bluuebunny/crossref_metadata_2025 huggingface dataset:
Bed-character dependent microseismicity clustering at Rutford Ice Stream, West Antarctica
Authors: Kufner Sofia-Katerina , Brisbourne Alex , Smith Andy , Anandakrishnan Sridhar , Murray Tavi , Schlegel Rebecca , Nicholls Keith , Hodgson Dominic , Kendall Michael , Lee Ian
Published: March 2020

Microseismicity, induced by the sliding of a glacier over its bed and through bed deformation, can be used to characterize frictional properties of the ice-bed interface. Together with ice column deformation, these characteristics form the key parameters controlling ice stream flow. Here, we use naturally occuring seismicity to monitor temporal and spatial changes in bed properties at Rutford Ice Stream (RIS), West Antarctica, in order to characterize ongoing basal deformation and sliding. RIS is a significant contributor to the outflow of ice from West Antarctica, with speeds of ~1.1 m/day. Past geological and geophysical surveys, including drilling into the bed itself, have revealed pronounced bed topography and a sharp change in bed character along flow direction from presumably soft deformable to stiffer sediments. These complementary data as well as Rutford’s flow characteristics allow us to interpret the seismic data in their geological context.

Our data consist of three months of seismic recordings from a 35-station seismic network located ~40 km upstream the grounding line of RIS, being collected in the framework of the BEAMISH project during the 2018/19 field season. An event catalogue derived using the QuakeMigrate and Nonlinloc software packages reveals an active seismic environment (~40,000 events in three months) with locally clustered microseismicity. Microseismicity occurs near the ice-bed interface and is concentrated in the transition region between presumed-soft and presumed-hard sediments. Within the more compacted sediments further seismicity occurs, predominantly along topographic lows, which form elongated, flow parallel sub-glacial valleys. Within the regions of activity, seismicity tends to cluster in focused spots of particular high activity. Repeated basal seismicity at spatially restricted locations has been observed before and was interpreted as being caused by ‘sticky spots’ within a more ductile deforming matrix. Our results, showing a close alignment of these sticky spots along structural and topographic boundaries, may indicate that such features form major obstacles for basal glacial sliding. In addition to these spatial variations, the average event frequency varies over time. We estimate an ~15 day periodicity to the activity with as many as 1200 events/day during the active times and as few as ~100 events per day during the more-quiescent times. This roughly corresponds to the period of the spring-neap tidal cycle which has been shown to modulate the horizontal flow velocity of RIS. Time dependent variations in the frequency of microseismicity might suggest the glacial bed affected by these modulations.
Efficiency of the piecewise constant acceleration modeling - GOCE case study
Authors: Bobojć Andrzej
Published: March 2020

One of the valuable products of the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) mission is a centimeter-accuracy orbit of the GOCE satellite called the precise science orbit (PSO). This orbit, delivered by the European Space Agency (ESA), was the reference for the GOCE orbit modeling using the piecewise constant acceleration approach. Besides initial conditions, the piecewise constant accelerations (i.e. empirical accelerations) were estimated in the radial, along-track and cross-track direction, employing the dedicated package called Torun Orbit Processor (TOP). The TOP software is based on the classical least squares adjustment including the Cowell 8-th order numerical integration for an orbit prediction and the orbit improvement module, taking into account the gravity field model and the background models (BM) describing gravitational and non-gravitational perturbing forces. The positions of GOCE satellite on the reduced-dynamic PSO orbit were treated as observations in the orbit improvement process. A measure of the fit of estimated arcs and their accuracy was the RMS of the residuals between the estimated orbits and the corresponding reference ones. Different variants of the orbit estimation were obtained for the shorter  arcs (22.5, 45, 90 and 180 minutes)  and for the longer 1-day arcs. The solution variants were determined for different numbers of the estimated piecewise constant accelerations. Moreover, these numbers were different for the radial, along-track and cross-track direction. The obtained solutions depend on a kind of computational mode – with and without the BM models in the GOCE orbit modeling using the estimated piecewise constant accelerations. Additionally, for selected solutions, the distributions of the residuals in the aforementioned directions along the estimated arcs are presented. 
Spatiotemporal Evaluation of Remote Sensing Derived Soil Moisture Deficit for the Sugarcane Crop: A Case Study for the Indo-Gangetic Basin
Authors: Sure Anudeep , Dikshit Onkar
Published: March 2020

This study focuses on the estimation of soil moisture deficit from root zone soil moisture information derived from remotely sensed passive microwave surface soil moisture data for a period of fifteen years (2002 to 2016) for the Indo-Gangetic basin. The remote sensing datasets used to estimate soil moisture deficit are Advanced Microwave Scanning Radiometer for EOS (AMSR-E) and Advanced Microwave Scanning Radiometer - 2 (AMSR-2) by JAXA and NASA. As India is an agrarian country, it is one of the largest producers of sugarcane at the global level and hence, this is the test crop considered for this work. The Indo-Gangetic basin has numerous culturable command areas with dynamic meteorological patterns, soil type, land use and land cover, agricultural practices, water and crop management with different sources of irrigation. Rain-fed irrigation is the primary source of water for crop production in this basin. Sugarcane crop is characterised by specific root depth, crop water requirement, crop length and crop phenology. In India, meteorological parameters primarily, precipitation, temperature and evapotranspiration and the meteorological seasons define the agricultural season (irrigation to harvesting). Here, an interrelationship between soil moisture deficit (at varying depth) and meteorological parameters, precipitation based meteorological indices (Rainfall Anomaly Index, Standardized Precipitation Index and Effective Drought Index), ground-based crop indices (crop yield index, crop area index and crop production index) is analysed at the annual and seasonal scale. The study indicates the paramount effect of the aforementioned factors on soil moisture deficit variable. The temporal variation of soil moisture deficit being served as a proxy for crop water requirement and the model developed from the same provides vital information for an efficient irrigation scheduling, sustainable water resource management for increased crop production and developing crop insurance schemes and policies at the basin level.
High-resolution mapping of lake and floodplain topography from space
Authors: Fassoni-Andrade Alice César , Paiva Rodrigo Cauduro Dias de , Barbosa Claudio Clemente Faria , Novo Evlyn Marcia Leão de Moraes , Rudorff Conrado de Moraes , Fleischmann Ayan Santos
Published: March 2020

Terrain elevation data are essential for land management, navigation, and earth science applications. Digital elevation models (DEMs) can be created for land as well as underwater surfaces, and remote sensing advancements have led to the increase in the availability of a range of DEMs over the land. However, the generation of underwater DEMs usually requires the shorelines delineation of the water body, and in regions with many lakes, such approach have high processing costs. Currently, there is no systematic mapping of lakes and channels bathymetry of large and complex wetlands using remote sensing data.

We present here the first high-resolution topographic mapping (30 m) of the central Amazon floodplain (~1100 km extension of the Amazon River) using a new method based on water surface elevations and a flood-frequency map derived from Landsat images. Validation using field bathymetric surveys presented a Root Mean Square Error (RMSE) of 1.30 m in floodplain elevations and Pearson’s correlation coefficient of 0.73. These results indicate adequate spatial representation over a large complex floodplain geomorphology and important improvements relative to the SRTM (RMSE of 3.55 and Pearson’s coefficient of 0.22). The method can be applied to temporarily flooded regions, with the advantage of not requiring lake delimitation. Finally, this method provides synergism with the forthcoming satellite SWOT mission for advancements in hydrological, ecological and geomorphological studies of floodplain as the projected increase in availability of surface water elevation data will enhance its applicability and yield unprecedented opportunities to create new datasets of floodplain DEMs and lakes storage volumes.
Eco-hydrological soil carbon fluxes in established Nature-based solutions for soil protection
Authors: Gonzalez Ollauri Alejandro , Ma Jing
Published: March 2020

Nature-based solutions (NBS) for soil protection generally involve planting trees to provide effective soil reinforcement, stability and resilience over time. Atmospheric carbon accumulates in both plant and soil materials as the tree cover develops and establishes on a given NBS. However, the carbon stored in a given NBS is subjected to continue cycling as a result of decomposition and soil respiration processes, both linked to the soil’s water content. Consequently, carbon cycling rates within NBS could be regulated by the partition of rainfall into throughfall, dripfall and stemflow at the tree’s canopy. Yet, quantification of soil carbon fluxes related to eco-hydrological processes occurring at the plant-soil-atmosphere interface is rare and needs further investigation. As a result, a figure on the carbon footprint of NBS remains inaccurate. The aim of this study was to quantify soil carbon fluxes under changing meteorological conditions in a tree-vegetated embankment to ascertain the effect of rainfall partition at the tree’s canopy on carbon cycling. To this end, we investigated rainfall partitioning and soil carbon fluxes under six adult tree individuals of Populus nigra L., Dyospiros kaki Thunb., and Melia azedarach L. growing on an embankment in Xuzhou, China. The results showed that soil carbon fluxes were substantially higher on rainy days than on dry days. Nonetheless, we did not find convincing evidence suggesting that rainfall partition at the trees’ canopy contributed to the regulation of the soil carbon cycle. Herein, we discuss experimental limitations that should be addressed in future work to verify the eco-hydrological effect of vegetation on soil carbon fluxes in established NBS, as well as approaches for quantifying the carbon footprint of NBS.          

   
A subducted slab of the Paleo-Tethys oceanic lithosphere associated with the formation of the Emeishan large igneous province
Authors: He Chuansong
Published: March 2020

The formation of large igneous provinces is a focus of geoscientists and is a major scientific issue in mantle dynamics. A broad consensus holds that the Emeishan large igneous province (ELIP) was generated by an upwelling mantle plume. However, recent geological and seismic studies have challenged this notion. In this study, I redraw and reanalyze previous tomographic images and use images of three velocity perturbation profiles crossing the ELIP. I collected abundant high-quality teleseismic data and performed common conversion point (CCP) stacking of receiver functions in the mantle transition zone (MTZ) of the ELIP. The tomographic images show a high-velocity anomaly of a northeastward-subducted slab-like body beneath the ELIP, which might be a relic of the Paleo-Tethys oceanic lithosphere. Images from CCP stacking of receiver functions indicate that the subducted slab of the Paleo-Tethys oceanic lithosphere retained an imprint on the X-discontinuity and the 410 and 660 km discontinuities. Based on my assessment, the subducted slab might have induced return mantle flow or large-scale mantle upwelling, which possibly played an important role in the formation of the ELIP.
Risk analysis of the 2018 Sedongpu glacial debris flows in the southeastern Tibet
Authors: Hu Kaiheng , Zhang Xiaopeng , Tang Jinbo
Published: March 2020

Several high-magnitude glacial debris flows happened at Sedongpu, a tributary of Yarlung Tsangpo river in the southeastern Tibet in 2018. The hazards blocked the main river twice and inundated the road and bridge to Jiala village on the foot of Namche Barwa massif. The glacial dammed lake with an impounded water of 0.6 billion m3 broke out and caused an outburst flood of peak discharge ~ 30,000 m3/s on October 19. A comprehensive methodology was developed to assess the potential hazard of the glacial-debris-dammed lake before the outburst. Multi-temporal remote sensing image interpretation was used to obtain the frequency-magnitude relationship. The debris-flow deposition and dam height were estimated via numerical simulation of 2-D shallow water equations. Then, the impoundment area and potential inundation were analysed by GIS spatial analysis. We also test different hydrological empirical models of calculating the peak discharge of glacial-debris lake outburst floods. With regard to the Sedongpu event, the 1985 Costa’s model shows best agreement with the measured data.
Evaluation of two process-based models used to estimate global CH4 emissions from natural wetlands
Authors: Li Tingting
Published: March 2020

Reliable models are required to estimate global wetland CH4 emissions. This study aimed to test two process-based models, CH4MODwetland and TEM, against the CH4 flux measurements of marsh, swamps, peatland and coastal wetland sites across the world; specifically, model accuracy and generality were evaluated for different wetland types and in different continents, and then the global CH4 emissions from 2000 to 2010 were estimated. Both models showed similar high correlations with the observed seasonal CH4 emissions, and the regression of the observed versus computed total seasonal CH4 emissions resulted in R2 values of 0.78 and 0.72 by CH4MODwetland and TEM, respectively. The CH4MODwetland predicted more accurately in marsh, peatland and coastal wetlands, with model efficiency (EF) values of 0.22, 0.55 and 0.72, respectively; however, the model showed poor performance in swamps (EF<0). The TEM model predicted better in peatland and swamp, with EF values of 0.77 and 0.71, respectively, but it could not accurately simulate the marsh and coastal wetland (EF<0). There was a good correlation between the simulated CH4 fluxes and the observed values on most continents. However, CH4MODwetland showed no correlation with the observed values in South America and Africa. TEM showed no correlation with the observations in Europe. The global CH4 emissions for the period 2000­­–2010 were estimated to be 105.31±2.72 Tg yr-1 by CH4MODwetland and 134.31±0.84 Tg yr-1 by TEM. Both models simulated a similar spatial distribution of CH4 emissions across the world and among continents. Marsh contributes 36%–39% to global CH4 emissions. Lakes and rivers and swamp are the second and third contributors, respectively. Other wetland types account for only approximately 20% of global emissions. Based on the models’ generality, if we use the more accurate model to estimate each continent/wetland type, we obtain a new assessment of 116.99–124.74 Tg yr-1 for the global CH4 emissions for the period 2000–2010.
Assessing energetic flow structures responsible for bridge pier scour
Authors: Xu Yi , Valyrakis Manousos , Michalis Panagiotis
Published: March 2020

Scour has been recognized as one of the primary reasons for bridge pier destabilization. As extreme weather intensifies and hydraulic infrastructure such as bridge piers and abutments (many constructed since the Victorian era, for the case of the UK) continues to age, the challenge of scour-induced hazards will keep growing impacting the resilience of our society. Thus, there is an increasing value in studying the highly dynamical process of scour around hydraulic infrastructure. Maximum scour depth estimation has been broadly studied by researchers over the past decades, using phenomenological or empirical approaches, linking mean flow properties, bridge pier and riverbed materials characteristics [1, 2].

This study aims to get a better understanding of how the turbulent flow field modified by the bridge pier, interacts with the bed surface towards the generation of the scour hole. This is pursued by following a dynamical approach via assessing the flow structures that are sufficiently energetic [3] to remove bed material from the vicinity of the bridge pier.

A series of scour experiments with different lengthscale of model bridge piers is conducted in a water recirculating research flume. For each of these cases flow velocity profiles are collected downstream the bridge pier using high resolution acoustic Doppler velocimetry (ADV). Using the raw data collected near the bed surface and information for the bed surface material, the criterion of impulse [4] is used as a metric for assessing the extend and maximum scour depth. The results are compared for the different measurement locations are compared to better understand the process of scour downstream different model piers.

[1]. M Valyrakis, P Michalis, H Zhang, (2015). A new system for bridge scour monitoring and prediction, Proceedings of the 36th IAHR World Congress, 1-4.

[2]. Yagci, O., Celik, M. F., Kitsikoudis, V., Ozgur Kirca, V.S., Hodoglu, C., Valyrakis, M. , Duran, Z. and Kaya, S. (2016) Scour patterns around isolated vegetation elements. Advances in Water Resources, 97, pp. 251-265.(doi:10.1016/j.advwatres.2016.10.002)

[3]. Valyrakis, M. , Diplas, P. and Dancey, C.L. (2013) Entrainment of coarse particles in turbulent flows: an energy approach. Journal of Geophysical Research: Earth Surface, 118(1), pp. 42-53. (doi:10.1029/2012JF002354)

[4]. Valyrakis, M. , Diplas, P., Dancey, C.L., Greer, K. and Celik, A.O. (2010) Role of instantaneous force magnitude and duration on particle entrainment. Journal of Geophysical Research: Earth Surface, 115(F02006), 18p. (doi:10.1029/2008JF001247)
Monitoring African Bush Elephants with the OSOP Raspberry Shake and Boom
Authors: Lamb Oliver , Shore Michael , Lees Jonathan , Lee Stephen
Published: March 2020

In terms of terrestrial animal communication, elephants are especially noteworthy because they have been documented to produce some of the loudest sounds at frequencies between 10-35 Hz. Their vocalisations, or ‘rumbles’, with fundamental frequencies in the infrasonic range (≤ 20 Hz) can have amplitudes as high as 117 dB. Here we present our efforts to evaluate the performance of the Raspberry Shake and Boom, a low-cost seismic and acoustic sensor, for identifying and monitoring the movements of African Bush Elephants (Loxodonta africana). The test area was the Adventures with Elephants elephant reserve in South Africa which includes a herd of 7 elephants (3 females, 2 males, and 2 juveniles). Within the reserve we deployed a local network of 5 Raspberry Shake and Boom units in October 2019 in order to record seismo-acoustic waves generated by the herd. The network also included other seismic and acoustic sensors of different sensitivities which were used to assess the performance Raspberry Shake and Boom units. We show that the Raspberry Shake and Boom units performed well during the deployment, with clear recordings of elephant movement and rumbles. The acoustic data also suggests that we may be able to discriminate between individual elephants due to the distinct frequencies of their rumbles. This presentation will provide general information on the potential use of low-cost sensor units for the purpose of unobtrusively monitoring vulnerable wildlife such as elephants.
Implications of methane emissions in biogeochemical budgeting: A study from a eutrophic tropical lake of South India
Authors: Das Revathy , Krishnakumar Appukuttan Pillai , AnoopKrishnan Krishnan , Nandakumar Vivekanandan
Published: March 2020

Greenhouse gases (GHGs), especially, methane (CH4) emissions from the littoral zones of the lakes play an important role in regional biogeochemical budgets. Only a few studies are available in literature highlighting the direct flux measurements of CH4   from the aquatic systems. In the present study, an attempt has been made to quantify the spatio-temporal variations of CH4 efflux and the key physical factors controlling the emission rate, from the vegetated littoral zones of lake Vellayani (5.55Km2), located in the urbanized area of Thiruvananthapuram city, Kerala, South-West India. CH4 efflux were collected from different vegetations in littoral zones, using a static chamber, during the peak growing seasons from March to October in 2016 and further analyses were carried out by using Gas Chromatograph (PE Clarus 500, PerkinElmer, Inc.). The mean efflux rate of CH4   from the emergent plant species (Phragmites australis and Typha spp.) was 114.4 mg CH4 m-2h-1; while, in the floating leaved species (Nymphaea spp. and Nelumbo Spp.), it   was   observed to be 32.6 mgCH4 m-2h-1. The results reveal that CH4 efflux in the zone of emergent vegetation was significantly higher than the floating-leaved zone indicating the importance of plant biomass and standing water depths for the spatial variations of CH4 efflux. However, no significant temporal variations were noticed in the physical factors during the peak growing seasons. These results indicate that the vegetated littoral zones of lake, especially the emergent plant zones were supersaturated with CH4, facilitating the production of carbon for CH4 emission, but also enable the release of CH4 by the diffusion from the intercellular gas lacunas. We conclude that the atmospheric CH4 emissions will be affected by the growth of exotic species in the lake systems and may be the reason for enhancing the climate warming in local/regional scale.
Detecting original variations in calcite and aragonite input in limestone-marl alternations
Authors: Nohl Theresa , Steinbauer Manuel , Sinnesael Matthias , Jarochowska Emilia
Published: March 2020

The origin of carbonatic rhythmically alternating lithologies, called limestone-marl alternations (LMA), is a lively debated topic. LMA are commonly used as high-resolution cyclostratigraphic record, but diagenetic studies indicate that not all LMA reflect genuine differences in the original composition driven by environmental changes. LMA with a clear difference between limestones and marls in their ratios of diagenetically inert elements such as Al2O3/TiO2 can be identified as the product of primary sedimentary differences, i.e. variation affecting the terrigenous compound of the precursor sediment. In contrast, LMA without these differences could be the product of (1) variations in the carbonate compounds of the precursor sediment, i.e. aragonite and calcite input, or of (2) the distortion of the latter by diagenetic carbonate redistribution, or of (3) diagenetic carbonate redistribution in a homogenous precursor sediment. The problem of differentiating these three cases is known as the diagenetic dilemma. The question is, how can the composition in the original CaCO3 compound (aragonite, calcite) of the precursor sediment be reconstructed? This study provides a new approach to tackle the diagenetic dilemma. According to the model of differential diagenesis, the concentration of trace elements is inversely proportional to the amount of diagenetically redistributed carbonate. Consequently, the difference between the ratios of diagenetically inert elements from two adjacent beds is a measure for carbonate redistribution between them. This is quantifiable by calculating the vector length between these ratios for two adjacent beds. The new approach is illustrated here by evaluating 75 contiguous limestone and marl beds from the Högklint Formation (Silurian) on Gotland, Sweden. To test the new method, trace elements in these beds were compared according to their relative solubility during diagenesis. All elements which are either bound to clay minerals or fit into the calcite lattice show the same pattern of vector lengths (
The European HF Radar Node: focal point to promote land-based remote sensing of coastal surface currents and its applications
Authors: Corgnati Lorenzo , Mantovani Carlo , Rubio Anna , Mader Julien , Reyes Emma , Asensio Igoa Jose Luis , Novellino Antonio , Gorringe Patrick , Griffa Annalisa
Published: March 2020
Climate change impacts on wind power density over southeastern Mediterranean
Authors: Tzanis Chris G. , Philippopoulos Kostas , Cartalis Constantinos , Granakis Konstantinos , Alimissis Anastasios , Koutsogiannis Ioannis
Published: March 2020

Energy production from the utilization of wind energy potential depends on the variability of the wind field as determined by the interaction of natural processes on different scales. Global climate change can cause alterations in the surface wind and thus it may affect the geographical distribution and the wind energy potential variability. Wind energy production is sensitive to wind speed changes, especially in the upper percentile of the wind speed distributions, where energy production is more effective. The importance of wind energy production changes is enhanced by the fact that wind energy investments are long-term and are characterized by high initial costs and low operating costs. In the present study, these changes are examined for the southeastern Mediterranean region, based on simulations of the Regional Climate Model ALADIN 5.2 extracted from the Med-CORDEX database for the climatic scenarios RCP4.5 and RCP8.5. The results indicate a wind power density increase over the Aegean Sea, the Ionian Sea, the Dardanelles and the Black Sea, with similar levels of increase for both climatic scenarios. In contrast, during the winter period there is a decline across the southeastern Mediterranean, which is more significant in the case of the RCP8.5 scenario. Finally, for most areas of eastern Greece, there is a reduction in the number of wind speed cases for both below and above cut-in and cut-out wind speeds, while there is an increase in the number of wind speed cases that wind turbines operate at their maximum power. The results are expected to reduce the uncertainty associated with the impact of climate change on wind energy production. 
Effects of snow melt infiltration and geochemical oxidation on the distribution of sulphate in reclaimed oil sands shale overburden
Authors: Huang Mingbin , Ireson Andrew , Barbour Lee
Published: March 2020

A key risk to reclamation covers over oil sands shale overburden is salinization of the cover soil due to salt transport from the underlying shale. The objective of this study was to evaluate controls on salt ingress based on observations and modelling of the transport of a conservative chemical species, chloride (Cl-), and a produced species, sulphate (SO42-) within reclamation profiles at the South Bison Hills overburden dump located north of Fort McMurray, Alberta, Canada.  The SO42- is produced as a result of pyrite oxidation.  Previously developed water dynamics models, including a fully coupled water and heat transfer model (CM) and a modified CM model (CM-EI) to account for enhanced snow melt infiltration, were coupled with an advective-dispersive transport model to simulate the observed Cl- profiles and concomitantly constrain the solute transport parameters.  This transport model was then used to simulate SO42- migration to evaluate the impact of pyrite oxidation (i.e. depth and SO42- production rate) on the evolving SO42- profiles.  It was found that the observed SO42- distributions could be simulated using an initially low rate of SO42- production (0.1 g SO42- m-2 d-1) in the first 5 years while macropore development as a result of freeze/thaw and wet/dry cycling was occurring, followed by a higher rate (0.62 g SO42- m-2 d-1) once this soil structure evolution was complete.  These average rates were applied over a shale depth of 0.75 m, consistent with field observations of oxygen ingress.  Mass balance estimates using measured available pyrite suggest that at these rates oxidation could continue for approximately 93 years.  Inclusion of enhanced snow melt (CM-EI model) results in higher rates of both net percolation and evapotranspiration (ET). The increased net percolation enables more rapid flushing of the produced SO42- deeper into the profile; however, the increased ET also draws produced SO42- into the cover soils. It is therefore likely that short-term soil salinization of the base of the covers is exacerbated by increased snowmelt infiltration, while in the long run salinity levels will drop due to increased net percolation.   
Maximisation of flood events by superposition at confluences
Authors: Bühler Philipp , Fischer Svenja , Schumann Andreas
Published: March 2020

The superposition of two or more flood events at confluences is an important factor in the genesis of extreme floods. With extreme floods in 2002 and 2013 in Germany, analyses of the genesis of those floods becomes a more vital part in the understanding of their mechanisms. While the superposition is not the main driver of extremity, it still influences the peak significantly, depending on the arrival of the peaks from upstream floods as well as the shape and steepness of the floods. Hereby, the degree of superposition depends much on the flood type: for steep and short waves, the probability of overlapping peaks is low but has a high chance to result in an extraordinary flood or the overlapping of long flood waves has a high probability with a smaller chance to produce a flood event with an extreme peak after the point of confluence. In order to quantify the effects of superposition for extreme events, confluences of tributaries in the Mulde river basin in the east of Germany were analysed based on hourly discharge data. For these events, the range of best- and worst case scenarios was analysed based on sensible shifts of the routing. The travel times and therefore the arrivals of flood events at the downstream gauge were evaluated from the data as well as with a theoretical approach calculated by the mean slope of the stream as a static and the peak discharge of a flood event as the dynamic component. It is shown how the different combinations of arrival times in the downstream gauge may result in long events with damped peaks or a maximization of the flood peaks by overlaying. With the developed methodology, the observed peak can be compared with an ensemble of possible flood events and their peaks, caused by different superposition scenarios. This leads to an extended range of high empirical quantiles for flood statistics, with impact on the selection of most appropriated distribution functions.
The timescale of the endogenous processes and PT conditions of garnet, biotite, and plagioclase equilibrium in the mica schists and gneisses of the Korvatundra complex (Kola region)
Authors: Nitkina Elena , Belyaev (Ϯ) Oleg , Kozlova Natalia , Kaulina Tatiana , Sharkov Evgeny , Kozlov Nikolay
Published: March 2020

The Korvatundra complex is situated between the granite gneisses of the White Sea complex and the rocks of the Tana belt the Kola region (Kozlov et al., 1990; Priyatkina&Sharkov, 1979) and composed of  mica gneisses, schists and quartzite schists. The metamorphism of the complex increases from south to north from the staurolite-muscovite zone to kyanite-garnet-biotite (Map of the mineral facies, 1992; Perchuk&Krotov, 1998).

The U-Pb age of igneous zircon from the metavolcanite is 2101±21 Ma (Kaulina et al., 2003). The early stages of the progressive metamorphism reflected in relict paragenesis in the southern part were under the conditions of the staurolite-chloritoid and staurolite-garnet-two-mica subfacies with 385-570оС and 4.6-7.6  kbar (Belyaev&Petrov, 2002).  The prograde metamorphism were under the conditions of the kyanite-garnet-micas and kyanite-garnet-biotite subfacies and are reflected in the composition of newly formed, chemically non-zonal garnets, or in the similar composition newly formed garnet rim. The metamorphism stage parameters determined by the garnet indicate increasing of the temperatures and pressures to 575-615оС и 7.5-9.1 kbar  (Belyaev&Petrov, 2002) or to 650оС  и 7.5 kbar (Perchuk&Krotov, 1998). The time of prograde metamorphism of the Korvatundra is in the interval 1940 and 1917 Ma. Within the Korvatundra the processes of superimposed tectonometamorphism occur under conditions of the kyanite-garnet-biotite subfacies and in the north of the Korvatundra their temperatures and pressures reach of 700-750 ° C and 13-14 kbar, correspondingly. 

 

This research was funded by GI KSC RAS program 0226-2019-0052 and Fundamental Program of the Presidium of RAS section “Fundamental geological and geophysical research of the lithosphere processes”.

 

Belyaev O.A, Petrov V.P. // Apatity: GI KSC RAS. 2002. P. 195-208.

Map of the metamorphic rock mineral facies of the Baltic Shield. S.-Pb.: VSEGEI. 1992.

Kaulina T.V., Dlenizin A.A., Belyaev O.A., Kozlova N.E., Apanasevich E.A. // S.-Pb.: IPG RAS. 2003. 189-193 p.

Kozlov N.E., Ivanov A.A., Nerovich L.I. // Apatity: KSC RAS, 1990. 172 p.

Perchuk L.L.., Krotov A.V. // Petrologia. 1998. V.7. №4. P. 356-381.

Priyatkina L.A., Sharkov E.V. // Leningrad: Nauka. 1979. 127 с.
Six-degree-of-freedom seismogeodesy by combining collocated high-rate GNSS, accelerometers and gyroscopes
Authors: Geng Jianghui , Wen Qiang , Chen Qijin
Published: March 2020

High-rate GNSS receivers, sampling satellite signals at over 1-Hz rate, can record strong ground motions and directly in the form of displacements instead of velocities or accelerations. In this case, broadband displacement waveforms down to 0 Hz can be obtained nominally; the benefit is that static offsets can be identified accurately from high-rate displacements with minimal contamination by the very early postseismic signals. The drawback of high-rate GNSS, however, consists in its orders of magnitude higher noise than that of seismometers, almost on all frequency bands concerning seismic studies. Combining collocated high-rate GNSS and accelerometers can be a remedy and produces broadband seismogeodetic displacements. However, accelerometer data must be heavily downweighted due to their baseline errors originating primarily in instrument rotations, and therefore their contribution to seismogeodetic displacements is seriously underestimated. We further introduced a gyroscope into this classic seismogeodesy to mitigate baseline errors and formulated advanced six-degree-of-freedom (6-DOF) seismogeodesy without undervaluing accelerometer data. A shake table holding one GNSS antenna, four accelerometers, and one gyroscope was used to simulate waveforms from the 2010 Mw 7.2 El Mayor-Cucapah earthquake. We found that the displacements derived from the 6-DOF seismogeodesy were up to 68% more accurate than those from the classic seismogeodesy over 0.04–0.4 Hz. Moreover, broadband rotations containing the permanent components were also generated, which were unachievable by integrating gyroscope data. We believe that the 6-DOF seismogeodesy is capable of improving both source rupture studies of large earthquakes and high-rise monitoring under strong seismic waves.
Astronomically paced climate changes during the demise of the penultimate icehouse
Authors: Fang Qiang , Wu Huaichun
Published: March 2020

Late Paleozoic deglaciation is the only deep-time analogue of an icehouse-to-greenhouse transition in a vegetated world, but the detailed processes of this climatic upheaval are still under debate due to the absence of higher precision and accuracy in global correlations. The astronomical calibration of sedimentary cycles (3–4 m) in a carbonate succession from Naqing in South China to the 405 kyr eccentricity cycle reveals short eccentricity (135 kyr and 96.1 kyr), main obliquity (31.6 kyr), and precession (21.5 kyr and 19.3 kyr) for the early Cisuralian (Early Permian). 405-kyr-eccentricity-forced teleconnections are established between Paleo-Tethyan deep-marine carbonate cyclicity and U-Pb zircon ages-calibrated cyclothems from Euramerica in the Pangean paleotropics, providing a refined chronostratigraphy for the Asselian and Sakmarian stages on global scale. Geological record indicates a (s4 − s3) − (g4 − g3) resonance likely transited into (s4 − s3) − 2(g4 − g3) resonance at ~296.8 Ma, which confirms the chaotic dynamical behaviour of the Solar System during the Cisuralian. The synchronized proxies from marine records (magnetic susceptibility, gamma ray, carbon and oxygen isotope) and terrestrial climate indicators (paleosols, evaporates and tillites) across continents and latitudes demonstrate that long-term glacial, glacioeustatic, and climatic events were in pace with eccentricity and obliquity modulation cycles superimposed on secular global warming, reinforcing solid linkage between climate changes at low and high latitudes regardless of the ice sheet volume. Quasi-periodic alignments of the maxima (minima) of eccentricity and obliquity amplitude decelerated (accelerated) the trajectory of the CO2-forced deglaciation. Intermittent nondeposition of the Cisuralian cyclothems on the North American Midcontinent correspond to the enhanced none-astronomical-related noise in the sedimentary record from South China, both of which were likely attributed to weaker or less apparent influence of astronomical forcing on the climate changes without an ice-sheet amplifier. Our study provides a better temporal resolution and understanding of the late Paleozoic deglaciation.
Plotting for Synthesis of Large Datasets
Authors: Kelleher Christa , Braswell Anna
Published: March 2020

In the age of big data, hydrologic studies contain more sites, longer and more resolute simulated and observed timeseries, and finer resolution spatial data than ever before.  This growth in capabilities to collect and generate data represents a tremendous opportunity for hydrologic science, but can challenge creating and presenting figures that summarize this information in succinct, interpretable, and meaningful ways.  To address this challenge, this presentation reviews several plotting approaches focused on synthesis of large hydrologic and environmental datasets from across the literature.  We highlight plots that can be used to visualize multi-dimensional spatial and temporal modeling and observational data, to synthesize patterns, to highlight outliers, and above all to convey key messages.  Building on these different types of plots, we highlight a set of best practices for how we as a community can create effective visualizations that synthesize large datasets of a variety of types in scientific presentations and publications.
Global gravity wave detections at infrasound stations of the International Monitoring System
Authors: Hupe Patrick , Ceranna Lars , Le Pichon Alexis
Published: March 2020

Atmospheric gravity waves (GWs) transport energy and momentum horizontally and vertically. The dissipation of GWs can modify the atmospheric circulation at different altitude layers. Knowledge about the occurrence of GWs is thus essential for Numerical Weather Prediction (NWP). However, uniform networks for global GW measurements are rare, and satellite observations generally allow to derive GW parameters in the middle and upper atmosphere only. The barometric sensors of the International Monitoring System (IMS) infrasound network can potentially fill this gap of global GW observations at the Earth’s surface. This infrasound network has been established for monitoring the atmosphere to verify compliance with the Comprehensive Nuclear-Test-Ban Treaty.
Two alternative configurations of the Progressive Multi-Channel Correlation Method (PMCC) are discussed for deriving GW detections from the differential pressure data. These configurations focus on GW frequencies equivalent to periods of between 5 min and 150 min. This range covers sources of deep convection, particularly in the tropics, whereas at mid-latitudes, GWs are hard to distinguish from other low-frequency signals, e.g. coherent wind noise. Challenges and perspectives of using the IMS infrasound data for deriving ground-based GW parameters useful for NWP will be discussed.
Fluid flow and pore pressure development throughout the evolution of a trough mouth fan and implications for the slope stability, western Barents Sea
Authors: Llopart Jaume , Urgeles Roger , Forsberg Carl Fredrik , Camerlenghi Angelo , Vanneste Maarten , Rebesco Michele
Published: March 2020

Using a combination of geophysical and geotechnical data from the Storfjorden Trough Mouth Fan, off southern Svalbard, we investigate the role of glacial advances and retreats over the continental shelf on the hydrogeology of the continental margin. The results of compressibility and permeability tests are used together with margin stratigraphic models from seismic data, as input for numerical finite element models to understand focusing of interstitial fluids in glaciated continental margins. The modeled evolution of the Storfjorden TMF from 2.7 to 0.2 Ma shows that onset of glacial sedimentation (~1.5 Ma) had a significant role in developing aquicludes (tills) on the shelf that decreased the vertical fluid flow towards the sea floor and diverted it towards the slope. This model shows that prior to 220 ka, high overpressure ratio (λ~0.6) develops below the shelf edge and in the middle slope. A more detailed, high resolution model for the last 220 kyrs accounting for ice loading during Glacial Maxima shows that the less permeable glacigenic debris flows deposited during glacial maxima on the slope hinder fluid evacuation from the plumites. This effect in combination with the fluid flow focusing from the shelf allows high overpressure ratio (λ~0.7) to develop in the shallower-most plumite layers. These high overpressures likely persist to the Present and are critical in determining the onset of submarine slope failure. The safety factor of the upper continental slope is reduced by 60% due to the combination of high sedimentation rates, ice loading and focusing of fluids during Glacial Maxima with values of the factor of safety reaching 1.2 during the LGM and beginning of the last deglaciation.
Causes and consequences of Southern Ocean change: the IPCC SROCC assessment
Authors: Meredith Michael , Sommerkorn Martin , Cassotta Sandra , Derksen Chris , Ekaykin Alexey , Hollowed Anne , Kofinas Gary , Mackintosh Andrew , Melbourne-Thomas Jess , Muelbert Monica , Ottersen Geir , Pritchard Hamish , Schuur Ted , Meijers Andrew , Hogg Andrew , Hallberg Robert , Tagliabue Alessandro , He Shengping , Peck Victoria
Published: March 2020

Climate change in the polar regions exerts a profound influence both locally and over all of our planet.  Physical and ecosystem changes influence societies and economies, via factors that include food provision, transport and access to non-renewable resources.  Sea level, global climate and potentially mid-latitude weather are influenced by the changing polar regions, through coupled feedback processes, sea ice changes and the melting of snow and land-based ice sheets and glaciers.

Reflecting this importance, the IPCC Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC) features a chapter highlighting past, ongoing and future change in the polar regions, the impacts of these changes, and the possible options for response.  The role of the polar oceans, both in determining the changes and impacts in the polar regions and in structuring the global influence, is an important component of this chapter.

With emphasis on the Southern Ocean and through comparison with the Arctic, this talk will outline key findings from the polar regions chapter of SROCC. It will synthesise the latest information on the rates, patterns and causes of changes in sea ice, ocean circulation and properties. It will assess cryospheric driving of ocean change from ice sheets, ice shelves and glaciers, and the role of the oceans in determining the past and future evolutions of polar land-based ice. The implications of these changes for climate, ecosystems, sea level and the global system will be outlined.
A comparison study of tidal prediction techniques for applications in the German Bight
Authors: Boesch Andreas , Jandt-Scheelke Simon
Published: March 2020

The harmonic representation of inequalities (HRoI) is a technique for tidal analysis and prediction. The HRoI has been used at BSH for over six decades to calculate heights and times of high and low waters for German tide tables. In its original form, it is tailored to predict the vertices of semi-diurnal tides. A more generalized version of the HRoI allows analysing the full tidal curve at equal fractions of the mean lunar day. We compare results from the HRoI with other tidal analysis techniques, e.g. the common harmonic method, for locations in the German Bight. The study includes several tide gauges in the rivers Ems, Weser and Elbe. Short durations of rise and rapid water level changes after low water often characterize the tide curves in these rivers and pose challenges to tidal predictions.
Dynamic and thermodynamic drivers of Arctic lower tropospheric warm extremes
Authors: Papritz Lukas
Published: March 2020

Recent decades have revealed dramatic changes in the high Arctic (> 80°N) related to natural variability and anthropogenic climate change. In particular, episodes of extremely warm temperatures in the lower troposphere and their role for sea ice melting have gained considerable attention. While it has been recognized that injections of warm and humid air masses contribute to wintertime warm anomalies, summertime warm anomalies have also been linked to blocking anticyclones within the high Arctic. Yet, the relative importance of the various thermodynamic and atmospheric dynamical processes that can contribute to the formation of extreme warm anomalies in the high Arctic is poorly understood.

In this work, we present a systematic analysis of the processes leading to the formation of winter- and summertime lower tropospheric warm extremes in the high Arctic by means of kinematic backward trajectories based on the ERA-Interim reanalysis. The trajectories enable us to quantify the relative contributions of poleward transport from (potentially) warmer regions, adiabatic warming due to subsidence, and diabatic heating associated with surface sensible heat fluxes and latent heat release. Furthermore, we relate these processes to atmospheric dynamical flow features such as atmospheric blocking and extratropical cyclones.

Our analyses reveal that subsidence in blocking anticyclones over the Barents and Kara Seas and diabatic warming by surface sensible heat fluxes are the dominant mechanisms leading to wintertime warm extremes (contributing about 40% each), whereas the transport from southerly latitudes – predominantly accomplished by the injection of warm and humid air masses associated with an intensified and westward displaced storm track in the Nordic Seas - is of secondary importance (20%). Summertime warm anomalies, in contrast, are essentially the result of subsidence in blocking anticyclones (70%) that are located within the high Arctic. Thus, our findings point towards a rich, seasonally varying spectrum of dynamical and thermodynamic processes contributing to Arctic warm extremes that result from a complex interplay between transport induced by dynamical weather systems and diabatic processes. Furthermore, they emphasize the importance of processes within the Arctic for the formation of warm extremes.

Papritz, L., 2019: Arctic lower tropospheric warm and cold extremes: horizontal and vertical transport, diabatic processes, and linkage to synoptic circulation features, J. Climate, doi: 10.1175/JCLI-D-19-0638.1