bluuebunny/crossref_metadata_2025 huggingface dataset:
An integrated geophysical approach for structural behavior characterization of the Gravina bridge (Matera, Southern Italy)
Authors: Serlenga Vincenzo , Gallipoli Maria Rosaria , Tragni Nicola , Ditommaso Rocco , Stabile Tony Alfredo , Perrone Angela , Pietrapertosa Domenico , Carso Raffaele Franco
Published: March 2020

Civil infrastructures (i.e bridges, galleries ...) are crucial parts of the road asset and their possible degradation, with related consequences, may have great social, economical and safety impacts. On these grounds, the periodic monitoring of such infrastructures, from a static and dynamic point of view, is required for identifying possible changes in the structure properties, in order to prevent serious damages and disasters.

In this study we propose an integrated geophysical approach by using non-invasive and non-destructive seismic and electromagnetic techniques with standard and low-cost sensors. It has been implemented to understand the static and dynamic properties of the Gravina bridge and its interaction with foundation soils. Gravina Bridge is a bow-string bridge located few km far from Matera (Southern Italy) and developing for 144 m along a steel-concrete deck. First, the properties of the foundation soils were studied by carrying out three high-resolution geo-electrical tomographies, one bi-dimensional seismic array and two single-station seismic noise measurements. Then, the structural characteristics of the bridge were inferred through seismic and electromagnetic sensing. The former was performed by means of recordings by accelerometers and velocimeters. The accelerometers were installed in a continuous acquisition mode, along the deck and on the top of the arch. In that way, several local and regional earthquakes were recorded and detected. The velocimeters were deployed along different seismic array configurations for on-demand ambient noise recordings, in normal traffic conditions and during vibration tests. The latter were executed by using vehicles as dynamic sources.

The electromagnetic sensing was performed by using the Microwave Radar Interferometer: it was placed below the deck to measure the displacements of all the scenario illuminated by the antenna beam providing a continuous mapping of the static and dynamic displacements of the entire target.

The acquired dataset was analyzed both in frequency and time-frequency domain in order to characterize the stationary and non-stationary response of the monitored bridge in terms of fundamental frequencies of vibration, equivalent viscous damping factors and modal shapes. The consistency between the results retrieved by different geophysical techniques provides therefore an importan hint about the reliability of the described approach.
Monitoring rainfed cereals under different soils and rainfall pattern
Authors: Tarquis Ana Maria , Rivas-Tabares David , Martín-Sotoca Juan J. , Saa-Requejo Antonio
Published: March 2020

In most Mediterranean climate regions drought events are of great importance and their effects on rainfed crops are evident. Crop yields of rainfed cereal are highly dependent of the soil-plant-atmosphere system, especially referred to the weather conditions and soil properties. However, very few studies are found on the importance of both factors on crop condition.

Several plots were localized in the midlands of Eresma-Adaja watershed. Combining remote sensing data and agricultural survey work those with monocrop cereal sequences were identify. These plots were clustered based on which soil class were allocated based on a Self-Organizing Map and precipitation regimen elaborated in the area (Rivas-Tabares et al., 2019). Within this area, two contrasting soil properties sites were selected to assess plots with at least 20 years of rainfed monocropping sequences but under similar weather regime. This allows us to analyze the effect and relationships of soil type and rainfall with Normalized Difference Vegetation Index (NDVI) in time.

The NDVI average from both areas are statistically different in the growing season suggesting that soils and weather conditions are motivating the spectral variability of sites. The influence of soil texture and rainfall regimen related to NDVI values and interannual variability during the crop growth are discussed.

References

Rivas-Tabares, D., AM Tarquis, B Willaarts, Á De Miguel. 2019. An accurate evaluation of water availability in sub-arid Mediterranean watersheds through SWAT: Cega-Eresma-Adaja. Agricultural Water Management 212, 211-225.

 

ACKNOWLEDGEMENTS

Finding for this work was partially provided by Boosting agricultural Insurance based 465 on Earth Observation data - BEACON project under agreement Nº 821964, funded under H2020_EU, DT-SPACE-01-EO-2018-2020. The authors also acknowledge support from Project No. PGC2018-093854-B-I00 of the Spanish Ministerio de Ciencia Innovación y Universidades of Spain. The data provided by ITACyL and AEMET is greatly appreciated.
Total and methylmercury concentrations in Canadian alpine proglacial freshwater rivers (Banff and Jasper National Parks)
Authors: Serbu Jessica A. , St.Louis Vincent L. , Enns Sydney J. A.
Published: March 2020

Anthropogenic activities have resulted in increased mercury (Hg) emissions, and the deposition of inorganic and methyl Hg to watersheds, including those that are glaciated. Alpine glaciers are melting at unprecedented rates due to climate change, with glacier-fed rivers potentially transporting contaminants such as mercury historically archived in glacial ice to downstream proglacial environments. Hg in glacial rivers can also be derived from natural sources such as the erosion of subglacial and proglacial geologic material as glaciers melt and retreat. Furthermore, as inorganic Hg moves downstream, methylation can occur in regions of the watershed that contain wetlands, for example, transforming into it into toxic methyl Hg (MeHg) that can biomagnify in the watershed’s food web.

We conducted detailed monthly water quality surveys along three major glacial river transects (the Athabasca, North Saskatchewan, and Bow) in the Canadian Rocky Mountains (Banff and Jasper National Parks, Alberta), that included sampling for total and dissolved concentrations of total Hg (THg; all forms of Hg in a sample) and MeHg up to 100 km downstream of glacial termini. The resultant inter-seasonal data, spanning from May to December in this mid-latitude region, will be used to assess the amount of Hg originating from glacial melt in these systems and how it is transformed as it moves downstream. We will also examine contributions of Hg from the erosion of subglacial and proglacial bedrock material. Preliminary results show that THg and MeHg concentrations are very low in these rivers, consistently measuring at less that 3 ng/L. Additionally, as one moves downstream a larger proportion of THg is in the dissolved fraction. MeHg always measured around or below our laboratory’s detection limit (0.01 ng/L) regardless of the sampling location on our river transects.

The presence of contaminants such as Hg can have negative impacts on freshwater quality, organisms within the watershed, and downstream human populations. Quantifying the amount and speciation of Hg in the headwaters of three primary watersheds in Canada could have important implications for future research and the ongoing challenge of properly planning for drastic climate change effects in glaciated alpine regions despite concentrations of THg and MeHg being so low. 
Landslides triggered by 2019 extreme rainfall and flood events in Iran: Results from satellite remote sensing and field survey
Authors: Motagh Mahdi , Roessner Sigrid , Akbari Bahman , Behling Robert , Stefanova Vassileva Magdalena , Haghshenas-Haghighi Mahmud , Ulrich-Wetzel Hans
Published: March 2020

Between mid-March and the beginning of April 2019, extremely high precipitation affected the whole Iran, leading to widespread flash flooding and landslides. Approximately 10 million people were affected, among them 2 million were in humanitarian needs. The event caused 78 fatalities, more than 1000 injuries and widespread damage in 25 out of the 31 provinces.

In this work, we use both high resolution – spatial and temporal – optical and radar satellite remote sensing to characterize spatiotemporal pattern of landslide occurrence related to the main hydro-meteorological triggering events in Golestan province, North Iran. Large-area landslide detection has been performed in a semi-automated way using time series of optical Planet Scope and Sentinel-2A/B data. The obtained satellite remote sensing based results were evaluated by field surveys conducted in September 2019 in cooperation between the GFZ Potsdam and the Forest, Range and Watershed Management Organization of Iran (FRWM) being responsible for landslide hazard and risk assessment as well as the design and implementation of mitigation measures.

Moreover, we report on our deformation monitoring using Sentinel-1/B based differential interferometric synthetic aperture radar (DInSAR) on hot-spots areas to investigate whether any of the catastrophic landslides that happened in spring of 2019 have shown precursory signs in form of preparatory deformation. In particular, we present our detailed investigation for Hossein Abad Kalpush landslide, located at the border between Golestan and Semnan provinces. In April 2019, this slide slipped at an unprecedented scale, causing total destruction of one part of the village nearby with complete destruction of 250 houses. Using an integrated approach exploring satellite imagery, in-situ measurements and field survey, we perform detailed time-series analysis of the evolution of Hossein Abad Kalpush landslide and examine the role of meteorological and anthropogenic influencing factors in controlling the behaviour of this landslide.
Co-location of the downdip end of seismic locking and the continental shelf break
Authors: Malatesta Luca C. , Bruhat Lucile , Finnegan Noah J. , Olive Jean-Arthur L.
Published: March 2020

Along subduction margins, the morphology of the near shore domain records the combined action of erosion from ocean waves and permanent tectonic deformation from the convergence of plates. We observe that at subduction margins around the globe, the edge of continental shelves tends to be located above the downdip end of seismic coupling on the megathrust (locking depth). Coastlines lie farther landward at variable distances. This observation stems from a compilation of well-resolved coseismic and interseismic  coupling datasets. The permanent interseismic uplift component of the total tectonic deformation can explain the localization of the shelf break. It contributes a short wave-length gradient in vertical deformation on top of the structural and isostatic deformation of the margin. This places a hinge line between seaward subsidence and landward uplift above the locking depth. Landward of the hinge line, rocks are uplifted in the domain of wave-base erosion and a shelf is maintained by the competition of rock uplift and wave erosion. Wave erosion then sets the coastline back from the tectonically meaningful shelf break. We combine a wave erosion model with an elastic deformation model to show how the locking depth pins the location of the shelf break. In areas where the shelf is wide, onshore geodetic constraints on seismic coupling is limited and could be advantageously complemented by considering the location of the shelf break. Subduction margin morphology integrates hundreds of seismic cycles and could inform seismic coupling stability through time.
From Magma Ocean turbulent convection to lithosphere formation and mantle convection: insights from laboratory experiments
Authors: Davaille Anne , Massol Helene
Published: March 2020

A clear understanding of the transition from a liquid magma ocean (MO) to a convective solid mantle is still lacking. Part of the problem is that there is still no clear view of all the physical phenomena at play during this crucial stage. As the MO cools down, the formation of a solid and therefore very viscous lithosphere at its surface has often been considered to trigger a new pattern of motion where convection occurs below the lithosphere which remains stagnant. However, when the liquid thermal boundary layer at the top of the MO cools down, it first becomes a mushy lithosphere through which melt and exsolved gas bubbles can still percolate to the surface. Using laboratory experiments of thermal convection in colloidal suspensions, we study the formation of this mushy lithosphere and its different regimes of deformation and coupling to mantle convection. We observe that deformation of the lithosphere can include « heat pipe » formation at high heat, melt and volatile flux. On the other hand, rapid thermal contraction of the lithosphere can cause buckling, leading to subduction. Transition from MO to solid-state convection could involve both processes in succession , or in competition, depending on the temperature and volatiles conditions. 
A Cloud-based Science Gateway for Enabling Science as a Service to Facilitate Open Science and Reproducible Research
Authors: Ramamurthy Mohan
Published: March 2020

The geoscience disciplines are either gathering or generating data in ever-increasing volumes. To ensure that the science community and society reap the utmost benefits in research and societal applications from such rich and diverse data resources, there is a growing interest in broad-scale, open data sharing to foster myriad scientific endeavors. However, open access to data is not sufficient; research outputs must be reusable and reproducible to accelerate scientific discovery and catalyze innovation.

As part of its mission, Unidata, a geoscience cyberinfrastructure facility, has been developing and deploying data infrastructure and data-proximate scientific workflows and analysis tools using cloud computing technologies for accessing, analyzing, and visualizing geoscience data.

Specifically, Unidata has developed techniques that combine robust access to well-documented datasets with easy-to-use tools, using workflow technologies. In addition to fostering the adoption of technologies like pre-configured virtual machines through Docker containers and Jupyter notebooks, other computational and analytic methods are enabled via “Software as a Service” and “Data as a Service” techniques with the deployment of the Cloud IDV, AWIPS Servers, and the THREDDS Data Server in the cloud. The collective impact of these services and tools is to enable scientists to use the Unidata Science Gateway capabilities to not only conduct their research but also share and collaborate with other researchers and advance the intertwined goals of Reproducibility of Science and Open Science, and in the process, truly enabling “Science as a Service”.

Unidata has implemented the aforementioned services on the Unidata Science Gateway ((http://science-gateway.unidata.ucar.edu), which is hosted on the Jetstream cloud, a cloud-computing facility that is funded by the U. S. National Science Foundation. The aim is to give geoscientists an ecosystem that includes data, tools, models, workflows, and workspaces for collaboration and sharing of resources.

In this presentation, we will discuss our work to date in developing the Unidata Science Gateway and the hosted services therein, as well as our future directions toward increasing expectations from funders and scientific communities that they will be Open and FAIR (Findable, Accessible, Interoperable, Reusable). In particular, we will discuss how Unidata is advancing data and software transparency, open science, and reproducible research. We will share our experiences in how the geoscience and information science communities are using the data, tools and services provided through the Unidata Science Gateway to advance research and education in the geosciences.
Field observations of rapid midwinter recharge in a seasonally frozen bedrock aquifer
Authors: Wright Stephanie , Novakowski Kent
Published: March 2020

Under conditions of a changing climate winters are predicated to be warmer and wetter in the northern hemisphere. As a result, midwinter melts and rain on snow (ROS) events have the potential to contribute to groundwater recharge. An understanding of the impacts of repeated freeze-thaw and ROS on groundwater recharge is critical for predicting and managing future groundwater resources in seasonally frozen environments. In particular, fractured rock aquifers have received little attention regarding these processes. To explore the impacts of midwinter melts and ROS on bedrock recharge, a granitic outcrop has been heavily instrumented in Eastern Ontario, Canada over the 2019-2020 winter season. The low-lying outcrop is approximately 10 m X 8 m and the water table resides in the bedrock approximately 3 m below ground surface. Two wells have been drilled to 15 m and 30 m depths. The first well is open and the second has two isolated intervals with pressure transducers and temperature sensors installed in both wells. Three temperature probes have been drilled into the rock outcrop with two installed just beneath the soil to explore if heat transferred from exposed warming rock could melt adjacent frozen soil. Two soil moisture and temperature profiles (5 measurements each) have been installed in the adjacent soil and extend from the surface to the soil-bedrock contact. Finally, a weather station has been installed that measures precipitation, snow depth, air temperature, relative humidity, solar radiation and wind speed. The instrumented area allows for detailed measurements of atmosphere-subsurface interaction that can be used for coupled snowpack and subsurface flow modelling. Preliminary field observations indicate that rapid recharge in the bedrock can take place despite frozen conditions. This is evidenced by sharp drops in groundwater temperature accompanied by rises in water level in response to snowmelt or ROS events. The soil moisture and temperature profiles indicate that shallow (20 cm) soil remains frozen, limiting infiltration from above. However, runoff from the outcrop can flow along the soil-rock contact allowing for infiltration and recharge to occur beneath the frozen layer. These results suggest that areas of exposed rock can be localized hotspots for groundwater recharge when midwinter warming or ROS occurs. This may result in increased recharge to bedrock aquifers during winter months under future climate change scenarios.
The role of changing Southern Ocean circulation for the uptake and storage of CFC-12, anthropogenic CO2 and oxygen
Authors: Patara Lavinia , Rieck Jan Klaus , Tanhua Toste , Kriest Iris , Boening Claus
Published: March 2020

Recent studies highlighted an increase in the Southern Ocean ventilation since several decades and, at the same time, pronounced decadal fluctuations in its carbon sink. The role of changing ventilation for the anthropogenic CO2 uptake (and thus for the overall Southern Ocean carbon sink) and for oxygen concentrations of mode and intermediate waters (with possible impacts on low-oxygen regions downstream) are still poorly understood. The aim of this study is to assess the role of changing Southern Ocean ventilation for the uptake and storage of atmospheric gases such as CFC-12, CO2 and oxygen. A related question is whether CFC-12 can be used as a proxy of anthropogenic CO2 in the Southern Ocean, since CO2 equilibrates significantly more slowly in seawater than CFC-12 and, while the solubility of CFC-12 increases with decreasing temperature and salinity, the solubility of anthropogenic CO2 decreases. We developed a suite of global configurations based on the NEMO-LIM2 ocean sea ice model including the passive tracer CFC-12 and the biogeochemical model MOPS. The suite includes ORCA05 (1/2° resolution), ORCA025 (1/4° resolution) and ORION10 (featuring a 1/10° nest between 68°S and 30°S). Hindcast and sensitivity experiments performed with ORCA025 under the JRA-55-do atmospheric forcing are used to unravel the role of changing wind and buoyancy forcing on the gas uptake and storage. First results highlight that anthropogenic CO2 is taken up in lighter density classes than CFC-12, meaning that increased ventilation of lighter mode waters would be particularly effective in taking up anthropogenic CO2. This effect is more pronounced in the higher-resolution model ORION10, indicating that mesoscale eddies inject anthropogenic CO2 in lighter waters than lower-resolution models.
Robust data worth analysis with surrogate models in groundwater
Authors: Gosses Moritz , Wöhling Thomas
Published: March 2020

Physically-based groundwater models allow highly detailed spatial resolution, parameterization and process representation, among other advantages. Unfortunately, their size and complexity make many model applications computationally demanding. This is especially problematic for uncertainty and data worth analysis methods, which often require many model runs.

To alleviate the problem of high computational demand for the application of groundwater models for data worth analysis, we combine two different solutions:

a) the use of surrogate models as faster alternatives to a complex model, and

b) a robust data worth analysis method that is based on linear predictive uncertainty estimation, coupled with highly efficient null-space Monte Carlo techniques.

We compare the performance of a complex benchmark model of a real-world aquifer in New Zealand to two different surrogate models: a spatially and parametrically simplified version of the complex model, and a projection-based surrogate model created with proper orthogonal decomposition (POD). We generate predictive uncertainty estimates with all three models using linearization techniques implemented in the PEST Toolbox (Doherty 2016) and calculate the worth of existing, “future” and “parametric” data in relation to predictive uncertainty. To somewhat account for non-uniqueness of the model parameters, we use null-space Monte Carlo methods (Doherty 2016) to efficiently generate a multitude of calibrated model parameter sets. These are used to compute the variability of the data worth estimates generated by the three models.

Comparison between the results of the complex benchmark model and the two surrogates show good agreement for both surrogates in estimating the worth of the existing data sets for various model predictions. The simplified surrogate model shows difficulties in estimating worth of “future” data and is unable to reproduce “parametric” data worth due to its simplification in parameter representation. The POD model was able to successfully reproduce both “future” and “parametric” data worth for different predictions. Many of its data worth estimates exhibit a high variance, though, demonstrating the need of robust data worth methods as presented here which (to some degree) can account for parameter non-uniqueness.

 

Literature:

Doherty, J., 2016. PEST: Model-Independent Parameter Estimation - User Manual. Watermark Numerical Computing, 6th Edition.
Integrated, operational water availability estimates for the conterminous United States: transdisciplinary data and modeling successes and challenges
Authors: Driscoll Jessica M. , Farmer William H.
Published: March 2020

The U.S. Geological Survey, through the National Water Census, has produced a near real-time, operational concept map of water availability for the conterminous United States. Currently, this map aggregates “natural” landscape-dimension storage volumes (e.g. soil moisture, snowpack, and surface depression storage) and relates these values to historic averages for a given spatial unit for the given time of year. The purpose of this operational concept map is to improve communication of current water availability to the general public using the best available knowledge and technology. Current operational model deployment is an application of nationally-consistent methods; however, the degree to which regionalization and local knowledge might be applied and interwoven into the national product are current topics of exploration. In addition, future development for this model and visualization process will include adding water quality and water use as variables that contribute to the overall availability of water. Adding these transdisciplinary components to the existing physical model is not straightforward; the differences in model structure and data types needed for specific disciplines will need to be overcome to present a truly integrated water availability estimate that can provide useful information for the public as well as the technical research community. In this presentation, we explore the successes and challenges of the existing operational model used for the National Water Census, including transdisciplinary model integration, calibration, and uncertainty, with the goal of improving communication of water availability.
Seafloor pockmarks on the Chatham Rise, New Zealand: Possible causes and links to glacial cycles.
Authors: Pecher Ingo , Davy Bryan , Hillman Jess , Stott Lowell , Coffin Richard , Prestage Anna , Rose Paula , Bialas Joerg
Published: March 2020

An area of the seafloor of >50,000 km2 on the Chatham Rise and Bounty Trough east of New Zealand’s South Island is covered by seafloor depressions.  Distribution and type of these depressions seem to be bathymetrically controlled, with smaller depressions occurring between ~500-700 m water depth and larger ones in water depths of >800 m.  Formation of these features is enigmatic.  The smaller features display typical features of pockmarks caused by sudden escape of fluids and gas.  Echosounder and seismic data furthermore reveal wide-spread buried pockmarks that appear to have been formed repeatedly near glacial-stage maxima.  Some of the buried pockmarks appear to be stacked, often at a slight offset, underlain by positive-polarity reflections, and aligned with structures that promote fluid escape.  These patterns are compatible with repeated release of fluids from deep sources and precipitation of authigenic material.  Some of the larger seafloor depressions appear to involve interaction with the Southland Current.  These depressions have been interpreted as contouritic mounds although alternative hypotheses have been proposed and they may be linked to deeply rooted fluid migration.

Pronounced Δ14C anomalies during the last glacial termination, around the time of formation of the most recent pockmarks, indicate release of significant amounts of geologic carbon.  The pockmark fields coincide with the extent of the flat-subducted Hikurangi Plateau.  We hypothesize formation of the pockmarks is linked to repeated release of CO2 that originates from carbonates on top of the Hikurangi Plateau.  We will discuss this hypothesis, open questions in particular related to the “valve” mechanism controlling repeated release and pockmark formation, as well as alternative mechanisms for possible formation of seafloor depressions in the study area.
Protein yield and extractability of flood-tolerant perennial grasses cultivated on a riparian fen, affected by harvest and fertilisation frequency
Authors: Kalla Claudia , Stødkilde Lene , Jørgensen Uffe , Lærke Poul Erik
Published: March 2020

Paludiculture, defined as agriculture on wet or rewetted peatlands has been proposed as a mitigation strategy to reverse unsustainable environmental impacts such as land subsidence, nutrient release to surface water and greenhouse gas emissions from traditional agriculture on drained peatland. In particular, the production of biomass feedstock from flood-tolerant perennial grasses for green biorefining to protein and other value-added products may be a viable economic and environmentally sustainable option for temperate peatlands. However, optimal quality characteristics of the biomass for protein extraction have yet to be defined.

In 2018, field plots cultivated with different flood-tolerant perennial grasses were established in an agricultural fen peatland in Denmark. Of these, a total of eight plots cultivated with reed canary grass (RCG) and tall fescue were each subdivided into six sub-plots with different management regarding harvest and fertilisation. Harvest frequencies ranged from one to five times in the period between mid-May to mid-October at intervals of 4-6 weeks. The sub-plots received fertilisation of 100 kg ha-1 of both N and K prior to each harvest. Protein extractability of the grasses was assessed by lab-scale biorefinery techniques using a screw press followed by precipitation of true protein in the resulting juice. This was compared with protein fractions classified by the Cornell Net Carbohydrate and Protein System (CNCPS).  The biorefinery extractable protein yields (fresh weight) ranged from 10 % to 25 % of the fresh mass input, dependent on treatment, with summer harvests having the lowest yield. Evaluation of the easily extractable crude protein (CP) CNCPS fractions B1 and B2 showed yields of between 61.8 – 110.7 g CP kg-1 DM.  Preliminary processing of data showed that the cumulative yields of extractable crude protein for the growing season seem highly affected by management.
Migration patterns of earthquake clusters
Authors: Fischer Tomáš , Hainzl Sebastian
Published: March 2020

Earthquake hypocenter migration is the most characteristic pattern which indicates aseismic processes triggering the observed seismicity. These processes can involve creep, fluid migration or similar. While interactions among earthquakes can also lead to some expansion of seismic clouds, these expansions are rather small and not comparable to migration patterns related to pore-pressure diffusion, slow slip events, or growing hydraulic fractures. Thus, identification and modeling of migration patterns, which has not been studied in detail, is important for the characterization of fault dynamics.

Advance of the triggering front is usually analyzed using distance-time plots that show the time dependence of the distance of individual events from the origin. If event order is used instead of time as the argument on the horizontal axis, event migration is analyzed in dependence on the seismic activity itself, which brings a new view to the running seismicity. We applied this approach to the relocated earthquake swarm catalogs from West Bohemia, California and Iceland and found a striking linear growth of the triggering front. This indicates that the advance of the front is likely to be driven by the rupture of individual earthquakes rather than by the running time. It also turned out that the growth velocity measured in meters per event increases with the magnitude of the data set.

Using the basic concepts of earthquake physics, we propose the relation of the growth velocity on earthquake magnitudes and compare it with measurements on the analyzed swarm catalogues. We show that the spreading velocity of the triggering front is closely related to source parameters, which gives hints to the understanding of the background mechanism.
Imaging the Earth’s magnetic environment in soft X-rays with SMILE
Authors: Branduardi-Raymont Graziella , Sembay Steve , Sun Tianran , Connor Hyunju , Samsonov Andrey
Published: March 2020

It is a relatively recent discovery that charge exchange soft X-ray emission is produced in the interaction of solar wind high charge ions with neutrals in the Earth’s exosphere; this has led to the realization that imaging this emission will provide us with a global and novel way to study solar-terrestrial interactions.

In particular X-ray imaging will provide us with the means of establishing the location of the magnetopause and the morphology of the magnetospheric cusps. Variations of the magnetopause standoff distance indicate global magnetospheric compressions and expansions, both in response to solar wind variations and internal magnetospheric processes.

Soft X-ray imaging is one of the main objectives of SMILE (Solar wind Magnetosphere Ionosphere Link Explorer), a joint space mission by ESA and the Chinese Academy of Sciences, which is under development and is due for launch in 2023. This presentation will introduce the scientific aims of SMILE, show simulations of the expected images to be returned by SMILE’s Soft X-ray Imager for different solar wind conditions, and will discuss some of the techniques that will be applied in order to extract the positions of the Earth’s magnetic boundaries, such as the magnetopause standoff distance.
The timing of fjord formation and early glaciations in North and Northeast Greenland
Authors: Pedersen Vivi Kathrine , Krog Larsen Nicolaj , Lundbek Egholm David
Published: March 2020

The timing and extent of early glaciations in Greenland, and their co-evolution with the underlying landscape remain elusive. In this study, we explore the timing of fjord erosion in Northeast and North Greenland between Scoresby Sund (70°N) and Independence Fjord (82°N). By determining the timing of fjord formation, we can improve our understanding of the early history of the Greenland Ice Sheet in these regions.

We use the concept of geophysical relief to estimate fjord erosion and calculate the subsequent flexural isostatic response to erosional unloading. The timing of erosion and isostatic uplift is constrained by marine sediments of late Pliocene-early Pleistocene age that are now exposed on land between ~24 and 230 m a.s.l.

We find that the northern Independence Fjord system must have formed by glacial erosion at average rates of ~0.5-1 mm/yr since ~2.5 Ma, in order to explain the current elevation of the marine Kap København Formation by erosion-induced isostatic uplift. In contrast, fjord formation in the outer parts of southward Scoresby Sund commenced before the Pleistocene, most likely in late Miocene, and continued throughout the Pleistocene by fjord formation progressing inland. Our results suggest that the inception of the Greenland Ice Sheet began in the central parts of Northeast Greenland before the Pleistocene and spread to North Greenland only at the onset of the Pleistocene.  
Testing the distributed hydrological wflow_sbm concept across different geographical domains
Authors: Weerts Albrecht , van Verseveld Willem , Eilander Dirk , Boisgontier Helene , Haag Arjen , Hazenberg Pieter , Imhoff Ruben
Published: March 2020

Improving our understanding of hydrological processes beyond single catchments is important. Here we test wflow_sbm (simple bucket model) for modelling hydrology across different geographical areas (i.e. Europe, Africa).  Wflow_sbm is a conceptual bucket-style hydrological model based on simplified physical relationships. It uses kinematic wave surface and subsurface routing for lateral transport. The model setup and parameter estimation are fully automated based on global and regional data sources (like MERIT DEM, SoilsGrids, monthly MODIS LAI, global/regional land use) and includes anthropogenic influences like lakes and reservoirs and its management from HydroLAKES and GRanD databases. It makes use of scaling operators as applied in Multiscale Parameter Regionalization (MPR) to go from high resolution data sources to a ~1km2 or coarser resolution model.  

The model is tested at 1 km2 spatial and daily temporal resolution for different basins: Umealven (Sweden), Glomma (Norway), Mono river (Togo), the white Nile, Save River (Mozambique) and Incomati river using EOBS or CHIRPS rainfall and ERA5 derived temperature and potential evaporation forcing.  From these applications, it becomes apparent that the model can explain the measured discharge most of times reasonably well (KGE~0.4 and higher). The main factors controlling the performance are (quality of the) forcing, lateral hydraulic conductivity, rooting depth and reservoir/lake management.
20 years of mountain permafrost monitoring in the Swiss Alps: key results and major challenges
Authors: Noetzli Jeannette , Pellet Cécile
Published: March 2020

Permafrost is a widespread thermal subsurface phenomenon in polar and high mountain regions and was defined as an essential climatic variable (ECV) by the Global Climate Observing System (GCOS). The Swiss Permafrost Monitoring Network was started in the year 2000 as an unconsolidated network of sites from research projectsand as the first national long-term observation network for permafrost it is an early component of the Global Terrestrial Network for Permafrost (GTN-P). After 20 years of operation, development and evaluation, PERMOS holds the largest and most diverse collection of mountain permafrost data worldwide and has a role model regarding its structure and organization. PERMOS aims at the systematic long-term documentation of the state and changes of mountain permafrost in the Swiss Alps. The scientific monitoring strategy is now based on three observation elements: ground-surface and subsurface temperatures, changes in subsurface ice content, and permafrost creep velocities. These three elements complement each other in a landform-based approach to capture the influence of the topography as well as the surface and subsurface conditions of different landforms on the ground thermal regime. These influences are considered to be more relevant than regional climatic conditions in the small country.

Over the past 20 years, all observation elements indicate a clear warming trend of mountain permafrost in the Swiss Alps. Borehole temperatures generally increase at 10 and 20 m depth. This warming trend was intensified after 2009 and temporarily interrupted following winters with a thin and late snow cover, particularly winter 2016. Further, the trend is more pronounced at cold permafrost sites like rock glacier Murtèl-Corvatsch, where an increase of +0.5°C has been observed at 20 m over the past 30 years. For permafrost temperatures close to 0 °C, climate warming does not result in significant temperature increase but is masked by phase changes and latent heat effects. These result in significant changes in ice content, which can be registered by electrical resistivity tomography (ERT). Further, the warming trend of mountain permafrost in the Swiss Alps is corroborated by increasing creep rates of rock glaciers, which follow an exponential relationship with ground temperatures. In this contribution, we present and discuss the key results from two decades of mountain permafrost monitoring within the PERMOS network. In addition to the measurement data, we identified considerable challenges for long-term monitoring network of mountain permafrost based on experience collected over two decades. The acquisition of reliable data at a limited number of stations in extreme environments with difficult access requires robust strategies, standards and traceability for the entire data acquisition chain: installation > measurement > raw data > processing > archiving and, finally, reporting.
Hydraulic strategy drives Amazon forest modelled response to drought
Authors: Papastefanou Phillip , Zang Christian , Pugh Thomas , Liu Daijun , Lapola David , Fleischer Katrin , Grams Thorsten , Hickler Thomas , Rammig Anja
Published: March 2020

Plant hydraulics are crucial to understand impacts of droughts on single plants and whole forest ecosystems. The complex interplay of hydraulic mechanisms still poses challenges for vegetation modellers, regarding development and parameterization. Here, we apply a new hydraulic module developed for the dynamic global vegetation model LPJ-GUESS to the Amazon Basin. Special focus is given to the newly developed mortality process based on hydraulic-failure and to differences in hydraulic behaviour of plants.  The implemented hydraulic-failure process can explain observed mortality patterns at rainfall exclusion experiments in the Amazon. Modelled vegetation carbon is most sensitive to two of the hydraulic processes: The xylem vulnerability to water stress and the plant specific hydraulic behaviour, i.e. how plants regulate their water potential under drought stress. Applied to the whole Amazon Basin, our model shows a strong impact of the 2005 drought event across a wide margin of modelled species and parameters, which is in good agreement with empirical studies. We highlight the hydraulic behaviour of plants, for which little is known in the Amazon rainforest, and its relevance for ecosystem model development. Considering only one single plant functional type does not sufficiently capture the complex response of the Amazon rainforest to drought, hence future modelling studies should take the interaction and competition of different hydraulic strategies into account.
The role of ocean circulation in the propagation of rifts on ice shelves.
Authors: Poinelli Mattia , Larour Eric , Riva Riccardo
Published: March 2020

The break-up of large ice shelves and the associated loss of ice are thought to play a destabilizing role in the ice sheet dynamics. Although ice shelves are a substantial buttressing source in the stability of continental ice sheets, the propagation of large rifts eventually leads to the break-up of icebergs into the ocean. As consequence, this loss of ice would trigger further glacier acceleration and ice sheets retreat, destabilizing the ice cap. Retreat and collapse of ice sheets are also thought to be related to regional climate warming. Indeed, satellite observations suggest that a warming surrounding would induce the ice sheet to progressive thinning and weakening.

The prolongation of un-grounded ice into the ocean is often interrupted by the propagation of fractures that eventually separates large icebergs from the ice shelf. These fractures are called rifts and range from dimensions of 10 to 100 km. A recent example of such phenomena is the massive break-up of the Larsen C in July, 2017 which followed the disintegration of Larsen A in 1995 and the partial break-up of Larsen B in 2002. The tabular iceberg formed by Larsen C was limited by the propagation of a large rift that began in summer 2016, although the ice shelf had already been thinning since 1992.

Rift initiation and propagation are thought to be the result of glaciological and oceanographic sources that trigger ice to break. Nonetheless, exact mechanisms remain elusive. The on-going project focuses on ice-ocean interactions in ice shelves that accommodate rifts by using oceanographic models. The goal is to couple rift propagation and ocean circulation underneath ice cavities in order to infer how basal melting affects the development of rifts. The numerical framework is developed within the capabilities of the MITgcm. We aim to identify the sensitivity of propagation rate and opening rate of rifts to variations in the ocean circulation that have occurred during the separation of part of the ice shelf.

On a larger scale, we are interested in the role of rifting in the stability of Antarctic shelves. Therefore, we work toward a better understanding of which processes are involved in the triggering of rift propagation.
High resolution CO2 record of the great Plio-Pleistocene glaciations using boron isotopes
Authors: Brown Rachel , Chalk Thomas , Wilson Paul , Rohling Eelco , Foster Gavin
Published: March 2020

The intensification of Northern Hemisphere glaciation (iNHG) at 3.4-2.5 million years ago (Ma) represents the last great transition in Cenozoic climate state with the development of large scale ice sheets in the Northern Hemisphere that waxed and waned with changes in insolation. Declining atmospheric CO2 levels are widely suggested to have been the main cause of iNHG but the CO2 proxy record is too poorly resolved to provide an adequate test of this hypothesis. The boron isotope-pH proxy, in particular, has shown promise when it comes to accurately estimating past CO2 concentrations and is very good at reconstructing relative changes in CO2 on orbital timescales. Here we present a new orbitally resolved record of atmospheric CO2 (1 sample per 3 kyr) change from Integrated Ocean Drilling Program Site 999 (12.74˚N, -78.74 ˚E) spanning ~2.6–2.4 Ma based on the boron isotope (δ11B) composition of planktic foraminiferal calcite, Globingerinoides ruber (senso stricto, white).  We find that δ11B values of G. ruber show clear glacial-interglacial cycles with a magnitude that is similar to those of the Mid-Pleistocene at the same site and elsewhere.  This new high-resolution view of CO2 during the first large glacial events of the Pleistocene confirms the importance of CO2 in amplifying orbital forcing of climate and offers new insights into the mechanistic drivers of natural CO2 change. 
Establishing past firn accumulation records from ice caves of the European Alps
Authors: Racine Tanguy , Spötl Christoph , Reimer Paula
Published: March 2020

Mid-latitude, cave-hosted temperate ice is increasingly scrutinised for its palaeoclimatic potential. Findings of dendrochronologically dated wood trunks and radiometrically dated woody macrofossils demonstrate that underground ice accumulations records may locally span several millenia. The cave geometries conducive to underground firn accumulation were additionally shown to favour the preservation of a winter signal, making cave-hosted ice an attractive and complementary archive to existing and largely summer-biased proxy records. Proxy derivation from these ice accumulations first requires the establishment of firn accumulation/ablation chronologies from stratigraphic mapping and radiometric dating of organic inclusions. Decadal to centennial trends in accumulation/ablation recorded by the ice stratigraphy thus provide insight in past variations of solid precipitation .

Preliminary results from several well-dated ice caves of the Northern Calcareous Alps in Austria suggest local preservation of ice since ca. 3600-3300 BC. Inclusion-rich unconformities in the ice stratigraphy from these alpine caves mark short breaks in firn accumulation between 250 BC and 250 AD and longer hiatuses during Late Antiquity and the 8th and 9th century AD. The majority of dated ice sequences testify the onset of rapid ice accumulation from the 11th and 12th century AD onwards and build up throughout the 'Litte Ice Age'.
Global soil respiration: patterns, challenges and network opportunities
Authors: Vargas Rodrigo , Warner Daniel , Stell Emma , Bond-Lamberty Benjamin , Jian Jinshi
Published: March 2020

Soil respiration (Rs) is the soil‐to‐atmosphere CO2 efflux produced by microbes and plant roots and is a critical component for the global carbon budget. We present state-of-the-art approaches to estimate global soil respiration at 1 km spatial resolution using the global Soil Respiration Database (GSRD) and machine learning techniques. Patterns of Rs are evident at the global scale and we report an annual estimate of 87.9 Pg C/year with an associated global uncertainty of 18.6 (mean absolute error) and 40.4 (root mean square error) Pg C/year. Global heterotrophic respiration (Rh), the microbial decomposition of soil organic matter, could be derived from empirical relationships with Rs with a global estimate of 49.7 Pg C/year. We discuss how these global estimates and patterns are influenced by adding new measurements as we compared the GSRD version 3 with version 4. This comparison raises challenges about how adding new information, within a multivariate space, influence model uncertainty and regional-to-global estimates. Finally, we discuss future approaches to estimate global Rs, network opportunities for expanding the GSRD, and where new measurements are needed across the world.