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  • Weitere Quellen  (19)
  • American Institute of Physics
  • American Geophysical Union (AGU)
  • Annual Reviews
  • 2005-2009  (10)
  • 1995-1999  (4)
  • 1990-1994  (3)
  • 1980-1984  (2)
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  • 1
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    A significant upper limit for the rate of formation, of OCS from the reaction of OH with CS2 (1980)
    American Geophysical Union (AGU)
    In:  Geophysical Research Letters, 7 (10). pp. 797-800.
    Details
    Publikationsdatum: 2020-07-30
    Beschreibung: The rate of reaction of OH with CS2 to form OCS by reaction (1) has been measured through observation of O14CS following 254 nm equation image photolysis of mixtures of H2O2 with 14CS2. The OH concentrations have been monitored through simultaneous measurement in the same cell of either (a) the oxidation of CO to CO2, or (b) the removal of a hydrocarbon such as C3H8 or iso-C4H10. The upper limit for the formation of OCS based on (a) corresponds to a rate constant k1 〈 0.3 × 10−14 cm³ molecule−1 sec−1. Other chemical reactions in the system have led to the formation of both 14CO and 14CO2, indicating the existence of a complex combination of reactions such that the observed O14CS need not have been formed by (1). The rate of reaction (1) is sufficiently slow that it is neither an important atmospheric sink for CS2 nor an important source for atmospheric OCS. The reaction of OH with OCS has not been measured in these experiments, but by analogy with k1 it is probably not an important atmospheric sink for OCS nor an important source of SO2.
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  • 2
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    Classification of heterogeneous seafloor topography through surface slope distributions (1991)
    American Institute of Physics
    In:  Journal of the Acoustical Society of America, 90 (4, Pt. 2). pp. 2255-2256.
    Details
    Publikationsdatum: 2020-07-16
    Beschreibung: Seafloor topography is neither spatially homogeneous, nor does it obey Gaussian statistics; deviations from both of these assumptions are important from a geological and acoustic point of view. It has been found that the distribution of topographic slopes can be used as a primary tool for understanding the sources and extent of spatial heterogeneities and patterns on the seafloor. The covariance function has been widely used to characterize seafloor topography, but requires the assumption of Gaussian joint probability statistics to be valid. For heterogeneous topography characterized by large transient signals such as steep scarps and volcanoes, the covariance becomes dominated by the transients; in contrast the family slope distributions can still be used to derive stable descriptors for regions with large transient signals, as well as regions containing asymmetric features, and regions with only limited sampling. Knowledge of slopes is useful because a direct relation exists between the covariance and the slope distributions at different spatial scales. Studies of the slope distribution provide a means of identifying the presence of the non‐Gaussian elements in the topography, and flagging their spatial locations. The methods used here are demonstrated by applying them to three small patches of topography located within 20 km of each other in the Eastern Pacific. It is found that dominant azimuthal directions and dip angles differ widely between the patches. In addition, asymmetries in the cross‐sectional shapes of faulted abyssal hills are documented. [Work supported by ONR.]
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  • 3
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    High‐frequency bottom backscattering: Roughness versus sediment volume scattering (1992)
    American Institute of Physics
    In:  Journal of the Acoustical Society of America, 92 (2). pp. 962-977.
    Details
    Publikationsdatum: 2020-07-16
    Beschreibung: High‐frequency bottom acoustic and geoacoustic data from three well‐characterized sites of different bottom composition are compared with scattering models in order to clarify the roles played by interface roughness and sediment volume inhomogeneities. Model fits to backscattering data from two silty sites lead to the conclusion that scattering from volume inhomogeneities was primarily responsible for the observed backscattering. In contrast, measured bottom roughness was sufficient to explain the backscattering seen at a sandy site. Although the sandy site had directional ripples, the model and data agree in their lack of anisotropy.
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  • 4
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    Seismic characterization and continuity analysis of gas-hydrate horizons near Mallik research wells, Mackenzie Delta, Canada (2006)
    American Institute of Physics
    In:  The Leading Edge, 25 (5). pp. 599-604.
    Details
    Publikationsdatum: 2015-11-25
    Beschreibung: Gas-hydrate accumulations located onshore in Arctic permafrost regions are seen as a potential source of natural gas. Surprisingly, most of the gas hydrate found in the Mackenzie Delta and Beaufort Sea areas was indirectly discovered or inferred from conventional hydrocarbon exploration programs. One of these occurrences, the Mallik gas-hydrate field (Figure 1), has received particular attention over the last 10 years. Two internationally partnered research well programs have intersected three intervals of gas hydrates and have allowed successful extraction of subpermafrost core samples with significant gas hydrates. The gas-hydrate intervals are up to 40 m thick and have high gas-hydrate saturation, sometimes exceeding 80% of pore volume of unconsolidated clastic sediments with average porosities from 25–40%. At Mallik, the gas-hydrate intervals are located at depths of 900–1100 m and are localized on the crest of an anticline.
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  • 5
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    Noise reduction in 2D and 3D seismic imaging by the CRS method (2008)
    American Institute of Physics
    In:  The Leading Edge, 27 (2). pp. 258-265.
    Details
    Publikationsdatum: 2015-12-16
    Beschreibung: The definition of noise and signal in seismic data will vary widely with the viewer's perspective and methods to process and visualize the data. Thus we begin with our definition from the perspective of presenting structural subsurface information.
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  • 6
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    Geo- and hydro-acoustic manifestations of shallow gas and gas seeps in the Dnepr paleodelta, northwestern Black Sea (2009)
    American Institute of Physics
    In:  The Leading Edge, 28 (9). pp. 1030-1040.
    Details
    Publikationsdatum: 2016-05-24
    Beschreibung: Shallow gas occurs between 0 and 1000 m below the sea floor. It consists mainly of microbial-formed or thermogenic methane or a combination of both, sometimes with a limited admixture of higher hydrocarbons (propane, butane, etc.).
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  • 7
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    A new equation for the accurate calculation of sound speed in all oceans (2008)
    American Institute of Physics
    In:  Journal of the Acoustical Society of America, 124 (5). pp. 2774-2782.
    Details
    Publikationsdatum: 2020-07-16
    Beschreibung: A new equation is proposed for the calculation of sound speed in seawater as a function of temperature, salinity, depth, and latitude in all oceans and open seas, including the Baltic and the Black Sea. The proposed equation agrees to better than ±0.2m∕s with two reference complex equations, each fitting the best available data corresponding to existing waters of different salinities. The only exceptions are isolated hot brine spots that may be found at the bottom of some seas. The equation is of polynomial form, with 14 terms and coefficients of between one and three significant figures. This is a substantial reduction in complexity compared to the more complex equations using pressure that need to be calculated according to depth and location. The equation uses the 1990 universal temperature scale (an elementary transformation is given for data based on the 1968 temperature scale). It is hoped that the equation will be useful to those who need to calculate sound speed in applications of marine acoustics.
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  • 8
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    Dependence of multiple-attenuation techniques on the geological setting: A case study from offshore Taiwan (1999)
    American Institute of Physics
    In:  The Leading Edge, 18 (1). pp. 74-80.
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    Publikationsdatum: 2018-01-18
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  • 9
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    DMS air/sea flux and gas transfer coefficients from the North Atlantic summertime coccolithophore bloom (2008)
    American Geophysical Union (AGU)
    In:  Geophysical Research Letters, 35 (L23812).
    Details
    Publikationsdatum: 2020-07-30
    Beschreibung: Dimethylsulfide (DMS) atmospheric and oceanic concentrations and eddy covariance air/sea fluxes were measured over the N. Atlantic Ocean during July 2007 from Iceland to Woods Hole, MA, USA. Seawater DMS levels north of 55 degrees N ranged from 3 to 17 nM, with variability related to the satellite-derived distributions of coccoliths and to a lesser extent, chlorophyll. For the most intense bloom region southwest of Iceland, DMS air/sea fluxes were as high as 300 mu mol m(-2) d(-1), larger than current model estimates. The observations imply that gas exchange coefficients in this region are significantly greater than those estimated using most gas transfer parameterizations. South of 55 degrees N, DMS levels were lower and the gas transfer coefficients were similar to those observed in other regions of the ocean. The data suggest that DMS emissions from the bloom region may be significantly larger than current estimates. The anomalous gas exchange coefficients likely reflect strong near-surface, water column DMS gradients influenced by physical and biological processes
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  • 10
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    3-D seismic discontinuity for faults and stratigraphic features: The coherence cube (1995)
    American Institute of Physics
    In:  The Leading Edge, 14 (10). pp. 1053-1058.
    Details
    Publikationsdatum: 2016-07-26
    Beschreibung: Seismic data are usually acquired and processed for imaging reflections. This paper describes a method of processing seismic data for imaging discontinuities (e.g., faults and stratigraphic features). One application of this nontraditional process is a 3-D volume, or cube, of coherence coefficients within which faults are revealed as numerically separated surfaces. Figure 1 compares a traditional 3-D reflection amplitude time slice with the results of the new method. To our knowledge, this is the first published method of revealing fault surfaces within a 3-D volume for which no fault reflections have been recorded.
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  • 11
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    Depth-pressure relationships in the oceans and seas (1998)
    American Institute of Physics
    In:  Journal of the Acoustical Society of America, 103 (3). pp. 1346-1352.
    Details
    Publikationsdatum: 2020-07-16
    Beschreibung: Two sets of equations, covering all world oceans and seas, are presented to calculate pressure from depth for the computation of sound speed, and depth from pressure for use in ocean engineering. They are based on the algorithm of UNESCO 1983 [N. P. Fofonoff and R. C. Millard, Jr., Unesco Tech. Papers in Mar. Sci. No. 44 (1983)], and on calculations from temperature and salinity profiles. The pressure to depth conversion is presented first. The equations can be used in those cases where the desired accuracy is reduced to ±0.8 m. The equations to convert depth to pressure provide an overall accuracy between ±8000 Pa and ±1000 Pa. This leads to errors in sound speed consistently smaller than ±0.02 m/s. The discussion, and comparisons with results and other formulas, suggest that the new equations are a substantial improvement on the previous simplified ones, which should now be abandoned.
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  • 12
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    Seismic attributes and their classification (1996)
    American Institute of Physics
    In:  The Leading Edge, 15 (10). p. 1090.
    Details
    Publikationsdatum: 2016-08-30
    Beschreibung: Attributes have proliferated recently with different selections available on different workstations. What do they all mean? When do we use one and when another? The answers to these questions are not easy but the first step is to understand what our options are, and herein lies the purpose of this article.
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  • 13
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    Dynamics of Coupled Ocean-Atmosphere Models: The Tropical Problem (1994)
    Annual Reviews
    In:  Annual Review of Fluid Mechanics, 26 (1). pp. 617-659.
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    Publikationsdatum: 2020-06-09
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  • 14
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    Distribution of dissolved organic nutrients and their effect on export production over the Atlantic Ocean (2009)
    American Geophysical Union (AGU)
    In:  Global Biogeochemical Cycles, 23 (4).
    Details
    Publikationsdatum: 2020-07-30
    Beschreibung: A synthesis is provided of dissolved organic nitrogen (DON) and phosphorus (DOP) distributions over the Atlantic Ocean based upon field data from eight recent transects, six meridional between 50°N and 50°S and two zonal at 24° and 36°N. Over the entire tropical and subtropical Atlantic, DON and DOP provide the dominant contributions to total nitrogen and phosphorus pools for surface waters above the thermocline. Elevated DON and DOP concentrations (〉5 and 〉0.2 μ mol L−1, respectively) occur in surface waters on the eastern side of the North Atlantic subtropical gyre and equatorial sides of both the North and South Atlantic subtropical gyres, while particularly low concentrations of DOP (〈0.05 μ mol L−1) occur over the northern flank of the North Atlantic subtropical gyre along 36°N. This distribution is consistent with organic nutrients formed at the gyre margins supporting carbon export as they are redistributed via the gyre circulation. The effect of DON and DOP transport and cycling on export production is examined in an eddy‐permitting, coupled physical and nutrient model integrated for 40 years: organic nutrients are produced in the upwelling zones off North Africa and transferred laterally into the gyre interior, facilitated in part by the mesoscale eddy circulation, as well as fluxed northward from the tropics as part of the overturning circulation. Inputs of semilabile DON and DOP to the tropical and subtropical Atlantic Ocean play an important role in sustaining up to typically 40 and 70% of the modeled particulate N and P export, particularly on the eastern and equatorward sides of the subtropical gyres.
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  • 15
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    Fracture properties from seismic scattering (2007)
    American Institute of Physics
    In:  The Leading Edge, 26 (9). pp. 1186-1196.
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    Publikationsdatum: 2019-04-29
    Beschreibung: The seismic trace is a complex aggregate of reflected and scattered signals from subsurface formation interfaces and heterogeneities. Although many varieties of random noise may also be present in the trace, we know from reacquiring the same seismic survey that seismic data are highly repeatable, indicating that significant information about the subsurface is contained in the trace but not yet used by our standard analysis methods. Seismic scattering is a type of signal contained in the data that is generally not utilized.
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  • 16
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    Mass balance of the Greenland ice sheet from 1958 to 2007 (2008)
    American Geophysical Union (AGU)
    In:  Geophysical Research Letters, 35 (20). L20502.
    Details
    Publikationsdatum: 2020-07-30
    Beschreibung: We combine estimates of the surface mass balance, SMB, of the Greenland ice sheet for years 1958 to 2007 with measurements of the temporal variability in ice discharge, D, to deduce the total ice sheet mass balance. During that time period, we find a robust correlation (R2 = 0.83) between anomalies in SMB and in D, which we use to reconstruct a continuous series of total ice sheet mass balance. We find that the ice sheet was losing 110 ± 70 Gt/yr in the 1960s, 30 ± 50 Gt/yr or near balance in the 1970s–1980s, and 97 ± 47 Gt/yr in 1996 increasing rapidly to 267 ± 38 Gt/yr in 2007. Multi‐year variations in ice discharge, themselves related to variations in SMB, cause 60 ± 20% more variation in total mass balance than SMB, and therefore dominate the ice sheet mass budget.
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  • 17
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    Seafloor reflectivity—An important seismic property for interpreting fluid/gas expulsion geology and the presence of gas hydrate (2006)
    American Institute of Physics
    In:  The Leading Edge, 25 (5). pp. 620-628.
    Details
    Publikationsdatum: 2020-01-20
    Beschreibung: A bottom-simulating reflection (BSR) is a seismic reflectivity phenomenon that is widely accepted as indicating the base of the gas-hydrate stability zone. The acoustic impedance difference between sediments invaded with gas hydrate above the BSR and sediments without gas hydrate, but commonly with free gas below, are accepted as the conditions that create this reflection. The relationship between BSRs and marine gas hydrate has become so well known since the 1970s that investigators, when asked to define the most important seismic attribute of marine gas-hydrate systems, usually reply, “a BSR event.” Research conducted over the last decade has focused on calibrating seafloor seismic reflectivity across the geology of the northern Gulf of Mexico (GoM) continental slope surface to the seafloor. This research indicates that the presence and character of seafloor bright spots (SBS) can be indicators of gas hydrates in surface and near-surface sediments (Figure 1). It has become apparent that SBSs on the continental slope generally are responses to fluid and gas expulsion processes. Gas-hydrate formation is, in turn, related to these processes. As gas-hydrate research expands around the world, it will be interesting to find if SBS behavior in other deepwater settings is as useful for identifying gas-hydrate sites as in the GoM.
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  • 18
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    Optimum frequencies for noise‐limited active sonar detection (1981)
    American Institute of Physics
    In:  The Journal of the Acoustical Society of America, 70 (5). pp. 1336-1338.
    Details
    Publikationsdatum: 2020-05-11
    Beschreibung: The curves of optimum frequencies versus maximum range for active sonar detection under specific sets of assumptions are presented for the more recent expressions for attenuation given by Lovett [J. Acoust. Soc. Am. 58, 620–625 (1975)] for the eastern North Pacific and Thorp [J. Acoust. Soc. Am. 42, 270 (1967)] for the western North Atlantic as corrected at low frequencies by Kibblewhite et al. [J. Acoust. Soc. Am. 60, 1040–1047 (1976)].
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  • 19
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    Air-sea gas exchange of CO2 and DMS in the North Atlantic by eddy covariance (2009)
    American Geophysical Union (AGU)
    In:  Geophysical Research Letters, 36 . L15816.
    Details
    Publikationsdatum: 2020-07-30
    Beschreibung: We report the first simultaneous eddy covariance flux measurements of CO2 and dimethylsulfide (DMS) over the open ocean for two North Atlantic cruises. After normalization for Schmidt number, the two gases give essentially identical gas transfer coefficients and wind speed dependences for the wind speed range 2–10 ms−1. The data indicate a linear relationship between the gas transfer coefficient and mean wind speed, with measured gas transfer coefficients slightly above the Wanninkhof (1992) parameterization, particularly at low wind speeds.
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