bluuebunny/crossref_metadata_2025 huggingface dataset:
UV photochemistry of carboxylic acids at the air‐sea boundary: A relevant source of glyoxal and other oxygenated VOC in the marine atmosphere
Authors: Chiu R. , Tinel L. , Gonzalez L. , Ciuraru R. , Bernard F. , George C. , Volkamer R.
Published: December 2016

Photochemistry plays an important role in marine dissolved organic carbon (DOC) degradation, but the mechanisms that convert DOC into volatile organic compounds (VOCs) remain poorly understood. We irradiated carboxylic acids (C7–C9) on a simulated ocean surface with UV light (<320 nm) in a photochemical flow reactor and transferred the VOC products into a dark ozone reactor. Glyoxal was detected as a secondary product from heptanoic, octanoic, and nonanoic acid (NA) films, but not from octanol. Primary glyoxal emissions were not observed, nor was glyoxal formed in the absence of ozone. Addition of a photosensitizer had no noticeable effect. The concurrent detection of heptanal in the NA system suggests that the ozonolysis of 2‐nonenal is the primary chemical mechanism that produces glyoxal. This source can potentially sustain tens of parts per trillion by volume (pptv) glyoxal over oceans, and helps to explain why glyoxal fluxes in marine air are directed from the atmosphere into the ocean.
Spectral analysis of Ahuna Mons from Dawn mission's visible‐infrared spectrometer
Authors: Zambon F. , Raponi A. , Tosi F. , De Sanctis M. C. , McFadden L. A. , Carrozzo F. G. , Longobardo A. , Ciarniello M. , Krohn K. , Stephan K. , Palomba E. , Pieters C. M. , Ammannito E. , Russell C. T. , Raymond C. A.
Published: December 2016

Ahuna Mons is the highest mountain on Ceres. A unique complex in terms of size, shape, and morphology, Ahuna is bordered by flanks of the talus around its summit. Recent work by Ruesch et al. () based on Dawn's Framing Camera images shed light on the possible origin of Ahuna Mons. According to Ruesch et al. (2016), Ahuna Mons is formed by a volcanic process involving the ascent of cryomagma and extrusion onto the surface followed by dome development and subsequent spreading. Here we analyzed in detail the composition of Ahuna Mons, using data acquired by the visible and infrared spectrometer aboard Dawn. The spectral analysis reveals a relatively high abundance of carbonates and a nonhomogeneous variation in carbonate composition and abundance along Ahuna's flanks, associated with a lower amount of the Ceres's ubiquitous NH4‐phyllosilicates over a large portion of the flanks. The grain size is coarser on the flanks than in the surrounding regions, suggesting the presence of fresher material, also compatible with a larger abundance of carbonates. Thermal variations are seen in Ahuna, supporting the evidence of different compactness of the surface regolith in specific locations. Results of the spectral analysis are consistent with a possible cryovolcanic origin which exposed fresher material that slid down on the flanks.
Voluminous eruption from a zoned magma body after an increase in supply rate at Axial Seamount
Authors: Chadwick W. W. , Paduan J. B. , Clague D. A. , Dreyer B. M. , Merle S. G. , Bobbitt A. M. , Caress D. W. , Philip B. T. , Kelley D. S. , Nooner S. L.
Published: December 2016

Axial Seamount is the best monitored submarine volcano in the world, providing an exceptional window into the dynamic interactions between magma storage, transport, and eruption processes in a mid‐ocean ridge setting. An eruption in April 2015 produced the largest volume of erupted lava since monitoring and mapping began in the mid‐1980s after the shortest repose time, due to a recent increase in magma supply. The higher rate of magma replenishment since 2011 resulted in the eruption of the most mafic lava in the last 500–600 years. Eruptive fissures at the volcano summit produced pyroclastic ash that was deposited over an area of at least 8 km2. A systematic spatial distribution of compositions is consistent with a single dike tapping different parts of a thermally and chemically zoned magma reservoir that can be directly related to previous multichannel seismic‐imaging results.
Assessing sensitivities in algorithmic detection of tropical cyclones in climate data
Authors: Zarzycki Colin M. , Ullrich Paul A.
Published: December 2016

This study applies a sensitivity analysis (SA) technique (the Morris method, MM) to an automated Lagrangian tropical cyclone (TC) tracking algorithm used on gridded climate data. MM demonstrates the ability to screen for input parameters defining TCs (such as minimum intensity and lifetime) that contribute significantly to sensitivity in output metrics (such as storm count). The SA is performed by tracking TCs in four different reanalyses. Tracked TC trajectories are compared to a pointwise observational record. Results show that using thermally integrated metrics for isolating TC warm cores is superior to single‐temperature levels. Input thresholds defining TC vortex strength during tracking contribute the most variance in all output metrics. Integrated output metrics (such as accumulated cyclone energy) are less variable than “counting” metrics such as TC frequency. MM greatly reduces the computational requirements for tracker optimization, with tracked TCs demonstrating better hit and false alarm rates than previous studies.
Middle atmosphere dynamical sources of the semiannual oscillation in the thermosphere and ionosphere
Authors: Jones M. , Emmert J. T. , Drob D. P. , Siskind D. E.
Published: December 2016

The strong global semiannual oscillation (SAO) in thermospheric density has been observed for five decades, but definitive knowledge of its source has been elusive. We use the National Center of Atmospheric Research thermosphere‐ionosphere‐mesosphere electrodynamics general circulation model (TIME‐GCM) to study how middle atmospheric dynamics generate the SAO in the thermosphere‐ionosphere (T‐I). The “standard” TIME‐GCM simulates, from first principles, SAOs in thermospheric mass density and ionospheric total electron content that agree well with observed climatological variations. Diagnosis of the globally averaged continuity equation for atomic oxygen ([O]) shows that the T‐I SAO originates in the upper mesosphere, where an SAO in [O] is forced by nonlinear, resolved‐scale variations in the advective, net tidal, and diffusive transport of O. Contrary to earlier hypotheses, TIME‐GCM simulations demonstrate that intra‐annually varying eddy diffusion by breaking gravity waves may not be the primary driver of the T‐I SAO: A pronounced SAO is produced without parameterized gravity waves.
Opal‐CT in chert beneath the toe of the Tohoku margin and its influence on the seismic aseismic transition in subduction zones
Authors: Kameda Jun , Okamoto Atsushi , Sato Kiminori , Fujimoto Koichiro , Yamaguchi Asuka , Kimura Gaku
Published: December 2016

Thick accumulation of chert is a ubiquitous feature of old oceanic plates at convergent margins. In this study, we investigate chert fragments recovered by the Integrated Ocean Drilling Program expedition 343 at the Japan Trench where the 2011 Tohoku‐Oki earthquake (Mw 9.0) occurred. This sample provides a unique opportunity to investigate in situ chert diagenesis at an active subduction margin and its influence on the kinematics of megathrust faulting. Our mineralogical analyses revealed that the chert is characterized by hydrous opal‐CT and may therefore be highly deformable via pressure solution creep and readily accommodate shear strain between the converging plates at driving stresses of kilopascal order. As chert diagenesis advances, any further deformation requires stresses of >100 MPa, given the increasing transport distances for solutes as represented in cherts on land. The chert diagenesis is thus related to the mechanical transition from a weakly to strongly coupled plate interface at this margin.
Geologic influence on induced seismicity: Constraints from potential field data in Oklahoma
Authors: Shah Anjana K. , Keller G. Randy
Published: December 2016

Recent Oklahoma seismicity shows a regional correlation with increased wastewater injection activity, but local variations suggest that some areas are more likely to exhibit induced seismicity than others. We combine geophysical and drill hole data to map subsurface geologic features in the crystalline basement, where most earthquakes are occurring, and examine probable contributing factors. We find that most earthquakes are located where the crystalline basement is likely composed of fractured intrusive or metamorphic rock. Areas with extrusive rock or thick (>4 km) sedimentary cover exhibit little seismicity, even in high injection rate areas, similar to deep sedimentary basins in Michigan and western North Dakota. These differences in seismicity may be due to variations in permeability structure: within intrusive rocks, fluids can become narrowly focused in fractures and faults, causing an increase in local pore fluid pressure, whereas more distributed pore space in sedimentary and extrusive rocks may relax pore fluid pressure.
Earthquake ground motion amplification for surface waves
Authors: Bowden Daniel C. , Tsai Victor C.
Published: December 2016

Surface waves from earthquakes are known to cause strong damage, especially for larger structures such as skyscrapers and bridges. However, common practice in characterizing seismic hazard at a specific site considers the effect of near‐surface geology on only vertically propagating body waves. Here we show that surface waves have a unique and different frequency‐dependent response to known geologic structure and that this amplification can be analytically calculated in a manner similar to current hazard practices. Applying this framework to amplification in the Los Angeles Basin, we find that peak ground accelerations for certain large regional earthquakes are underpredicted if surface waves are not properly accounted for and that the frequency of strongest ground motion amplification can be significantly different. Including surface‐wave amplification in hazards calculations is therefore essential for accurate predictions of strong ground motion for future San Andreas Fault ruptures.
Mapping the conjugate and corotating storm‐enhanced density during 17 March 2013 storm through data assimilation
Authors: Yue Xinan , Wan Weixing , Liu Libo , Liu Jing , Zhang Shunrong , Schreiner William S. , Zhao Biqiang , Hu Lianhuan
Published: December 2016

The storm‐enhanced density (SED) is an electron density enhancement phenomenon extending from the later afternoon at middle latitude to the noontime in high latitude within a narrow band during early stage of geomagnetic storm. Previous investigations were mostly focused on the northern America region due to sparse data coverage in other regions. Recent observational analysis and simulation studies have shown that the SED might be quite complicated both physically and spatial/temporal evolution. In this paper, we obtained the global ionospheric electron density with the spatial/temporal resolution of 5° in latitude, 10° in longitude, ~30 km around F2 peak, and 0.5 h in time, during 17 March 2013 geomagnetic storm through assimilating ground and LEO‐based total electron content (TEC) data into the model. A total of ~450 ground‐based Global Navigation Satellite Systems stations' and ~10 LEO satellites' observations were applied in the assimilation. Of all the data, six satellites with ionospheric radio occultation profiling capability provided the key altitudinal variation information. The SED associated with the tongue of ionization (TOI) and boundary blob can be well identified from the data assimilation results, although their amplitude of enhancement was only up to ~6 TECU (TEC unit, 1 TECU = 1016 el m−2). All structures show very dynamic and complicated time evolution features. During this storm time, we identified two separate SED/TOI/blob structures corotating from Europe to American with conjugate occurrence. This partly supports the mechanism of convection expansion. Given a significant amount of radio occultation will be available in the near future, this method will help up us to resolve global large‐scale ionospheric disturbance down to very small spatial and temporal scale in storm time.
An alternative possibility to equatorial plasma bubble forecasting through mathematical modeling and Digisonde data
Authors: Sousasantos J. , Kherani E. A. , Sobral J. H. A.
Published: December 2016

Equatorial plasma bubbles (EPBs), or large‐scale plasma depleted regions, are one of the subjects of great interest in space weather research since such phenomena have been extensively reported to cause strong degrading effects on transionospheric radio propagation at low latitudes, especially over the Brazilian region, where satellite communication interruptions by the EPBs have been, frequently, registered. One of the most difficult tasks for this field of scientific research is the forecasting of such plasma‐depleted structures. This forecasting capability would be of significant help for users of positioning/navigation systems operating in the low‐latitude/equatorial region all over the world. Recently, some efforts have been made trying to assess and improve the capability of predicting the EPB events. The purpose of this paper is to present an alternative approach to EPB prediction by means of the use of mathematical numerical simulation associated with ionospheric vertical drift, obtained through Digisonde data, focusing on telling beforehand whether ionospheric plasma instability processes will evolve or not into EPB structures. Modulations in the ionospheric vertical motion induced by gravity waves prior to the prereversal enhancement occurrence were used as input in the numerical model. A comparison between the numerical results and the observed EPB phenomena through CCD all‐sky image data reveals a considerable coherence and supports the hypothesis of a capability of short‐term forecasting.
The response of the inner magnetosphere to the trailing edges of high‐speed solar‐wind streams
Authors: Denton M. H. , Borovsky J. E.
Published: December 2016

The effects of the leading edge stream interface of high‐speed solar‐wind streams (HSSs) upon the Earth's magnetosphere have been extensively documented. The arrival of HSSs leads to significant changes in the plasmasphere, plasma sheet, ring current, and radiation belts, during the evolution from slow solar wind to persistent fast solar wind. Studies have also documented effects in the lower ionosphere and the neutral atmosphere. However, only cursory attention has been paid to the trailing‐edge stream interface during the transition back from fast solar wind to slow solar wind. Here we report on the statistical changes that occur in the plasmasphere, plasma sheet, ring current, and electron radiation belt during the passage of the trailing‐edge stream interface of HSSs, when the magnetosphere is in most respects in an extremely quiescent state. Counterintuitively, the peak flux of ~1 MeV electrons is observed to occur at this interface. In contrast, other regions of the magnetosphere demonstrate extremely quiet conditions. As with the leading‐edge stream interface, the occurrence of the trailing‐edge stream interface has a periodicity of 27 days, and hence, understanding the changes that occur in the magnetosphere during the passage of trailing edges of HSSs can lead to improved forecasting and predictability of the magnetosphere as a system.
Investigating the source of near‐relativistic and relativistic electrons in Earth's inner radiation belt
Authors: Turner D. L. , O'Brien T. P. , Fennell J. F. , Claudepierre S. G. , Blake J. B. , Jaynes A. N. , Baker D. N. , Kanekal S. , Gkioulidou M. , Henderson M. G. , Reeves G. D.
Published: December 2016

Using observations from NASA's Van Allen Probes, we study the role of sudden particle enhancements at low L shells (SPELLS) as a source of inner radiation belt electrons. SPELLS events are characterized by electron intensity enhancements of approximately an order of magnitude or more in less than 1 day at L < 3. During quiet and average geomagnetic conditions, the phase space density radial distributions for fixed first and second adiabatic invariants are peaked at 2 < L < 3 for electrons ranging in energy from ~50 keV to ~1 MeV, indicating that slow inward radial diffusion is not the dominant source of inner belt electrons under quiet/average conditions. During SPELLS events, the evolution of electron distributions reveals an enhancement of phase space density that can exceed 3 orders of magnitude in the slot region and continues into the inner radiation belt, which is evidence that these events are an important—and potentially dominant—source of inner belt electrons. Electron fluxes from September 2012 through February 2016 reveal that SPELLS occur frequently (~2.5/month at 200 keV), but the number of observed events decreases exponentially with increasing electron energy for ≥100 keV. After SPELLS events, the slot region reforms due to slow energy‐dependent decay over several day time scales, consistent with losses due to interactions with plasmaspheric hiss. Combined, these results indicate that the peaked phase space density distributions in the inner electron radiation belt result from an “on/off,” geomagnetic‐activity‐dependent source from higher radial distances.
Earthquake supercycles on the Mentawai segment of the Sunda megathrust in the seventeenth century and earlier
Authors: Philibosian Belle , Sieh Kerry , Avouac Jean‐Philippe , Natawidjaja Danny H. , Chiang Hong‐Wei , Wu Chung‐Che , Shen Chuan‐Chou , Daryono Mudrik R. , Perfettini Hugo , Suwargadi Bambang W. , Lu Yanbin , Wang Xianfeng
Published: December 2016

Over at least the past millennium, the Mentawai segment of the Sunda megathrust has failed in sequences of closely timed events rather than in single end‐to‐end ruptures—each the culmination of an earthquake “supercycle.” Here we synthesize the sixteenth‐ and seventeenth‐century coral microatoll records into a chronology of interseismic and coseismic vertical deformation. We identify at least five discrete uplift events in about 1597, 1613, 1631, 1658, and 1703 that likely correspond to large megathrust ruptures. This sequence contrasts with the following supercycle culmination, which involved only two large ruptures in 1797 and 1833. Fault slip modeling suggests that together the five cascading ruptures involved failure of the entire Mentawai segment. Interseismic deformation rates also changed after the onset of the rupture sequence, as they did after the 1797 earthquake. We model this change as an altered distribution of fault coupling, presumably triggered by the ~1597 rupture. We also analyze the far less continuous microatoll record between A.D. 1 and 1500. While we cannot confidently delineate the extent of any megathrust rupture during that period, all evidence suggests that individual major ruptures involve only part of the Mentawai segment, often overlap below the central Mentawai Islands, often trigger coupling changes, and occur in clusters that cumulatively cover the entire Mentawai segment at the culmination of each supercycle. It is clear that each Mentawai rupture sequence evolves uniquely in terms of the order and grouping of asperities that rupture, suggesting heterogeneities in fault frictional properties at the ~100 km scale.
Submarine groundwater discharge and associated nutrient fluxes into the Southern Yellow Sea: A case study for semi‐enclosed and oligotrophic seas‐implication for green tide bloom
Authors: Liu Jian'an , Su Ni , Wang Xilong , Du Jinzhou
Published: December 2016

The biogenic elements concentrations in a coastal bay/estuary are strongly influenced not only by riverine input but also by submarine groundwater discharge (SGD) which has been identified as a typical process of land/ocean interactions in coastal zones. To assess the role of SGD in nutrient fluxes in the Southern Yellow Sea (SYS), 228Ra activities were measured in seawater collected in May 2014. Analyzing the sources and sinks of 228Ra, the flux of excess 228Ra through SGD was estimated to be (2.2 ± 1.0) ×1015 dpm yr−1. Based on the 228Ra mass balance model, we estimated the average SGD flux to be approximately (1.3 ± 0.87) ×1012 m3 yr−1 over the entire SYS, which is at least 3.3 times the estimated annual delivery from the Changjiang River into the SYS (∼1.3 × 1011 m3 yr−1). The SGD‐derived biogenic elements loads (dissolved inorganic nitrogen (DIN), phosphorus (DIP) and silicon (DSi)) were estimated as (487 ± 384) × 109 mol yr−1, (2.8 ± 2.2) × 109 mol yr−1, and (313 ± 259) × 109 mol yr−1, respectively, which are approximately 18 times, 7 times and 13 times the riverine input from both mainland China and Korea. The accumulation nutrient fluxes derived by SGD may play one of the most important roles in the green tide bloom that originated from the Subei Shoal zone in the SYS. Additionally, DIN and DIP via SGD can provide the necessary amounts of nutrient for recovering nutrient concentrations to normal levels after the green tide bloom is terminated.
Impact of DYNAMO observations on NASA GEOS‐5 reanalyses and the representation of MJO initiation
Authors: Achuthavarier D. , Wang H. , Schubert S. D. , Sienkiewicz M.
Published: December 2016

This study examines the impact of the Dynamics of the Madden‐Julian Oscillation (DYNAMO) campaign in situ observations on NASA Goddard Earth Observing System version 5 (GEOS‐5) reanalyses and the improvements gained thereby in the representation of the Madden‐Julian Oscillation (MJO) initiation processes. To this end, we produced a global, high‐resolution (1/4° spatially) reanalysis that assimilates the level‐4, quality‐controlled DYNAMO upper air soundings from about 87 stations in the equatorial Indian Ocean region along with a companion data‐denied control reanalysis. The DYNAMO reanalysis produces a more realistic vertical structure of the temperature and moisture in the central tropical Indian Ocean by correcting the model biases, namely, the cold and dry biases in the lower troposphere and warm bias in the upper troposphere. The reanalysis horizontal winds are substantially improved, in that, the westerly acceleration and vertical shear of the zonal wind are enhanced. The DYNAMO reanalysis shows enhanced low‐level diabatic heating, moisture anomalies and vertical velocity during the MJO initiation. Due to the warmer lower troposphere, the deep convection is invigorated, which is evident in convective cloud fraction. The GEOS‐5 atmospheric general circulation model (AGCM) employed in the reanalysis is overall successful in assimilating the additional DYNAMO observations, except for an erroneous model response for medium rain rates, between 700 and 600 hPa, reminiscent of a bias in earlier versions of the AGCM. The moist heating profile shows a sharp decrease there due to the excessive convective rain re‐evaporation, which is partly offset by the temperature increment produced by the analysis.
Downward solar global irradiance at the surface in São Paulo city—The climatological effects of aerosol and clouds
Authors: Yamasoe M. A. , do Rosário N. M. E. , Barros K. M.
Published: December 2016

We analyzed the variability of downward solar irradiance reaching the surface at São Paulo city, Brazil, and estimated the climatological aerosol and cloud radiative effects. Eleven years of irradiance were analyzed, from 2005 to 2015. To distinguish the aerosol from the cloud effect, the radiative transfer code LibRadtran was used to calculate downward solar irradiance. Two runs were performed, one considering only ozone and water vapor daily variability, with AOD set to zero and the second allowing the three variables to change, according to mean climatological values. The difference of the 24 h mean irradiance calculated with and without aerosol resulted in the shortwave aerosol direct radiative effect, while the difference between the measured and calculated, including the aerosol, represented the cloud effect. Results showed that, climatologically, clouds can be 4 times more effective than aerosols. The cloud shortwave radiative effect presented a maximum reduction of about −170 W m−2 in January and a minimum in July, of −37 W m−2. The aerosol direct radiative effect was maximum in spring, when the transport of smoke from the Amazon and central parts of South America is frequent toward São Paulo. Around mid‐September, the 24 h radiative effect due to aerosol only was estimated to be −50 W m−2. Throughout the rest of the year, the mean aerosol effect was around −20 W m−2 and was attributed to local urban sources. The effect of the cloud fraction on the cloud modification factor, defined as the ratio of all‐sky irradiation to cloudless sky irradiation, showed dependence on the cloud height. Low clouds presented the highest impact while the presence of high clouds only almost did not affect solar transmittance, even in overcast conditions.
Water isotope diffusion in the WAIS Divide ice core during the Holocene and last glacial
Authors: Jones T. R. , Cuffey K. M. , White J. W. C. , Steig E. J. , Buizert C. , Markle B. R. , McConnell J. R. , Sigl M.
Published: December 2016

We use a high‐resolution water isotope record from the West Antarctic Ice Sheet Divide ice core (WDC) to evaluate the effects of water isotope diffusion for the last 29 ka B.P. Using spectral analysis of the data, we determine diffusion lengths in depth and time domains. The diffusion length quantifies the mean cumulative diffusive displacement of water molecules relative to their original location at time of deposition. We simulate the observed signal with models and find that our understanding of processes and conditions in the ice sheet is incomplete. With the effects of ice‐deformational thinning removed, portions of the Holocene record show total diffusion lengths smaller than predicted for a lower limit case of diffusion through a single ice crystal. Such reduced diffusion is probably due to structural features such as crusts and tortuous porosity that inhibit vapor transport in the firn. In the late glacial portion of the record, diffusion lengths double between ~19.5 and 17 ka B.P. Known dependencies of diffusion on climatic variables do not account for this enhancement in models, and we hypothesize that it could arise from thermal gradients in the firn column, impurity‐driven enhancement of solid ice diffusion, or changes in firn grain properties that alter vapor access to open pores. Despite model uncertainties, the WDC diffusion length chronology will be an essential input to future studies of high‐frequency variability in the water isotope climate record, as it allows for the effects of diffusion to be removed.
Repeated surveys reveal nontectonic exposure of supposedly active normal faults in the central Apennines, Italy
Authors: Kastelic Vanja , Burrato Pierfrancesco , Carafa Michele M. C. , Basili Roberto
Published: December 2016

We investigate the geomorphic processes that expose bedrock fault surfaces from under their slope‐deposit cover in the central Apennines (Italy). These bedrock fault surfaces are generally located at various heights on mountain fronts above the local base level of glacio‐fluvial valleys and intermountain fluvio‐lacustrine basins and are laterally confined to the extent of related mountain fronts. The process that led to the exposure of fault surfaces has often been exclusively attributed to coseismic earthquake slip and used as proxy for tectonic slip rates and earthquake recurrence estimations. We present the results of monitoring the contact between the exposed fault surfaces and slope deposits at 23 measurement points on 12 different faults over 3.4 year long observation period. We detected either downward or upward movements of the slope deposit with respect to the fault surface between consecutive measurements. During the entire observation period all points, except one, registered a net downward movement in the 2.9–25.6 mm/yr range, resulting in the progressive exposure of the fault surface. During the monitoring period no major earthquakes occurred in the region, demonstrating that the measured exposure process is disconnected from seismic activity. Our results indicate that the fault surface exposure rates are rather due to gravitational and landsliding movements aided by weathering and slope degradation processes. The so far neglected slope degradation and other (sub)surface processes should thus be carefully taken into consideration before attempting to recover fault slip rates using surface gathered data.
Quantitative reconstruction of Holocene sea ice and sea surface temperature off West Greenland from the first regional diatom data set
Authors: Krawczyk D. W. , Witkowski A. , Moros M. , Lloyd J. M. , Høyer J. L. , Miettinen A. , Kuijpers A.
Published: December 2016

Holocene oceanographic conditions in Disko Bay, West Greenland, were reconstructed from high‐resolution diatom records derived from two marine sediment cores. A modern data set composed of 35 dated surface sediment samples collected along the West Greenland coast accompanied by remote sensing data was used to develop a diatom transfer function to reconstruct April sea ice concentration (SIC) supported by July sea surface temperature (SST) in the area. Our quantitative reconstruction shows that oceanographic changes recorded throughout the last ~11,000 years reflect seasonal interplay between spring (April SIC) and summer (July SST) conditions. Our records show clear correlation with climate patterns identified from ice core data from GISP2 and Agassiz‐Renland for the early to middle Holocene. The early Holocene deglaciation of western Greenland Ice Sheet was characterized in Disko Bay by initial strong centennial‐scale fluctuations in April SIC with amplitude of over 40%, followed by high April SIC and July SST. These conditions correspond to a general warming of the climate in the Northern Hemisphere. A decrease in April SIC and July SST was recorded during the Holocene Thermal Optimum reflecting more stable spring‐summer conditions in Disko Bay. During the late Holocene, high April SIC characterized the Medieval Climate Anomaly, while high July SST prevailed during the Little Ice Age, supporting previously identified antiphase relationship between surface waters in West Greenland and climate in NW Europe. This antiphase pattern might reflect seasonal variations in regional oceanographic conditions and large‐scale fluctuations within the North Atlantic Oscillation and Atlantic Meridional Overturning Circulation.
Decadal variations in groundwater quality: A legacy from nitrate leaching and denitrification by pyrite in a sandy aquifer
Authors: Jessen Søren , Postma Dieke , Thorling Lærke , Müller Sascha , Leskelä Jari , Engesgaard Peter
Published: December 2016

Twenty‐five years of groundwater quality monitoring in a sandy aquifer beneath agricultural fields showed large temporal and spatial variations in major ion groundwater chemistry, which were linked closely to the nitrate (NO3) content of agricultural recharge. Between 1988 and 2013, the NO3 content of water in the oxidized zone of the aquifer nearly halved, following implementation of action plans to reduce N leaching from agriculture. However, due to denitrification by pyrite oxidation in the aquifer, a plume of sulfate‐rich water migrates through the aquifer as a legacy of the historical NO3 loading. Agriculture thus is an important determinant of major ion groundwater chemistry. Temporal and spatial variations in the groundwater quality were simulated using a 2D reactive transport model, which combined effects of the historical NO3 leaching and denitrification, with dispersive mixing into the pristine groundwater residing deeper in the aquifer. Reactant‐to‐product ratios across reaction fronts are altered by dispersive mixing and transience in reactant input functions. Modelling therefore allowed a direct comparison of observed and simulated ratios of concentrations of NO3 (reactant) in the oxidized zone to those of SO4 (product) in the reduced zone, which aided a stoichiometric assessment of the mechanisms of denitrification. Denitrification by pyrite in the Rabis Creek aquifer results in oxidation of S−1 and Fe2+ in pyrite to S6+ in dissolved SO4 and Fe3+ in Fe‐oxide. Neither precipitation of elemental sulfur (S0), nor of jarosite, was supported by observations, and adsorption of sulfate was also dismissed.
Multiple outflows, spatial components, and nonlinearities in age theory
Authors: Calabrese Salvatore , Porporato Amilcare
Published: December 2016

Water age has become an important variable for the characterization of hydrologic systems. The goal of this paper is to analyze the role of multiple outflows, spatial components, and nonlinearities in age theory. We first extend the theory to linear systems with multiple outflows, including the relationship between age distribution at death and survival time distribution at birth. We further show that for each outflow there is a survival time distribution at birth, which normalized corresponds to the impulse‐response function for the specific outflow. We also analyze how the impulse‐response function affects both the amplitude gain and time delay of the outflow and the long‐term average partitioning. With regard to linear spatially extended systems, we link the impulse‐response function to the Green's function. This allows us to easily compute the loss function and the age distribution for the system. Finally, we focus on nonlinear systems to analyze the effects of storage‐dependent and age distribution‐dependent loss functions. By considering the Burgers' equation, we show how the relationships between spatial dynamics and the age distribution are complicated by nonlinearities.
An analytical test case for snow models
Authors: Clark Martyn P. , Nijssen Bart , Luce Charles H.
Published: December 2016

This paper develops general analytical solutions for examples of water movement through snow and compares the derived analytical solutions to numerical simulations from a coupled energy and mass balance model. The intended use of the test cases is to evaluate the impact of different numerical approximations, especially different vertical discretization strategies and different time stepping schemes. The analytical solutions provide both outflow from the snowpack, as well as vertical profiles of temperature and volumetric liquid water content at different times throughout the analysis period. The derived analytical solutions have close correspondence with model simulations in most cases. The most pronounced differences between the numerical simulations and the analytical solutions are for the fresh snow test case, where the numerical simulations predict earlier arrival of snowpack outflow. The analytical solutions provide a useful test case for physically motivated snow models because the solutions can be used to evaluate the coupling of hydrology and thermodynamics as well as the unsaturated flow of water through porous media.
Measuring household consumption and waste in unmetered, intermittent piped water systems
Authors: Kumpel Emily , Woelfle‐Erskine Cleo , Ray Isha , Nelson Kara L.
Published: December 2016

Measurements of household water consumption are extremely difficult in intermittent water supply (IWS) regimes in low‐ and middle‐income countries, where water is delivered for short durations, taps are shared, metering is limited, and household storage infrastructure varies widely. Nonetheless, consumption estimates are necessary for utilities to improve water delivery. We estimated household water use in Hubli‐Dharwad, India, with a mixed‐methods approach combining (limited) metered data, storage container inventories, and structured observations. We developed a typology of household water access according to infrastructure conditions based on the presence of an overhead storage tank and a shared tap. For households with overhead tanks, container measurements and metered data produced statistically similar consumption volumes; for households without overhead tanks, stored volumes underestimated consumption because of significant water use directly from the tap during delivery periods. Households that shared taps consumed much less water than those that did not. We used our water use calculations to estimate waste at the household level and in the distribution system. Very few households used 135 L/person/d, the Government of India design standard for urban systems. Most wasted little water even when unmetered, however, unaccounted‐for water in the neighborhood distribution systems was around 50%. Thus, conservation efforts should target loss reduction in the network rather than at households.
Unsaturated hydraulic properties of Sphagnum moss and peat reveal trimodal pore‐size distributions
Authors: Weber Tobias K. D. , Iden Sascha C. , Durner Wolfgang
Published: December 2016

In ombrotrophic peatlands, the moisture content of the vadose zone (acrotelm) controls oxygen diffusion rates, redox state, and the turnover of organic matter. Whether peatlands act as sinks or sources of atmospheric carbon thus relies on variably saturated flow processes. The Richards equation is the standard model for water flow in soils, but it is not clear whether it can be applied to simulate water flow in live Sphagnum moss. Transient laboratory evaporation experiments were conducted to observe evaporative water fluxes in the acrotelm, containing living Sphagnum moss, and a deeper layer containing decomposed moss peat. The experimental data were evaluated by inverse modeling using the Richards equation as process model for variably‐saturated flow. It was tested whether water fluxes and time series of measured pressure heads during evaporation could be simulated. The results showed that the measurements could be matched very well providing the hydraulic properties are represented by a suitable model. For this, a trimodal parametrization of the underlying pore‐size distribution was necessary which reflects three distinct pore systems of the Sphagnum constituted by inter‐, intra‐, and inner‐plant water. While the traditional van Genuchten‐Mualem model led to great discrepancies, the physically more comprehensive Peters‐Durner‐Iden model which accounts for capillary and noncapillary flow, led to a more consistent description of the observations. We conclude that the Richards equation is a valid process description for variably saturated moisture fluxes over a wide pressure range in peatlands supporting the conceptualization of the live moss as part of the vadose zone.
A platform for probabilistic Multimodel and Multiproduct Streamflow Forecasting
Authors: Roy Tirthankar , Serrat‐Capdevila Aleix , Gupta Hoshin , Valdes Juan
Published: December 2016

We develop and test a probabilistic real‐time streamflow‐forecasting platform, Multimodel and Multiproduct Streamflow Forecasting (MMSF), that uses information provided by a suite of hydrologic models and satellite precipitation products (SPPs). The SPPs are bias‐corrected before being used as inputs to the hydrologic models, and model calibration is carried out independently for each of the model‐product combinations (MPCs). Forecasts generated from the calibrated models are further bias‐corrected to compensate for the deficiencies within the models, and then probabilistically merged using a variety of model averaging techniques. Use of bias‐corrected SPPs in streamflow forecasting applications can overcome several issues associated with sparsely gauged basins and enable robust forecasting capabilities. Bias correction of streamflow significantly improves the forecasts in terms of accuracy and precision for all different cases considered. Results show that the merging of individual forecasts from different MPCs provides additional improvements. All the merging techniques applied in this study produce similar results, however, the Inverse Weighted Averaging (IVA) proves to be slightly superior in most cases. We demonstrate the implementation of the MMSF platform for real‐time streamflow monitoring and forecasting in the Mara River basin of Africa (Kenya & Tanzania) in order to provide improved monitoring and forecasting tools to inform water management decisions.
Phase exposure‐dependent exchange
Authors: Ginn T. R. , Schreyer L. G. , Zamani K.
Published: December 2016

Solutes and suspended material often experience delays during exchange between phases one of which may be moving. Consequently transport often exhibits combined effects of advection/dispersion, and delays associated with exchange between phases. Such processes are ubiquitous and include transport in porous/fractured media, watersheds, rivers, forest canopies, urban infrastructure systems, and networks. Upscaling approaches often treat the transport and delay mechanisms together, yielding macroscopic “anomalous transport” models. When interaction with the immobile phase is responsible for the delays, it is not the transport that is anomalous, but the lack of it, due to delays. We model such exchanges with a simple generalization of first‐order kinetics completely independent of transport. Specifically, we introduce a remobilization rate coefficient that depends on the time in immobile phase. Memory‐function formulations of exchange (with or without transport) can be cast in this framework, and can represent practically all time‐nonlocal mass balance models including multirate mass transfer and its equivalent counterparts in the continuous time random walk and time‐fractional advection dispersion formalisms, as well as equilibrium exchange. Our model can address delayed single‐/multievent remobilizations as in delay‐differential equations and periodic remobilizations that may be useful in sediment transport modeling. It is also possible to link delay mechanisms with transport if so desired, or to superpose an additional source of nonlocality through the transport operator. This approach allows for mechanistic characterization of the mass transfer process with measurable parameters, and the full set of processes representable by these generalized kinetics is a new open question.
Activation of PPARγ by baicalin attenuates pulmonary hypertension in an infant rat model by suppressing HMGB1/RAGE signaling
Authors: Chen Zhenjie , Wang Qiuxia
Published: December 2016

Pulmonary hypertension (PH) is a vascular disease, and proinflammatory factors are strongly implicated in its pathogenesis, causing right ventricular (RV) hypertrophy and heart failure. Baicalin exhibits potent anti‐inflammation activity. This study aimed to investigate the curative effects of baicalin in an infant rodent model of PH and to further explore the underlying mechanisms. A PH model in infant rats was induced by hypoxia and the resulting rats were administered baicalin in incremental dosages. Invasive hemodynamic methods were used to measure mean pulmonary arterial pressure (mPAP) and RV end‐diastolic pressure (RVEDP). RV hypertrophy was assessed by mass pathology and histology. ELISAs were used to determine concentrations of high‐mobility group box 1 (HMGB1), secretory receptor for advanced glycation end products (sRAGE), interleukin 6 (IL6) and transforming growth factor β (TGFβ1) in bronchoalveolar lavage fluid (BALF). Electrophoretic mobility shift and phosphorylation in nuclear extracts were used to evaluate the activation of peroxisome proliferator‐activated receptor γ (PPARγ). Western blotting was used to detect the expression levels of heme oxygenase 1 (HO1), HMGB1, RAGE, IL6 and TGFβ1 in lung tissue. Baicalin administration significantly attenuated mPAP, RVEDP and RV hypertrophy in infant rats with PH. HMGB1, sRAGE, IL6 and TGFβ1 levels in BALF were also reduced by baicalin treatment. Baicalin activated PPARγ, which promoted expression of HO1. Furthermore, expression levels of HMGB1, RAGE, IL6 and TGFβ1 in lung tissue were dramatically decreased by baicalin in a dosage‐dependent manner. Baicalin showed curative effects in infant rats with PH. Activation of PPARγ that inhibited HMGB1/RAGE inflammatory signaling was involved.
Characterization and Comparison of Inconel 625 Processed by Selective Laser Melting and Laser Metal Deposition
Authors: Marchese Giulio , Garmendia Colera Xabier , Calignano Flaviana , Lorusso Massimo , Biamino Sara , Minetola Paolo , Manfredi Diego
Published: December 2016

Inconel 625 (IN625) is a Ni superalloy ideal for the aeronautic and aerospace industries because of its superior mechanical and corrosion resistance properties. However, the production of components with complex geometries by traditional processes is very expensive, so additive manufacturing (AM) technologies can be applied to reduce the costs. In this work, IN625 alloy is processed by two different AM processes: selective laser melting (SLM) and laser metal deposition (LMD). First, the different powders are characterized, and then a parameter optimization is performed to obtain the highest possible density (over 99.8%) and hardness, showing very fine microstructures. The LMD process allows the highest build‐up rate, but results in less dimensional accuracy and a lower hardness than the SLM process.
In Situ Multimodality Imaging of Cancerous Cells Based on a Selective Performance of Fe2+‐Adsorbed Zeolitic Imidazolate Framework‐8
Authors: Du Tianyu , Zhao Chunqiu , ur Rehman Fawad , Lai Lanmei , Li Xiaoqi , Sun Yi , Luo Shouhua , Jiang Hui , Gu Ning , Selke Matthias , Wang Xuemei
Published: December 2016

Metal‐organic frameworks possess tremendous potential in biomedical areas for their particular structure. In this study, the authors explored Fe2+‐adsorbed nanoscaled zeolitic imidazolate framework‐8 (ZIF‐8) for in vivo multimodal imaging of cancerous cells for early diagnosis of target cancers. The observations demonstrate that adding Fe2+ into the suspension of ZIF‐8 can neutralize the alkalinity and lower toxicity, while the Fe2+‐adsorbed ZIF‐8 can readily transform to fluorescence ZnO and super paramagnetic Fe3O4 under the synergistic reaction of ROS, GSH, and acids. It is evident that the formation of the nanoclusters ZnO and Fe3O4 only occurred in cancerous cells and does not take place in normal cells, which can be attributed to the different ROS levels and specific micro‐environment in tumor and normal cells. This raises the possibility for the Fe2+‐adsorbed zeolitic imidazolate frameworks to act as promising agents for the in vivo multimodal imaging of cancers in their early stage.
Chiral Induction in Intramolecular Rhodium‐Catalyzed [2+2+2] Cycloadditions of Optically Active Allene–ene/yne–allene Substrates
Authors: Haraburda Ewelina , Fernández Martí , Gifreu Anna , Garcia Jordi , Parella Teodor , Pla‐Quintana Anna , Roglans Anna
Published: December 2016

Allene‐yne‐allene and allene‐ene‐allene N‐tosyl‐linked substrates with two chiral centres in the α‐position of the allene moiety were satisfactorily prepared starting both from racemic and chiral propargylic alcohols. The Wilkinson's complex‐catalyzed [2+2+2] cycloaddition reaction of these substrates was evaluated. In the case of enantiomerically pure bisallenes, high stereoselectivity was observed, giving a diastereomerically pure cycloadduct. The chirality of starting bisallene substrates can be completely transferred to the cycloadducts, representing an atom‐economical and enantiospecific process for the construction of fused polycycles. However, when reacting an oxygen‐linked allene‐ene‐allene substrate, the stereoselectivity decreased and two diastereoisomers were formed. A detailed characterization study of the resulting cycloadducts allowed us to identify the enantioisomer generated in the cycloaddition.

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