bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Influence of Io's 2015 Volcanic Activity on Jupiter's Magnetospheric Dynamics
Authors: Yoshioka K. , Tsuchiya F. , Kagitani M. , Kimura T. , Murakami G. , Fukuyama D. , Yamazaki A. , Yoshikawa I. , Fujimoto M. 
Published: October 2018

AbstractEmbedded deep inside the huge magnetosphere of Jupiter, the moon Io has active volcanos. Jovian magnetospheric dynamics are driven by the expulsion of Iogenic plasma in the strongly magnetized, fast‐rotating system and should vary in response to Io's volcanic activity. In early 2015 when various observations indicated an increase in volcanic activity, the EXCEED instrument onboard the Hisaki spacecraft continuously observed the Jovian magnetosphere via the aurora emission and the emission from the Io plasma torus. The plasma diagnosis of the enhanced Io plasma torus spectrum along with a physical chemistry model for deducing plasma parameters revealed a higher plasma density and a 2–4 times faster radial flow as compared with a volcanically quiet period. Aurora emissions reflecting midmagnetospheric activities showed multiple highly elevated brightness peaks about a month later. Long‐term and continuous monitoring by Hisaki enabled the first comprehensive observations of the Jovian magnetosphere in response to Io's enhanced volcanic activity.
Comparing the Cohesive Effects of Mud and Vegetation on Delta Evolution
Authors: Lauzon Rebecca , Murray A. Brad 
Published: October 2018

AbstractCohesive sediment exerts a significant influence on delta evolution, increasing shoreline rugosity and decreasing channel mobility. Vegetation has been assumed to play a similar role in delta evolution, but its cohesive effects have not been explicitly studied. We use the model DeltaRCM to directly explore two effects of vegetation: decreasing lateral transport of sediment and increasing flow resistance. We find that vegetation and cohesive sediment do alter delta morphology and channel dynamics in similar ways (e.g., more rugose shorelines and deeper, narrower, less mobile channels) but that vegetation may have additional implications for deltaic sediment retention and stratigraphy, by confining flow and sand in channels. Our results suggest that sediment composition is a first‐order control on delta morphology, but vegetation has a stronger influence on channel mobility time scales. To fully understand the cohesive influences acting on a delta, vegetation influence should be considered in addition to fine sediment.
Energetic Radio Emissions and Possible Terrestrial Gamma‐Ray Flashes Associated With Downward Propagating Negative Leaders
Authors: Lyu Fanchao , Cummer Steven A. 
Published: October 2018

AbstractA study of negative polarity energetic in‐cloud pulses (−EIPs) during thunderstorms reveals that −EIPs occur during two distinct stages of downward negative leader development. The first group is observed at the beginning of downward negative leaders, with estimated average source altitude of ~5.9 km between main negative and lower positive charge regions. The second and new group are observed at the very end of downward negative leaders and appear to be produced at low altitudes close to the ground, where image charges amplify the electric field between the leader tip and conducting ground. Negative EIPs appear to occur only in these two scenarios, suggesting that their production require a high background electric field. Their radio emission signatures and occurrence contexts are similar with +EIPs, which are known to be connected to terrestrial gamma‐ray flashes. We thus suggest that these two types of −EIPs may be associated with downward terrestrial gamma ray flashes.
Importance of the El Niño Teleconnection to the 21st Century California Wintertime Extreme Precipitation Increase
Authors: Zecca Katherina , Allen Robert J. , Anderson Ray G. 
Published: October 2018

AbstractUnder continued climate warming, California (CA) hydrological projections, particularly precipitation, exhibit significant uncertainty. Recent analyses, however, have indicated a tendency for increased CA precipitation through the 21st century, particularly during December‐January‐February (DJF). Here we show that this increase is due entirely to an increase in extreme (>90th percentile) daily precipitation. This response is consistent with enhanced horizontal vapor transport off the CA coast, most of which is caused by thermodynamical effects due to increases in atmospheric moisture. Furthermore, observations over the late twentieth century show that CA DJF extreme precipitation is associated with an El Niño‐like sea surface temperature anomaly pattern. Models that better simulate the observed El Niño teleconnection with CA DJF precipitation also better reproduce the El Niño‐like sea surface temperature anomaly pattern associated with extreme precipitation, including the associated thermodynamical and dynamical atmospheric responses. In turn, these models simulate a significantly larger increase in extreme precipitation under warming.
Episodic Slow Slip Events and Overlying Plate Seismicity at the Southernmost Ryukyu Trench
Authors: Chen Sean Kuanhsiang , Wu Yih‐Min , Chan Yu‐Chang 
Published: October 2018

AbstractShallow slow slip events accompanied by seismicity has been increasingly reported in subduction zones during the last decade; however, the relationship between shallow slip events and seismicity is unclear. We report episodic slow slip events and seismicity at the southernmost Ryukyu Trench. The inversion results from GPS‐derived cumulative displacements indicate that the slow slip events occur offshore in northeastern Taiwan on the shallow subduction interface, where high seismic VP/VS ratios applies. Seismicity is observed above the subduction interface for locations of significant variations in the VP/VS ratio and does not follow the migration of peak slip along the subduction interface. We calculated the temporal evolution between the seismicity and the propagation of slow slip events and determined that seismicity is not primarily driven by slip propagation. The spatiotemporal relationship, coupled with the VP/VS ratio, suggests that high‐pressure fluid activity may be crucial to episodes of slow slip events and seismicity.
Early Mars Climate History: Characterizing a “Warm and Wet” Martian Climate With a 3‐D Global Climate Model and Testing Geological Predictions
Authors: Palumbo Ashley M. , Head James W. 
Published: October 2018

AbstractObservations of Late Noachian‐Early Hesperian‐aged Martian surfaces reveal valley networks, lakes, degraded craters, and putative oceanic shorelines, often interpreted to require a persistent “warm and wet” climate, characterized by mean annual temperature >273 K and abundant rainfall. We simulate this “warm and wet” climate (global mean annual temperature ~ 275 K) with a 3‐D global climate model to determine whether these features could have formed in this climate through rainfall activity. We find that rainfall is limited in abundance and areal distribution, precipitation is dominated by snowfall, and highlands temperatures are <273 K for the majority of the year. We conclude that, in this simulated climate scenario, (1) Late Noachian‐Early Hesperian valley networks and lakes could not have formed through rainfall‐related erosion, (2) crater degradation by rainsplash and runoff is not predicted, (3) global clay formation through long‐lived rainfall, fluvial activity, and warm temperatures is unlikely, and (4) the presence of a rainfall‐ and overland flow‐fed northern ocean is improbable.
Multipoint Observations of Nightside Plasmaspheric Hiss Generated by Substorm‐Injected Electrons
Authors: Su Zhenpeng , Liu Nigang , Zheng Huinan , Wang Yuming , Wang Shui 
Published: October 2018

AbstractPlasmaspheric hiss plays a key role in shaping the radiation belt environment, whose origin remains under active debate. Using the wave and particle data of Van Allen Probes, Geostationary Operational Environmental Satellites, and Time History of Events and Macroscale Interactions during Substorm spacecraft, we here examine the nightside plasmaspheric hiss generation during a substorm. The substorm‐electron injection caused the plasmapause to shrink promptly from Lpp=6.6 to 5.1. Corresponding to the azimuthal drift of the injected electrons, the plasmaspheric hiss was intensified gradually from nightside to dayside. Particularly, in the inner postmidnight plasmasphere free from the substorm injection, the instantaneous peak amplitude of hiss reached 0.9 nT. The enhanced hiss within the locally unchanged plasma must originate from other spatial regions. Our data and modeling demonstrate that the large‐amplitude hiss was generated by the substorm‐injected electrons drifting into the outer postmidnight plasmasphere, rather than linked to the nightside chorus suffering strong Landau damping or the dayside chorus/hiss propagating azimuthally to the nightside plasmasphere.
First In Situ Seismic Record of Spreading Events at the Ultraslow Spreading Southwest Indian Ridge
Authors: Meier M. , Schlindwein V. 
Published: October 2018

AbstractIn situ observations of mid‐ocean ridge spreading events are rare, and no observations exist at ultraslow spreading ridges. In 2013, two earthquake swarms and prominent, tidally modulated harmonic tremor were accidentally recorded by ocean bottom seismometers at the Southwest Indian Ridge. After relative relocation, the first swarm shows downward migrating hypocenters, while the second swarm immediately spreads over a steeply dipping plane originating at the same location as the first swarm. The tremor signal is temporally connected to the swarms and persists for more than 20 days after the second swarm. Polarization analysis points to two source locations above the seismically active area at 2‐ to 8‐km depth. We interpret swarms and tremor as evidence for a dike intrusion event that caused disruption to an existent hydrothermal system. The tremor may be generated by enhanced hydrothermal circulation caused by the added heat of the intrusion with increased flow during low tides.
Galveston Bay and Coastal Ocean Optical‐Geochemical Response to Hurricane Harvey From VIIRS Ocean Color
Authors: D’Sa Eurico J. , Joshi Ishan , Liu Bingqing 
Published: October 2018

AbstractDissolved and particulate organic carbon, suspended particulate matter concentrations, and their optical proxies colored dissolved organic matter absorption and backscattering coefficients were studied in Galveston Bay, Texas, following the extreme flooding of Houston and surrounding areas due to Hurricane Harvey (25–29 August 2017) using field and ocean color observations. A three‐step empirical‐semianalytic algorithm for determination of colored dissolved organic matter absorption and backscattering coefficients revealed the dynamics of dissolved organic carbon and particle distribution from Visible and Infrared Imaging Radiometric Suite ocean color. Environmental drivers, especially floodwater discharge and winds, strongly influenced the spatiotemporal distribution of dissolved/particulate material in the bay and shelf waters following the hurricane passage. Over 10 days during/following the hurricane, ~25.2 × 106 kg C of total organic carbon and ~314.7 × 106 kg of suspended particulate matter were rapidly exported from Galveston Bay (representing ~0.65% and 0.27% of respective annual Mississippi River fluxes to the Gulf of Mexico), with potential for ecological impacts to shelf waters.
Annual Cycle of Turbulent Dissipation Estimated from Seagliders
Authors: Evans Dafydd Gwyn , Lucas Natasha Sarah , Hemsley Victoria , Frajka‐Williams Eleanor , Naveira Garabato Alberto C. , Martin Adrian , Painter Stuart C. , Inall Mark E. , Palmer Matthew R. 
Published: October 2018

AbstractThe rate of dissipation of turbulent kinetic energy is estimated using Seaglider observations of vertical water velocity in the midlatitude North Atlantic. This estimate is based on the large‐eddy method, allowing the use of measurements of turbulent energy at large scales O(1–10 m) to diagnose the rate of energy dissipated through viscous processes at scales O(1 mm). The Seaglider data considered here were obtained in a region of high stratification (1 × 10−4<N < 1×10−2s−1), where previous implementations of this method fail. The large‐eddy method is generalized to high‐stratification by high‐pass filtering vertical velocity with a cutoff dependent on the local buoyancy frequency, producing a year‐long time series of dissipation rate spanning the uppermost 1,000 m with subdaily resolution. This is compared to the dissipation rate estimated from a moored 600 kHz acoustic Doppler current profiler. The variability of the Seaglider‐based dissipation correlates with one‐dimensional scalings of wind‐ and buoyancy‐driven mixed‐layer turbulence.
Solar Wind‐Induced Water Cycle on the Moon
Authors: Jones Brant M. , Aleksandrov Alex , Hibbitts K. , Dyar M. D. , Orlando Thomas M. 
Published: October 2018

AbstractThe solar wind has been implicated as a source of water on airless bodies such as the Moon, asteroids, and possibly Mercury, yet a kinetic and mechanistic chemical model consistent with present‐day observational data is still lacking. Utilizing available data sets on temperature‐driven water formation and desorption from metal oxides (e.g., SiO2, TiO2, and Al2O3) with surface hydroxyl defects (─OH) and experimental data from a lunar mare regolith Apollo sample (10084), the 2.8‐μm optical signal on the Moon is modeled. Specifically, the presence and persistence of this band result from the balance of formation and loss mechanisms associated with solar wind production and thermal transformation of hydroxyls on and within the regolith. This cycle involves formation and release of molecular water via recombinative desorption of the chemically bound ─OH. Though this mechanism forms gas‐phase H2O on the sunlit side, photodissociation and dissociative adsorption lead to rehydroxylation and very limited exospheric water over a lunation.
The Neodymium Isotope Fingerprint of Adélie Coast Bottom Water
Authors: Lambelet M. , van de Flierdt T. , Butler E. C. V. , Bowie A. R. , Rintoul S. R. , Watson R. J. , Remenyi T. , Lannuzel D. , Warner M. , Robinson L. F. , Bostock H. C. , Bradtmiller L. I. 
Published: October 2018

AbstractAdélie Land Bottom Water (ALBW), a variety of Antarctic Bottom Water formed off the Adélie Land coast of East Antarctica, ventilates the abyssal layers of the Australian sector of the Southern Ocean as well as the eastern Indian and Pacific Oceans. We present the first dissolved neodymium (Nd) isotope and concentration measurements for ALBW. The summertime signature of ALBW is characterized by εNd = −8.9, distinct from Ross Sea Bottom Water, and similar to Weddell Sea Bottom Water. Adélie Land Shelf Water, the precursor water mass for wintertime ALBW, features the least radiogenic Nd fingerprint observed around Antarctica to date (εNd = −9.9). Local geology around Antarctica is important in setting the chemical signature of individual varieties of Antarctic Bottom Water, evident from the shelf water signature, which should be considered in the absence of direct wintertime observations.
Shape of Atlantic Tropical Cyclone Tracks and the Indian Monsoon
Authors: Kelly Patrick , Leung L. Ruby , Balaguru Karthik , Xu Wenwei , Mapes Brian , Soden Brian 
Published: October 2018

AbstractWe find a significant enhancement of the North Atlantic subtropical high on interannual timescales (1970–2016) concurrently linked to an anomalously strong Indian monsoon in September. Consistent with a stronger North Atlantic subtropical high, enhanced anticyclonic flow and subtropical easterlies in the eastern Atlantic basin are found during strong monsoon years. Observational regression analysis combined with a statistical track model are used to assess the influence of these monsoon‐linked wind variations on Atlantic tropical cyclone (TC) tracks originating in the main development region. When controlling for effects of El Niño–Southern Oscillation (ENSO), a westward shift of TC tracks is shown to be robustly correlated to internal monsoon variability in September. This work highlights variability of the Indian monsoon as an additional constraint on Atlantic TCs, with increased landfall probability during a strong monsoon. Previous attribution of similar steering effects to ENSO need to be reconsidered to account for ENSO's correlation with the monsoon.
Longitudinal Structure of Oxygen Torus in the Inner Magnetosphere: Simultaneous Observations by Arase and Van Allen Probe A
Authors: Nosé M. , Matsuoka A. , Kumamoto A. , Kasahara Y. , Goldstein J. , Teramoto M. , Tsuchiya F. , Matsuda S. , Shoji M. , Imajo S. , Oimatsu S. , Yamamoto K. , Obana Y. , Nomura R. , Fujimoto A. , Shinohara I. , Miyoshi Y. , Kurth W. S. , Kletzing C. A. , Smith C. W. , MacDowall R. J. 
Published: October 2018

AbstractSimultaneous observations of the magnetic field and plasma waves made by the Arase and Van Allen Probe A satellites at different magnetic local time (MLT) enable us to deduce the longitudinal structure of an oxygen torus for the first time. During 04:00–07:10 UT on 24 April 2017, Arase flew from L = 6.2 to 2.0 in the morning sector and detected an enhancement of the average plasma mass up to ~3.5 amu around L = 4.9–5.2 and MLT = 5.0 hr, implying that the plasma consists of approximately 15% O+ ions. Probe A moved outbound from L = 2.0 to 6.2 in the afternoon sector during 04:10–07:30 UT and observed no clear enhancements in the average plasma mass. For this event, the O+ density enhancement in the inner magnetosphere (i.e., oxygen torus) does not extend over all MLT but is skewed toward the dawn, being described more precisely as a crescent‐shaped torus or a pinched torus.
Transport of Pacific Water Into the Canada Basin and the Formation of the Chukchi Slope Current
Authors: Spall Michael A. , Pickart Robert S. , Li Min , Itoh Motoyo , Lin Peigen , Kikuchi Takashi , Qi Yiquan 
Published: October 2018

AbstractA high‐resolution regional ocean model together with moored hydrographic and velocity measurements is used to identify the pathways and mechanisms by which Pacific water, modified over the Chukchi shelf, crosses the shelf break into the Canada Basin. Most of the Pacific water flowing into the Arctic Ocean through Bering Strait enters the Canada Basin through Barrow Canyon. Strong advection allows the water to cross the shelf break and exit the shelf. Wind forcing plays little role in this process. Some of the outflowing water from Barrow Canyon flows to the east into the Beaufort Sea; however, approximately 0.4 to 0.5 Sv turns to the west forming the newly identified Chukchi Slope Current. This transport occurs at all times of year, channeling both summer and winter waters from the shelf to the Canada Basin. The model indicates that approximately 75% of this water was exposed to the mixed layer within the Chukchi Sea, while the remaining 25% was able to cross the shelf during the stratified summer before convection commences in late fall. We view the
Sv of the Chukchi Slope Current as replacing Beaufort Gyre water that would have come from the east in the absence of the cross‐topography flow in Barrow Canyon. The weak eastward flow on the Beaufort slope is also consistent with the local disruption of the Beaufort Gyre by the Barrow Canyon outflow.
Coastal Upwelling Revisited: Ekman, Bakun, and Improved Upwelling Indices for the U.S. West Coast
Authors: Jacox Michael G. , Edwards Christopher A. , Hazen Elliott L. , Bograd Steven J. 
Published: October 2018

AbstractCoastal upwelling is responsible for thriving marine ecosystems and fisheries that are disproportionately productive relative to their surface area, particularly in the world's major eastern boundary upwelling systems. Along oceanic eastern boundaries, equatorward wind stress and the Earth's rotation combine to drive a near‐surface layer of water offshore, a process called Ekman transport. Similarly, positive wind stress curl drives divergence in the surface Ekman layer and consequently upwelling from below, a process known as Ekman suction. In both cases, displaced water is replaced by upwelling of relatively nutrient‐rich water from below, which stimulates the growth of microscopic phytoplankton that form the base of the marine food web. Ekman theory is foundational and underlies the calculation of upwelling indices such as the “Bakun Index” that are ubiquitous in eastern boundary upwelling system studies. While generally valuable first‐order descriptions, these indices and their underlying theory provide an incomplete picture of coastal upwelling. Here we review the relevant dynamics and limitations of classical upwelling indices, particularly related to representation of the surface wind stress, the influence of geostrophic currents, and the properties of upwelled water. To address these shortcomings, we present two new upwelling indices for the U.S. West Coast (31–47°N), which are available from 1988 to present. The Coastal Upwelling Transport Index and the Biologically Effective Upwelling Transport Index provide improved estimates of vertical transport and vertical nitrate flux, respectively, by leveraging technological and scientific advances realized since the introduction of the Bakun Index nearly a half century ago.
(U‐Th)/He Thermochronology and Zircon Radiation Damage in the South American Passive Margin: Thermal Overprint of the Paraná LIP?
Authors: Hueck Mathias , Dunkl István , Heller Beatrix , Stipp Basei Miguel Angelo , Siegesmund Siegfried 
Published: October 2018

AbstractNew zircon and apatite (U‐Th)/He data (AHe and ZHe) from the crystalline basement of the South American passive margin in southern Brazil present a wide distribution of Phanerozoic apparent ages, recording its prerift evolution. Its geological significance can be investigated by modeling the influence of the accumulated radiation damages on the measured crystals in its He ages during a long upper crust residence. Despite the presence of a significant fault in the studied area, the samples essentially constrain a uniform thermal history for the entire study area. Zircon helium ages spread from 472 to 26 Ma and correlate strongly with the radioactive element content of the crystals. Although the region was probably covered by Paleozoic sediments of the Paraná Basin, the ZHe system experienced a more intense thermal overprint, most likely the onset of the Paraná Large Igneous Province (LIP), causing its dispersion. The nearby intrusion of a feeding system of the LIP, the Florianópolis Dyke Swarm, may have contributed for keeping geothermal gradients elevated for a period long enough to promote the observed reset. After the extrusion of the volcanism, the study area was probably covered by up to 2 km of basalt floods, imprinting temperatures above the AHe partial retention zone on the crystalline basement. These were eroded during rapid cooling between 75 and 55 Ma, as indicated by thermal modeling. Additional analyses with Raman spectroscopy were used for calculating radiation damage ages in the zircon crystals measured for (U‐Th)/He, resulting in a comparable set of ages.