bluuebunny/crossref_metadata_2025 huggingface dataset:
The enigma of large sorted stone stripes in the tropical Ethiopian Highlands
Authors: Groos Alexander Raphael , Niederhauser Janik , Akçar Naki , Veit Heinz
Published: March 2020

The Bale Mountains in the southern Ethiopian Highlands (7-8°N) are formed of multiple superimposed flood basalts and comprise Africa’s largest plateau above 4000 m. Glacial and periglacial landforms are well-preserved and facilitate the reconstruction of the paleoclimate and landscape of the afro-alpine environment. During the Late Pleistocene, an ice cap covered the central part of the plateau and outlet glaciers extended down into the northern valleys. A striking geomorphological feature on the plateau are large sorted stone stripes that consist of hardly-weathered columnar basalt and are up to 2 m deep, 15 m wide and 200 m long. The stone stripes are located between 3850 and 4050 m at gentle slopes (4-8°) of two volcanic plugs 3-5 km south of the highest peak (Tullu Dimtu, 4377 m) and in the far west of the plateau. Sorted patterned grounds of similar size are characteristic for periglacial environments of the high latitudes, but unique for tropical mountains since their formation requires permafrost and a deep active layer. While diurnal freeze-thaw cycles in tropical mountains are sufficient for the genesis of small-scale patterned grounds, the sorting of large basalt columns (length >2 m, diameter >40 cm) assumes seasonal (or multi-annual) freeze-thaw cycles and a deep active layer. When and under which climatic conditions the sorted stone stripes in the Bale Mountains formed, remains an unsolved mystery. The stone stripes might have developed during the Late Pleistocene under periglacial conditions in close proximity to the ice cap or after deglaciation (~15-14 ka). To assess the timing of the final stagnation of the stone stripes, we determined the age of six basalt columns from two different stripes using 36Cl surface exposure dating. In addition, we installed temperature data logger in 2, 10 and 50 cm depth across the plateau and between the stone stripes to investigate the present thermal conditions and diurnal and seasonal temperature variations in the ground. The difference between the measured mean annual temperature and presumed average ground temperature for permafrost (≤0°C) indicates an extreme temperature depression on the plateau of ≥10°C during the formation period of the sorted stone stripes. Such a Late Pleistocene cooling would be unprecendented in the tropical mountains. Finally, we applied a simple statistical model forced with meteorological data from a nearby weather station to simulate ground temperatures and test which climatic preconditions are necessary for the formation of sporadic permafrost in the Bale Mountains.
Snowmelt contribution to seasonal runoff: Lessons learned from using a bucket-type model on a large set of catchments
Authors: Jenicek Michal , Ledvinka Ondrej
Published: March 2020

The streamflow seasonality in mountain catchments is largely influenced by snow. However, a shift from snowfall to rain is expected in the future. Consequently, a decrease in snow storage and earlier snowmelt is predicted, which will cause changes in spring and summer runoff. The objectives of this study were to quantify 1) how inter-annual variations in snow storages affect spring and summer runoff, including summer low flows and 2) the importance of snowmelt in generating runoff compared to rainfall. The snow storage, groundwater recharge and streamflow were simulated for 59 mountain catchments in Czechia in the period 1980–2014 using a bucket-type catchment model. The model performance was evaluated against observed daily runoff and snow water equivalent. Hypothetical simulations were performed, which allowed us to analyse the effect of inter-annual variations in snow storage on seasonal runoff separately from other components of the water balance. This was done in the HBV snow routine using the threshold temperature TT that differentiates between snow and rain and sets the air temperature of snowmelt onset. By changing the TT, we can control the amount of accumulated snow and snowmelt timing, while other variables remain unaffected.

The results showed that 17-42% (26% on average) of the total runoff in study catchments originates as snowmelt, despite the fact that only 12-37% (20% on average) of the precipitation falls as snow. This means that snow is more effective in generating catchment runoff compared to liquid precipitation. This was documented by modelling experiments which showed that total annual runoff and groundwater recharge decreases in the case of a precipitation shift from snow to rain. In general, snow-poor years are clearly characterized by a lower snowmelt runoff contribution compared to snow-rich years in the analysed period. Additionally, snowmelt started earlier in these snow-poor years and caused lower groundwater recharge. This also affected summer baseflow. For most of the catchments, the lowest summer baseflow was reached in years with both relatively low summer precipitation and snow storage. This showed that summer low flows (directly related to baseflow) in our study catchments are not only a function of low precipitation and high evapotranspiration, but they are significantly affected by previous winter snowpack. This effect might intensify the summer low flows in the future when generally less snow is expected.

Modelling experiments also opened further questions related to model structure and parameterization, specifically how individual model procedures and parameters represent the real natural processes. To understand potential model artefacts might be important when using HBV or similar bucket-type models for impact studies, such as modelling the impact of climate change on catchment runoff.
Impact of using various prior flux models on the posterior NEE derived from the Jena Carboscope regional inversion system
Authors: Munassar Saqr , Gerbig Christoph , Koch Frank-Thomas , Rödenbeck Christian
Published: March 2020

Regional flux estimates over Europe have been calculated using the two-step inverse system of the Jena CarboScope Regional inversion (CSR) to estimate the annual CO2 budgets for recent years, in cooperation with the research project VERIFY. The CSR system assimilates observational datasets of CO2 mixing ratio provided by the Integrated Carbon Observation System (ICOS) across the European domain to optimize Net Ecosystem Exchange (NEE) fluxes computed from biosphere models at a spatial resolution of 0.25 degree. Ocean fluxes are assumed to be constant over time. Fossil fuel emissions are obtained from EDGAR_v4.3 and updated based on British Petroleum (BP) statistics. Therefore, only biosphere-atmosphere exchange fluxes are considered to be optimized against the atmospheric data.

In this study we focus on the impact of using a-priori fluxes from different biosphere and ocean models on the annual CO2 budget of posterior fluxes. Results calculated using the Vegetation and Photosynthesis Respiration Model (VPRM) and Simple Biosphere/Carnegie-Ames Stanford Approach (SiBCASA) models show a consistent posterior interannual variability, largely independent of which prior fluxes are used, even though those prior fluxes show considerable differences on annual scales.
How thermochemical piles initiate plumes at their edges
Authors: Heyn Björn , Conrad Clinton , Trønnes Reidar
Published: March 2020

Deep-rooted mantle plumes are thought to originate from the margins of the Large Low Shear Velocity Provinces (LLSVPs) at the base of the mantle. Visible in seismic tomography, the LLSVPs are often numerically modeled as dense and viscous thermochemical piles. Although the piles force lateral mantle flow upwards at their edges, it is not clear if, and how, plumes are predominantly initiated at the pile margins. In this study, we develop numerical models that show a series of plumes periodically rising from the margin of an approximately 300 km thick dense thermochemical pile, with each plume temporarily increasing the pile’s local thickness to almost 370 km due to upward viscous drag from the rising plume. When the plume is pushed towards the pile center by the lateral mantle flow, the viscous drag on the dense material at the pile margin decreases and the pile starts to collapse back towards the core-mantle boundary (CMB). This causes the dense pile material to extend laterally along the CMB (about 150 km), locally thickening the lower thermal boundary layer on the CMB next to the pile, which initiates a new plume. The resulting plume cycle is reflected in both the thickness and lateral motion of the local pile margin within a few degrees of the pile edge, while the overall thickness of the pile is not affected. The frequency of plume generation is mainly controlled by the rate at which slab material is transported to the CMB, and thus depends on the plate velocity and the sinking rate of slabs in the lower mantle. Within Earth, this mechanism of episodic plume initiation may explain the suggested link between the positions of hotspots and Large Igneous Provinces (LIPs) and the LLSVP margins. Moreover, a collapse of the southeastern corner of the African LLSVP, and subsequent triggering of plumes around the spreading pile material, may explain the observed clustering of LIPs in that area between 95 and 155 Ma.
Amazon CH4 budget and its controls based on atmospheric data from vertical profiles measurements
Authors: Basso Luana , Gatti Luciana , Marani Luciano , Cassol Henrique , Tejada Graciela , Domingues Lucas , Correia Caio , Crispim Stephane , Neves Raiane , Ipia Alber , Arai Egidio , Aragão Luiz , Miller John , Gloor Manuel
Published: March 2020

Wetland emissions are considered the main natural global Methane (CH4) source, but it is budget remains highly uncertain. Tropical regions like the Amazon, host some of the largest wetlands/seasonally flooded areas on the globe. However, tropical regions are still poorly observed with large-scale integrating observations. Here we present the first atmospheric sampling of the lower troposphere over the Amazon using regular vertical profile greenhouse gas and carbon monoxide (CO) observations at four sites. Since 2010 we collected bimonthly CH4, to provide solid seasonal and annual CH4 budgets with large spatial resolution. Vertical profiles are sampled using light aircraft, high-precision greenhouse gas and CO analysis of flask air, fortnightly between 2010 to 2018. The results show a regional variation in CH4 emissions. There are comparably high emissions from the northeast part of the Amazon exhibiting strong variability, with particularly high CH4 fluxes in the beginning of the wet season (January to March). A second period of high emissions occurs during the dry season. The cause of the high emissions is unclear. In the other three sites located further downwind along the main air-stream are observed lower emissions, that represents approximately 25-30% of what is observed in the northeast region and with a clear annual seasonality. In addition, these data show an interannual variability in emissions magnitude, so we discuss how these data can be correlate to climate variables (like temperature and precipitation) and with human-driven changes (like biomass burning) that could be influencing this variability. Over the full period the Amazon (total area of around 7.2 million km2) was a source of CH4, of approximately 46 ± 6 Tg/year, which represent 8% of the global CH4 flux to the atmosphere. Using a CO/CH4 emission ratio calculated in this study we find a biomass burning contribution varying between 10 and 23% of the total flux at each site.

 

Acknowledgment: FAPESP (2019/23654-2, 2018/14006-4, 2016/02018-2, 2008/58120-3, 2011/51841-0), NASA, ERC (GEOCARBON, Horizon 2020/ASICA), NERC (NE/F005806/1), CNPq (480713/2013-8).
Hazard assessment of landslide-prone areas on highly weathered dunite rock in Bello Oriente, Medellín, Colombia (Project Inform@Risk)
Authors: Breuninger Tamara , Gamperl Moritz , Thuro Kurosch
Published: March 2020

The project Inform@Risk, a collaboration of German and Colombian Universities and Institutes funded by the German government, aims to install a landslide early warning system in the informal settlements in Medellín, Colombia. In the recent past the city has suffered from multiple landslides, some of them with up to 500 casualties. The informal settlements in the steep slopes at the city borders grow rapidly, which destabilizes the ground and complicates the installation and operation of an early warning system. Therefore, key goal of the project is to include the community in the process of the development of the early warning system.

Medellín is embedded in the Aburrá Valley in the Cordillera Central of the Andes. The region around the city consists of different triassic and cretaceous metamorphic rocks and magmatic batholites and plutonites. Especially the north-eastern slope is prone to landslides, as it is very steep and made up of a deep cover of soil over highly weathered dunite rock.

During the first field trip, carried out in August 2019, former landslide areas were located, and ERT-measurements were conducted at the study site Bello Oriente in the northeast of Medellín. After a first evaluation of the findings, the soil cover seems to be over 50 m high in the middle of the slope, which indicates a deep-seated landslide, that might have been moving downhill very slowly for thousands of years. The more dangerous landslides however, which are much faster, are the shallow ones on the surface. These landslides can appear on top of each other and are distributed across the whole study area but are most concentrated between and above the last houses of the barrio. During a second field campaign in 2020, the ERT-profiles will be calibrated and complemented by drillings and the hazard map will be completed accordingly.
Patterns of hydrochorous dispersal in agricultural channels
Authors: Vinatier Fabrice , Rudi Gabrielle , Belaud Gilles , Bailly Jean-Stéphane
Published: March 2020

rimary soilIditches during short but intense storms. Furthermore, these man made ditches provide valuable habitat for fauna and flora, but the spread of the weed could be limited by preserving existing hydraulic structures or maintaining areas where the density of terrestrial vegetation is sufficient to enhance seed retention downstream.
Revealing tectonic evolution across the Northeastern Flemish Cap-Goban Spur margin
Authors: Yang Pei , Welford J.Kim
Published: March 2020

In past years, a good understanding of the structure and tectonics of the Flemish Cap and the Goban Spur margin has been obtained based on seismic data, potential field data, and borehole data. However, due to limited data coverage and quality, the rift-related domains along the margin pair have remained poorly defined and their architecture has been primarily delineated on the basis of a small number of co-located 2-D seismic profiles. In addition, according to previous studies, the geophysical characteristics (e.g. velocity structure, crustal thickness, seismic patterns, etc.) across both the margins are strikingly different. Furthermore, from restored models of the southern North Atlantic, some scholars argue against the linkage of the Goban Spur and the Flemish Cap, questioning the widely-accepted “conjugate” relationship of the two margins. However, these restored models are mainly dependent on potential field data analysis, lacking seismic constraints, particularly for the Irish Atlantic Margin.

In this study, new long offset 2D multichannel seismic data, acquired in 2013 and 2014 by Eni Ireland for the Department of Communications, Climate Action & Environment of Ireland, cover the shelf, slope, and deepwater regions of the offshore Irish Altlantic margin. Combining these with seismic reflection data at the NE Flemish Cap, seismic refraction data, DSDP drilling sites, gravity and magnetic maps, crustal thickness maps, and oceanic isochrones, we integrate all constraints together to characterize the structure and evolution of both margins. These geophysical data reveal significant along-strike structural variations along both margins, and aid to delimit five distinct crustal zones related to different rifting stages and their regional extents. The geometries of each crustal domain are variable along the margin strike, probably suggestive of different extension rates during the evolution of the margin and/or inherited variations in crustal composition and rheology. Particularly, the along-strike exhumed serpentinized mantle domain of the Goban Spur margin spans a much wider (~ 42 - 60 km) area while it is much narrower (~25 km) at the NE Flemish Cap margin. In the exhumed domain, only peridotite ridges are observed at the Flemish Cap, while both peridotite ridges and a wide region of exhumed mantle with deeper basement are observed at the Goban Spur, indicative of a more complex evolutionary model than previously thought for both margins. Plate reconstruction of the Goban Spur and the Flemish Cap using GPlates reveals asymmetry in their crustal architectures, likely due to rift evolution involving more 3-D complexity than can be explained by simple 2-D extensional kinematics. In spite of uncertainties, the crustal architecture comparison between the two margins provides 3D seismic evidence related to the temporal and spatial rifting evolution on both sides.
Mercury dynamics from pan-Canadian survey of lakes: analyses of sediment cores
Authors: Gregory-Eaves Irene , Beaulieu Marieke , Amyot Marc , Griffiths Katherine , Poulain Alexandre
Published: March 2020

Strong measures have been taken since the 1970s to reduce mercury emissions in Canada. However, long-range transport of emissions continues and constitutes a large percentage of the total anthropogenic deposition of mercury in Canada. Natural sources of mercury are also heterogeneously distributed across the Canadian landscape.  As part of the LakePulse network (www.lakepulse.ca), we are quantifying mercury concentration in hundreds of lake sediment cores across 13 Canadian ecozones. Analyses from eastern Canada lakes showed that total mercury is significantly different among ecozones, and many ecozones showed higher total mercury concentrations in contemporary sediments.  Contemporary methyl mercury concentrations also differed among ecozones. Our overarching goals are to map the heterogeneity in mercury concentrations across the country and to identify the most parsimonious set of predictors considering a suite of physico-chemical and land-use variables from lakes and their watersheds set across the temperate to subarctic landscape.
Late Pleistocene Palaeohydrology of the Moksha River (the Volga Basin)
Authors: Matlakhova Ekaterina , Panin Andrei , Ukraintsev Vadim
Published: March 2020

The Moksha River valley was studied in its lower part between the Tsna River confluence and the mouth of the Moksha River. Wide floodplain and two levels of terraces are presented on the studied part of the valley. The height of the floodplain is from 1 to 6 m, of the first terrace – about 9-11 m, of the second terrace – 18-22 m. The width of the valley in this area is about 14-16 km, but sometimes it can reach 20-22 km and more. The width of the floodplain is about 12-14 km.

The Moksha River is a meandering channel. Large and small (modern-size) meandering palaeochannels spread widely on the floodplain surface. These palaeochannels were the main objects of our study. Small palaeochannels have the same parameters as the modern river channel: their width is about 100-150 m, wavelength is between 300-400 and 600-700 m. For the large palaeochannels (macromeanders) the mean parameters are the following: width is about 250-300 m, wavelength is about 1500-2000 m. These large palaeochannels are the signs of high flood activity epoch(s).

In our study we used a number of field and laboratory methods. Twelve boreholes in large and small palaeochannels were made during fieldwork in August-September 2019. Organic material from studied palaeochennels was sampled to make radiocarbon (AMS) dating to find the time of palaeochannels’ formation and infilling. Also we made the reconstructions of paleo-discharges of the Moksha River based on paleochannels’ parameters.

We studied both large and small palaeochannels to reconstruct palaeohydrology and history of the Moksha River valley development in Late Pleistocene. Large palaeochannels correspond to the time of high river runoff. The oldest ones of small palaeochannels were studied to know the time of lowering of the river runoff. Presumably, large palaeochannels were formed at the end of Late Glacial (after LGM) when river runoff was much higher than the modern one. This period of extremely high runoff was previously distinguished in many river valleys of East European Plain, where formation of large paleochannels is usually associated with Late Glacial (the end of MIS 2). Lowering of runoff on the central part of the East European Plain is usually associated with the beginning of the Holocene.

This study is supported by Russian Science Foundation (Project № 19-17-00215).
Probabilistic ULF models: how do they improve our understanding of the physics?
Authors: Bentley Sarah , Watt Clare , Thompson Rhys
Published: March 2020

Probabilistic modelling is used heavily in weather and climate models to accurately represent the full range of possible physical states, thereby improving forecasts and capturing the uncertainty inherent in a complex system. Here, we begin to apply probabilistic modelling to ULF waves. Eventually, we aim to better determine the impact of ULF waves on Earth’s radiation belts; by representing the full probability distribution of radial diffusion coefficients we will represent physical reality more faithfully than solely using the mean or median.

However, to construct such a model, we first need to determine the probability distributions of the radial diffusion coefficient, which varies with the power in the underlying ULF waves. Therefore we present an analysis of the distributions of wave power spectral density for both ground-based magnetometers (CARISMA) and the corresponding in situ observations. We compare these distributions, examine the relationships between them and comment on the new physical insights this probabilistic approach reveals. Differences between distributions seen on the ground and in space give us new insights into the generation and propagation of ULF waves in the magnetosphere. We comment on the consequences of these types of distributions for probabilistic modelling. We also discuss how these distributions change with the driving solar wind; in particular, whether upper and lower bounds of power at the ground determined by the solar wind are seen in space. These bounds may indicate a limit to the ability of the magnetosphere to support ULF waves, and therefore limits on the resulting radial diffusion.
A circumpolar coupled ocean – Antarctic ice sheet configuration for investigating recent changes in Southern Ocean heat content
Authors: Pelletier Charles , Zipf Lars , Haubner Konstanze , Goosse Hugues , Pattyn Frank , Mathiot Pierre
Published: March 2020

From 2016 on, observed tendencies of Southern Ocean sea surface temperatures and Antarctic sea ice extent (SIE) have shifted from cooling down (with SIE increase) to warming up (SIE decrease). This change of Southern Ocean surface thermal properties has been sustained since, which indicates that it is not solely due to the interannual variability of the atmosphere, but also to modifications in the ocean itself. Among other physical phenomena, the acceleration of continental ice shelf melt, through its subsequent impact on the Southern Ocean stratification, has been proposed as one of the potential meaningful drivers of the sea ice changes. Reciprocally, recent studies suggest that besides atmosphere forcings, the upper ocean thermal content bears significant impact on ice shelf melt rates and dynamics. Here we present a new circumpolar coupled Southern Ocean – Antarctic ice sheet configuration aiming at investigating the impact of this ocean – continental ice feedback, developed within the framework of the PARAMOUR project. Our setting relies on the ocean and sea ice model NEMO3.6-LIM3 sending ice shelf melt rates to the Antarctic ice sheet model f.ETISh v1.5, who in turn responds to it and provides updated ice shelf cavity geometry. Both technical aspects and first coupled results are presented.
Summer drought conditions promote the dominant role of phytoplankton in riverine nutrient dynamics
Authors: Kamjunke Norbert , Rode Michael , Baborowski Martina , Kunz Vanessa , Lechtenfeld Oliver , Herzsprung Peter , Weitere Markus
Published: March 2020

Large rivers play a relevant role in the nutrient turnover from land to ocean. Here, highly dynamic planktonic processes are more important compared to streams making it necessary to link the dynamics of nutrient turnover to control mechanisms of phytoplankton. We investigated the basic conditions leading to high phytoplankton biomass and corresponding nutrient dynamics in the eutrophic River Elbe (Germany). In a first step, we performed six Lagrangian samplings in the lower river part at different hydrological conditions. While nutrient concentration remained high at low algal densities in autumn and at moderate discharge in summer, high algal concentrations occurred at low discharge in summer. Under these conditions, concentrations of silica and nitrate decreased and rates of nitrate assimilation were high. Soluble reactive phosphorus was depleted and particulate phosphorus increased inversely. Rising molar C:P ratios of seston indicated a phosphorus limitation of phytoplankton. Global radiation combined with discharge had a strong predictive power to explain maximum chlorophyll concentration. In a second step, we estimated nutrient turnover exemplarily for N during the campaign with the lowest discharge. Mass balance calculations revealed a total nitrate uptake of 455 mg N m-2d-1 which was clearly dominated by assimilatory phytoplankton uptake whereas denitrification and other benthic processes were only of minor importance. Phytoplankton density, which showed a sigmoidal longitudinal development, dominantly explained gross primary production, related assimilatory nutrient uptake and respiration. Chlorophyll a concentration and bacterial abundance affected the composition of dissolved organic matter and were positively related to a number of CHO and CHNO components with high H/C and low O/C ratios but negatively to several CHOS surfactants. In conclusion, nutrient uptake in the large river strongly depends on the growth conditions for phytoplankton, which are favored during summer drought conditions.
Aeolian sediments as a palaeoclimate proxy in the transition zone between the Asian summer monsoon and the mid-latitude westerlies
Authors: Stauch Georg , Nottebaum Veit , Lehmkuhl Frank
Published: March 2020

For this study we analysed OSL (optical stimulated luminescence) ages from aeolian sands or sandy deposits in Mongolia and the north-eastern Tibetan Plateau for the last 21 ka. While the north-eastern Tibetan Plateau is at the northern boundary of the Asian summer monsoon extent, the mid-latitude Westerlies control the climate in Mongolia. Aeolian sediments are widespread in both areas, ranging from thin sand covers with a high silt content in the mountains to large sand sheets with well-developed dune systems in the basins. We collected all available OSL ages, which were published until 2019 and analysed them for their spatial and temporal distribution. The dataset comprises nearly 350 OSL ages. However, while there is a large number of OSL ages available from the north-eastern Tibetan Plateau, only 68 ages from aeolian sediments from central and western Mongolia meet our quality criteria.

There are some remarkable differences in the timing of aeolian sediment deposition between these two areas. While in both areas only few ages from the last glacial maximum are available, aeolian deposition in Mongolia incepts at the beginning of the late glacial at 17 ka. In contrast, permanent aeolian deposition on the north-eastern Tibetan Plateau did not start before 13 ka. We interpret this signal as a time lag between the strengthening of the mid-latitude westerlies and the Asian summer monsoon after the last glacial. An increase in moisture caused by the two atmospheric systems resulted in an enhanced vegetation cover and consequently in the trapping and permanent fixation of aeolian sediments.

Furthermore, during the early Holocene at around 10.5 to 8.5 ka no OSL ages are available from Mongolia while on the monsoon influenced north-eastern Tibetan Plateau a comparably high number of OSL ages point to an enhanced trapping of aeolian sediments. At this stage, a straightforward explanation for the gap in the age distribution in Mongolia is not obvious. It might be caused by the generally wet climate conditions due to enhanced moisture transport to the area due to strong westerlies and thus the diminishing of source areas for aeolian entrainment by denser vegetation covers. The enhanced westerlies would be caused by higher insolation values and are reflected in several archives, especially from northern Mongolia. However, the gap might also just be related to the generally low number of OSL ages from Mongolia.

Both areas show an increase in aeolian activity in the late Holocene, indicating a return to drier conditions after wetter climate conditions in the mid-Holocene. Drier conditions started on the north-eastern Tibetan Plateau at around 3.5 ka and in Mongolia at 2 to 3 ka. This trend is documented in a large number of archives in central Asia and is related to a weakening of the Asian summer monsoon as well as the mid-latitude Westerlies.
GIC drivers - the Characteristics of Storm-time Rapid Geomagnetic Variations
Authors: Opgenoorth Hermann J. , Schilling Audrey , Hamrin Maria
Published: March 2020

Rapid storm-time geomagnetic disturbances, typically at sub-auroral latitudes, have been recognized as one of the most detrimental space weather phenomena, potentially leading to damage to and outage of critical power infrastructure. We can show that sub-auroral magnetic spikes in storms (of the order of 1000 nT/min) do resemble in their appearance and spatio-temporal behavior small but intense and very short-lived substorms, including three-dimensional current wedge and electrojet-enhancement formation. Statistically these spikes do occur at all local times, but preferably pre-midnight and around 0600 MLT in the morning sector, which is only partially in agreement with the substorm analogy, and indicate that there may indeed be several mechanisms at work. We will present results from event and statistical studies to clarify the physical characteristics and potential drivers for these potentially most damaging geomagnetic disturbances in the SWx realm.

 
A new database of independently estimated eruption source parameters devoted to eruptive column model evaluation
Authors: Engwell Samantha , Aubry Thomas , Biass Sebastien , Bonadonna Costanza , Bursik Marcus , Carazzo Guillaume , Eychenne Julia , Gouhier Mathieu , Grainger Don , Jellinek Mark , Jessop David , Mastin Larry , Pyle David , Scollo Simona , Taylor Isabelle , Van Eaton Alexa , Wallace Kristi , Woodhouse Mark
Published: March 2020

Eruptive column models are crucial for managing volcanic crises, forecasting future events, and reconstructing past eruptions. Given their central role in volcanology and the large uncertainties weakening their predictions, the evaluation and improvement of these models is critical. Such evaluation is challenging as it requires independent estimates of the main model inputs (e.g. mass eruption rate) and outputs (e.g. column height). Despite recent efforts to extend datasets of independently estimated eruption source parameters (ESP) (e.g. Mastin 2014, Aubry et al. 2017), there is no standardized, maintained, and community-based ESP database devoted to the evaluation of eruptive column models.

Here we present a new ESP database designed to respond to the needs of the plume modelling community, and which will also be valuable to observatories, field volcanologists, and volcanic ash advisory centers. We compiled data for over 130 eruptive events with independent estimates of: i) the mass eruption rate; ii) the height reached by the column; and iii) atmospheric conditions during the eruption. In contrast with previous ESP datasets, we distinguish estimates of column height that relate to different phases (ash and SO2) and parts of the column (plume top or umbrella). We additionally provide the total grain size distribution, uncertainties in eruption parameters, and multiple sources for atmospheric profiles for events where these parameters are available. The database also includes a wealth of additional information which will enable modelers to distinguish between different eruptions when evaluating or calibrating models. This includes the type of eruption, the morphology of the plume (weak/transitional/strong), and the occurrence and mass entrained within pyroclastic density currents.

We will apply the new database to revisit empirical scaling relationships between the mass eruption rate and “plume height”. In particular, we will show how such relationships depend on the type of height (e.g. SO2 height vs. ash top height) and eruption (e.g. magmatic vs. phreatomagmatic) considered. We will also discuss the difficulties and limitations of compiling ESP estimates from the literature as well as characterizing fundamentally unsteady volcanic events by a single value for each ESP.
Extending near fault earthquakes catalogs using convolutional neural network and single-station waveforms
Authors: Majstorović Josipa , Poli Piero
Published: March 2020

The machine learning (ML) algorithms have already found their application in standard seismological procedures, such as earthquake detection and localization, phase picking, earthquake early warning system, etc. They are progressively becoming superior methods since one can rapidly scan voluminous data and detect earthquakes, even if buried in highly noisy time series.

We here make use of ML algorithms to obtain more complete near fault seismic catalogs and thus better understand the long-term (decades) evolution of seismicity before large earthquakes occurrence. We focus on data recorded before the devastating L’Aquila earthquake (6 April 2009 01:32 UTC, Mw6.3) right beneath the city of L’Aquila in the Abruzzo region (Central Italy). Before this event sparse stations were available, reducing the magnitude completeness of standard catalogs. 

We adapted existing convolutional neural networks (CNN) for earthquake detection, localisation and characterization using a single-station waveforms. The CNN is applied to 29 years of data (1990 to 2019) recorded at the AQU station, located near the city of L’Aquila (Italy). The pre-existing catalog maintained by Istituto nazionale di geofisica e vulcanologia is used to define labels and train and test the CNN. We are here interested in classifying the continuous three-component waveforms into four categories, noise/earthquakes, distance (location), magnitude and depth, where each category consists of several nodes. Existing seismic catalogs are used to label earthquakes, while the noise events are randomly selected between the catalog events, evenly represented by daytime and night-time periods.

We prefer CNN over other methods, since we can use seismograms directly with very minor pre-processing (e.g. filtering) and we do not need any prior knowledge of the region.
Ecosystem services of organic wine production – Linking different views
Authors: Iglesias Ana , Garrote Luis , Sotes Vicente , Bardaji Isabel
Published: March 2020

Aiming to explore and exchange ideas about the ecosystem services of organic wine production, this presentation will address two questions. First, what is the potential for improving ecosystem services? This is explored at the continental scale, looking at the spatial distribution of the effect of organic management practices in permanent crops. Second, how can the targets be reached based on public and private solution? This is explored based on local policy targets and contract based solutions including the private sector and the value chain. A case study of organic wine production in the Spanish Denomination of Origin Rueda is presented as a practical example. The content of the study is based on the results of the iSQAPER (http://www.isqaper-project.eu/) and CONSOLE (https://console-project.eu/) H2020 projects.
Long term hydrologic simulations for the meso-scale catchments Rur and Bode in Germany by TSMP
Authors: Yang Zhenlei , Kurtz Wolfgang , Gebler Sebastian , Schüler Lennart , Kollet Stefan , Vereecken Harry , Hendricks-Franssen Harrie-Jan
Published: March 2020

Integrated terrestrial systems modeling is important for the comprehensive investigation of the coupled terrestrial water, energy and biogeochemical cycles. In this work, we applied the Terrestrial Systems Modeling Platform (TSMP) to the two meso-scale catchments in Germany (Rur and Bode) to conduct a long time hydrologic simulation with a focus on variables such as soil moisture, evapotranspiration (ET) and groundwater recharge. Simulations for the Rur and Bode catchments were performed at three different spatial horizontal model resolutions (1000, 500, and 200m) with CLM and CLM-PF in TSMP. Each of the three resolution models was run for 24 years (1995-2018) with transient atmospheric forcings derived from COSMO-REA6 data. The long term simulation results show that the summer of 2018 resulted in the lowest soil moisture content over the time series that is around 0.20, lower than the dry summers of 1995 and 2003. ET was more reduced in July-August 2018 due to the decrease of soil moisture content during this period. Nevertheless, actual evapotranspiration was even in the summer of 2018 often not limited by soil moisture content. For these catchments ET is most of the time energy limited. In addition, the vegetation evaporation (resulting from interception) accounts for the smallest percentage of the ET (ca. 20%), whereas the vegetation transpiration and soil evaporation account for almost the same percentage of the total ET (each 40% approximately). Both the CLM and CLM-PF simulation results indicate that grid coarsening (lower model resolution) leads to larger ET and soil moisture content, which is related to the decreasing slope gradient with grid coarsening. The analysis of groundwater recharge is underway.
The deglaciation of the northwestern Laurentide Ice Sheet in the Mackenzie Mountains
Authors: Stoker Benjamin J. , Margold Martin , Froese Duane G. , Gosse John C.
Published: March 2020

The northwestern sector of the Laurentide Ice Sheet coalesced with the Cordilleran Ice Sheet over the southern Mackenzie Mountains, and with local montane glaciers along the eastern slopes of the Mackenzie Mountains. Recent numerical modelling studies have identified rapid ice sheet thinning in this region as a major contributor to Meltwater Pulse 1A. Despite advances in remote sensing and numerical dating methods, the configuration and chronology of the northwestern sector of the Laurentide Ice Sheet has not been reconstructed in detail. The last available studies date back to the 1990s, where field surveys and mapping from aerial imagery were used to reconstruct the Last Glacial Maximum glacier extents in the Mackenzie Mountains. Cross-cutting relationships between glacial landforms and a series of 36Cl cosmogenic nuclide dates were used to propose a deglacial model involving a significant ice readvance in the region. However, the chronological evidence supporting the readvance is uncertain because the individual ages are few and poorly clustered. Here we present an updated map of the Last Glacial Maximum glacial limits and the recessional record in the Mackenzie Mountains, based on glacial geomorphological mapping from the ArcticDEM. Sixteen new 10Be dates from four sites that were previously glaciated by the Laurentide Ice Sheet constrain the deglacial sequence across the region. These dates indicate ice sheet detachment from the eastern Mackenzie Mountains at ~16 ka as summits became ice-free. The Mackenzie Valley at ~ 65 °N became ice free at ~ 13 – 14 ka, towards the end of the Bølling-Allerød warm period. These chronological constraints on the deglaciation of the Laurentide Ice Sheet allow us to reinterpret landform relationships in the Mackenzie Mountains to reconstruct the ice sheet retreat pattern. Our updated model of the LGM extent and timing of deglaciation in the Mackenzie Mountains provides important constraints for quantifying past sea level contributions and numerical modelling studies.
The implications of landscape visual impact on future highly renewable power systems: a case study for Great Britain
Authors: Price James , Mainzer Kai , Petrović Stefan , Zeyringer Marianne , McKenna Russell
Published: March 2020

The decarbonisation of power production is key to achieving the Paris Agreement goal of limiting global mean surface temperature rise to well below 2°C, particularly so given the drive to electricity transport and heat. At the same time, variable renewable energy (VRE) sources such as solar photovoltaics (PV) and wind have seen rapid cost reductions in recent decades bringing them into cost parity with base load fossil generation. Therefore, recent long term planning studies, which utilise cost-optimising models, have demonstrated the important role of VREs in decarbonising power systems across the world. However, while techno-economically detailed, such studies tend to neglect key social factors that often shape the real world evolution of the energy system.

Of particular relevance to VRE deployment is their visual impact on the landscape which can act to undermine their public acceptability. Here, we use crowd-sourced scenicness data to derive spatially explicit, empirically grounded wind energy capacity potentials for three scenarios of public sensitivity to this visual impact. We augment these with a detailed analysis of Great Britain’s (GB) solar PV capacity potential. We then use these scenarios in a cost-optimising model of GB’s power system to assess their impact on the cost and design of the electricity system in 2050. Our results show that the levelised cost of the system can increase by up to 15% when public sensitivity to visual impact is high compared to low. In part this is driven by our finding that some of the most picturesque parts of GB also happen to be the most cost-effective for onshore wind, leading to large reductions in installed capacity as we move through our sensitivity scenarios. Indeed, deployment is heavily limited in Scotland and the South-West which in turn acts to limit the spatial diversity of onshore wind. We conclude that it is essential for policy makers to consider these cost implications and to find mechanisms to ameliorate the visual impact of onshore wind in local communities.
Monitoring and Retrieval of High-Level Radioactive Waste
Authors: Mintzlaff Volker , Stahlmann Joachim
Published: March 2020

Monitoring and Retrieval of High-Level Radioactive Waste

The retrievability of high-level radioactive waste (HAW) is defined as the option to retrieve previously emplaced waste from a respository. This is a design requirement in many countries, as for example in Germany, justified by the need to react on possible failures in the repository system.

Retrievability affects the footprint of the repository (Léon-Vargas et al., 2017) and requires a monitoring program (Stahlmann et al., 2018), as the decision on retrieval should be justified on sound basis. For a holistic analysis of the design consequences of retrievability of high-level radioactive waste it is necessary to get information about the retrieval process itself. In TRANSENS, a transdisciplinary research platform for HAW disposal research, the retrieval process will be analyzed in general.

The presentation will focus on a generic repository approach based upon Stahlmann et al. (2018) modified for the analysis of the retrieval process. Main impacts of the retrieval works on the host rock were identified, as the effects of the redriven emplacement drifts on the repository system. The presentation will focus on these processes and give a short outlook on their consequences for a monitoring program.

 

Leon Vargas, R.; Stahlmann, J.; Mintzlaff, V. (2017): Thermal impact in the geometrical settings in deep geological repositories for HLW with retrievability and monitoring. 16th International High-Level Radioactive Waste Management Conference (IHLRWM 2017), Charlotte, NC, April 9-13, 2017.

Stahlmann, J.; Mintzlaff, V.; León Vargas, R.P.; Epkenhans, I. (2018): Normalszenarien und Monitoringkonzepte für Tiefenlager mit der Option Rückholung. Generische Tiefenlagermodelle mit Option zur Rückholung der radioaktiven Reststoffe. ENTRIA-Arbeitsbericht-15. Braunschweig.
Size-resolved aerosol pH over Europe during summer
Authors: Pandis Spyros , Zakoura Maria , Kakavas Stelios , Nenes Athanasios
Published: March 2020

The dependence of aerosol acidity on particle size, location and altitude over Europe during a summertime period is investigated using the hybrid version of aerosol dynamics in the chemical transport model PMCAMx. The pH changes more with particle size in northern and southern Europe owing to the enhanced presence of non-volatile cations (Na, Ca, K, Mg) in the larger particles. Differences of up to 1-4 pH units are predicted between sub- and super-micron particles, while the average pH of PM1-2.5 can be as much as 1 unit higher than that of PM1. Most aerosol water over continental Europe is associated with PM1, while PM2.5-5 and PM5-10 dominate the water content in the marine and coastal areas due to the relatively higher levels of hygroscopic sea salt. Particles of all sizes become increasingly acidic with altitude (0.5-2 units pH decrease over 2.5 km) primarily because of the decrease in aerosol liquid water content (driven by humidity changes) with height. Inorganic nitrate is strongly affected by aerosol pH with the highest average nitrate levels predicted for the PM2.5-5 range and over locations where the pH exceeds 3. Dust tends to increase aerosol water levels, aerosol pH and nitrate concentrations for all particle sizes. This effect of dust is quite sensitive to its calcium content. The size-dependent pH differences carry important implications for pH-sensitive processes in the aerosol.