Methane Fluxes from a High Intensity Seep Area west of Crimea, Black Sea

Methane seepage is a wide-spread phenomenon in the Black Sea with an increase in density and intensity west of the Crimea in the Paleo Dnepr area between 70 and 250m water depth. Within the EU funded project CRIMEA we studied the impact of high intensity seeps on the methane distribution in the water column and its possible transport into the atmosphere. Here we present data which allow flux calculations of free methane from an area of 1 by 1.23 miles between 80 and 95m water depth. Our calculations are based on direct and hydroacoustic flux measurements of single seeps or small-scaled seep areas (several m2); the spatial extrapolation of these fluxes use the very strong correlation between the bubble seep occurrence and a high backscattering seafloor; the temporal variability of bubble release was detected via the lander-based hydroacoustic system GasQuant.More than 1000 bubbling seep sites were identified during two cruises in 2003 and 2004 by hydroacoustic water column surveys. The hydroacoustic detection of bubbles uses the strong backscattering of the free gas phase caused by the great impedance difference of bubbles in water (equivalent to the detection of fish and their swim bladder). In echograms, bubble streams or even single bubbles can be detected, traced and used for special analyses such as bubble rising speed, bubble size and shrinking rates. Because of the flare-like appearance of bubble streams in echograms we call these features ’flares’.Parallel multi beam mapping allowed the detection of the seafloor morphology together with the spatial backscatter intensity of the seafloor. The combination of flare occurrences with high backscatter areas provided a very good correlation. Normalized, the backscatter ranged from -12.5 to 7.1 dB for an area of 4.23 km2. All seep positions plott in areas with more than -2.7 dB, which is almost the entire area of investigation (95.8 %). However, 75% of the flares occur within only 20.1% of the area, half of the flares occur in only 9.2% and 25% even occur in only 3.8% of the area with backscattering values above 2.4 dB. This correlation allows to predict and extrapolate active bubble seeps even without direct or hydroacoustic observations.One reason for the high backscattering seafloor are patches of carbonate cemented seafloor (formed via AOM) which typically occurs just below bright white Beggiatoa mats. In addition, high resolution seismic studies with a 5kHz sub-bottom profiler clearly show a shallow gas front in normally 3m sediment depth. In those areas where strong gas front reflectors dome up and reach the seafloor surface the backscatter values and flare density are the highest. This clearly shows that the bubbles released are fed from shallow gas which also might have an impact on the physical properties of the seafloor and its backscatter behaviour. Seeps in lower or even very low backscatter areas possibly indicate a rather young or weak activity which did not (so far) cause a remarkable carbonate cementation detectable during multi beam surveys.However, the backscatter data are the base for our spatial flux calculations which use direct bubble trapping to distinguish the flux rate from one single seep hole and hydroacoustic methods for small seep areas of several m2. Direct bubble flux measurements were performed with the submersible JAGO by trapping the bubbles with a funnel. Fluxes vary between 0.55 and 1.44 ml/s (or 1.98 to 5.18 l/h at in situ volume; or 0.24 to 0.64 mmol/s). Subsequent GC-based gas analyses onboard confirmed that the gas phase consists exclusively of methane. Visual observations by JAGO and towed camera systems showed bubble diameters between 1 and 15mm with typical sizes between 3 and 7mm. Together with bubble rising speeds of typically 25cm/s both attributes are in very good agreement with detailed hydroacoustic measurements using a dual frequency scientific echo sounder EK500 (120 and 38kHz). Flux estimat

Preliminary Experiments and Modelling of the Fate of CO2 Bubbles in the Water Column Near Panarea Island (Italy)

Although CO2 capture and storage in deep, offshore reservoirs is a proven technology, as illustrated by over 15 years of operation of the Sleipner site in the Norwegian North Sea, potential leakage from such sites into the overlying water column remains a concern for some stakeholders. Therefore, we are obliged to carefully assess our ability to predict and monitor the migration, fate, and potential ecosystem impact of any leaked CO2. The release of bubbles from the sea floor, their upward movement, and their dissolution into the surrounding water controls the initial boundary conditions, and thus an understanding of the behavior of CO2 bubbles is critical to address such issues related to monitoring and risk assessment. The present study describes results from an in situ experiment conducted in 12 m deep marine water near the extinct volcanic island of Panarea (Italy). Bubbles of a controlled size were created using natural CO2 released from the sea floor, and their evolution during ascent in the water column was monitored via both video and chemical measurements. The obtained results were modelled and a good fit was obtained, showing the potential of the model as a predictive tool. These preliminary results and an assessment of the difficulties encountered are examined and will be used to improve experimental design for the subsequent phase of this research

QuShape: Rapid, accurate, and best-practices quantification of nucleic acid probing information, resolved by capillary electrophoresis

Chemical probing of RNA and DNA structure is a widely used and highly informative approach for examining nucleic acid structure and for evaluating interactions with protein and small-molecule ligands. Use of capillary electrophoresis to analyze chemical probing experiments yields hundreds of nucleotides of information per experiment and can be performed on automated instruments. Extraction of the information from capillary electrophoresis electropherograms is a computationally intensive multistep analytical process, and no current software provides rapid, automated, and accurate data analysis. To overcome this bottleneck, we developed a platform-independent, user-friendly software package, QuShape, that yields quantitatively accurate nucleotide reactivity information with minimal user supervision. QuShape incorporates newly developed algorithms for signal decay correction, alignment of time-varying signals within and across capillaries and relative to the RNA nucleotide sequence, and signal scaling across channels or experiments. An analysis-by-reference option enables multiple, related experiments to be fully analyzed in minutes. We illustrate the usefulness and robustness of QuShape by analysis of RNA SHAPE (selective 2′-hydroxyl acylation analyzed by primer extension) experiments

Oxygen fluxes beneath Arctic land-fast ice and pack ice: towards estimates of ice productivity

Sea-ice ecosystems are among the most extensive of Earth's habitats; yet its autotrophic and heterotrophic activities remain poorly constrained. We employed the in situ aquatic eddy-covariance (AEC) O-2 flux method and laboratory incubation techniques ((HCO3-)-C-14, [H-3] thymidine and [H-3] leucine) to assess productivity in Arctic sea-ice using different methods, in conditions ranging from land-fast ice during winter, to pack ice within the central Arctic Ocean during summer. Laboratory tracer measurements resolved rates of bacterial C demand of 0.003-0.166mmolCm(-2)day(-1) and primary productivity rates of 0.008-0.125mmolCm(-2)day(-1) for the different ice floes. Pack ice in the central Arctic Ocean was overall net autotrophic (0.002-0.063mmolCm(-2)day(-1)), whereas winter land-fast ice was net heterotrophic (-0.155mmol C m(-2) day(-1)). AEC measurements resolved an uptake of O-2 by the bottom-ice environment, from similar to-2mmolO(2)m(-2) day(-1) under winter land-fast ice to similar to-6mmolO(2)m(-2)day(-1) under summer pack ice. Flux of O-2-deplete meltwater and changes in water flow velocity masked potential biological-mediated activity. AEC estimates of primary productivity were only possible at one study location. Here, productivity rates of 1.3 +/- 0.9mmolO(2)m(-2)day(-1), much larger than concurrent laboratory tracer estimates (0.03mmolCm(-2)day(-1)), indicate that ice algal production and its importance within the marine Arctic could be underestimated using traditional approaches. Given careful flux interpretation and with further development, the AEC technique represents a promising new tool for assessing oxygen dynamics and sea-ice productivity in ice-covered regions.Peer reviewe

CSI 2264: Accretion process in classical T Tauri stars in the young cluster NGC 2264

Context. NGC 2264 is a young stellar cluster (~3 Myr) with hundreds of low-mass accreting stars that allow a detailed analysis of the accretion process taking place in the pre-main sequence. Aims. Our goal is to relate the photometric and spectroscopic variability of classical T Tauri stars to the physical processes acting in the stellar and circumstellar environment, within a few stellar radii from the star. Methods. NGC 2264 was the target of a multiwavelength observational campaign with CoRoT, MOST, Spitzer, and Chandra satellites and photometric and spectroscopic observations from the ground. We classified the CoRoT light curves of accreting systems according to their morphology and compared our classification to several accretion diagnostics and disk parameters. Results. The morphology of the CoRoT light curve reflects the evolution of the accretion process and of the inner disk region. Accretion burst stars present high mass-accretion rates and optically thick inner disks. AA Tau-like systems, whose light curves are dominated by circumstellar dust obscuration, show intermediate mass-accretion rates and are located in the transition of thick to anemic disks. Classical T Tauri stars with spot-like light curves correspond mostly to systems with a low mass-accretion rate and low mid-IR excess. About 30% of the classical T Tauri stars observed in the 2008 and 2011 CoRoT runs changed their light-curve morphology. Transitions from AA Tau-like and spot-like to aperiodic light curves and vice versa were common. The analysis of the Hα emission line variability of 58 accreting stars showed that 8 presented a periodicity that in a few cases was coincident with the photometric period. The blue and red wings of the Hα line profiles often do not correlate with each other, indicating that they are strongly influenced by different physical processes. Classical T Tauri stars have a dynamic stellar and circumstellar environment that can be explained by magnetospheric accretion and outflow models, including variations from stable to unstable accretion regimes on timescales of a few years

CSI 2264 : accretion process in classical T Tauri stars in the young cluster NGC 2264

APS and SHPA acknowledge support from CNPq, CAPES and Fapemig. JFG acknowledges support from FCT ref project UID/FIS/04434/2013.Context. NGC 2264 is a young stellar cluster (~3 Myr) with hundreds of low-mass accreting stars that allow a detailed analysis of the accretion process taking place in the pre-main sequence. Aims. Our goal is to relate the photometric and spectroscopic variability of classical T Tauri stars to the physical processes acting in the stellar and circumstellar environment, within a few stellar radii from the star. Methods. NGC 2264 was the target of a multiwavelength observational campaign with CoRoT, MOST, Spitzer, and Chandra satellites and photometric and spectroscopic observations from the ground. We classified the CoRoT light curves of accreting systems according to their morphology and compared our classification to several accretion diagnostics and disk parameters. Results. The morphology of the CoRoT light curve reflects the evolution of the accretion process and of the inner disk region. Accretion burst stars present high mass-accretion rates and optically thick inner disks. AA Tau-like systems, whose light curves are dominated by circumstellar dust obscuration, show intermediate mass-accretion rates and are located in the transition of thick to anemic disks. Classical T Tauri stars with spot-like light curves correspond mostly to systems with a low mass-accretion rate and low mid-IR excess. About 30% of the classical T Tauri stars observed inthe 2008 and 2011 CoRoT runs changed their light-curve morphology.Transitions from AA Tau-like and spot-like to a periodic light curves and vice versa were common. The analysis of the Hα emission line variability of 58 accreting stars showed that 8 presented a periodicity that in a few cases was coincident with the photometric period. The blue and red wings of the Hα line profiles often do not correlate with each other, indicating that they are strongly influenced by different physical processes. Classical T Tauri stars have a dynamic stellar and circumstellar environment that can be explained by magnetospheric accretion and outflow models, including variations from stable to unstable accretion regimes on timescales of a few years.PostprintPeer reviewe

CSI 2264: Probing the inner disks of AA Tauri-like systems in NGC 2264

Context. The classical T Tauri star (CTTS) AA Tau has presented photometric variability that was attributed to an inner disk warp, caused by the interaction between the inner disk and an inclined magnetosphere. Previous studies of the young cluster NGC 2264 have shown that similar photometric behavior is common among CTTS. Aims. The goal of this work is to investigate the main causes of the observed photometric variability of CTTS in NGC 2264 that present AA Tau-like light curves, and verify if an inner disk warp could be responsible for their observed variability. Methods. In order to understand the mechanism causing these stars’ photometric behavior, we investigate veiling variability in their spectra and u − r color variations and estimate parameters of the inner disk warp using an occultation model proposed for AA Tau. We also compare infrared Spitzer IRAC and optical CoRoT light curves to analyze the dust responsible for the occultations. Results. AA Tau-like variability proved to be transient on a timescale of a few years. We ascribe this variability to stable accretion regimes and aperiodic variability to unstable accretion regimes and show that a transition, and even coexistence, between the two is common. We find evidence of hot spots associated with occultations, indicating that the occulting structures could be located at the base of accretion columns. We find average values of warp maximum height of 0.23 times its radial location, consistent with AA Tau, with variations of on average 11% between rotation cycles. We also show that extinction laws in the inner disk indicate the presence of grains larger than interstellar grains. Conclusions. The inner disk warp scenario is consistent with observations for all but one star with AA Tau-like variability in our sample. AA Tau-like systems are fairly common, comprising 14% of CTTS observed in NGC 2264, though this number increases to 35% among systems of mass 0.7 M_⊙ ≲ M ≲ 2.0 M_⊙. Assuming random inclinations, we estimate that nearly all systems in this mass range likely possess an inner disk warp. We attribute this to a possible change in magnetic field configurations among stars of lower mass

A Very Intense Neutrino Super Beam Experiment for Leptonic CP Violation Discovery based on the European Spallation Source Linac: A Snowmass 2013 White Paper

Very intense neutrino beams and large neutrino detectors will be needed in order to enable the discovery of CP violation in the leptonic sector. We propose to use the proton linac of the European Spallation Source currently under construction in Lund, Sweden to deliver, in parallel with the spallation neutron production, a very intense, cost effective and high performance neutrino beam. The baseline program for the European Spallation Source linac is that it will be fully operational at 5 MW average power by 2022, producing 2 GeV 2.86 ms long proton pulses at a rate of 14 Hz. Our proposal is to upgrade the linac to 10 MW average power and 28 Hz, producing 14 pulses/s for neutron production and 14 pulses/s for neutrino production. Furthermore, because of the high current required in the pulsed neutrino horn, the length of the pulses used for neutrino production needs to be compressed to a few $\mu$s with the aid of an accumulator ring. A long baseline experiment using this Super Beam and a megaton underground Water Cherenkov detector located in existing mines 300-600 km from Lund will make it possible to discover leptonic CP violation at 5 $\sigma$ significance level in up to 50% of the leptonic Dirac CP-violating phase range. This experiment could also determine the neutrino mass hierarchy at a significance level of more than 3 $\sigma$ if this issue will not already have been settled by other experiments by then. The mass hierarchy performance could be increased by combining the neutrino beam results with those obtained from atmospheric neutrinos detected by the same large volume detector. This detector will also be used to measure the proton lifetime, detect cosmological neutrinos and neutrinos from supernova explosions. Results on the sensitivity to leptonic CP violation and the neutrino mass hierarchy are presented.Comment: 28 page

Environmental Geophysics at Kings Creek Disposal Site and 30th Street Landfill, Aberdeen Proving Ground, Maryland

Geophysical studies on the Bush River Peninsula in the Edgewood Area of Aberdeen Proving Ground, Maryland, delineate landfill areas and provide diagnostic signatures of the hydrogeologic framework and possible contaminant pathways. These studies indicate that, during the Pleistocene Epoch, alternating stands of high and low seal levels resulted in a complex pattern of shallow channel-fill deposits in the Kings Creek area. Ground-penetrating radar studies reveal a paleochannel greater than 50 ft deep, with a thalweg trending offshore in a southwest direction into Kings Creek. Onshore, the ground-penetrating radar data indicate a 35-ft-deep branch to the main channel, trending to the north-northwest directly beneath the 30th Street Landfill. Other branches are suspected to meet the offshore paleochannel in the wetlands south and east of the 30th Street Landfill. This paleochannel depositional system is environmentally significant because it may control the shallow groundwater flow regime beneath the site. Electromagnetic surveys have delineated the pre-fill lowland area currently occupied by the 30th Street Landfill. Magnetic and conductive anomalies outline surficial and buried debris throughout the study area. On the basis of geophysical data, large-scale dumping has not occurred north of the Kings Creek Disposal Site or east of the 30th Street Landfill