsize dispersity into the clogging/non-clogging transition. Starting from simpler monodisperse granular material, we determine via DEM simulations the particle diameter D that induces clogging in the openings, as a function of the opening size S. Thus, for monodisperse grains, a set of threshold values for S/D can be detected: on one side of the threshold the particles are too small to clog the opening, on the other side they are too large to allow free passage of the material.

However, natural debris deposits are far from uniform. To analyse the role of grainsize dispersity, bidisperse specimens are created mixing grains with two different diameters: a small diameter and a large diameter. By varying the composition of large and small particles, a transition is observed between clogging and free-flow, in analogy with what obtained in the simulation with monodisperse grains. The comparison of results obtained with bidisperse and monodisperse samples indicates that an analogy in terms of trends and thresholds exists, as long as an equivalent diameter D* is introduced for bidisperse mixtures (Marchelli, 2018). This parameter is therefore suggested as the reference diameter to be adopted in the barrier design.
Implementation of watershed modelling in the Litter-TEP service (Marine Litter Drift Monitoring in the NE Atlantic Shelf Region) to complement CMEMS data inputs.
Authors: Gunti Quentin , Vallette Anne , Coulibaly Fatimatou
Published: March 2021

It has been considered for quite a while that rivers, coastal outlets and flytipping are the main input contributors to Marine litter. After their discharge into the sea, litter is then transported by currents and wind while sunk and/or disintegrated into micro marine litter, some pieces finishing their course at the coast where they wash ashore. Thanks to a Copernicus Marine Environment Monitoring Service (CMEMS) grant, ARGANS Ltd has developed a web-based service, called Litter-TEP, that aims to track marine litter from their source. The service is based on two segments, one Land unit and one Ocean unit, and the issue is with the former: The Land component is made of a parametric model of riverine macro litter discharge at sea which is based on hydrological information and socio-economics data. It feeds the Ocean unit, with drift models using ocean current, wave and wind forecasts from CMEMS to provide a 5-day running forecast of macro-litter density in the sea, potential beach stranding at the coast and, inversely, where a beach litter event is identified to provide the likelihood of where the litter entered the sea. Yet, by lack of real-time land hydrological data from free & public sources, the land-litter input model currently implemented in the service only relies on hydrological information from statistics based on 30 years of daily rivers flow data. Nota: if the hydrological data (river flows) is in open access for the European rivers on the Copernicus service, it is with a 30-day delay. To mitigate this shortage, we have implemented a water discharge model as a prototype; it is based on HYPE v.5.11.2 from SMHI to calculate daily estimation of rivers flow from near real time rainfall (from NASA) & temperature data (from all national Met Offices) and thus to link the volume of litter coming into the sea to Meteorological events to have better estimates of litter’s volume brought into the sea. The model has been validated for Ireland and is currently parametrized for other countries and regions. It shall be implemented in the next version of the LITTER-TEP.
Statistically downscaled climate projections as a support for adaptation tools
Authors: Tomozeiu Rodica , Monti Roberta , Nerozzi Fabrizio
Published: March 2021

ADRIADAPT is a project inside the framework of the Italy-Croatia Interreg Cooperation Programme. Focused to contrast impacts over Adriatic coastal areas, which are particularly exposed to climate changes, it aims to provide a resilience information platform, suitable for performing vulnerability analysis and making decisions. In this work, climate projections are computed for some Emilia-Romagna coastal areas throughout a statistical downscaling scheme, based on the canonical correlation analysis between local climate indices (predictands) and large-scale fields (predictors). Firstly, the scheme has been calibrated and validated at a seasonal time scale for minimum and maximum temperature, tropical nights, heatwave duration, frost days, obtained by the ERACLITO observation gridded dataset for Emilia-Romagna, and large-scale fields (mean sea level pressure, 500hPa geopotential height, and 850hPa temperature) of the ECMWF-ERA40 and ERA-interim re-analysis data set. Calibration is performed over the 1961-1985 and 2006-2010 periods, while validation concerns the 1986-2005 period. Correlation coefficients, bias, and root mean square errors are taken as skill measures. Secondly, large-scale field data simulated by four global climate models from CMIP5 experiments (CMCC-CM, MPI ESM-MR, CNRM -CM5, Can-ESM2) in the framework of two emission scenarios (RCP4.5 and RCP8.5) has been treated as input to the statistical downscaling scheme to obtain local climate indices for the next four 20-year periods: 2021-2040, 2041-2060, 2061-2080, 2081-2100. Changes respect to the 1986-2005 period, taken as climatic reference, are evaluated. A Poor Man’s ensemble technique is applied to reduce uncertainties and give more statistical robustness to the results. The minimum and maximum temperature projections show a significant increase could be expected to occur for all seasons and both RCPs. The magnitude of changes is higher for the maximum temperature, especially during the summer season when changes up to 4°C for RCP4.5 and 8°C for RCP8.5 are expected at the end of the century. As regards extreme temperature indices, the seasonal tropical nights and heatwaves duration are projected to increase while frost days to decrease over all the four-time periods and for both emission scenarios.
This work has been performed in the framework of Italy-Croatia Interreg Cooperation Programme – ADRIADAPT Project (https://www.italy-croatia.eu/web/adriadapt/).
Greenhouse gas dynamics in drained peatlands: CH4 and N2O fluxes from tree stems and soil
Authors: Ranniku Reti , Schindler Thomas , Lehtme Eliisa , Mander Ülo , Machacova Katerina , Soosaar Kaido
Published: March 2021

Peatland soils are considered the dominating source of nitrous oxide (N2O) and methane (CH4) to the atmosphere. However, there are high spatio-temporal uncertainties regarding the budgets of these greenhouse gases (GHG) from peatlands due to complex dynamics between the chemical, physical and biological variables occurring in the soil. GHG fluxes from peatland soils are relatively well studied, however, tree stems have received far less attention and are often overlooked in GHG models and assessments. It is necessary to study relationships between stem and soil fluxes, and their chemical, physical and biological drivers to understand the fluxes' origin.

Our ongoing project focuses on measuring GHGs from tree stems and soil in the Agali Birch Forest Research Station in Estonia, representing a drained peatland with Downy Birch (Betula pubescens) and Norway Spruce (Picea abies) trees. Twelve representative sub-sites were selected in the study area. One half consist of an adjacent set of a Downy Birch and a Norway Spruce tree with manual tree stem chambers, plus one automatic dynamic soil chamber. The remaining sub-sites are set pairs of birch trees and soil chambers. Six birch trees and all six spruce trees have stem chambers installed at 10, 80 and 170 cm above the ground to measure stem fluxes' vertical profile. Chambers on the six remaining birch trees were only installed at the lowest height. During the weekly ongoing sampling campaigns that started in October 2020, we use manual static gas extraction from rigid stem chambers to analyse hourly changes in chamber headspace concentrations of CH4 and N2O. The gas samples are analysed in the laboratory within two weeks of collection using gas chromatography. Automated soil chambers collect CH4 and N2O flux data every two hours per chamber, and a connected Picarro measuring unit analyses the gas samples in-situ.

When extrapolated, our results can help understand stem and soil GHG emissions on an ecosystem level and acknowledge the role of tree stems for local and regional GHG budgets. Within a larger research framework, these GHG flux data will be joined with detailed soil biogeochemistry and microbial dynamics to further improve process-based modelling of peatland GHG emissions. We plan to continue our measurements for one full year to understand the seasonal changes in CH4 and N2O emissions patterns.
First gravity data aquired by the transportable absolute Quantum Gravimeter QG-1 employing collimated Bose-Einstein condensates
Authors: Herr Waldemar , Heine Nina , Musakaev Marat , Abend Sven , Timmen Ludger , Müller Jürgen , Rasel Ernst. M.
Published: March 2021

The transportable Quantum Gravimeter QG-1 is designed to determine the local gravity to the nm/s² level of uncertainty. It relies on the interferometric interrogation of magnetically collimated Bose-Einstein condensates in a transportable setup consisting of a sensor head and an electronics supply unit.
In this contibution we introduce the measurement concept and discuss it's impact on the measurement uncertainty. We are reporting on the first gravity data taken with the device over the course of three days thereby validating the operability and the measurement concept applied in QG-1.
We acknowledge financial support from "Niedersachsisches Vorab" through "Förderung von Wissenschaft und Technik in Forschung und Lehre" for the initial funding of research in the new DLR-SI Institute. Funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany's Excellence Strategy - EXC-2123 QuantumFrontiers - 390837967 and under Project-ID 434617780 - SFB 1464.
Simulation of LGM ice sheets with the Community Earth System Model version 2 
Authors: Bradley Sarah L , Petrini Michele , Sellevold Raymond , Vizcaino Miren , Lipscomb William H. , Georgiou Sotiria
Published: March 2021

The last deglaciation provides as unique a framework to investigate the processes of ice sheet and climate interaction during periods of mass loss as in the current climate. Here we simulate the Last Glacial Maximum (LGM) northern hemisphere ice sheets climate, surface mass balance (SMB), and dynamics with the Community Earth System Model version 2 (CESM2, Danabasoglu et al., 2020)) and the Community Ice Sheet Model version 2 (CISM2, Lipscomb et al., 2019). This LGM simulation will be later used as starting point for coupled CESM2-CISM2 simulations of the last deglaciation.

 

CESM2 is run at the nominal resolution used for IPCC-type projections (approx. 1 degree for all components). The model includes an advanced snow/firn and SMB calculation (van Kampenhout et al, 2019; Sellevold et al, 2019) the land component (CLM, cite) that has been evaluated and applied to the simulation of the future Greenland melt (van Kampenhout et al, 2020, Muntjewerf et al., 2020a,b, Sellevold & Vizcaino, 2020).

 

Our analysis examines how the global, Arctic, and North Atlantic climate result in the simulated radiative and turbulent heat fluxes over the ice sheets, and the mass fluxes from precipitation, refreezing, runoff, and sublimation. We also examine the simulated ice streams in CISM2, which is run at 8 km under a higher-order approximation for ice flow.
Frequency-domain electromagnetic induction inversion with randomized tensor decomposition
Authors: Narciso João , Liu Mingliang , Van De Vijver Ellen , Azevedo Leonardo , Grana Dario
Published: March 2021

Near-surface systems can be complex and highly heterogeneous. The complex nature of these systems makes their numerical modelling a challenging problem in geosciences. Geophysical survey methods combined with direct measurements have been widely used to characterize the spatial distribution of the near-surface physical properties. Within this scope, geophysical inversion has been a preferable tool to predict quantitively the spatial distribution of the relevant near-surface properties. Ensemble-based data assimilation techniques are common geophysical inversion methods used in problems related to subsurface modelling and characterization. These methods allow the accurate prediction of the spatial distribution of the subsurface properties and have the ability to assess the uncertainty about the model predictions. However, these are computationally demanding inversion techniques, which makes their applicability to large data sets prohibitive.

This study presents the application of a computationally efficient ensemble-based data assimilation technique for inversion of a large-scale frequency-domain electromagnetic induction survey data set. The inversion method is based on randomized high-order singular value decomposition. We combine randomized linear algebra with high-order singular value decomposition, which allows to perform data assimilation in a low-dimensional model and data space. This inversion approach satisfies two objectives: it reduces the computational burden of the inversion and has the same characteristics as conventional ensemble-based data assimilation methods. The inversion method presented herein predicts the spatial distribution of subsurface electrical conductivity and magnetic susceptibility from frequency-domain electromagnetic induction data (as related to the in-phase and quadrature FDEM signal components).

The method is illustrated in a three-dimensional real case application where a set of geophysical and borehole data is available. The log-set composed by electrical conductivity and magnetic susceptibility is used as conditioning data to generate a prior ensemble of numerical three-dimensional models with geostatistical simulation. The predicted posterior distribution generates synthetic frequency-domain electromagnetic induction data that reproduces the observed data. The model predictions at a blind well location, not used in the generation of the prior ensemble, agree will with the observed log data, validating the quality of the applied method.
Combining current velocity data from different sources as input to coastal zone management
Authors: Ullgren Jenny , Stene Anne
Published: March 2021

Sustainable development of the aquaculture industry depends on wise coastal zone management.  Aquaculture in Norway is typically found in small, rural municipalities that may lack expertise in marine ecology. In the project “Precise coastal zone planning with focus on aquaculture” we combine marine maps with in situ data and model results to produce a management tool for easier and more efficent aquaculture planning.

Our study area comprises five municipalities in Western Norway and includes both fjords and open coast. High resolution marine maps exist for the area. We also have access to environmental assessments from aquaculture sites, sediment samples for Total Organic Carbon (TOC), and current velocity time series from oceanographic moorings. We will compare the in situ data with output from two current models (Sinmod and NorKyst-800). The data will be used to produce thematic maps of key characteristics, mainly current and organic carbon content, to help administrators identify areas suitable for different types of aquaculture.

Here, we present results from in situ measurements that will provide the current velocity input to the thematic maps. Data from seven oceanographic moorings placed in the fjord system show the current variability on time scales from hours to years. In addition we have done four 1-month deployments of a current profiler on sites selected to improve the geographical data coverage. We show preliminary results and discuss the challenges in simplifying variable current fields in an area with complex geography into an overall map.
Near-inertial wave modulated turbulence in a Kuroshio anticyclonic eddy
Authors: Essink Sebastian , Lien Ren-Chieh , Kunze Eric
Published: March 2021

Storm-generated near-inertial waves are a significant source for deep-ocean mixing. However, their energy pathways beyond wind generation and equatorward propagation as low modes are still elusive. Previous studies suggest that the bulk of inertial wind power is lost in the nearfield of storm forcing, but there is little observational evidence to confirm this.

Finescale horizontal velocity, temperature, salinity and microscale temperature profiles to 500-m depth were collected in the Kuroshio-Oyashio Confluence east of Japan during the storm-seasons of 2016 and 2017 with chi-augmented EM-APEX floats. Temporal sampling was at 1-h resolution during storms, sufficient to resolve near-inertial motions. Turbulent dissipation rates  and diapycnal diffusivities K were inferred from microscale temperature-gradient spectra.  Several floats were trapped near the velocity maximum of anticyclonic eddies.  Mesoscale eddies are known to trap and amplify near-inertial waves and to modulate near-inertial wave distribution and dissipation.

Near-inertial energy-fluxes within the eddy are mostly inward and downward. Signatures of a critical layer, e.g., increasing vertical wavenumbers, shear, and turbulence are present at the depth where the eddy vorticity approaches the surface value, and strong vertical mean shears and vorticity-gradients occur. Turbulence is reduced by a factor of 10 above 180-m depth, despite elevated near-inertial energy, and enhanced between 200 and 255 m. Three mechanisms for the generation of enhanced turbulence are hypothesized: i) local and remotely forced near-inertial waves superimposing to create shear-unstable layers, ii) kinematic superposition of eddy and near-inertial shear that generates patches of turbulence at inertial periods, iii) a near-inertial critical layer due to dynamic wave/mean interaction. Ray tracing simulations will be performed to examine whether vertical vorticity gradients and/or Doppler shifting are responsible for the presence of a critical layer.
Potential link between mountain subsidence and water discharge from a tunnel in north Iceland
Authors: Drouin Vincent , Gautason Bjarni
Published: March 2021

The Vaðlaheiði tunnel is a 7.4 km long tunnel located in north Iceland, linking the Eyjafjörður fjord and the Fnjóskadalur valley. It goes through the Vaðlaheiði mountain at maximum depth of about 500 m. The tunnel was built in order to shorten the main road around Iceland (road 1) by 16 km and avoid a mountain pass which was often blocked by snow during winters. The drilling started in July 2013. On the 16th of February, after having excavated about 1.9 km, a water vein was encountered and started to leak in the tunnel at a rate of about 350 L/s. Drilling was complete in April 2017 and the tunnel opened for traffic in December 2018. As of January 2021, about 250 L/s of a mix of geothermal and cold water is still going out of the tunnel.

The Sentinel-1 SAR satellites from the Copernicus mission provide acquisitions over Iceland since summer 2015. InSAR time-series analysis were conducted for four tracks covering Vaðlaheiði: two ascending (T118, T147) and two descending (T111, T9). Results show that part of the hill subsided about 10 mm between summer 2015 and summer 2016. It also appears that the same area was subsiding about 5 mm per year between summer 2016 and summer 2020. Older datasets from the Envisat SAR mission covering 2004-2010 were analysed and show no evidence of subsidence in the same location. Therefore, it appears there could potentially be a link between the water going out of the tunnel and the subsidence. Especially since water withdrawal at depth is known to cause surface subsidence, like in the case of agriculture irrigation or geothermal exploitation. Using numerical modelling, we attempt to explain this relation between water withdrawal and subsidence in the case of the Vaðlaheiði tunnel.