bluuebunny/crossref_metadata_2025_split huggingface dataset:
Isolating roughness scales of gravel‐bed patches
Authors: Bertin Stephane , Groom Jane , Friedrich Heide 
Published: July 2017

AbstractThere is a growing consensus that gravel‐bed roughness should be parameterized based on bed‐surface topography, not only sediment size. One benefit is the possible identification of various spatial scales of surface roughness and evaluation of their respective contributions to flow resistance (and also to bedload transport). The absence of relationships between roughness at the different scales is apparent in previous work, which currently limits roughness parameterization from topography and application in flow modeling. This study examines the use of moving‐window detrending on gravel‐bed digital elevation models (DEMs) for isolating roughness scales and their respective signatures. A large data set of 35 water‐worked gravel‐bed patches from both the laboratory and the field was used for the analysis. The measured bed topography was separated into two distinct DEMs: one representing grains, the other representing small bedforms. For all DEMs, bed‐elevation parameters measuring vertical roughness, imbrication, and spatial correlations were determined. Our results show distinct topographic signatures between grain and bedform DEMs. We show strong positive linear relationships between grain vertical roughness and the size of the bed‐surface material. Surface sediment arrangement also determined bedform shape, with groupings of coarse sediment forming humps on the surface, and finer sediment sheltered in hollows. Patch‐scale vertical roughness could not be estimated simply as the sum of grain and bedform vertical roughness. Instead, our results suggest weighted summation and the existence of universal weighting coefficients. Practical applications for studies on gravel‐bed roughness and flow modeling using DEMs are discussed.
Paleothermal structure of the Nankai inner accretionary wedge estimated from vitrinite reflectance of cuttings
Authors: Fukuchi Rina , Yamaguchi Asuka , Yamamoto Yuzuru , Ashi Juichiro 
Published: July 2017

AbstractThe paleothermal structure and tectonic evolution of an accretionary prism is basic information for understanding subduction zone seismogenesis. To evaluate the entire paleotemperature profile of the Integrated Ocean Drilling Program (IODP) Site C0002 located in the off‐Kumano region of the Nankai Trough and penetrate the inner accretionary wedge down to 3058.5 m below the seafloor (mbsf), we performed a vitrinite reflectance analysis for cuttings and core samples during IODP expeditions 338 and 348: Nankai Trough seismogenic zone experiment. Although vitrinite reflectance values (Ro) tend to increase with depth, two reversals of these values suggested the existence of thrust fault zones with sufficient displacements to offset the paleothermal structure. The estimated maximum paleotemperatures are 42–70°C at 1200–1300 mbsf, 44–100°C at 1600–2400 mbsf, and 56–115°C at 2600–3000 mbsf, respectively. These temperatures roughly coincide with estimated modern temperatures; however, at a smaller scale, the reconstructed partial paleogeothermal gradient (∼60–150°C/km) recorded at the hanging‐ and footwall of the presumed thrust fault zone is higher than the modern geothermal gradient (∼30–40°C/km). This high paleogeothermal gradient was possibly obtained prior to subduction, reflecting the large heat flow of the young Philippine Sea Plate.
Lateral heterogeneity imaged by small‐aperture ScS retrieval from the ambient seismic field
Authors: Spica Zack , Perton Mathieu , Beroza Gregory C. 
Published: July 2017

AbstractInterpreting core‐related body wave traveltimes is challenging for seismologists because Earth's heterogeneities are averaged over thousands of kilometers and the sparsity of earthquake measurements makes these heterogeneities difficult to localize. We show how the ambient seismic wave field can be used to overcome these limitations. We present a regional‐scale analysis of core‐mantle boundary reflections (ScS) under Mexico. We show that body wave arrivals (i.e., P and ScS) are retrieved from higher‐order cross correlations (C3), a technique that provides a more uniform and controlled source distribution using the scattered waves of the coda of classical ambient field cross correlations (C1). Then, we extract ScS traveltimes along a dense linear array in Mexico and find that lithospheric lateral heterogeneity, such as the subducting Cocos slab beneath Mexico, may have a strong impact on ScS traveltimes. In parallel, we show that lateral heterogeneity such as a possible ultralow velocity zone (ULVZ) near the core‐mantle boundary might also affect, although to a lesser extent, the traveltime anomalies. Our results and interpretation are supported through numerical simulations that account for slab and ULVZ properties.
Polar cap hot patches: Enhanced density structures different from the classical patches in the ionosphere
Authors: Zhang Q.‐H. , Ma Y.‐Z. , Jayachandran P. T. , Moen J. , Lockwood M. , Zhang Y.‐L. , Foster J. C. , Zhang S.‐R. , Wang Y. , Themens D. R. , Zhang B.‐C. , Xing Z. Y. 
Published: July 2017

AbstractBased on in situ and ground‐based observations, a new type of “polar cap hot patch” has been identified that is different from the classical polar cap enhanced density structure (cold patches). Comparing with the classical polar cap patches, which are transported from the dayside sunlit region with dense and cold plasma, the polar cap hot patches are associated with particle precipitations (therefore field‐aligned currents), ion upflows, and flow shears. The hot patches may have the same order of density enhancement as classical patches in the topside ionosphere, suggesting that the hot patches may be produced by transported photoionization plasma into flow channels. Within the flow channels, the hot patches have low‐energy particle precipitation and/or ion upflows associated with field‐aligned currents and flow shears. Corresponding Global Navigation Satellite System (GNSS) signal scintillation measurements indicate that hot patches may produce slightly stronger radio signal scintillation in the polar cap region than classical patches. A new type of polar cap patches, “polar cap hot patches,” is identified to differentiate enhanced density structures from classical patches. Hot patches are associated with particle precipitations, ion upflows, field‐aligned currents, and shear flows in the polar cap. Hot patches may lead to slightly stronger ionospheric scintillations of GNSS signals in the polar cap region than classical patches.
Ice stream reorganization and glacial retreat on the northwest Greenland shelf
Authors: Newton A. M. W. , Knutz P. C. , Huuse M. , Gannon P. , Brocklehurst S. H. , Clausen O. R. , Gong Y. 
Published: July 2017

AbstractUnderstanding conditions at the grounding‐line of marine‐based ice sheets is essential for understanding ice sheet evolution. Offshore northwest Greenland, knowledge of the Last Glacial Maximum (LGM) ice sheet extent in Melville Bugt was previously based on sparse geological evidence. This study uses multibeam bathymetry, combined with 2‐D and 3‐D seismic reflection data, to present a detailed landform record from Melville Bugt. Seabed landforms include mega‐scale glacial lineations, grounding‐zone wedges, iceberg scours, and a lateral shear margin moraine, formed during the last glacial cycle. The geomorphology indicates that the LGM ice sheet reached the shelf edge before undergoing flow reorganization. After retreat of ~80 km across the outer shelf, the margin stabilized in a mid‐shelf position, possibly during the Younger Dryas (12.9–11.7 ka). The ice sheet then decoupled from the seafloor and retreated to a coast‐proximal position. This landform record provides an important constraint on deglaciation history offshore northwest Greenland.
Evidence for a low bulk crustal density for Mars from gravity and topography
Authors: Goossens Sander , Sabaka Terence J. , Genova Antonio , Mazarico Erwan , Nicholas Joseph B. , Neumann Gregory A. 
Published: July 2017

AbstractKnowledge of the average density of the crust of a planet is important in determining its interior structure. The combination of high‐resolution gravity and topography data has yielded a low density for the Moon's crust, yet for other terrestrial planets the resolution of the gravity field models has hampered reasonable estimates. By using well‐chosen constraints derived from topography during gravity field model determination using satellite tracking data, we show that we can robustly and independently determine the average bulk crustal density directly from the tracking data, using the admittance between topography and imperfect gravity. We find a low average bulk crustal density for Mars, 2582 ± 209 kg m−3. This bulk crustal density is lower than that assumed until now. Densities for volcanic complexes are higher, consistent with earlier estimates, implying large lateral variations in crustal density. In addition, we find indications that the crustal density increases with depth.
The relative contributions of tropical Pacific sea surface temperatures and atmospheric internal variability to the recent global warming hiatus
Authors: Deser Clara , Guo Ruixia , Lehner Flavio 
Published: July 2017

AbstractThe recent slowdown in global mean surface temperature (GMST) warming during boreal winter is examined from a regional perspective using 10‐member initial‐condition ensembles with two global coupled climate models in which observed tropical Pacific sea surface temperature anomalies (TPAC SSTAs) and radiative forcings are specified. Both models show considerable diversity in their surface air temperature (SAT) trend patterns across the members, attesting to the importance of internal variability beyond the tropical Pacific that is superimposed upon the response to TPAC SSTA and radiative forcing. Only one model shows a close relationship between the realism of its simulated GMST trends and SAT trend patterns. In this model, Eurasian cooling plays a dominant role in determining the GMST trend amplitude, just as in nature. In the most realistic member, intrinsic atmospheric dynamics and teleconnections forced by TPAC SSTA cause cooling over Eurasia (and North America), and contribute equally to its GMST trend.
Cloud droplets to drizzle: Contribution of transition drops to microphysical and optical properties of marine stratocumulus clouds
Authors: Glienke S. , Kostinski A. , Fugal J. , Shaw R. A. , Borrmann S. , Stith J. 
Published: July 2017

AbstractAircraft measurements of the ubiquitous marine stratocumulus cloud type, with over 3000 km of in situ data from the Pacific during the Cloud System Evolution in the Trades experiment, show the ability of the Holographic Detector for Clouds (HOLODEC) instrument to smoothly interpolate the small and large droplet data collected with Cloud Droplet Probe and 2DC instruments. The combined, comprehensive instrument suite reveals a surprisingly large contribution in the predrizzle size range of 40–80 μm (transition droplets, or drizzlets), a range typically not measured and assumed to reside in a condensation‐to‐collision minimum between cloud droplet and drizzle modes. Besides shedding light on the onset of collision coalescence, drizzlets are essential contributors to optical and chemical properties because of a substantial contribution to the total surface area. When adjusted to match spatial resolution of spaceborne remote sensing, the missing drizzlets bring in situ measurements to closer agreement with satellite observations.
Kinematics of Mass Transport Deposits revealed by magnetic fabrics
Authors: Weinberger R. , Levi T. , Alsop G. I. , Marco S. 
Published: July 2017

AbstractThe internal deformation and movement directions of Mass Transport Deposits (MTDs) are key factors in understanding the kinematics and dynamics of their emplacement. Although these are relatively easy to recover from well‐bedded sediments, they are more difficult to deduce from massive beds without visible strain markers. In order to test the applicability of using anisotropy of magnetic susceptibility (AMS) to determine MTD movement, we compare AMS fabrics, with structural measurements of visible kinematic indicators. Our case study involves the structural analysis of slumped lake sediments extensively exposed in MTDs within the Dead Sea Basin. Structural analyses of MTDs outcropping for >100 km reveal radial transport directions toward the basin depocenter. We show that the AMS fabrics display the same transport directions as inferred from structural analyses. Based on this similarity, we outline a robust procedure to obtain the transport direction of slumped MTDs from AMS fabrics. Variations in the magnetic fabrics and anisotropies in fold‐thrust systems within the slumps match the various structural domains. We therefore suggest that magnetic fabrics and anisotropy variations in drill cores may reflect internal deformation within the slumps rather than different slumps. Obtaining magnetic fabrics from MTDs provides a viable way to infer the transport directions and internal deformation of MTDs and reconstruct the basin depocenter in ancient settings. The present results also have implications beyond the kinematics of MTDs, as their geometry resembles fold‐thrust systems in other geological settings, scales, and tectonic environments.
Is El Niño really changing?
Authors: Capotondi Antonietta , Sardeshmukh Prashant D. 
Published: July 2017

AbstractEl Niño–Southern Oscillation (ENSO) is the leading mode of tropical Pacific climate variability, with global impacts. Understanding how the statistics of ENSO events may be changing in response to global warming is of great interest and importance for society. A clear detection of such signals in observations has, however, been obscured by large event‐to‐event differences and apparent “regime shifts” such as that of the late 1970s. In particular, despite extensive research, it is not clear to what extent the observed long‐term changes are systemic or random. Here we show using a multicomponent linear inverse modeling technique that statistically significant systemic changes have indeed occurred in ENSO dynamics since the late 1970s and have affected the evolution of El Niño and La Niña events from their embryonic to fully mature stages.
Radial transport of radiation belt electrons in kinetic field‐line resonances
Authors: Chaston C. C. , Bonnell J. W. , Wygant J. R. , Reeves G. D. , Baker D. N. , Melrose D. B. , Cairns Iver H. 
Published: July 2017

AbstractA representative case study from the Van Allen Probes during a geomagnetic storm recovery phase reveals enhanced electron fluxes at intermediate pitch angles over energies from ~100 keV to 5 MeV coincident with broadband low‐frequency electromagnetic waves. The statistical properties of these waves are used to build a model for radial diffusion via drift‐bounce resonances in kinetic Alfvén eigenmodes/kinetic field‐line resonances. Estimated diffusion coefficients indicate timescales for radial transport on the order of hours in storm time events at energies from <100 keV to MeVs over equatorial pitch angles from the edge of the loss cone to nearly perpendicular to the geomagnetic field. The correlation of kinetic resonances with electron depletions and enhancements during storm main phase and recovery, and the rapid diffusion these waves drive, suggests that they may modulate the outer radiation belt.
In situ observations of magnetosonic waves modulated by background plasma density
Authors: Yuan Zhigang , Yu Xiongdong , Huang Shiyong , Wang Dedong , Funsten Herbert O. 
Published: July 2017

AbstractWe report in situ observations by the Van Allen Probe mission that magnetosonic (MS) waves are clearly relevant to the background plasma number density. As the satellite moved across dense and tenuous plasma alternatively, MS waves occurred only in lower density region. As the observed protons with “ring” distributions provide free energy, local linear growth rates are calculated and show that magnetosonic waves can be locally excited in tenuous plasma. With variations of the background plasma density, the temporal variations of local wave growth rates calculated with the observed proton ring distributions show a remarkable agreement with those of the observed wave amplitude. Therefore, the paper provides a direct proof that background plasma densities can modulate the amplitudes of magnetosonic waves through controlling the wave growth rates.
The ion temperature gradient: An intrinsic property of Earth's magnetotail
Authors: Lu San , Artemyev A. V. , Angelopoulos V. , Lin Y. , Wang X. Y. 
Published: July 2017

AbstractAlthough the ion temperature gradient along (XGSM) and across (ZGSM) the Earth's magnetotail, which plays a key role in generating the cross‐tail current and establishing pressure balance with the lobes, has been extensively observed by spacecraft, the mechanism responsible for its formation is still unknown. We use multispacecraft observations and three‐dimensional (3‐D) global hybrid simulations to reveal this mechanism. Using THEMIS (Time History of Events and Macroscale Interactions during Substorms), Geotail, and ARTEMIS (Acceleration, Reconnection, Turbulence and Electrodynamics of Moon's Interaction with the Sun) observations during individual, near‐simultaneous plasma sheet crossings from 10 to 60 RE, we demonstrate that the ion temperature ZGSM profile is bell‐shaped at different geocentric distances. This ZGSM profile is also prevalent in statistics of ~200 THEMIS current sheet crossings in the near‐Earth region. Using 3‐D global hybrid simulations, we show that mapping of the XGSM gradient of ion temperature along magnetic field lines produces such a bell‐shaped profile. The ion temperature mapping along magnetic field lines in the magnetotail enables construction of two‐dimensional distributions of these quantities from vertical (north‐south) spacecraft crossings. Our findings suggest that the ion temperature gradient is an intrinsic property of the magnetotail that should be considered in kinetic descriptions of the magnetotail current sheet. Toward this goal, we use theoretical approaches to incorporate the temperature gradient into kinetic current sheet models, making them more realistic.
Predicting the consequence of natural and chemical dispersion for oil slick size over time
Authors: Zeinstra‐Helfrich Marieke , Koops Wierd , Murk Albertinka J. 
Published: July 2017

AbstractApplication of dispersants aims to enhance the natural dispersion process in order to reduce the size of the slick and the amount of oil at the surface. This study presents an approach for modeling the development of the surface oil slick as a function of the wind speed, oil viscosity, and dispersant application. We modeled the oil slick mass distribution across a transect through the slick over time taking into account the continuous entrainment of oil, resurfacing process of the different oil droplet size classes and horizontal transport. Outcomes show distinctively different oil slick features, depending on how favorable conditions are for dispersion. A large comet‐shaped slick is formed in the case of suboptimal dispersion. Optimal dispersion yields a small surface oil slick, with a large mass of oil suspended. The benefit of dispersants is limited to in conditions with suboptimal natural dispersion, with the exception of extremely unfavorable conditions in which the slick size would be increased. The oil slick length, fraction of oil still floating, lifetime of the slick, and wind drift are highly influenced by wind speed and related mixing conditions, and to a lesser extent by oil properties. In the newly defined “Dispersibility Factor” (DF) the oil slick properties and environmental conditions can be combined into one value that correlates with the simulation outcomes and therefore can be used as an indicator of favorability of natural dispersion and likelihood of added value of chemical dispersion.
Coastal ocean circulation during Hurricane Sandy
Authors: Miles Travis , Seroka Greg , Glenn Scott 
Published: July 2017

AbstractHurricane Sandy (2012) was the second costliest tropical cyclone to impact the United States and resulted in numerous lives lost due to its high winds and catastrophic storm surges. Despite its impacts little research has been performed on the circulation on the continental shelf as Sandy made landfall. In this study, integrated ocean observing assets and regional ocean modeling were used to investigate the coastal ocean response to Sandy's large wind field. Sandy's unique cross‐shelf storm track, large size, and slow speed resulted in along‐shelf wind stress over the coastal ocean for nearly 48 h before the eye made landfall in southern New Jersey. Over the first inertial period (∼18 h), this along‐shelf wind stress drove onshore flow in the surface of the stratified continental shelf and initiated a two‐layer downwelling circulation. During the remaining storm forcing period a bottom Ekman layer developed and the bottom Cold Pool was rapidly advected offshore ∼70 km. This offshore advection removed the bottom Cold Pool from the majority of the shallow continental shelf and limited ahead‐of‐eye‐center sea surface temperature (SST) cooling, which has been observed in previous storms on the MAB such as Hurricane Irene (2011). This cross‐shelf advective process has not been observed previously on continental shelves during tropical cyclones and highlights the need for combined ocean observing systems and regional modeling in order to further understand the range of coastal ocean responses to tropical cyclones.
Synthesis of Allenamides and Structurally Related Compounds by a Gold‐Catalyzed Hydride Shift Process
Authors: Zhao Qing , Gagosz Fabien 
Published: July 2017

AbstractA new procedure for the synthesis of allenamides and structurally related compounds is reported. Under gold catalysis, a series of ynamides possessing a benzyloxy group at the propargylic position were efficiently converted into the corresponding allenamides following a 1,5 hydride shift process. The scope of the reaction was shown to be extremely broad allowing the formation of γ‐mono or γ‐disubstituted allenes possessing various functional groups. Notably, and in contrast to previously reported methods, not only N‐allenyl sulfonamido but also urea, phosphonamido and the rarely studied phthalimido, pyrrolo, indolo and carbazolo derivatives could be readily and efficiently accessed.magnified image
In‐Gel Direct Laser Writing for 3D‐Designed Hydrogel Composites That Undergo Complex Self‐Shaping
Authors: Nishiguchi Akihiro , Mourran Ahmed , Zhang Hang , Möller Martin 
Published: July 2017

AbstractSelf‐shaping and actuating materials inspired by biological system have enormous potential for biosensor, microrobotics, and optics. However, the control of 3D‐complex microactuation is still challenging due to the difficulty in design of nonuniform internal stress of micro/nanostructures. Here, we develop in‐gel direct laser writing (in‐gel DLW) procedure offering a high resolution inscription whereby the two materials, resin and hydrogel, are interpenetrated on a scale smaller than the wavelength of the light. The 3D position and mechanical properties of the inscribed structures could be tailored to a resolution better than 100 nm over a wide density range. These provide an unparalleled means of inscribing a freely suspended microstructures of a second material like a skeleton into the hydrogel body and also to direct isotropic volume changes to bending and distortion motions. In the combination with a thermosensitive hydrogel rather small temperature variations could actuate large amplitude motions. This generates complex modes of motion through the rational engineering of the stresses present in the multicomponent material. More sophisticated folding design would realize a multiple, programmable actuation of soft materials. This method inspired by biological system may offer the possibility for functional soft materials capable of biomimetic actuation and photonic crystal application.