bluuebunny/crossref_metadata_2025_split huggingface dataset:
Subregional characterization of mesoscale eddies across the Brazil‐Malvinas Confluence
Authors: Mason Evan , Pascual Ananda , Gaube Peter , Ruiz Simón , Pelegrí Josep L. , Delepoulle Antoine 
Published: March 2017

AbstractHorizontal and vertical motions associated with coherent mesoscale structures, including eddies and meanders, are responsible for significant global transports of many properties, including heat and mass. Mesoscale vertical fluxes also influence upper ocean biological productivity by mediating the supply of nutrients into the euphotic layer, with potential impacts on the global carbon cycle. The Brazil‐Malvinas Confluence (BMC) is a western boundary current region in the South Atlantic with intense mesoscale activity. This region has an active role in the genesis and transformation of water masses and thus is a critical component of the Atlantic meridional overturning circulation. The collision between the Malvinas and Brazil Currents over the Patagonian shelf/slope creates an energetic front that translates offshore to form a vigorous eddy field. Recent improvements in gridded altimetric sea level anomaly fields allow us to track BMC mesoscale eddies with high spatial and temporal resolutions using an automated eddy tracker. We characterize the eddies across fourteen 5° × 5° subregions. Eddy‐centric composites of tracers and geostrophic currents diagnosed from a global reanalysis of surface and in situ data reveal substantial subregional heterogeneity. The in situ data are also used to compute the evolving quasi‐geostrophic vertical velocity (QG‐ω) associated with each instantaneous eddy instance. The QG‐ω eddy composites have the expected dipole patterns of alternating upwelling/downwelling, however, the magnitude and sign of azimuthally averaged vertical velocity varies among subregions. Maximum eddy values are found near fronts and sharp topographic gradients. In comparison with regional eddy composites, subregional composites provide refined information about mesoscale eddy heterogeneity.
Ship observations and numerical simulation of the marine atmospheric boundary layer over the spring oceanic front in the northwestern South China Sea
Authors: Shi Rui , Chen Ju , Guo Xinyu , Zeng Lili , Li Jian , Xie Qiang , Wang Xin , Wang Dongxiao 
Published: March 2017

AbstractThe response of the marine atmospheric boundary layer (MABL) structure to an oceanic front is analyzed using Global Positioning System (GPS) sounding data obtained during a survey in the northwestern South China Sea (NSCS) over a period of about 1 week in April 2013. The Weather Research and Forecasting (WRF) model is used to further examine the thermodynamical mechanisms of the MABL's response to the front. The WRF model successfully simulates the change in the MABL structure across the front, which agrees well with the observations. The spatially high‐pass‐filtered fields of sea surface temperature (SST) and 10 m neutral equivalent wind from the WRF model simulation show a tight, positive coupling between the SST and surface winds near the front. Meanwhile, the SST front works as a damping zone to reduce the enhancement of wind blowing from the warm to the cold side of the front in the lower boundary layer. Analysis of the momentum budget shows that the most active and significant term affecting horizontal momentum over the frontal zone is the adjustment of the pressure gradient. It is found that the front in the NSCS is wide enough for slowly moving air parcels to be affected by the change in underlying SST. The different thermal structure upwind and downwind of the front causes a baroclinic adjustment of the perturbation pressure from the surface to the midlayer of the MABL, which dominates the change in the wind profile across the front.
The combined risk of extreme tropical cyclone winds and storm surges along the U.S. Gulf of Mexico Coast
Authors: Trepanier J. C. , Yuan J. , Jagger T. H. 
Published: March 2017

AbstractTropical cyclones, with their nearshore high wind speeds and deep storm surges, frequently strike the United States Gulf of Mexico coastline influencing millions of people and disrupting offshore economic activities. The combined risk of occurrence of tropical cyclone nearshore wind speeds and storm surges is assessed at 22 coastal cities throughout the United States Gulf of Mexico. The models used are extreme value copulas fitted with margins defined by the generalized Pareto distribution or combinations of Weibull, gamma, lognormal, or normal distributions. The statistical relationships between the nearshore wind speed and storm surge are provided for each coastal city prior to the copula model runs using Spearman's rank correlations. The strongest significant relationship between the nearshore wind speed and storm surge exists at Shell Beach, LA (ρ= 0.67), followed by South Padre Island, TX (ρ= 0.64). The extreme value Archimedean copula models for each city then provide return periods for specific nearshore wind speed and storm surge pairs. Of the 22 cities considered, Bay St. Louis, MS, has the shortest return period for a tropical cyclone with at least a 50 ms−1nearshore wind speed and a 3 m surge (19.5 years, 17.1‐23.5). The 90% confidence intervals are created by recalculating the return periods for a fixed set of wind speeds and surge levels using 100 samples of the model parameters. The results of this study can be utilized by policy managers and government officials concerned with coastal populations and economic activity in the Gulf of Mexico.
Reducing multisensor monthly mean aerosol optical depth uncertainty: 2. Optimal locations for potential ground observation deployments
Authors: Li Jing , Li Xichen , Carlson Barbara E. , Kahn Ralph A. , Lacis Andrew A. , Dubovik Oleg , Nakajima Teruyuki 
Published: March 2017

AbstractSurface remote sensing of aerosol properties provides “ground truth” for satellite and model validation and is an important component of aerosol observation system. Due to the different characteristics of background aerosol variability, information obtained at different locations usually has different spatial representativeness, implying that the location should be carefully chosen so that its measurement could be extended to a greater area. In this study, we present an objective observation array design technique that automatically determines the optimal locations with the highest spatial representativeness based on the Ensemble Kalman Filter (EnKF) theory. The ensemble is constructed using aerosol optical depth (AOD) products from five satellite sensors. The optimal locations are solved sequentially by minimizing the total analysis error variance, which means that observations at these locations will reduce the background error variance to the largest extent. The location determined by the algorithm is further verified to have larger spatial representativeness than some other arbitrary location. In addition to the existing active Aerosol Robotic Network (AERONET) sites, the 40 selected optimal locations are mostly concentrated on regions with both high AOD inhomogeneity and its spatial representativeness, namely, the Sahel, South Africa, East Asia, and North Pacific Islands. These places should be the focuses of establishing future AERONET sites in order to further reduce the uncertainty in the monthly mean AOD. Observations at these locations contribute to approximately 50% of the total background uncertainty reduction.
Protracted volcanism after large impacts: Evidence from the Sudbury impact basin
Authors: Ubide Teresa , Guyett Paul C. , Kenny Gavin G. , O'Sullivan Edel M. , Ames Doreen E. , Petrus Joseph A. , Riggs Nancy , Kamber Balz S. 
Published: March 2017

AbstractMorphological studies of large impact structures on Mercury, Venus, Mars, and the Moon suggest that volcanism within impact craters may not be confined to the shock melting of target rocks. This possibility prompted reinvestigation of the 1.85 Ga subaqueous Sudbury impact structure, specifically its 1.5 km thick immediate basin fill (Onaping Formation). Historically, breccias of this formation were debated in the context of an endogenic versus an impact‐fallback origin. New field, petrographic, and in situ geochemical data document an array of igneous features, including vitric shards, bombs, sheet‐like intrusions, and peperites, preserved in exquisite textural detail. The geochemistry of vitric materials is affected by alteration, as expected for subaqueous magmatic products. Earlier studies proposed an overall andesitic chemistry for all magmatic products, sourced from the underlying impact melt sheet. The new data, however, suggest progressive involvement of an additional, more magnesian, and volatile‐rich magma source with time. We propose a new working model in which only the lower part of the Onaping Formation was derived by explosive “melt‐fuel‐coolant interaction” when seawater flooded onto the impact melt sheet in the basin floor. By contrast, we suggest that the upper 1000 m were deposited during protracted submarine volcanism and sedimentary reworking. Magma was initially sourced from the impact melt sheet and up stratigraphy, from reservoirs at greater depth. It follows that volcanic deposits in large impact basins may be related to magmatism caused by the impact but not directly associated with the impact‐generated melt sheet.
Characterization of LIBS emission lines for the identification of chlorides, carbonates, and sulfates in salt/basalt mixtures for the application to MSL ChemCam data
Authors: Anderson D. E. , Ehlmann B. L. , Forni O. , Clegg S. M. , Cousin A. , Thomas N. H. , Lasue J. , Delapp D. M. , McInroy R. E. , Gasnault O. , Dyar M. D. , Schröder S. , Maurice S. , Wiens R. C. 
Published: March 2017

AbstractAncient environmental conditions on Mars can be probed through the identification of minerals on its surface, including water‐deposited salts and cements dispersed in the pore space of sedimentary rocks. Laser‐induced breakdown spectroscopy (LIBS) analyses by the Martian rover Curiosity's ChemCam instrument can indicate salts, and ChemCam surveys aid in identifying and selecting sites for further, detailed in situ analyses. We performed laboratory LIBS experiments under simulated Mars conditions with a ChemCam‐like instrument on a series of mixtures containing increasing concentrations of salt in a basaltic background to investigate the potential for identifying and quantifying chloride, carbonate, and sulfate salts found only in small amounts, dispersed in bulk rock with ChemCam, rather than concentrated in veins. Data indicate that the presence of emission lines from the basalt matrix limited the number of Cl, C, and S emission lines found to be useful for quantitative analysis; nevertheless, several lines with intensities sensitive to salt concentration were identified. Detection limits for the elements based on individual emission lines ranged from ~20 wt % carbonate (2 wt % C), ~5–30 wt % sulfate (1–8 wt % S), and ~5–10 wt % chloride (3–6 wt % Cl) depending on the basaltic matrix and/or salt cation. Absolute quantification of Cl, C, and S in the samples via univariate analysis depends on the cation‐anion pairing in the salt but appears relatively independent of matrices tested, following normalization. These results are promising for tracking relative changes in the salt content of bulk rock on the Martian surface with ChemCam.
Alkali trace elements in Gale crater, Mars, with ChemCam: Calibration update and geological implications
Authors: Payré V. , Fabre C. , Cousin A. , Sautter V. , Wiens R. C. , Forni O. , Gasnault O. , Mangold N. , Meslin P.‐Y. , Lasue J. , Ollila A. , Rapin W. , Maurice S. , Nachon M. , Le Deit L. , Lanza N. , Clegg S. 
Published: March 2017

AbstractThe Chemistry Camera (ChemCam) instrument onboard Curiosity can detect minor and trace elements such as lithium, strontium, rubidium, and barium. Their abundances can provide some insights about Mars' magmatic history and sedimentary processes. We focus on developing new quantitative models for these elements by using a new laboratory database (more than 400 samples) that displays diverse compositions that are more relevant for Gale crater than the previous ChemCam database. These models are based on univariate calibration curves. For each element, the best model is selected depending on the results obtained by using the ChemCam calibration targets onboard Curiosity. New quantifications of Li, Sr, Rb, and Ba in Gale samples have been obtained for the first 1000 Martian days. Comparing these data in alkaline and magnesian rocks with the felsic and mafic clasts from the Martian meteorite NWA7533—from approximately the same geologic period—we observe a similar behavior: Sr, Rb, and Ba are more concentrated in soluble‐ and incompatible‐element‐rich mineral phases (Si, Al, and alkali‐rich). Correlations between these trace elements and potassium in materials analyzed by ChemCam reveal a strong affinity with K‐bearing phases such as feldspars, K‐phyllosilicates, and potentially micas in igneous and sedimentary rocks. However, lithium is found in comparable abundances in alkali‐rich and magnesium‐rich Gale rocks. This very soluble element can be associated with both alkali and Mg‐Fe phases such as pyroxene and feldspar. These observations of Li, Sr, Rb, and Ba mineralogical associations highlight their substitution with potassium and their incompatibility in magmatic melts.
Rapid heterogeneous oxidation of organic coatings on submicron aerosols
Authors: Lim C. Y. , Browne E. C. , Sugrue R. A. , Kroll J. H. 
Published: March 2017

AbstractLaboratory studies have found that heterogeneous oxidation can affect the composition and loading of atmospheric organic aerosol particles over time scales of several days, but most studies have examined pure organic particles only. In this study, in order to probe the reactivity of organic species confined near the particle surface, the rates and products of the OH‐initiated oxidation of pure squalane particles are compared to oxidation of thin coatings of squalane on ammonium sulfate particles. The squalane reaction rate constant shows a linear dependence on the organic surface area‐to‐volume ratio, with rate constants for coated particles up to 10 times larger than for pure particles. Changes in the carbon oxidation state and fraction of particulate carbon remaining show similar enhancements, implying that heterogeneous oxidation may exhibit a stronger effect on the loadings and properties of organic aerosol than previously estimated from laboratory studies.
A new view of Jupiter's auroral radio spectrum
Authors: Kurth W. S. , Imai M. , Hospodarsky G. B. , Gurnett D. A. , Louarn P. , Valek P. , Allegrini F. , Connerney J. E. P. , Mauk B. H. , Bolton S. J. , Levin S. M. , Adriani A. , Bagenal F. , Gladstone G. R. , McComas D. J. , Zarka P. 
Published: March 2017

AbstractJuno's first perijove science observations were carried out on 27 August 2016. The 90° orbit inclination and 4163 km periapsis altitude provide the first opportunity to explore Jupiter's polar magnetosphere. A radio and plasma wave instrument on Juno called Waves provided a new view of Jupiter's auroral radio emissions from near 10 kHz to ~30 MHz. This frequency range covers the classically named decametric, hectometric, and broadband kilometric radio emissions, and Juno observations showed much of this entire spectrum to consist of V‐shaped emissions in frequency‐time space with intensified vertices located very close to the electron cyclotron frequency. The proximity of the radio emissions to the cyclotron frequency along with loss cone features in the energetic electron distribution strongly suggests that Juno passed very close to, if not through, one or more of the cyclotron maser instability sources thought to be responsible for Jupiter's auroral radio emissions.
Elastic deformation of the Australian continent induced by seasonal water cycles and the 2010–2011 La Niña determined using GPS and GRACE
Authors: Han Shin‐Chan 
Published: March 2017

AbstractThe solid Earth deforms elastically in response to changes in atmospheric, water, and ice mass load. I present geodetic (Gravity Recovery and Climate Experiment and GPS) observations of continental deformation at seasonal and interannual scales, responding to water and atmospheric cycles in Australia. In the southern summer, the central part of the Australian continent rises by a few millimeter and the north‐south perimeter lengthens by ~1 mm, induced by atmospheric unloading. In winter, the continent subsides and the perimeter shortens due to atmospheric loading. In autumn, increased soil moisture and groundwater result in 7 mm of subsidence in northern Australia and produce a positive slope trending southward. This trend reverses in spring. The La Niña precipitation in 2010–2011 produced widespread subsidence of >10 mm, followed by gradual uplift of 10 mm over the next 3–4 years, as water storage depletes slowly through evapotranspiration. The geodetic measurements find significant imbalance in the water cycle budget in Australia over 2010–2015.
Remagnetization of carbonate rocks in southern Tibet: Perspectives from rock magnetic and petrographic investigations
Authors: Huang Wentao , Lippert Peter C. , Zhang Yang , Jackson Michael J. , Dekkers Mark J. , Li Juan , Hu Xiumian , Zhang Bo , Guo Zhaojie , van Hinsbergen Douwe J. J. 
Published: March 2017

AbstractThe latitudinal motion of the Tibetan Himalaya—the northernmost continental unit of the Indian plate—is a key component in testing paleogeographic reconstructions of the Indian plate before the India‐Asia collision. Paleomagnetic studies of sedimentary rocks (mostly carbonate rocks) from the Tibetan Himalaya are complicated by potentially pervasive yet cryptic remagnetization. Although traditional paleomagnetic field tests reveal some of this remagnetization, secondary remanence acquired prior to folding or tilting easily escapes detection. Here we describe comprehensive rock magnetic and petrographic investigations of Jurassic to Paleocene carbonate and volcaniclastic rocks from Tibetan Himalayan strata (Tingri and Gamba areas). These units have been the focus of several key paleomagnetic studies for Greater Indian paleogeography. Our results reveal that while the dominant magnetic carrier in both carbonate and volcaniclastic rocks is magnetite, their magnetic and petrographic characteristics are distinctly different. Carbonate rocks have “wasp‐waisted” hysteresis loops, suppressed Verwey transitions, extremely fine grain sizes (superparamagnetic), and strong frequency‐dependent magnetic susceptibility. Volcaniclastic rocks exhibit “pot‐bellied” hysteresis loops and distinct Verwey transitions. Electron microscopy reveals that magnetite grains in carbonate rocks are pseudomorphs of early diagenetic pyrite, whereas detrital magnetite is abundant and pyrite is rarely oxidized in the volcaniclastic rocks. We suggest that the volcaniclastic rocks retain a primary remanence, but oxidation of early diagenetic iron sulfide to fine‐grained magnetite has likely caused widespread chemical remagnetization of the carbonate units. We recommend that thorough rock magnetic and petrographic investigations are prerequisites for paleomagnetic studies throughout southern Tibet and everywhere in general.
Ozone and Reactive Oxygen Species
Authors: Krasensky Julia , Carmody Melanie , Sierla Maija , Kangasjärvi Jaakko 
Published: March 2017

Abstract

High tropospheric ozone (O
3
) concentrations affect plant growth and crop yield. O
3
enters leaves through stomata and rapidly degrades in the apoplast into other reactive oxygen species (ROS), which readily interact with surrounding biomolecules. Due to their high reactivity, ROS act as important signalling molecules. Apoplastic ROS perception induces secondary ROS production in other cellular compartments and activates interorganelle signalling pathways towards stress defence. Defence responses include activation of hormonal signalling, the enhancement of antioxidative defence responses, protection of the photosynthetic machinery and induction of cell death processes. Different species prioritise different defence strategies and population studies towards the identification of genetic loci associated with O
3
tolerance are currently the most promising approach for identifying genes involved in O
3
tolerance.

Key Concepts

While the stratospheric O
3
layer has protective UV‐B screening properties, tropospheric O
3
accumulation near the earth's surface is a health hazard to living organisms.

Ozone enters through open stomatal pores in the leaf epidermis and triggers rapid ROS accumulation and complex signalling pathways originating from the apoplastic space between cells.

Acute O
3
exposure in sensitive plants results in visible cell death lesions; long‐term chronic exposures to O
3
levels above 40 ppb leads to a reduction in crop yields due to reduced photosynthesis and disruption to metabolism.

The photosynthetic activity decreases under O
3
exposure and subsequently causes a reduction in CO
2
fixation and central carbohydrate metabolism. Subsequently, catabolic processes are enhanced to re‐mobilise resources, causing early senescence and a shift in source‐sink relations.

ROS are continuously produced during photosynthesis and respiration and ROS production increases under stress conditions. This serves as an important signalling mechanism that initiates defence and acclimation processes.

ROS, calcium and hormones accumulate within different intra‐ and extracellular compartments and act together as signals in a dense and complex signalling network under stress conditions.

Stomatal closure physically blocks the entry of air pollutants or pathogens. Stomatal closure is a defence response, triggered by O
3
and other types of abiotic and biotic stress, measured through stomatal conductance (g
s
).

While harsh stress results in passive cell death, programmed cell death (PCD) is an active defence mechanism that can isolate and contain the spread of diseases to smaller areas of tissue in the plant.

Strategies to increase the tolerance of plants to O
3
include population studies, transgenic approaches as well as the application of protective chemicals.