bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of greenhouse gas fluxes from tropical forests and oil palm plantations on mineral soil
Authors: Drewer Julia , Leduning Melissa M. , Griffiths Robert I. , Goodall Tim , Levy Peter E. , Cowan Nicholas , Comynn-Platt Edward , Hayman Garry , Sentian Justin , Majalap Noreen , Skiba Ute M.
Published: March 2021

Abstract. In Southeast Asia, oil palm (OP) plantations have largely replaced
tropical forests. The impact of this shift in land use on greenhouse gas
(GHG) fluxes remains highly uncertain, mainly due to a relatively small pool
of available data. The aim of this study is to quantify differences of
nitrous oxide (N2O) and methane (CH4) fluxes as well as soil
carbon dioxide (CO2) respiration rates from logged forests, oil palm
plantations of different ages, and an adjacent small riparian area. Nitrous
oxide fluxes are the focus of this study, as these emissions are expected to
increase significantly due to the nitrogen (N) fertilizer application in the
plantations. This study was conducted in the SAFE (Stability of Altered
Forest Ecosystems) landscape in Malaysian Borneo (Sabah) with measurements
every 2 months over a 2-year period. GHG fluxes were measured by static
chambers together with key soil physicochemical parameters and microbial
biodiversity. At all sites, N2O fluxes were spatially and temporally
highly variable. On average the largest fluxes (incl. 95 % CI) were measured
from OP plantations (45.1 (24.0–78.5) µg m−2 h−1 N2O-N), slightly smaller fluxes from the riparian area (29.4 (2.8–84.7) µg m−2 h−1 N2O-N), and the smallest fluxes from logged forests
(16.0 (4.0–36.3) µg m−2 h−1 N2O-N). Methane fluxes
were generally small (mean ± SD): −2.6 ± 17.2 µg CH4-C m−2 h−1 for OP and 1.3 ± 12.6 µg CH4-C m−2 h−1 for riparian, with the range of measured CH4 fluxes
being largest in logged forests (2.2 ± 48.3 µg CH4-C m−2 h−1). Soil respiration rates were larger from riparian areas
(157.7 ± 106 mg m−2 h−1 CO2-C) and logged forests
(137.4 ± 95 mg m−2 h−1 CO2-C) than OP plantations
(93.3 ± 70 mg m−2 h−1 CO2-C) as a result of larger
amounts of decomposing leaf litter. Microbial communities were distinctly
different between the different land-use types and sites. Bacterial
communities were linked to soil pH, and fungal and eukaryotic communities were linked to
land use. Despite measuring a large number of environmental parameters,
mixed models could only explain up to 17 % of the variance of measured
fluxes for N2O, 3 % of CH4, and 25 % of soil respiration.
Scaling up measured N2O fluxes to Sabah using land areas for forest and
OP resulted in emissions increasing from 7.6 Mt (95 % confidence interval,
−3.0–22.3 Mt) yr−1 in 1973 to 11.4 Mt (0.2–28.6 Mt) yr−1 in 2015 due
to the increasing area of forest converted to OP plantations over the last
∼ 40 years.
Multi-fidelity approach to Bayesian parameter estimation in subsurface heat and fluid transport models 
Authors: Menberg Kathrin , Bidarmaghz Asal , Gregory Alastair , Choudhary Ruchi , Girolami Mark
Published: March 2021

The increased use of the urban subsurface for multiple purposes, such as anthropogenic infrastructures and geothermal energy applications, leads to an urgent need for large-scale sophisticated modelling approaches for coupled mass and heat transfer. However, such models are subject to large uncertainties in model parameters, the physical model itself and in available measured data, which is often rare. Thus, the robustness and reliability of the computer model and its outcomes largely depend on successful parameter estimation and model calibration, which are often hampered by the computational burden of large-scale coupled models.

To tackle this problem, we present a novel Bayesian approach for parameter estimation, which allows to account for different sources of uncertainty, is capable of dealing with sparse field data and makes optimal use of the output data from computationally expensive numerical model runs. This is achieved by combining output data from different models that represent the same physical problem, but at different levels of fidelity, e.g. reflected by different spatial resolution, i.e. different model discretization. Our framework combines information from a few parametric model outputs from a physically accurate, but expensive, high-fidelity computer model, with a larger number of evaluations from a less expensive and less accurate low-fidelity model. This enables us to include accurate information about the model output at sparse points in the parameter space, as well as dense samples across the entire parameter space, albeit with a lower physical accuracy.

We first apply the multi-fidelity approach to a simple 1D analytical heat transfer model, and secondly on a semi-3D coupled mass and heat transport numerical model, and estimate the unknown model parameters. By using synthetic data generated with known parameter values, we are able to test the reliability of the new method, as well as the improved performance over a single-fidelity approach, under different framework settings. Overall, the results from the analytical and numerical model show that combining 50 runs of the low resolution model with data from only 10 runs of a higher resolution model significantly improves the posterior distribution results, both in terms of agreement with the true parameter values and the confidence interval around this value. The next steps for further testing of the method are employing real data from field measurements and adding statistical formulations for model calibration and prediction based on the inferred posterior distributions of the estimated parameters.
Reduced El Niño variability in the PlioMIP2 model ensemble
Authors: Oldeman Arthur , Baatsen Michiel , von der Heydt Anna , Dijkstra Henk , Tindall Julia
Published: March 2021

The mid-Piacenzian or mid-Pliocene warm period (mPWP, 3.264 – 3.025 Ma) is the most recent geological period to see atmospheric CO­2 levels similar to the present-day values (~400 ppm). Some proxy reconstructions for the mPWP show reduced zonal SST gradients in the tropical Pacific Ocean, possibly indicating an El Niño-like mean state in the mid-Pliocene. However, past modelling studies do not show the same results. Efforts to understand mPWP climate dynamics have led to the Pliocene Model Intercomparison Project (PlioMIP). Results from the first phase (PlioMIP1) showed clear El Niño variability (albeit significantly reduced) and did not show the greatly reduced time-mean zonal SST gradient suggested by some of the proxies.

In this work, we study ENSO variability in the PlioMIP2 ensemble, which consists of additional global coupled climate models and updated boundary conditions compared to PlioMIP1. We quantify ENSO amplitude, period and spatial structure as well as the tropical Pacific annual mean state in a mid-Pliocene and pre-industrial reference simulation. Results show a reduced El Niño amplitude in the model- ensemble mean, with 11 out of 13 individual models showing such a reduction. Furthermore, the spectral power of this variability considerably decreases in the 3–7-year band and shifts to higher frequencies compared to pre-industrial. The spatial structure of the dominant EOF shows no particular change in the patterns of tropical Pacific variability in the model-ensemble mean, compared to the pre-industrial. Further analyses that will be presented include the correlation of the zonal SST gradient with the El Niño amplitude, investigation of shift in El Niño flavour, and a discussion of the coupled feedbacks at play in the mid-Pliocene tropical Pacific Ocean.
Extreme Precipitation in the Eastern Mediterranean in ERA5
Authors: Rischmüller Alexander , Karwat Alexia , Blender Richard , Franzke Christian
Published: March 2021

Datasets with precipitation indices from the coastal areas of Syria, Lebanon and Israel are defined from the ERA5-Land database (0.1° resolution). In each coastal area the grid point with the highest hourly precipitation is selected. The declustered datasets are modelled by generalised Pareto distribution. The parameters of the stationary models are estimated using the maximum likelihood (MLE) and Bayesian inference methods.

Non-stationary models with several different covariates, i.e., time and teleconnection indices are incorporated into the scale parameter. The parameters of the non-stationary models are estimated using the MLE. The goodness-of-fit of stationary models is assessed by the Anderson-Darling test. QQ-plots subjectively assess the goodness-of-fit for both stationary and non-stationary models. The goodness-of-fit of non-stationary models is assessed in comparison to the stationary models with the likelihood ratio test (LRT) and with the differences in the Akaike information criterion (AIC).

The results show clear non-stationarity with the time covariates. Non-stationarity with teleconnection covariates is incoherent, except for the North Atlantic oscillation (NAO) in Syria. Return levels are estimated for stationary and non-stationary models which are obtained from different quantiles of the time-changing scale parameter vector according to -risk scenarios. The results show that return levels are highest in Syria and lowest in Israel.
Functional role of earthworms to control the hydraulic conductivity of constructed wetlands 
Authors: Gilibert Océane , Costa Dan Tam , Sauvage Sabine , Orange Didier , Capowiez Yvan , Julien Frédéric , Gerino Magali
Published: March 2021

Wetlands are known for their natural service of water quality regulation. The hyporheic zones of the rivers filter and purify the surface water from the stream and infiltrated waters in soil nearby through the riparian zone. This purification service occurs because of a synergy between the substrate and its biodiversity (including plants, bacteria and other invertebrates). Our study deals with constructed wetlands (CW) as a nature-based solution mimicking wetlands water purification process, to purify wastewaters. The REUSE technology of CW is based on the use of specific layers of gravels and sands inside a close concrete structure, planted with specific sub-aquatic plants, where wastewaters or runoff of stormwaters are introduced to be filtered. The technology of Vertical Flow Constructed Wetlands (VFCW) reproduces the water flux observed in the riparian zone with a gravity flow of water. It is composed of reeds planted on a sandy layer (Ø 0-4 mm) and succession of gravel layers. This substrate can be saturated or unsaturated to reproduce the functioning of the hyporheic zone or the riparian zone respectively. By the time, the substrate is colonized by a community of bacteria producing biofilms which capture the residual organic matter from wastewaters to mineralize them. However, the VFCW substrates tend to clog over time due to the accumulation of organic matter and biofilms. Many studies consider earthworms as one of the solutions to alleviate this clogging, thanks to their burrows recreating macropores and preferential channels which help to improve the dispersion of water into the deep soil. The main goal of this study is to assess the impact of earthworm activities on the hydraulic conductivity of columns composed with the same substrate used in the VFCW. Different densities of earthworms (Eisenia fetida) were introduced (0, 100, 500, 1000 g of earthworms/m²) in these columns to be monitored for 37 days. The hydraulic conductivity was measured every 7 days, aside from day 23 with the addition of 40 g of peat bedding on column surfaces to simulate a high organic matter input. Columns with earthworm density superior to 500 g/m² shows an amelioration of their hydraulic conductivity after 21 days. These densities are also able to restore the hydraulic conductivity of the column in less than 7 days after the setting of clogged condition due to the organic matter input (peat bedding) at the sediment surface. This study showed that the burrowing activity of E. fetida improves the hydraulic flux of a sandy substrate and this impact is dependent on the earthworm density introduced. So, the addition of earthworms in the VFCW could serve as a prevention against clogging.
Surface temperature and radiation budget of snow-covered complex terrains
Authors: Robledano Alvaro , Picard Ghislain , Arnaud Laurent , Larue Fanny , Ollivier Inès
Published: March 2021

The temporal evolution of the snowpack is controlled by the surface temperature, which plays a key role in physical processes such as snowmelt. It shows large spatial variations in mountainous areas, where the illumination conditions are variable and depend on the topography. The surface energy budget is affected by the particular processes that occur in these areas, such as the modulation of the illumination by local slope and the re-illumination of the surface from surrounding slopes. These topography effects are often neglected in models, considering the surface as flat and smooth. Here we aim at estimating the surface temperature and the radiation budget of snow-covered complex terrains, in order to evaluate the role of the different processes that control their spatial variations. For this, a modelling chain is implemented to derive surface temperature from in-situ measurements. The main component is the Rough Surface Ray-Tracing (RSRT) model, based on a photon transport algorithm to quantify the impact of surface roughness in snow-covered areas. It is coupled to a surface scheme in order to estimate the radiation budget. To validate the model, we use in-situ measurements and satellite thermal observations (TIRS sensor aboard Landsat-8) in the Col du Lautaret area, in the French Alps. The satellite images are corrected from atmospheric effects with a single-channel algorithm. The results of the simulations show (i) an agreement between the simulated and observed surface temperature for a diurnal cycle in winter; (ii) the spatial variations of surface temperature are on the order of 5 to 10°C between opposed slope orientations; (iii) the agreement with satellite observations is improved when considering topography effects. It is therefore necessary to account for these effects to estimate the spatial variations of the radiation budget and surface temperature over snow-covered complex terrain. 
Crystal zoning patterns: competition between crystal growth and elements diffusion
Authors: Musu Alessandro , Caricchi Luca , Perugini Diego , Corsaro Rosa Anna , Vetere Francesco , Petrelli Maurizio
Published: March 2021

Magma reservoirs represent areas of large variation in the physico-chemical properties of magmas and are directly associated with volcanic activity. Understanding the processes acting at inaccessible depths is of crucial importance to interpret monitoring signals and to develop quantitative models to forecast volcanic activity. Minerals are witnesses of the temporal evolution of the physico-chemical conditions within magma reservoirs recording variations of intensive parameters as chemical signals. However, the competition between crystal growth and elements diffusion in the melt phase can also modulate the chemical zoning of minerals, therefore complicating the interpretation of chemical zoning patterns. To disentangle this complexity, chemically zoned minerals are synthetically grown at the Petro-Volcanology Research Group of the University of Perugia, under controlled conditions. For these experiments tephra from 2002-03 Mt. Etna eruption is used as starting material. The zonation in minerals is been forced inside a high-temperature furnace by oscillating the temperature with three different setups: static conditions, using a controlled deformation gradient (Concentric Cylinder Apparatus) and using a chaotic mixing regime (Chaotic Magma Mixing Device). The zoned crystals are analysed for major and trace elements by Electron Probe Micro Analyzer (EPMA) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS), respectively. High spatial resolution elemental maps (0.5 micrometres) are also collected to characterise the zoning of selected crystals. The data are analysed using a series of custom-built machine learning algorithms to disentangle zoning related to variations of the thermodynamic conditions of crystal growth from the effects of the competition between diffusion and growth. The main target of this project is to provide quantitative tools to distinguish between chemical zoning forced by thermodynamic conditions of growth and chemical zoning produced by competition between crystal growth and element diffusion.
Ozone vertical profiles from TGO/NOMAD-UVIS: an inter-comparison of three retrieval schemes
Authors: Piccialli Arianna , Vandaele Ann Carine , Willame Yannick , Aoki Shohei , Depiesse Cedric , Trompet Loic , Neary Lori , Viscardy Sebastien , Daerden Frank , Erwin Justin , Thomas Ian R. , Ristic Bojan , Mason Jon , Patel Manish , Khayat Alain , Wolff Michael , Bellucci Giancarlo , Lopez Moreno Jose Juan
Published: March 2021

We will present the vertical distribution of ozone obtained from NOMAD-UVIS solar occultations and we will compare the results of three retrieval schemes.

NOMAD (Nadir and Occultation for MArs Discovery) is a spectrometer composed of 3 channels: 1) a solar occultation channel (SO) operating in the infrared (2.3-4.3 μm); 2) a second infrared channel LNO (2.3-3.8 μm) capable of doing nadir, as well as solar occultation and limb; and 3) an ultraviolet/visible channel UVIS (200-650 nm) that can work in the three observation modes [1,2].

The UVIS channel has a spectral resolution <1.5 nm. In the solar occultation mode it is mainly devoted to study the climatology of ozone and aerosols content [3].

Since the beginning of operations, on 21 April 2018, NOMAD UVIS acquired more than 4000 solar occultations with an almost complete coverage of the planet.

NOMAD-UVIS spectra are simulated using three different retrieval scheme:

1) An onion peeling approach based on [4,5] deriving slant columns at the different altitudes sounded, from which local densities are obtained;

2) The line-by-line radiative transfer code ASIMUT-ALVL developed at IASB-BIRA [6] using the Optimal Estimation Method to derive the local density profile in one go (on all transmittances of one occultation observation);

3) A direct onion peeling method deriving sequentially from top to bottom the local densities in the different layers probed.

We will compare results obtained from the different retrieval methods as well as their uncertainties and we will discuss the advantages and difficulties of each method.

References

[1] Vandaele, A.C., et al., Planetary and Space Science, Vol. 119, pp. 233–249, 2015.

[2] Neefs, E., et al., Applied Optics, Vol. 54 (28), pp. 8494-8520, 2015.

[3] M.R. Patel et al., In: Appl. Opt. 56.10 (2017), pp. 2771–2782. DOI: 10.1364/AO.56.002771.

[4] Quémerais, E.,et al. J.Geophys. Res. (Planets)111, 9, 2006.

[5] Piccialli, A. et al., Planetary and Space Science, 113-114(2015) 321–335

[6] Vandaele, A.C., et al., JGR, 2008. 113 doi:10.1029/2008JE003140.
Estimation of secondary organic aerosol formation parameters for the Volatility Basis Set combining thermodenuder, isothermal dilution and yields measurements 
Authors: Uruci Petro , Drosatou Anthoula D. , Sippial Dontavious , Pandis Spyros N.
Published: March 2021

Secondary organic aerosol (SOA) constitutes a major fraction of the total organic aerosol (OA) in the atmosphere. SOA is formed by the partitioning onto pre-existent particles of low vapor pressure products of the oxidation of volatile, intermediate volatility, and semivolatile organic compounds. Oxidation of the precursor molecules results a myriad of organic products making the detailed analysis of smog chamber experiments difficult and the incorporation of the corresponding results into chemical transport models (CTMs) challenging. The volatility basis set (VBS) is a framework that has been designed to help bridge the gap between laboratory measurements and CTMs. It describes the volatility distribution of the OA and the SOA. The parametrization of SOA formation for the VBS has been traditionally based on fitting yield measurements of smog chamber experiments. To reduce the uncertainty of this approach we developed an algorithm to estimate parameters such as volatility product distribution, effective vaporization enthalpy, and accommodation coefficient combining SOA yield measurements with thermograms (from thermodenuders) and areograms (from isothermal dilution chambers) from different experiments and laboratories. The algorithm was first evaluated with “pseudo-data” produced from the simulation of the corresponding processes assuming SOA with known properties. The results showed excellent agreement and low uncertainties when the volatility range and the mass loadings range of the yield measurements coincide. One of the major features of our approach is that it estimates the uncertainty of the resulting parameterization for different atmospheric conditions (temperature, concentration levels, etc.). In the last step of the work, the use of the algorithm with realistic smog laboratory data is demonstrated.
Design and pre-assessment of NBS for coastal erosion and marine flooding: a case study.
Authors: Aguzzi Margherita , Bacci Maurizio , De Nigris Nunzio , Leo Laura Sandra , Morelli Maurizio , Pulvirenti Beatrice , Robello Paola , Ruggieri Paolo , Tavaroli Fabrizio , Unguendoli Silvia , Valentini Andrea , Cacciamani Carlo
Published: March 2021

The natural reserve in Sacca di Bellocchio, Lido di Spina (Italy) is affected by frequent marine floods and intense erosive phenomena which threaten the freshwater ecosystem and biodiversity at the site. Floods and erosion are linked to the reduction of river sediment transport and a progressive ground subsidence and sea level rise. The persistence of these conditions and the future rise in sea level can expose neighboring anthropized areas to coastal risk.

This work presents the project of a nature-based solution (NBS) as a possible defense and mitigation action against coastal erosion and marine flooding along the Bellocchio beach. The NBS has been newly designed   within the European project H2020 OPERANDUM (OPEn-air laboRAtories for Nature baseD solutions to Manage Environmental risk) and consists of an artificial sand dune made of natural materials, such as sand, wood, geotextiles and geomembranes through naturalistic engineering techniques. On the new dune will then be inserted native herbaceous and shrubby vegetation. The dune design was supported by an accurate hydro-morphodynamic modeling of the site combined with data concerning the morphological structure, the erosive dynamics and the local climate.

This study discusses in detail the modeling techniques and the monitoring system that guided the design of the dune and that constitute a basis for the assessment of performance and effectiveness of any future NBS intervention at the site. The monitoring campaign is still ongoing and allows the collection of critical and updated information on the impacts of coastal storms, storm surges and flood events in the area. The dataset clearly highlights that the site morphology is constantly changing due to a multitude of factors, such as seasonality, the increasing incidence and/or intensity of coastal storms, sea level rise, etc. These rapid, and sometimes drastic, morphological changes pose a substantial challenge to NBS's design and, most importantly, to its deployment planning and timing phase.

 
Nano-sized particles and semimetal-rich melts in PGE-rich magmatic mineral systems 
Authors: González-Jiménez José María , Proenza Joaquín A. , Gervilla Fernando , Piña Rubén
Published: March 2021

The results of several high temperature experiments predict that nanoparticles and nanomelts enriched in noble metals indeed exist in magmatic systems. Nanoparticles of Ru-Os-Ir or P-bearing sulfides alloys have been synthetized from S-free or S-undersaturated basaltic silicate melts at > 1000 °C at > 1000 °C. Pt-rich arsenide nanoparticles have also been synthesized in high-temperature sulfide melts well before the melt had reached a Pt–As concentration at which discrete Pt arsenide minerals become stable phases. More recently, the immiscibility of PGE-rich bismuthide melts within Ni-Fe-Cu sulfide liquids have also observed in high-temperature experiments, evidencing the key role played by nanomelts in controlling the PGE partitioning in magmatic mineral systems and their necessary existence for the formation of PGE-rich nanoparticles. However, many researches still remain convinced that these nanoparticles represent artifacts produced during quenching of experimental runs. The combination of focused ion beam micro-sampling techniques with high-resolution transmission electron microscopy (HRTEM) observations allowed the identification of PGE nanoparticles and nanominerals in magmatic base-metal sulfides from the PGE-Cr deposits from the Bushveld Complex in South Africa  and the eastern Cuban ophiolites. Moreover, nanometer sized of all six PGEs (Os, Ir, Rh, Ru, Pt, Pd) are relatively frequent natural quenched silicate melts preserved in mantle xenoliths. Collectively, all these observations made on natural rocks confirm the predictions of previous experiments on the possible formation of PGE mineral nanoparticles in magmatic systems rather to be result of low-temperature subsolidus re-equilibrium of magmatic minerals.

 

 
Controls on the distribution and behaviour of metals in sub-surface metalliferous seamount sediments from the Molloy Ridge system, Arctic Ocean
Authors: Grant Hannah , Lockwood-Ireland Christine , Howe John , Stewart Heather
Published: March 2021

Sub-surface sampling of marine sediments allows investigation of paleo-depositional conditions and subsequent modification by post-depositional geochemical processes. This sedimentary record can encompass many thousands of years and record discrete events where proximal and distal material is incorporated into the pelagic sediment column. The Arctic Ocean is the world’s smallest ocean, however evidence from sedimentary records show it has a pivotal role in the regulation of many oceanographic and physiographic processes. Despite this, there are only limited studies on the distribution and geochemical behaviour of metals within sub-surface marine sediments of the Arctic Ocean basin. This study presents a detailed geochemical investigation for two sediment piston cores to a maximum of 5.7 metres depth and spanning at least 44,000 years BP, from two seamounts bordering the western flanks of the Molloy Hole in the Fram Strait.

Comparison to other studies of sub-surface ridge sediments below 60oS on the Mid-Atlantic Ridge reveals these piston cores contain elevated metal concentrations, particularly for Mn, Co, and Ni. Distinct variability is observed within, and between the cores; particularly the interplay between Fe and Mn, the two most common authigenic elements in marine pelagic sediments. Within the Molloy Ridge neovolcanic zone, in the upper half of the easternmost core (PC127/79), Fe and Mn are decoupled and metal distribution is controlled by redox front migration. Decoupling occurs as Mn is more readily dissolved compared to Fe, and Fe in solution is more reactive and precipitates quicker during remobilisation. In PC127/79, Mn is strongly associated with other redox-sensitive metals (e.g., Co, Ni, Mo, U) likely in Mn-oxide dominated horizons, and Fe is strongly associated with V and As. Towards the base of the core, Fe and Mn are coupled, but are not associated with a distinct discrete metalliferous signature of Co, Ni, Cd and Ti. These metals are also negatively associated with major rock-forming elements such as Si, Al, Mg, and Ca. In the western core (PC127/80), Fe and Mn are coupled, are positively associated with the majority of metals and the major rock forming elements, and negatively correlated with common clay-derived components.

Investigation of pelagic versus hydrothermal component indices indicate that the distinct metalliferous signature towards the base of PC127/79 may have a hydrothermal origin. Hydrothermal activity associated with ultramafic oceanic core complexes is known on superslow-spreading ridges to the north and south of the Molloy Ridge, however contributions of metals from ice-rafted debris or past mass wasting events off the Spitsbergen margin cannot be ruled out.
Persistent organic pollutants distribution of small coastal catchments at the Canadian Beaufort coast.
Authors: Lodi Rachele , Wagner Julia , Hugelius Gustaf , Martin Victoria Sophie , Speetjens Niek , Richter Andreas , Gabrieli Jacopo , Barbate Carlo
Published: March 2021

Recent decades have shown phases of very rapid warming in the Canadian Arctic. This raises a concern, also in reference to potential changes in permafrost active layer deepening, enhancing the fact that seawater, snow and soils are becoming important secondary sources remobilizing persistent organic pollutants (POPs). This work investigates the potential influence of permafrost on POPs distribution in the soils of two small coastal catchments at the Canadian Beaufort coast. One catchment is located south of Herschel Island on the mainland and was covered by the Laurentide ice sheet during the last glacial maximum (LGM), the second catchment is located westerly at Komakuk Beach and was ice-free during the LGM.

Soils were sampled by horizon in the Active Layer from an open soil pit and by coring into the permafrost, near the top of the permafrost table and at 90 cm depth from the soil surface (99 samples form Ptarmigan Bay and 89 from Komakuk Beach). The total sampling depth was 1,0 m (including Active Layer and Permafrost). A random distribution of the points over the areas guaranteed the sampling over different Landforms, aiming to understand the contaminant concentration and distribution. Quantification of PAHs, PCBs, HCB was performed using GC-MS technique, a 7890A gas chromatographer coupled with a 5975C MSD System, Agilent Technologies, at CNR-ISP Venice, Italy.

Preliminary results confirm that the mechanism responsible for the transport of POPs into the soil are believed to be gravity drainage and capillary suction into fissures and cracks. An accumulation of PAHs has been detected in the permafrost transient layer. It is probably related, as demonstrate in literature, to the accumulation and transport of soil organic carbon influence, as well as the changing in hydraulic barriers. The role of cryoturbation in the vertical transport and accumulation of POPs is also considered and discussed.

The study has been conducted thanks to Grant Agreement number: 773421 — Nunataryuk — H2020-BG-2016-2017/H2020-BG-2017-1 ‘Permafrost thaw and the changing arctic coast: science for socio-economic adaptation — Nunataryuk’
Inverse energy cascade in ocean macroscopic turbulence:      Energy transfer rate ε and Richardson-Obhukov  constant g from an surface drifter experiment in the Benguela upwelling system
Authors: Draeger-Dietel Julia , Griesel Alexa
Published: March 2021

We derive the energy transfer rate ε from the 3rd order relative (longitudinal)  velocity structure function <Δul3>=(3/2)εs from ocean surface drifter trajectories in the turbulent mixed layer of the Benguela upwelling region off the coast of Namibia.  Combination with the  mean squared pair separation<s2(t)> =gεt3 reveals the Richardson-Obhukov constant g≅0.5, which is remarkably close to the one measured in  controlled two-dimensional turbulent flows in laboratory. We verify the  two coupled  cascades of energy (upscale/inverse) and enstrophy (downwscale) by  the  theoretically predicted  slope 1  for <Δul3> for inertial scales (above the injection scale) and slope 2 for  the 2nd order structure function <Δul2> for non-local scales (below the injection scale) respectively. We detect  additional 'ballistic contributions' in the central regime of the corresponding probability distribution P(st) of relative separations s for fixed time t, leading to an additional  power law factor s-α with  α ≅ 5/3. The algebraic decay with 1<α <2 revives  to the relevance of Levy distributions in the stochastic description of the turbulent transport process in contrast to former claims. Our findings  of a positively skewed   probability distribution P(Δuls) of relative longitudinal velocity Δul  for inertial scales s renews the question of intermittency in the  inverse energy cascade.
Multi-model projections of evaporation in a sub-tropical lake
Authors: La Fuente Sofia , Woolway Iestyn , Jennings Eleanor , Gal Gideon , Kirillin Georgiy , Shatwell Tom , Ladwig Robert , Moore Tadhg , Couture Raoul-Marie , Côté Marianne , Råman Vinnå Love
Published: March 2021

Evaporation of surface water is critical to the basic functioning of lakes. It directly and, in some cases, substantially modifies the hydrologic, chemical, and energy budgets, making evaporation one of the most important physical controls on lake ecosystems. Predicting lake evaporation response to climate change is, therefore, of paramount importance. Most studies that simulate climate change impacts on lake evaporation have utilised only a single mechanistic model. Whilst such studies have merit, the advantage of applying multiple, independently developed models (i.e., an ensemble approach), is that some of the inherent uncertainties in the individual lake models due to, for example, different model structures, can be reduced thus enabling increased robustness of historic and future projections. In this study, we present results from the Inter-Sectoral Impact Model Intercomparison Project phase 2b (ISIMIP) Lake Sector, where lake evaporation responses to 20th and 21st century (1901-2099) climate change has been simulated with a suite of independently developed lake models under different climate change scenarios (Representative Concentration Pathways, RCP, 2.6, 6.0 and 8.5). Our study focuses on Lake Kinneret (Israel), a sub-tropical monomictic lake of socioeconomic importance. Our simulations are validated during the historic period with bulk evaporation estimates calculated from high frequency meteorological and in-lake observations. Our results demonstrate that the lake models provide an accurate representation of historical variability in lake evaporation, with promising comparisons of the magnitude, timing and seasonality of evaporative water loss. Future evaporation projections at Lake Kinneret show that evaporation anomalies will increase by the end of the century. We show that multi-model projections of lake evaporation can accurately represent the historic period and hence provide reliable future projections that will be vital for water management.
On the lack of widespread bottom simulating reflectors in the Mediterranean Basin
Authors: Corradin Cristina , Camerlenghi Angelo , Giustiniani Michela , Tinivella Umberta , Bertoni Claudia
Published: March 2021

In the Mediterranean Basin, gas hydrate bottom simulating reflectors (BSR) are absent, with very few and spatially limited exceptions occurring in Eastern Mediterranean mud volcanoes and in the Nile deep sea fan. This is in spite of widespread occurrence of hydrocarbon gases in the subsurface, mainly biogenic methane, from a wide range of stratigraphic intervals.
In this study we model the methane hydrate stability field using all available information on DSDP and ODP boreholes in the Western Mediterranean and in the Levant Basin, including the downhole changes of pore water salinity. The models take into account the consequent pore water density changes and use known estimates of geothermal gradient. None of the drilled sites were located on seismic profiles in which a BSR is present.
The modelled base of the stability field of methane hydrates is located variably within, below, or even above the drilled sedimentary section (the latter case implies that it is located in the water column). We discuss the results in terms of geodynamic environments, areal distribution of Messinian evaporites, upward ion diffusion from Messinian evaporites, organic carbon content, and the peculiar thermal structure of the Mediterranean water column.
We conclude that the cumulative effects of geological and geochemical environments make the Mediterranean Basin a region that is unfavorable to the existence of BSRs in the seismic record, and most likely to the existence of natural gas hydrates below the seabed.
Reconstruction of the Jurassic to Early Cretaceous tectono-magmatic evolution of the Northern Andean Arc from their Crustal Thickness and Thermobarometry
Authors: Chavarria Luisa , Bustamante Camilo , Cardona Agustín , Bayona Germán
Published: March 2021

Igneous rocks in magmatic arcs record variations in composition, thermal flux, and subduction dynamics through time. In the Northern Andes, arc magmatism of the Jurassic age registers a complicated history, including the fragmentation of Pangea at the end of the Triassic and the beginning of a new subduction zone in the Jurassic located at the western margin of South America.

We characterized the crustal thickness variations of the Early Jurassic to Early Cretaceous (194-130 Ma) in plutonic and volcanic rocks of the Northern Andes of Colombia and Ecuador, using trace elements signatures and analyzed the implications of the emplacement conditions during the last stage of the magmatism using Al-in-hornblende thermobarometry and mineral chemistry. Moderate rare earth elements (REE) slopes and depleted heavy REE patterns show that the primary residual magma source was amphibole, but plagioclase and pyroxene were also significant residual phases indicating that the magma source was formed in a crust that varied in thickness from 35-50 km. The La/Yb and Sr/Y crustal quantifications variations indicate that the arc underwent two thickening episodes. The first episode (190 to 180 Ma) is associated with a magmatic event. The second episode (165 to 154 Ma) is related to the shift to an oblique subduction setting and a subsequent collisional event that produced medium P-T metamorphic rocks. In the Late Jurassic to Early Cretaceous (154-130 Ma), the crust became thinner and, in this scenario, was emplaced the last stage of plutonism with depths that varied from shallow to deep level (until 25.5 km) in the crust.
Modelling Mineral Snowflakes in the Atmospheres of Gas-Giant Exoplanets
Authors: Samra Dominic , Helling Christiane , Min Michiel , Birnstiel Til
Published: March 2021

Exoplanets provide excellent laboratories to explore novel atmospheric regimes; using observations coupled with microphysical models we can probe our understanding of the formation and evolution of planets beyond those in the Solar System. However, clouds remain a key challenge in observation of exoplanet atmospheres, both altering the local atmospheric composition and obscuring deeper atmospheric layers. Currently, most observed exoplanet atmospheres are tidally locked gas-giants in close orbit around their host star. These hot and ultra-hot Jupiters have day-side temperatures in excess of 2500 K, and still above 400 K on the night-side, thus they form solid clouds made of minerals, metal oxides and metals. These clouds may form snowflake like structures, either through condensation or by constructive collisions (coagulation).

We explore the effects of non-compact, non-spherical cloud particles in gas-giant exoplanet atmospheres by expanding our kinetic non-equilibrium cloud formation model, to include parameterised porous cloud particles as well as cloud particle growth and fragmentation through collisions. We apply this model to prescribed 1D temperature - pressure Drift-Phoenix atmospheric profiles, using Mie theory and effective medium theory to study cloud optical depths, representing the effects of the non-spherical cloud particles through a statistical distribution of hollow spheres.

Finally, we apply our cloud formation model to a sample of gas-giants as well as ultra-hot Jupiters, using 1D profiles extracted from the 3D SPARC/MITgcm general circulation model. In particular, we take the example cases of gas-giant WASP-43b and the ultra-hot Jupiter HAT-P-7b, where we find dramatic differences in the day-/night-side distribution of clouds between these types of exoplanets due to the intensity of stellar irradiation for HAT-P-7b. Further an asymmetry in cloud coverage at the terminators of ultra-hot Jupiters is observable in the optical depth of the clouds, which affects the observable atmospheric column and thus has implication for detection of key gas phase species. Clouds also enhance the gas phase C/O which is often used as an indicator of formation history. With next-generation instruments such as the James Webb Space Telescope (JWST) such details will begin to be examined, but we find that a detailed understanding of cloud formation processes will be required to interpret observations.
Forcing climate variability has large impacts on terrestrial carbon storage in a dynamic global vegetation model
Authors: Krause Andreas , Küpfer Katharina , Rammig Anja
Published: March 2021

Terrestrial carbon storage is largely driven by prevailing climate conditions. However, ecosystems are not only affected by mean climate conditions but also by day-to-day climate variability, which is projected to increase in the future. Here we explore the effects of low vs. high climate variability on global terrestrial carbon storage in the dynamic global vegetation model LPJ-GUESS. Low variability corresponds to linear interpolation between monthly means while high variability corresponds to daily means. We conduct three factorial simulations: one driven by low variability for temperature, radiation, and precipitation; one with low temperature and radiation variability but high precipitation variability; and one with high variability for all climatic drivers. All three options are commonly used in existing LPJ-GUESS studies but have so far not been compared to each other in terms of carbon cycle impacts. Surprisingly, the low variability simulation results in the smallest terrestrial carbon stocks globally (1963 Gt C), while low temperature/radiation variability but high precipitation variability simulates the largest carbon storage (2171 Gt C). Differences are most pronounced in high latitudes and deviations from the global trend also occur in some regions. Exploring the underlying processes, we find that differences in carbon stocks are largely driven by differences in ecosystem productivity. In LPJ-GUESS, high precipitation variability increases nitrogen availability via enhanced nitrogen mineralisation and reduced leaching, thereby promoting plant growth. In contrast, high temperature variability decreases productivity as the optimum temperature range for photosynthesis is often exceeded in temperate and boreal regions. Differences in fire mortality and soil water availability across simulations seem to be less important. Our results suggest that future changes in climate variability could impact ecosystem carbon storage via subtle effects on photosynthesis and coupled carbon-nutrient cycling. They also imply that ecosystem modellers need to be aware that changing the temporal resolution of the input climate (e.g. from monthly to daily means) may substantially affect their simulation results.
The Interplay between Volcanic and Solar Cooling in the Early 19th Century
Authors: Fang Shih-Wei , Timmreck Claudia , Jungclaus Johann , Schmidt Hauke
Published: March 2021

Volcanic eruptions and reduced solar radiance can individually cool our globe through both direct changes in incoming radiation and indirect influences from dynamical processes. However, whether the cooling from the combination of two forcing can be linearly additive, or if additional cooling exists when reduced solar radiance is imposed during volcanic eruptions remains unclear. In this project, by using the state-of-art climate model (MPI-ESM1-2-LR), we found that the total cooling of the two forcing can be additive, but also have additional cooling during the period when volcanic cooling bouncing back to climatology. Our experiments focus on the early 19th century (1791-1850) since the period existed multiple strong volcanic events (especially the 1809 unidentified eruption and 1815 Tambora eruption), a solar minimum (Dalton minimum from 1790-1830), and limited influence from anthropogenic greenhouse gases. In the presentation, we will discuss how volcanic eruptions and different amplitudes of solar reconstructions can individually and together cool the surface through both direct radiative changes and dynamical influences. Our main focus will be how the atmospheric circulation may influence the polar sea ice and large-scale climate patterns when imposing combinations of solar and volcanic forcing.
Application of a combined and automated monitoring and early warning system for debris flows at the Dawinbach
Authors: Schöffl Tobias , Koschuch Richard , Jocham Philipp , Hübl Johannes
Published: March 2021

After a heavy rainfall event on August 31st, 2019, a debris flow at the Dawinbach in the municipality of Strengen (Tyrol, Austria) caused a blockage of the culvert below the provincial road B-316 and deposition in the residential area. The debris deposition raised up to 2 to 3 meters on the road and led to property damage to real estate. The total volume of the debris flow was approximately 15 000 cubic meters.

In order to control a further debris flow of this magnitude, the Austrian Service of Torrent and Avalanche Control started to construct mitigation measures. They include a channel relocation in order to significantly increase the channel crosssection. Hence the construction company STRABAG is also relocating the provincial road bridge.

Since the risk for this road section and for the workers on site is particularly high during the construction period, a combined monitoring and early warning concept was developed and implemented by the BOKU, Vienna and the company IBTP Koschuch.

The monitoring site consisting of a pulse compression radar and a pull rope system was installed 800m upstream from the fan. The combination of the two sensors now results in three major advantages.

At sensor level, the system operates redundantly.

A more reliable differentiation between increased discharge or debris flow is given.

In the event of a false alarm, the system provides easier diagnosis and assignment of the fault.

Two events of increased runoff occurred during the deployment period. Both were successfully detected by the pulse compression radar. Here, the first event was used for threshold validation of the radar unit. Thus, an alarm could already be sent out automatically for the second one. The road is controlled by an integrated light signal system consisting of three traffic lights. A siren near the construction site can warn workers of an impending event by means of an acoustic signal. The reaction time after the alarm has been triggered is between 75 and 150 seconds, depending on the speed of the debris flow. The responsible authorities are informed by sending an SMS chain, which includes details about the type of process and the type of the activated triggering system.