bluuebunny/crossref_metadata_2025 huggingface dataset:
Chlorine in Gale Crater, Mars: comparing data from DAN and APXS instruments onboard the Curiosity rover
Authors: Lisov Denis , Djachkova Maya , Gellert Ralf , Litvak Maxim , Mitrofanov Igor , Nikiforov Sergey
Published: March 2020

The Dynamic Albedo of Neutrons (DAN) experiment onboard the MSL Curiosity rover performs active neutron measurements at the rover’s stops. It produces short pulses of high-energy neutrons and observes the time profile of slowed down neutrons leaking from the subsurface. Due to neutrons’ high penetrating power it is sensitive to the abundance of neutron moderating elements (mostly hydrogen) and neutron capturing elements (most significant are chlorine and iron) in approximately top 60 cm of the subsurface under the rover, a few tons of matter in total. The DAN data processing procedure is based on numerical simulations of neutron propagation, moderation and capture with the MCNPX software package and returns both the model acceptance probability and the best fit estimates for H2O mass fraction and equivalent Cl mass fraction. The latter corresponds to the total neutron absorption of the subsurface assuming a fixed Fe content. If external information on Fe content is available from other measurements, the DAN equivalent Cl mass fraction can be transformed into an estimate of the real Cl mass fraction in the subsurface.

We compare the DAN data on neutron absorption in the subsurface to the data on the Cl and Fe mass fractions on the surface as measured by the APXS instrument in different regions along the Curiosity path. Our analysis shows that the DAN and APXS measurements taken at the same location are in many cases not consistent with each other as the neutron absorption corresponding to the surface concentrations of chlorine and iron measured by APXS is too high to be accepted by the DAN data.

We investigate this finding in several regions along the Curiosity path. E.g., for the Glen Torridon region the DAN neutron absorption level for different measurements corresponds to the average chlorine mass fraction of 0.81% with a standard deviation of 0.18% and with typical measurement uncertainty of 0.10% (assuming the Fe mass fraction measured by APXS), while the chlorine mass fraction measured by APXS is 1.19% on average with a standard deviation of 0.43%. These two distributions are significantly different, and only 22% of the DAN measurements in the Glen Torridon region agree with the APXS-based neutron absorption for the same location.

We discuss several possible causes for this inconsistency, including either differences between Cl abundances in the martian dust particles and in rocks, or differences between Cl content in the very top surface layer and in the subsurface, or possible bias in APXS target selection.
A sedimentary ancient DNA approach to elucidate the Labrador Sea paleoceanography over the last ~130,000 years
Authors: De Schepper Stijn , Ray Jessica Louise , Griem Lisa , Van Nieuwenhove Nicolas , Grant Danielle Magann , Steinsland Kristine , Sandnes Skaar Katrine , Ijaz Umer Zeeshan
Published: March 2020

Long sedimentary ancient DNA (sedaDNA) records from the marine environment are at present a curiosity and their utility in paleoceanographic research is not yet fully explored. Nevertheless, a few studies indicate that this ecogenetic repository represents an untapped source of new information with which paleoclimatic and paleoceanographic variability can be more deeply explored. We have generated a sedaDNA record from a 19.6 m-long sediment core in the Labrador Sea (Eirik Drift, south of Greenland). The record extends from the early Holocene to Marine Isotope Stage 5 (ca. 130,000 years ago), and we characterized several important climatic transitions in this time interval using stable isotope stratigraphy, ice-rafted detritus counts, and dinoflagellate cyst census counts. The primary goal of this investigation was to query the sedaDNA record for a biological indication of the last and penultimate deglaciation, as well as Heinrich events identified between 65,000 and 25,000 years ago. Our metabarcoding strategy targeted a broad diversity of eukaryotic organisms through amplification of the V7 hypervariable region of the small subunit ribosomal RNA (SSU rRNA) gene. The preliminary sedaDNA results indicate that eukaryote ancient DNA is present in all samples investigated, including those dating back to Marine Isotope Stage 5. Furthermore, we identified abundance shifts in Protaspidae (cercozoa), diatoms, dinoflagellates, and marine stramenopiles (amongst others) that may be linked to changes in paleoceanography during the last two deglaciations as well as Heinrich events (HE3, HE4).
Assessing the sensitivity of multi-frequency vegetation optical depth to biomass and canopy moisture content: towards an ecological-oriented evaluation
Authors: Schmidt Luisa , Forkel Matthias , Dorigo Wouter A. , Moesinger Leander , van der Schalie Robin , Yebra Marta , Pugh Thomas A. M.
Published: March 2020

Multi-decadal records of global Vegetation Optical Depth (VOD) derived from spaceborne microwave sensors provide novel opportunities to observe and analyze both the current state as well as the temporal changes of vegetation. Theoretically, VOD is sensitive to the biomass and moisture content of vegetation. Past studies found relations between VOD and leaf area index (LAI), productivity, biomass, and vegetation water status. In addition, VOD has been used to investigate or estimate changes in biomass, vegetation isohydricity, and tree mortality. However, VOD is not directly measured with ground observations and therefore difficult to evaluate. Several VOD products exist that have been retrieved using different satellite sensors, microwave frequencies (e.g. Ku, X, C, and L-bands) and retrieval algorithms. These products show differences in both their temporal (e.g. short-term variability) as well as spatial dynamics (e.g. their relation with LAI). Hence from a user point-of-view, it is difficult to assess which VOD products might be the most suitable for a certain ecological application.

Here we aim to develop and present initial results of an ecological-oriented assessment of several VOD products. Based on the theoretical assumption that VOD is sensitive to vegetation biomass and moisture content, we assess the co-varying sensitivities of high- (Ku, X, C-bands) and low-frequency (L-band) VOD products to biomass and moisture content within a consistent evaluation framework. High-frequency VOD was taken from the recent developed VODCA products and low-frequency VOD from SMAP and SMOS retrievals. Biomass was derived from global above-ground biomass maps and MODIS LAI. Canopy moisture content was estimated from MODIS retrievals.

The first results confirm previous findings that VOD is both sensitive to biomass and moisture content. High-frequency VOD products are mainly sensitive to short-term changes in canopy biomass and moisture content and low frequency VOD to woody biomass. However, we also found that high-frequency VOD shows high sensitivity to aboveground biomass in Savannahs and boreal forests. Also low-frequency VOD includes a clear signal of vegetation moisture that cannot be explained by biomass changes. This suggests that multi-frequency VOD products and estimates of vegetation biomass and moisture content should be integrated and jointly analyzed to provide a consistent picture of ecosystem dynamics.
The age of surface-exposed ice along the northern margin of the Greenland Ice Sheet
Authors: MacGregor Joseph , Fahnestock Mark , Colgan William , Larsen Nicolaj , Kjeldsen Kristian , Welker Jeffrey
Published: March 2020

Each summer, surface melting of the margin of the Greenland Ice Sheet exposes a distinctive visible stratigraphy that is related to past variability in subaerial dust deposition across the accumulation zone and subsequent ice flow toward the margin. Here we map this surface stratigraphy along the northern margin of the ice sheet using mosaicked Sentinel-2 multispectral satellite imagery from the end of the 2019 melt season and finer-resolution WorldView-2/3 imagery for smaller regions of interest. We trace three distinct transitions in apparent dust concentration and the top of a darker basal layer. The three dust transitions have been identified previously as representing late-Pleistocene climatic transitions, allowing us to develop a coarse margin chronostratigraphy for northern Greenland. Substantial folding of late-Pleistocene stratigraphy is observed but uncommon. The oldest conformal surface-exposed ice in northern Greenland is likely located adjacent to Warming Land and may be up to ~55 thousand years old. Basal ice is commonly exposed hundreds of meters from the ice margin and may indicate a widespread frozen basal thermal state. We conclude that the ice margin across northern Greenland offers multiple compelling opportunities to recover paleoclimatically valuable ice relative to previously studied regions in southwestern Greenland.
How the magnetosphere-ionosphere/thermosphere-ground system is coupled by waves
Authors: Song Paul , Tu Jian-Nan
Published: March 2020

We study the polar magnetospheric coupling to the ionosphere/thermosphere and ground system along the field by examining a spectrum of perturbations propagating from the magnetosphere downward. What distinguishes this study from conventional treatments of the magnetosphere-ionosphere/thermosphere system is that our treatment self-consistently includes the responses of the neutrals to the magnetic and plasma velocity perturbations. The thermosphere is coupled to the magnetosphere-ionosphere (M-I) system in a degree that depends on the time scale of the perturbations. There are three major processes that affect the perturbation propagation: damping that reduces the energy flux while producing heating, the neutral-inertia loading that reduces the propagation speed, and reflection which, associated with structures of the ionosphere and thermosphere, reduces the downward energy flux. The damping is stronger in higher frequencies, 10-2~0 Hz for M-I coupling. As a result of reflection, significant energy fluxes of the magnetospheric perturbations cannot reach the lower ionosphere and hence the ground although some heating and energization may occur in the lower ionosphere resulting from the strong damping of high frequency fluctuations. However, the amplitude of the magnetic fluctuations of the transmitted flux into the lower ionosphere can be enhanced in lower frequencies because of the decrease in the propagation speed due to strong neutral-inertia loading. Combining the attenuation and amplitude enhancement effects, the net enhanced amplitudes occur in frequencies less than few Hertz, which may explain the ready observations of PC waves that are enhanced magnetic oscillations in periods from 0.5 sec to 30 min on the ground while little enhancement is observed below this period range. On the other hand, the smallness of the propagation velocity results in very small electric perturbations, forming a magneto-static condition for coupling from the lower ionosphere to the ground in low-frequencies, casting doubts on any ionosphere-ground coupling mechanisms based on static electric field in the lower frequencies.
Non-equilibrium turbulent stresses and sediment transport in the benthic boundary layer of a shallow shelf environment influenced by flow obstruction
Authors: Austin Martin , Lincoln Ben , Walker-Springett Guy
Published: March 2020

The shallow continental shelf is increasingly used to site infrastructure for marine energy conversion and aquaculture. In this shallow typically energetic environment, tides and waves cause significant sediment fluxes, which interact with and are modified by emplaced infrastructure. This contribution presents observational field data to quantify non-equilibrium turbulent stresses caused by an obstruction in a tidal flow and its impact on suspended sediment transport.

Observations of the turbulent properties of the benthic boundary layer (BBL) in an energetic nearshore environment were made over a 4-month period in Cemaes Bay, Anglesey, UK. The area experiences a high energy semi-diurnal tidal regime with a maximum range of 7.5 m. Tidal current velocities were a maximum of 1.1 m s−1 during springs tides and the strength of the tides ensures that the water column was vertically well mixed. An instrumented lander deployed in 13 m depth on a region of flat sand-sheet sampled the turbulent flows in the BBL using a pulse coherent Nortek Aquadopp and a Vector ADV. An Acoustic Backscatter System was mounted coincidently to sample suspended sediment concentrations.

Vertical profiles of mean flow show that during the flood tide an obstruction upstream of the sampling region modified the BBL causing the breakdown of the constant stress layer and a reduction in velocity shear compared to the opposing ebb tide currents. The turbulent dissipation rate computed using the inertial dissipation and structure functions methods illustrate an order of magnitude increase in dissipation and identify a strongly non-equilibrium relationship between turbulent dissipation and production during flood tides, which varies with elevation above the seabed. The non-equilibrium turbulence effects the suspension and transport of seabed sediments by modifying the vertical profile of sediment diffusivity. These effects are quantified and impacts discussed.
A possible mechanism of space stem precursors formation at the negative lightning leader corona streamer burst periphery
Authors: Syssoev Artem , Iudin Dmitry
Published: March 2020

It’s a common knowledge for the spark discharge researches that there are space leaders inside the negative leader streamer zone. They arise from plasma formations of the volume of about 1 cm3 which are called space stems. But there is no any established idea about how space stems form in conditions when the background electric field magnitude inside a negative leader corona is about three times less than the dielectric strength of air. In this study, we propose a new mechanism of space stem precursors (ionization centers, which are capable to generate positive streamers) formation which is based on the joint action of ionization and drifting processes. The most possible location of proposed mechanism realization is the external boundary of the negative corona streamer burst, where electric field strength reaches a maximum value. The process takes place in the presence of strongly inhomogeneous stochastic electric field relief, which is formed by chaotically positioned clusters of negative charge transported to the negative corona streamer burst periphery by the negative streamer heads. The last are emanated from the leader tip during the negative corona streamer burst finishing each step-formation process. The only thing needed for the space stem precursor formation is the increased level of streamer heads spatiotemporal appearance frequency inside the very small area of space, which scale is of the order of a few millimeters. One important conclusion derived from this study is that the relatively strong electric field strength, overabundance of negative charge, and increased level of both reduced electric field and detachment frequency, which accompany ionization center formation, facilitate survival and growth of positive streamers initiated from a space stem precursor. The model is applied to specify the range of conditions, under which space stem precursor genesis is possible, and to analyze times of its formation at the range of altitudes of 0-12 km.

This work was supported by the Russian Science Foundation (project 19-17-00183).
Soil Organic Matter stability along altitudinal gradients in the French Alps
Authors: Poulenard Jérôme , Khedim Norine , Cecillon Lauric , Sailard Amélie , Barré Pierre , Soucémarianadin Laure , Baudin François , Choler Philippe , Thuiller Wilfried
Published: March 2020

High-elevation ecosystems are considered as systems that have accumulated large amounts of organic carbon in their soils over the past millennia. However, there are still large uncertainties about soil organic matter (SOM) stocks and stability in mountain areas . The fate of SOM in alpine environments is particularly questioned in the context of climate change.

The aim of this study was to investigate SOM stocks and biogeochemical characteristics of SOM along altitudinal gradients to decipher their climatic and biogeochemical drivers. To do so, we used the soil samples set of the French ORCHAMP long-term observatory network. ORCHAMP is built around multiple altitudinal gradients (ca. 1000m of elevation gain representative of the pedoclimatic variability of the French Alps. Each gradient is made of 5 to 8 permanent plots distributed regularly each 200 m of elevation, from the valley (1000 m a.s.l.) to the mountain top (until 3000 m a.s.l.). We studied 18 elevational gradients, including 105 soil profiles and 350 soil horizons. The biogeochemical stability of SOM was estimated with Rock-Eval® thermal analysis.

SOM stocks are extremely variable and do not increase with elevation . The size of the thermally labile SOM  pool strongly increases with elevation. The high lability of SOM revealed by Rock-Eval® thermal analysis suggests a generally high vulnerability of SOM to climate change in alpine environments. The mechanisms explaining the maintenance of this SOM pool in alpine environments are still under study. Hypotheses involving complex balances between climate, nature of fresh organic matter, and enzymatic activities will be discussed.

 
Spatio-temporal variability of droughts in Peruvian Andes and associated risks related to ENSO
Authors: Vega-Jacome Fiorella , Fernandez-Palomino Carlos , Lavado-Casimiro Waldo
Published: March 2020

Droughts in Peru are one of the disasters with major losses in economic activities as agriculture or energy production, affecting livelihoods of the population. The occurrence of droughts can be explained by climatic variability of precipitation, where El Niño Southern Oscillation (ENSO) seems to have an important influence. For the first time, this study addresses the spatio-temporal variability, characteristics and trends of droughts in Peruvian Andes for the 1970-2018 period. The regionalization of droughts was performed combining Principal Component Analysis (PCA) and Cluster method, for which the Standardized Precipitation Index (SPI) was used. Finally, a characterization using a trend analysis, correlation with oceanic-atmospheric indices and a drought risk assessment during El Niño Southern Oscillation (ENSO) was performed.

 We found that the spatio-temporal variability of droughts could be best investigated by distinguishing eight homogeneous regions with different regional drought characteristics. Thus, the trend analysis indicates a reduced duration and severity of droughts in the northern Pacific divide and a lower intensity in the south. In addition, the depicted trends seem to indicate increasing droughts in the Altiplano (high plateau) divide. Additionally, considering a decadal analysis of droughts (1970-2010), the number of drought months in the last decade (2000-2010) has reduced in all regions compared to previous decades.

From the drought risk assessment during ENSO, only remarkable results were obtained using the Oceanic Niño Index (ONI). Thus, under positive anomalies of ONI, an increasing risk of droughts was identified in the southern part of the Pacific divide, in the divide of Titicaca and in the south and north of the Amazon divide.
Fine laminated clastic deposits revealing the delay of the deglaciation timing in the High Tatras Mts. (Central Europe) to Early Holocene
Authors: Ramachandran Dhavamani , Pipík Radovan , Chamutiová Timea , Žatková Lucia , Vidhya Marina , Milovský Rastislav , Milovská Stanislava , Starek Dušan , Šurka Juraj , Uhlík Peter , Bitušík Peter , Hamerlík Ladislav , Biroň Adrian
Published: March 2020

The Tatra moraine relief and cosmogenic nuclide dating show glacier stabilizationand the maximum glacier extent in two phases,at26 – 21 ka and at 18 ka followed by a gradual retreat and  a termination of the glaciation during the Bølling/Allerød warming at 14.64 –12.9 ka (Makos etal., 2014). A renewed glaciation within the Younger Dryas (12.9 – 11.5 ka) formed smaller rock glaciers. This retreat was connected with the formation of the morainic, trough and cirque lakes and the beginning of light-grey silt sedimentation dated from 10ka to 16ka cal BP on the northern slopes of the Tatra Mountains and before 10ka cal BP on its southern slopes (Klapyta et al., 2016).

A new paleolimnic research led to a discovery of a cyclic fine laminated deposit in the four Tatra Mts. lakes. The laminae of thickness from 1 to 3 mm are built of couplets of light-coloured coarse detrital and fine dark-coloured laminae. Thicker light coloured laminae occasionally show a gradation ending in dark-coloured laminae. Laminae consist occasionally of low spherical angular grains of sand and gravel fractions, rarely up to size 10 mm which deformed underlying laminae. Light-coloured laminae are predominantly composed of quartz, followed by K-feldspar, plagioclase, mica, and clay-like particles. Dark-coloured laminae consist of clay-size clastic particles. These laminae were formed in cold, oxygen-rich, ultra-oligotrophic, slightly acid conditions in which the chironomids Pseudodiamesa nivosa and Micropsectra radialis-type dominated. We interpret these lamination as varves related to annual glacial melting. Once the valleys were ice-free, varve production stopped and a short deposition period of homogenous silt was replaced by gyttja. The radiometric C14 age dating shows the deglaciation in the Tatra Mts terminated at the beginning of the Early Holocene, around 10ka cal BP – 9ka cal BP.

 

The research was funded by APVV-15-0292 and the project Centre of Excellence for Integrated Research of the Earth's Geosphere, ITMS 26220120064.

 

Klapyta P., Zasadni J., Pociask-Karteczka J., Gajda A., Franczak P., 2016. Late Glacial and Holocene Paleoenvironmental records in the Tatra Mountains, East-Central Europe, based on lake, peat bog and colluvial sedimentary data: A summary review. Quaternary International 415: 126-144.

 

Makos M., Dzierzek J., Nitychoruk J., Zreda M., 2014. Timing of glacier advances and climate in the Tatra Mountains (Western Carpathians) during the Last Glacial Maximum. Quaternary Research 82: 1-13.
How the choice between nodal planes affects the estimate of tsunami hazard of an earthquake
Authors: Bolshakova Anna , Nosov Mikhail , Kolesov Sergey , Nurislamova Gulnaz , Sementsov Kirill
Published: March 2020

Usually tsunami warning is issued if a submarine earthquake is registered of magnitude exceeding a threshold, the value of which varies depending on the region where the earthquake took place and on the earthquake depth. Being simple and fast this approach is characterized by quite a low accuracy in the tsunami run-up heights estimate. The forecast accuracy can be improved if, instead of magnitude, we use the potential energy of the initial elevation in the tsunami source, calculated taking into account the earthquake focal mechanism. Automatic system for estimate of tsunami hazard using focal mechanism (Tsunami Observer, http://ocean.phys.msu.ru/projects/tsunami-observer/) was recently developed and implemented. Focal mechanisms derived from analysis of the recorded seismic waveforms has two possible solutions, i.e. two nodal planes. Short after an earthquake it is not possible to determine automatically which of the nodal planes is in fact the fault plane.

The main purpose of this study is to reveal a difference in estimates of the potential energy of the initial elevation obtained making use of the first (NP1) and the second (NP2) nodal planes. All earthquake data including focal mechanism solutions were extracted from the Bulletin of the International Seismological Centre. Totally we processed nearly 6000 earthquakes Mw>6 occurred within the time period 1976 – 2019. All calculations were performed by means of the Tsunami Observer system. It was established that the potential energy calculated with use of NP1 (ENP1) and NP2 (ENP2) datasets can vary more than an order. However for overwhelming majority of seismic events (96.3%) the difference does not exceed two times, for significant number of events (74.1%) the difference does not exceed 1.2 times. In our presentation, we shall provide detailed description of calculation methods we use and the distribution of the ratio ENP1/ENP2. Also we shall discuss the influence of the focal depth and magnitude on the ratio ENP1/ENP2.

Acknowledgements

This work was supported by the Russian Foundation for Basic Research, projects 19-05-00351, 20-07-01098, 20-35-70038
Retrieval of aerosol single scattering albedo using joint satellite and surface visibility measurements
Authors: Li Jing , Dong Yueming
Published: March 2020

Aerosol single scattering albedo is a critical optical parameter that determines aerosol radiative effect. However, most existing passive satellite sensors such as MODIS and VIIRS only measures the intensity of reflected solar radiation and can only retrieve aerosol optical depth, while aerosol single scattering albedo needs to be assumed in the retrieval algorithm. On the other hand, if aerosol optical depth is known, it would be possible to retrieve aerosol single scattering albedo using satellite sensors.  In this study, we develop a machine learning based algorithm that retrieves aerosol single scattering albedo using joint visibility and satellite measurements. Combined with meteorology variables including relative humidity and boundary layer height, surface visibility can be converted to column aerosol optical depth. Then combining this converted aerosol optical depth with VIIRS measured TOA apparent reflectance, we retrieve aerosol single scattering albedo at over 2000 stations worldwide. The results compare well with AERONET retrieved SSA. However, compared with AERONET, visibility is recorded at every WMO meteorology station and has much more extensive coverage. We also applied our method to surface PM2.5 measurements obtained satisfactory results. Our work provides an aerosol single scattering albedo dataset with extensive coverage over land, which can be used for aerosol radiative forcing calculations and model validation.
Deformation and evolution history of oblique Mozambique margins system
Authors: Roche Vincent , Leroy Sylvie , Guillocheau François , Revillon Sidonie , Dietrich Pierre , Watremez Louise , Lepretre Angélique , Nonn Chloé , Despinois Frank , Vetel William
Published: March 2020

The Gondwana and particularly its south-central part encompassing Africa and Antarctica has recorded a complex rift to drift history during the mid-Jurassic. Large discrepancies between the many kinematic reconstruction models that attempted to reconstruct such an history emphasise the urgent need for a critical reappraisal. Here we combine high-resolution seismic data sets and oil company wells to propose a deformation history and an evolution scenario for the oblique Mozambique margins system from the Davie ridge area to the Agulhas fracture zone through Angoche, Beira High, Limpopo and Natal segments.

Our results indicate large differences in rifting style and magmatism, ranging from wide to narrow rifting associated with restricted and/or widespread magmatic activities (synchronous or post-rift) combined with asymmetric to more symmetrical structures. At first glance, such differences seem to be related to the African mantle plume melting triggering thermal perturbations, but the importance and the influence of inherited lithospheric structures and thick layer of sediments enhancing mantle melt extraction cannot be excluded. We propose a geodynamic model in three main stages for the evolution of the Mozambique margins, from the extension initiation to the seafloor spreading. Stage T1, representing the first extensional event inducing crustal thinning before the Gondwana’s breakup. It is characterized by an E-W extension trend responsible for the formation of a large fault-controlled basin during the Permo-Trias (e.g. Limpopo). Stage T2 is marked by the onset of a mantle plume activity responsible for the Karoo Large Igneous Province formation, from about 186 Ma in a cratonic and belt lithosphere. Stage T2 is defined by NW-SE trending extension leading to mid-Jurassic basins infilling, and to a first onset of oceanic crust from Chron M33 (160 Ma) to Chron M25 (156 Ma), depending on the area. Stage T3 corresponds to the rift continuation with a stress field rotation ranging from NW-SE to N-S, suggesting that Antarctica moved in a SSE direction with respect to Africa after 156 Ma. This change of kinematics is defined for instance, by flower structures occurrences along the Limpopo margin (i.e. Limpopo transform fault zone), and allowed for the deposition of several seaward dipping reflectors. While the Angoche and Beira High margins recorded a period of quiescence, the Limpopo and Astrid ridge areas experienced an episode of uplift and erosion probably related to mantle dynamics (e.g. mantle plume, small-convection due to the difference of thickness of the lithosphere).
Monitoring activities in several caves along a transect stretching from the Adriatic Sea to the Aggtelek Karst (NE-Hungary): trace element and stable isotopic compositions of drip waters and cave carbonates
Authors: Czuppon György , Demény Attila , Bocic Neven , Buzjak Nenad , Kármán Krisztina , Kovács Zsófia , Leél-Össy Szabolcs , John Szilárd , Óvári Mihály , Bottyán Emese
Published: March 2020

Several caves have been monitored along a transect stretching from the Adriatic Sea to the Aggtelek Karst (NE-Hungary) including two caves in Croatia and three caves in Hungary:  1) Cerovacke cave (~25 km far from the sea, Velebit Mt.), 2) Baraceve cave (~70 km far from the sea), 3) Csodabogyós Cave (~320 km far from the sea, Keszthely Mt.), 4) Béke and Baradla Caves (~700 km far from the sea, Aggtelek Karst). The monitoring activities in each caves included microclimate measurements, analyses of the elemental and stable isotope compositions of drip water and precipitation, as well as stable isotope measurements of modern calcite precipitates formed on light bulbs or glass plates.

The stable isotope compositions of the drip waters in all cases (except one) show systematically lower values than those found in amount-weighted annual precipitation suggesting that the source of the infiltrating water dominantly derives from winter precipitation. Moreover, the relative contribution of winter precipitation can vary even within same cave system reflecting also the local morphology of the karst above the cave. The d-excess values of the drip waters show an increasing trend from the Aggtelek Karst towards to Adriatic Sea, showing higher values than 10‰ (Béke-C.: 10.3‰; Csodabogyós-C.: 11‰, Baraceve-C.: 12‰, Cerovacke: 15‰). These observations indicate significant contribution from moisture originated from the Mediterranean Basin to the infiltrating water. The monitoring of the precipitation support these findings as among the marine moisture source the Mediterranean is the most dominant even relative far from the sea.

The trace element systematics in drip waters indicate that PCP likely took place during relatively dry periods. In some caves the change of the hydrological condition affected both the trace element composition of the drip water and the stable isotope composition of the modern calcite precipitates. Although the calcite-water isotope fractionations show significant scatter even within individual caves, the majority of the data fall close to the Coplen (2007) and the Tremaine et al. (2011) fractionation values in both Croatian and Hungarian caves.

The research was supported by the Ministry for Innovation and Technology, the National Research, Development and Innovation Office (project No. PD 121387).
Transport and retention of engineered silver nanoparticles in the presence of phosphorus
Authors: Adrian Yorck , Schneidewind Uwe , Bradford Scott , Simunek Jirka , Klumpp Erwin , Azzam Rafig
Published: March 2020

Nowadays engineered silver nanoparticles (AgNP) are being widely used for a multitude of purposes. At certain times during their life-cycle they might enter soils and freshwater resources and thus recent research has focused on their transport and fate in soils and the vadose zone as well as the saturated zone. AgNP retention in the subsurface depends on a multitude of parameters including the type and shape of the sediments through the nanoparticles are exposed to, the chemical composition of pore and groundwater acting as background solution or the type and quantity of soil organic matter present. One aspect that has received little attention so far is their transport behaviour in the presence of nutrients.

Here we study PVP-AgNP transport and retention in saturated columns containing silicate-dominated aquifer material that is also exposed to orthophosphate (NaH2PO4) or myo-inositol hexakisphosphate (IP6) via the background solution. In particular, we compare PVP-AgNP transport behaviour for different pH (6 and 4.5) in the background solution, for different mass concentrations of sediments <63 µm in the columns (0 and 2%) and in the presence/absence of soil organic matter (SOM). Experimental data were modelled using HYDRUS 1D.

Results of our experiments show that PVP-AgNP exhibit a higher mobility through the columns in the presence of phosphate as the latter can block attachment sites otherwise available to the nanoparticles. In the presence of SOM this mobility is even higher than in the absence of SOM as SOM and phosphate anions are both negatively charged and potentially bound to the same attachment sites. PVP-AgNP mobility also increased for both P-species when an increase in pH occurred but this increase was more pronounced in columns with orthophosphate. Results further show that PVP-AgNP are more mobile in columns with IP6 than orthophosphate in the absence of sediments <63 µm at pH 4.5. However, while for columns with material < 63 µm the overall AgNP mobility is decreased due to an overall increase in sediment surface area, AgNP are more mobile in the presence of orthophosphate as IP6 is more strongly bound to iron and aluminium oxides found in higher abundance in the fine sediments.   
Comparing Wildfire GOES-based Stereo-Plume Heights, Winds, and Aerosol Property from 3D-Wind and MAGARA Algorithms to CMAQ simulations: A 2018 Camp Fire Study
Authors: Friberg Mariel , Zou Yufei , Limbacher James , Wu Dong , Carr James , O’Neill Susan
Published: March 2020

Science Question:  How can we use two new geostationary satellite-based algorithms to constrain wildfire plume modeling simulations?

Method:  Our approach is twofold. Combining NASA’s legacy MODIS products with the GOES Advanced Baseline Imager imagery, the state-of-the-art 3D-Wind algorithm, we first compare satellite-based detected wildfire plume injection heights with CMAQ, a chemical transport model. The validated GOES-MODIS 3D-Wind algorithm provides plume dynamics data with < 200 m vertical resolution for plume height and < 0.5 m/s for plume speed. Secondly, we compare aerosol type observations from the novel Multi-Angle Geostationary Aerosol Research Algorithm (MAGARA) to constrain modeled smoke hotspots and dispersion patterns of aerosols. Consistently modeled meteorology and extensive satellite coverage combine to produce more accurate plume injection heights and dispersion patterns, especially in areas where ground measurements are limited or absent. We compare the results of the two novel algorithms, 3D-Wind and MAGARA, to the 2018 Camp Fire event CMAQ runs. 

Impact:  Geostationary satellite wildfire plume-attribute products provide spatiotemporal context and can decrease errors in plume characterization. 

Why It Matters:  According to the EPA, wildland fires contributed approximately 30 percent of directly emitted fine particulate matter, linked to premature death from heart and lung disease. By capturing the dynamic wildfire plume dispersion, height, and winds, we can determine if fire plumes stay within or shoot above the planetary boundary layer and constrain modeling results. Improved accuracy, coverage, and characterization of plume injection height data increase the effectiveness of management methods that reduce and estimate smoke exposure.
Cloud macrophysical properties from airborne observations during EUREC4A
Authors: Konow Heike , Klingebiel Marcus , Ament Felix
Published: March 2020

Trade wind cumulus clouds are the predominant cloud type over the tropical Atlantic east of the island of Barbados. Parameters describing their macroscopic shape can help characterizing and comparing general features of clouds. This characterizing will indirectly help to constrain estimates of climate sensitivity, because models with different structures of trade wind cumuli feature different response to increased CO2 contents.

Two aircraft campaigns with the HALO (High Altitude LOng range) aircraft took place in the recent past in this region: NARVAL-South (Next-generation Aircraft Remote-Sensing for VALidation studies) in December 2013, during the dry season, and NARVAL2 in August 2016, during the wet season. During these two campaigns, a wide range of cloud regimes from shallow to deep convection were sampled. This past observations are now extended with observations from this year’s measurement campaign EUREC4A, again during the dry season. EUREC4A is endorsed as WCRP capstone experiment and the synergy of four research aircraft, four research vessels and numerous additional observations will provide comprehensive characterizations of trade wind clouds and their environment.

Part of the NARVAL payload on HALO is a 35 GHz cloud radar, which has been deployed on HALO on several missions since 2013. These cloud radar measurements are used to segment individual clouds entities by applying connected component analysis to the radar cloud mask. From these segmented individual clouds, macrophysical parameters are derived to characterize each individual cloud.

This presentation will give an overview of the cloud macrophysics observed from HALO during EUREC4A. Typical macrophysical parameters, i.e. cloud depth, cloud length, cloud fraction, are analyzed. We will relate these to observations from past campaigns and assess the representativeness of EUREC4A. As special focus of the EUREC4A campaign, measurements will be performed during different times of the day to detect diurnal cycles. Macrophysical parameters can be used to characterize changes over the day and cloud scenes of similar clouds types can be identified.
How well does climate model perform for southern Brazil?
Authors: Pereima Maria Fernanda R. , Amorim Pablo B. , Brighenti Tassia M. , Rodrigues Regina R. , Chaffe Pedro Luiz B.
Published: March 2020

Southern Brazil is in a transitional zone between tropical and extratropical climates. The rainfall regime in such transitional zones can be rather sensitive to climate change and related expansion of the tropics in the Southern Hemisphere. It is expected that rainfall will increase up to 30% over this area in the next decades. It is important, however, to investigate if the mechanisms that generate rainfall are simulated correctly in the models to know when downscaling and bias correction methods should be applied. The objective of this study is to evaluate the performance of the CMIP5 climate models in terms of precipitation in southern Brazil. This study addresses fundamental aspects of model evaluation and aims to give guidance on the proper use of climate model outputs for southern Brazil. We use 41 historical climate simulations and 22 RCP8.5 future climate simulations for the periods of 1980-2005 and 2070-2100, respectively. We compare the historical simulations with an interpolated product database obtained from ground stations. To evaluate the model performance regarding its marginal distribution, we use the following metrics: annual rainfall, variance, skewness, dry day fraction, wet day fraction, high percentiles and similarity of distributions (trough Kolmogorov-Smirnov test). There is a negative bias in all of them except for wet day fraction. All metrics of temporal aspects such as Markham’s seasonality index, autocorrelation, time of the annual maxima, dry spell average and maximum lengths, wet spell average and maximum lengths show a positive bias, apart from the time of annual maxima. Overall, annual rainfall is expected to increase in southern Brazil. Spatial patterns of annual rainfall are similar in the RCP 8.5 future pathways to the ones found in the historical period, with wetter areas expanding toward the north. However, the spatial pattern of observed rainfall is not captured by climate models. They simulate smaller volumes of precipitation in the southern border. A similar pattern was found in extreme precipitation, with bias almost twice as large than the one found in annual rainfall. Furthermore, the models do not properly represent the seasonal cycle, the Markham’s seasonality index reached four times the observed in some areas. Given the poor performance in the area, the use of future simulations in impact studies should be done carefully once the direct use of climate model precipitation in hydrological studies could result in misleading conclusions.

This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001
In-situ microseism noise generation measured from distributed acoustic sensing on seafloor optical cable
Authors: Rivet Diane , Guérin Gauthier , Mata Daniel , Lior Itzhak , Sladen Anthony , Ampuero Jean-Paul
Published: March 2020

Measuring seismic and acoustic signals on seafloor telecom cables has proven recently its very high potential for earthquake monitoring but also for beter understanding the interaction between the oceans and the solid earth. A consequence of these interactions is the generation of the primary and secondary microseismic noise on coastal regions and in the deep ocean respectively. These seismic noises that propagate across continents are central to a large fraction of todays' seismic imagery and monitoring campaigns. Compared to previous studies and instrumentation setups, acoustic sensing over oceanic telecom cables offer the unique ability to measure in a very dense manner waves that are generated on the seafloor. We analyse a week long record of ambient noise measurements on the 41.5 km-long seafloor telecom cable offshore Toulon, south of France. At shallow depth, close to the coast, we measure the pressure changes caused by the oceanic gravity waves. The bottom pressure is then compared to an oceanographic buoy located a few kilometers away from the cable. The amplitude and frequency of the pressure are modulated by the gravity waves height and dominant periods. This observation opens the way for a distributed measurement of the oceanic waves characteristics over several kilometers. At depth larger than a 1km, we observe Scholte waves at the ocean-solid earth interface produced by the non-linear interaction of gravity waves. These waves have the double frequency of the gravity waves seen at the coast. We find that the amplitude and frequency change over time, as do the gravity waves observed near the coast. The frequency-wave number decomposition of the signal reveals that the apparent velocity of the Scholte waves does not depend of the azimuth of the fiber. These observations confirm that these deep Scholte waves are secondary microseismic noise, generated locally from the interaction of landward gravity waves with oceanward gravity wave reflected on the coast. Spatially distributed monitoring of the ambient noise wave field at the ocean-solid earth interface provides a better understanding of the noise generation and therefore will allow a better modeling of the ambient noise in the future.
A method for predicting hydrogen and oxygen isotope distributions across a region’s river network using reach-scale environmental attributes
Authors: Dudley Bruce , Yang Jing , Shankar Ude , Graham Scott
Published: March 2020

Long-term isotope values of river water provide information on hydrological flow pathways and atmospheric exchange. However, current development of isotope maps for rivers is limited by methodology that spatially interpolates point measures to entire river networks. Catchment environmental characteristics and structures that affect river water isotope values also affect downstream reaches via flow, but many (such as man-made dams) are no more likely to affect nearby unconnected catchments than distant ones. Hence, geospatial and statistical interpolation methods used to develop isoscapes for precipitation and terrestrial systems may be less appropriate for river networks. We developed a modified ‘water balance’ river isotope mapping method to consider the effects of reach-scale catchment environmental characteristics and applied it across the entire stream network of New Zealand. This network comprises over 600,000 reaches and over 400,000 kilometres of rivers. The method uses national rainfall precipitation isoscapes, a digital elevation layer, a national river water isotope monitoring dataset (currently over 3 years of monthly sampling at 58 sites) and reach scale river environmental databases across the New Zealand river network. δ2H and δ18O isoscapes produced using our method showed improved fit to validation data, compared to a model for which residuals were applied as a correction factor across the river network using ordinary kriging. Hence, we show that a water balance modelling approach can provide a good representation of long-term river water δ2H and δ18O values when combined with a regression-based correction using catchment environmental data.
Using Seismic and Geodetic Observations in a Simultaneous Kinematic Model of the 2019 Ridgecrest, California Earthquakes
Authors: Goldberg Dara , Melgar Diego , Sahakian Valerie , Thomas Amanda , Xu Xiaohua , Crowell Brendan , Geng Jianghui
Published: March 2020

The July 4, 2019 Mw6.4 and subsequent July 6, 2019 Mw7.1 Ridgecrest Sequence earthquakes in California, USA, ruptured orthogonal fault planes in the Little Lake Fault Zone, a low slip rate (1 mm/year) dextral fault zone in the region linking the Eastern California Shear Zone (ECSZ) and Walker Lane. This region is tectonically interesting because it accommodates approximately one fourth of plate boundary motion and has been proposed to be an incipient transform fault system that could eventually become the main tectonic boundary, replacing the San Andreas Fault. Additionally, large ruptures of such low slip rate faults are important to understand from the context of seismic hazard. We investigate the interaction within this fault system and demonstrate a novel kinematic slip method that inverts for both earthquakes simultaneously, allowing us to use Interferometric Synthetic Aperture Radar (InSAR) data that spans both earthquakes, along with seismic (strong-motion accelerometer) and geodetic (high-rate Global Navigation Satellite Systems (GNSS) and GNSS static offset) datasets that recorded each earthquake separately. We also present results of Coulomb stress change modeling to evaluate how the Mw6.4 earthquake may have affected the subsequent Mw7.1 event. Our findings suggest a complex rupture process and interactions between several fault structures, including dynamic and static triggering between splays involved in the July 4th Mw6.4 and July 6th Mw7.1 events. The integration of seismic and geodetic datasets provides constraints on rupture continuation through stepovers, as well as important context for regional models of seismic source characterization and hazard.