bluuebunny/crossref_metadata_2025 huggingface dataset:
The Holocene Cedrus pollen record from Sierra Nevada (S Spain), a proxy for climate change in N Africa
Authors: Jiménez-Moreno Gonzalo , Anderson R. Scott , Ramos-Román María J. , Camuera Jon , Mesa-Fernández Jose Manuel , García-Alix Antonio , Jiménez-Espejo Francisco J. , Carrión José S.
Published: March 2020

In this study, we synthesized pollen data from seven sites from the Sierra Nevada in southern Spain to investigate the response of forests in the western Mediterranean area to centennial- and millennial-scale climate changes and to human impact during the Holocene. In particular, here we focused in Cedrus pollen abundances, which most-likely originated from Northern Africa and were carried to Sierra Nevada by wind. Although Cedrus abundances are generally lower than 1% in the studied pollen samples, a comparison with North African pollen records shows similar trends at long- and short-term time-scales. Therefore, this record could be used as a proxy for changes in this forest species in North Africa. A Middle and Late Holocene Cedrus pollen increasing trend has been observed in the Sierra Nevada synthetic record, which seems to be the result of decreasing summer insolation. This would have produced overall cooler annual temperatures in Northern Africa (Atlas and Rif Mountains), benefiting the growth of this cool-adapted montane tree species, and lower summer evaporation, increasing available moisture during the summer, which is critical for this water-demanding species. Millennial- and centennial-scale variability also characterize the Sierra Nevada Cedrus synthetic record. Cedrus abundance oscillations could have been produced by well-known millennial-scale climatic variability that controlled cedar abundance in montane areas of N Africa.  
Using a data-driven network to understand the drivers of soil organic carbon dynamics across the tropic
Authors: Winowiecki Leigh , Vågen Tor-Gunnar
Published: March 2020

Maintaining soil organic carbon (SOC) content is recognized as an important strategy for a well-functioning soil ecosystem. The UN Convention to Combat Desertification (UNCCD) recognizes that reduced SOC content can lead to land degradation, and ultimately low land and agricultural productivity. SOC is almost universally proposed as the most important indicator of soil health, not only because SOC positively influences multiple soil properties that affect productivity, including cation exchange capacity and water holding capacity, but also because SOC content reflects aboveground activities, including especially agricultural land management. To be useful as an indicator, it is crucial to assess the importance of both inherent soil properties as well as external factors (climate, vegetation cover, land management, etc.) on SOC dynamics across space and time. This requires large, reliable and up-to-date soil health data sets across diverse land cover classes. The Land Degradation Surveillance Framework (LDSF), a well-established method for assessing multiple biophysical indicators at georeferenced locations, was employed in nine countries across the tropics (Burkina Faso, Cameron, Honduras, India, Indonesia, Kenya, Nicaragua, Peru, and South Africa) to assess the influence of land use, tree cover and inherent soil properties on soil organic carbon dynamics. The LDSF was designed to provide a biophysical baseline at landscape level, and monitoring and evaluation framework for assessing processes of land degradation and the effectiveness of rehabilitation measures over time. Each LDSF site has 160 – 1000 m2 plots that were randomly stratified among 16 - 1 km2 sampling clusters. A total of 6918 soil samples were collected (3478 topsoil (0-20 cm) and 3435 subsoil (20-50 cm)) within this study. All samples were analyzed using mid-infrared spectroscopy and 10% of the samples were analyzed using traditional wet chemistry to develop calibration prediction models.  Validation results for soil properties (soil organic carbon (SOC), sand, and total nitrogen) showed good accuracy with R2 values ranging between 0.88 and 0.96. Mean organic carbon content was 21.9 g kg-1 in topsoil and 15.2 g kg-1 in subsoil (median was 18.3 g kg-1  for topsoil and 10.8 g kg-1 in subsoil). Forest and grassland had the highest and similar carbon content while bushland/shrubland had the lowest. Sand content played an important role in determining the SOC content across the land cover types. Further analysis will be conducted and shared on the role of trees, land cover and texture on the dynamics of soil organic carbon and the implications for LDN reporting, land restoration initiatives as well as sustainable land management recommendations.
Polytope: Serving ECMWFs Big Weather Data
Authors: Hawkes James , Manubens Nicolau , Danovaro Emanuele , Hanley John , Siemen Stephan , Raoult Baudouin , Quintino Tiago
Published: March 2020

Every day, ECMWF produces ~120TiB of raw weather data, represented as a six-dimensional dataset. This data is used to produce approximately 30TiB of user-defined products, which are disseminated worldwide. The raw data is also stored in the world's largest meteorological archive (MARS), currently holding over 300 PiB of primary data -- which is also served around the world on demand. As the resolution of ECMWFs global weather models increase over the next few years, the amount of raw data produced per day will increase into the petabytes, and the distribution of products and archived data becomes impossible. In-situ, on-the-fly data extraction and processing are required to sustain and increase the accessibility of ECMWFs big weather data.

 

To meet these requirements, ECMWF is developing Polytope -- an open-source service which allows users to request arbitrary n-dimensional stencils ("polytopes") of data from highly-structured n-dimensional datasets. The data extraction is performed server-side (collocated with the data), allowing for large data reduction prior to transmission and less complexity for the user. For example, a user could request a polytope describing a flight path -- simultaneously crossing temporal and spatial axes. Polytope will return just a few bytes of data rather than large structured arrays of geo-spatial data which must be further post-processed by the user.

 

Polytope is being partly developed under LEXIS, an EU-funded Horizon 2020 project which focuses on large-scale HPC & cloud workflows. The emphasis of LEXIS is on how HPC and cloud systems interact; how they can share data; and methods to compose workflows of tasks running on both cloud and HPC systems. Polytope will be used to provide a cross-centre weather and climate data API which connects to multiple high-performance data sources across Europe, and serves multiple cloud environments with this data.

 

This poster will present the early developments and future vision of Polytope. It will also illustrate how it is used within the LEXIS project to enable complex weather and climate workflows, involving global forecasts, regional forecasts and cloud-based simulations.
Acoustic analysis of starting jets in an anechoic chamber
Authors: Sesterhenn Jörn Lothar , Peña Fernández Juan Jose , Cigala Valeria , Küppers Ulrich , Dingwell Don
Published: March 2020

Explosive volcanic eruptions emanate complex acoustic signals. They
are influenced by several parameters, most of most of which are highly
unconstrained in volcanic setting.

We investigate the acoustics of starting jets analogous to
volcanic jets at high Mach numbers and with different nozzle
geometries, in a controlled environment. For the first time in
volcanic analog studies, an anechoic chamber is used to eliminate
contamination of the signals by reflections from any wall or
obstacle.  The analysis concentrates on the identification of the
principal jet noise components including: compression waves, vortex
ring noise, turbulent jet mixing noise,  broadband shock noise and
screech. We employed a shock tube apparatus and signals were recorded
using a microphone array.  Employing wavelet analysis, we have
identified the noise sources in both time- and frequency-space.

We have identified the principal sound sources of the jet in
time-frequency space and have analyzed their behaviour with respect to
changes in pressure ratio $p/p_\infty$ ,non-dimensional mass supply
L/D and exit-to-throat area ratio.

We find that at higher pressure ratios the peak frequency of the
broadband shock noise is noticeably lower whereas the amplitude is
higher. The non-dimensional mass supply controls whether a jet forms
and its blowing duration and maximum velocity. The nozzle geometry has
a markable effect on delay of the shock-shear layer-vortex ring
interaction with respect to the compression wave.

Changes in parameters of the starting jet leave a clear and
interpretable trace in the observed sound pattern. This quantitative
parametrisation of these effects is essential for utilizing these
findings as well as field observations for the solution of the inverse
problem in the lab and in nature.

 
Response of soil N2 and N2O fluxes to denitrification control factors in two agricultural soils
Authors: Matson Amanda , Burkart Stefan , Grosz Balazs , Köster Jan Reent , Merl Simone , Well Reinhard
Published: March 2020

Controlling soil N cycling to mitigate N-oxide emissions and optimize N use efficiency is an important aspect of agricultural soil management. Numerous denitrification models exist that can inform management decisions, but these are limited by the lack of soil N2 flux measurements to validate the model estimates. Measurements of soil denitrification - including both N2O and N2 fluxes - are challenging, however, due to methodological limitations for the measurement of N2 and the spatial/temporal heterogeneity of denitrification in soils.

We used laboratory incubations of re-packed soil cores, combined with both soil flushing and stable isotope techniques, to measure denitrification in two agricultural soils, as part of the DFG-research unit “Denitrification in Agricultural Soils: Integrated Control and Modelling at Various Scales (DASIM)”. The laboratory incubations used an automated mesocosm system, with regular measurements of both N2O and N2, to assess the response of soil denitrification to a variety of control factors. Control factors simulated typical scenarios that might occur in the field, including different amounts/types of plant residue, and changes in moisture, temperature, NO3- and oxygen concentration. Both natural abundance and 15N labeling of the soil mineral N pool were used to assess denitrification pathways.

Here we contrast the results of the incubation data from a sandy Podzol and silt-loam Luvisol. These data will be used to calibrate newly developed DASIM models as well as denitrification sub-modules of existing biogeochemical models. They will also inform the next steps of this work, which will extend the laboratory incubation technique to measure denitrification in undisturbed field soils.
Quantifying synergies and trade-offs in the water-land-energy-food-climate nexus using a multi-model scenario approach
Authors: Doelman Jonathan , Kram Tom , Bodirsky Benjamin , Weindle Isabelle , Stehfest Elke
Published: March 2020

The human population has substantially grown and become wealthier over the last decades. These developments have led to major increases in the use of key natural resources such as food, energy and water causing increased pressure on the environment throughout the world. As these trends are projected to continue into the foreseeable future, a crucial question is how the provision of resources as well as the quality of the environment can be managed sustainably.

Environmental quality and resource provision are intricately linked. For example, food production depends on availability of water, land suitable for agriculture, and favourable climatic circumstances. In turn, food production causes climate change due to greenhouse gas emissions, and affects biodiversity through conversion of natural vegetation to agriculture and through the effects of excessive fertilizer and use of pesticides. There are many examples of the complex interlinkages between different production systems and environmental issues. To handle this complexity the nexus concept has been introduced which recognizes that different sectors are inherently interconnected and must be investigated in an integrated, holistic manner.

Until now, the nexus literature predominantly exists of local studies or qualitative descriptions. This study present the first qualitative, multi-model nexus study at the global scale, based on scenarios simultaneously developed with the MAgPIE land use model and the IMAGE integrated assessment model. The goal is to quantify synergies and trade-offs between different sectors of the water-land-energy-food-climate nexus in the context of sustainable development goals (SDGs). Each scenario is designed to substantially improve one of the nexus sectors water, land, energy, food or climate. A number of indicators that capture important aspects of both the nexus sectors and related SDGs is selected to assess whether these scenarios provide synergies or trade-offs with other nexus sectors, and to quantify the effects. Additionally a scenario is developed that aims to optimize policy action across nexus sectors providing an example of a holistic approach that achieves multiple sustainable development goals.

The results of this study highlight many synergies and trade-offs. For example, an important trade-off exists between climate change policy and food security targets: large-scale implementation of bio-energy and afforestation to achieve stringent climate targets negatively impacts food security. An interesting synergy exists between the food, water and climate sectors: promoting healthy diets reduces water use, improves water quality and increases the uptake of carbon by forests.
Applying economic complexity to agriculture: new indicators for water security
Authors: Sciarra Carla , Chiarotti Guido , Ridolfi Luca , Laio Francesco
Published: March 2020

The application of complex network theory to economics has given the chance to define the hidden capabilities (i.e., natural and human resources, investments, finances, etc.) of production of countries whose economic growth is determined. This application is known as economic complexity and it evaluates the hidden capabilities of production by exploiting the data on the international trade of goods. The outcomes of the economic complexity methodologies are a ranking of the countries, according to their economic growth potential, and a ranking of the products, according to the capabilities required for their production and export (more sophisticated products require more capabilities).

The idea lying beyond the economic complexity framework is replicable and it can be effectively used in other fields beyond economics. A first example is ecology, where the approach is used to rank the species interacting in an ecosystem. A second example is eco-hydrology, where the methodologies of economic complexity have been used to rank countries according to their virtual water consumption.

Here, we propose to exploit the approach of economic complexity to define a ranking of countries according to the sustainability of the water used in agriculture. For each country, we define the amount of blue water used for irrigation, categorized according to the sources of water withdrawal (i.e., groundwater or surface water discretized with different thresholds depending on the rechargeability of the sources). To structure the data as a bipartite network of countries-sources allows one to rank countries according to the impact of their agriculture on the global water resources, while ranking the sources of blue water for their sustainability. In this view, less valued water sources – in the sense of being more rechargeable – are found at the bottom of the ranking, while more valued water sources, as the fossil ones, are found at the top positions. Our results reveal the performance of countries in terms of their water management strategies. This approach could pave the way to a new class of indicators of water security and management that could help policy makers in the definition of new strategies for granting water security on a global scale.
Role of Saharan dust and black carbon deposition on snow cover in the French mountain ranges over the last 39 years.
Authors: Réveillet Marion , Dumont Marie , Gascoin Simon , Nabat Pierre , Lafaysse Matthieu , Nheili Rafife , Tuzet François , Menegoz Martin , Ginoux Paul
Published: March 2020

Light absorbing particles such as black carbon(BC) or mineral dust are known to darken the snow surface when deposited on the snow cover and amplify several snow-albedo feedbacks, drastically modifying the snowpack evolution and the snow cover duration. Mineral dust deposition on snow is generally more variablein time than black carbon deposition and can exhibit both a high inter and intra annual variability. In France, the Alps and the Pyrenees mountain ranges are affected by large dust deposition events originating from the Sahara . The aim of this study is to quantify the impact of these impurities on the snow cover variability over the last 39 years (1979-2018).

For that purpose, the detailed snowpack model Crocus with an explicit representation of impurities is forced by SAFRAN meteorological reanalysis and a downscaling of the simulated deposition fluxes from a regional climate model (ALADIN-Climate). Different simulations are performed: (i) considering dust and/or BC (i.e. explicit representation), (ii) without impurities and (iii) considering an implicit representation (i.e. empirical parameterization based on a decreasing law of the albebo with snow age).

Simulations are compared at point scale to the snow depth measured at more than 200 Meteo-France’s stations in each massif, and spatially evaluated over the 2000-2018 period in comparing thesnow cover area, snow cover duration and the Jacard index to MODIS snow products. Scores are generally better when considering the explicit representation of the impurities than when using the snow age as a proxy for light absorbing particles content.

Results indicate that dust and BC have a significant impact on the snow cover duration with strong variations in the magnitude of the impact from one year to another and from one location to another.We also investigate the contribution of light absorbing particles depositionto snow cover inter-annual variability based on statistical approaches.
High-frequency dynamics near the shelf break southwest of Svalbard
Authors: Poulain Pierre-Marie , Cozzani Elisa , Pennucci Giuliana , Lewis Craig , Lathuiliere Cyril , Bordoix Lucie , Centurioni Luca
Published: March 2020

The high-frequency dynamics (including tidal and inertial currents, internal and coastal-trapped waves) on the shelf break/slope southwest of Svalbard were explored in September-October 2019 using a variety of mobile and fixed sensors operated as part of the NARVAL19 Sea Trial. Ocean currents, temperature and salinity were measured in the water column with 6 moorings, 3 gliders and a wirewalker profiler. In addition near-surface (15 m) currents were measured with 24 satellite-tracked drifters.

The collected data show some variability, mostly near the surface, associated with the lateral displacements or meandering of the Polar Front separating cool and low salinity waters on the shelf and warmer/saltier waters of Atlantic origin. The most striking signal, however, is at depth (in and below the thermocline) in the form of internal waves at semidiurnal tidal frequency.

Preliminary results of spectral and harmonic analyses of the data collected by all the platforms are presented and discussed.
Systemic modelling of soil functions under the impact of agricultural management
Authors: König Sara , Weller Ulrich , Lang Birgit , Ließ Mareike , Mayer Stefanie , Stößel Bastian , Vogel Hans-Jörg , Wiesmeier Martin , Wollschläger Ute
Published: March 2020

The increasing demand for food and bio-energy gives need to optimize soil productivity, while securing other soil functions such as nutrient cycling and buffer capacity, carbon storage, biological activity, and water filter and storage. Mechanistic simulation models are an essential tool to fully understand and predict the complex interactions between physical, biological and chemical processes of soil with those functions, as well as the feedbacks between these functions.

We developed a systemic soil model to simulate the impact of different management options and changing climate on the named soil functions by integrating them within a simplified system. The model operates on a 1d soil profile consisting of dynamic nodes, which may represent the different soil horizons, and integrates different processes including dynamic water distribution, soil organic matter turnover, crop growth, nitrogen cycling, and root growth.

We present the main features of our model by simulating crop growth under various climatic scenarios on different soil types including management strategies affecting the soil structure. We show the relevance of soil structure for the main soil functions and discuss different model outcome variables as possible measures for these functions.

Further, we discuss ongoing model extensions, especially regarding the integration of biological processes, and possible applications.
Interfacing FORTAN Code with Python: an example for the Hydrus-1D model
Authors: Collenteur Raoul , Vremec Matevz , Brunetti Giuseppe
Published: March 2020

HYDRUS-1D is a popular software suite for one-dimensional modeling of flow and transport through the vadose zone [1]. Models can be handled through the Graphical User Interface (GUI), made freely available by the original authors (https://www.pc-progress.com/). As the program is file-based, the HYDRUS-1D GUI already ensures a certain degree of reproducibility, as these files contain all information about a model. The original FORTRAN code of the HYDRUS-1D model is also made available and is used in many publications to perform more complicated analysis of flow and transport through the unsaturated zone. For each of these publications new code was programmed to change the input files and perform a specific analysis. Being a popular hydrological model, it seems only logical to start reusing such code and structurally develop its capabilities. In the presentation, we introduce Phydrus, an open source Python package to create, optimize and visualize HYDRUS-1D models. Python scripts or Jupyter Notebooks are used for all steps of the modeling process, documenting the entire workflow and ensuring reproducibility of the analysis. Connecting HYRDUS-1D to Python makes it easier to perform repetitive tasks on models, and potentially opens up a whole new set of possibilities and applications. While introducing Phydrus, this presentation will also focus on the process of creating the Python Package and why we think it is worthwhile for the hydrologic community to interface existing (older) code with newer programming languages popular in the hydrological scientific community.

References
[1] Šimůnek, J. and M. Th. van Genuchten (2008) Modeling nonequilibrium flow and transport with HYDRUS, Vadose Zone Journal.
The use of high-speed camera technique for observation of soil splash phenomena
Authors: Beczek Michał , Ryżak Magdalena , Mazur Rafał , Sochan Agata , Polakowski Cezary , Bieganowski Andrzej
Published: March 2020

Soil, i.e. the natural outer layer of the lithosphere and an important component of many ecosystems, may be subjected to various degradation processes dependent on different factors. One of the forms of degradation is water erosion, where the first stage is the splash phenomenon. This process is caused by water drops hitting the soil surface during rainfall, which results in detachment and ejection of splashed material and transport thereof over different distances. The aim of this study was to present the application of the high-speed camera technique for investigations of surface phenomena (effects) influenced by the impact of a single water-drop onto the soil surface.

The measurements were conducted on types of soil differentiated in terms of texture and variants of initial moisture content, which helped to observe different aspects of the soil splash phenomenon. Water drops with a diameter of 4.2 mm fell on soil samples with various kinetic energy values depending on the height of the drop fall (up to 7m). Phantom Miro M310 high-speed cameras were used to observe the effects of the drop impact. The devices registered images with a speed of 3260 fps (frames per second) at the highest available resolution (1280x800 pixels). The following phenomena were observed: I) ejection of splashed particles (including solid soil particles, water droplets, solid particles within the water sheath); II) crown formation – when the drop impacting onto wet soil surface forces the liquid layer to rise up and form a crown (important for the mode and amount of transferred material); III) micro-crater formation – the deformation of the surface and formation of a shallow pool after the drop impact.          

 

This work was partly financed from the National Science Centre, Poland; project no. 2018/31/N/ST10/01757.

 

References:

Beczek M., Ryżak M., Sochan A., Mazur R., Bieganowski A.: The mass ratio of splashed particles during raindrop splash phenomenon on soil surface. GEODERMA 347, 40-48, 2019

Beczek M., Ryżak M., Lamorski K., Sochan A., Mazur R., Bieganowski A.: Application of X-ray computed microtomography to soil craters formed by raindrop splash. Geomorphology 303, 357-361, 2018

Beczek M., Ryżak M., Sochan A., Mazur R., Polakowski C., Bieganowski A.: The differences in crown formation during the splash on the thin water layers formed on the saturated soil surface and model surface. PLoS ONE 12, 2017
Simulating human mobility with a Lagrangian Constraint Random Walk Model based on climatic and environmental conditions
Authors: Klein Konstantin , Shao Yaping , Rostami Masoud
Published: March 2020

Archaeological records indicate that human population experienced frequent decline and growth as humans were on their way to populate the whole planet. Our hypothesis is that climate and environment were the main drivers for human existence and dispersal. Based on this hypothesis, we develop a Lagrangian Constraint Random Walk Model (CRW) to simulate the dispersal of hunter-gatherers. Human existence potential (HEP) is estimated using climate/environment model data, supported by archaeological evidence. The CRW simulates the movement of individual humans with a stochastic differential equation. While the movement of the individuals has a random component, it is constrained by a drift term which depends on the HEP. Population growth and decline are represented using a birth and a death term. Sociological elements of hunter-gatherers, such as population pressure, conflicts, and cooperation, are considered in the model. With the CRW, we estimate human mobility and dispersal based on the statistical behavior of a large ensemble of individuals. Furthermore, by varying the external factors and hence the HEP, we evaluate the response of hunter-gatherer societies to climate change. We will present the model and a case study on the mobility of hunter-gatherers on the Iberian Peninsula during the Last Glacial Maximum.
V-FOR-WaTer – a virtual research environment to access and process environmental data
Authors: Strobl Marcus , Azmi Elnaz , Hassler Sibylle K. , Mälicke Mirko , Meyer Jörg , Zehe Erwin
Published: March 2020

V-FOR-WaTer, as a virtual research environment, wants to simplify data access for environmental sciences, foster data publications and facilitate preparation of data and their analyses with a comprehensive toolbox. A large number of datasets, covering a wide range of spatial and temporal resolution, is still hardly accessible for others than the original data collector. Frequently these datasets are stored on local storage devices. By giving scientists from universities and state offices open access to data, appropriate pre-processing and analysis tools and workflows, we accelerate scientific work and facilitate the reproducibility of analyses.

The prototype of the virtual research environment was developed during the last three years. Today it consists of a database with a detailed metadata scheme that is adapted to water and terrestrial environmental data and compliant with international standards (INSPIRE, ISO19115). Data in the web portal originate from university projects and state offices. The connection of V-FOR-WaTer to established repositories, like the GFZ Data Services, is work in progress. This will simplify both, the process of accessing publicly available datasets and publishing the portal users’ data, which is increasingly demanded by journals and funding organisations.

The appearance of the web portal is designed to reproduce typical workflows in environmental sciences. A filter menu, based on the metadata, and a graphical selection on the map gives access to the data. A workspace area provides tools for data pre-processing, scaling, common hydrological applications and more specific tools, e.g. geostatistics. The toolbox is easily extendable due to the modular design of the system and will ultimately also include user-developed tools. The selection of the tools is based on current research topics and methodologies in the hydrology community. They are implemented as Web Processing Services (WPS); hence, the tool executions can be joined with one another and saved as workflows, enabling more complex analyses and reproducibility of the research.
The imprint of anammox on the stable isotope compositions of nitrogen-bearing molecules
Authors: Magyar Paul , Hausherr Damian , Niederdorfer Robert , Wei Jing , Mohn Joachim , Bürgmann Helmut , Joss Adriano , Lehmann Moritz
Published: March 2020

Stable isotope measurements of nitrogen and oxygen in nitrogen-containing molecules provide important constraints on the sources, sinks and pools of these molecules in the environment. Anammox is one of two known biological processes for converting fixed nitrogen to N2, and through its consumption of ammonium and nitrite and production of nitrate, it impacts the supply of a wide variety of fixed N molecules. Nevertheless, the isotope fractionations associated with the various anammox-associated redox reactions remain poorly constrained. We have measured the isotope effects of anammox in microbial communities enriched for the purpose of nitrogen removal from wastewater by anammox. In this system, we can replicate the ecological complexity exhibited in environmental settings, while also performing controlled experiments. We find that under a variety of conditions, the nitrogen isotope effect for the anaerobic oxidation of ammonium in this system (NH4+ to N2) is between 19‰ and 32‰, that for the reduction of nitrite (NO2– to N2) is between 7‰ and 18‰, and that for the production of nitrate (NO2– to NO3–) is between -16‰ and -43‰. We propose that these ranges reflect both (1) a mixture of signals from different anammox-performing species and (2) variation of the isotope effect associated with the anammox process within a given microbial community under different conditions. We seek to understand further what factors control this variability to better interpret stable isotope measurements of N-bearing molecules in environmental settings.
Climate change in mountains around the globe: Elevation dependencies and contrasts to adjacent lowlands
Authors: Arnone Enrico , Pepin Nick , Palazzi Elisa , Kotlarski Sven , Terzago Silvia , Seibert Petra , Formayer Herbert
Published: March 2020

Mountain and high elevation regions often show distinct climate trends in temperature and precipitation, which can contrast those of adjacent lowland regions. In the context of temperature, this phenomenon is known as elevation-dependent warming (EDW). Past temperature trends can increase with elevation, but this is not always so, and they may peak in a critical elevation band, or show more complex elevation profiles. This is controlled by a variety of mechanisms which may be responsible for the observed patterns, including snow albedo feedback, vegetation change, cloud and moisture patterns, aerosol forcing and their interactions.

We here present a literature-based meta-analysis of elevation profiles in recent warming rates and, in a more general context, temperature change in mountain regions around the globe. For the recent historical period (~1960-2010) we find that when comparing like with like (i.e. high elevation regions with adjacent low elevation regions) warming rates are mostly stronger at higher elevations. Warming rates have also increased over time, with more recent decades showing stronger warming. On a global scale there is no significant difference between mean warming rates in mountains and in other areas. Thus, elevation-dependency within regions can be masked by differences in geographical location in global meta-analyses. Although there have been far fewer studies on vertical profiles of precipitation changes, we extend our meta-analysis to consider this parameter,  where information is available.

In addition to the meta-analysis, we compare past temperature and precipitation changes in mountain and lowland regions using global gridded observation-based and reanalysis datasets (e.g. CRU, ERA5, NCEP2) and global climate model simulations (CMIP5). Despite the uncertainties of these datasets (e.g. inhomogeneous underlying station coverage and related interpolation errors, biases, coarse spatial resolution), they allow us to compare different mountain regions globally with the same level of accuracy. There are only a few mountain areas that show distinct differences when their temperature trends are compared with lowland surroundings, but patterns vary by dataset and region. We also explore different extensions of adjacent lowlands, which may influence the quantification of differences in temperature and precipitation trends at high and low elevation.

This historical assessment is completed by an analysis of model projections (CMIP5) for studying the expected future evolution of climate change in mountains and contrasts to adjacent lowlands
Slow rock mass deformation in the mountain side north of the Tungnakvíslarjökull outlet glacier in western part of the Mýrdalsjökull glacier
Authors: Sæmundsson Þorsteinn , Einarsson Páll , Belart Joaquin , Hjartardóttir Ásta Rut , Magnússon Eyjólfur , Geirsson Halldór , Pálsson Finnur , Pedersen Gro , Drouin Vincent
Published: March 2020

A large slow rock mass deformation has been detected in a mountain side north of the Tungnakvíslarjökull outlet glacier, located in the western part of the Mýrdalsjökull glacier in Iceland. A group of scientist from the University of Iceland, National Land Survey and Icelandic GeoSurvey have worked on collecting data from several sources and installed monitoring equipment at the site. According to observations, which were based on comparison of DEM from aerial photographs from 1945 to 2019, the slope has been showing slow rock mass deformation since at least 1945. The rate of movements has been estimated for the period from 1945 to 2019. The data show that the total displacement since 1945 is around 200 m. The data also indicate that the deformation rate has not been constant over this time period and the data shows that the maximum deformation was between 1999 and 2004 of total of 94 m or about 19 m/year.

The mountain slope north of the Tungnakvíslarjökull outlet glaciers reaches up to around 1100 m height. The head scarp of the slide, which is almost vertical, is around 2 km wide rising from about 4-500 m in the western part up to the Mýrdalsjökull glacier at 1100 m in the east. The total sliding from the head scarp down to the present day ice margin is around 1 km2. The total volume of the moving mass is not known as the sliding plane is not known, but the minimum volume might be between 100 to 200 million m3. The entire slope shows signs of displacement and is heavily fractured and broken up. A GPS station that was installed in the uppermost part of the slope in August shows that the slope is moving about 3-9 mm per day, at a constant rate since installation.

There are two main ideas of the causes for this slow rock mass deformation. One is the consequences of slope steepening by glacial erosion, followed by unloading and de-buttressing due to glacial retreat. Another proposed cause for the deformation is related to its location on the western flank of the Katla volcano. Persistent seismic activity in this area for decades may be explained by a slowly rising cryptodome, which may also explain the slope failure.
DROP: a DROught Probabilistic near-real time monitoring tool
Authors: Turco Marco , Jerez Sonia , Donat Markus , Toreti Andrea , Vicente-Serrano Sergio M. , Doblas-Reyes Francisco J.
Published: March 2020

Accurate and timely information of evolving drought conditions is crucial to take early actions and alleviate their impacts. A number of drought datasets is already available. They cover the last three decades and provide data in near-real time (using different sources), but they are all "deterministic" (i.e. single realisation), and data partly differ between them.  Here we first evaluate the quality of long-term and continuous climate data for timely meteorological drought monitoring considering the Standardized Precipitation Index. Then, by applying an ensemble approach, similarly to weather/climate prediction studies, we develop DROP (DROught Probabilistic; Turco et al. 2020), a new global land gridded dataset to monitor meteorological drought that gathers an ensemble of observation-based datasets providing near-real time estimates with associated uncertainty. This approach makes the most of the available information and brings it to the end-users. DROP, publicly available at https://drop.shinyapps.io/DROP/, is operationally updated every monthly and provides drought information in near-real time, i.e., up to the previous month. The high-quality and probabilistic information provided by DROP is useful for monitoring applications, and may help to develop global policy decisions on adaptation priorities in alleviating drought impacts, especially in countries where meteorological monitoring is still challenging.

 

References

Turco M, Jerez S, Donat M, Toreti M, Vicente-Serrano S M, Doblas-Reyes, F J. (2020). A global probabilistic dataset for monitoring meteorological droughts. Bulletin of the American Meteorological Society. Under review.

 

Acknowledgments

M.T. has received funding from the Spanish Ministry of Science, Innovation and Universities through the project PREDFIRE (RTI2018-099711-J-I00).

 
Uvalas and their relationship to sinkholes (dolines) in an evaporite karst setting
Authors: Watson Robert , Holohan Eoghan , Al-Halbouni Djamil , Alrshdan Hussam , Closson Damien , Dahm Torsten
Published: March 2020

Enclosed topographic depressions are characteristic of karst landscapes on Earth. The scale and morphological characteristics of such depressions are variable, but the most common depression type is a sinkhole (doline). Certain karst depressions that are much larger than sinkholes and that display gentler slopes and more complex three-dimensional shapes are known as uvalas. A single uvala typically contains numerous sinkholes within it. The developmental relationship between sinkholes and uvalas has been subject of debate, however, mainly because long developmental timescales impede direct observation in classical limestone karst, where such features are most commonly reported.

Here, we describe the development of five uvalas and numerous associated sinkholes in an evaporite karst setting on the eastern shore of the hypersaline Dead Sea. This karst landscape evolved rapidly over a 25-year period from 1992 to 2017 in response to the anthropogenically-driven decline in the Dead Sea level. Our remote sensing data and field observations show that both the sinkholes and the uvala-like depressions formed through subsidence in a very close spatio-temporal relationship. While many sinkholes developed initially in clusters, the uvalas developed around such clusters as larger-scale and gentler depressions that are structurally distinct both in space and time.

In agreement with inferences for examples in limestone karst settings, the uvalas in this evaporite karst setting do not form by a simple coalescence of sinkholes. Instead, these evaporite-karst uvalas form through subsidence (sagging), interpreted here as in response to distributed subsurface dissolution and physical erosion within a mechanically unstable subsurface volume (e.g. a groundwater conduit network). Sinkholes, on the other hand, are interpreted as discrete subsidence responses within that volume to smaller-scale zones of highly localised material removal (e.g. individual groundwater conduits). Our observations and interpretations are consistent with numerical modelling of subsidence produced by the development of multiple void spaces at progressively deepening levels. Morphometrically, our results also agree well in several respects with a recent re-evaluation of uvalas in some classical limestone karst areas. Consequently, this study helps to clarify the nature, occurrence and genesis of uvalas in karst systems generally.
On the features of the dynamics of the upper mixed layer of the ocean in the presence of shear flows
Authors: Soustova Irina , Gladskikh Daria , Troitskaya Yuliya , Ostrovsky Lev
Published: March 2020

In the framework of the modernized RANS model of turbulent closure [1], the evolution in the pycnocline and shear flow in the upper mixed layer of the ocean is studied. For this purpose, one of the variants of the model situation is considered, which consists in studying the mutual transformation of the buoyancy frequency, shear flow, as well as the kinetic and potential turbulence energies determined at the initial time at different depths. It is shown that the kinetic energy of turbulence increases with time, and its maximum shifts to the maximum of the the horizontal shear flow. However, unlike the standard gradient scheme, in the beginning there is a mutual transformation of the kinetic and potential turbulence energies, after which they quickly reach a stationary equilibrium level (at large values of the Richardson numbers). A significant change in stratification, initially having a maximum at a certain depth, was also found in the process of establishing a stationary turbulence regime.

The work was financially supported by the Russian Foundation for Basic Research (projects № 18-05-00292, 18-35-00602).

References:

1. Ostrovsky, L.A., Troitskaya, Yu.I., The model of turbulent transport and the dynamics of turbulence in a stratified shear flow/ Izvestiya, Atmospheric and Oceanic Physics., 1987. v.3. pp. 1031–1040
Constraining hydrological impact simulations over Europe through weighting the climatic forcing
Authors: Greve Peter , Burek Peter , Wilcke Renate , Brunner Lukas , McSweeney Carol , Booth Ben , Lenderink Geert , Wada Yoshihide
Published: March 2020

Global hydrological models (GHMs) have become an established tool to simulate water resources on continental scales. To assess the future of water availability and various impacts related to hydrological extreme events, these models usually use sets of atmospheric variables (such as e.g., precipitation, humidity, temperature) obtained from (regional) climate model simulations as input data. The uncertainty associated with the climate projections is transferred onwards into the impact simulations and is usually accounted for through the use of large model ensembles. These ensembles thus enable assessments addressing the robustness of projected hydrological changes and impacts. Given recent efforts within the European Climate Prediction (EUCP) project to test existing and develop new techniques to constrain/weight climate model ensembles, we use here different methods to specify the large-scale meteorological input to an ensemble of regional climate models that provide the input data for a state-of-the-art GHM. The climate models are weighted/constrained based on the key large-scale climatic and meteorological drivers shaping the hydrological characteristics in different regions and large river basins across Europe. To assess the potential benefits of the different techniques, we compare simulation ensembles using unweighted input data obtained from the full ensemble of regional climate models against an ensemble based on constrained/weighted forcing data. Given the large uncertainties usually associated with hydrological impact simulations forced by the full range of available climate models, processing the ensemble output of GHMs based on uncertainty assessments of the underlying climate forcing could lead to more robust projections of water resources in general and hydrological extreme events in particular.
How does the meltwater flow? Retention and refreezing in firn on ice sheets and ice shelves
Authors: Mottram Ruth , Vandecrux Baptiste , Olesen Martin , Boberg Fredrik , Hansen Nicolaj , Langen Peter , Fausto Robert ,   RetMIP contributors
Published: March 2020

Mass loss from glacier surface melt is buffered by percolation and refreezing in the underlying snowpack, processes of particular importance in the percolation zone of the Greenland ice sheet and increasingly in Antarctica under a warming climate. Retention and refreezing is dependent on a number of micro-scale factors such as snow grain size, density and temperature that are heavily parameterized in models. Melt and snowfall in preceding seasons are also important in determining retention rates in the current season due to initialization of the snowpack .

In the retention model intercomparison project (RetMIP) we use a common atmospheric forcing from the HIRHAM5 regional climate model to drive participating  models, to study the effect of different internal parameterisations. We compare 9 different 1D models and four 2D models with each other and with observations from 4 key field sites. We show that initialisation of snowpack models is important but evolution of retention through time is strongly determined by melt rates.

Models that explicitly account for deep meltwater percolation tend to overestimate percolation depth and consequently firn temperature at the percolation and ice slab sites although they simulate accurately the recharge of the firn aquifer. Models using Darcy’s law and bucket scheme compare favourably to observations at the percolation site but only the Darcy models accurately simulate firn temperature and thus meltwater percolation at the ice slab site. We find that Eulerian models that transfer firn through fixed layers, diffuse over time the gradients in firn temperature and density. No model outperforms all others at our four test sites indicating that all models have potential for development.

A first look at Antarctic firn processes emphasises the importance of long spin-up times to initialise the snowpack and as the ice sheet surface evolves in the future parameterising the specific Antarctic retention process is likely to become more important.