bluuebunny/crossref_metadata_2025_split huggingface dataset:
Subsea ice‐bearing permafrost on the U.S. Beaufort Margin: 2. Borehole constraints
Authors: Ruppel Carolyn D. , Herman Bruce M. , Brothers Laura L. , Hart Patrick E. 
Published: October 2016

AbstractBorehole logging data from legacy wells directly constrain the contemporary distribution of subsea permafrost in the sedimentary section at discrete locations on the U.S. Beaufort Margin and complement recent regional analyses of exploration seismic data to delineate the permafrost's offshore extent. Most usable borehole data were acquired on a ∼500 km stretch of the margin and within 30 km of the contemporary coastline from north of Lake Teshekpuk to nearly the U.S.‐Canada border. Relying primarily on deep resistivity logs that should be largely unaffected by drilling fluids and hole conditions, the analysis reveals the persistence of several hundred vertical meters of ice‐bonded permafrost in nearshore wells near Prudhoe Bay and Foggy Island Bay, with less permafrost detected to the east and west. Permafrost is inferred beneath many barrier islands and in some nearshore and lagoonal (back‐barrier) wells. The analysis of borehole logs confirms the offshore pattern of ice‐bearing subsea permafrost distribution determined based on regional seismic analyses and reveals that ice content generally diminishes with distance from the coastline. Lacking better well distribution, it is not possible to determine the absolute seaward extent of ice‐bearing permafrost, nor the distribution of permafrost beneath the present‐day continental shelf at the end of the Pleistocene. However, the recovery of gas hydrate from an outer shelf well (Belcher) and previous delineation of a log signature possibly indicating gas hydrate in an inner shelf well (Hammerhead 2) imply that permafrost may once have extended across much of the shelf offshore Camden Bay.
Winter warming and summer monsoon reduction after volcanic eruptions in Coupled Model Intercomparison Project 5 (CMIP5) simulations
Authors: Zambri Brian , Robock Alan 
Published: October 2016

AbstractThough previous studies have shown that state‐of‐the‐art climate models are rather imperfect in their simulations of the climate response to large volcanic eruptions, the results depend on how the analyses were done. Observations show that all recent large tropical eruptions were followed by winter warming in the first Northern Hemisphere (NH) winter after the eruption, with little such response in the second winter, yet a number of the evaluations have combined the first and second winters. We have looked at just the first winter after large eruptions since 1850 in the Coupled Model Intercomparison Project 5 historical simulations and find that most models do produce a winter warming signal, with warmer temperatures over NH continents and a stronger polar vortex in the lower stratosphere. We also examined NH summer precipitation responses in the first year after these large volcanic eruptions and find clear reductions of summer monsoon rainfall.
The global infrared energy budget of the thermosphere from 1947 to 2016 and implications for solar variability
Authors: Mlynczak Martin G. , Hunt Linda A. , Russell James M. , Marshall B. Thomas , Mertens Christopher J. , Thompson R. Earl 
Published: October 2016

AbstractWe present an empirical model of the global infrared energy budget of the thermosphere over the past 70 years. The F10.7, Ap, and Dst indices are used in linear regression fits to the 14.5 year time series of radiative cooling by carbon dioxide and nitric oxide measured by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on the TIMED satellite. Databases of these indices are used to develop the radiative cooling time series from 1947. No consistent relation between the occurrence of peak sunspot number and peak infrared cooling is found over the past six solar cycles. The total infrared energy radiated by the thermosphere, integrated over a solar cycle, is nearly constant over five complete solar cycles studied. This is a direct consequence of the geoeffective solar energy also being nearly constant over the same intervals. These results provide a new metric for assessing the terrestrial context of the long‐term record of solar‐related indices.
Macroscopic quasi‐linear theory of electromagnetic electron cyclotron instability associated with core and halo solar wind electrons
Authors: Sarfraz M. , Saeed Sundas , Yoon P. H. , Abbas G. , Shah H. A. 
Published: October 2016

AbstractSpacecraft observations made near 1 AU show that both core and halo solar wind electrons exhibit temperature anisotropies that appear to be regulated by marginal electromagnetic electron cyclotron instability condition. In the literature, the threshold conditions of this instability, operative for T⊥>T∥, have been expressed as an inverse correlation between the temperature anisotropy, T⊥/T∥, and parallel beta, β∥, but such a relation was deduced on the basis of linear stability analysis combined with empirical fitting. The present paper, on the other hand, employs macroscopic quasi‐linear analysis for core‐halo two‐component model of the solar wind electrons, in order to follow the self‐consistent time history of the core and halo temperature development as well as the dynamics of magnetic field perturbation wave energy. In the present analysis, the inverse correlation for core and halo temperature anisotropy and parallel beta naturally emerges from the solutions of self‐consistent theory. The present findings indicate that the macroscopic quasi‐linear method may be useful for modeling the dynamics of solar wind electrons.
Signatures of complex magnetic topologies from multiple reconnection sites induced by Kelvin‐Helmholtz instability
Authors: Vernisse Y. , Lavraud B. , Eriksson S. , Gershman D. J. , Dorelli J. , Pollock C. , Giles B. , Aunai N. , Avanov L. , Burch J. , Chandler M. , Coffey V. , Dargent J. , Ergun R. E. , Farrugia C. J. , Génot V. , Graham D. B. , Hasegawa H. , Jacquey C. , Kacem I. , Khotyaintsev Y. , Li W. , Magnes W. , Marchaudon A. , Moore T. , Paterson W. , Penou E. , Phan T. D. , Retino A. , Russell C. T. , Saito Y. , Sauvaud J.‐A. , Torbert R. , Wilder F. D. , Yokota S. 
Published: October 2016

AbstractThe Magnetospheric Multiscale mission has demonstrated the frequent presence of reconnection exhausts at thin current sheets within Kelvin‐Helmholtz (KH) waves at the flank magnetopause. Motivated by these recent observations, we performed a statistical analysis of the boundary layers on the magnetosheath side of all KH current sheets on 8 September 2015. We show 86% consistency between the exhaust flows and particle leakage in the magnetosheath boundary layers but further highlight the very frequent presence of additional boundary layer signatures that do not come from the locally observed reconnection exhausts. These additional electron and ion boundary layers, of various durations and at various positions with respect to the leading and trailing boundaries of the KH waves, signal connections to reconnection sites at other locations. Based on the directionality and extent of these layers, we provide an interpretation whereby complex magnetic topologies can arise within KH waves from the combination of reconnection in the equatorial plane and at midlatitudes in the Southern and Northern Hemispheres, where additional reconnection sites are expected to be triggered by the three‐dimensional field lines interweaving induced by the KH waves at the flanks (owing to differential flow and magnetic field shear with latitude). The present event demonstrates that the three‐dimensional development of KH waves can induce plasma entry (through reconnection at both midlatitude and equatorial regions) already sunward of the terminator where the instability remains in its linear stage.
Detection of multiple terrestrial gamma‐ray flashes from thunderstorm systems
Authors: Ursi A. , Marisaldi M. , Tavani M. , Casella D. , Sanò P. , Dietrich S. 
Published: October 2016

AbstractSince their discovery, Terrestrial Gamma ray Flashes (TGFs) exhibited an evident correlation with thunderstorms and lightning activity. The fleeting nature of these events and the heavy absorption of gamma rays in the lowest atmospheric layers severely hamper the observation of this phenomenon, making us reveal just a small fraction of a probably much wider population. As each thunderstorm produces a large amount of lightning discharges during its lifetime, it is reasonable that even a large amount of TGFs are produced during the same event. However, detection of multiple TGFs coming from the same storm is difficult to perform, as it requires the constant monitoring of a spatially limited geographic region: this is not an easy task to perform for satellites on high‐inclination orbits that make them experience nonnegligible latitudinal shifts at each orbital passage over a certain region, preventing the monitoring of a limited geographic region throughout successive overpasses. In this perspective, the quasi‐equatorial (2.5°) orbit of the Astrorivelatore Gamma ad Immagini LEggero (AGILE) satellite ensures a minimal latitudinal shift when flying over the same region at successive passages, allowing for the follow‐up of thunderstorms in time. We exploit this feature of the AGILE satellite to search for multiple TGFs coming from the same geographic region and, in particular, from the same thunderstorm. We carry out this search on the AGILE TGF database (2009–2016), ending up with a sample of 79 systems producing more than one TGF, both during the same overpass and up to four overpasses after. Data acquired by geostationary meteorological satellites and cross correlation with radio sferics detected by World Wide Lightning Location Network are used to support this investigation. The AGILE satellite for the first time clearly establishes the multiple occurrences of TGFs from convective thunderstorms, both on timescales of minutes to several hours.
A database of interplanetary and interstellar dust detected by the Wind spacecraft
Authors: Malaspina David M. , Wilson Lynn B. 
Published: October 2016

AbstractIt was recently discovered that the WAVES instrument on the Wind spacecraft has been detecting, in situ, interplanetary and interstellar dust of approximately 1 μm radius for the past 22 years. These data have the potential to enable advances in the study of cosmic dust and dust‐plasma coupling within the heliosphere due to several unique properties: the Wind dust database spans two full solar cycles; it contains over 107,000 dust detections; it contains information about dust grain direction of motion; it contains data exclusively from the space environment within 350 Earth radii of Earth; and it overlaps by 12 years with the Ulysses dust database. Further, changes to the WAVES antenna response and the plasma environment traversed by Wind over the lifetime of the Wind mission create an opportunity for these data to inform investigations of the physics governing the coupling of dust impacts on spacecraft surfaces to electric field antennas. A Wind dust database has been created to make the Wind dust data easily accessible to the heliophysics community and other researchers. This work describes the motivation, methodology, contents, and accessibility of the Wind dust database.
Geomagnetically induced currents around the world during the 17 March 2015 storm
Authors: Carter B. A. , Yizengaw E. , Pradipta R. , Weygand J. M. , Piersanti M. , Pulkkinen A. , Moldwin M. B. , Norman R. , Zhang K. 
Published: October 2016

AbstractGeomagnetically induced currents (GICs) represent a significant space weather issue for power grid and pipeline infrastructure, particularly during severe geomagnetic storms. In this study, magnetometer data collected from around the world are analyzed to investigate the GICs caused by the 2015 St. Patrick's Day storm. While significant GIC activity in the high‐latitude regions due to storm time substorm activity is shown for this event, enhanced GIC activity was also measured at two equatorial stations in the American and Southeast Asian sectors. This equatorial GIC activity is closely examined, and it is shown that it is present both during the arrival of the interplanetary shock at the storm sudden commencement (SSC) in Southeast Asia and during the main phase of the storm ∼10 h later in South America. The SSC caused magnetic field variations at the equator in Southeast Asia that were twice the magnitude of those observed only a few degrees to the north, strongly indicating that the equatorial electrojet (EEJ) played a significant role. The large equatorial magnetic field variations measured in South America are also examined, and the coincident solar wind data are used to investigate the causes of the sudden changes in the EEJ ∼10 h into the storm. From this analysis it is concluded that sudden magnetopause current increases due to increases in the solar wind dynamic pressure, and the sudden changes in the resultant magnetospheric and ionospheric current systems, are the primary drivers of equatorial GICs.
Interseismic deformation and moment deficit along the Manila subduction zone and the Philippine Fault system
Authors: Hsu Ya‐Ju , Yu Shui‐Beih , Loveless John P. , Bacolcol Teresito , Solidum Renato , Luis Artemio , Pelicano Alfie , Woessner Jochen 
Published: October 2016

AbstractWe examine interseismic coupling of the Manila subduction zone and fault activity in the Luzon area using a block model constrained by GPS data collected from 1998 to 2015. Estimated long‐term slip rates along the Manila subduction zone show a gradual southward decrease from 90–100 mm/yr at the northwest tip of Luzon to 65–80 mm/yr at the southern portion of the Manila Trench. We provide two block models (models A and B) to illustrate possible realizations of coupling along the Manila Trench, which may be used to infer future earthquake rupture scenarios. Model A shows a low coupling ratio of 0.34 offshore western Luzon and continuous creeping on the plate interface at latitudes 18–19°N. Model B includes the North Luzon Trough Fault and shows prevalent coupling on the plate interface with a coupling ratio of 0.48. Both models fit GPS velocities well, although they have significantly different tectonic implications. The accumulated strain along the Manila subduction zone at latitudes 15–19°N could be balanced by earthquakes with composite magnitudes of Mw 8.8–9.2, assuming recurrence intervals of 500–1000 years. GPS observations are consistent with full locking of the majority of active faults in Luzon to a depth of 20 km. Inferred moments of large inland earthquakes in Luzon fall in the range of Mw 6.9–7.6 assuming a recurrence interval of 100 years.
Continental rupture and the creation of new crust in the Salton Trough rift, Southern California and northern Mexico: Results from the Salton Seismic Imaging Project
Authors: Han Liang , Hole John A. , Stock Joann M. , Fuis Gary S. , Kell Annie , Driscoll Neal W. , Kent Graham M. , Harding Alistair J. , Rymer Michael J. , González‐Fernández Antonio , Lázaro‐Mancilla Octavio 
Published: October 2016

AbstractA refraction and wide‐angle reflection seismic profile along the axis of the Salton Trough, California and Mexico, was analyzed to constrain crustal and upper mantle seismic velocity structure during active continental rifting. From the northern Salton Sea to the southern Imperial Valley, the crust is 17–18 km thick and approximately one‐dimensional. The transition at depth from Colorado River sediment to underlying crystalline rock is gradual and is not a depositional surface. The crystalline rock from ~3 to ~8 km depth is interpreted as sediment metamorphosed by high heat flow. Deeper felsic crystalline rock could be stretched preexisting crust or higher‐grade metamorphosed sediment. The lower crust below ~12 km depth is interpreted to be gabbro emplaced by rift‐related magmatic intrusion by underplating. Low upper mantle velocity indicates high temperature and partial melting. Under the Coachella Valley, sediment thins to the north and the underlying crystalline rock is interpreted as granitic basement. Mafic rock does not exist at 12–18 km depth as it does to the south, and a weak reflection suggests Moho at ~28 km depth. Structure in adjacent Mexico has slower midcrustal velocity, and rocks with mantle velocity must be much deeper than in the Imperial Valley. Slower velocity and thicker crust in the Coachella and Mexicali valleys define the rift zone between them to be >100 km wide in the direction of plate motion. North American lithosphere in the central Salton Trough has been rifted apart and is being replaced by new crust created by magmatism, sedimentation, and metamorphism.
GPS Imaging of vertical land motion in California and Nevada: Implications for Sierra Nevada uplift
Authors: Hammond William C. , Blewitt Geoffrey , Kreemer Corné 
Published: October 2016

AbstractWe introduce Global Positioning System (GPS) Imaging, a new technique for robust estimation of the vertical velocity field of the Earth's surface, and apply it to the Sierra Nevada Mountain range in the western United States. Starting with vertical position time series from Global Positioning System (GPS) stations, we first estimate vertical velocities using the MIDAS robust trend estimator, which is insensitive to undocumented steps, outliers, seasonality, and heteroscedasticity. Using the Delaunay triangulation of station locations, we then apply a weighted median spatial filter to remove velocity outliers and enhance signals common to multiple stations. Finally, we interpolate the data using weighted median estimation on a grid. The resulting velocity field is temporally and spatially robust and edges in the field remain sharp. Results from data spanning 5–20 years show that the Sierra Nevada is the most rapid and extensive uplift feature in the western United States, rising up to 2 mm/yr along most of the range. The uplift is juxtaposed against domains of subsidence attributable to groundwater withdrawal in California's Central Valley. The uplift boundary is consistently stationary, although uplift is faster over the 2011–2016 period of drought. Uplift patterns are consistent with groundwater extraction and concomitant elastic bedrock uplift, plus slower background tectonic uplift. A discontinuity in the velocity field across the southeastern edge of the Sierra Nevada reveals a contrast in lithospheric strength, suggesting a relationship between late Cenozoic uplift of the southern Sierra Nevada and evolution of the southern Walker Lane.
Close correlation between global air temperature change and polar motion during 1962–2013
Authors: Huang Mei , Zhu Lin , Gong He , Shao Yaping 
Published: October 2016

AbstractPolar motion is an important Earth orientation parameter, but our understanding of its relation to global climate change is highly uncertain. In this study, we examine the links between polar motion excitation and annual mean air temperature during the period of 1962–2013 and discuss the possible responsible mechanisms. The regions of positive correlation correspond well with the warming centers. Spectral analysis shows that they have strong signals at similar frequencies. Strong correlations are also found between the polar motion and surface air pressure and vertical integrated zonal wind. This implies that polar motion serves as an important indicator of global climate change, and thus, the feedbacks between the solid Earth and the climate system deserve careful considerations.
Increase in winter haze over eastern China in recent decades: Roles of variations in meteorological parameters and anthropogenic emissions
Authors: Yang Yang , Liao Hong , Lou Sijia 
Published: October 2016

AbstractThe increase in winter haze over eastern China in recent decades due to variations in meteorological parameters and anthropogenic emissions was quantified using observed atmospheric visibility from the National Climatic Data Center Global Summary of Day database for 1980–2014 and simulated PM2.5 concentrations for 1985–2005 from the Goddard Earth‐Observing System (GEOS) chemical transport model (GEOS‐Chem). Observed winter haze days averaged over eastern China (105–122.5°E, 20–45°N) increased from 21 days in 1980 to 42 days in 2014 and from 22 to 30 days between 1985 and 2005. The GEOS‐Chem model captured the increasing trend of winter PM2.5 concentrations for 1985–2005, with concentrations averaged over eastern China increasing from 16.1 µg m−3 in 1985 to 38.4 µg m−3 in 2005. Considering variations in both anthropogenic emissions and meteorological parameters, the model simulated an increase in winter surface‐layer PM2.5 concentrations of 10.5 (±6.2) µg m−3 decade−1 over eastern China. The increasing trend was only 1.8 (±1.5) µg m−3 decade−1 when variations in meteorological parameters alone were considered. Among the meteorological parameters, the weakening of winds by −0.09 m s−1 decade−1 over 1985–2005 was found to be the dominant factor leading to the decadal increase in winter aerosol concentrations and haze days over eastern China during recent decades.
Experimental modeling of pressurized subglacial water flow: Implications for tunnel valley formation
Authors: Lelandais Thomas , Mourgues Régis , Ravier Édouard , Pochat Stéphane , Strzerzynski Pierre , Bourgeois Olivier 
Published: October 2016

AbstractTunnel valleys are elongated hollows commonly found in formerly glaciated areas and interpreted as resulting from subglacial meltwater erosion beneath ice sheets. Over the past two decades, the number of studies of terrestrial tunnel valleys has continuously increased, and their existence has been hypothesized also on Mars, but their formation mechanisms remain poorly understood. We introduce here an innovative experimental approach to examine erosion by circulation of pressurized meltwater within the substratum and at the ice/substratum interface. We used a permeable substratum (sand) partially covered by a viscous, impermeable, and transparent cap (silicon putty), below which we applied a central injection of pure water. Low water pressures led to groundwater circulation in the substratum only, while water pressures exceeding a threshold that is larger than the sum of the glaciostatic and lithostatic pressures led to additional water circulation and formation of drainage landforms at the cap/substratum interface. The formation of these drainage landforms was monitored through time, and their shapes were analyzed from digital elevation models obtained by stereo‐photogrammetry. The experimental landforms include valleys that are similar to natural tunnel valleys in their spatial organization and in a number of diagnostic morphological criteria, such as undulating longitudinal profiles and “tunnel” shapes. These results are consistent with the hypothesis that overpressurized subglacial water circulation controls the formation of tunnel valleys.