bluuebunny/crossref_metadata_2025_split huggingface dataset:
The temporal evolution of a long‐lived contrail cirrus cluster: Simulations with a global climate model
Authors: Bock Lisa , Burkhardt Ulrike 
Published: March 2016

AbstractThe representation of contrail cirrus in climate models has advanced in the last years tremendously. Nevertheless, uncertainties in particular regarding the representation of contrail microphysics still remain. Properties of young contrail cirrus differ from those of natural cirrus due to the large ice crystal number concentration common in contrails. Consequently, microphysical process rates in contrail cirrus, which control its lifetime, can be very different to those in natural cirrus. We extend a contrail cirrus scheme within a climate model by implementing a microphysical two‐moment scheme and study the life cycle of a contrail cirrus cluster. In an idealized experiment we study the properties and microphysical process rates of a contrail cirrus cluster in a large and long‐lived ice supersaturated region. We find that at flight level contrail cirrus display their typical high ice crystal number concentration (of about 10–100 cm−3) for a few hours with far lower densities in lower levels caused by sedimentation. After about 7 h contrail cirrus have spread considerably so that even at flight level associated ice crystal number concentrations have dropped to values that prohibit fast relaxation of ice supersaturation. The reduced ice crystal number and the resulting limited water uptake in the contrail cirrus limit the lifetime of the contrail cirrus cluster to about 10 h even though surrounding conditions would be still favorable for contrail cirrus persistence. In our case studies, contrail cirrus resembles natural cirrus regarding their ice crystal number concentration and size after 5–7 h.
Using satellite data to estimate partial pressure of CO2 in the Baltic Sea
Authors: Parard Gaëlle , Charantonis Anastase Alexandre , Rutgersson Anna 
Published: March 2016

AbstractIn this study we focused on estimating the pressure partial of CO2 (pCO2) in the entire Baltic Sea which can be considered a coastal area in its entirety. We used the self‐organizing multiple linear output (SOMLO) method to estimate the ocean surface pCO2 in the Baltic Sea from the remotely sensed sea surface temperature, chlorophyll a, colored dissolved organic matter, net primary production, and mixed‐layer depth. Uncertainties in the estimates include sparsity of in situ data used to train the algorithms, in particular, for some sectors and seasons. For this application we divided the Baltic Sea in four basins. When comparing the results obtained with this division to those obtained in previous studies, we notice a decrease in the root‐mean‐square error (<40 μatm) between the reconstruction of the pCO2 and their corresponding in situ measurements, as well as an increase of the correlation coefficient (> 0.96) between them. The outputs of this research have a horizontal resolution of 4 km and cover the 1998–2011 period. For the first time, a climatological mean distribution of surface water pCO2 over the Baltic Sea was calculated based on the SOMLO method with a mean pCO2 of 368.3 ± 100 μatm, and a range of 234–514 μatm. The seasonal variability is similar throughout the Baltic Sea, being high in winter and low in summer.
Riparian zones attenuate nitrogen loss following bark beetle‐induced lodgepole pine mortality
Authors: Biederman Joel A. , Meixner Thomas , Harpold Adrian A. , Reed David E. , Gutmann Ethan D. , Gaun Janelle A. , Brooks Paul D. 
Published: March 2016

AbstractA North American bark beetle infestation has killed billions of trees, increasing soil nitrogen and raising concern for N loss impacts on downstream ecosystems and water resources. There is surprisingly little evidence of stream N response in large basins, which may result from surviving vegetation uptake, gaseous loss, or dilution by streamflow from unimpacted stands. Observations are lacking along hydrologic flow paths connecting soils with streams, challenging our ability to determine where and how attenuation occurs. Here we quantified biogeochemical concentrations and fluxes at a lodgepole pine‐dominated site where bark beetle infestation killed 50–60% of trees. We used nested observations along hydrologic flow paths connecting hillslope soils to streams of up to third order. We found soil water NO3 concentrations increased 100‐fold compared to prior research at this and nearby southeast Wyoming sites. Nitrogen was lost below the major rooting zone to hillslope groundwater, where dissolved organic nitrogen (DON) increased by 3–10 times (mean 1.65 mg L−1) and NO3‐N increased more than 100‐fold (3.68 mg L−1) compared to preinfestation concentrations. Most of this N was removed as hillslope groundwater drained through riparian soils, and NO3 remained low in streams. DON entering the stream decreased 50% within 5 km downstream, to concentrations typical of unimpacted subalpine streams (~0.3 mg L−1). Although beetle outbreak caused hillslope N losses similar to other disturbances, up to 5.5 kg ha−1y−1, riparian and in‐stream removal limited headwater catchment export to <1 kg ha−1y−1. These observations suggest riparian removal was the dominant mechanism preventing hillslope N loss from impacting streams.
Origin and temporal variability of unusually low δ13C‐DOC values in two High Arctic catchments
Authors: Hindshaw R. S. , Lang S. Q. , Bernasconi S. M. , Heaton T. H. E. , Lindsay M. R. , Boyd E. S. 
Published: March 2016

AbstractThe stable carbon isotopic composition of dissolved organic matter (δ13C‐DOC) reveals information about its source and extent of biological processing. Here we report the lowest δ13C‐DOC values (−43.8‰) measured to date in surface waters. The streams were located in the High Arctic, a region currently experiencing rapid changes in climate and carbon cycling. Based on the widespread occurrence of methane cycling in permafrost regions and the detection of the pmoA gene, a proxy for aerobic methanotrophs, we conclude that the low δ13C‐DOC values are due to organic matter partially derived from methanotrophs consuming biologically produced, 13C‐depleted methane. These findings demonstrate the significant impact that biological activity has on the stream water chemistry exported from permafrost and glaciated environments in the Arctic. Given that the catchments studied here are representative of larger areas of the Arctic, occurrences of low δ13C‐DOC values may be more widespread than previously recognized, with implications for understanding C cycling in these environments.
Antenna selection in a SIMO architecture for HF radio links
Authors: Erhel Yvon , Lemur Dominique , Oger Martial , Le Masson Jérôme 
Published: March 2016

AbstractThis work takes place in the global design of a SIMO architecture (single input multiple output) for transhorizon radio links, aiming at a significant increase in the data rate when compared with standard modems based in general on a SISO scheme (single input single output). The project is subject to available space constraints at the receive end, involving mobile stations or onboard implementation. We consider solutions that appear as extensions of the compact and heterogeneous antenna array that we proposed previously: collocated antennas of different types are set up with the same phase center and present diversity in their polarization sensitivities to make array processing effective. Given the number NC of receive channels, we address the problem of selecting the most effective antennas in a set of NA possible candidates including monopoles, dipoles, loop antennas with various geometries, and orientations. The criterion to be maximized is the SIMO outage capacity, a quantity based on the statistical distribution of the SIMO Shannon capacity estimated for a large number of ionospheric channel realizations, each of them being quantified by its channel impulse response including the receive antenna directional responses. Results are presented in the context of a 1 × 2 SIMO structure: the identification of the two most effective antennas in a set of NA = 15 sensors indicates that the optimal structures involve two orthogonal horizontal dipoles or two vertical orthogonal loop antennas. In these conditions, the outage capacity reaches up to 2.23 bps/Hz, a value that significantly exceeds the performances of standard modems.
Seismotectonics of northeastern Sicily and southern Calabria (Italy): New constraints on the tectonic structures featuring in a crucial sector for the central Mediterranean geodynamics
Authors: Scarfì L. , Barberi G. , Musumeci C. , Patanè D. 
Published: March 2016

AbstractThe purpose of this study is to gain a better understanding on the tectonic structures featuring in a crucial sector of central Mediterranean area, including the Aeolian Islands, southern Calabria, and northeastern Sicily, where the convergence between Eurasian and African Plates has given rise to a complicated collisional/subduction complex. A high‐quality data set of about 3000 earthquakes has been exploited for local earthquake tomography and focal mechanisms computation together with available source mechanisms from published catalogues. The results depict new details of a network of faults which enables the concurrent existence of adjacent compressional and extensional domains. In particular, tomographic images, seismic events distribution, and focal mechanisms pinpoint the geometry and activity of a lithospheric‐scale tear faults system which, with a NW‐SE trend through Sicily and the Tyrrhenian and Ionian Seas, represents the southern edge of the Ionian subduction trench zone. At crustal depth, this tearing is well highlighted by a rotation of the maximum horizontal stress, moving across the area from west toward east. In addition, the shallow normal fault regime, characterizing the southern Calabria and northeastern Sicily mainland, south of the NW‐SE lineament, changes in the deeper part of the crust. Indeed, a NE‐SW earthquake distribution, gently dipping NW, and inverse fault solutions indicate a still active contractional deformation in eastern Sicily, caused by the Africa‐Eurasia convergence and well framed with the current compressive regime along the southern Tyrrhenian zone and at the front of the Sicilian Chain‐Foreland.
Timing of deformation in the Sarandí del Yí Shear Zone, Uruguay: Implications for the amalgamation of western Gondwana during the Neoproterozoic Brasiliano‐Pan‐African Orogeny
Authors: Oriolo Sebastián , Oyhantçabal Pedro , Wemmer Klaus , Basei Miguel A. S. , Benowitz Jeffrey , Pfänder Jörg , Hannich Felix , Siegesmund Siegfried 
Published: March 2016

AbstractU‐Pb and Hf zircon (sensitive high‐resolution ion microprobe ‐SHRIMP‐ and laser ablation‐inductively coupled plasma‐mass spectrometry ‐LA‐ICP‐MS‐), Ar/Ar hornblende and muscovite, and Rb‐Sr whole rock‐muscovite isochron data from the mylonites of the Sarandí del Yí Shear Zone, Uruguay, were obtained in order to assess the tectonothermal evolution of this crustal‐scale structure. Integration of these results with available kinematic, structural, and microstructural data of the shear zone as well as with geochronological data from the adjacent blocks allowed to constrain the onset of deformation along the shear zone at 630–625 Ma during the collision of the Nico Pérez Terrane and the Río de la Plata Craton. The shear zone underwent dextral shearing up to 596 Ma under upper to middle amphibolite facies conditions, which was succeeded by sinistral shearing under lower amphibolite to upper greenschist facies conditions until at least 584 Ma. After emplacement of the Cerro Caperuza granite at 570 Ma, the shear zone underwent only cataclastic deformation between the late Ediacaran and the Cambrian. The Sarandí del Yí Shear Zone is thus related to the syncollisional to postcollisional evolution of the amalgamation of the Río de la Plata Craton and the Nico Pérez Terrane. Furthermore, the obtained data reveal that strain partitioning and localization with time, magmatism emplacement, and fluid circulation are key processes affecting the isotopic systems in mylonitic belts, revealing the complexity in assessing the age of deformation of long‐lived shear zones.
Late Neogene tectonically driven crustal exhumation of the Sikkim Himalaya: Insights from inversion of multithermochronologic data
Authors: Landry Kyle R. , Coutand Isabelle , Whipp David M. , Grujic Djordje , Hourigan Jeremy K. 
Published: March 2016

AbstractApatite fission track and zircon (U‐Th)/He data are reported for 34 bedrock samples distributed between the foothills and the topographic crest of the Darjeeling‐Sikkim Himalaya. The pattern of observed cooling ages does not correlate with topography, rainfall distribution, and the deeply incised high‐relief Tista window, indicating that tectonic processes are mainly responsible for their spatial distribution. Inversion of this thermochronometric data set using 3‐D thermokinematic modeling constrained by independent geological and geophysical observations was performed to evaluate the contribution of slip partitioning, duplex development, and relief growth on the evolution of the thermal structure of the Himalaya during the last 12 Ma. Models involving significant relief growth do not show a substantial influence of topography evolution on the cooling age distribution, while models involving duplex growth demonstrate that tectonic processes exert a dominant influence on their distribution. In concert with equivalent studies in Bhutan, central Nepal, and NW India, our results attest that the lateral variation of the geometry and kinematics of the Himalayan basal décollement locally associated with duplex formation exert a leading influence on lateral variations of middle to upper crustal long‐term exhumation rates documented along the strike of the Himalaya.
Ice mass loss in Greenland, the Gulf of Alaska, and the Canadian Archipelago: Seasonal cycles and decadal trends
Authors: Harig Christopher , Simons Frederik J. 
Published: March 2016

AbstractOver the past several decades mountain glaciers and ice caps have been significant contributors to sea level rise. Here we estimate the ice mass changes in the Canadian Archipelago, the Gulf of Alaska, and Greenland since 2003 by analyzing time‐varying gravimetry data from the Gravity Recovery and Climate Experiment. Prior to 2013, interannual ice mass variability in the Gulf of Alaska and in regions around Greenland remains within the average estimated over the whole data span. Beginning in summer 2013, ice mass in regions around Greenland departs positively from its long‐term trend. Over Greenland this anomaly reached almost 500 Gt through the end of 2014. Overall, long‐term ice mass loss from Greenland and the Canadian Archipelago continues to accelerate, while losses around the Gulf of Alaska region continue but remain steady with no significant acceleration.
The atmospheric partial lifetime of carbon tetrachloride with respect to the global soil sink
Authors: Rhew Robert C. , Happell James D. 
Published: March 2016

AbstractThe magnitude of the terrestrial soil sink for atmospheric carbon tetrachloride (CCl4) remains poorly constrained, with the estimated uncertainty range of CCl4 partial lifetimes between ~110 and 910 years. Field observations are sparse, and there are uncertainties in extrapolating these results to the global scale. Here we add to the published CCl4 fluxes with additional field measurements, and we employ a land cover classification scheme based on Advanced Very High Resolution Radiometer measurements that align more closely with the measurement sites to reevaluate the global CCl4 soil sink. We calculate an updated partial lifetime of CCl4 with respect to the soil sink to be 375 (288–536) years, which is 50 to 90% longer than the most recently published best estimates of the soil sink partial lifetime (195 and 245 years). This translates into a longer overall atmospheric lifetime estimate, which is more consistent with the observed atmospheric concentration trend and interhemispheric gradient.
Comparing GOSAT observations of localized CO2 enhancements by large emitters with inventory‐based estimates
Authors: Janardanan Rajesh , Maksyutov Shamil , Oda Tomohiro , Saito Makoto , Kaiser Johannes W. , Ganshin Alexander , Stohl Andreas , Matsunaga Tsuneo , Yoshida Yukio , Yokota Tatsuya 
Published: March 2016

AbstractWe employed an atmospheric transport model to attribute column‐averaged CO2 mixing ratios (XCO2) observed by Greenhouse gases Observing SATellite (GOSAT) to emissions due to large sources such as megacities and power plants. XCO2 enhancements estimated from observations were compared to model simulations implemented at the spatial resolution of the satellite observation footprint (0.1° × 0.1°). We found that the simulated XCO2 enhancements agree with the observed over several continental regions across the globe, for example, for North America with an observation to simulation ratio of 1.05 ± 0.38 (p < 0.1), but with a larger ratio over East Asia (1.22 ± 0.32; p < 0.05). The obtained observation‐model discrepancy (22%) for East Asia is comparable to the uncertainties in Chinese emission inventories (~15%) suggested by recent reports. Our results suggest that by increasing the number of observations around emission sources, satellite instruments like GOSAT can provide a tool for detecting biases in reported emission inventories.
Mapping 3D fault geometry in earthquakes using high‐resolution topography: Examples from the 2010 El Mayor‐Cucapah (Mexico) and 2013 Balochistan (Pakistan) earthquakes
Authors: Zhou Yu , Walker Richard T. , Elliott John R. , Parsons Barry 
Published: March 2016

AbstractFault dips are usually measured from outcrops in the field or inferred through geodetic or seismological modeling. Here we apply the classic structural geology approach of calculating dip from a fault's 3‐D surface trace using recent, high‐resolution topography. A test study applied to the 2010 El Mayor‐Cucapah earthquake shows very good agreement between our results and those previously determined from field measurements. To obtain a reliable estimate, a fault segment ≥120 m long with a topographic variation ≥15 m is suggested. We then applied this method to the 2013 Balochistan earthquake, getting dips similar to previous estimates. Our dip estimates show a switch from north to south dipping at the southern end of the main trace, which appears to be a response to local extension within a stepover. We suggest that this previously unidentified geometrical complexity may act as the endpoint of earthquake ruptures for the southern end of the Hoshab fault.
The importance of ENSO phase during volcanic eruptions for detection and attribution
Authors: Lehner Flavio , Schurer Andrew P. , Hegerl Gabriele C. , Deser Clara , Frölicher Thomas L. 
Published: March 2016

AbstractComparisons of the observed global‐scale cooling following recent volcanic eruptions to that simulated by climate models from the Coupled Model Intercomparison Project 5 (CMIP5) indicate that the models overestimate the magnitude of the global temperature response to volcanic eruptions. Here we show that this overestimation can be explained as a sampling issue, arising because all large eruptions since 1951 coincided with El Niño events, which cause global‐scale warming that partially counteracts the volcanically induced cooling. By subsampling the CMIP5 models according to the observed El Niño–Southern Oscillation (ENSO) phase during each eruption, we find that the simulated global temperature response to volcanic forcing is consistent with observations. Volcanic eruptions pose a particular challenge for the detection and attribution methodology, as their surface impacts are short‐lived and hence can be confounded by ENSO. Our results imply that detection and attribution studies must carefully consider sampling biases due to internal climate variability.
Volcanic lightning and plume behavior reveal evolving hazards during the April 2015 eruption of Calbuco volcano, Chile
Authors: Van Eaton Alexa R. , Amigo Álvaro , Bertin Daniel , Mastin Larry G. , Giacosa Raúl E. , González Jerónimo , Valderrama Oscar , Fontijn Karen , Behnke Sonja A. 
Published: March 2016

AbstractSoon after the onset of an eruption, model forecasts of ash dispersal are used to mitigate the hazards to aircraft, infrastructure, and communities downwind. However, it is a significant challenge to constrain the model inputs during an evolving eruption. Here we demonstrate that volcanic lightning may be used in tandem with satellite detection to recognize and quantify changes in eruption style and intensity. Using the eruption of Calbuco volcano in southern Chile on 22 and 23 April 2015, we investigate rates of umbrella cloud expansion from satellite observations, occurrence of lightning, and mapped characteristics of the fall deposits. Our remote sensing analysis gives a total erupted volume that is within uncertainty of the mapped volume (0.56 ± 0.28 km3 bulk). Observations and volcanic plume modeling further suggest that electrical activity was enhanced both by ice formation in the ash clouds >10 km above sea level and development of a low‐level charge layer from ground‐hugging currents.
Enhanced ionospheric plasma bubble generation in more active ITCZ
Authors: Li Guozhu , Otsuka Yuichi , Ning Baiqi , Abdu M. A. , Yamamoto M. , Wan Weixing , Liu Libo , Abadi Prayitno 
Published: March 2016

AbstractA close link between the atmospheric Intertropical Convergence Zone (ITCZ) and ionospheric plasma bubble has been proposed since the last century. But this relationship has often appeared to be less than convincing due to the simultaneous roles played by several other factors in shaping the global distribution of ionospheric bubbles. From simultaneous collaborative radar multibeam steering measurements at Kototabang (0.2°S, 100.3°E) and Sanya (18.4°N, 109.6°E), conducted during September–October of 2012 and 2013, we find that the total numbers of nights with bubble (i.e., occurrence rates) at the two closely located longitudes (Kototabang and Sanya) are comparable. But interestingly, the total number of nights with locally generated bubble (i.e., generation rate) over Kototabang is clearly more than that over Sanya. Further analysis reveals that a more active ITCZ is situated around the longitude of Kototabang. We surmise that the enhanced ionospheric bubble generation at Kototabang longitude could be caused by a higher gravity wave activity associated with the more active ITCZ.
On the electron diffusion region in asymmetric reconnection with a guide magnetic field
Authors: Hesse Michael , Liu Yi‐Hsin , Chen Li‐Jen , Bessho Naoki , Kuznetsova Masha , Birn Joachim , Burch James L. 
Published: March 2016

AbstractParticle‐in‐cell simulations in a 2.5‐D geometry and analytical theory are employed to study the electron diffusion region in asymmetric reconnection with a guide magnetic field. The analysis presented here demonstrates that similar to the case without guide field, in‐plane flow stagnation and null of the in‐plane magnetic field are well separated. In addition, it is shown that the electric field at the local magnetic X point is again dominated by inertial effects, whereas it remains dominated by nongyrotropic pressure effects at the in‐plane flow stagnation point. A comparison between local electron Larmor radii and the magnetic gradient scale lengths predicts that distribution should become nongyrotropic in a region enveloping both field reversal and flow stagnation points. This prediction is verified by an analysis of modeled electron distributions, which show clear evidence of mixing in the critical region.