bluuebunny/crossref_metadata_2025 huggingface dataset:
Multi-methodological investigation of a retrogressive thaw slump in the Richardson Mountains, Northwest Territories, Canada
Authors: Kunz Julius , Kneisel Christof , Ullmann Tobias , Baumhauer Roland
Published: March 2020

The Mackenzie-Delta Region is known for strong morphological activity in context of global warming and permafrost degradation, which reveals in a large number of retrogressive thaw slumps. These are frequently found along the shorelines of inland lakes and the coast; however, this geomorphological phenomenon also occurs at inland ​​streams and creeks of the Peel Plateau and the Richardson Mountains, located in the southwest of the delta. Here several active retrogressive thaw slumps are found of which some have reached an extent of several hectares, e.g. the mega slump at the Dempster Creek.

In this study we investigated a recent retrogressive thaw slump at the edge of the Richardson Mountains close to the Dempster Highway to determine the subsurface properties using non-invasive geophysical methods. We performed three-dimensional Ground Penetrating Radar (GPR) surveys, as well as quasi-three-dimensional Electrical Resistivity Tomography (ERT) surveys in order to investigate the subsurface characteristics adjacent to the retreating headwall of the slump. These measurements provide information on the topography of the permafrost table, ice content and/or water pathways on top, within or under the permafrost layer. Additionally, we performed manual measurements of the active layer thickness for validation of the geophysical models. The approach was complemented by the analysis of high-resolution photogrammetric digital elevation models (DEM) that were generated using in situ drone acquisitions.

The measured active layer depths show a strong influence of the relief and especially of small creeks on the permafrost table topography. Likely, this influence also is the primary trigger for the initial slump activity. In addition, the ERT measurements show strong variations of the electrical resistivity values in the upper few meters, which are indicative for heterogeneities, also within the ice-rich permafrost body. Especially noticeable is a layer of low resistivity values in an area adjacent to the slump headwall. This layer is found at depths between 4m to 7m, which approximately corresponds to the base of the headwall. Here, the low resistivity values could be indicative for an unfrozen or water-rich layer below the ice-rich permafrost. Consequently, this layer may have contributed to the initial formation of the slump and is important for the spatial extension of the slump.

These results present new insights into the subsurface of an area adjacent to an active retrogressive thaw slump and may contribute to a better understanding of slump development.
Modelling rock walls destabilization caused by hydrostatic pressure in frozen/unfrozen bedrock (Hochvogel & Zugspitze, Germany)
Authors: Stoll Verena , Scandroglio Riccardo , Krautblatter Michael
Published: March 2020

One of the most important but still unknown destabilizing factors of rock faces in periglacial environments is the contribution of water in terms of hydrostatic pressure (e.g. Piz Cengalo in 2017). Its presence has often been registered in major rock failures, but it has never been quantified. Perched water table >>20m above virtually impermeable permafrost bedrock can cause excessive hydrostatic stress on affected rockwalls. Climate change related intensification of rainstorms as well as permafrost degradation promote water accumulation. An increase in rockfall activity due to higher water pressure peaks is therefore expected, thus intensifying the risk for humans and infrastructures.

Here we conduct a hydromechanical stability analysis at two study sites in the Northern Calcareous Alps where this effect has been observed. We use the distinct element method developed in the software UDEC (Itasca); the required geometric and mechanical model input parameters were obtained from previous studies with direct investigations and laboratory tests in frozen/unfrozen conditions. Infiltration from rainfall or snow/ice melting is expected to create extreme pressure peaks, especially when permafrost seals fractured rock.

Here we present results from:

the permafrost affected Zugspitze summit (Wetterstein Range), where sealing permafrost allows the meltwater to accumulate in the active layer. This causes high hydrostatic pressure, evaluated by relative gravimetry methods and with the help of a fracture mapping.

a preparing high-magnitude rock fall at the Hochvogel (Allgäu Alps), where perched water could destabilize up to 260’000 m³. Displacement measurements on the summit showed acceleration following intense precipitation.

Our model proves that a column of water can bring the Zugspitze north face to instable equilibrium. This happens with different intensities according to frozen/unfrozen conditions and various depth of the active layer, if the hydrostatic pressure is adequate (0.2-0.4 MPa = 20-40 m water column).

Water could also increase the destabilization rates of the south-east face of Hochvogel by adding hydrostatic pressure. A Factor of Safety < 1 is reached when other water-related factors are considered, like: (i) reduction of cohesion in saturated joints, (ii) decrease of the interface friction angle in fractures and (iii) accelerates weathering along the shear plane
Towards the first circumarctic N2O budget – Extrapolating to the landscape scale
Authors: van Delden Lona , Marushchak Maija , Voigt Carolina , Grosse Guido , Faguet Alexey , Lashchinskiy Nikolay , Kerttula Johanna , Biasi Christina
Published: March 2020

The Arctic is warming at twice the rate of the rest of the globe. While it has been increasingly highlighted that thawing permafrost accelerates soil organic matter decomposition, research on biogeochemical N cycling is still underrepresented. Arctic nitrous oxide (N2O) emissions have long been assumed to have a negligible climatic impact but recently increasing evidence has emerged of N2O hotspots in the Arctic. Even in small amounts, N2O has the potential to contribute to climate change due to it being nearly 300 times more potent at radiative forcing than CO2. Therefore, the ‘NOCA’ project aims to establish the first circumarctic N2O budget. Following intensive N2O flux sampling campaigns at primary sites within Northern Russia and soil N2O concentration measurements from secondary sites across the Arctic, we are now entering the phase of spatial extrapolation. Challenges to overcome are the small-scale heterogeneity of the landscape and incorporating small features that can function as N2O hotspots. Therefore, as a first step in upscaling the N2O fluxes, high resolution imagery is needed. We show here novel high-resolution 3D imagery from an unmanned aerial vehicle (UAV), which will be used to upscale N2O fluxes from plot to landscape scale by linking ground-truth N2O measurements to vegetation maps. This approach will first be applied to the East cliff of Kurungnakh Island in the Lena River Delta of North Siberia and is based on 2019 sampling campaign data. Kurungnakh Island is characterized by ice- and organic-rich Yedoma permafrost that is thawed by fluvial thermo-erosion forming retrogressive thaw slumps in various stages of activity. Overall, 20 sites were sampled along the cliff and inland, covering the significant topographic and vegetative characteristics of the landscape. The data from this scale will provide the basis for extrapolating, by using a stepwise upscaling approach, to the regional and finally circumarctic scale, allowing a first rough estimate of the current climate impact of N2O emissions from permafrost affected soils. Available international circumarctic data from this and past projects will be synthesized with an Arctic N2O database under development for use in future ecosystem and process-based climate model simulations.   
Massive Parallelization of the Global Hydrological Model mHM
Authors: Kaluza Maren , Samaniego Luis , Thober Stephan , Schweppe Robert , Kumar Rohini , Rakovec Oldrich
Published: March 2020

Parameter estimation of a global-scale, high-resolution hydrological model requires a powerful supercomputer and an optimized parallelization
algorithm. Improving the efficiency of such an implementation is essential to advance hydrological science and to minimize the uncertainty of
the major hydrologic fluxes and storages at continental and global scales. Within the ESM project [1], the main transfer-function parameters of the mHM
model will be estimated by jointly assimilating evapotranspiration (ET) from FLUXNET, the TWS anomaly from GRACE (NASA) and streamflow time series
from 5500 GRDC gauges to achieve this goal.

For the parallelization of the objective functions, a hybrid MPI-OpenMP scheme is implemented. While the parallelization
into equally sized subdomains for cell-wise computations  of fluxes (e.g., ET, TWS) is trivial,
cell-to-cell fluxes need to be computed for streamflow routing. For time series
datasets, the advanced parallelization algorithm MPI parallelized Decomposition of Forest (MDF) will be used. 

In this study, we go beyond the standard approach which decomposes the river into tributaries (e.g. the Pfaffenstetter System
[2]). We apply a non-trivial graph algorithm to decompose each river-network into a tree data structure with nodes representing
subbasin domains of almost equal size [3]. 

We analyze several aspects affecting the MDF parallelization: 
(1) the communication time between nodes; (2) buffering data before sending; (3) optimizing total node idle time and total run time; (4) memory
imbalance between master processes and other processes. 

We run the mHM model on the high-performance JUWELS supercomputer at Jülich Supercomputing Center (JSC) where the (routing) code efficiently scales up to ~180 nodes with 96 CPUs each. We discuss different parallelization aspects, 
including the effect of parameters onto the scaling of MDF and we show the benefits of MDF over a non-parallelized routing module.

[1] https://www.esm-project.net/
[2] http://proceedings.esri.com/library/userconf/proc01/professional/papers/pap1008/p1008.htm
[3] https://meetingorganizer.copernicus.org/EGU2019/EGU2019-8129-1.pdf
Error Analysis for the Himawari-8 Aerosol Optical Depth Basing on Parts of Aerosol Model and Sun Position over Wuhan, Central China
Authors: Ma Yingying , Zhang Ming , Shi Yifan , Gong Wei , Jin Shikuan
Published: March 2020

Aerosols attract great attention as having critical influence on the Earth’s energy budget and human health. Geostationary satellites like Himawari-8 process advantages on temporal resolution that allows rapidly changing weather phenomena tracking and aerosol monitoring. This work aims at providing a novel error analysis for the Advanced Himawari Imager (AHI) aerosol optical depth (AOD) retrieval from the aspect of aerosol model and sun position combing with the high quality ground-based observation in Wuhan, central China. Three-year co-located AOD dataset from AHI and sun-photometer are used. AHI underestimates AOD in all the seasons. Aerosol size distributions and phase functions are discussed as parts of aerosol model to explain the underestimation of AOD. AHI sets a low fine-mode particle median radius comparing with the in-site measurement in Wuhan that increases backscattering, and finally leads to the underestimation of AOD. Sun position also affects AHI AOD retrieval, and we use solar zenith angle (SZA) and scattering angle to represent sun position. Geostationary satellites get fixed satellite position for one site that provides convenience to the discussion. SZA influences AOD retrieval mainly through the length of transfer path and higher percent of samples within expected error often appears at low SZAs. Scattering angle also has obvious influence on AOD retrieval through the simulation of phase function and causes the difference of correlation performance between AHI and sun-photometer in aspect of SZA in morning and afternoon. Finally, we applied the dark target method to retrieve AHI AOD. The comparison of AODs reveals that the retrieval method of AHI performs better in Wuhan. The better performance of AHI AOD may be due to high aerosol loading and lack of enough prior information of aerosol properties in Wuhan. Our work could also be performed on other areas or other geostationary satellites, and help us to further understand the controlling factors that affect AOD retrieval accuracy, then contribute to better AOD retrieval.
Quantifying asset and visitor risk at Mt. Taranaki, New Zealand from multiple volcanic hazards
Authors: Procter Jonathan , Mead Stuart , Bebbington Mark
Published: March 2020

We present a probabilistic quantification of multiple volcanic hazards in an assessment of risk to visitors and assets in Egmont National Park, New Zealand. The probability of impact to proposed park infrastructure from volcanic activity (originating from Mt. Taranaki) is quantified using a combination of statistical and numerical techniques. While single (volcanic) hazard assessments typically follow a methodology where the hazard source (e.g. pyroclastic flow, ashfall, debris avalanche) is the focus and defines an area of impact, our multi-volcanic hazard assessment uses a location-centred methodology where critical locations are used to define the range of hazard sources that affect risk over park asset lifetimes. Key to this process is creating fast (i.e. linear/functional) mappings between hazard source parameters such as volume and impact parameters such as depth. These mappings can then be combined with stochastic models to find the probability of input parameters and the probability of eruptions generating these input parameters. For some hazards, such as ash fall, statistical models are available to map intensity to probability. However, mass flow hazards required the use of Gaussian process emulation to develop a computationally cheap surrogate to numerical simulations that can be efficiently sampled for probabilistic hazard assessment. This was a suitable alternative when statistical models for the hazard are unavailable. Our study demonstrates the use of these techniques to integrate stochastic and deterministic models for probabilistic volcano multi-hazard assessment.
Acknowledging technological and cultural evolutions to communicate seismic information to the public.
Authors: Fallou Laure , Landès Matthieu , Roch Julien , Roussel Frédéric , Steed Robert , Julien-Laffériere Sylvain , Bossu Rémy
Published: March 2020

Over the past decade technologies and social media have been praised a revolution in the way seismic risk and information was communicated to the public. For instance, LastQuake system is crowdsourcing earthquake detections and providing timely information and safety tips to citizens through social media and a free app now used by over 900K users over the world. Through a series of other practical examples and case studies, among which Earthquake Network system and Raspberry Shakes use, we show that smartphones and social media along with other technologies have indeed shaped new ways to detect earthquakes. They also enable to collect key information in order to raise situational awareness and in the end, inform the public in a timely and geotargeted manner, passing from a top-down approach to a two-way communication. Technology use also led to a significant increase of citizens’ role and implication in seismology, not only raising their interest for the risk but also for the science that relies beneath it.

Our analysis demonstrates that in order to be successful, and thus to reduce anxiety and create a trust relationship between scientists and citizens, efficient communication strategies must be based on a thorough knowledge of both risk culture and technological culture. Indeed, such assessment of the audience enables to better meet public’s various information needs in terms of content, format and time frame.

However, technologies as well as their uses have kept evolving and seismologists are now facing new challenges to communicate key information. For instance, in an increasing number of cases, misinformation and rumours about earthquake predictions become viral on social media. This is a critical issue to be addressed, especially in a context of development of both earthquake early warning systems and earthquake operational forecast. Additionally, citizen communication and information routines are evolving, especially with the rise of messaging apps or the development of new social media. However, to date, messaging apps are not designed in a way that facilitates communication of critical seismic information by seismic institutions.

We conclude that lessons learned from previous challenges, especially through a constant return of experience process, will be useful to address contemporary ones. Communicating towards the public is a necessity during all phases of the crisis cycle, from a scientific and risk perspective. Getting to know the audience’s needs, habits, language, emotions or cultural background and show them empathy is a critical part of efficient communication strategies. Finally, technologies should be seized as an opportunity to engage with citizens and build a lasting trust relationship.
Quantifying microbial growth and carbon use efficiency in dry soil environments via 18O water vapor equilibration
Authors: Canarini Alberto , Wanek Wolfgang , Watzka Margarete , Sandén Taru , Spiegel Heide , Imminger Stefanie , Woebken Dagmar , Šantrůček Jiří , Schnecker Jörg
Published: March 2020

As the global hydrological cycle intensifies with future warming, more severe droughts will alter the terrestrial biogeochemical carbon (C) cycle. As soil microbial physiology controls the large fluxes of C from soil to the atmosphere, improving our ability to accurately quantify microbial physiological parameters in soil is essential. However, currently available methods to determine microbial C metabolism in soil require the addition of water, which makes it practically impossible to measure microbial physiology in dry soil samples without stimulating microbial growth and respiration (namely, the “Birch effect”).

We developed a new method based on in vivo 18O water vapor equilibration to minimize soil re-wetting effects. This method allows the isotopic labelling of soil water without any liquid water or dissolved substrate addition to the sample. This was compared to the main current method (18O-water application method) in soil samples either at near-optimal water holding capacity or in air dry soils. We generated time curves of the isotopic equilibration between liquid soil water and water vapor and calculated the average atom percent 18O excess over incubation time, which is necessary to calculate microbial growth rates. We tested isotopic equilibration patterns in nine different soils (natural and artificially constructed ones) covering a wide range of soil texture and organic matter content. We then measured microbial growth, respiration and carbon use efficiency in three natural soils (either dry or at near-optimal water holding capacity). The proposed 18O vapor equilibration method provides similar results as the currently widely used method of liquid 18O water addition to determine microbial growth when used a near-optimal water holding capacity. However, when applied to dry soils the liquid 18O water addition method overestimated growth by up to 250%, respiration by up to 500%, and underestimated carbon use efficiency by up to 40%.

Finally, we applied the new method to undisturbed biocrust samples, at field water content (1-3%), and show for the first time real microbial growth rates and CUE values in such arid ecosystems. We describe new insights into biogeochemical cycling of C that the new method can help uncover and consider the wide range of questions regarding microbial physiology and its response to global change that can now be proposed and addressed.
Transient nature of riverbank filtered drinking water supply systems - a new challenge of natural radioactivity assessment
Authors: Csondor Katalin , Baják Petra , Izsák Bálint , Vargha Márta , Surbeck Heinz , Horváth Ákos , Erőss Anita
Published: March 2020

In Hungary the drinking water supply is mainly based on groundwater from aquifers characterized by different lithology. Riverbank filtered systems represent 40 % of drinking water supply. According to the EURATOM drinking water directive, there are recent regulations in Hungary regarding the natural radioactivity of drinking waters. Based on this, if gross alpha or gross beta radiation exceeds the limit, nuclide-specific measurements are required to be performed by the relevant waterworks. Since the mobility of uranium and radium is strongly influenced by the geochemical conditions, knowledge on the geochemical parameters of water is required. Therefore hydrogeology has a crucial role in revealing the origin of elevated activity concentrations. This research presents a case study in Hungary where the drinking water supply is provided by bank filtered and karst wells. The main aim of this study is to determine which radionuclides may cause the elevated radioactivity and explain their occurrence using hydrogeological approach, considering also the temporal variation of groundwater/surface water ratio. In most of the wells of the research area the gross alpha values are above the screening level, 0.1 Bq L-1. The study revealed the correlation between the river water level fluctuation and the uranium content of the wells. Among the investigated radionuclides, the uranium activity concentrations responded the most to the water level changes of the river and showed systematically higher values during low water conditions. In addition the karst wells showed low activity concentrations. This suggests, that uranium is transported by the groundwater component, and possibly sourced from the fluviatile sediments. The results of this study highlighted the transient nature of river bank filtered systems, which should be taken into account in the monitoring and water supply strategy. Nevertheless, the study emphasizes the importance of considering the dynamics of groundwater and associated geochemical environment in addition to geological factors, when investigating the radioactivity of groundwater or other potential contaminants.

This study was supported by the ÚNKP-19-3 New National Excellence Program of the Ministry of Human Capacities. This study is part of a project that has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 810980.
Quantifying and mapping citrate exudation in soil-grown root systems
Authors: Tiziani Raphael , Puschenreiter Markus , Smolders Erik , Mimmo Tanja , Herrera José Carlos , Cesco Stefano , Santner Jakob
Published: March 2020

The determination of citrate exuded from soil-grown roots is very challenging due to its rapid microbial degradation and mineralization, sorption to the solid soil phase and ongoing release of organic molecules from organic matter breakdown. For this reason, our knowledge about citrate release is mainly based on experiments carried out in hydroponics. Results obtained in hydroponics cannot directly be transferred to soil-plant systems, as hydroponics represents an artificial environment. This study aimed to develop a localization and quantification technique for citrate exuded from soil-grown plant roots, based on diffusive gradients in thin film (DGT). Polyacrylamide gels containing precipitated zirconium hydroxide (ZrOH) were applied to the rhizosphere of soil grown plants, on which citrate is efficiently immobilized, thereby creating a zero sink to sample the citrate exuded from the roots. Citrate was eluted with 1 mL 0.5 mol L-1 NaOH from the ZrOH gel and quantified by ion chromatography. ZrOH gel discs were able to bind the citrate contained in 10 mL of 2.77 mg citrate L-1 solutions within a 4h uptake period. Elution efficiency was ~89%. ZrOH gel capacity at pH 8 was 200 µg per gel disc and 299 µg per gel disc at pH 4, which is sufficient to act as a zero sink for citrate released from plant roots. As a first exemplary method application, we grew white lupin plants in rhizotrons using a highly phosphorus deficient soil. ZrOH gel sheets were applied for 26 h onto cluster roots for citrate sampling following established DGT protocols. Gels were cut afterwards into 5×5 and 5×2 mm slices for obtaining a citrate exudation map. In both cases we were able to localize and quantify up to 7.89 µg citrate on individual gel slices, as well as to identify longitudinal and lateral citrate gradients around the cluster roots. Moreover, the characterization of ZrOH gels showed its suitability for citrate sampling in terms uptake kinetics and capacity. These results demonstrate that the developed method is suitable for citrate sampling and localization in a non-destructive way from soil-grown plant roots. As it is applicable to soil grown-roots and provides unprecedented spatial resolution, this sampling technique advances the experimental possibilities for researching root exudates considerably. Using suitable binding materials, this approach is also applicable to other carboxylates such as malate or oxalate and other compound classes such as phenolics, flavonolos etc. Furthermore, this technique can be combined with complementary imaging methods for mapping e.g. nutrients, contaminants, pH or enzyme activity distributions.
Extracting the properties of Earth and atmospheric tidal harmonics from groundwater level records: a least-squares approach
Authors: Schweizer Daniel , Ried Vincent , Rau Gabriel , Tuck Jonathan , Stoica Peter , Blum Philipp
Published: March 2020

Groundwater resources are under increasing threat from human activity and climate change, making sustainable management critical. However, appropriate management generally requires extensive knowledge of the properties and characteristics of aquifers. In recent years, research into passive investigation methods utilising the impact of Earth and atmospheric tides (EAT) on the groundwater response have gained momentum. EAT occur at known frequencies of daily and sub-daily cycles per day (cpd) and present an inexpensive and viable opportunity for the characterization of groundwater systems at an unprecedented spatial and temporal resolution (McMillan et al., 2019). However, quantifying aquifer properties relies on accurate and reliable extraction of the harmonic properties (amplitude and phase) of tidal components embedded in groundwater level and atmospheric pressure records that are dominated by larger magnitude variations as well as other noise. Here, we use synthetic signals and real measurements to test and compare the performance of the Discrete Fourier Transform (DFT) with a generalised harmonic least squares amplitude and phase estimation (APES) approach for the harmonic tidal components. APES was implemented in Python in conjunction with a windowed de-trending function that serves as a high pass filter. The analysis focuses on three realistic aspects often encountered in groundwater monitoring: (1) the minimum record length required to reliably separate tidal components at nearby frequencies, (2) signal quantisation as a proxy for measurement resolution, and (3) the amount of sampling gaps or irregularly spaced sampling. Results indicate that APES outperforms DFT in quantifying the amplitude of the major tidal components M2 (1.93227 cpd) and S2 (2.0 cpd) on regularly sampled data, because it is not subject to spectral leakage. Furthermore, APES is superior in handling data gaps, missing values and outliers, yielding accurate amplitude estimates even for comparably small amounts of data and without requiring pre-processing such as data interpolation or resampling. This increases the data volume for the tidal analysis considerably and enables a much more extensive use of tidal analysis. Further investigation will focus on the methods’ performance in quantifying the phase of the M2 and S2 components.

 

McMillan, T. C., Rau, G. C., Timms, W. A., & Andersen, M. S. ( 2019). Utilizing the impact of Earth and atmospheric tides on groundwater systems: A review reveals the future potential. Reviews of Geophysics, 57, 281– 315. https://doi.org/10.1029/2018RG000630.
First estimate of NO2 in the upper troposphere from TROPOMI
Authors: Marais Eloise , Joiner Joanna , Choi Sungyeon
Published: March 2020

Nitrogen oxides (NO x = NO + NO2) in the upper troposphere (~10-12 km) are effective at producing ozone in the upper troposphere where ozone is a potent greenhouse gas. Observations of NOx in the upper troposphere are limited in time to a few intensive research aircraft campaigns and in space to commercial aircraft campaigns. There are satellite-derived observations of NO2 in the upper troposphere from the Ozone Monitoring Instrument (OMI), but these are at very coarse resolutions (seasonal, > 2,000 km). The high-resolution Sentinel-5P/TROPOMI instrument offers higher spatial resolution and better cloud-resolving capability than OMI. Here we use synthetic columns of NO2 from the GEOS-Chem chemical transport model to assess feasibility of deriving NO2 in the upper troposphere using partial columns of NO2 above cloudy scenes (the so-called cloud-slicing technique). The model is also used to quantify errors induced by uncertainties in cloud-top height and to determine whether NO2 over cloudy scenes is representative of all-sky conditions (the "truth"). We find that the cloud-slicing approach is spatially consistent (R =0.5) with the "truth", but with a small (10 pptv) bias in background NO2. Cloud-slicing is then applied to TROPOMI total columns of NO2 to derive near-global observations of NO2 in the upper troposphere and assessed against the existing OMI products and aircraft observations from NASA DC8 aircraft campaigns.
Investigating the sensitivity of the onset and withdrawal of the south Asian summer monsoon system to changes in anthropogenic emissions using a climate model
Authors: Mishra Shiwansha , Ganguly Dilip , Sharma Puneet
Published: March 2020

While the monsoon onset is recognized as a rapid, substantial, and sustained increase in rainfall over large parts of south Asia, the withdrawal marks the return to dry conditions. Normally, the south Asian summer monsoon onset occurs around 1st June over extreme south of peninsular India, which gradually advances to extreme northwest of India by around 15th July. The withdrawal starts from northwest India from around 1st September and from extreme south peninsular India by around 30th September. The determinations of the onset and withdrawal dates of monsoon have great economic significance for this region as they influence many agriculture and water resource management decisions in one of the most highly populated regions of the world. Several studies involving global model simulations have shown that changing aerosol emissions could result in significant changes in the seasonal mean precipitation distribution over India. A few studies also show that presence of absorbing aerosols in the foothills of Himalayas and over the Tibetan plateau could increase the moisture convergence over India thereby causing an advancement and intensification of the monsoon precipitation. However, most of the previous studies, which investigated the impact of anthropogenic emissions on the monsoon, are limited to understanding the impact of various emission changes on the seasonal mean monsoon characteristics. In the present study, we try to understand the sensitivity of the onset and withdrawal period of the south Asian summer monsoon system to changes in anthropogenic emissions using a climate model (CESM1.2). We diagnose the onset and withdrawal of the south Asian monsoon by analyzing the variability in vertically integrated moisture transport (VIMT) over the south Asian region and following the definition of hydrologic onset and withdrawal index (HOWI) defined by Fasullo et al. (2002). We examined the effect of changing emissions anthropogenic aerosol, greenhouse gases and both on the onset and withdrawal of the south Asian summer monsoon system. Our preliminary results suggest that increases in the emissions of aerosols and greenhouse gases from anthropogenic sources from pre-industrial to present day could possibly result in significant delay in the onset and advancement in withdrawal of the south Asian summer monsoon system thereby shortening the length of the monsoon season. More results with greater detail will be presented.
The southern North Sea as a natural palaeo-laboratory to reconstruct the coastal response to Last Interglacial sea-level rise
Authors: Barlow Natasha , Cartelle Victor , Pollard Oliver , Gregoire Lauren , Gomez Natalya , Hodgson David , Eaton Stephen , Busschers Freek , Cohen Kim , Cotterill Carol , Mellett Claire , Haigh Ivan
Published: March 2020

Current models that project sea-level rise beyond 2100 have large uncertainties because recent observation encompass a too limited range of climate variability to provide robust tests against which to simulate future changes. It is crucial to turn to the geological record where there are large-scale changes in climate, but the current interglacial provides limited evidence for how the Earth-system responds to increased temperatures, and therefore it is necessary to study previous climatically-warm periods. Global temperatures during the Last Interglacial were ~1oC warmer than pre-industrial values and 3-5oC warmer at polar latitudes, during which time global mean sea level was likely 6-9 m above present. Though the drivers of warming during the Last Interglacial are different to those of today, it is the amplified warming at polar latitudes, the primary locations of the terrestrial ice masses likely to contribute to long term sea-level rise, which makes the Last Interglacial an ideal palaeo-laboratory to understand coastal response to sea-level rise.  However, our understanding of Last Interglacial sea level change is primarily limited to tropical and sub-tropical latitudes and it is important to understand the response of temperate estuarine settings to rising sea level.

The ERC-funded RISeR project (Rates of Interglacial Sea-level Change, and Responses) focuses on specifically targeting palaeo shorelines buried within the southern North Sea, preserved beyond the limit of the Last Glacial Maximum ice sheets. Buried Last Interglacial sequences in this area provide a valuable record of marine transgression and are being unveiled in new geophysical and geotechnical datasets acquired to support the offshore renewable energy development. This offshore sedimentary archives offer significant advantages over the geomorphologically restricted onshore records allowing us to trace the transgression over a much large area, and should capture the earliest flooding of the Last Interglacial North Sea basin, when the far-field data suggests ice sheet melt was at it maximum. By integrating the already available datasets with newly acquired samples as part of the project, we aim to develop new palaeoenvironmental reconstructions of the Last Interglacial sea-level change from northwest Europe, providing the first chronological constraints on timing, and therefore rates. This has the potential to allow us to ‘fingerprint’ the source of melt (Greenland and/or Antarctica) during the interglacial sea-level highstand.
Initial in-flight performance results from Solar Orbiter RPW/BIAS
Authors: Khotyaintsev Yuri V. , Vaivads Andris , Graham Daniel B. , Edberg Niklas J. T. , Johansson Erik P. G. , Maksimovic Milan , Bale Stuart D. , Chust Thomas , Kretzschmar Matthieu , Soucek Jan
Published: March 2020

The BIAS subsystem is a part of the Radio and Plasma Waves (RPW) instrument on the ESA Solar Orbiter mission. It allows sending bias current to each of the three RPW antennas. By setting the appropriate bias current the antenna potential can be shifted closer to the local plasma potential. This allows us to measure the floating potential of the spacecraft, as well as the electric field in the DC/LF frequency range with higher accuracy and lower noise level. Here we present the very initial results on RPW/BIAS in-flight performance based on the operations during the instrument commissioning.
Temporal Dynamics of Streamflow Using Complex Networks
Authors: Sivakumar Bellie
Published: March 2020

Modeling the dynamics of streamflow continues to be highly challenging. The present study proposes a new approach to study the temporal dynamics of streamflow. The approach couples the concepts of complex networks and chaos theory. Applications of the concepts of complex networks for studying streamflow dynamics have been gaining momentum in recent years. A key step in such applications is the construction of the network – a network is a set of points (nodes) connected by lines (links). The present study uses the concept of phase-space reconstruction, an essential first step in chaos theory-based methods, for network construction to study the temporal dynamics of streamflow. The phase-space reconstruction involves representation of a single-variable time series in a multi-dimensional phase space using delay embedding. The reconstructed phase space is treated as a network, with the reconstructed vectors (rather than the original time series) serving as the nodes and the connections between them serving as the links. With this network construction, the clustering coefficient of the individual nodes and the entire network is calculated to assess the node and network strengths. The approach is employed to a large number of streamflow time series observed in the United States. The results indicate the usefulness and effectiveness of the phase-space reconstruction-based approach for network construction. The implications of the outcomes for identification of the appropriate type and complexity of model as well as for classification of catchments are discussed.
Long term observation of crustal deformation in NE-Italy
Authors: Braitenberg Carla , Grillo Barbara , Pastorutti Alberto , Pivetta Tommaso
Published: March 2020

The long term monitoring of crustal deformation in NE-Italy derives from tilt and strainmeter observations since 1960. The stations have been maintained by three generations of scientists starting with the geodesist Antonio Marussi, keeping the instrumentation active and up to date. The decade-long time series have given observations of rare events, as the free oscillations recorded by the largest earthquakes ever recorded (Chile 1960, Sumatra 2004, Tohoku 2011) and climatic extreme events leading to extremely intense rainfalls that generate underground flooding and surface deformation (Braitenberg et al., 2019; Braitenberg, 2018). The stations have the characteristic of being representative of geodetic monitoring in karst geologic formation, that they are placed in a seismically active area which has experienced a magnitude M 6.4 earthquake in the past (1976 Gemona), and that they are influenced by the ocean loading deformation of the Adriatic Sea. The seismic area implies that the strain accumulation is an ongoing process, presently activating the elastic energy of the next earthquake. We show some relevant observations, which could hardly have been caught without such a long time series. Between 1973 and 1976 the long base horizontal pendulums of the Grotta Gigante cave gave episodic disturbances, that seized 6 months after the Gemona main shock. The hydrology of the karst is made of an underground channel system that is completely flooded during extreme rainfall and is pressurized close to simultaneously over a distance of 30 km, leading to an observable uplift and deformation of the surface (Braitenberg et al., 2019). It has been possible to extract and model this type of deformation.

The tilt and strainmeters have high accuracies and precision in the detection of crustal deformation, with the drawback to be point measurements. InSAR acquisitions cover thousands of points on the surface, but with coarser accuracy. One major problem is in the correction of atmospheric effects in the InSAR signal, which produces apparent movement in the direction of Line of Sight, uncorrelated to the real soil movement. Our present research objective is the transfer of knowledge from the signals known in the tilt and strainmeter observations to the detection of these signals with InSAR. 

 

Braitenberg C. (2018). The deforming and rotating Earth - A review of the 18th International Symposium on Geodynamics and Earth Tide, Trieste 2016 , Geodesy and Geodynamics, 187-196, doi::10.1016/j.geog.2018.03.003 .

Braitenberg C., Pivetta T., Barbolla D. F., Gabrovsek F., Devoti R., Nagy I. (2019). Terrain uplift due to natural hydrologic overpressure in karstic conduits. Scientific Reports, 9:3934, 1-10, doi.:10.1038/s41598-019-38814-1.
The pre-Mesozoic basement underneath the Jura Mountains fold-and-thrust belt: an overview from models and maps
Authors: Schori Marc , Sommaruga Anna , Mosar Jon
Published: March 2020

The Jura Mountains are a thin-skinned fold-and-thrust belt (FTB) in the northern foreland of the European Alps, extending over northern and western Switzerland and eastern France. The Jura FTB was detached in Triassic evaporites during Late Miocene and Pliocene compression. Prior to this, the pre-Mesozoic basement was intensely pre-structured by inherited faults that had been reactivated under changing stress fields during the Mesozoic and Cenozoic structural evolution of continental Europe. In order to understand the connection between thin-skinned FTB formation and pre-existing basement structures, we compiled boreholes and geological cross-sections across the Northern Alpine Foreland and derived elevation, thickness and erosion models of defined Mesozoic units and the top of the pre-Mesozoic basement.

Our models confirm the presence of basement faults concealed underneath the detached cover of the Jura Mountains. The pre-Mesozoic basement shows differences in structural altitudes resulting from partially overlapping lithospheric processes. They include graben formation during evolution of the European Cenozoic Rift System (ECRIS), flexural subsidence during Alpine forebulge development and lithospheric long-wavelength buckle folding. Faults in connection with these processes follow structural trends that suggest the reactivation of inherited Variscan and post-Variscan fault systems. We discuss the spatio-temporal imprint of lithospheric signatures on the pre-Mesozoic basement and their consequence on the formation of the Jura Mountains FTB. Untangling structures within the pre-Mesozoic basement leads us to a modern understanding of the long-term evolution of the detached Mesozoic cover. Furthermore, it allows us to improve the prediction of ages that are potentially preserved within the Mesozoic cover of the Jura FTB.
Jura glacial lakes: a paleoclimatic and paleoenvironmental evolution since the Late Glacial Period.
Authors: Bomou Brahimsamba , Zappa Damien , Rachoud-Schneider Anne-Marie , Haas Jean-Nicolas , Gärtner Marina , Spangenberg Jorge , Bichet Vincent , Adatte Thierry
Published: March 2020

During the retreat of a Würm ice sheet, numerous glacial paleolakes took place in the Swiss and French Jura. Two sites were investigated: the Amburnex Valley site (Switzerland), which evolved in well-developed peatland and the Lake Val (France), which is still persisted as a lacustrine system. During the Late Glacial period, both sites were glacial lakes characterized by a significant accumulation of lacustrine sediments.

Using a multiproxy approach, this project aims to reconstruct the paleoclimatic and the paleoenvironmental evolution recorded in lacustrine sediments and peatbog deposits since the last 13’000 years.

The Amburnex core (7m) exhibit a basal morainic deposit from the Würm period, overlain by three meters of lacustrine deposits and four meters of peatland deposits. The Lake Val core (4.5m) consists of the same lithological succession.

A multiproxy approach based on palynological analyses, grain-size analyses, mineralogical analyses (XRD) and geochemical analyses (TOC, Nitrogen, Phosphorus and Mercury contents; major and trace elements; organic carbon isotopes) have been used to characterize the hydrological and climatic fluctuations, the trophic level and the origin of organic matter in order to reconstruct the paleoenvironmental and paleoclimatic evolution of this area.

In the Amburnex site, the Bølling-Allerød, the Younger Dryas and the beginning of the Preboreal period have been recognized by palynological analyses and confirmed by carbon 14 dating. During the Oldest Dryas, oligotrophic conditions took place as suggested by the very low concentrations in nitrogen and organic matter. Then, during the warmer Bølling period, an enrichment in total organic carbon (TOC) associated with a decrease in phosphorus content are observed, implying the development of eutrophic conditions and maybe phosphorus recycling. Later in the Allerød period, low TOC and phosphorus contents, associated with varved carbonate deposits, indicate a return to more oligotrophic conditions. New organic matter enrichments are observed in the interval corresponding to the colder Younger Dryas period. These trends are quite consistent with those observed in the Lake Val and reflect significant changes in runoff and nutrient inputs at least at regional scale.
Advancing intersatellite laser interferometry for geodesy applications
Authors: Koch Alexander , Heinzel Gerhard , Wanner Alexander , Ertmer Wolfgang
Published: March 2020

In the summer of 2019 the Deutsches Zentrum für Luft- und Raumfahrt (German Aerospace Center) Institute for Satellite Geodesy and Inertial Sensing (DLR-SI) was founded. This new institute is located in Hannover with one group in Bremen. It benefits from strong ties to different institutes from the Leibniz University in Hannover (Institute for Quantum Optics, Institute of Geodesy, Institute for Gravitational Physics), the Center of Applied Space Technology and Microgravity (ZARM) in Bremen and the National Metrology Institute (PTB) in Brunswick.

In this talk I will give an overview of the focus of the working group for Laser Interferometric Sensing. The overarching goal of our group is the technology development for laser interferometric satellite geodesy missions, like a possible Next Generation Gravity Mission (NGGM). Due to the technological overlap, collaboration with the LISA community is also possible. Specifically, the currently planned work packages include, but are not limited to the development of novel optical bench topologies for laser interferometric ranging instruments for geodesy missions and the design of low noise photoreceivers and laser link acquisition sensors. Furthermore, interferometric readout of monolithic accelerometers will be studied and flight data from the GRACE Follow-On Laser Ranging Interferometer (LRI) will be evaluated within our group. In my talk I will give an overview of these planned work packages and will point out the expected benefit of these novel technologies to the geodesy community.