bluuebunny/crossref_metadata_2025_split huggingface dataset:
Turbulent plumes from a glacier terminus melting in a stratified ocean
Authors: Magorrian Samuel J. , Wells Andrew J. 
Published: June 2016

AbstractThe melting of submerged faces of marine‐terminating glaciers is a key contributor to the glacial mass budget via direct thermodynamic ablation and the impact of ablation on calving. This study considers the behavior of turbulent plumes of buoyant meltwater in a stratified ocean, generated by melting of either near‐vertical calving faces or sloping ice shelves. We build insight by applying a turbulent plume model to describe melting of a locally planar region of ice face in a linearly stratified ocean, in a regime where subglacial discharge is insignificant. The plumes rise until becoming neutrally buoyant, before intruding into the ocean background. For strong stratifications, we obtain leading‐order scaling laws for the flow including the height reached by the plume before intrusion, and the melt rate, expressed in terms of the background ocean temperature and salinity stratifications. These scaling laws provide a new perspective for parameterizing glacial melting in response to a piecewise‐linear discretization of the ocean stratification.
Swell impact on wind stress and atmospheric mixing in a regional coupled atmosphere‐wave model
Authors: Wu Lichuan , Rutgersson Anna , Sahlée Erik , Guo Larsén Xiaoli 
Published: June 2016

AbstractOver the ocean, the atmospheric turbulence can be significantly affected by swell waves. Change in the atmospheric turbulence affects the wind stress and atmospheric mixing over swell waves. In this study, the influence of swell on atmospheric mixing and wind stress is introduced into an atmosphere‐wave‐coupled regional climate model, separately and combined. The swell influence on atmospheric mixing is introduced into the atmospheric mixing length formula by adding a swell‐induced contribution to the mixing. The swell influence on the wind stress under wind‐following swell, moderate‐range wind, and near‐neutral and unstable stratification conditions is introduced by changing the roughness length. Five year simulation results indicate that adding the swell influence on atmospheric mixing has limited influence, only slightly increasing the near‐surface wind speed; in contrast, adding the swell influence on wind stress reduces the near‐surface wind speed. Introducing the wave influence roughness length has a larger influence than does adding the swell influence on mixing. Compared with measurements, adding the swell influence on both atmospheric mixing and wind stress gives the best model performance for the wind speed. The influence varies with wave characteristics for different sea basins. Swell occurs infrequently in the studied area, and one could expect more influence in high‐swell‐frequency areas (i.e., low‐latitude ocean). We conclude that the influence of swell on atmospheric mixing and wind stress should be considered when developing climate models.
Influence of Venus topography on the zonal wind and UV albedo at cloud top level: The role of stationary gravity waves
Authors: Bertaux Jean‐Loup , Khatuntsev I. V. , Hauchecorne A. , Markiewicz W. J. , Marcq E. , Lebonnois S. , Patsaeva M. , Turin A. , Fedorova A. 
Published: June 2016

AbstractBased on the analysis of UV images (at 365 nm) of Venus cloud top (altitude 67 ± 2 km) collected with Venus Monitoring Camera on board Venus Express (VEX), it is found that the zonal wind speed south of the equator (from 5°S to 15°S) shows a conspicuous variation (from −101 to −83 m/s) with geographic longitude of Venus, correlated with the underlying relief of Aphrodite Terra. We interpret this pattern as the result of stationary gravity waves produced at ground level by the uplift of air when the horizontal wind encounters a mountain slope. These waves can propagate up to the cloud top level, break there, and transfer their momentum to the zonal flow. Such upward propagation of gravity waves and influence on the wind speed vertical profile was shown to play an important role in the middle atmosphere of the Earth by Lindzen (1981) but is not reproduced in the current GCM of Venus atmosphere from LMD. (Laboratoire de Météorologie Dynamique)In the equatorial regions, the UV albedo at 365 nm varies also with longitude. We argue that this variation may be simply explained by the divergence of the horizontal wind field. In the longitude region (from 60° to −10°) where the horizontal wind speed is increasing in magnitude (stretch), it triggers air upwelling which brings the UV absorber at cloud top level and decreases the albedo and vice versa when the wind is decreasing in magnitude (compression). This picture is fully consistent with the classical view of Venus meridional circulation, with upwelling at equator revealed by horizontal air motions away from equator: the longitude effect is only an additional but important modulation of this effect. This interpretation is comforted by a recent map of cloud top H2O, showing that near the equator the lower UV albedo longitude region is correlated with increased H2O. We argue that H2O enhancement is the sign of upwelling, suggesting that the UV absorber is also brought to cloud top by upwelling.
Impacts of riparian wetlands on the seasonal variations of watershed‐scale methane budget in a temperate monsoonal forest
Authors: Sakabe Ayaka , Kosugi Yoshiko , Okumi Chika , Itoh Masayuki , Takahashi Kenshi 
Published: June 2016

AbstractForest soils are considered a methane (CH4) sink because dry soils can oxidize CH4; however, previous studies on CH4 fluxes in humid temperate forests indicated a high spatial and temporal variability in CH4 fluxes, especially in CH4 emissions from wet soils close to riparian zones, which can turn the soil of a whole forest from a CH4 sink to a CH4 source. In this study, the spatial and temporal variability of soil CH4 fluxes was investigated in a Japanese coniferous forest, including a riparian wetland and a hillslope water‐unsaturated forest floor, based on multipoint flux measurements using laser‐based CH4 analyzers over a period of 2 years. We identified CH4 emission hot spots (60.2 ± 169.1 nmol m−2 s−1 from 117 sampling points) in the wetland in late summer, while the CH4 absorption rate in the forest floor was comparatively lower (−1.2 ± 1.4 nmol m−2 s−1 from 119 sampling points). The temporal variability of watershed‐scale CH4 flux was amplified by a clear seasonal cycle of soil temperature and rainfall pattern under the Asian monsoon climate. The watershed‐scale CH4 budget showed that the forest turned into a CH4 source during the summer owing to the high and variable CH4 emissions from the riparian wetland and the lower part of the hillslope. Overall, our results indicated that CH4 emissions from small riparian areas are important in controlling forest CH4 dynamics at a watershed scale.
Detection of carbon dioxide leakage during injection in deep saline formations by pressure tomography
Authors: Hu Linwei , Bayer Peter , Brauchler Ralf 
Published: June 2016

AbstractCO2 injected into storage formations may escape to the overlying permeable layers. Mixed‐phase diffusivity, namely the ratio of hydraulic conductivity and specific storage of the phase mixture, declines with increasing CO2 saturation. Thus, it can be an indicator of CO2 leakage. In this study, we perform interference brine or CO2 injection tests in a synthetic model, including a storage reservoir, an above aquifer, and a caprock. Pressure transients derived from an observation well are utilized for a travel‐time based inversion technique. Variations of diffusivity are resolved by inverting early travel time diagnostics, providing an insight of plume development. Results demonstrate that the evolution of CO2 leakage in the above aquifer can be inferred by interpreting and comparing the pressure observations, travel times, and diffusivity tomograms from different times. The extent of the plume in reservoir and upper aquifer are reconstructed by clustering the time‐lapse data sets of the mixed‐phase diffusivity, as the diffusivity cannot be exactly reproduced by the inversion. Furthermore, this approach can be used to address different leaky cases, especially for leakage occurring during the injection.
On edge melting under the Colorado Plateau margin
Authors: Rudzitis Sean , Reid Mary R. , Blichert‐Toft Janne 
Published: June 2016

AbstractAsthenosphere beneath the relatively thin lithosphere of the Basin and Range province appears to be juxtaposed in step‐like fashion against the Colorado Plateau's thick lithospheric keel. Primary to near‐primary basalts are found above this edge, in the San Francisco‐Morman Mountain volcanic fields, north central Arizona, western USA. We show that at least two distinct peridotite‐dominated mantle end‐members contributed to the origin of the basalts. One has paired Nd and Hf isotopic characteristics that cluster near the mantle array and trace element patterns as expected for melts generated in the asthenosphere, possibly in the presence of garnet. The second has isotopic compositions displaced above the εHf ‐ εNd mantle array which, together with its particular trace element characteristics, indicate contributions from hydrogenous sediments and/or melt (carbonatite or silicate)‐related metasomatism. Melt equilibration temperatures obtained from Si‐ and Mg‐thermobarometry are mostly 1340–1425°C and account for the effects of water (assumed to be 2 wt.%) and estimated CO2 (variable). Melt equilibration depths cluster at the inferred location of the lithosphere‐asthenosphere boundary at ∼70–75 km beneath the southwestern margin of the Colorado Plateau but scatter to somewhat greater values (∼100 km). Melt generation may have initiated in or below the garnet‐spinel facies transition zone by edge‐driven convection and continued as mantle and/or melts upwelled, assimilating and sometimes equilibrating with shallower contaminated mantle, until melts were finally extracted.
Global rate and distribution of H2 gas produced by serpentinization within oceanic lithosphere
Authors: Worman Stacey L. , Pratson Lincoln F. , Karson Jeffrey A. , Klein Emily M. 
Published: June 2016

AbstractIt has recently been estimated that serpentinization within continental lithosphere produces H2 at rates comparable to oceanic lithosphere (both are ~1011 mol H2/yr). Here we present a simple model that suggests that H2 production rates along the mid‐oceanic ridge alone (i.e., excluding other marine settings) may exceed continental production by an order of magnitude (~1012 mol H2/yr). In our model, H2 production rates increase with spreading rate and the net thickness of serpentinizing peridotite (S‐P) in a column of lithosphere. Lithosphere with a faster spreading rate therefore requires a relatively smaller net thickness of S‐P to produce H2 at the same rate as lithosphere with a slower rate and greater thickness of S‐P. We apply our model globally, incorporating an inverse relationship between spreading rate and net thickness of S‐P to be consistent with observations that serpentinization is more common within lithosphere spreading at slower rates.
MMS observations of electron‐scale filamentary currents in the reconnection exhaust and near the X line
Authors: Phan T. D. , Eastwood J. P. , Cassak P. A. , Øieroset M. , Gosling J. T. , Gershman D. J. , Mozer F. S. , Shay M. A. , Fujimoto M. , Daughton W. , Drake J. F. , Burch J. L. , Torbert R. B. , Ergun R. E. , Chen L. J. , Wang S. , Pollock C. , Dorelli J. C. , Lavraud B. , Giles B. L. , Moore T. E. , Saito Y. , Avanov L. A. , Paterson W. , Strangeway R. J. , Russell C. T. , Khotyaintsev Y. , Lindqvist P. A. , Oka M. , Wilder F. D. 
Published: June 2016

AbstractWe report Magnetospheric Multiscale observations of macroscopic and electron‐scale current layers in asymmetric reconnection. By intercomparing plasma, magnetic, and electric field data at multiple crossings of a reconnecting magnetopause on 22 October 2015, when the average interspacecraft separation was ~10 km, we demonstrate that the ion and electron moments are sufficiently accurate to provide reliable current density measurements at 30 ms cadence. These measurements, which resolve current layers narrower than the interspacecraft separation, reveal electron‐scale filamentary Hall currents and electron vorticity within the reconnection exhaust far downstream of the X line and even in the magnetosheath. Slightly downstream of the X line, intense (up to 3 μA/m2) electron currents, a super‐Alfvénic outflowing electron jet, and nongyrotropic crescent shape electron distributions were observed deep inside the ion‐scale magnetopause current sheet and embedded in the ion diffusion region. These characteristics are similar to those attributed to the electron dissipation/diffusion region around the X line.
The effect of crack orientation on the nonlinear interaction of a P wave with an S wave
Authors: TenCate J. A. , Malcolm A. E. , Feng X. , Fehler M. C. 
Published: June 2016

AbstractCracks, joints, fluids, and other pore‐scale structures have long been hypothesized to be the cause of the large elastic nonlinearity observed in rocks. It is difficult to definitively say which pore‐scale features are most important, however, because of the difficulty in isolating the source of the nonlinear interaction. In this work, we focus on the influence of cracks on the recorded nonlinear signal and in particular on how the orientation of microcracks changes the strength of the nonlinear interaction. We do this by studying the effect of orientation on the measurements in a rock with anisotropy correlated with the presence and alignment of microcracks. We measure the nonlinear response via the traveltime delay induced in a low‐amplitude P wave probe by a high‐amplitude S wave pump. We find evidence that crack orientation has a significant effect on the nonlinear signal.
Characterization of the submesoscale energy cascade in the Alboran Sea thermocline from spectral analysis of high‐resolution MCS data
Authors: Sallares Valenti , Mojica Jhon F. , Biescas Berta , Klaeschen Dirk , Gràcia Eulàlia 
Published: June 2016

AbstractPart of the kinetic energy that maintains ocean circulation cascades down to small scales until it is dissipated through mixing. While most steps of this downward energy cascade are well understood, an observational gap exists at horizontal scales of 103–101 m that prevents characterizing a key step in the chain: the transition from anisotropic internal wave motions to isotropic turbulence. Here we show that this observational gap can be covered using high‐resolution multichannel seismic (HR‐MCS) data. Spectral analysis of acoustic reflectors imaged in the Alboran Sea thermocline shows that this transition is likely caused by shear instabilities. In particular, we show that the averaged horizontal wave number spectra of the reflectors vertical displacements display three subranges that reproduce theoretical spectral slopes of internal waves (λx > 100 m), Kelvin‐Helmholtz‐type shear instabilities (100 m > λx > 33 m), and turbulence (λx < 33 m), indicating that the whole chain of events is occurring continuously and simultaneously in the surveyed area.
Land surface temperature from INSAT‐3D imager data: Retrieval and assimilation in NWP model
Authors: Singh Randhir , Singh Charu , Ojha Satya P. , Kumar A. Senthil , Kishtawal C. M. , Kumar A. S. Kiran 
Published: June 2016

AbstractA new algorithm is developed for retrieving the land surface temperature (LST) from the imager radiance observations on board geostationary operational Indian National Satellite (INSAT‐3D). The algorithm is developed using the two thermal infrared channels (TIR1 10.3–11.3 µm and TIR2 11.5–12.5 µm) via genetic algorithm (GA). The transfer function that relates LST and thermal radiances is developed using radiative transfer model simulated database. The developed algorithm has been applied on the INSAT‐3D observed radiances, and LST retrieved from the developed algorithm has been validated with Moderate Resolution Imaging Spectroradiometer land surface temperature (LST) product. The developed algorithm demonstrates a good accuracy, without significant bias and standard deviations of 1.78 K and 1.41 K during daytime and nighttime, respectively. The newly proposed algorithm performs better than the operational algorithm used for LST retrieval from INSAT‐3D satellite. Further, a set of data assimilation experiments is conducted with the Weather Research and Forecasting (WRF) model to assess the impact of INSAT‐3D LST on model forecast skill over the Indian region. The assimilation experiments demonstrated a positive impact of the assimilated INSAT‐3D LST, particularly on the lower tropospheric temperature and moisture forecasts. The temperature and moisture forecast errors are reduced (as large as 8–10%) with the assimilation of INSAT‐3D LST, when compared to forecasts that were obtained without the assimilation of INSAT‐3D LST. Results of the additional experiments of comparative performance of two LST products, retrieved from operational and newly proposed algorithms, indicate that the impact of INSAT‐3D LST retrieved using newly proposed algorithm is significantly larger compared to the impact of INSAT‐3D LST retrieved using operational algorithm.
The concurrent variability of East Asian subtropical and polar‐front jets and its implication for the winter climate anomaly in China
Authors: Xiao Chuliang , Zhang Yaocun , Lofgren Brent M. , Nie Yu 
Published: June 2016

AbstractThe variability of East Asian upper level westerly jets in winter is studied with regard to the concurrent existence of subtropical jet (East Asian subtropical jet (EASJ)) and polar‐front jet (East Asian polar‐front jet (EAPJ)) using the National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis. In the distribution of jet occurrence revealed in 6‐hourly data, two jet branches along 30°N and 55°N, corresponding to locations of EASJ and EAPJ, respectively, are separated over the Tibetan Plateau. The leading two modes of zonal‐mean zonal wind in East Asia extracted from a mass‐weighted empirical orthogonal function analysis are characterized by the intensity changes and location displacements of two jets. The key regions for EASJ and EAPJ are then defined to represent variabilities of these two jets. Correlation analysis indicates that the subseasonal variation of EAPJ precedes EASJ by around 5 days, which can be interpreted as wave‐mean flow interactions via synoptic‐scale transient eddy activities. Based on the pentad intensity indices of two jets, the concurrent variabilities of EASJ and EAPJ are investigated with typical temperature and precipitation anomalies in China. The results suggest that by taking account of the two jets, we are able to get a more comprehensive understanding of the winter climate.
Reply to comment by X. X. Zhang et al. on “Three‐dimensional quantification of soil hydraulic properties using X‐ray computed tomography and image‐based modeling”
Authors: Tracy Saoirse R. , Daly Keith R. , Sturrock Craig J. , Crout Neil M. J. , Mooney Sacha J. , Roose Tiina 
Published: June 2016

AbstractIn response to the comment raised by Zhang et al. (2016, doi: 10.1002/2015WR018432) we explore the differences in average velocity computed using slip and no‐slip boundary conditions at the air water interface. We consider a porous medium in which the air phase acts to impede the movement of water rather than to lubricate it, a case closer to the observed distribution of water in our CT images. We find that, whilst the slip boundary condition may be a more accurate approximation, in cases where the air phase is seen to impede water movement the differences between the two approaches are negligible.
Water yield and sediment export in small, partially glaciated Alpine watersheds in a warming climate
Authors: Micheletti Natan , Lane Stuart N. 
Published: June 2016

AbstractClimate change is expected to modify the hydrological and geomorphological dynamics of mountain watersheds significantly, so impacting on downstream water yield and sediment supply. However, such watersheds are often poorly instrumented, making it difficult to link recent and rapid climate change to landscape response. Here we combine unique records of river flow and sediment export, with historical archival imagery to test the hypothesis that climate warming has substantially increased both water yield and sediment export from small Alpine watersheds (<3 km2) characterized by small (<0.5 km2 surface) glaciers. To examine ice and landform response to climate change, we apply archival digital photogrammetry to historical aerial imagery available from 1967 to present. We use the resulting data on ice loss, in combination with reliable records of stream flow from hydroelectric power intakes and climate data to approximate a water budget and to determine the evolution of different contributions to river flow. We use the stream flow records to estimate volumetric sediment transport capacity and compare this with the volumes of sand and gravel exported from the watersheds, quantified from records of intake flushing. The data show clearly that climate forcing since the early 1980s has been accompanied by a net increase in both water yield and sediment transport capacity, and we attribute these as signals of reduced snow accumulation and glacier recession. However, sediment export has not responded in the same way and we attribute this to limits on sediment delivery to streams because of poor rockwall‐hillslope‐channel connectivity. However, we do find that extreme climate conditions can be seen in sediment export data suggesting that these, rather than mean climate warming, may dominate watershed response.
Effect of internal cleavage site mutations in human immunodeficiency virus type 1 capsid protein on its structure and function
Authors: Tóth Ferenc , Kádas János , Mótyán János András , Tőzsér József 
Published: June 2016

The capsid protein of the human immunodeficiency virus type 1 has been found to be a substrate of the retroviral protease in vitro, and its processing was predicted to be strongly dependent on a pH‐induced conformational change. Several protease cleavage sites have been identified within the capsid protein, but the importance of its cleavage by the viral protease at the early phase of infection is controversial. To confirm the relevance of this process, we aimed to design, produce, and characterize mutant capsid proteins, in which the protein susceptibility toward HIV‐1 protease is altered without affecting other steps of the viral life cycle. Our results indicate that while the introduced mutations changed the cleavage rate at the mutated sites of the capsid protein by HIV‐1 protease, some of them caused only negligible or moderate structural changes (A78V, L189F, and L189I). However, the effects of other mutations (W23A, A77P, and L189P) were dramatic, as assessed by secondary structure determination or cyclophilin A‐binding assay. Based on our observations, the L189F mutant capsid remains structurally and functionally unchanged and may therefore be the best candidate for use in studies aimed at better understanding the role of the protease in the early postentry events of viral infection or retrovirus‐mediated gene transduction.