bluuebunny/crossref_metadata_2025 huggingface dataset:
Origin and evolution of the lowermost lava successions at Santorini volcano (Greece): insights from major and trace element composition of rocks from the submarine caldera wall
Authors: Pank Katharina , Hansteen Thor H. , Geldmacher Jörg , Garbe-Schönberg Dieter , Jicha Brian , Hauff Folkmar , Hoernle Kaj
Published: March 2021

Santorini volcano in the central sector of the South Aegean volcanic arc is one of the most active and potentially dangerous magmatic systems in Europe having had twelve Plinian eruptions over the last 350 ka of which at least four eruptions were accompanied by caldera collapses. The well-known Late Bronze Age eruption (~3.6 kaA) for example is considered to rank as one of the largest eruptions since the Late Miocene.

The main focus of research thus far has been on the comparatively young and subaerial deposits, whereas older stages of volcanism have been poorly studied. Our study comprises samples from the submarine caldera flanks and gives new insights into the early evolutionary stages of Santorini volcano, contributing to a better understanding of its eruptive history and potential risks. The submarine lava successions were sampled along the inner caldera wall by a remotely operated vehicle (ROV) during R/V POSEIDON cruise 511 in 2017.

The investigated lavas can be divided into two magmatic series: a low-K basaltic series overlain by medium- to high-K series, including basaltic andesites, andesites and occasional dacites. First results of 40Ar/39Ar dating reveal ages of ~250 ka for the andesites. For the presumably older basalts, no reliable age data could be obtained.

Major and trace element compositions and mineral zoning patterns suggest that fractional crystallization was the dominant process controlling magma evolution. In addition, repeated magma mixing played an important role as indicated by characteristic zonation patterns within plagioclase and clinopyroxene ante- and phenocrysts. Comparison of the major and trace element compositions with published data from subaerial deposits show a strong similarity between our lavas and the ~528-308 kaA old deposits of Peristeria volcano, a composite stratocone in the north of the volcanic field and whose subaerial deposits are found on northern Thera onlyB. This similarity is also supported by the Sr-Nd-Pb isotopic compositions of our lavas. Our results indicate both an extended age range of Peristeria activity and a much wider geographic distribution of its lava flows than previously recognized.

 

A T. H. Druitt et al. (1999), Santorini Volcano, Geological Society of London Memoir

B T. H. Druitt et al. (2015): Field guide to Santorini Volcano
Prediction of Surface Water Resources in Danjiangkou Basin Based on ESP and Distributed Hydrological Model
Authors: Yuan Ruifang , Cai Siyu , Liao Weihong
Published: March 2021

 The prediction of surface water resources in the Danjiangkou Basin is of great significance for the design of the water transfer plans for the South-to-North Water Diversion Project. However, it is difficult to obtain high-precision simulations for mid- and long-term hydrological forecasting. Based on the thought of extended streamflow prediction (ESP) and distributed hydrological models, this paper proposed a set of forecasting systems for predicting the annual surface water resources in the Danjiangkou Basin. Firstly,  the Wetspa model  was established to forecast the inflow of Danjiangkou reservoir. The Nash efficiency coefficients of the monthly average runoff during the calibration period (2006-2012) and verification period (2013-2016) were 0.97 and 0.95, respectively. Secondly, it was assumed that the rainfall of 2017 could be predicted by the rainfall forecasting model, then the rainfall process was obtained based on the ESP and the runoff process of the basin outlet was calculated through the Wetspa model. Finally, the predicted surface water resources of the Danjiangkou Basin in 2017 was 45.448 billion m3, and the actual surface water resources is 40.395 billion m3, with a relative error of 12.51%. The results showed that the prediction of surface water resources in Danjiangkou Basin based on ESP and distributed hydrological model could provide a certain reference for the design of water transfer plans of the Danjiangkou Reservoir.

Key words: Water resources prediction; ESP; Wetspa model; Nash coefficient
Extreme convection in the Lofoten Basin of the Norwegian Sea
Authors: Fedorov Aleksandr M. , Raj Roshin P. , Belonenko Tatyana V. , Novoselova Elena V. , Bashmachnikov Igor L. , Johannessen Johnny A. , Pettersson Lasse H.
Published: March 2021

One of the factors affecting the variability of the global climate is strong oceanic convection. Current research declares the results of the investigation on the extreme convection in the Lofoten Basin (LB) using the Argo profilers data. The most common parameter reflecting the convection intensity is Mixed Layer Depth (MLD). In the frames of the understudied period, MLD exceeds 1000 m in March-April and December 2010 in the Lofoten Basin Eddy (LBE), whereas the average MLD is about 200 m and rarely exceeds 400 m in the basin. Water volume formed at mid-depth of the central LB, between 1000 m depth and the isosteric surface s07 is connected with the extreme convection events. We analytically assess the final mixing depth that corresponds well to measured values of the MLD. Such a correspondence indicates the variations in the buoyancy flux and stratification as the main reasons for MLD variability in the LB. We easily explain this variability due to heat release in the basin. Atmospheric patterns during the extreme convection are described. It occurs that northerly winds are as common as dominating south-westerly winds during the months with extreme convection. 32 cases of extreme convective events with MLD exceeding 350 m were analyzed and we reveal that correspondent composite maps of Sea Level Pressure (SLP) and surface heat flux match well NAO-/EAP- atmospheric pattern in the Northern Atlantic, while negative NAO pattern prevails in climate during winter-spring. We define the heat release as the major trigger of strong convection. Heat release associated with extreme convection events in the LB is twice stronger than usual.
Petrographic and geochemical fingerprinting of flints from the type-Maastrichtian (SE Netherlands and NE Belgium): implications for flint formation and provenance
Authors: Van der Geest Hannah , Vellekoop Johan , Kaskes Pim , Sinnesael Matthias , Jagt John , Degryse Patrick , Claeys Philippe
Published: March 2021

The chalk deposits of the type-Maastrichtian, in the SE Netherlands and NE Belgium (the Liège-Limburg region), are characterized by abundant flint layers. Since prehistoric times, flints from this region have been used as raw materials for tool making. While the formation, cyclicity and lithostratigraphy of flint layers from the type-Maastrichtian have been previously studied, their stratigraphic, lateral and internal geochemical and petrological variability are still poorly constrained, posing challenges for tracing the provenance of flint tools. Therefore, in the context of the Maastrichtian Geoheritage Project, we are analysing in-situ flint samples macroscopically, microscopically and with micro-X-ray fluorescence (µXRF). The flint samples were collected from a 50-m-thick interval from the Upper Cretaceous Gulpen Formation at the former ENCI quarry (NL) and the Hallembaye quarry (BE). In contrast to averaged outcomes of bulk or portable X-ray fluorescence techniques commonly used for provenance studies of flints in geoarchaeology, the use of µXRF has the advantage of offering insights into the internal variability and heterogeneity of flints, by displaying relative distributions of major and trace elements within flint samples. Our preliminary results show that flint nodules from the Gulpen Formation can be subdivided based on composition. Flint layers in the middle part of this formation (Vijlen Member) show a high contribution of micrite, in addition to silica, and display a heterogeneous distribution of elements such as Ca, S, K, Fe, Rb and Sr, while flint layers from the overlying Lixhe 1-3 members consist predominantly of silica and have a more homogeneous distribution of chemical elements. Both types of flint layers contain biogenic inclusions, such as fragments of sponge spicules, echinoids, shells and benthic/planktic foraminifera, and other minerals, including iron sulphides and glauconite, but with a different abundance. The observed heterogeneity and variability within the flint nodules might not only be useful for tracing the provenance of flint tools, but could also provide insights into the complex formation of flints.
Possible Reason of the Dependence of an Apparent Permeability on the Pressure Gradient at low Flow Rates in Laboratory Study
Authors: Baryshnikov Nikolay , Zenchenko Evgeniy , Turuntaev Sergey
Published: March 2021

Currently, a number of studies showing that the injection of fluid into the formation can cause induced seismicity. Usually, it is associated with a change in the stress-strain state of the reservoir during the pore pressure front propagation. Modeling this process requires knowledge of the features of the filtration properties of reservoir rocks. Many researchers note the fact that the measured permeability of rock samples decreases at low pressure gradients. Among other things, this may be due to the formation of boundary adhesion layers with altered properties at the interfaces between the liquid and solid phases. The characteristic thickness of such layer can be fractions of a micron, and the effect becomes significant when filtering the fluid in rocks with a comparable characteristic pore size. The purpose of this work was to study the filtration properties of rock samples with low permeability at low flow rates. Laboratory modeling of such processes is associated with significant technical difficulties, primarily with the accuracy limit of measuring instruments when approaching zero speed values. The technique used by us to conduct the experiment and data processing allows us to study the dependence of the apparent permeability on the pore pressure gradient in the range of 0.01 MPa/m, which is comparable to the characteristic pressure gradients during the development of oil fields. In the course of the study, we carried out laboratory experiments on limestone core samples, during which the dependencies of their apparent permeability on the pore pressure gradient were obtained. We observed a significant decrease in their permeability at low flow rates. In the course of analyzing the experimental results, we proposed that a decrease in apparent permeability may occur due to the effect of even a small amount of residual gas in the pore space of the samples. This has been confirmed by additional experiments. The possibility of clogging of core sample pore space must be considered when conducting when conducting laboratory studies of the core apparent permeability.
Observation of TGFs at Mid Latitude
Authors: Maiorana Carolina , Marisaldi Martino , Füllekrug Martin , Soula Serge , Lapierre Jeff , Mezentsev Andrey , Skeie Chris Alexander , Heumesser Matthias , Chanrion Olivier , Østgaard Nikolai , Neubert Torsten , Reglero Victor
Published: March 2021

We present a sample of Terrestrial Gamma-ray Flashes (TGFs) observed at mid latitudes by the Atmosphere Space Interaction Monitor (ASIM). The events were detected over the period June 2018 - August 2020 in the latitude bands between 35° and 51° and between -35° and -51°; the sample includes the first observations above ±38°. The characteristics of these mid-latitude events are consistent with the global population concerning the number of counts, but durations are significantly shorter. We also analyze the meteorological context and the general evolution of the parent storms and we show that the storms are not extreme in terms of total duration and extension. Finally, we present an estimation of the TGF occurrence rate at mid latitudes, based on ASIM's exposure, the local flash rate and tropopause altitude, and we show that it is outside but very close to two standard deviation from the rate of production at tropical latitudes, corrected by the higher atmospheric absorption of higher latitudes. This means that atmospheric absorption plays a major role in the detection of TGFs at mid latitudes, but we cannot rule out other factors.
Sentinel-1 snow depth assimilation improves river discharge simulations in the western Alps
Authors: Brangers Isis , Lievens Hans , Getirana Augusto , Kumar Sujay , De Lannoy Gabrielle
Published: March 2021

In many of the world’s mountainous regions, river discharge is largely influenced by the seasonal melt of snow. Therefore, accurate information on the amount of water stored as snow is essential for water management and flood forecasting. However, there are large uncertainties in model simulations of snow depth, partly due to uncertain precipitation estimates in mountain regions with complex topography. A study by Lievens et al. (2019) showed the potential of Sentinel-1 (S1) satellite observations to provide snow depth estimates at 1 km spatial and ~weekly temporal resolution in mountain regions. In this study, we assimilated these retrievals into the Noah Multiparameterization (Noah-MP) v3.6 land surface model for the western Alps using an ensemble Kalman filter. The land surface model was coupled to the Hydrological Modeling and Analysis Platform (HyMAP) routing scheme to also provide estimates of river discharge. With S1 data assimilation, the snow depth estimates improved, reducing the bias from 0.23 m to 0.05 m compared to in situ measurements. Preliminary results also show improved discharge simulations mainly in mountain catchments at high elevations that are less prone to regulations (e.g., by dams). This study demonstrates the capability of the S1 snow depth retrievals to improve not only snow depth estimates, but also the estimation of snow melt water contributions to river discharge.
Modeling of plant water uptake in two distinct forest stands using whole-plant capacitance approach
Authors: Skalova Veronika , Dohnal Michal , Votrubova Jana , Vogel Tomas , Tesar Miroslav
Published: March 2021

Soil-plant-atmosphere interactions are studied to improve the estimation of actual transpiration – the key part of the catchment water balance. The one-dimensional soil water flow model S1D, involving vertically distributed macroscopic root water uptake and whole-plant hydraulic capacitance, was used. The model is based on the numerical solution of Richards' equation coupled with a transient transpiration stream algorithm.

The study focuses on the catchment Liz located in the Bohemian Forest, Czech Republic. The catchment is covered with Norway spruce (Picea abies) and European beech (Fagus sylvatica). In 2020, sap flow measurements by thermal dissipation probes were conducted at both forest environments. Soil water pressure head, soil water content, and soil temperature data, as well as complete meteorological data from the nearby meteorological station, were also available for the whole period of interest.

The registered sap flow and simulated transpiration fluxes are compared with a particular attention to the different behavior of isohydric (spruce) and anisohydric (beech) trees. The model reasonably well reproduces the plant responses caused by both the high midday potential transpiration demand and the occasional soil drought.

The research is supported by the Czech Science Foundation Project No. 20-00788S.
Stable finite element method for solving the oblique derivative boundary value problems in geodesy
Authors: Macák Marek , Minarechová Zuzana , Čunderlík Róbert , Mikula Karol
Published: March 2021

We presents local gravity field modelling in a spatial domain using the finite element method (FEM). FEM as a numerical method is applied for solving the geodetic boundary value problem with oblique derivative boundary conditions (BC). We derive a novel FEM numerical scheme which is the second order accurate and more stable than the previous one published in [1]. A main difference is in applying the oblique derivative BC. While in the previous FEM approach it is considered as an average value on the bottom side of finite elements, the novel FEM approach is based on the oblique derivative BC considered in relevant computational nodes. Such an approach should reduce a loss of accuracy due to averaging. Numerical experiments present (i) a reconstruction of EGM2008 as a harmonic function over the extremely complicated Earth’s topography in the Himalayas and Tibetan Plateau, and (ii) local gravity field modelling in Slovakia with the high-resolution 100 x 100 m while using terrestrial gravimetric data.

[1] Macák, Z. Minarechová, R. Čunderlík, K. Mikula, The finite element method as a tool to solve the oblique derivative boundary value problem in geodesy. Tatra Mountains Mathematical Publications. Vol. 75, no. 1, 63-80, (2020)
Study of Propagation of Acoustic-Gravity Waves Generated by Tropospheric Heat Source
Authors: Kurdyaeva Yuliya , Kshevetskii Sergey
Published: March 2021

     The use of experimental data on pressure variations on the Earth's surface makes possible to study the propagation of acoustic-gravity waves from the lower to the upper atmosphere. However, a question arises: how the pressure on the Earth's surface is related to meteorological processes and how significant inaccuracy is allowed when replacing tropospheric meteorological sources instead experimentally observed pressure fluctuations on the Earth's surface.

     The problem of wave propagation from a tropospheric heat source was analytically studied to resolve this issue. Based on general assumptions about the tropospheric source and its parameters, an estimate of the waves that could be generated by such source was made. The study showed that the generation of internal gravity waves by a heat source cannot occur without the generation of infrasonic waves by this source. Therefore, infrasonic waves must also be taken into account. The source of infrasonic waves was defined and it was shown that in terms of power it is approximately equal to the source of internal gravity waves. Despite this, the amplitude of the generated infrasonic waves is less than the amplitude of the gravity ones, due to the fact that the source frequency is less than the acoustic cutoff frequency.

     In the numerical study of this problem, model local thermal small-sized tropospheric sources of waves operating at different frequencies were studied. Pressure fluctuations at the Earth's surface from the studied model source are recorded and then used at the boundary surface to calculate the propagation of waves upward from pressure fluctuations. Comparison results of calculations directly from a tropospheric source operating at infrasonic frequencies and from recorded pressure fluctuations on the Earth's surface showed that the wave pattern above the source, created directly by the tropospheric source, and from pressure variations recorded on the Earth's surface, practically coincide. In the case when the tropospheric source operates at the frequencies of internal gravity waves, the general coincidence of the two wave patterns also takes place. However, the quality of this match is lower. This happens due both to the typical features of the propagation of the internal gravity waves themselves, and to the fact that during the operation of such a source, infrasonic waves are additionally generated.

     The reported study was funded by RFBR and Kaliningrad region according to the research project № 19-45-390005.
Effects of rainfall spatial-temporal variability on flash flood modelling
Authors: Khosh Bin Ghomash Shahin , Bachmann Daniel
Published: March 2021

Precipitation time series with high spatial and temporal resolutions are the driving force for hydrodynamic modelling of floods. Spatially-uniform precipitation correlated to a certain return period which typically is derived based on point rainfall records have been used for flood risk evaluation. This is mainly due to reasons such as limited observed data, low-density measuring networks or merely the inherent simplicity of using spatially-uniform rain storms in flood simulations. While the use of such rainfalls is convenient, spatially-uniform design storms tend to neglect the impact of rain spatial variability on the hydrological response of the hydrological catchment. Additionally, extreme storm events with high temporal and spatial variability are predicted to occur more often as a result of climate change.

In this work, we study the extent spatially explicit precipitation can affect flooded areas, water levels and surface flow generation in catchment areas in flood modelling. Moreover, the influence of rainfall spatial resolution is also taken into account. This is achieved by means of physically-based, spatially explicit surface flow simulations using the tool ProMaIDes (2021), a free software for risk-based evaluation of flood risk mitigation measures. Precipitation data is generated based on the Poisson distribution and furthermore spatially interpolated in different resolutions using interpolation methods such as the Inversed Distance Squared method and Kriging.

Our study area is the Kan river catchment located in the province of Tehran (Iran) with a total area of 836 km², which has experienced multiple flooding events in recent years. Due to its semi-arid climate and steep topography, the area has high potential for flash flood occurrence as a result of high intensity precipitation.

The results of this study show a range of possible magnitudes of influence of rainfall spatial variability on the catchment´s runoff response. The resulting flood maps highlight the importance of rainfall spatial-temporal variability in the estimation of flood likelihood in urban catchment areas. Moreover, the flood maps resulting from spatially explicit rain signals provide a more comprehensive assessment of flooding in contrast to the spatially-uniform rainfall events, which allows for better flood risk mitigation decisions.

ProMaIDes (2021): Protection Measures against Inundation Decision support. https://tinyurl.com/promaides77 (last access 11.1.2021)

Acknowledgment: This work is part of the BMBF-IKARIM funded project HoWaMan (Sustainable Strategies and Technologies for Flood Risk Management in Arid and Semi-arid Areas)
Large deltas versus small deltas: Two different beasts
Authors: Syvitski Jaia
Published: March 2021

Many studies rank deltas as a continuum, as conditioned by hinterland drainage area, river discharge, sediment load, ocean energy, or even human interaction.  This scaling has helped advance our understanding on how these important coastal deposits develop. From such studies, equilibrium states have been identified, such as the balance between sediment supply and the subsequent dispersal of incoming sediment.  Conceptual equations are used to track the influence of changing boundary conditions such as sea level rise (or fall) that can then expose the role of anthropogenic influences such as groundwater mining.  However, scaling may not reveal important differences between small-scale deltas, that globally number in the thousands, and large regional deltas that number in the dozens.  For example backwater effects appear important in large delta systems but can often be ignored in many smaller delta systems with steeper fluvial gradients. Large deltas are home to large human populations and their infrastructure, but does this influence scale with delta size? This overview presentation explores the use of conceptual equations to determine if there is a limit to scaling.
Low-flow forecasting in France: update on the latest developments of the PREMHYCE operational forecast platform
Authors: Bourgin François , Tilmant François , Véron Anne-Lise , Besson François , François Didier , Le Lay Matthieu , Nicolle Pierre , Perrin Charles , Rousset Fabienne , Thiéry Dominique , Willemet Jean-Marie , Magand Claire , Morel Mathilde
Published: March 2021

Low-flow forecasting can help to improve water management at places where a number of uses can be affected by diminishing water supply from rivers. Several French institutes (INRAE, BRGM, EDF, Lorraine University and Météo-France) have been collaborating to set up an operational platform, called PREMHYCE, for low-flow forecasting at the national scale, in cooperation with operational services. PREMHYCE includes five hydrological models and low-flow forecasts can be issued up to 90 days ahead for more than 800 basins. Several input scenarios are considered: ECMWF 14-days ensemble forecasts, ensemble streamflow prediction (ESP) using historical climatic data, and a no precipitation scenario. Outputs from the different hydrological models are combined into a multi-model approach to improve robustness of the forecasts. The tool provides text files and graphical representation of forecasted low-flows, as well as key low-flow indicators, such as the probabilities of being under low-flow thresholds provided by operational services. The presentation will show the main characteristics of this operational forecast platform, its latest developments and the results on the recent low-flow periods.
How confident are predictability estimates of the winter North Atlantic Oscillation?
Authors: Weisheimer Antje , Decremer Damien , MacLeod David , O'Reilly Chris , Stockdale Tim , Johnson Stephanie , Palmer Tim
Published: March 2021

Predictions of the winter NAO and its small signal-to-noise ratio have been a matter of much discussion recently. Here we look at the problem from the perspective of 110-year-long historical hindcasts over the period 1901-2010 performed with ECMWF’s coupled model. Seasonal forecast skill of the NAO can undergo pronounced multidecadal variations: while skill drops in the middle of the century, the performance of the reforecasts recovers in the early twentieth century, suggesting that the mid-century drop in skill is not due to a lack of good observational data. We hypothesize instead that these changes in model predictability are linked to intrinsic changes of the coupled climate system. 

The confidence of these predictions, and thus the signal-to-noise behaviour, also strongly depends on the specific hindcast period. Correlation-based measures like the Ratio of Predictable Components are shown to be highly sensitive to the strength of the predictable signal, implying that disentangling of physical deficiencies in the models on the one hand, and the effects of sampling uncertainty on the other hand, is difficult. These findings demonstrate that relatively short hindcasts are not sufficiently representative for longer-term behaviour and can lead to skill estimates that may not be robust in the future.

See also: Weisheimer, A., D. Decremer, D. MacLeod, C. O'Reilly, T. Stockdale, S. Johnson and T.N. Palmer (2019). How confident are predictability estimates of the winter North Atlantic Oscillation? Q. J. R. Meteorol. Soc., 145, 140-159, doi:10.1002/qj.3446.
Coseismic displacement interferences and patterns along subduction megathrusts: insights from analog modelling
Authors: Corbi Fabio , Poli Piero , Bedford Jonathan , Funiciello Francesca
Published: March 2021

Finding a deformation pattern that is representative of a given stage of the seismic cycle of subduction megathrusts is crucial as this might provide clues about the upcoming earthquake. Here we focus on the short term interaction between seismic asperities and in particular on how geodetic velocities change in response to ruptures of an along-strike neighbor portion of the megathrust. Enhanced megathrust coupling, slab acceleration, in plane bending of the overriding plate, continental-scale viscoelastic mantle relaxation have been proposed as potentially responsible driving mechanisms. However, the paucity of observations from natural cases and the multiple- interrelated contributions that act at different spatial and temporal scales complicate the understanding of this process.

We use an analog model that simulates a series of laterally partial ruptures and analyze systematically the effect of slip episodes on deformation history of the neighbor “receiver” region. The analog model has the advantage of reproducing tens of seismic cycles with well controlled boundary conditions. The model shows that the deformation pattern associated to slip episodes has a characteristic twisting about a vertical axis. Such twisting interfere positively (causing velocity increase) or negatively (causing velocity decrease) with local interseismic velocity field depending on time since the last earthquake. Identifying accelerating or decelerating velocities in geodetic timeseries could be therefore informative of the seismic evolution of a subduction zone.
Thermobarometry and geochemistry of the mantle section beneath Morkoka pipe Central Yakutia Russia
Authors: Vavilov Mikhail , Ashchepkov Igor , Mevedev Nikolai
Published: March 2021

The Morkoka pipe belonging to the territory of West Daldyn terrane but It has all the features which are characteristic to the Malo- Botuobinsky or Upper MunaThe lower part of mantle section is represented by the depleted lower part of mantle section with the high amount of sub  Ca garnets with the high amount like in Mir pipe and rather long lineal ilmenite trend from the LAB at 7.5 GPA to the Moho at 2 GPA which is also the common feature of most pipe from the Magan terrane an happens in the Upper Muna field  Though the Morkoka pipe itself is barren the nearest territories around contain similar indicator minerals which shot ha there is a group pf pipes and some of them may be diamondiferous. The TRE patterns show mainly S- type which is perspective for the prospecting of diamonds.  But the HFSE for the garnets reveal rather high Zr>Hf peaks which became higher with the HREE level, (Ta>Nb) and higher than La. The LILE and Ba are typically low  but Th U sometimes higher than Nb. The ilmenites reveal slightly concave patterns with the minima near Gd  or  reveal  opposite inclination  similar to garnets but with the elevated LREE part.  The HFSE are rather high an Ta-Nb are higher that Zr Hf Some samples with the high LREE also reveal elevated Th and U, indicating influence of the essentially carbonatitic melts.

It seems that the mantle beneath the Morkoka pipe wre originally depleted but regenerated but the H2O bearing melts possibly rather oxidized and this may be the reason of the rather low diamond grade.  The ilmenites were generated by the essentially carbonatitic protokimberlite melts which passed through the matrix where garnets prevail  Reaction of the maters with the different REE inclination produced concave REE  patterns

Grant RBRF 19- 05-00788
Salinity effects on pressure-based tide gauges in a macro-tidal estuary
Authors: Williams Joanne
Published: March 2021

Estuarine salinity can be highly variable, resulting in significant density variability. So tide-gauges measuring pressure (either directly or as bubblers) can experience salinity-induced pressure variations of up to 1% of their range. They can therefore record depths with up to 1% variability that is not seen in other measurement systems. In most places this is a small effect compared to other sources of varibility but in macro-tidal estuary such as the Severn in the UK it amounts around 10cm difference between high and low tide. This is comparable to levels of accuracy being sought by current surge forecasts.

 

This effect can be seen in neighbouring radar and pressure gauges in the Severn. It could result in spurious seasonal and spring-neap constituents. Elsewhere, similar errors could result related to unusual freshwater river flow in estuarine locations that are usually saline, or unusual saline storm surge in usually freshwater sites. It has implications for assessment of storm surge and multi-hazard forecasting, and accurate calibration of new gauge installations. 

 
Exploring the influence of the North Pacific Ocean Rossby wave sources on interannual variability of summer precipitation and surface temperature over the Northern Hemisphere
Authors: Fuentes-Franco Ramón , Koenigk Torben , Docquier David , Graef Federico , Wyser Klaus
Published: March 2021

The influence of Rossby wave sources (RWS) emitted on the Northeastern Pacific Ocean (NePO) in the Northern Hemisphere during summer is analysed in the ERA5 reanalysis and a large ensemble performed with the EC-Earth3 model. Using extreme years composites of precipitation, surface temperature and geopotential height, we found a causal influence of the Rossby waves generated over the NePO on a global climate response. Both the reanalysis ERA5 and the EC-Earth3 large ensemble show that RWS triggers wave-like patterns arising from the upper troposphere NePO region. We show that an increased Rossby wave sources intensity is related with a) negative temperature anomalies over western North America, b) positive temperature anomalies over eastern North America, c) increased precipitation over Northern Europe during summer and d) sea-ice concentration decrease in the Arctic.  We also show that the North Atlantic plays a very important role hindering or permitting that Rossby waves generated in the Pacific reach the Atlantic and modulate the atmospheric conditions over Europe. Such conditions were found in ERA5 and EC-Earth3 large ensemble during colder and icier conditions over the North Atlantic.
An auspicious landscape: Quantifying transient glacial incision in the Patagonian Andes from ~6 Ma to present
Authors: Willett Chelsea , Ma Keith , Brandon Mark , Hourigan Jeremy , Christeleit Elizabeth , Shuster David
Published: March 2021

The topography, climate, and geology of the central Patagonian Andes provide an auspicious natural laboratory to track long-term rates of erosion in a dynamic mountainous landscape. Herein, we report a mountain-scale record of erosion rates in the central Patagonian Andes from >10 million years (Ma) ago to present, which covers the transition from a fluvial to alpine glaciated landscape. Apatite (U-Th)/He ages of 72 granitic cobbles from alpine glacial deposits show slow erosion before ~6 Ma ago, followed by a two- to three-fold increase in the spatially averaged erosion rate of the source region after the onset of alpine glaciations and a 15-fold increase in the top 25% of the distribution. This transition is followed by a pronounced decrease in erosion rates over the past ~3 Ma. We ascribe the pulse of fast erosion to local deepening and widening of valleys, which are characteristic features of alpine glaciated landscapes. The subsequent decline in local erosion rates may represent a return toward a balance between rock uplift and erosion.
Landscape Records 25 Million Years of Tectonic Evolution at an Oblique Convergent Margin, Marlborough Fault System, New Zealand
Authors: Duvall Alison , Upton Phaedra , Collett Camille , Harbert Sarah , Williams Seth , Flowers Rebecca , Tucker Gregory , Stone John , LaHusen Sean
Published: March 2021

The landscape at the NE end of the South Island, New Zealand, records oblique plate collision over the last 25 million years. Using low-temperature thermochronology, geomorphic analyses, and cosmogenic 10Be data, we document the landscape response to tectonics over long (106) and short (102 – 103) timescales in the Marlborough Fault System (MFS) and related Kaikōura Mountains. Our results indicate two broad stages of landscape evolution that reflect a changing plate boundary through time. In the eastern MFS, Miocene folding above blind thrust faults generated prominent Kaikōura Mountain peaks and formed major transverse rivers early in the plate collision history. By the Pliocene, rotation of the plate boundary led to a transition to dextral strike-slip faulting and widespread uplift that led to cycles of river channel offset, deflection and capture of tributaries draining across active faults, and headward erosion and captures by major transverse rivers within the western MFS. Despite clear evidence of recent rearrangement of the western MFS drainage network, rivers in this region still flow parallel to older faults, rather than along orthogonal traces of younger, active strike-slip faults. Such drainage patterns emphasize the importance of river entrenchment, showing that once rivers establish themselves along a structural grain, their capture or avulsion becomes difficult, even when exposed to new weakening and tectonic strain. Over short timescales (hundreds to thousands of years), apparent catchment-wide average erosion rates derived from 10Be data show an increase from SW to NE, along strike of the Seaward Kaikōura Range. These rates mirror spatial increases in elevation, slope, channel steepness, and coseismic landslides, demonstrating that both landscape and geochronology patterns are consistent with an increase in rock uplift rate toward a subduction front that is presently locked on its southern end. Remarkably, the form of the topography, hillslopes, and rivers across much of the MFS appears to faithfully record the complex and changing tectonic history of a long-lived, oblique convergent plate boundary.
Fast Iterative Filtering: a new, fast and robust decomposition method for nonlinear and nonstationary processes
Authors: Cicone Antonio , Zhou Haomin
Published: March 2021

The analysis of nonlinear and nonstationary processes is, in general, a challenging task.
One way to tackle it is to first decompose the signal into simpler components and then analyze them separately. This is the idea behind the Empirical Mode Decomposition (EMD) method, published originally in 1998. EMD had a big impact in many filed of research as testified by the more than 15300 citations (based on Scopus). However, the mathematical properties of EMD and its generalizations, like the Ensemble EMD, are still under investigation. For this reason an alternative technique, called Iterative Filtering (IF), was proposed in 2009.

In this talk we introduce the IF method and present new insights in its mathematical properties. In particular, we show its robustness to noise, its ability to avoid mode mixing, and its speed up in what is called the Fast Iterative Filtering (FIF).
Both IF and FIF have been extened to handle multivariate and multidimensional data sets, outperforming, in terms of computational time, any alternative method proposed so far in the literature for the decomposition of nonstationary signals.

This is a joint work with H. Zhou (Georgia Tech).
Analyzing an InSAR short-term systematic phase bias with regards to soil moisture and landcover
Authors: Saporta Paloma , Gomba Giorgio , De Zan Francesco
Published: March 2021

This work investigates a systematic phase bias affecting Synthetic Aperture Radar interferograms, in particular at short-term, causing biases in displacement velocity estimates that can reach several mm per year ([1]).
The analysis relies on the processing of a stack of Single Look Complex SAR images; in our case, the stack consists in 184 Sentinel-1 images acquired regularly between 2014 and 2018 and covering the Eastern part of Sicily. A reference phase history is derived using the EMI method (Eigen-decomposition-based Maximum-likelihood estimator of Interferometric phase), which takes advantage of the full sample covariance matrix built out of all the SAR acquisitions at a given pixel. This phase history has been shown to be equivalent to a persistent scatterer’s phase history over our region of interest. We use it to calibrate the direct multilooked interferograms built out of consecutive acquisitions. The short-term phase bias signal thus obtained is analyzed in time and space, making use in addition of ASCAT soil moisture variations and landcover information from the CORINE dataset.
We observe that for certain land classes, the high-frequency part of the signal is correlated with soil moisture variations in both dry and wet seasons. The low-pass trend exhibits strongly seasonal variations, with maxima of comparable value in spring (April-May) of each year. Areas with similar landcover types (forests, vegetated areas, agricultural areas) witness similar phase biases behavior, indicating a physical contribution associated with vegetation effects.
By investigating the behavior of the bias, this study contributes towards a future mitigation of this phase error in deformation estimates, or the exploitation of the bias itself as a physically relevant signal.

[1] H. Ansari, F. De Zan and A. Parizzi, "Study of Systematic Bias in Measuring Surface Deformation With SAR Interferometry," in IEEE Transactions on Geoscience and Remote Sensing, doi: 10.1109/TGRS.2020.3003421.
Synoptic analysis of globally-distributed data sets of cosmogenic-nuclide exposure ages
Authors: Balco Greg
Published: March 2021

This abstract describes a project to make large data sets of cosmogenic-nuclide measurements useable for synoptic global analysis of paleoclimate, glacier change, and landscape change. It is based on the 'ICE-D' (Informal Cosmogenic-nuclide Exposure-age Database), a transparent-middle-layer infrastructure for compiling and storing cosmogenic-nuclide measurements and generating internally consistent exposure-age data. The prototype implementation of this project focuses on a global data set of exposure ages from glacial deposits that are, potentially, useful for synoptic analysis of glacier change and paleoclimate. The aim is to address a number of messy data-management and analysis problems associated with cosmogenic-nuclide data, thus making it possible to apply unbiased, automated quantitative analysis to the entire globally-distributed data set. The presentation will highlight (i) examples of error-tolerant hypothesis testing using this approach; (ii) means of quantifying the importance of the details of cosmogenic-nuclide production-rate calculations to global paleoclimate inferences, and (iii) likewise, approaches to understanding the importance of geomorphic processes and landform evolution to global paleoclimate inferences drawn from exposure-dated landforms.
Spatial Distribution and Key Prevention Areas of Ephemeral Gully under the 'Grain for Green Project' in Loess Plateau, China
Authors: Zhong Yuan , Wang Chunmei , Pang Guowei , Yang Qinke , Guo Zitian , Liu Xin , Su Jianhua
Published: March 2021

Soil erosion is an important threat in the high-quality development of the Loess Plateau of China, and Ephemeral Gully (EG) erosion is an important erosion type. Answering the distribution characteristics of EG at the regional scale is an important basis for EG control. The regional distribution of EG and the areas that still at high risk of EG development after the 'Grain for Green Project' since more than 20 years ago remain poorly understood. This study aimed to solve the above problems by using visual interpretation based on sub-meter Google Earth images in 137 systematically selected small watersheds in the Loess Plateau. The EG density, length, land use of the hillslope where each EG existed, and other parameters were obtained and analyzed using the GIS method. The spatial distribution of EG density, average length, and spatial correlation in the Loess Plateau was explored. The current EG distribution and key prevention areas in the Loess Plateau were identified. The results showed that: (1) EGs were found in 46 surveyed watersheds accounting for 33.6% of the total watershed number, with an EG density average value of 3.41km/km2 and maximum value of 21.92 km/km2. The average number of EG was 60.32/km2. EG length was mainly distributed in 20 ~ 60 m, with an average length of 63.31 m; The critical slope length of EGs was mainly 40 ~ 60 m, with an average 56.20 m. (2) The watersheds with EGs were mainly located in the north-central, the west, and northwest of the Loess Plateau. EG erosion is extremely strong in loess hilly and gully region, and moderate in loess plateau gully region.(3) 38.3% of EG was distributed in cropland; 35.3% distributed in grassland; 22.8% distributed in forest land. After the 'Grain for Green Project', the EGs that were still distributed on cropland were a more important threat to soil erosion and need better prevention efforts. EGs located on cropland were still widely distributed in many areas of Loess Plateau, such as the northwest of Yan 'an City in the middle and upper reaches of Beiluo River, Suide and Luliang in the lower reaches of Wuding River, at the junction of Dingxi and Huining and in Qingyang area. This research would help in a more reasonable distribution of erosion control practices in the Loess Plateau.
Continuous monitoring of SO2 emissions from Sinabung Volcano, Indonesia
Authors: Kunrat Syegi , Alfianti Hilma , Kern Christoph , Primulyana Sofyan , Lerner Allan , Asrori Moh. Nurul , Putra Armen , Al Hidayat Deri
Published: March 2021

After more than 800 years of dormancy, phreatic explosions occurred at Sinabung Volcano in North Sumatra, Indonesia, on August 27, 2010. These marked the beginning of a period of unrest at Sinabung that continues through the present. Phreatic activity temporarily ceased in September 2010, however a more explosive phase of the eruption began again in September 2013, sending ash columns as high as 9 km above the volcano’s summit. A lava dome breached the surface on 17-18 December 2013 and subsequent collapses of this dome have produced numerous pyroclastic density currents reaching up to 5 km from the vent. Eruptive activity has waxed and waned since 2013, and the eruption entered period of especially vigorous activity beginning in February 2019 that is continuing through the present.

Between 2010 and 2013, the Indonesian Center for Volcanology and Geological Hazard Mitigation (CVGHM) significantly ramped up its monitoring efforts at Sinabung by installing seismometers, GPS instruments and electronic distance measuring benchmarks. In August 2016, the volcano observatory then installed a network of 3 scanning Differential Optical Absorption Spectrometers (DOAS) on the eastern side of Sinabung at distances between 4 and 6 km from the volcano’s summit. These DOAS instruments are part of the Network for Observation of Volcanic and Atmospheric Change (NOVAC), and autonomously measure the emission rate of sulfur dioxide (SO2) from Sinabung during typical west-wind conditions.

Since its installation, the DOAS network has provided useful monitoring information at Sinabung. The collected data indicate that the average SO2 emission rate lies between 100 and 400 metric tons per day (t/d), but emissions up to 2,400 t/d are common throughout the measurement period. The maximum emission rate recorded since 2016 was 4,500 t/d, measured in July 2019. However, the NOVAC instruments are not able to accurately capture the SO2 emissions associated with large explosive eruptions, and satellite data indicate that plumes associated with such events have sometimes contained significantly more SO2 than during the more typical passive degassing behavior. Here, we present excerpts of the long-term SO2 data from Sinabung and compare these with complimentary records of the timing and frequency of explosions, gas exhalations, rockfalls, and pyroclastic flows. These combined datasets provide insights into the active volcanic processes ongoing at Sinabung.
Multi-phase seismic source imprint of tropical cyclones
Authors: Retailleau Lise , Gualtieri Lucia
Published: March 2021

The coupling between the ocean activity driven by winds and the solid Earth generates seismic signals recorded by seismometers worldwide. The 2-10 s period band, known as secondary microseism, represents the largest background seismic wavefield. While moving over the ocean, tropical cyclones generate particularly strong and localized sources of secondary microseisms that are detected remotely by seismic arrays.

We assess and compare the seismic sources of P, SV, and SH waves associated with typhoon Ioke during its extra-tropical transition. To understand their generation mechanisms, we compare the observed multi-phase sources with theoretical sources computed with a numerical ocean wave model, and we assess the influence of the ocean resonance (or ocean site effect) and coastal reflection of ocean waves. We show how the location and lateral extent of the associated seismic source is period- and phase-dependent. This information is crucial for the use of body waves for ambient noise imaging and gives insights about the sea state, complementary to satellite data.