bluuebunny/crossref_metadata_2025 huggingface dataset:
A recent update on the circulation and water masses around the Filchner and Ronne ice shelves in the southern Weddell Sea
Authors: Janout Markus , Hellmer Hartmut , Hattermann Tore , Osterhus Svein , Stulic Lucrecia , Huhn Oliver , Sültenfuss Jürgen , Kanzow Torsten
Published: March 2020

The Filchner and Ronne ice sheets (FRIS) compose the second largest contiguous ice sheet on the Antarctic continent. Unlike at several other Antarctic glaciers, basal melt rates at FRIS are comparatively low, as cold and dense waters presently dominate the wide southern Weddell Sea (WS) continental shelf and effectively block out any significant inflow of warmer ocean waters. We revisited the southern WS shelf in austral summer 2018 during Polarstern expedition PS111 with detailed hydrographic and tracer measurements along both the Ronne and Filchner ice fronts. The hydrography along FRIS was characterized by near-freezing high salinity shelf water (HSSW) in front of Ronne, and a striking dominance of ice shelf water (ISW) in Filchner Trough. The cold (-2.2°C) and fresher (34.6) ISW was formed by the interaction of Ronne-sourced HSSW with the ice shelf base. The strong dominance of ISW in Filchner Trough indicates a recently enhanced circulation below FRIS, likely fueled by enhanced sea ice production in the southwestern WS. We view these recent observations in a multidecadal (1973-present) context, contrast the two dominant circulation modes below FRIS, and discuss the importance of sea ice formation and large-scale sea level pressure patterns for the stability of the ocean circulation and basal melt rates underneath FRIS.
Evaluation of soil quality in different land uses in the Mengzi Gabin Basin, Southwest of China
Authors: Tang Liqun , Shan Zhijie , Yu Yang
Published: March 2020

Re-vegetation has been widely carried out to prevent land degradation, reduce soil erosion, and improve soil quality. In order to investigate the characteristics of soil nutrients content in different land use types of karst gabin basin, soil organic matter, soil total nitrogen, soil total phosphorus, soil total potassium, soil pH, and soil texture in woodland, agricultural land, orchard, and grassland were surveyed in Mengzi Gabin Basin, Southwest of China. The difference of soil indicators between vegetation types was analyzed, and soil fertility quality of four land use types was comprehensively evaluated by the soil quality index (SQI). The results showed that land use significantly affected soil organic matter content. Soil organic matter content was the highest in grassland, followed by agricultural land and forest land, while orchard was lowest. There was a significant difference in soil total nitrogen content between different land uses. The total nitrogen content in farmland soil was the highest, followed by grassland and woodland, and the lowest in the orchard. Woodand had the highest total potassium content and the lowest total phosphorus content. The grassland soil had the highest total phosphorus content and the lowest total potassium content. pH value in the four land use types was acidic, ranged from 5.82 to 6.67. The soil quality index showed that woodland had the highest soil fertility quality. The results of the study could provide the basis of soil nutrients variation and status in Gabin basin, and also provides support for evaluating the soil improvements during vegetation restoration in fragile Karst ecosystems.
Status of GFZ's GRACE/GRACE-FO RL06 Level-2 and Level-3 Data Products
Authors: Dahle Christoph , Murböck Michael , Flechtner Frank , König Rolf , Dobslaw Henryk , Boergens Eva , Sasgen Ingo , Groh Andreas
Published: March 2020

The GRACE Follow-On (GRACE-FO) mission was successfully launched on May 22nd, 2018 and continues the 15-year data record of monthly global mass changes from the GRACE mission (2002-2017). The German Research Centre for Geosciences (GFZ) as part of the GRACE/GRACE-FO Science Data System (SDS) has recently reprocessed the complete GRACE mission data (RL06 in the SDS nomenclature). These RL06 processing standards serve as common baseline for the continuation with GRACE-FO data.

This presentation provides an overview of the current processing status and the validation of the GFZ GRACE/GRACE-FO RL06 gravity field products. Besides its Level-2 products (monthly sets of spherical harmonic coefficients representing the Earth's gravity potential), GFZ additionally generates user-friendly Level-3 products in collaboration with the Alfred-Wegener-Institut (AWI) and TU Dresden. These Level-3 data products comprise dedicated mass anomaly products of terrestrial water storage over non-glaciated regions, bottom pressure variations in the oceans and ice mass changes in Antarctica and Greenland, available via GFZ's Gravity Information Service (GravIS) portal (http://gravis.gfz-potsdam.de/).
Hydrological analysis of runoff formation in a small forested mountain catchment using δ2H and δ18O ratios
Authors: Rommel Lisa , Wöhling Thomas
Published: March 2020

The identification of origin, flow paths and transit times of water in catchments is an important component for process-based model development for runoff prediction. Hydrological studies offer, combined with isotope data, the possibility to quantify interactions between different compartments in catchments. In the context of this work it is examined to what extent event sampling of precipitation, streamflow, soil water and groundwater and the evaluation of their isotopic ratios δ2H and δ18O enable complex hydrological process investigations in the small forested mountain catchment of the river Große Ohe in the Bavarian Forest National Park. Within this study process analyses are carried out on small scales, e.g. runoff formation on hill slopes and on catchment scale as integrative process analysis. The water samples were collected during a small flood event and analysed for the isotope ratios δ2H and δ18O using a Picarro. A hydrograph separation was carried out through a comprehensive evaluation of the concentration profiles during the event. In combination with further hydrological and soil hydrological observations possible areas of origin and retention times of the water were determined. A strongly delayed reaction of the groundwater was observed which suggests that groundwater is not contributing to stream flow during a flood event, but a possible mobilization of pre-event water in the riparian zone can be observed as a response to precipitation events. The knowledge gained hereby is the basis for further process analysis and model development.
A dimensionality reduction-feature selection approach to streamﬂow reconstruction using dendrochronological data
Authors: Obertelli Marco , Amaranto Alessandro , Castelletti Andrea
Published: March 2020

A dimensionality reduction-feature selection approach to streamﬂow reconstruction using dendrochronological data

Marco Obertelli1, Alessandro Amaranto1, Andrea Castelletti1

1Department of Electronics, Information and Bioengineering, Politecnico di Milano, Milano, Italy

Instrumental gauge records are the basis for understanding streamflow variability and for informing water management plans accordingly. Yet, these records seldom exceed 100 years and might thus be insufficient for capturing the whole range of streamflow variability for a given river section. Tree ring width from climatically sensitive trees provides a means for developing long-duration chronologies that extend beyond instrumental recording. Considering their dependence on temperature and surface water availability in a specific year, dendrodata have been recognized in the literature as representative climate proxies; and have been therefore widely used in recent years for reconstructing chronologies of hydrological variables as precipitation frequency, drought severity and streamflow variability. Paleoclimate reconstructions are usually carried by combining a dimensionality reduction-feature selection technique with linear regression methods.  The goal of this study is to better understand long-term hydrological variability in the Rhine and the Po river basins by reconstructing for the first time their streamflow trajectories from paleoclimatic data. We apply Principal Component Analysis (PCA) for dimensionality reduction and Multiple Linear Regression (MLR) as a reconstruction model.  Palmer Drought Severity Index (PDSI) trajectories, inferred from tree-rings chronologies are employed as paleoclimate proxy. Numerical results show a good accuracy in the reconstruction approach, especially in the Rhine basin (average R2 = 0.60). The accuracy decreases in the Po basin, probably due to the Alpine hydrologic regimes which includes complex nonlinear phenomena (e.g. solid precipitation and snowmelt) not fully described by the PDSI drought index. Historical evidence of the reconstructed 1817 drought in the Po river basin has been found as a proof of the reliability of this approach. The variety of the morphological and hydrological characteristics reflected in the two river basins considered in this study, allows to explore how some of their peculiarities reflect on the streamflow reconstruction, increasing the possibility to replicate the approach in other areas of the world.
Longwave Radiation at the Cloud-Aerosol Transition Zone from Radiative Parameterizations in Weather Research and Forecasting Model (WRF)
Authors: Jahani Babak , Calbó Josep , González Josep-Abel
Published: March 2020

There are conditions between cloudy and cloud-free air at which it is hard to define the suspended particles in the atmosphere either as a cloud or an atmospheric aerosol; it is called twilight or transition zone. This occurs when characteristics of the suspended particles are between those corresponding to a pure cloud and those corresponding to a pure atmospheric aerosol. However, in most meteorological and climate studies the condition of sky is assumed to be either cloudy (fully developed cloud) or cloud-free (dry aerosol), neglecting the transition zone. The present communication aims to show the uncertainties introduced by this simplified assumption in modeling longwave radiation. For this purpose, the parameterizations RRTMG, NewGoddard and FLG included in the Weather Research and Forecasting Model (WRF) version 4.0 were isolated from the whole model. These parameterizations were then used to perform a number of simulations under ideal “cloud” and “aerosol” modes, for different values of (i) cloud optical thicknesses resulting from different sizes of ice crystals or liquid droplets, cloud height, mixing ratios; and (ii) different aerosol optical thicknesses combined with various aerosol types. The differences in the resulting longwave radiative effects (RE) at the top of the atmosphere and at the Earth surface were analyzed. The primary results show: (1) the parameterization RRTMG is not capable of simulating the REs of the aerosols in the longwave region, (2) different assumptions of a situation corresponding to the transition zone lead to a mean relative uncertainty of about 170% in the estimated longwave irradiance at both top of the atmosphere and surface, (3) the absolute uncertainties observed in the surface downwelling irradiances are substantially greater than those relating to the upwelling irradiances at top of the atmosphere.
Modulation of regional precipitation and groundwater level variability by large-scale oceanic/atmospheric circulation over interannual and interdecadal scales
Authors: Massei Nicolas , Fournier Matthieu , Chun Kwok Pan , He Qing , Dieppois Bastien , Lattelais Clément , Dupont Jean-Paul
Published: March 2020

Hydrological processes vary over long time-scales, which are originating from large-scale climate. It is not always straightforward, however, to identify how large-scale climate variability can affect regional or local-scale hydrological processes, as such relationships are not linear. Taking the example of the Seine river watershed (northern France), we study the modalities of precipitation and chalk aquifer groundwater level (GWL) variability, focusing on interannual (4-12 years) and interdecadal (12-23 years) scales. We propose a methodological approach for analysing and discussing potential large-scale relationships and forcings on hydrological systems.

163 GWL and 13 precipitation monthly time series, covering the northern half of metropolitan France between 1964 and 2015, were analysed using continuous and discrete multiresolution wavelet transforms. GWL time series all revealed statistically significant oscillating components on interannual and interdecadal scales, but with different amplitudes in space. All precipitation time series displayed the same oscillating components across the watershed with rather constant amplitudes spatially, contrary to GWL time series, which suggest an impact of local physical watershed properties to filter some parts of the climate signal. Using precipitation and GWL time series available over one century, as well as the NOAA 20CR reanalysis, we then analysed the relationship with the North Atlantic atmospheric circulation at both the interannual and interdecadal scales. On interannual scale, using sea-level pressure and geopotential height at 200 hPa, we found that precipitation and GWL variability would be linked to pronounced Rossby wave-like patterns. On interdecadal scale, the patterns obtained correspond to clear west-circulation patterns, which are very similar to the patterns associated with Atlantic Multidecadal Oscillation (AMO). Interdecadal precipitation variability are indeed also found to be consistent with the positive and negative phases of the AMO, suggesting potential impacts on hydrological variability. Examining both precipitation and GWL, major droughts occured during low levels of interannual and interdecadal components. This study therefore demonstrates that such extreme events would then be: i) linked to a weakened western circulation with strong North-South jet stream oscillations on interannual scale; ii) modulated by western circulation associated with the AMO on interdecadal scale.
Late stage of the Gibraltar arc subduction system (western Mediterranean): from slab-tearing to continental-edge delamination
Authors: Negredo Ana M. , Mancilla Flor de Lis , Clemente Carlos , Morales Jose , Fullea Javier
Published: March 2020

The Gibraltar arc subduction system is the result of the fast westward roll-back of the Alboran slab at the westernmost end of the Mediterranean Sea. This westward motion is controlled, at its northern edge, by slab tearing along a so called STEP (Subduction-Transform-Edge-Propagator) fault under the Betics orogen. The Alboran subduction process is in its last evolutionary stage, where the oceanic lithosphere has been fully consumed and the continental lithosphere attached to it collides with the overriding plate. In this situation the continued slow convergence between Iberia and Africa could lead to a short stage of continental subduction. However, the particular setup after slab tearing, characterized by a sharp lateral contrast between the orogenic Betic lithosphere and the adjacent thinned lithosphere of the overriding Alboran domain, is also prone to trigger continental delamination, i.e. the detachment between the crust and the lithospheric mantle. Several lines of evidence indicate that northwards mantle delamination is likely occurring in the central Betics. The fast average topographic uplift during the last 8 Ma together with the lack of spatial correspondence between the highest topography (Sierra Nevada Mountains) and the thickest crust indicate that the topography could be partly supported by asthenospheric upwelling due to continental delamination. In this study we take advantage of an unprecedented resolution seismic receiver functions lithospheric mapping in the Betic orogen to investigate the conditions for, and consequences of, edge delamination in the Iberian margin after slab tearing. We show that given a weak enough Iberian lower crust the delaminated lithospheric mantle peels off the crust and adopts a geometry consistent with the imaged southward dipping Iberian lithosphere in the central Betics. In contrast, the thinned lower crust beneath the Iberian margin in the eastern Betics prevented mantle delamination via asthenospheric inflow into the lower crust.
Strain gauge measurements in hydraulic experiments: Chinese firecrackers versus industrial solutions
Authors: Wolff Martin , Schnauder Ingo
Published: March 2020

Force measurements using load cells equipped with strain gauges are widely applied in hydraulic experimentation and field surveys. In our case, drag on 5 horizontal cylinders in cross-flows had to be measured directly in a hydraulic water flume. We tested different setups and came up with a two-load cell solution per cylinder as mechanically best way to fix the cylinders in the flume.
The costs for an amplifier system of industrial standard is in the order of magnitude of 10.000 Euro and for load cells around 500 Euro. For our multiple cylinder application, the costs of an industrial standard solution exceeded the budget and forced us to find alternatives. Chinese-made load cells cost only a few Euros each. We designed our own measuring system, consisting of an external analogue-digital converter and a microcontroller. A Python script was programmed to operate the microcontroller and analyse the data.
In the session, we will give an overview of the flume setup and the measuring system – including live operation. We will discuss the required calibration procedure for the load cells and data quality and give recommendations for further improvements.
Mars' Annular Polar Vortex
Authors: Ball Emily , Mitchell Dann , Seviour William , Vallis Geoffrey , Thomson Stephen
Published: March 2020

The Martian winter polar vortex has recently been shown to be annular in nature, with a local minimum in potential vorticity near the pole. This suggests barotropic instability, yet the vortex is remarkably persistent. It has been shown that its annular nature may be due to the release of latent heat from CO2 condensation, CO2 clouds, changes in dust distributions, and the strength of the Hadley circulation circulation, with many of these being interlinked. In this poster, we present results using the the Mars Analysis Correction Data Assimilation (MACDA) reanalysis dataset, which demonstrates clearly the annular vortex. Additionally, we perform simulations of the Martian atmosphere and its response to varying topography and radiation scheme in the flexible Isca framework, a climate model capable of simulating the Martian basic state at varying levels of complexity. It is noted that the strength of the Martian polar vortex is significantly lower in Isca simulations than in the MACDA dataset. Through further simulations with Isca, we aim to investigate the effect of CO2 condensation on the strength and shape of the Martian polar vortex.
Past hydrological trends on the Pyrenees: towards a higher spatial heterogeneity
Authors: Zabaleta Ane , Haro-Monteagudo David , Antiguedad Iñaki , Beguería Santiago
Published: March 2020

The Pyrenees are a fundamental source of water resources for the territories surrounding this mountain range and beyond, and like other mountainous areas they are very vulnerable under global change. The CLIMPY project (Interreg-POCTEFA) calculated an increase of 1.5 ℃ on average temperature for this region in the last 60 years.

One of the aims of the PIRAGUA project (Interreg-POCTEFA) is to make a regional and temporal characterisation of the water resources of the Pyrenees. To achieve that objective, a common standardized and homogenized database was created for the first time in this transboundary region with streamflow data measured by the different water agencies operating in the area (1956-2015).

To avoid human impacted gauging stations (e.g. upstream reservoirs and large irrigation withdrawals), and to analyse only those with a reasonable quality, only a number of the initially obtained streamflow series were considered. A set of indicators was calculated from the selected daily streamflow series concerning mean, high and low flows at annual and monthly scales for different time periods ending in 2015. 

Results show that median discharge decreased an average of 30% in all gauging stations between 1956 through to 2015. High and low streamflow also decreased during the same period. On average, the number of days below the first quartile increased 10 days per decade, and the number of days above the third quartile decreased 6 days per decade. The interquartile range decreased 4% per decade on average showing that streamflow suffered a generalised reduction between 1956 and 2015. Regarding monthly streamflow, trends for median streamflow and the first quartile are similar to the annual scale. The most significant decrease is observed during spring (12-15% on average), and the lowest decrease occurs in the autumn (6-9% on average). Since 1986, trends change and streamflow increases are observed at some gauging stations with results that are spatially very heterogeneous. This inflection may be an effect of a more spatially heterogeneous climate in the recent past or of land use changes that are not regionally homogeneous, or a combination of both.
60 years of rock glacier displacements and fluxes changes over Laurichard Rock glacier, French Alps.
Authors: Cusicanqui Diego , Rabatel Antoine , Bodin Xavier
Published: March 2020

Recent acceleration of rock glaciers has been largely documented in the European Alps, hence highlighting an increase in flow speed of stable rock glaciers and some anomalous behaviors called destabilization (development of landslides-like features on the rock glacier surface).  In this study, we focus on Laurichard active rock glacier, 225 m long, up to 75 m wide, which covers an area of 0.084 km2 and has the longest measurement time-series in the French Alps. Here we aim to understand the causes of the changes in ice velocity of Laurichard rock glacier. We investigate the changes in the fluxes of ice masses across longitudinal and transversal profiles in order to be able to analyze in details the differences between the upper part and the front of the glacier. Using a combination of remote sensing data from 1952 (historical aerial images) until 2018 (Pléiades high-resolution satellite images), we documented the three-dimensional evolution of the Laurichard rock glacier during the last 60 years. We calculated the surface flow velocity between 1952 and 2018 using a feature-tracking algorithm at a resolution of 1 m and a precision of 0.5 m. Digital elevation models were assembled using the SfM techniques for aerial images, and the AMES stereo pipeline for Pléiades data. In addition, we made the analysis using in-situ annual velocities and temperatures data allowing to understand better which factors mostly explain the kinematic behavior.  We reconstructed a time series of changes in surface elevation by systematically co-registering and differencing DEMs between 1952 and 2018, with an average precision of 1 m. We first observed that the average annual horizontal velocity measured had increased progressively from 0.65 m yr-1 to 1.1 m yr-1 to 1.5 m yr-1 for the periods 1952-1960, 1994-2003 and 2013-2018, respectively. On the other hand, the surface mass changes and long term monitoring of mass transport show for all analyzed periods a clear negative surface elevation change of 2 m on average, between 1952 and 2018. The area with most of the elevation changes is the frontal part of the glacier, which is consistent with the increase in speed, which represents a mass exchange from the upper part to the front. We conclude that the rates of rock glacier mass transport have increased during the last 20 years and hypothetize, for this rock glacier, a transition state controlled mainly by local topographical factors which will eventually lead to high speed rock glacier or rock glacier destabilization.
Combination Service for Time-variable Gravity Fields (COST-G) – operations
Authors: Meyer Ulrich , Jäggi Adrian , Flechtner Frank , Dahle Christoph , Mayer-Gürr Torsten , Kvas Andreas , Lemoine Jean-Michel , Bourgogne Stéphane , Groh Andreas , Eicker Annette , Meyssignac Benoit
Published: March 2020

With the release of the combined GRACE monthly gravity field time-series COST-G RL01 the Combination Service for Time-variable Gravity fields (COST-G) of the International Association of Geodesy (IAG) became operational in July 2019. We present the COST-G RL01 time-series and provide validation in terms of orbit fit, ice mass trends, lake altimetry and sea level budget. We identify weak points in the combined monthly gravity fields and discuss possible improvements of the combination strategy for future combinations.

While COST-G RL01 is based on sets of re-processed GRACE monthly gravity fields, COST-G also provides combinations of monthly Swarm high-low satellite-to-satellite tracking (hl-SST) gravity fields on an operational basis with a latency of 3 months. Combinations of GRACE-FO monthly gravity fields are in the process of operationalization. We provide a status report and first results of GRACE-FO combinations. Combined GRACE, Swarm and GRACE-FO gravity fields complement each other to provide a long-term time-series of mass variation in the system Earth.
Monitoring precipitation convective clouds with collocated hyperspectral infrared sounder and imager measurements
Authors: Gong Xinya , Li Jun , Li Zhenglong , Moeller Christopher C.
Published: March 2020

Typically, DCCs are identified by 11 µm band brightness temperature (BT11) lower than a fixed BT threshold. Another method of combining the brightness temperature difference (BTD) between a water vapor absorption channel and a window channel to its measurement noise ratio (BNR) is adopted and applied to DCC identification. This BNR method improves the DCC detections over the legacy method because it is less contaminated with high clouds not thick and bright enough. BNR detects fewer DCCs than BT11, but with more confidence. 

Using observations of the collocated Cross-track Infrared Sounder (CrIS) and the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the Suomi National Polar-orbiting Partnership (SNPP) from 2017 to 2018, the results show BNR has better performances than BT11 for identifying the DCC and monitoring reflective solar bands. When comparing to BT11, BNR has more robust and invariant time series of monthly reflectance for all RSBs. Because BNR affects more on the left tails (less reflective) of the histograms than the mode reflectance, the improvement is more significant on the mean values than the modes. This method can be applied to other imagers with collocated advanced infrared sounders for detecting DCCs and monitoring the calibration stabilities of RSBs. 

Recently, the hyperspectral infrared atmospheric sounders onboard China’s next-generation FengYun satellites, i.e. the Geosynchronous Interferometric InfraRed Sounder (GIIRS) on the FengYun-4 geostationary satellite series and the Hyperspectral Infrared Atmospheric Sounder (HIRAS) on the FengYun-3 polar orbiting meteorological satellite series, are in operation. Flown onboard the same platforms, the collocated (consistent in time and space) infrared sounders and imagers, provide mount of match-up measurements for the study of methodology and process for synergistic use of both infrared sounder and imager for multiple applications. The findings will provide scientific evidences for further enhancements and applications of future FengYun satellites and its observing system.
Impacts of climate change on extreme precipitation and dry spells in New Zealand
Authors: Nicotina Ludovico , Comola Francesco , Satyam Saket , Scudeler Carlotta , Prakash Mani
Published: March 2020

Global warming is expected to enhance El Niño Southern Oscillation (ENSO), with potential impacts on frequency and severity of floods and droughts in numerous countries of the Asia-Pacific region. However, the limited time coverage of historical records and the large uncertainties underlying climate model projections impair our ability to identify trends in extreme rainfall and dry spells. Here, we generate and analyze a long-term stochastic precipitation dataset for New Zealand that accounts for the potential effects of climate change. For this purpose, we draw on a 60 year-dataset of daily precipitation maps to identify the rainfall principal components and quantify their temporal correlations with the ENSO signal. We then generate a long-term stochastic set of daily rainfall maps correlated with ENSO projections, corresponding to different climate change scenarios. Our results indicate that climate change may lead to more intense precipitation in the Southern Alps during positive ENSO phases. Conversely, extreme precipitation is likely to increase in the North Island during negative ENSO phases. Our analyses also suggest that the duration of extreme dry spells may significantly increase along the east side of the North and South Islands during positive ENSO phases. These results may guide the implementation of effective adaptation and mitigation strategies against the increasing risk of natural catastrophes.
Application of the Cahn-Hilliard-type approach to the development of oscillatory zoning in minerals
Authors: Schmidt Katharina , Tajmanova Lucie , Khakimova Lyudmila
Published: March 2020

Preservation of mechanically-controlled microstructures can help us to unravel the long-term stress state in geological materials. To better understand the stress state in such a microstructure, we need to quantify the processes in a coupled, chemo-mechanical, point of view. One of such a mechanically-controlled microstructure is oscillatory zoning in high-temperature metamorphic rocks. The presented example is a sharp zoned plagioclase of 150 x 200 µm size with thin compositional lamellae of 1-10 µm alternating from the core towards the rim. This microstructure is interpreted to be mechanically-controlled, since conventional diffusion failed to preserve the observed microstructure within timescales that would be reasonable from a regional geology point of view. In contrast, considering that chemical diffusion is coupled to mechanical deformation the observed zoning can be maintained over the geologically-relevant timescales.

Despite of the recent valuable progress in our understanding of these microstructures, the mechanisms controlling its evolution from slowly cooled rocks are still not complete. Here, we numerically investigate the coupled, chemo-mechanical, effect that generates oscillatory zones mechanically maintained over geologically relevant timescales. We test the possibility of modelling oscillatory zoning in minerals that is similar to the exsolution process. We apply a classical Cahn-Hilliard-type equation where we add more complexity considering the impact of deformation during the process.
Local-scale and spatially explicit response of tropical forests to climate change
Authors: Hofhansl Florian , Huber Werner , Weissenhofer Anton , Wanek Wolfgang , Franklin Oskar
Published: March 2020

Currently applied dynamic vegetation models do not realistically represent forest ecosystem processes and thus are not able to reproduce in-situ observations of forest ecosystem responses to drought. This is due to the fact that models typically rely on plant functional types to forecast the functional response of vegetation to climate change and to anthropogenic disturbance. However, recent observations of divergent ecosystem responses between topographic forest sites, differing in the availability of water and nutrients, indicate that we should no longer rely on this outdated concept but rather should explore new avenues of representing vegetation dynamics and associated climate change response in next-generation approaches.

Global climate change scenarios forecast increasing severity of climate extremes in association with El Niño–Southern Oscillation (ENSO). Such climate anomalies have been shown to affect forest ecosystem processes such as net primary productivity, which is determined by climate (precipitation, temperature, and light) and soil fertility (geology and topography). However, more recently it has been suggested that the impact of such climate fluctuations on forest productivity was strongly related to local site characteristics, which determined the sensitivity of forest ecosystem processes to climate anomalies.

We propose a novel approach integrating in-situ observations with remotely sensed estimates of forest aboveground productivity for parameterization of next-generation vegetation models capable of forecasting realistic forest ecosystem responses under future scenarios. Our approach considers local site characteristics associated with topography and disturbance history, both of which determine the sensitivity of forest aboveground productivity to projected climate anomalies. Our results therefore should have crucial implications for management and restoration of forest ecosystems and could be used to refine estimates of forest C sink-strength under future scenarios.
Imaging organo-mineral associations of creek sediments
Authors: Eusterhues Karin , Thieme Jürgen , Lühl Lars , Haidl Andreas , Heym S. Johannes , Adrianov Konstantin , Dehlinger Aurelie , Rehbein Stefan , Wilhein Thomas , Kanngießer Birgit , Totsche Kai Uwe
Published: March 2020

Interactions of organic matter with mineral surfaces are seen as one of the important mechanisms to increase carbon preservation in soils. Often, the mineral associated organic matter is assumed to consist of microbial derived material, because of its small C/N ratio and its isotopic signature.

We sampled sediments and surface water flocs from a small creek (pH 6.4) to obtain natural samples with a much higher microbial versus plant derived organic matter input than expected for soils. The bulk material was investigated by CNS analysis, X-ray diffraction (XRD), and infrared spectroscopy (FTIR). Organo-mineral associations were imaged by a combination of atomic force microscopy (AFM), scanning electron microscopy (SEM), and X-ray fluorescence spectroscopy (STXM-XRF) at 2550 eV (S, P, Si, Al, Fe) and 320 eV (C) at a spatial resolution of 50 nm. The speciation of C and P was addressed by near edge X-ray absorption fine structure spectroscopy (STXM-NEXAFS). Synchrotron measurements were performed at the PO4 beamline at PETRA III using the Animax STXM endstation with a 4-channel fluorescence detector with a solid angle of detection of up to 1.1 sr.

Organic matter was mainly found on Fe oxides (ferrihydrite). However, the C concentration on the Fe oxides varied and some Fe oxides were not covered by organic matter. Clay minerals (mainly illite) were either free of organic matter or showed a lower concentration of organic matter than the Fe oxides. Phosphorus was only observed on some of the Fe oxides surfaces and its P K-edge NEXAFS spectrum usually showed a small pre-edge peak at ~2150 eV, which can be taken as evidence for inner-sphere Fe-O-P bonds. Although Fe oxides were often found in close proximity of bacterial cells, the Fe oxide-associated organic matter was rich in carbonyl C and O-alkyl C, but showed higher contributions of aryl C and/or alkyl C than pure extracellular polymeric substances (EPS) or bacterial cells.

Our observations confirm a high reactivity of Fe oxides towards organic matter and phosphate. However, the Fe oxides were not fully coated, i.e. saturated with organic matter. The mineral associated organic matter was not similar to EPS or bacterial cells.
COST Action Underground4value: Living Labs for the Underground Built Heritage valorisation
Authors: Pace Giuseppe
Published: March 2020

Underground4value (COST Action CA18110) is a four years’ project (2019-2023) establishing an expert network from twenty-nine countries, with the objective of promoting balanced and sustainable approaches for the conservation and promotion of underground built heritage (UBH). Every year, four underground sites and their local communities become places for experimenting studies, new policies, and participatory approaches. During the first year (April 2019 - March 2020), the sites of Naples (Italy), La Union (Murcia, Spain), Postojna (Slovenia) and Göreme (Cappadocia, Turkey) have been selected. The originality of the approach is that it is geared towards assisting local communities’ decision-making with cultural, scientific and technical knowledge of the underground built heritage, from many different perspectives: archaeology, geo-technics, history, urban planning, cultural anthropology, economics, architecture, cultural tourism, ecology.

The Living Lab approach is used to organise fieldwork, spending time on each site with a mix of participants (international scientists and local practitioners). The idea is to identify and explore social innovations models for empowering local communities and making them part of the UBH promotion process. Collected information is then the basis for developing new research and training, which remain open and accessible. Knowledge transfer is secured by several dedicated tasks, including a Training School, held in last February in Naples, where the trainees have morning learning sessions and afternoon research activities on specific topics occurred in the living labs’ activities.
Implications of root exudates on the formation of rhizosheaths
Authors: Rahim Riffat , Haupenthal Adrian , Kroener Eva
Published: March 2020

Root exudates stimulate microbial activity and functions as a binding and adhesive agent that increases aggregate stability in the rhizosphere. The exudates produced from plant roots and microorganisms in the rhizosphere play a significant role in the formation of rhizosheath. Rhizosheaths comprises the soil that adheres to the roots with the help of root hair and mucilage even when it is removed from the surrounding soil. Low surface tension and great viscosity stabilize soil aggregates in surrounding root and develop rhizosheath formation. To our knowledge, no investigations are made on the influence of root exudates in soil rhizosheath formation, although it is well documented the formation and stabilization of rhizosheath of maize plants under various soil water contents but the influence of root exudates on the rhizosheath formation associated with other rheological properties is still missing. Such knowledge will greatly enhance the understanding of how rhizosheath is formed under different root and seed exudates and the effect of their physiochemical properties on the adhesion properties of mucilage will be studied in this project.

The aim of this study is to provide the first combined quantitative data on how root and seed exudates of different plants affect rhizosheath formation. We hypothesized that mucilage will contribute to the formation of rhizosheaths.  For this, we will use the mucilage of chia seeds which acts as a modelled plant root mucilage and mix it with soil in five different concentrations. After preparing the soil with mucilage, artificial roots (flax cords) will be incorporated in this soil and after drying and wetting cycles roots will be removed and the mucilage adhesion, simulation and rheological properties will be investigated under various soil water contents, soil texture, soil type, and soil compaction.

Key words:

                   Rhizosheath, mucilage, drying and wetting cycles and soil structure

 
What happens below construction pits? - The long-term erosion of temporary barriers to groundwater flow
Authors: Zech Alraune , Dekker Joris , Sweijen Thomas
Published: March 2020

Injection of grout material is widely used to create a temporary flow barrier at construction sites in the Netherlands. We investigate the long-term erosion behavior of a grout layer by means of semi-analytical expressions for groundwater flow and transport.

A typical grout injection contains sodium-meta silicate, water and solidifier forming a temporarily impermeable ‘waterglass’. The combination of a waterglass layer and vertical walls allow for dry excavations below the groundwater table. After construction is finished, the waterglass remains in the subsurface and erodes over time. A question concerning the potential risk to groundwater quality remains: How high is the concentration of dissolved waterglass in the groundwater leaving the site?

Numerical simulations allow to describe the flow and transport for site specific conditions. However, it’s missing an analytical expression to predict the transport behavior for arbitrary settings. We approximate the erosion behavior by a set of semi-analytical equations. The challenge here is the change in permeability of the waterglass layer from almost impermeable to fully permeable. We define a dilution ratio relating the flux into the construction site to the flux through the layer as a measure of dissolved waterglass concentration leaving the site. We also determine the impact of design parameters such as construction site aspect ratio, depth of the waterglass layer and its thickness. We checked our results against numerical simulations for a range of parameter settings. Preliminary results show that erosion is initially slow and accelerates until the temporary injection layer is completely gone.
Low-cost interferometric optical fibre-based sensor for landslide monitoring: laboratory tests under different applications
Authors: Ivanov Vladislav , Longoni Laura , Ferrario Maddalena , Brunero Marco , Papini Monica
Published: March 2020

Landslide monitoring must keep pace with the development of technology. The costs of elaborate monitoring tools could however be quite elevated, especially when considering that monitoring instruments in direct contact with the measurand could undergo irreversible damage and thus be obliterated. A variety of landslide monitoring tools based on the optical fibre technology have emerged in the past few decades. While authors tend to focus on the reduced costs of the sensing cables, the economic and practical aspects related to the interrogating systems are often disregarded. In fact, commercially available units are hardly exploitable outside the laboratory. In this regard, we propose a newly developed interferometric optical fibre-based monitoring system which offers high sensitivity strain monitoring at a significantly reduced cost of the instrumentation involved. Moreover, the devised setup could easily be exported for field use. The setup has been tested in controlled conditions as a monitoring tool in a downscaled landslide model. Two major modes of operation have been experimented: a) direct strain sensor where the optical fibre cable undergoes deformation, and b) a high frequency elastic wave detection mode where the sensor is able to distinguish the energetic footprint generated by ground movement. The two experimental schemes indicate that the newly developed sensing system could eventually be put into effective use for a variety of landslide phenomena where the most appropriate mode of application would depend of the circumstances of the problem under investigation. The design of a field application of the monitoring tool are currently underway.
Will warmer winters induce more forest and crop pests in Switzerland?
Authors: Schneider Léonard
Published: March 2020

Will warmer winters induce more forest and crop pests in Switzerland?

Léonard Schneider*,**

*Institute of Geography, University of Neuchatel, Espace Tilo-Frey 1, 2000 Neuchatel (leonard.schneider@unine.ch)

**Swiss Federal Research Institute WSL, Zürcherstrasse 111, 8903 Birmensdorf

 

With current global warming, recent winters have often been milder in Switzerland than they were in previous decades and should still become more so in the coming decades. Some insect species sensitive to winter extreme cold events could increase their survival rates during the cold season. Forest pests, such as pine processionary moth (Thaumetopoea pityocampa), green spruce aphid (Elatobium abietinum), and some crop pests, such as southern green stink bug (Nezara viridula), could overwinter more easily in Switzerland. These species are affected by temperatures below -12°C (Thaumetopoea pityocampa, Elatobium abietinum) to below -8°C (Nezara viridula).

This research aims to determine to what extent the evolution of winter minimum temperatures could increase the winter survival rate of some pest species in various places in Switzerland. We examine the trends for winter temperatures, with a special focus on cold events (days with minimal air temperature below -8°C and -12°C). We first analyse daily air temperature between 1980 and 2019 using 67 meteorological stations located all over Switzerland. Then, we use available data from CH2018 climatic scenarios to estimate possible trends along the coming century.

Preliminary results showed that the frequency of cold days has been decreasing in Switzerland over the last 40 years even though winter minimum temperatures have been increasing less than yearly minimum temperatures. By the end of the 21st Century, occurrences of temperatures below -12°C could become irregular up to 1700 m and winters with temperatures below -8°C could become rare at lower elevations in Switzerland. As a consequence, some crop pests such as southern green stin bug could overwinter more easily on the Swiss Plateau, and some forest pests such as green spruce aphid and pine processionary moth could reach higher elevations in mountain areas by the end of the century.
Macroplastics Pollution in the Southern North Sea – Sources, Pathways and Abatement Strategies
Authors: Wolff Jörg-Olaf , Hahner Florian , Meyerjürgens Jens , Ricker Marcel , Schöneich-Argent Rosanna Isabel , Badewien Thomas , Lettmann Karsten Alexander , Schaal Peter , Freund Holger , Mose Ingo , Stanev Emil , Zielinski Oliver
Published: March 2020

Since 2016, an interdisciplinary consortium at the Carl von Ossietzky University in Oldenburg has been funded by the Lower Saxony Ministry for Science and Culture in order to provide solid, scientific knowledge of the sources, pathways and accumulation zones of plastic litter. This team consists of physical oceanographers, geoecologists, biologists and environmental planners.

Using simple wooden drifters, GPS-drifters and high resolution, numerical modelling, the consortium studied the dispersal of floating macroplastics (i.e. visible plastic fragments and objects) and accumulation areas within the German Bight and the Wadden Sea. Furthermore, coastal sensors and observation systems were employed to gather data of hydrodynamic parameters. In addition, the general public has actively participated in the collection of litter data via a web-based registration system for reporting the findings of wooden drifters.

In this presentation we will highlight some of the most important results of the project amongst them the surprising observation of a complete reversal of the circulation in the southern North Sea in March 2018, supported by drifter reports from citizen scientists from Britain. We will also shortly shed light on the heavy workload involved with presentations to the public (Radio, TV, print media, presentations to various stakeholder groups) which future projects should anticipate already at the planning stage.