bluuebunny/crossref_metadata_2025_split huggingface dataset:
Atlantic Multidecadal Oscillation Modulates the Impacts of Arctic Sea Ice Decline
Authors: Li Fei , Orsolini Yvan J. , Wang Huijun , Gao Yongqi , He Shengping 
Published: February 2018

AbstractThe Arctic sea ice cover has been rapidly declining in the last two decades, concurrent with a shift in the Atlantic Multidecadal Oscillation (AMO) to its warm phase around 1996/1997. Here we use both observations and model simulations to investigate the modulation of the atmospheric impacts of the decreased sea ice cover in the Atlantic sector of the Arctic (AASIC) by the AMO. We find that the AASIC loss during a cold AMO phase induces increased Ural blocking activity, a southeastward‐extended snowpack, and a cold continent anomaly over Eurasia in December through northerly cold air advection and moisture transport from the Arctic. The increased Ural blocking activity and more extended Eurasian snowpack strengthen the upward propagation of planetary waves over the Siberian‐Pacific sector in the lower stratosphere and hence lead to a weakened stratospheric polar vortex and a negative Arctic Oscillation (AO) phase at the surface in February. However, corresponding to the AASIC loss during a warm AMO phase, one finds more widespread warming over the Arctic and a reduced snowpack over Northern Eurasia in December. The stratosphere‐troposphere coupling is suppressed in early winter and no negative AO anomaly is found in February. We suggest that the cold AMO phase is important to regulate the atmospheric response to AASIC decline, and our study provides insight to the ongoing debate on the connection between the Arctic sea ice and the AO.
Transmissivity Changes and Microseismicity Induced by Small‐Scale Hydraulic Fracturing Tests in Crystalline Rock
Authors: Jalali Mohammadreza , Gischig Valentin , Doetsch Joseph , Näf Rico , Krietsch Hannes , Klepikova Maria , Amann Florian , Giardini Domenico 
Published: February 2018

AbstractMultiple meter‐scale hydraulic fracturing (HF) experiments were executed in the crystalline rock at the Grimsel Test Site, Switzerland. The effect of the HF on the rock transmissivity has been quantified with hydraulic tests before and after each HF experiment. We observe transmissivity enhancement of 2 to 3 orders of magnitude and a change in the dominant flow regime after most of the HF tests. From microseismicity induced by the HF, we do not observe a systematic correlation between transmissivity enhancement and event numbers, frequency‐magnitude distribution, or maximum magnitude. However, the radii of hydraulic fractures inferred independently from seismicity clouds and hydraulic responses coincide, implying that slip along fractures is the common underlying mechanism for transmissivity increase and seismicity.
Evaluating Surface Radiation Fluxes Observed From Satellites in the Southeastern Pacific Ocean
Authors: Pinker R. T. , Zhang B. , Weller R. A. , Chen W. 
Published: February 2018

AbstractThis study is focused on evaluation of current satellite and reanalysis estimates of surface radiative fluxes in a climatically important region. It uses unique observations from the STRATUS Ocean Reference Station buoy in a region of persistent marine stratus clouds 1,500 km off northern Chile during 2000–2012. The study shows that current satellite estimates are in better agreement with buoy observations than model outputs at a daily time scale and that satellite data depict well the observed annual cycle in both shortwave and longwave surface radiative fluxes. Also, buoy and satellite estimates do not show any significant trend over the period of overlap or any interannual variability. This verifies the stability and reliability of the satellite data and should make them useful to examine El Niño–Southern Oscillation variability influences on surface radiative fluxes at the STRATUS site for longer periods for which satellite record is available.
Urban Modification of Convection and Rainfall in Complex Terrain
Authors: Freitag B. M. , Nair U. S. , Niyogi D. 
Published: February 2018

AbstractDespite a globally growing proportion of cities located in regions of complex terrain, interactions between urbanization and complex terrain and their meteorological impacts are not well understood. We utilize numerical model simulations and satellite data products to investigate such impacts over San Miguel de Tucumán, Argentina. Numerical modeling experiments show urbanization results in 20–30% less precipitation downwind of the city and an eastward shift in precipitation upwind. Our experiments show that changes in surface energy, boundary layer dynamics, and thermodynamics induced by urbanization interact synergistically with the persistent forcing of atmospheric flow by complex terrain. With urbanization increasing in mountainous regions, land‐atmosphere feedbacks can exaggerate meteorological forcings leading to weather impacts that require important considerations for sustainable development of urban regions within complex terrain.
Fault Rupture Model of the 2016 Gyeongju, South Korea, Earthquake and Its Implication for the Underground Fault System
Authors: Uchide Takahiko , Song Seok Goo 
Published: February 2018

AbstractThe 2016 Gyeongju earthquake (ML 5.8) was the largest instrumentally recorded inland event in South Korea. It occurred in the southeast of the Korean Peninsula and was preceded by a large ML 5.1 foreshock. The aftershock seismicity data indicate that these earthquakes occurred on two closely collocated parallel faults that are oblique to the surface trace of the Yangsan fault. We investigate the rupture properties of these earthquakes using finite‐fault slip inversion analyses. The obtained models indicate that the ruptures propagated NNE‐ward and SSW‐ward for the main shock and the large foreshock, respectively. This indicates that these earthquakes occurred on right‐step faults and were initiated around a fault jog. The stress drops were up to 62 and 43 MPa for the main shock and the largest foreshock, respectively. These high stress drops imply high strength excess, which may be overcome by the stress concentration around the fault jog.
A Case Study of Connection Between Ground Magnetic Field Perturbations and Tail Current Sheet Bursty Flows at X = −60 RE
Authors: Wang Chih‐Ping , Xing Xiaoyan , Liu Yi‐Hsin , Runov Andrei 
Published: February 2018

AbstractWe report the first observations that connect a burst of fast flows and Pi2 fluctuations in the midtail current sheet at X ~ −60 RE with ground magnetic negative bays and Pi2 pulsations at high latitudes near 70°. Both the flow burst and negative bays occurred around midnight and were isolated and lasted for ~10 min. The flow burst had the characteristics of a low‐density plasma bubble. It was moving earthward at ~340 km/s and was accompanied by field‐aligned currents. The timing and equatorward motion of magnetic bays can be accounted for by this earthward moving bubble. Enhanced Pi2 fluctuations were observed within both the bubble and the magnetic bays. Pressure anisotropy with higher parallel pressure was observed associated with the flow burst and was firehose unstable. We discuss firehose instability as one of the possible mechanisms for the Pi2 fluctuations.
CT Identification and Fractal Characterization of 3‐D Propagation and Distribution of Hydrofracturing Cracks in Low‐Permeability Heterogeneous Rocks
Authors: Liu Peng , Ju Yang , Gao Feng , Ranjith Pathegama G. , Zhang Qianbing 
Published: February 2018

AbstractUnderstanding and characterization of the three‐dimensional (3‐D) propagation and distribution of hydrofracturing cracks in heterogeneous rock are key for enhancing the stimulation of low‐permeability petroleum reservoirs. In this study, we investigated the propagation and distribution characteristics of hydrofracturing cracks, by conducting true triaxial hydrofracturing tests and computed tomography on artificial heterogeneous rock specimens. Silica sand, Portland cement, and aedelforsite were mixed to create artificial heterogeneous rock specimens using the data of mineral compositions, coarse gravel distribution, and mechanical properties that were measured from the natural heterogeneous glutenite cores. To probe the effects of material heterogeneity on hydrofracturing cracks, the artificial homogenous specimens were created using the identical matrix compositions of the heterogeneous rock specimens and then fractured for comparison. The effects of horizontal geostress ratio on the 3‐D growth and distribution of cracks during hydrofracturing were examined. A fractal‐based method was proposed to characterize the complexity of fractures and the efficiency of hydrofracturing stimulation of heterogeneous media. The material heterogeneity and horizontal geostress ratio were found to significantly influence the 3‐D morphology, growth, and distribution of hydrofracturing cracks. A horizontal geostress ratio of 1.7 appears to be the upper limit for the occurrence of multiple cracks, and higher ratios cause a single crack perpendicular to the minimum horizontal geostress component. The fracturing efficiency is associated with not only the fractured volume but also the complexity of the crack network.
The Character of South Pole‐Aitken Basin: Patterns of Surface and Subsurface Composition
Authors: Moriarty D. P. , Pieters C. M. 
Published: February 2018

AbstractUsing Moon Mineralogy Mapper data, we characterize surface diversity across the enormous South Pole‐Aitken Basin (SPA) by evaluating the abundance and composition of pyroxenes, which are overwhelmingly the most abundant mafic mineral in the region. Although SPA exhibits significant complexity due to billions of years of geologic processes subsequent to formation, the basin has retained regular patterns of compositional heterogeneity across its structure. Four distinct, roughly concentric zones are defined: (1) a central SPA compositional anomaly, which exhibits a pervasive elevated Ca,Fe‐rich pyroxene abundance; (2) a Mg‐pyroxene annulus, which is dominated by abundant Mg‐rich pyroxenes; (3) a heterogeneous annulus, which exhibits localized pyroxene‐rich areas spatially mixed with feldspathic materials; and (4) the SPA exterior, which is primarily feldspathic. Pyroxene compositions in the heterogeneous annulus are similar to those in the Mg‐pyroxene annulus, and Mg‐rich pyroxenes also underlie the more Ca,Fe‐rich pyroxene surface material across the SPA compositional anomaly. The establishment of these four distinct compositional zones across SPA constrains basin evolution models and serves to guide potential sample return (and other science) targets.
The Effects of H2SO4 on the Mechanical Behavior and Microstructural Evolution of Polycrystalline Ice
Authors: Hammonds Kevin , Baker Ian 
Published: February 2018

AbstractThe Earth's large continental ice sheets contain a variety of naturally occurring impurities, both soluble and insoluble. Understanding how these impurities affect the rheology, intrinsic thermodynamic properties, and fate of these ice sheets is not well understood. To investigate the effects that trace amounts of H2SO4 have on the flow and ductility of polycrystalline ice, a series of mechanical tests were conducted at −6, −10, −12.5, and −20°C using laboratory‐prepared specimens of polycrystalline ice doped with 1–15 ppm of H2SO4. Parallel tests were performed on identical but undoped specimens of polycrystalline ice. Mechanical testing included constant‐load tensile creep tests at an initial stress of 0.75 MPa and compression tests at constant displacement rates with initial strain rates ranging from 1 × 10−6 to 1 × 10−4 s−1. It was found that H2SO4‐doped specimens of ice exhibited faster creep rates in tension and significantly lower peak stresses in compression, when compared to the undoped ice. Postmortem microstructural analyses were performed using cross‐polarized light thin section imaging, X‐ray computed microtomography, Raman spectroscopy, and electron backscatter diffraction. These analyses showed that H2SO4‐doped specimens had a larger grain size at strains ≤15%, and an earlier onset of microcracking at lower strain rates than the undoped ice. Strain‐induced grain boundary migration was found to be the predominant mechanism of recrystallization in both doped and undoped specimens. Further, an aqueous phase of H2SO4 was found to exist at the grain boundaries and triple junctions of the doped ice, which is thought to have significantly contributed toward its reduced viscosity.
Power Flow, Energy Density, and Group/Energy Transport Velocities in Spatially Dispersive Media
Authors: Yaghjian Arthur D. 
Published: February 2018

AbstractElectromagnetic power flow, energy density, and the energy transport velocity that equals the group velocity of a lossless wave packet are straightforwardly derived for the recently formulated electric and magnetic anisotropic representation of spatially dispersive materials or metamaterials. Boundary conditions in spatially dispersive media are used to confirm analytically and numerically the expressions obtained for the power flow and energy density. A long‐standing alternative expression for the energy transport velocity in spatially dispersive media is shown to be invalid. Plausible formulation‐independent definitions of spatial and temporal dispersion for normal modes are proposed in terms of group and phase velocities.
Intrusion of Magmatic Bodies Into the Continental Crust: 3‐D Numerical Models
Authors: Gorczyk Weronika , Vogt Katharina 
Published: February 2018

AbstractMagma intrusion is a major material transfer process in the Earth's continental crust. Yet the mechanical behavior of the intruding magma and its host are a matter of debate. In this study we present a series of numerical thermomechanical simulations on magma emplacement in 3‐D. Our results demonstrate the response of the continental crust to magma intrusion. We observe change in intrusion geometries between dikes, cone sheets, sills, plutons, ponds, funnels, finger‐shaped and stock‐like intrusions, and injection time. The rheology and temperature of the host are the main controlling factors in the transition between these different modes of intrusion. Viscous deformation in the warm and deep crust favors host rock displacement and plutons at the crust‐mantle boundary forming deep‐seated plutons or magma ponds in the lower to middle crust. Brittle deformation in the cool and shallow crust induces cone‐shaped fractures in the host rock and enables emplacement of finger‐ or stock‐like intrusions at shallow or intermediate depth. Here the passage of magmatic and hydrothermal fluids from the intrusion through the fracture pattern may result in the formation of ore deposits. A combination of viscous and brittle deformation forms funnel‐shaped intrusions in the middle crust. Intrusion of low‐density magma may more over result in T‐shaped intrusions in cross section with magma sheets at the surface.
Reply to Comment by Vincent et al.
Authors: Cowgill Eric , Niemi Nathan A. , Forte Adam M. , Trexler Charles C. 
Published: February 2018

Key Points

The Greater Caucasus Basin encompassed a broader region than envisioned by Vincent et al., who disregard Cenozoic shortening
Terminal basin closure occurred when the Greater and Lesser Caucasus collided
Data cited by Vincent et al. document the onset of basin closure by 35 Ma, but do not indicate terminal basin closure at this time
Early Cenozoic Denudation of Central West Britain in Response to Transient and Permanent Uplift Above a Mantle Plume
Authors: Łuszczak K. , Persano C. , Stuart F. M. 
Published: February 2018

AbstractUpwelling mantle plumes beneath continental crust are predicted to produce difficult to quantify, modest uplift and denudation. The contribution of permanent and transient components to the uplift is also difficult to distinguish. A pulse of denudation in Britain in the Early Paleogene has been linked, although with some controversy, with the arrival of the proto‐Iceland mantle plume. In this contribution we show that combining apatite and zircon (U‐Th‐Sm)/He and apatite fission track analyses from central west Britain with numerical modeling clearly identifies a pulse of early Cenozoic denudation. The data indicate that rock uplift and denudation were centered on the northern East Irish Sea Basin and 1.0–2.4 km of rocks were removed during the latest Cretaceous‐early Paleogene. Uplift and erosion appears to have started a few million years before the earliest magmatism in the region. The regional denudation pattern mirrors the distribution of low‐density magmatic rocks that has been imaged in the deep crust. However, the injection of the underplating melt is not enough to account for the total denudation. An additional regional uplift of at least 300 m is required, which is consistent with a transient thermal effect from the hot mantle plume. The rapid exhumation event ceased by ~40 Ma and the data do not require significant Neogene exhumation.
Three‐Dimensional Modeling of Mount Etna Volcano: Volume Assessment, Trend of Eruption Rates, and Geodynamic Significance
Authors: Barreca Giovanni , Branca Stefano , Monaco Carmelo 
Published: February 2018

Abstract3‐D modeling of Mount Etna, the largest and most active volcano in Europe, has for the first time enabled acquiring new information on the volumes of products emitted during the volcanic phases that have formed Mount Etna and particularly during the last 60 ka, an issue previously not fully addressed. Volumes emitted over time allow determining the trend of eruption rates during the volcano's lifetime, also highlighting a drastic increase of emitted products in the last 15 ka. The comparison of Mount Etna's eruption rates with those of other volcanic systems in different geodynamic frameworks worldwide revealed that since 60 ka ago, eruption rates have reached a value near to that of oceanic‐arc volcanic systems, although Mount Etna is considered a continental rift strato‐volcano. This finding agrees well with previous studies on a possible transition of Mount Etna's magmatic source from plume‐related to island‐arc related. As suggested by tomographic studies, trench‐parallel breakoff of the Ionian slab has occurred north of Mount Etna. Slab gateway formation right between the Aeolian magmatic province and the Mount Etna area probably induced a previously softened and fluid‐enriched suprasubduction mantle wedge to flow toward the volcano with consequent magmatic source mixing.
Evidence for the Influence of DE3 Tide on the Occurrence of Equatorial Counterelectrojet
Authors: Singh Dupinder , Gurubaran S. , He Maosheng 
Published: February 2018

AbstractThe long‐term Challenging Minisatellite Payload magnetometer data are analyzed to derive the equatorial counterelectrojet (CEJ) signatures globally over a range of local times. The resultant local time‐longitude map of CEJ occurrence rate shows a strong influence of the diurnal eastward propagating wave number 3 (DE3) nonmigrating tide during July–September months. DE3 is also shown to account for the reduction of CEJ occurrence at certain longitudes. These aspects of DE3 tide‐CEJ relationship have implications for understanding the seasonal and longitudinal variations of CEJ. Observations of zonal winds from the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) Doppler Interferometer instrument on board the TIMED satellite are used to establish these findings.
Very High Frequency Radio Emissions Associated With the Production of Terrestrial Gamma‐Ray Flashes
Authors: Lyu Fanchao , Cummer Steven A. , Krehbiel Paul R. , Rison William , Briggs Michael S. , Cramer Eric , Roberts Oliver , Stanbro Matthew 
Published: February 2018

AbstractRecent studies of the close association between terrestrial gamma‐ray flashes (TGFs) production and simultaneous lightning processes have shown that many TGFs are produced during the initial leader of intracloud flashes and that some low‐frequency (LF) radio emissions may directly come from TGF itself. Measurements of any simultaneous very high frequency (VHF) radio emissions would give important insight into any lightning leader dynamics that are associated with TGF generation, and thus, such measurements are needed. Here we report on coordinated observations of TGFs detected simultaneously by Fermi Gamma‐ray Burst Monitor, two VHF lightning mapping arrays, and Duke ground‐based LF radio sensors to investigate more on the close association between TGFs and LF and VHF radio emissions. Three TGFs are analyzed here and confirm previous findings on the close association between TGF generation and lightning processes and, for the first time, provide time‐aligned measurements of the VHF radio signature within a few tens of microseconds of TGF generation. Strong VHF emissions were observed essentially simultaneously with two TGFs and within a few tens of microseconds of a third TGF. Equally importantly, the VHF measurement details indicate that the TGF‐associated emissions are nonimpulsive and extended in time. We conclude that the TGF‐producing process is at least sometimes closely associated with strong VHF emissions, and thus, there may be a link between the generation of TGFs and active lightning streamer dynamics.
A Framework to Study Mixing Processes in the Marine Boundary Layer Using Water Vapor Isotope Measurements
Authors: Benetti M. , Lacour J.‐L. , Sveinbjörnsdóttir A. E. , Aloisi G. , Reverdin G. , Risi C. , Peters A. J. , Steen‐Larsen H. C. 
Published: February 2018

AbstractWe propose a framework using water vapor isotopes to study mixing processes in the marine boundary layer (MBL) during quiescent conditions, where we expect evaporation to contribute to the moisture budget. This framework complements the existing models, by taking into account the changing isotopic composition of the evaporation flux (δe), both directly in response to the mixing and indirectly in response to mixing and surface conditions through variations in MBL humidity. The robustness of the model is demonstrated using measurements from the North Atlantic Ocean. This shows the importance of considering the δe variability simultaneous to the mixing of the lower free troposphere to the MBL, to simulate the MBL water vapor, whereas a mixing model using a constant δe fails to reproduce the data. The sensitivity of isotope observations to evaporation and shallow mixing further demonstrates how these observations can constrain uncertainties associated with these key processes for climate feedback predictions.
Nondestructive Optical Toxicity Assays of 3D Liver Spheroids with Optical Coherence Tomography
Authors: Martucci Nicole J. , Morgan Katie , Anderson Graham W. , Hayes Peter C. , Plevris John N. , Nelson Leonard J. , Bagnaninchi Pierre O. 
Published: February 2018

AbstractDrug‐induced liver injury (DILI) is the leading cause of failure in preclinical drug development and withdrawals. Given the central role of the liver in drug metabolism and detoxification, strong incentives exist to create new physiologically relevant, human‐based, 3D in vitro liver models which will offer better prediction of DILI. However, most cell metabolic assays are designed for 2D culture and are not always suitable to assess 3D cultures; in addition, there is an emerging need to develop novel nondestructive assays to assess cell activity in a time‐lapse fashion. In this study, optical coherence tomography (OCT) is used to measure the viability on 3D liver spheroids after acetaminophen exposure used as a model of DILI. Using HepaRG cells, 3D liver spheroids are grown simultaneously to the conventional 2D DILI model for 9 d and are exposed to 5, 10, 20, and 40 × 10−3
m acetaminophen for 24 h. It is shown that OCT can image noninvasively, and label free, the cell metabolic activity, thus enabling the assessment of viability of the 3D spheroids. This correlates well with cellular metabolic activity measured by biochemical assays. This method is translatable to any 3D tissue model and can be performed using any commercial OCT system.