bluuebunny/crossref_metadata_2025 huggingface dataset:
Radio Emissions from Electrical Activity in Martian Dust Storms
Authors: Majid Walid
Published: March 2020

Dust storms on Mars are predicted to be capable of producing electrostatic fields and discharges, even larger than those in dust storms on Earth.  There are three key elements in the characterization of Martian electrostatic discharges: dependence on Martian environmental conditions, event rate, and the strength of the generated electric fields.  The detection and characterization of electric activity in Martian dust storms has important implications for habitability, and preparations for human exploration of the red planet. Furthermore, electrostatic discharges may be linked to local chemistry and plays an important role in the predicted global electrical circuit.

 

Because of the continuous Mars telecommunication needs of NASA’s Mars-based assets, the Deep Space Network (DSN) is the only facility in the world that combines long term, high cadence, observing opportunities with large sensitive telescopes, making it a unique asset worldwide in searching for and characterizing electrostatic activity from large scale convective dust storms at Mars. We will describe a program at NASA’s Madrid Deep Space Communication Complex that has been carrying out a long-term monitoring campaign to search for and characterize the entire Mars hemisphere for powerful discharges during routine tracking of spacecraft at Mars on an entirely non-interfering basis. The ground-based detections will also have important implications for the design of a future instrument that could make similar in-situ measurements from orbit or from the surface of Mars, with far greater sensitivity and duty cycle, opening up a new window in our understanding of the Martian environment.
On the origins of an explicit IMF By dependence on solar wind - magnetosphere coupling
Authors: Reistad Jone Peter , Ohma Anders , Laundal Karl Magnus , Moretto Therese , Milan Steve , Østgaard Nikolai
Published: March 2020

Presently, all empirical coupling functions quantifying the solar wind - magnetosphere energy- or magnetic flux conversion, assume that the coupling is independent of the sign of the dawn-dusk component (By) of the Interplanetary Magnetic Field (IMF). In this paper we present observations strongly suggesting an explicit IMF By effect on the solar wind - magnetosphere coupling. When the Earth's dipole is tilted in the direction corresponding to northern winter, positive IMF By is found to on average lead to a larger polar cap than when IMF By is negative during otherwise similar conditions. This explicit IMF By effect is found to reverse when the Earth's dipole is inclined in the opposite direction (northern summer), and is consistently observed from both hemispheres using the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) to infer the size of the region 1/2 current system. Two interpretations are presented: 1) The dayside reconnection rate is affected by the combination of dipole tilt and IMF By sign in a manner explaining the observations 2) The combination of dipole tilt and IMF By sign affect the global conditions for maintaining a given nightside reconnection rate. The observations as well as idealized magnetohydrodynamic (MHD) model runs are analyzed and discussed in light of the two different interpretations in order to enhance our understanding of this explicit IMF By effect.
Geomorphic feedbacks on the moraine record
Authors: Anderson Leif , Scherler Dirk
Published: March 2020

Glacial moraines represent one of the most spatially diverse climate archives on earth. Moraine dating and numerical modeling are used to effectively reconstruct past climate from mountain ranges at the global scale. But because moraines are often located downvalley from steep mountain headwalls, it is possible that debris-covered glaciers emplaced many moraines preserved in the landscape today.

Before we can understand the effect of debris cover on the moraine recored we need to understand how debris modulates glacier response to climate change. To help address this need, we developed a numerical model that links feedbacks between mountain glaciers, climate change, hillslope erosion, and landscape evolution. Our model uses parameters meant to represent glaciers in the Khumbu region of Nepal, though the model physics are relevant for mountain glaciers elsewhere.

We compare simulated debris-covered and debris-free glaciers and their length evolution. We explore the effect of climate-dependent hillslope erosion. We also allow temperature change to control frost cracking and permafrost in the headwall above simulated glaciers. Including these effects holds special implications for glacial evolution during deglaciation and the long-term evolution of mountain landscapes.

Because debris cover suppresses melt, debris-covered glaciers can advance independent of climate change. When debris cover is present during cold periods, moraine emplacement can lag debris-free glacier moraine emplacement by hundreds of years. We develop a suite of tools to help determine whether individual moraines were formed by debris-covered glaciers. Our analyses also point to how we might interpret moraine ages and estimate past climate states from debris-perturbed settings.
Preliminary GHG balances of different drained and rewetted peatland ecosystems in North-eastern Germany
Authors: Köhn Daniel , Günther Anke , Jurasinski Gerald
Published: March 2020

Globally, peatlands store an immense amount of carbon and thus are of large importance for the global climate. Therefore, it is also of uttermost importance to understand the functioning of this carbon sink with regards to anthropogenic influences such as drainage, agricultural use and subsequent rewetting.

In the federal state of Mecklenburg-Western Pomerania in north-western Germany peatlands cover 13% of the total land area. A large proportion of these peatlands have been drained and an estimated 27% of all GHG Emissions of the state originate from drained peatlands. Rewetting of peatlands holds a large potential for the reduction of CO2 emissions thus becoming more and more important in tackling climate change.

In the WETSCAPES project, we aim at understanding the processes of matter turnover in differently managed peatland ecosystems. Here we present preliminary full GHG balances of the first two years of measurements. Results include the balances of coastal flooding fens, percolation fens, and alder forests, of which there is a drained and rewetted one for each peatland ecosystem. The coastal flooding fen was rewetted in 1996, the percolation fen in 1998 and the alder forest in 2003. Fluxes of CO2, CH4, and N2O were measured on these six different sites using the closed chamber method. Additionally, stem fluxes and ditch fluxes were included in the balances where applicable.

Preliminary results show lower CO2 emissions in the rewetted compared to the drained sites; however, this depends strongly on the peatland type. Especially the coastal fens differed only slightly in their CO2 emissions and at the same time showed very high overall CO2 emissions.

Our results show strong variation in GHG emissions of drained and rewetted central European fens in two years with extreme weather, i.e. drought, conditions that are predicted to become more common with increasing global warming. Methane emissions of the rewetted sites were low with only temporary peaks in summer, which again suggests rewetting as the best solution to reduce the climate impact of drained peatlands.
Measured Elevation of Lightning and Aurora in the Jovian Atmosphere
Authors: Benn Mathias , Jørgensen John L. , Denver Troelz , Jørgensen Peter S. , Herceg Matija , Connerney John E. P.
Published: March 2020

As part of the Juno MAG investigation, each magnetometer features dedicated star trackers providing accurate bias free attitude information continuously throughout the mission. These optical sensors are optimized for low-light scenarios, which enables detection of stars and objects as faint as 7-8Mv. The Juno mission features a highly elliptical polar orbit with a period of ~53 days, with periapsis as close as 3.300km above the cloud tops. In combination with the 13° off pointing of the star tracker cameras from the Juno spin axis in anti-sun direction, the Jovian night side high latitude regions regularly enters the field of regard of these star trackers. This geometry facilitates imaging low light phenomenas as lightning and aurora at a large slanted angle in the upper parts of Jupiter’s atmosphere. The large slant angle enables estimation of the vertical structure, by combining the detections with accurate attitude and spacecraft position information. We present up-to-date images of detected lightning events, visible wavelength aurora and the measured vertical structure, and discuss implications of these measurements for the Jovian atmosphere at the resulting altitudes
European drought during the last two millennia from reconstructions and model simulations
Authors: González-Rouco Fidel , López-Cayuela María Angeles , Navarro Jorge , García-Bustamante Elena , García-Cantero Nuria , Melo-Aguilar Camilo , Steinert Norman
Published: March 2020

The spatial and temporal variability of droughts in the Euro-Mediterranean area during the last two millennia has been analyzed by comparing the Old World Drought Atlas (OWDA) dentrochronological based reconstruction and 13 simulations including a complete set of natural and anthropogenic forcings from the Community Earth System Model- Last Millennium Ensemble (CESM-LME). The OWDA represents scPDSI estimates, whereas for the CESM-LME soil moisture is used. A clustering into regions of objectively different behavior is achieved through rotation of principal components and the resulting regionalizations of the OWDA and the CESM-LME are compared.

The resulting regions from the reconstructions and model are overall consistent. Some regions are coincident in both and in some cases model regions are a combination of the reconstructed ones. The resulting classification is also robust across the model ensemble, although It is found that the definition of some hydroclimatic regions shows some sensitivity to internal variability.

The temporal variability of drought within each region is analyzed. Differences are found in the level of low frequency variability among regions with implications for the probability of having long intense droughts in different areas. Megadroughts have been found to exist both in the reconstructions and in the simulations and their occurrence suggest rather internal variability dependances rather than responses to external forcing.
High temporal resolution measurements of CO2, CH4 and N2O in a Norwegian mire ecosystem using automated light-dark chambers
Authors: Avila Linsey , Steenberg Larsen Klaus , Ibrom Andreas , Pirk Norbert , Larsen Poul
Published: March 2020

Regeneration of natural hydrology in previously drained peatlands is becoming a widespread practice in nature restoration projects around the world. The drained peatlands are well known for their high emissions of CO2 caused by increased microbial decomposition rates in these very organic soils when suddenly exposed to higher levels of oxygen availability. Restoring natural water levels reduces again the decomposition rates and CO2 emissions. It remains uncertain, however, how rates of the much stronger greenhouse gases, CH4 and N2O, respond to the restored water table and these fluxes can potentially offset the GHG balance of rewetting peatlands.

 

In a new project in Norway (close to Trysil, Innlandet), we installed five ECO2flux automated chambers and one eddy flux tower in each of two areas of drained peatlands.  The automatic chambers were placed with different distances to the ditches reflecting variation in water table with greatest water level variability at the edges of the ditches. After two years, the ditches will be filled and the natural water table will be regenerated in one of the areas in order to follow the differences in the fluxes of CO2, CH4 and N2O upon rewetting.

 

We here present an analysis of the first year’s data from the ECO2flux chambers including the total greenhouse gas budget for the period measured. The fluxes of CO2 showed only little spatial heterogeneity whereas we observed a significant spatial pattern of higher fluxes of CH4 in plots where the water table was closer to the surface. The driest plots, i.e. the edges of the drain ditches, showed also the lowest emissions of CH4. The trend was similar in the two areas. This is an indicating that planned rewetting after two years of the project may lead to enhanced production and emission of CH4 in the area. So far, we observed no N2O emissions above the detection limit of the system indicating that CO2 and CH4 are the major components of the GHG budget.
Emerging heat extremes, adaptation and the speed of socio-economic development
Authors: Schleussner Carl-Friedrich , Vogel Martha M. , Pfleiderer Peter , Andrijevic Marina , Otto Friederike E. , Seneviratne Sonia I.
Published: March 2020

Heat extremes are among the most pertinent extreme weather hazards. At the same time, adaptation to the impacts of extreme heat can be very effective. The ability of societies to effectively adapt to climate change hazards such as extreme heat, however, critically depends on their level of socio-economic development. Examining the risks posed by future heat extremes to human societies requires to link socio-economic development trajectories with emerging heat extremes. Such an integrated assessment can also provide insights into whether or not it is indeed plausible for societies to “outgrow” climate change by increasing adaptive capacity faster than climate impacts emerge -  a narrative that underlies many policy decisions that prioritize economic development over climate action still today.

 

Here we provide such an integrated assessment by combining a novel approach to project the continuous emergence of heat extremes over the 21st century under different concentration pathways and the pace of socio-economic development under the shared socio-economic pathways accounting for continuous autonomous adaptation. We find that even under the most optimistic scenarios of future development, countries may not be able to outpace unmitigated climate change. Only Paris-Agreement compatible concentration pathways allow for human development to keep up with or even outpace the emerging climate change signal in vulnerable countries in the near future. A similar picture emerges when comparing heat day emergence with future evolution of governance as a proxy for adaptive capacity. Our findings underscore the critical importance of achieving the Paris Agreement goals to enable climate-resilient, sustainable development.
Multiple constraints and objectives should inform the negotiated filling of the Grand Ethiopian Renaissance Dam
Authors: Basheer Mohammed , Harou Julien , Wheeler Kevin , Elagib Nadir , Zagona Edith , Abdo Gamal , Etichia Mikiyas
Published: March 2020

This study analyzes the implications of a variety of filling approaches of the Grand Ethiopian Renaissance Dam (GERD) for the outlet management and dam engineering. A daily water balance model of the GERD is developed and used to investigate the ability of the GERD outlets to enable six reservoir filling scenarios. Results show that the turbines’ outlets, the bottom outlets, and the spillways would sufficiently provide downstream releases during the steady-state operation of the GERD. The river diversion outlets of the GERD are necessary to enable agreements on reservoir filling and the Ethiopian turbine phasing-in plan. The use of the river diversion outlets requires compliance with dam engineering constraints such as steel lining, head limit, and maximum flow speed. We propose a multi-objective optimization framework for reservoir filling whereby dam engineering constraints are considered in the negotiations on the initial filling of multi-year storage reservoirs.
Microfluidic device for continuous-flow analysis of organics in oldest ice
Authors: FIlippi Daniele , Giorio Chiara
Published: March 2020

The Beyond EPICA Oldest Ice (BEOI) project will drill an ice core dating back to 1.5 million-years (1.5 Myr) ago. This ice core is of particular interest to the scientific community as it will be the only one covering the climate history of the Mid Pleistocene Transition, when glacial-interglacial cycles changed from a 40 Kyr to 100 Kyr cyclicity, and for which causes are not well understood currently. Obtaining useful climatic information beyond 800 Kyr represents an analytical challenge due to the fact that the deepest section of the ice core is very compact and the amount of sample available is very low.

Current analytical methods for the determination of organics in ice are characterized by a large number of steps that requires large amounts of sample for a single analysis. This results in the loss of the high time resolution desired from ice cores which is particularly problematic for deeper (i.e. older) records where the ice is more compact.

This work aims at combining the growing field of microfluidics with improvements to conventional mass spectrometry to allow for continuous analysis of organics in ice cores, melted in continuous on a melting-head. In fact, microfluidic is a powerful technology in which, only a small amount of liquid (10-9-10-18 liters) is manipulated and controlled with an extremely high precision. The method invokes a three-step process: (1) the melted ice core sample is sent to a nebulizer to produce aerosol, then (2) the aerosol is dried to remove water content and concentrate the sample, and (3) the aerosol is sent to a mass spectrometer for continuous analysis through a modified electrospray ionization (ESI) probe.

This novel system, once operational, can be applied to a range of ice cores but is especially useful for older ice cores given the stratification of deeper segments. It will allow the research community to measure organic compounds with a high time resolution, even in the oldest of ice, to retrieve paleoclimatic information that would otherwise be lost using traditional methods.
Generating multiple resilience dividends from managing unnatural disasters. Opportunities for measurement and policy.
Authors: Mechler Reinhard , Hochrainer-Stigler Stefan
Published: March 2020

Despite solid evidence regarding the large benefits of reducing disaster risk, it has remained difficult to motivate sustained investment into disaster risk reduction and resilience. Recently, international policy debate has started to emphasize the need for focusing DRR investment toward actions that generate multiple dividends, including reducing loss of lives and livelihoods, unlocking development, and creating development co-benefits. We examine whether available and innovative decision support tools are fit-for-purpose. Focusing on the Asia region, we identify evidence of multiple dividends crafted using expert-based methods, such as cost–benefit analysis for selecting and evaluating “hard resilience-type” interventions. Given a rising demand for “softer” and systemic DRR investments in projects and programs, participatory decision support tools have become increasingly relevant. As one set of tools, resilience capacity (capital) measurement approaches may be used to support actions and decisions throughout all stages of the project cycle. Measuring capacity for resilience dividends, not outcome, such tools can serve as participatory decision support for organizations working at community and other levels for scoping out how development and disaster risk interact, as well as for supporting the co-generation of multiple resilience dividend-type solutions with those at risk.
Zinc isotope fractionation at destructive plate margins and potential implications for the global recycling signature
Authors: Rosca Carolina , König Stephan , Pons Marie-Laure , Schoenberg Ronny
Published: March 2020

Our understanding regarding the behaviour of the fluid mobile element Zn at destructive plate margins is limited. In particular the fractionation mechanisms and input-output mass-balance remains to be investigated due to implications for the spatio-temporal cycling of this vital and socio-economically relevant element. In this study, we investigate the Zn isotope systematics of subduction input provided by IODP samples from the SW Pacific in comparison to lavas from the central Tonga arc, addressed as a worldwide endmember in terms of pre-subduction mantle wedge depletion. With an improved analytical precision, we report subtle, yet resolvable Zn isotope variations between the central Tongan islands, with an overall statistically relevant variation of 0.05‰ (at ±0.014‰ 2SD). The signatures are all > 0.1‰ lighter than the subduction input at this site, suggesting a fractionation process during subduction. After careful extraction of the isotopic effect caused by mantle melting processes (using DMM δ66/64Zn JMC-Lyon provided by Sossi et al. (2018) and Wang et al. (2017) and melt extraction indices such as Sm/La, Zr/Nb, and Zn/La), a pronounced negative correlation is observed between the Zn isotopic composition of the lavas and key fluid indicators such as Ba/Th and Ce/Pb. Together with predictions from ab initio calculations and mixing models performed between Indian DMM and Rayleigh dehydration of the subducting slab, we attribute the remaining, subtle Zn isotope variations to additions by Cl-rich fluids to the individual mantle wedges. A maximum of 5% chlorine-fluid contribution is suggested for the magmatic source of Tofua, whereas smaller proportions are estimated for Kao, Late and Ata. Overall, this study sheds new light on Zn fractionation mechanisms in sediment-poor subduction zones. Implications for the long-term Zn recycling will be addressed in this presentation.

References:

Sossi, P.A., Nebel, O., O’Neill, H.S.C., Moynier, F., 2018. Zinc isotope composition of the Earth and its behaviour during planetary accretion. Chemical Geology 447, 73-84.

Wang, Z.-Z., Liu, S.-A., Liu, J., Huang, J., Xiao, Y., Chu, Z.-Y., Zhao, X.-M., Tang, L., 2017. Zinc isotope fractionation during mantle melting and constraints on the composition of Earth’s upper mantle. Geochimica et Cosmochimica Acta 198, 151- 167.
Flood hazard estimation and climate change: impacts and uncertainties for Irish catchments using CMIP6
Authors: Meresa Hadush , Murphy Conor , Fealy Rowan
Published: March 2020

In the coming decades, climate change will likely become a complex issue affecting hydrological regimes and flood hazard conditions. According to the IPCC reports, significant changes in atmospheric temperature, precipitation, humidity, and circulation are expected which may lead to extreme events including flood, droughts, heatwaves, heavy precipitation, and more intense cyclones. Although the effects of climate change on flood hazard indices is subject to large uncertainty, the evaluation of high-flows plays a crucial role in flood risk planning and extreme event management. With the advent of the Coupled Model Intercomparison Project Phase 6 (CMIP6), flood managers are interested to know how changes in catchment flood risk are expected to alter relative to previous assessments. Here we examine catchment based projected changes in flood quantiles and extreme high flow events for Irish catchments, selected to be representative of the range of hydrological conditions on the island. Conceptual hydrological models, together with different downscaling techniques are used to examine changes in flood risk projected from the CMIP6 archive for mid and end of century. Results will inform the range of plausible changes expected for policy relevant flood indices, the sensitivity of findings to use of different climate model ensembles and inform the tailoring of adaptation plans to account for the new generation of climate model outputs.
Characterization and Evolution of Marine Heat Waves in the Peruvian Upwelling System
Authors: Pietri Alice , Colas François , Mogollon Rodrigo , Espinoza-Morriberón Dante , Chamorro Adolfo , Tam Jorge , Gutiérrez Dimitri
Published: March 2020

Rapidly developing extreme events such as anomalously warm water events, known as Marine Heat Waves (MHWs), have received considerable attention in the past few years due to the significant impact they have on regional ecosystems and socioeconomic activity. The Peruvian Coastal Upwelling System (PCUS), one of the most productive ecosystem in the world in terms of fisheries, is highly exposed to climate variability in particular because of its geographic location close to the equator, and the influence of the subtropical high pressure cell variability.

The PCUS is highly influenced by El Niño events, which have been intensively studied, and whose variability is related to the longest and most intense MHWs in the region. However the very visible El Niño events probably overshadowed the MHWs of shorter duration that also have an important impact on the coastal environment as they can often go with other extreme events such as nearshore hypoxia. To date, a census of MHWs of shorter duration (less than 30 days) is lacking in the region.

Here, we investigate the characteristics (spatial variability, frequency, intensity and duration) and evolution of such MHWs in the South Tropical Eastern Pacific, with a focus on the PCUS coastal area where the ecological vulnerability is higher. Several sea surface temperature satellite products are compared to test the sensitivity of the results.

The distinction between El Niño events and regular MHWs has a major impact on the statistical distribution of MHWs properties in the South Equatorial and South Tropical Eastern Pacific as well as on their evolution over the last 35 years. First results indicate that in the equatorial region and along the Peruvian coast, fewer MHWs and of shorter duration are observed north than south of 15°S. The observed trend is an increase of MHWs occurrences, duration and intensity in the South Tropical Eastern Pacific over the last 35 years, with the exception of the coastal region off Peru where the trend in occurrences and duration is the same but the average temperature anomaly associated to MHWs has decreased. It also seems that there is no apparent preferential season for the occurrence of MHWs. A study of the possible drivers is performed in an attempt to disentangle the role of the local (wind stress, heat fluxes) and remote (equatorial wave activity) forcing.
Are economists getting climate dynamics right and does it matter?
Authors: Rezai Armon , Dietz Simon , van der Ploeg Frederick , Venmans Frank
Published: March 2020

We show that several of the most important economic models of climate change produce climate dynamics inconsistent with the current crop of models in climate science. First, most economic models exhibit far too long a delay between an impulse of CO2 emissions and warming. Second, few economic models incorporate positive feedbacks in the carbon cycle, whereby CO2 uptake by carbon sinks diminishes at the margin with increasing cumulative CO2 uptake and temperature. These inconsistencies affect economic prescriptions to abate CO2 emissions. Controlling for how the economy is represented, different climate models result in significantly different optimal CO2 emissions. A long delay between emissions and warming leads to optimal carbon prices that are too low and too much sensitivity of optimal carbon prices to the discount rate. Omitting positive carbon cycle feedbacks also leads to optimal carbon prices that are too low. We conclude it is important for policy purposes to bring economic models in line with the state of the art in climate science.
A system for detection of tampering on intermodal containers
Authors: Mosca Nicola , Negri Simone , Nitti Massimiliano , Colella Roberto , Renò Vito , Semerano Antonella , Stella Ettore
Published: March 2020

Shipping containers provide a standard and ubiquitous way to move goods between different places and countries. In fact, a large proportion of the international trade rely on them every day. It is thus understandable the importance of improving transport security of the containers hosting those goods.

It is therefore important to detect the possibility that a container has been tampered, both for avoiding losses due to theft, both for minimizing security risks due to counterfeiting or smuggling of illegal assets as soon as possible.

Standard tampering and intrusion counter-measures include locks, hard walls or reinforced curtains, tamper evident seals, etc. Most of these solutions, however, either need that the shipping company buys suitable containers (e.g. a container with hardened walls), or invest money in adding usually active devices to them (like for IR detection systems, locks, etc.).

A different way to detect anomalies can be achieved if the focus for ﬁnding intrusion evidence shifts from containers to the intermodal terminals that will receive the goods once they are ofﬂoaded from vessels, aircrafts or trains. A few solutions already exist or are being investigated, but they are usually expensive or difficult to deploy, thus reducing their spread and adoption.

In this work, the focus is on cost-effective, transportable solutions. In this context, various sensing technologies for evaluating the integrity of a container, are being explored, both on their own merits, and in combination with others. In particular, inspection based on colour and texture, 3d shape of the container, response to hyperspectral and thermal imaging are considered. 

Based on the sensors investigation, a cost-effective prototype of a “transportable” multimodal system is being devised. Such system is complemented by colour and 3d snapshot sensors, able to scan and report anomalies on a panel container or part of it. The system is designed to inspect a container and to fit in it while not in use, for logistics consideration. This work will present a prototype being experimented, along with an investigation of the obtainable results and the necessary trade-off that are necessary to develop such a system.
Understanding seed dispersal and germination in naturally disconnected stream networks to evaluate restoration success
Authors: Lind Lovisa , Su Xiaolei , Polvi Lina , Nilsson Christer
Published: March 2020

Stream networks both integrate abiotic and biotic landscape processes and transect the landscape, connecting different ecosystems and geologies longitudinally. The stream network can be divided into three process domains, as zones with distinct geomorphic processes: rapids, slow-flowing reaches, and lakes. Biotic recovery has been variable after stream restoration and it is therefore important to understand where in the catchment it is most beneficial to focus restoration and how the different process domains influence the restoration outcome. Along a stream network, potential for organism dispersal, usually by hydrochory for riparian plants, control riparian community organization. Thus, we wanted to determine whether differences in recovery of riparian vegetation after restoration are a function of seed dispersal or habitat conditions. Our main objective was therefore to predict how the local and upstream source of riparian vegetation influence the restoration outcome. Our study was located in the boreal region of northern Sweden in the Hjuksån catchment. Hjuksån is a tributary of the free-flowing Vindel River, which in turn is the largest tributary to the Ume River. We studied three major factors: dispersal, germination and establishment success of riparian vegetation. In consistence with previous studies that stagnant waterbodies, such as lakes and fens are efficient seed traps, our study indicate that lakes retain more seeds than rapids and slow-flowing reaches, which will influence the riparian community recovery as less species will continue to downstream restored reaches. However, while the germination experiment showed that lakes had the highest germination success there were no such indications for the establishment. The higher germination success might partly be explained by lakes having a higher soil moisture then rapids, which is important for the germination success. Overall, this study indicated that the dispersal, germination and establishment is very low in naturally disconnected stream networks in northern Sweden and further restoration effort might be needed to aid the slow recovery.
The impact of "Dzud" on vegetation condition in Gobi regions of Mongolia
Authors: Vova Oyudari , Kappas Martin , Fassnacht Steven R. , Renchin Tsolmon
Published: March 2020

A Dzud is a climate event in the Mongolian that causes serious environmental and economic damage. Although a natural phenomenon, its effects can be exacerbated by human activities such as livestock overgrazing and inadequate fodder, resulting in mass deaths of the livestock in the spring following a severe winter. This article is based on the analysis of various Dzud events (2000, 2001, 2002, and 2010) and their specific effect on the vegetation condition by analyzing Normalized Difference Vegetation Index NDVI in the Gobi regions of Mongolia. Our evaluation methods utilize the seasonal aridity index, time series of MODIS NDVI and data from livestock statistics. Heavy snowfall is one of the limiting factors for animal productivity and socioeconomic development in Mongolia. Based on the findings, steppe areas have the highest degree of vulnerability of climate, with the potential decline of growth grassland being stronger for humid areas. When there are high snowy winters, there is a 10 to a 20-day earlier peak of NDVI values as well as an increase in vegetation growth. Additionally, grazing pressure (caused by high livestock loss) played a minor role in plant growth. We found that during the dry winter conditions of a black Dzud, low soil moisture, and high evapotranspiration, the vegetation growth phase begins later due to water deficiency, leading to a lower peak in growth. During the year 2009/2010, a white Dzud occurred in the presence of a thick snow layer, which acted as a water reservoir. The effect of livestock loss and the reduction of grazing pressure played a minor part in vegetation recovery after different types of Dzud events in Mongolia.

 
Developing a 200-year flood chronology from reservoir sediments at Thirlmere, Northwest England
Authors: Phillips Hazel , Chiverrell Richard , Macdonald Neil
Published: March 2020

The English Lake District has experienced a number of recent devastating flood events (2005, 2009, 2015), without precedent in terms of magnitude during recent centuries. Climate projections for Northwest England have forecast intensification in frequency and magnitude of extreme precipitation, calling for a review of current catchment management practices. Flood hazard management requires precise estimates of extreme flood magnitude and frequency to better inform estimates of future risk, but are challenged by the short duration of river gauging data that often fails to capture the rarer, high magnitude events.

 

Methodological developments increasingly permit the high-resolution analysis of palaeoflood frequency and magnitude from lake sediments; but development of a regional database is challenged by the variable distribution of lakes. Conversely reservoirs were built extensively across the British uplands from the mid-eighteenth century and are more ubiquitous in their distribution. Attempts to reconstruct flood chronologies from reservoir sediments are limited, despite this broad distribution and there is a growing need to capture reservoir catchment histories to guide management of upland water resources. Better histories for reservoir catchment is needed, because though dam failures are rare recent examples (e.g. Whaley Bridge, Derbyshire, August 2019) highlight a paucity of hydrological data associated with these often aging structures.

 

Here, we investigate the sediment records from Thirlmere reservoir (Cumbria) and assess their value as indicators for flood history. A 200-year flood chronology has been interpreted from high-resolution particle size analyses and geochemical ratios diagnostic of variations in sediment grain size alongside historical documentary evidence, and a chronology has been developed through 210Pb dating. We address the following questions:

1) Is it possible to create a high-resolution flood chronology of a centennial timescale from reservoir sediments to better inform reservoir catchment management practices?

2) How similar are reservoir-based flood reconstructions to data from nearby lakes and historical records?

3) Do catchment landuse practices, for example mining activity, affect sediment delivery to the reservoir basins perturbing flood reconstruction?
Short-term retrospective forecasting of earthquakes based on temporal variations of the b-value of the magnitude-frequency distribution
Authors: Gasperini Paolo , Biondini Emanuele , Petruccelli Antonio , Lolli Barbara , Vannucci Gianfranco
Published: March 2020

In some recent works it has been hypothesized that the slope (b-value) of the magnitude-frequency distribution of earthquakes may be related to the differential stress inside the crust.  In particular, it has been observed that low b-values are associated with high stress values and therefore with high probability of occurrence of strong seismic shocks. In this paper we formulate a predictive hypothesis based on temporal variations of the b-value. We tested and optimized such hypothesis retrospectively based on the homogenized Italian instrumental seismic catalog (HORUS) from 1995 to 2018. A comparison is also made with a similar predictive hypothesis based on the occurrence of strong foreshocks.

 
Introducing Thermolab: a toolbox for Thermodynamics in MATLAB
Authors: Vrijmoed Johannes C. , Podladchikov Yury Y.
Published: March 2020

We present a set of MATLAB codes that can be used to perform equilibrium and non-equilibrium thermodynamic calculations. This will be of general use in geomaterial research and education, from the calculation of equilibrium phase diagrams to the development of dynamic models of reaction, deformation, mass and heat transport processes. The main MATLAB function calculates Gibbs energies of pure substances and mixtures using internally consistent thermodynamic databases, for rocks, minerals, melts and fluids. A general formulation of calculating Gibbs energy of mixtures based on linear algebra allows users to add custom solution models in an easy manner. The main Gibbs energy function can also be further extended, updated and customized, for example to involve other thermodynamic databases and equations of state.

We show three methods on how these Gibbs energies can be used to calculate chemical equilibrium based on optimization techniques and linear programming: 1) A brute-force method in which Gibbs energies of all possible phases and solutions are generated as a set of discrete phases. 2) A method of refining and restricting the Gibbs energies of solution phases to save computational resources and 3) A method that further saves computational resources by using system composition to generate Gibbs energies of solutions in a subset of the compositional space.

Finally, we demonstrate how these codes can be used in non-equilibrium thermodynamic processes such as reactive-fluid flow involving density and porosity changes.
Sources of uncertainty of Baltic Sea future projections
Authors: Meier Markus , Dieterich Christian , Gröger Matthias
Published: March 2020

In an ensemble of regional scenarios for the Baltic Sea we analyzed the sources of uncertainty in climate indices and environmental quality indicators. The ensemble is based on 32 regionalized scenarios where four different external drivers have been varied. Climate is represented by four different Earth System Models (ESMs). Uncertain future greenhouse gas emissions are represented by two different Representative Concentration Pathways (RCPs). Two nutrient load scenarios, broadly equivalent to two Shared Socio-economic Pathways (SSPs), describe two distinct evolutions of the regional population development, agricultural practices and food demand and two scenarios for global mean sea level rise (GMSL) measure the impact of the water level on the biogeochemical cycle in the Baltic Sea. The volume averaged temperature increase at the end of the century relative to the reference period 1976-2005 is 1.3 to 2.2 K (RCP 4.5) and 2.9 to 4.2 K (RCP 8.5). Averaged salinity changes by -2.1 and +0.2 g/kg (RCP 4.5) and -3.2 and -0.2 g/kg (RCP 8.5). For temperature, uncertainties before 2080 are dominated by natural variability and ESM biases. After 2080 the largest source of uncertainty is related to the unknown greenhouse gas concentrations. As expected, uncertainties related to either SLR or nutrient loads are negligible. For salinity, the dominating source of uncertainty during the entire 21st century is explained by the biases of the ESMs. However, natural variability and, in particular by the end of the century, uncertainties due to unknown greenhouse gas concentrations and sea level rises are important as well. For hypoxic area, uncertainties before 2040 are dominated by ESM biases. After 2040 the largest source of uncertainty is related to the unknown nutrient loads (SSPs). However, ESM biases, natural variability, unknown greenhouse gas concentrations and unknown sea level rises play an important role as well. Hence, the predictability of hypoxic area on long time scales requires accurate knowledge of various drivers and accurate quality of ESMs.

 
Improved thermal characterization of alpine permafrost sites by broadband SIP measurements
Authors: Limbrock Jonas K. , Weigand Maximilian , Kemna Andreas
Published: March 2020

Geoelectrical methods are increasingly used for non-invasive characterization and monitoring of permafrost sites, since the electrical properties of the subsoil are sensitive to the phase change of liquid to frozen water. In this context, electrical subsurface parameters act as proxies for temperature and ice content.  However, it is still challenging to distinguish between air and ice in the pore space of the rock based on the resistivity method alone due to their similarly low electrical conductivity. This ambiguity in the subsurface conduction properties can be reduced by considering the spectral electrical polarization signature of ice using the Spectral Induced Polarization (SIP) method, in which the complex, frequency-dependent impedance is measured. These measurements are hypothesized to allowing for the quantification of ice content (and thus differentiation of ice and air), and for the improved thermal characterization of alpine permafrost sites.

In the present study, vertical SIP sounding measurements have been made at different alpine permafrost sites in a frequency range from 100 mHz to 45 kHz. From borehole temperature measurements, we know the thermal state of these sites during our SIP soundings, i.e., an active layer thickness of about 4 m at the Schilthorn field site. In order to understand and to calibrate ice and temperature relationships, the electrical impedance was likewise measured on water-saturated soil and rock samples from these field sites in a frequency range from 10 mHz to 45 kHz during controlled freeze-thaw cycles (+20°C to -40°C) in the laboratory.

For field and laboratory measurements, the resistance (impedance magnitude) shows a similar temperature dependence, with increasing resistance for decreasing temperatures. For each sample, the impedance phase spectra exhibit the well-known temperature-dependent relaxation behavior of ice at higher frequencies (1 kHz - 45 kHz), with an increasing polarization magnitude for lower temperatures or larger depths of investigation, respectively. At lower frequencies (1 Hz - 1 kHz), a polarization with a low frequency dependence is observed in the unfrozen state of the samples. We interpret this response as membrane polarization, considering that it decreases in magnitude with decreasing temperature (i.e., with ongoing freezing).

Using the independently measured borehole temperature data, a systematic comparison of the SIP laboratory and field measurements indicates the possibility of a thermal characterization of an alpine permafrost site using SIP.
Local determination of the components of the deflection of the vertical using gravitational potential parameters at a neighboring point
Authors: Manoussakis Gerassimos , Korakitis Romylos
Published: March 2020

We present a method for the estimation of the components ξ and η of the deflection of the vertical using several parameters of the gravitational potential. Specifically, we assume that we know the geodetic coordinates (φ, λ, h), the magnitude of gravity g, the components ξ, η and the second partial derivatives of the gravitational potential (elements of the Eötvös matrix) at a point P. Knowing only the geodetic coordinates of a neighboring point A (at a distance up to several kilometers from P), we estimate the components ξ and η at A. The proposed method is evaluated with simulated data at several points in Greece. The results show that it may be used for the densification of a given astrogeodetic net.
Passive and active seismic studies of lithospheric structure and anisotropy beneath Sudetes (NE Variscides)
Authors: Środa Piotr , Rewers Julia , Materkowska Weronika , Ke Kuan-Yu , Working Group AniMaLS
Published: March 2020

The area of Sudetes, located at the margin of the Bohemian Massif, represents the NE-most part of the Variscan internides between the Elbe Fault in SW and the Odra Fault in NE. The lithosphere of the region is a mosaic of several distinct units/terranes with complex tectonic history ranging from the upper Proterozoic till the Quaternary. The crustal and uppermost mantle structure of this region was studied by seismic wide-angle experiment SUDETES 2003 and the results of 2-D isotropic modelling were published. Recently, this dataset, comprising off-line recordings from a net of intersecting profiles, was interpreted using anisotropic delay-time inversion. This resulted in models of 2-D distribution of upper crustal and uppermost mantle anisotropy based on azimuthal variability of the Pg and Pn traveltimes, respectively. The upper mantle of Sudetic region was the target of a passive seismic experiment AniMaLS. The project involved 23 broadband seismic stations deployed in the area of Sudetes and Fore-Sudetic block in SW Poland, supplemented with the data from 6 permanent seismic stations, operating in this area in Czech Republic and Poland. The measurements cover a ~200x100 km large area, with ~30 km inter-station spacing. The stations, deployed for a period of 24 months (2017-2019), provided broadband recordings of local, regional and teleseismic events. The aim of the experiment is to study the structure, seismic velocity variations including anisotropy distribution, and to map the upper mantle seismic discontinuities (Moho, lithosphere-asthenosphere boundary, mantle transition zone). Currently, the AniMaLS data are being interpreted using shear wave splitting method and receiver function method. The analysis of SKS and SKKS splitting was based on cross-correlation, eigenvalue minimization and transverse energy minimization methods. Resulting time delays between slow and fast S-wave components are ~1.2 sec on average, with fast velocity axis oriented largely in WNW-ESE direction, consistently with results of delay-time inversion of Pn phase traveltimes. Crustal anisotropy is characterized by similar fast axis orientation, but with lower amplitude of anisotropy. The orientation of fast axes in the crust and mantle correlates well with surface trends of tectonic units and with strike directions of major fault zones. This suggests vertically coherent deformation throughout the lithosphere, most likely during consolidation of the Sudetic region in Variscan times.