bluuebunny/crossref_metadata_2025_split huggingface dataset:
East Asian Winter Monsoon Variations and Their Links to Arctic Sea Ice During the Last Millennium, Inferred From Sea Surface Temperatures in the Okinawa Trough
Authors: Li Dongling , Li Tiegang , Jiang Hui , Björck Svante , Seidenkrantz Marit‐Solveig , Zhao Meixun , Sha Longbin , Knudsen Karen Luise 
Published: January 2018

AbstractThe East Asian winter monsoon (EAWM) significantly impacts living conditions in a large part of Asia, and therefore, it is important to understand its major driving mechanisms. Winter sea surface temperature (SSTW) and circulation in the southern Okinawa Trough are today both primarily controlled by the EAWM. Here we present a new SSTW reconstruction for the last millennium based on a diatom record from sediment core MD05‐2908, from the continental slope of the southern Okinawa Trough off northeastern Taiwan. Our reconstruction indicates that SSTW varied between 14.1 and 19.6°C over the past 1,000 years. Changes in SSTW in the southern Okinawa Trough correspond closely to the index of warm winters based on historical documents from the East Asian monsoon domain. This implies that our SSTW record can be used to reconstruct EAWM variability during the last millennium. Comparisons with the reconstructed winter Arctic Oscillation (AO, developed from historical snow anomaly events in Eastern Asia) and Arctic sea ice cover reveal a significant positive correlation between the EAWM and AO during the time interval from 1000–1400 Common Era (C.E.), coinciding with reduced sea ice cover. However, there is no significant correlation with increased sea ice cover during the interval from 1400 to 1700 C.E. This suggests that the reduction in Arctic sea ice may periodically have played a role in strengthening the relationship between the EAWM and the AO during the last millennium and that the current and future reduction in Arctic sea ice may have significant consequences for the EAWM.
Non‐CO2 Greenhouse Gas Emissions in China 2012: Inventory and Supply Chain Analysis
Authors: Zhang Bo , Zhang Yaowen , Zhao Xueli , Meng Jing 
Published: January 2018

AbstractReliable inventory information is critical in informing emission mitigation efforts. Using the latest officially released emission data, which is production based, we take a consumption perspective to estimate the non‐CO2 greenhouse gas (GHG) emissions for China in 2012. The non‐CO2 GHG emissions, which cover CH4, N2O, HFCs, PFCs, and SF6, amounted to 2003.0 Mt. CO2‐eq (including 1871.9 Mt. CO2‐eq from economic activities), much larger than the total CO2 emissions in some developed countries. Urban consumption (30.1%), capital formation (28.2%), and exports (20.6%) derived approximately four fifths of the total embodied emissions in final demand. Furthermore, the results from structural path analysis help identify critical embodied emission paths and key economic sectors in supply chains for mitigating non‐CO2 GHG emissions in Chinese economic systems. The top 20 paths were responsible for half of the national total embodied emissions. Several industrial sectors such as Construction, Production and Supply of Electricity and Steam, Manufacture of Food and Tobacco and Manufacture of Chemicals, and Chemical Products played as the important transmission channels. Examining both production‐ and consumption‐based non‐CO2 GHG emissions will enrich our understanding of the influences of industrial positions, final consumption demands, and trades on national non‐CO2 GHG emissions by considering the comprehensive abatement potentials in the supply chains.
Pore Pressure Pulse Drove the 2012 Emilia (Italy) Series of Earthquakes
Authors: Pezzo Giuseppe , De Gori Pasquale , Lucente Francesco Pio , Chiarabba Claudio 
Published: January 2018

AbstractThe 2012 Emilia earthquakes sequence is the first debated case in Italy of destructive event possibly induced by anthropic activity. During this sequence, two main earthquakes occurred separated by 9 days on contiguous thrust faults. Scientific commissions engaged by the Italian government reported complementary scenarios on the potential trigger mechanism ascribable to exploitation of a nearby oil field. In this study, we combine a refined geodetic source model constrained by precise aftershock locations and an improved tomographic model of the area to define the geometrical relation between the activated faults and investigate possible triggering mechanisms. An aftershock decay rate that deviates from the classical Omori‐like pattern and Vp/Vs changes along the fault system suggests that natural pore pressure pulse drove the space‐time evolution of seismicity and the activation of the second main shock.
Electron Crescent Distributions as a Manifestation of Diamagnetic Drift in an Electron‐Scale Current Sheet: Magnetospheric Multiscale Observations Using New 7.5 ms Fast Plasma Investigation Moments
Authors: Rager A. C. , Dorelli J. C. , Gershman D. J. , Uritsky V. , Avanov L. A. , Torbert R. B. , Burch J. L. , Ergun R. E. , Egedal J. , Schiff C. , Shuster J. R. , Giles B. L. , Paterson W. R. , Pollock C. J. , Strangeway R. J. , Russell C. T. , Lavraud B. , Coffey V. N. , Saito Y. 
Published: January 2018

AbstractWe report Magnetospheric Multiscale observations of electron pressure gradient electric fields near a magnetic reconnection diffusion region using a new technique for extracting 7.5 ms electron moments from the Fast Plasma Investigation. We find that the deviation of the perpendicular electron bulk velocity from E × B drift in the interval where the out‐of‐plane current density is increasing can be explained by the diamagnetic drift. In the interval where the out‐of‐plane current is transitioning to in‐plane current, the electron momentum equation is not satisfied at 7.5 ms resolution.
Recent Changes in Global Photosynthesis and Terrestrial Ecosystem Respiration Constrained From Multiple Observations
Authors: Li Wei , Ciais Philippe , Wang Yilong , Yin Yi , Peng Shushi , Zhu Zaichun , Bastos Ana , Yue Chao , Ballantyne Ashley P. , Broquet Grégoire , Canadell Josep G. , Cescatti Alessandro , Chen Chi , Cooper Leila , Friedlingstein Pierre , Le Quéré Corinne , Myneni Ranga B. , Piao Shilong 
Published: January 2018

AbstractTo assess global carbon cycle variability, we decompose the net land carbon sink into the sum of gross primary productivity (GPP), terrestrial ecosystem respiration (TER), and fire emissions and apply a Bayesian framework to constrain these fluxes between 1980 and 2014. The constrained GPP and TER fluxes show an increasing trend of only half of the prior trend simulated by models. From the optimization, we infer that TER increased in parallel with GPP from 1980 to 1990, but then stalled during the cooler periods, in 1990–1994 coincident with the Pinatubo eruption, and during the recent warming hiatus period. After each of these TER stalling periods, TER is found to increase faster than GPP, explaining a relative reduction of the net land sink. These results shed light on decadal variations of GPP and TER and suggest that they exhibit different responses to temperature anomalies over the last 35 years.
Electromagnetic Ion Cyclotron Waves Detected by Kaguya and Geotail in the Earth's Magnetotail
Authors: Nakagawa Tomoko , Nishino Masaki N. , Tsunakawa Hideo , Takahashi Futoshi , Shibuya Hidetoshi , Shimizu Hisayoshi , Matsushima Masaki , Saito Yoshifumi 
Published: January 2018

AbstractNarrowband electromagnetic ion cyclotron waves first discovered by the Apollo 15 and 16 Lunar Surface Magnetometers were surveyed in the magnetic field data obtained by the Kaguya satellite at an altitude of ∼100 km above the Moon in the tail lobe and plasma sheet boundary layer of the Earth's magnetosphere. The frequencies of the waves were typically 0.7 times the local proton cyclotron frequency, and 75% of the waves were left hand polarized with respect to the background magnetic field. They had a significant compressional component and comprised several discrete packets. They were detected on the dayside, nightside, and above the terminator of the Moon, irrespective of the lunar magnetic anomaly, or the magnetic connection to the lunar surface. The waves with the same characteristics were detected by Geotail in the absence of the Moon in the magnetotail. The most likely energy source of the electromagnetic ion cyclotron waves is the ring beam ions in the plasma sheet boundary layer.
Field‐Aligned GPS Scintillation: Multisensor Data Fusion
Authors: Mrak Sebastijan , Semeter Joshua , Hirsch Michael , Starr Gregory , Hampton Don , Varney Roger H. , Reimer Ashton S. , Swoboda John , Erickson Philip J. , Lind Frank , Coster Anthea J. , Pankratius Victor 
Published: January 2018

AbstractThe Mahali Global Positioning System (GPS) array (9 receivers, 15–30 km baseline distance) in central Alaska has probed auroral structures in a field‐aligned direction during a geomagnetic substorm on 7 October 2015. We present results from a collaborative study of GPS phase scintillation, optical emission brightness, and ionospheric density perturbations, by virtue of data fusion procedure from the Mahali GPS array, all‐sky imager (ASI), and the Poker Flat Incoherent Scatter Radar (PFISR). First, we present observations in a traditional way using colocated GPS‐ASI sensors, giving us a principal pattern of the phase scintillation with respect to auroral brightness, free of any mapping ambiguities. Next, we use an assumption that the plasma irregularities are located at an altitude of 120 km, we map the optical data to this altitude, and we extend the GPS‐ASI study over the entire field of view of the GPS receiver array. We obtain a repeatable and persuasive pattern, revealing that GPS phase scintillation is clustered at the auroral edges. Moreover, investigation of the colinear ISR observations supports the altitude assumption of scintillation producing irregularities, and PFISR‐derived electric field estimates suggest that the source for irregularities is gradient drift instability. The phase scintillation was observed on all GPS receivers, phase scintillation exceeded once cycle during several electrojet intensifications, and several events lasted for more than a minute. Finally, phase scintillation was observed during all surge events, independent of the particular auroral morphology.
Spatial Distribution and Semiannual Variation of Cold‐Dense Plasma Sheet
Authors: Bai Shichen , Shi Quanqi , Tian Anmin , Nowada Motoharu , Degeling Alexander W. , Zhou Xu‐Zhi , Zong Qiu‐Gang , Rae I. Jonathan , Fu Suiyan , Zhang Hui , Pu Zuyin , Fazakerly Andrew N. 
Published: January 2018

AbstractThe cold‐dense plasma sheet (CDPS) plays an important role in the entry process of the solar wind plasma into the magnetosphere. Investigating the seasonal variation of CDPS occurrences will help us better understand the long‐term variation of plasma exchange between the solar wind and magnetosphere, but any seasonal variation of CDPS occurrences has not yet been reported in the literature. In this paper, we investigate the seasonal variation of the occurrence rate of CDPS using Geotail data from 1996 to 2015 and find a semiannual variation of the CDPS occurrences. Given the higher probability of solar wind entry under stronger northward interplanetary magnetic field (IMF) conditions, 20 years of IMF data (1996–2015) are used to investigate the seasonal variation of IMF Bz under northward IMF conditions. We find a semiannual variation of IMF Bz, which is consistent with the Russell‐McPherron (R‐M) effect. We therefore suggest that the semiannual variation of CDPS may be related to the R‐M effect.
Electromagnetic Ion Cyclotron Wavefields in a Realistic Dipole Field
Authors: Denton R. E. 
Published: January 2018

AbstractThe latitudinal distribution and properties of electromagnetic ion cyclotron (EMIC) waves determine the total effect of those waves on relativistic electrons. Here we describe the latitudinal variation of EMIC waves simulated self‐consistently in a dipole magnetic field for a plasmasphere or plume‐like plasma at geostationary orbit with cold H+, He+, and O+ and hot protons with temperature anisotropy. The waves grow as they propagate away from the magnetic equator to higher latitude, while the wave vector turns outward radially and the polarization becomes linear. We calculate the detailed wave spectrum in four latitudinal ranges varying from magnetic latitude (MLAT) close to 0° (magnetic equator) up to 21°. The strongest waves are propagating away from the magnetic equator, but some wave power propagating toward the magnetic equator is observed due to local generation (especially close to the magnetic equator) or reflection. The He band waves, which are generated relatively high up on their dispersion surface, are able to propagate all the way to MLAT = 21°, but the H band waves experience frequency filtering, with no equatorial waves propagating to MLAT = 21° and only the higher‐frequency waves propagating to MLAT = 14°. The result is that the wave power averaged k∥, which determines the relativistic electron minimum resonance energy, scales like the inverse of the local magnetic field for the He mode, whereas it is almost constant for the H mode. While the perpendicular wave vector turns outward, it broadens. These wavefields should be useful for simulations of radiation belt particle dynamics.
On the Acceleration and Anisotropy of Ions Within Magnetotail Dipolarizing Flux Bundles
Authors: Zhou Xu‐Zhi , Runov Andrei , Angelopoulos Vassilis , Artemyev Anton V. , Birn Joachim 
Published: January 2018

AbstractDipolarizing flux bundles (DFBs), earthward propagating structures with enhanced northward magnetic field Bz, are usually believed to carry a distinctly different plasma population from that in the ambient magnetotail plasma sheet. The ion distribution functions within the DFB, however, have been recently found to be largely controlled by the ion adiabaticity parameter κ in the ambient plasma sheet outside the DFB. According to these observations, the ambient κ values of 2–3 usually correspond to a strong perpendicular anisotropy of suprathermal ions within the DFB, whereas for lower κ values the DFB ions become more isotropic. Here we utilize a simple, test particle model to explore the nature of the anisotropy and its dependence on the ambient κ values. We find that the anisotropy originates from successive ion reflections and reentries to the DFB, during which the ions are consecutively accelerated in the perpendicular direction by the DFB‐associated electric field. This consecutive acceleration may be interrupted, however, when magnetic field lines are highly curved in the ambient plasma sheet. In this case, the ion trajectories become stochastic outside the DFB, which makes the reflected ions less likely to return to the DFB for another cycle of acceleration; as a consequence, the perpendicular ion anisotropy does not appear. Given that the DFB ions are a free energy source for instabilities when they are injected toward Earth, our simple model (that reproduces most observational features on the anisotropic DFB ion distributions) may shed new lights on the coupling process between magnetotail and inner magnetosphere.
The Mechanism and Dynamics of N‐S Rifting in Southern Tibet: Insight From 3‐D Thermomechanical Modeling
Authors: Pang Yajin , Zhang Huai , Gerya Taras V. , Liao Jie , Cheng Huihong , Shi Yaolin 
Published: January 2018

AbstractN‐S trending rifts are widely distributed in southern Tibet, suggesting that this region is under E‐W extension, behind the N‐S collision between the Eurasia and India plates. Geophysical anomalies and Miocene magma extrusions indicate the presence of dispersed weak zones in the middle to lower crust in southern Tibet. These weak zones are partially located underneath the N‐S rifting systems. In order to study the formation of rifts in collision zones, we have developed a high‐resolution 3‐D thermomechanical model of continental lithosphere with bidirectional compressional‐extensional deformation, and spatially localized weak and low‐density zones in the middle to lower crust. Our numerical experiments systematically reproduce the development of N‐S trending rifts. Model results reveal that the weak middle to lower crust triggers the development of normal faults in the upper crust and surface uplift, whereas regions without such weak layer or with small‐scale weak zones are characterized by strike‐slip faulting. Geodynamic properties (density, depth, and geometry) of the weak middle to lower crust and Moho temperature notably influence the rifting pattern. In addition, rifting formation is critically controlled by large E‐W extension, with the ratio of extensional to compressional strain rate larger than 1.5 in the model with continuous weak middle crust. Our simulated rifting patterns correlate well with the observations in southern Tibet; we conclude that a combination of the bidirectional compression‐extension and the presence of locally weak middle to lower crust triggered the development of the rifting systems in southern Tibet.
Poisson's Ratio and Auxetic Properties of Natural Rocks
Authors: Ji Shaocheng , Li Le , Motra Hem Bahadur , Wuttke Frank , Sun Shengsi , Michibayashi Katsuyoshi , Salisbury Matthew H. 
Published: January 2018

AbstractHere we provide an appraisal of the Poisson's ratios (υ) for natural elements, common oxides, silicate minerals, and rocks with the purpose of searching for naturally auxetic materials. The Poisson's ratios of equivalently isotropic polycrystalline aggregates were calculated from dynamically measured elastic properties. Alpha‐cristobalite is currently the only known naturally occurring mineral that has exclusively negative υ values at 20–1,500°C. Quartz and potentially berlinite (AlPO4) display auxetic behavior in the vicinity of their α‐β structure transition. None of the crystalline igneous and metamorphic rocks (e.g., amphibolite, gabbro, granite, peridotite, and schist) display auxetic behavior at pressures of >5 MPa and room temperature. Our experimental measurements showed that quartz‐rich sedimentary rocks (i.e., sandstone and siltstone) are most likely to be the only rocks with negative Poisson's ratios at low confining pressures (≤200 MPa) because their main constituent mineral, α‐quartz, already has extremely low Poisson's ratio (υ = 0.08) and they contain microcracks, micropores, and secondary minerals. This finding may provide a new explanation for formation of dome‐and‐basin structures in quartz‐rich sedimentary rocks in response to a horizontal compressional stress in the upper crust.
Underestimation of Microearthquake Size by the Magnitude Scale of the Japan Meteorological Agency: Influence on Earthquake Statistics
Authors: Uchide Takahiko , Imanishi Kazutoshi 
Published: January 2018

AbstractMagnitude scales based on the amplitude of seismic waves, including the Japan Meteorological Agency magnitude scale (Mj), are commonly used in routine processes. The moment magnitude scale (Mw), however, is more physics based and is able to evaluate any type and size of earthquake. This paper addresses the relation between Mj and Mw for microearthquakes. The relative moment magnitudes among earthquakes are well constrained by multiple spectral ratio analyses. The results for the events in the Fukushima Hamadori and northern Ibaraki prefecture areas of Japan imply that Mj is significantly and systematically smaller than Mw for microearthquakes. The Mj‐Mw curve has slopes of 1/2 and 1 for small and large values of Mj, respectively; for example, Mj = 1.0 corresponds to Mw = 2.0. A simple numerical simulation implies that this is due to anelastic attenuation and the recording using a finite sampling interval. The underestimation affects earthquake statistics. The completeness magnitude, Mc, for magnitudes lower than which the magnitude‐frequency distribution deviates from the Gutenberg‐Richter law, is effectively lower for Mw than that for Mj, by taking into account the systematic difference between Mj and Mw. The b values of the Gutenberg‐Richter law are larger for Mw than for Mj. As the b values for Mj and Mw are well correlated, qualitative argument using b values is not affected. While the estimated b values for Mj are below 1.5, those for Mw often exceed 1.5. This may affect the physical implication of the seismicity.
High‐Resolution Rayleigh Wave Group Velocity Variation Beneath Greenland
Authors: Pourpoint Maeva , Anandakrishnan Sridhar , Ammon Charles J. 
Published: January 2018

AbstractWe present a high‐resolution group velocity model of Greenland from the analysis of fundamental mode Rayleigh waves. Regional and teleseismic events recorded by the Greenland Ice Sheet Monitoring Network seismic network were used and we developed a group velocity correction method to estimate the dispersion within our region of study. The global dispersion model GDM52 from Ekström (2011, https://doi.org/10.1111/j.1365‐246X.2011.05225.x) was used to calculate group delays from the earthquake to the boundaries of our study area. An iterative reweighted generalized least squares approach was then used to invert for the regional group velocity variations between periods of 25 s and 180 s. The group delay correction method helps alleviate the limitations of the sparse Greenland seismic network in a region with poor seismicity. Both the ray coverage and resolution of our model are significantly better than similar studies of Greenland using two‐station methods. Spike tests suggest that features as small as 200 km can be resolved across Greenland. Our dispersion maps are consistent with previous studies and reveal many signatures of known geologic features including known sedimentary basins in Baffin Bay, the West and East Greenland flood basalt provinces, the East and South Greenland Archean blocks. Our model also contains two prominent features: a deep high‐velocity anomaly extending from northwestern to southwestern Greenland that could be the signature of a cratonic root and a low‐velocity anomaly in central eastern Greenland that correlates with the Icelandic plume track and could be associated with lithospheric thinning and upwelling of hot asthenosphere material.
Directional Wave Spectra Observed During Intense Tropical Cyclones
Authors: Collins C. O. , Potter H. , Lund B. , Tamura H. , Graber H. C. 
Published: January 2018

AbstractTwo deep‐sea moorings were deployed 780 km off the coast of southern Taiwan for 4–5 months during the 2010 typhoon season. Directional wave spectra, wind speed and direction, and momentum fluxes were recorded on two Extreme Air‐Sea Interaction buoys during the close passage of Severe Tropical Storm Dianmu and three tropical cyclones (TCs): Typhoon Fanapi, Super Typhoon Megi, and Typhoon Chaba. Conditions sampled include significant wave heights up to 11 m and wind speeds up to 26 m s−1. Details varied for large‐scale spectral structure in frequency and direction but were mostly bimodal. The modes were generally composed of a swell system emanating from the most intense storm region and local wind‐seas. The peak systems were consistently young, meaning actively forced by winds, when the storms were close. During the peaks of the most intense passages—Chaba at the northern mooring and Megi at the southern—the bimodal seas coalesced. During Chaba, the swell and wind‐sea coupling directed the high frequency waves and the wind stress away from the wind direction. A spectral wave model was able reproduce many of the macrofeatures of the directional spectra.