bluuebunny/crossref_metadata_2025_split huggingface dataset:
Activation of hole charge carriers and generation of electromotive force in gabbro blocks subjected to nonuniform loading
Authors: Takeuchi Akihiro , Nagao Toshiyasu 
Published: April 2013

AbstractThis study verifies the activation of hole charge carriers in gabbro under nonuniform loading, which has been proposed as the possible source of the stress‐induced electromotive force in dry rocks without piezoelectric effect. When one end of vacuum‐dried gabbro blocks was subjected to uniaxial loading, the unloaded end became electronically positive (+80 mV at 50 MPa). The Seebeck coefficient of the loaded volume decreased from ~15.8 mV/K to ~14.9 mV/K when loaded, while the Seebeck coefficient of the unloaded end did not change remarkably (~15.6 mV/K). This means that this gabbro originally included a small number of hole charge carriers and the carriers in the loaded volume increased when loaded. From the viewpoint of the fundamental band model of solid state, the most reasonable mechanism of the increment is the decrease of the energy gap between the acceptors and the valence band top. Based on this idea, a generation model of the stress‐induced electromotive force is proposed. Since this model is expected to be universally applicable to various types of rocks, similar electromotive forces in the crustal scale may be induced by seismic, volcanic, and tidal activities.
Radiography of a normal fault system by 64,000 high‐precision earthquake locations: The 2009 L'Aquila (central Italy) case study
Authors: Valoroso L. , Chiaraluce L. , Piccinini D. , Di Stefano R. , Schaff D. , Waldhauser F. 
Published: April 2013

AbstractWe studied the anatomy of the fault system where the 2009 L'Aquila earthquake (MW 6.1) nucleated by means of ~64 k high‐precision earthquake locations spanning 1 year. Data were analyzed by combining an automatic picking procedure for P and S waves, together with cross‐correlation and double‐difference location methods reaching a completeness magnitude for the catalogue equal to 0.7 including 425 clusters of similar earthquakes. The fault system is composed by two major faults: the high‐angle L'Aquila fault and the listric Campotosto fault, both located in the first 10 km of the upper crust. We detect an extraordinary degree of detail in the anatomy of the single fault segments resembling the degree of complexity observed by field geologists on fault outcrops. We observe multiple antithetic and synthetic fault segments tens of meters long in both the hanging wall and footwall along with bends and cross fault intersections along the main fault and fault splays. The width of the L'Aquila fault zone varies along strike from 0.3 km where the fault exhibits the simplest geometry and experienced peaks in the slip distribution, up to 1.5 km at the fault tips with an increase in the geometrical complexity. These characteristics, similar to damage zone properties of natural faults, underline the key role of aftershocks in fault growth and co‐seismic rupture propagation processes. Additionally, we interpret the persistent nucleation of similar events at the seismicity cutoff depth as the presence of a rheological (i.e., creeping) discontinuity explaining how normal faults detach at depth.
Structural controls on localized intraplate deformation and seismicity in Southern Australia: Insights from local earthquake tomography of the Flinders Ranges
Authors: Pilia S. , Rawlinson N. , Direen N. G. , Cummins P. R. , Balfour N. 
Published: April 2013

AbstractData from an array of 24 seismometers are used to image the crust beneath the Flinders Ranges, southeast Australia, with the goal of improving our understanding of crustal structure, rheology, and the mechanism responsible for the localized intraplate deformation that characterizes this region. A subset of P‐ and S‐wave traveltimes is inverted to jointly recover earthquake hypocenters, P‐wave velocity structure and vp/vs anomalies. The P‐wave velocity model reveals a spatial correlation between major negative velocity perturbations and concentrations of seismicity. In particular, a cluster of seismicity is observed within a distinct low velocity region between the Archean‐Mesoproterozoic Gawler Craton and the Palaeo‐Mesoproterozoic Curnamona Province, from 7 to 20 km depth. We postulate that this may be associated with a pre‐existing structural weakness in the crust that arises primarily from rifting between the Curnamona Province and the Gawler Craton. Another area characterized by a high level of seismicity overlies a major sequence of N‐S trending Ross‐Delamerian thrust faults, which correspond to a band of low vp and particularly vp/vs. The lack of evidence for elevated heat flows in both of these seismogenic regions suggests that thermally induced weakness is unlikely to play a dominant role. Instead, the dynamic behavior of this intraplate region appears to be caused by a serendipitously oriented regional stress field, provided by far field forces that originate from the boundary between the Pacific and Australian plates, which acts upon preexisting structural weaknesses in the lithosphere.
A new driving mechanism for backarc extension and backarc shortening through slab sinking induced toroidal and poloidal mantle flow: Results from dynamic subduction models with an overriding plate
Authors: Schellart W. P. , Moresi L. 
Published: April 2013

AbstractWe present numerical subduction models to investigate overriding plate deformation at subduction zones. All models show forearc shortening, resulting predominantly from shear stresses at the subduction zone interface and opposite‐sense mantle shear stresses at the base of the forearc lithosphere. Models dominated by backarc extension show that it results from trench‐normal positive velocity gradients in the mantle below the overriding plate. Such gradients result from toroidal mantle flow induced by slab rollback, with velocities below the leading part of the backarc faster than the overriding plate velocity. The velocity gradients induce basal shear stresses that increase trenchward and cause trenchward overriding plate motion at a velocity (vOP⊥) whose spatial average is below the trench retreat velocity (vT⊥). The combination of basal shear stresses and average vOP⊥ < vT⊥ causes trench‐normal deviatoric tension in the backarc and backarc extension. Models dominated by backarc shortening show that it results from a relatively immobile subduction hinge and trenchward overriding plate motion driven by poloidal mantle flow. The poloidal mantle flow is induced by downdip slab sinking and causes the average vOP⊥ > vT⊥. This results in trench‐normal deviatoric compression and shortening in the leading part of the overriding plate as it collides with the subduction hinge. Ultimately, the geodynamic models demonstrate that backarc extension is favored for narrow slabs and near lateral slab edges and is driven by rollback induced toroidal mantle flow, while backarc shortening is favored for the center of wide slabs and is driven by poloidal mantle flow resulting from downdip slab motion.
Direct observations of the Antarctic circumpolar current transport on the northern flank of the Kerguelen Plateau
Authors: Damerell G. M. , Heywood K. J. , Stevens D. P. 
Published: April 2013

AbstractThe standing meander in the Antarctic Circumpolar Current (ACC) found on the northern flank of the Kerguelen Plateau was investigated during the Southern Ocean Finestructure cruise in November–December 2008. An 18 year time series of surface geostrophic currents from satellite altimetry shows that the meander as observed during this survey is typical of the region. Hydrographic stations were occupied between 65–75°E and 43–48°S on the shelf (~200 m depth) and slope into the deep ocean to the north of Kerguelen (~4700 m), providing the most detailed survey of this region to date. Geostrophic shears are referenced to lowered acoustic Doppler current profiler velocities to give the first estimate of the total volume transport in this region, and the transport budget is closed around the survey box. The Subtropical Front, Subantarctic Front, and a northern branch of the Polar Front together have an associated transport of 174 ± 22 Sv eastward. While 174 Sv is large compared with typical Drake Passage transports, it is reconciled with other estimates of the total transport with the additional 15 Sv of the Indonesian Throughflow. Baroclinic transport referenced to the deepest common level between station pairs is 119 Sv, consistent with other estimates of the baroclinic transport in this area. At this longitude, the fronts of the ACC are exceptionally close together. We discuss the exchange of properties across the fronts.
Revisit the interannual variability of the North Equatorial Current transport with ECMWF ORA‐S3
Authors: Zhai Fangguo , Hu Dunxin 
Published: April 2013

AbstractThe interannual variability of the North Equatorial Current (NEC) transport in the tropical northwestern Pacific Ocean is investigated with the output from ECMWF Ocean Analysis/Reanalysis System 3 (ORA‐S3). The results show that the amplitude and root mean square (RMS) of interannual NEC transport anomalies increase from about 3.0–4.0 Sv and 2.0 Sv at 170°E to above 5.0 and 3.4 Sv at 135°E, respectively. The NEC transport variation agrees well with the variation of the sea surface height (SSH) anomaly difference between the southern and northern boundaries of the NEC region. Further analysis near the Philippine coast suggests that their good agreement mainly comes from the agreement of the NEC transport and SSH variations south of the gyre boundary. Around the bifurcation point off the Philippine coast, the southern branch of the NEC transport is highly related to El Niño–Southern Oscillation (ENSO) events. During El Niño/La Niña years, westerly/easterly wind anomalies and positive/negative wind stress curl anomalies develop in the tropical northwestern Pacific Ocean south of 20°N before the mature phase. The wind forcing center moves eastward with time and reaches the easternmost position around 170°E several months before the mature phase. This wind forcing generates upwelling/downwelling Rossby waves, which propagate westward to result in negative/positive SSH anomalies, hence inducing a cyclonic/anticyclonic gyre anomaly, which is responsible for the increase/decrease of the NEC transport. The northern branch of the NEC transport near the Philippine coast has no significant simultaneous relation with ENSO events.
Physical controls on hypoxia in Chesapeake Bay: A numerical modeling study
Authors: Scully Malcolm E. 
Published: April 2013

ABSTRACTA three‐dimensional circulation model with a relatively simple dissolved oxygen model is used to examine the role that physical forcing has on controlling hypoxia and anoxia in Chesapeake Bay. The model assumes that the biological utilization of dissolved oxygen is constant in both time and space, isolating the role that physical forces play in modulating oxygen dynamics. Despite the simplicity of the model, it demonstrates skill in reproducing the observed variability of dissolved oxygen in the bay, highlighting the important role that variations in physical forcing have on the seasonal cycle of hypoxia. Model runs demonstrate significant changes in the annual integrated hypoxic volume as a function of river discharge, water temperature, and wind speed and direction. Variations in wind speed and direction had the greatest impact on the observed seasonal cycle of hypoxia and large impacts on the annually integrated hypoxic volume. The seasonal cycle of hypoxia was relatively insensitive to synoptic variability in river discharge, but integrated hypoxic volumes were sensitive to the overall magnitude of river discharge at annual time scales. Increases in river discharge were shown to increase hypoxic volumes, independent from the associated biological response to higher nutrient delivery. However, increases in hypoxic volume were limited at very high river discharge because increased advective fluxes limited the overall length of the hypoxic region. Changes in water temperature and its control on dissolved oxygen saturation were important to both the seasonal cycle of hypoxia and the overall magnitude of hypoxia in a given year.
Modeling how surface nitrogen fixation influences subsurface nutrient patterns in the North Atlantic
Authors: Yoshikawa Chisato , Coles Victoria J. , Hood Raleigh R. , Capone Douglas G. , Yoshida Naohiro 
Published: April 2013

AbstractWe represented mechanistically the process of nitrogen (N) fixation and associated N* anomalies in the Atlantic Ocean using a three‐dimensional coupled physical/biogeochemical model. Available direct measurements of N fixation rates in the Atlantic Ocean are compiled, and these, along with observed N* anomalies, constrain the model. The model N fixation rate for the whole Atlantic domain is 2.1 × 1012 molN yr–1. The model‐generated N* anomaly shows the observed feature of a subsurface maximum. When plotted on isopycnal surfaces, the model‐generated N* anomaly bears little relation to the pattern of N fixation at the surface. However, the highest N fixation rates should be spatially related to N* distribution if particulate export is remineralized at depths in the same region where the N fixation occurred. We performed case studies varying remineralization and advection to clarify the genesis of the N* anomaly and to determine the reasons underlying differences between N* anomalies and N fixation rate patterns. These studies indicated that the difference between these two patterns was created by both horizontal advection of excess N compared to phosphorus (P) and preferential remineralization of P compared to N. N fixation and preferential P remineralization create high N* anomalies both at the surface and in subsurface waters in the tropical Atlantic, which are transported into the northwestern North Atlantic by western boundary currents and subsequently subducted. As a result, the highest N* anomalies are located not in the tropics but in the northwestern North Atlantic.
Global carbon budgets simulated by the Beijing Climate Center Climate System Model for the last century
Authors: Wu Tongwen , Li Weiping , Ji Jinjun , Xin Xiaoge , Li Laurent , Wang Zaizhi , Zhang Yanwu , Li Jianglong , Zhang Fang , Wei Min , Shi Xueli , Wu Fanghua , Zhang Li , Chu Min , Jie Weihua , Liu Yiming , Wang Fang , Liu Xiangwen , Li Qiaoping , Dong Min , Liang Xiaoyun , Gao Yang , Zhang Jie 
Published: April 2013

AbstractThe paper examines terrestrial and oceanic carbon budgets from preindustrial time to present day in the version of Beijing Climate Center Climate System Model (BCC_CSM1.1) which is a global fully coupled climate‐carbon cycle model. Atmospheric CO2 concentration is calculated from a prognostic equation taking into account global anthropogenic CO2 emissions and the interactive CO2 exchanges of land‐atmosphere and ocean‐atmosphere. When forced by prescribed historical emissions of CO2 from combustion of fossil fuels and land use change, BCC_CSM1.1 can reproduce the trends of observed atmospheric CO2 concentration and global surface air temperature from 1850 to 2005. Simulated interannual variability and long‐term trend of global carbon sources and sinks and their spatial patterns generally agree with other model estimates and observations, which shows the following: (1) Both land and ocean in the last century act as net carbon sinks. The ability of carbon uptake by land and ocean is enhanced at the end of last century. (2) Interannual variability of the global atmospheric CO2 concentration is closely correlated with the El Niño‐Southern Oscillation cycle, in agreement with observations. (3) Interannual variation of the land‐to‐atmosphere net carbon flux is positively correlated with surface air temperature while negatively correlated with soil moisture over low and midlatitudes. The relative contribution of soil moisture to the interannual variation of land‐atmosphere CO2 exchange is more important than that of air temperature over tropical regions, while surface air temperature is more important than soil moisture over other regions of the globe.
The 2010 California Research at the Nexus of Air Quality and Climate Change (CalNex) field study
Authors: Ryerson T. B. , Andrews A. E. , Angevine W. M. , Bates T. S. , Brock C. A. , Cairns B. , Cohen R. C. , Cooper O. R. , de Gouw J. A. , Fehsenfeld F. C. , Ferrare R. A. , Fischer M. L. , Flagan R. C. , Goldstein A. H. , Hair J. W. , Hardesty R. M. , Hostetler C. A. , Jimenez J. L. , Langford A. O. , McCauley E. , McKeen S. A. , Molina L. T. , Nenes A. , Oltmans S. J. , Parrish D. D. , Pederson J. R. , Pierce R. B. , Prather K. , Quinn P. K. , Seinfeld J. H. , Senff C. J. , Sorooshian A. , Stutz J. , Surratt J. D. , Trainer M. , Volkamer R. , Williams E. J. , Wofsy S. C. 
Published: April 2013

AbstractThe California Research at the Nexus of Air Quality and Climate Change (CalNex) field study was conducted throughout California in May, June, and July of 2010. The study was organized to address issues simultaneously relevant to atmospheric pollution and climate change, including (1) emission inventory assessment, (2) atmospheric transport and dispersion, (3) atmospheric chemical processing, and (4) cloud‐aerosol interactions and aerosol radiative effects. Measurements from networks of ground sites, a research ship, tall towers, balloon‐borne ozonesondes, multiple aircraft, and satellites provided in situ and remotely sensed data on trace pollutant and greenhouse gas concentrations, aerosol chemical composition and microphysical properties, cloud microphysics, and meteorological parameters. This overview report provides operational information for the variety of sites, platforms, and measurements, their joint deployment strategy, and summarizes findings that have resulted from the collaborative analyses of the CalNex field study. Climate‐relevant findings from CalNex include that leakage from natural gas infrastructure may account for the excess of observed methane over emission estimates in Los Angeles. Air‐quality relevant findings include the following: mobile fleet VOC significantly declines, and NOx emissions continue to have an impact on ozone in the Los Angeles basin; the relative contributions of diesel and gasoline emission to secondary organic aerosol are not fully understood; and nighttime NO3 chemistry contributes significantly to secondary organic aerosol mass in the San Joaquin Valley. Findings simultaneously relevant to climate and air quality include the following: marine vessel emissions changes due to fuel sulfur and speed controls result in a net warming effect but have substantial positive impacts on local air quality.
Mercury speciation in a coal‐fired power plant plume: An aircraft‐based study of emissions from the 3640 MW Nanticoke Generating Station, Ontario, Canada
Authors: Deeds Daniel A. , Banic Catharine M. , Lu Julia , Daggupaty Sreerama 
Published: April 2013

AbstractCoal‐fired power plants are one of the principal sources of mercury to the atmosphere. The form this mercury takes is the predominant factor determining its fate after emission. Recent ground‐level field and modeling studies suggest that oxidized mercury in stack emissions is converted into elemental mercury in the plume. We present here aircraft‐based plume mercury measurements taken by Environment Canada in 2000 at the Nanticoke Generating Station as part of the Health Canada Toxic Substances Research Initiative Metals in the Environment Research Network. Although the average mercury speciation observed in the Nanticoke plume (82% Hg0, 13% Hg(II)(g), 5% Hg(P), by mass) appears to be distinct from the average mercury speciation in the Nanticoke stacks (53% Hg0, 43% Hg(II)(g), 4% Hg(P)), we find that the in‐plume elemental mercury concentrations as a whole can be explained by plume dilution after emission. The discrepancy between in‐stack and in‐plume Hg(II) concentrations is statistically significant, yet is not associated with a transformation of Hg(II) to Hg0. Sampling biases associated with the differing techniques used to measure Hg(II) in‐stack and in‐plume may reconcile the concentration discrepancy without invoking novel chemical reactions or physical processes. Although the mercury speciation of the Nanticoke plume influences local mercury deposition, the majority of the mercury emitted is transported out of the surrounding area.
Linear interference and the Northern Annular Mode response to tropical SST forcing: Sensitivity to model configuration
Authors: Fletcher Christopher G. , Kushner Paul J. 
Published: April 2013

AbstractInterannual variability in tropical sea surface temperatures (SSTs) associated with the El Niño–Southern Oscillation is linked to teleconnections with the Northern Annular Mode (NAM). Previous work highlighted that the sign and amplitude of the NAM response to tropical SSTs are controlled by the total wave activity entering the subpolar stratosphere, which depends on the linear interference of planetary wave anomalies with the climatological stationary wave field. This study uses multiple configurations of atmospheric general circulation models to assess the robustness of these linkages to details of the tropical SST forcing and model configuration. Across 23 cases with idealized SST forcing, the amplitudes of the tropical and extratropical wave responses are found to scale approximately linearly with forcing strength. But wave amplitude alone is not sufficient to predict the NAM response. Instead, the spatial structure of the wave response (and hence the linear interference) provides the best explanation of the NAM response in all cases. Linear interference explains most of the total wave activity response even in cases with stronger nonlinear contributions, due to consistent cancellation between quasi‐stationary wave nonlinearity and nonlinearity arising from transient waves. Within this limited set of experiments, there is no evidence for a consistent sensitivity of the NAM response to horizontal resolution or to vertical resolution in the stratosphere. These findings reveal that linear interference provides a robust and reproducible mechanism linking midlatitude wave responses to zonal mean circulation (NAM) responses across a wide variety of forcing cases.
Links between multidecadal and interdecadal climatic oscillations in the North Atlantic and regional climate variability of northern France and England since the 17th century
Authors: Dieppois Bastien , Durand Alain , Fournier Matthieu , Massei Nicolas 
Published: April 2013

AbstractKnowledge of the variability of climate in the past is essential for understanding current climatic changes. Therefore, we investigated two temperature indices and seven rainfall time series of northwestern Europe since the 17th century. Trends and multidecadal to interdecadal variability are similar in England and northern France for temperature, whereas a strong regional contrast is evident between the two regions for rainfall. Multidecadal and interdecadal variability displays several periods of enhanced amplitude for both temperature and rainfall that may be related to large‐scale climate control. On these scales, temperatures in both England and France display phase opposition with the Atlantic Multidecadal Oscillation (AMO) before 1800, while they are in‐phase afterward, as determined by wavelet coherence. On the other hand, the relationships between temperature and the North Atlantic Oscillation (NAO) are weak across multidecadal and interdecadal scales for the whole period under study. For rainfall, coherence with the AMO is observed for scales at around 30–60 years, whereas coherence with the NAO is detected on 50–80 year scales and interdecadal 16–23 year scales. However, relationships between rainfall variability and North Atlantic climate indices are highly contrasted depending on the region considered. Finally, the results of a mixed spectral/empirical orthogonal function analysis of mean sea level pressure on these co‐oscillation time scales highlight not only NAO regimes but also other patterns, explaining a nonnegligible amount of variance during certain time periods.