bluuebunny/crossref_metadata_2025 huggingface dataset:
Water column hydrothermal plumes on the Juan de Fuca Ridge
Authors: Lupton John E.
Published: February 2008

Hydrographic surveys on the Juan de Fuca Ridge (JdFR) carried out from 1980 to 1987 show a complex pattern of 3He and Mn‐rich water column plumes produced by venting from several submarine hot spring areas. In the vicinity of Axial Volcano at latitude 46°N, distinct plumes were detected in 1980, 1982, and 1983 with3He signatures up to δ(3He) = 64% at ∼1500‐m depth at distances of ∼10 km from the seamount summit. However, the same plumes had no detectable thermal signature, a paradox which is attributed to the high 3He/heat ratios and low salinities of the fluids venting within the caldera of Axial Volcano. Profiles directly over the seamount show hydrothermal 3He in the water column up to 300 m above the caldera floor, with the 3He signal increasing with depth to very high and uniform ratios of δ(3He) = 108–150% below the ∼1500‐m caldera sill depth. Another apparent locus of hydrothermal input is Helium Basin, a depression on the northeast flank of Axial Volcano which had δ(3He) = 51% when first sampled in 1980. However, subsequent hydrocasts into Helium Basin in 1982 and 1983 yielded lower helium enrichments, suggesting either a decrease in hydrothermal input or flushing of the basin via a mixing event. To the south of Axial Volcano, high δ(3He) values of ∼40% observed over the ridge axis at 45°18′N and 45°39′N indicate venting on this previously unexplored section of the ridge. The water column plumes over the U. S. Geological Survey vent site at ∼44°40′N on the southern JdFR have very high Mn/3He ratios of 4600 mol/cm3, an apparently unique characteristic which can be used to distinguish these plumes from those originating at other JdFR vent fields.
Geodetic constraints on the composition of Mars
Authors: Bills Bruce G.
Published: February 2008

The mean density and mean moment of inertia are remotely accessible geodetic parameters which provide two integral constraints on the radial density profile of Mars. The mean density is presently well known, but until the axial precession rate is better determined, the moment of inertia will remain uncertain. Values anywhere in the interval from 0.345 MR2 to 0.365 MR2 can be obtained from the observed gravitational field, depending on how that field is partitioned into hydrostatic and nonhydrostatic components. Even if the moment were accurately known, a considerable degree of nonuniqueness would still remain concerning the density and composition. This nonuniqueness is illustrated by construction of a family of orthogonal polynomials in the normalized radius which make no contribution to either the mean density or the mean inertial moment. If the mean moment is near to the lower end of its plausible range, the nonuniqueness in density and composition is considerably diminished. In order to avoid unrealistically high densities in the deep interior, the Martian mantle must have a density appreciably lower than the terrestrial mantle and must consequently be significantly depleted in iron. On the other hand, if the mean moment is near the upper end of its plausible range, a much broader range of density profiles can be accommodated, including (but not restricted to) iron enriched mantles.
Local structure in gallium‐ and germanium‐substituted silicate glasses investigated by magic angle spinning nuclear magnetic resonance
Authors: Sherriff Barbara L. , Fleet Michael E.
Published: February 2008

Local structural effects occurring with the substitution of gallium for aluminum and germanium for silicon in synthetic glasses with albite, jadeite, and nepheline analogue compositions are studied by 29Si, 27Al, and 23Na magic angle spinning nuclear magnetic resonance. There are systematic shifts to low field of the single broad resonance peak in each spectrum with progressive substitution by the larger cations. The effect of substitution of the next nearest neighbor tetrahedral cations (and the change in local structure) on chemical shift is calculated using model structures simulated with a computer graphics structure‐modeling program. Chemical shifts calculated for a random arrangement of tetrahedral cations are in closer agreement with observed chemical shifts than those calculated for ordered local structures complying with aluminum/gallium avoidance and having sodium coupled with aluminum/gallium cations. The observed shifts to low field with the substitution of aluminum or gallium for silicon or germanium are explainable only in part by the next nearest neighbor effect. A decrease in mean bond angle at the bridging oxygen atom, attributable to an increase in the number of small‐membered rings of TO4 tetrahedra, could account for further low‐field shifts, thus corroborating the findings of Henderson et al. (1985) from Raman spectroscopy.
Phase relations of aluminum‐undepleted and aluminum‐depleted komatiites at pressures of 4–12 GPa
Authors: Wei Kejian , Trønnes Reidar G. , Scarfe Christopher M.
Published: February 2008

The anhydrous phase relations of natural Al‐undepleted komatiite (AUK) with 25% MgO and Al‐depleted komatiite (ADK) with 32% MgO have been investigated in the pressure range from 4 to 12 GPa, using samples from Munro Township, Ontario, and the Barberton Mountains, South Africa. The experiments were carried out with graphite or molybdenum capsules in 18‐mm octahedral pressure cells in a uniaxial split‐sphere multianvil apparatus. The thermal gradient within the stepped resistance heaters of graphite and lanthanum chromite was about 50°C/mm. For both compositions, the liquidus phase is olivine at low pressure (up to 5.6 and 9.6 GPa for the AUK and ADK, respectively) and garnet at high pressure. Pyroxene is the only liquidus phase in an intermediate pressure range for the ADK (9.6–11.5 GPa) and reaches the liquidus at a multiple saturation point with olivine and garnet at 5.6 GPa pressure for the AUK. The subsolidus assemblage consists of olivine, pyroxene, and garnet in the entire pressure range for both of the compositions. The pyroxenes have variable CaO contents, and most of them are subcalcic clinopyroxenes, but minor amounts of orthopyroxene have been observed in some of the run products. If AUK and ADK compositions represent near primary magmas, the melt separation most likely occurred at pressures corresponding to the three phase saturation point at 5.6 GPa for AUK and one of the two cosaturation points (olivine‐pyroxene at 9.6 GPa and pyroxene‐garnet at 11.6 GPa) for the ADK. The low Ca/Al ratio of the AUK requires a nearly complete melting of garnet. The high Ca/Al ratio of the ADK indicates that garnet was a residual phase at the time of melt separation, or that the mantle source experienced some premelting or synmelting garnet fractionation. The clinopyroxene liquidus interval between 9.6 and 11.6 GPa excludes the coexistence of garnet and olivine in the residue, and the following alternative petrogenetic models are suggested for the ADK: 1. The initial melt was more magnesian than the source peridotite, and the melting progressed to the stage of disappearance of the residual olivine. The melting progressed further along the pyroxene‐garnet cotectic before melt separation. 2. Garnet fractionation took place from an ascending and partially molten peridotite diapir. Further melting of the upper portion of the diapir produced a melt that was less magnesian than the source diapir. This could lead to total melt consumption of any remaining residual garnet, and further melting could proceed along the olivine‐pyroxene cotectic before final melt separation.
Analysis of long‐period seismic waves excited by the November 1987 eruption of Izu‐Oshima Volcano
Authors: Takeo Minora , Yamasato Hitoshi , Furaya Itsuo , Seino Masaaki
Published: February 2008

Long‐period seismic waves, which were excited by two eruptions of Izu‐Oshima volcano in November 1987 and recorded at an Abbreviated Seismic Research Observatory station and at several volumetric strain meter stations, are analyzed to determine kinematic seismic source models associated with the eruptions. The seismic waves have unusual features in the radiation pattern and waveforms of Rayleigh waves which cannot be explained in terms of a shear dislocation model. Waveform inversion is applied to obtain a kinematic source model which is parameterized by a single force and a seismic moment tensor. Many geophysical and field observations make clear that the two eruptions occurred in a lava drain‐back stage of the volcanic activity. The source model of the seismic event associated with the eruption on November 16, 1987, is mainly composed of a vertical single force with a magnitude of 4×1011 N, and suggests a rapid collapse of overloading lava into the deeper vent The long‐period seismic waves excited by the eruption on November 17, 1987, can be explained by a force system composed of two vector dipoles with nearly vertical orientation which are separated in time by 81 s. The sum of the two dipoles is 1.7×1017 N m. This source model suggests that tension crack openings, or volume expansions of horizontally extended magma reservoirs or of aquifers occurred because of lava drain back.
Introduction to Special Section on the Geological, Geophysical, and Tectonic Setting of the Cascade Range
Authors: Muffler L. J. Patrick
Published: February 2008

The Cascade Range is an active volcanic arc that is formed by the subduction of the Juan de Fuca plate system beneath North America [Riddihough, 1978]. Knowledge of the Cascade Range, its volcanic rocks, and its tectonic setting is not only of broad scientific interest but also bears directly upon the estimation of geothermal resources and the evaluation of volcanic and seismic hazards.

An understanding of the regional aspects of the Cascade Range is at the present time particularly important to the assessment of geothermal resources. Although identified geothermal resources in the Cascade Range are modest [Brook et al., 1979], substantial undiscovered geothermal resources have been inferred [e.g., Brook et al., 1979; Black et al., 1983; Bloomquist et al., 1985], primarily from the favorable volcanic and tectonic setting but also from high regional heat flow along the Cascade Range [Blackwell et al., 1982]. Consequently, a multiyear, multidisciplinary program of studies to refine the geothermal resource estimates of the Cascade Range is a major objective of the U.S. Geological Survey (USGS) Geothermal Research Program [Muffler, 1987]. The smallest and easiest part of this effort is an updated inventory of known hydrothermal convection systems. A much larger and far more difficult task is the estimation of the undiscovered geothermal resources. Existing drill hole information in the Cascade Range is sparse, and under the foreseeable economic climate, direct evaluation of the thermal regime by numerous deep holes is unlikely. However, the magnitude of the undiscovered geothermal resources can be addressed indirectly by an analysis of the tectonic, geophysical, volcanic, and hydrologie setting of the Cascade Range, thus allowing extrapolation of available drill hole data.
A one‐million‐year history of the 11°45′N East Pacific Rise discontinuity
Authors: Perram Laura Jean , Macdonald Ken C.
Published: February 2008

Bathymetric, magnetic and side scan sonar data from a June 1987 SeaMARC II cruise aboard the R/V Moana Wave have been combined with additional data in an area 140 km by 154 km centered on the overlapping spreading center pair (OSC) located at 11°45′N on the East Pacific Rise (EPR). The purpose of this study is to correlate and interpret these data sets in order to determine the recent (<1 m.y.) history of this OSC. The data sets include gridded bathymetry and magnetic field anomalies, a side scan sonar mosaic, and a fault map. The bathymetry and anomaly grids were used as inputs in a three‐dimensional Fourier inversion resulting in a crustal rock magnetization distribution solution. The most prominent feature of all five maps is a roughly V‐shaped anomalous zone centered on the OSC. The zone is characterized by a positive depth anomaly, a negative magnetic field anomaly within the central (positive) anomaly and a zone of high magnetization in the inversion solution. A hummock y texture and sparse, curved faults mark the zone in the side scan mosaic and fault map. The shape of this zone indicates a short period of northward migration of the discontinuity 0.72–0.6 Ma at approximately 75 mm/yr followed by slow (less than 30 mm/yr) and then fast (140–200 mm/yr) southward migration for the past 0.6 m.y.. The anomalous zone is not well defined beyond the edge of the central anomaly which is straight and continuous, indicating that if this discontinuity of the EPR existed 0.72 Ma, its offset was negligible. The present‐day axis has an orientation of 349°, the edge of the central anomaly has an orientation of 353°, and Jaramillo‐age crust to the east of the EPR has an orientation of 353°–355°. This variation in magnetic linealion directions suggests a 4° to 6°‐counter‐clockwise change in the direction of spreading in the past 1 m.y. which seems to have been accommodated by asymmetric spreading. Variations in mean fault trend with age are consistent with a counter‐clockwise change in the direction of spreading for the same time period.
Soil gases in geothermal prospecting: Two case histories (Sabatini Volcanoes and Alban Hills, Latium, Central Italy)
Authors: Bertrami R. , Buonasorte G. , Ceccarelli A. , Lombardi S. , Pieri S. , Scandiffio G.
Published: February 2008

Studies were conducted to test the effectiveness of soil gas surveying for locating permeable zones in buried carbonate reservoirs and to locate the presence of possible gasoeus haloes linked to active geothermal systems. Two surveys were conducted in the Sabatini Volcanoes and Alban Hills areas. Each area is characterized by a thermal anomaly and a scarcity of surface manifestations. In the former area, CO2, H2, He, and CH4 in soil gases were determined; in the latter total helium in about 1000 soil gas samples and in about 400 water samples was determined. In both cases, anomalous concentrations of the gases were found mainly according to fault or fracture systems. Therefore it seems possible to utilize the distribution of the gases in these zones as indicators of deep permeability.
Experimental and theoretical constraints on the iron equation of state
Authors: Grover Richard
Published: February 2008

Model equations of state for solid and liquid iron in the range of conditions of interest to geophysicists are developed with the constraints provided by available experimental data and theoretical calculations. Sensitivities to various uncertainties are indicated by example. The important role of the two‐phase liquid‐solid region in the properties of the inner and outer core is illustrated.
Pacific‐North America Plate motions: New results from very long baseline interferometry
Authors: Ward Steven N.
Published: February 2008

Expansion and densification of the very long baseline interferometry (VLBI) network by the NASA Crustal Dynamics Project continues to clarify details of Pacific‐North America motions. In this paper I construct, for the first time, rigid plate tectonic models based purely on space geodetic data. Construction of VLBI plate models has the advantages of averaging the bias and errors of individual site velocities, making failures in the rigid plate assumption easy to document, and allowing the consistency of specified plate models to be quantified against the VLBI data set as a whole. VLBI‐based rigid plate models VM2 and VM3, obtained by fitting vector velocities of 10 sites in the stable interiors of the North America and Pacific plates, reveal a misfit of VLBI observations and RM2 (Minster and Jordan, 1978) predictions significant at the 99% confidence level. NUVEL l (DeMets et al., 1990) reproduces the velocities of these 10 sites far better than RM2 and offers a fit to the data which is statistically indistinguishable from VM2 and VM3. By including velocities of 16 additional stations in the deforming plate margin, VM2 and VMS can resolve all four terms (VPN, total Pacific‐North America motion, VSA San Andreas slip, VE,W, path integrated deformation east and west of the San Andreas) in the vector equation characterizing Pacific‐North America plate boundary deformation: VPN ‐ VSA = VE ‐ VW for several points along the San Andreas without reference to a global plate model, geological or local geodetic measurements, or restrictions on distributed shear. In most cases, instantaneous VLBI‐determined rates agree with geologically based estimates. Mapped to point C (36.0°N, 120.6°W) in central California, VM2 gives VPN(C) = 46.8±1.4 mm/yr (N36°±2°W), VSA(C) = 38.6±1.3 mm/yr (N36°±2°W), and VE(C) = 8.2±1.3 mm/yr (N34°±7°W). VLBI substantially eliminates VW(C), the component of the San Andreas Discrepancy west of C, although a few millimeters per year of right‐lateral strike slip on offshore faults can not be rejected. At point D (34.1°N, 117.0°W) in southern California, VM2 returns VSA(D) = 25.0±1.1 mm/yr (N52°±3° W), VE(D) = 8.8±1.1 mm/yr (N25°±8°W), and VW(D) = 13.3±1.6 mm/yr (N21°±5°W). VW(D) is accommodated west of the San Andreas to the Channel Islands. The azimuth of San Andreas slip suggests that the transverse ranges north of Los Angeles are absorbing 8±1 mm/yr of compression perpendicular to the trend of the fault.
The impact of the chlorocarbon industry on the ozone layer
Authors: Crutzen Paul J. , Isaksen Ivar S. A. , McAfee John R.
Published: February 2008

By means of calculations with a one‐dimensional photochemical‐diffusive model of the atmosphere a theoretical estimate is given of the present and the possible future impact of large sections of the chlorocarbon industry on the ozone layer. Our estimates for 1976 are that past chlorocarbon emissions may be responsible for a 1.5% reduction in the global total ozone content (0.8% by CFCl3 and CF2Cl2, 0.5% by CCl4, and 0.2% by CH3CCl3). This estimate was obtained by comparison with the ozone content of a model atmosphere without industrial chlorocarbon emissions. The effect of the nonindustrial gas CH3Cl can best be described by stating that without CH3Cl, there would be almost 1% more ozone in the atmosphere. Considerable attention should also be given to the atmospheric effects of expanding uses of CH3CCl3. The potential impact on the ozone layer of CHFCl2 and CHF2Cl emissions is also discussed. However, there are too many uncertainties regarding the tropospheric concentrations of OH and its role as a scavenger to assess the effect of a number of chlorocarbon compounds reliably. The effect of other chlorocarbon compounds (C2Cl4, C2HCl3, C2H5Cl, C2H4Cl2, CHCl3) on the ozone layer is estimated as being comparatively negligible. Model‐calculated vertical distributions of a large number of constituents are compared with observations. Substantial deviations between some theoretical and reported concentrations exist, especially for NOx, CO, and ClO. Uncertainties in our knowledge of stratospheric chemistry are discussed. It is concluded that these uncertainties are sufficiently numerous to take the given predictions of ozone reductions with some reservations.
The effects of cloud height, thickness, and overlap on tropospheric terrestrial radiation
Authors: Kuhn William R.
Published: February 2008

The infrared radiation reaching the earth's surface, the outgoing radiation at 50 mbar, and the tropospheric infrared flux divergence have been calculated for various cloud covers, heights, thicknesses, and amount of cloud overlap. The results are presented in a series of diagrams. For comparable cloud covers their effects on the downward surface flux and flux divergence decrease toward lower latitudes because of the shielding by larger water vapor amounts. Surface flux due to cloud cover in the tropical model is increased by as much as 10%, while during winter in the subarctic the increase may amount to 60% of the clear sky value. Tropospheric flux divergence can either increase or decrease depending on cloud height; for clouds below approximately 500 mbar the divergence increases, and in the polar regions with clouds very near the surface this increase can reach values about 80% larger than the divergence for clear skies. The degree of cloud overlap causes as much as a 3% uncertainty in downward flux in the tropics, but in polar latitudes during winter the uncertainty is 26% for two cloud layers each covering 50% of the sky. The water vapor continuum and temperature‐dependent transmission functions should be considered if fluxes and flux divergences are required to an accuracy of about 10%.
Coastal currents and an associated sand stream off Virginia Beach, Virginia
Authors: Ludwick John C.
Published: February 2008

Synoptic data on near‐surface and near‐bottom currents for two 1‐month periods are analyzed for six stations located 3.5–7 km offshore. Tidal currents are rotary with long ellipse axes approximately parallel to the shoreline and are nearly synchronous. On the basis of amplitude the seven largest constituents of the currents were identified as M2, S2, N2, K1, O1, J1, and SO1. Maximum tidal current speed decreases with distance to the south away from the entrance to Chesapeake Bay. Near the bottom, tidal currents at spring strength decrease from 32.4 cm/s at the entrance to 8.2 cm/s at a point 22 km to the south. Near‐bottom tidal currents are incompetent by themselves to move fine sand except in the entrance area. Forty‐hour low‐pass currents are generated by winds and by sea surface slopes. They reach peak speeds near the surface of 48 cm/s in events of up to 6 days' duration. In summer a strong pycnocline inhibits downward propagation of these high‐speed surface currents. In the fall the surface currents penetrate more readily to the bottom. Winds to the south in summer generate stronger currents than winds to the north having the same speed. Seasonal variations in wind regimes and corresponding currents seem to require a strong south slope to the sea surface in summer and a very gentle slope to the north in the fall. Waves entrain the bed sediment 60–83% of the time in depths of 8–13 m. With a threshold taken at 20 cm/s, only the south‐directed low‐pass currents supplement the incompetent tidal currents so as to produce sediment transport. Threshold exceedance in 8–13 m occurs 1–2% of the time under south‐flowing low‐pass currents in summer and 3–5% of the time under southerly low‐pass currents in the fall. At 15 m the transport threshold was not reached during the observation period. A coastwise parallel stream of intermittent bed sediment transport is thus defined. The frequency of exceedance decreases to the south away from the entrance area. This decrease is consistent with the seaward bulging configuration of isobaths east of Cape Henry.
The near‐surface ocean mixing layer in stable heating conditions
Authors: Thorpe S. A.
Published: February 2008

Evidence is presented to show that Kelvin‐Helmholtz instability dominates the structure in the mixing region near the sea surface when there is a net flux of heat into the sea and in conditions soon after the onset of wind.
Velocities and refraction laws of wave groups: A verification
Authors: Breeding J. Ernest
Published: February 2008

The conventional definition of group speed U = dω/dk is the speed of a wave group composed of collinear wave components. When there is dispersion and refraction, the wave components cannot remain parallel. Then U is found to be the apparent speed of the group in the direction of movement of the wavelets within the group. The velocity of a group composed of nonparallel wave components is found to depend upon the directional distribution of the wave components, and it is here termed the geometric group velocity. The geometric group speed G = U cos ϕ, where the angle ϕ is the difference between the direction of the wave group and the direction of the wavelets. For a wave group in which the bandwidth and the directional spread of the wave components are both small the wavelet velocity is nearly equal to the phase velocity of a wave component. The path of a wave packet is found to be given by Snell's law with the geometric group velocity, while at each point along the path the wavelets have a direction defined by Snell's law with the wavelet velocity. The findings are illustrated by using examples of gravity water waves and are confirmed by field observations.
The microscale sensing array
Authors: Dahlen John , Shillingford John
Published: February 2008

A moored self‐recording instrument designed to measure the fine scale temperature and velocity vector variability of the ocean in a vertical plane containing the mean velocity vector is described. (Since the conception, design, and naming of the microscale sensing array (MSA) the scale designation of phenomenon with wave lengths in the range (0) 1 to (0) 10 m has been changed from ‘mieroscale’ to ‘fine scale.’) The structure holds 16 water velocity sensors (propellors) and 14 water temperature sensors (thermistors). These sensors are mounted along two vertical masts, each 8 m long, separated horizontally by a 20‐m spar. The whole structure is rigid, buoyed by two aluminum spheres, each 1 m in diameter, providing a net buoyancy for the instrument of about 386 kg. Contained within the spheres are an electronic data acquisition system, a magnetic tape recorder, primary batteries, a compass, and accelerometers to measure roll and pitch attitude. A separate cylindrical housing contains a pressure transducer and preamplifiers to sense depth. Provision is made to measure MSA translational motion by means of an acoustic transceiver and remote transponders. Instrument life is primarily dependent upon tape storage (53 million bits) and data sampling rate, which is easily preset to various continuous or burst modes. Maximum allowable operating depth is presently 900 m. The MSA has been deployed four times in the main thermocline southeast of Bermuda and once in the New England Continental Shelf bottom boundary layer.
The heat budget of a region in the eastern Bering Sea, summer 1976
Authors: Reed R. K.
Published: February 2008

Changes in heat content of the upper ocean for two adjacent 1° × 1° areas (56°–57°N, 164°–166°W) in the eastern Bering Sea were investigated with the data from three quasi‐synoptic surveys in June, August, and September 1976. Data from current meters indicated that the net flow was very weak, and advection of heat was neglected. The mean local change of heat content for the two areas for the June–August period was 0.20 cal cm−2 min−1; during August–September the local change was 0.06 cal cm−2 min−1. Mean surface exchange for the two periods was estimated by recently evaluated empirical formulas (using data from satellite photographs and weather reports) to obtain values of 0.20 and 0.05 cal cm−2 min−1. The data also suggested that the gain of heat through horizontal diffusion was not more than 0.01 cal cm−2 min−1. Thus for both periods there was excellent agreement between the local change of heat and the net surface exchange. It appears that net radiation is typically the dominant heat flux affecting much of the eastern Bering Sea in summer, although in early fall, evaporation starts to assume importance. This region is quite unusual in that heat advection and diffusion have little effect on the heat balance. Lack of motion allows the effects of various physical processes to be examined.
Modeling the presence of wave groups in a random wave field
Authors: Mollo‐Christensen E. , Ramamonjiarisoa A.
Published: February 2008

Field and laboratory observations of surface wave fields show that the propagation speed of harmonic wave components differs from the predictions of linear theory. Angular spread fails to account for the observed discrepancy. An explanation is that the wave field does not consist of independently propagating Fourier components only but also contains groups of Stokes waves, forming envelope solitons. A model field is proposed, and the power spectral density and wave number spectra, as well as cross spectra, are calculated and compared to observations. A method is also suggested for identifying the properties of solitons contained in an observed wave field from spectra and cross spectra.
Trace metal enhancement in the biotic and abiotic components of an estuarine tidal front
Authors: Sick L. V. , Johnson C. C. , Engel R.
Published: February 2008

A frontal system of lower Delaware Bay was investigated to illustrate the role that such tidal fronts can have in concentrating trace metals and serving as a means for introducing trace metals into the trophic hierarchy of estuaries. This frontal system typically develops on ebb tide and can extend at least 32 km parallel to the central axis of Delaware Bay. In relation to samples collected on either side of the front, chlorophyll a concentrations and concentrations of selected trace metals in zooplankton, particulates, and the dissolved fraction were significantly higher in samples collected at the front. Seasonally, concentrations of cadmium and copper in all fractions were highest during the summer or fall. Differences in taxonomic composition of zooplankton assemblages, as well as differences in total numbers of organisms across the front, suggested advective transport by convergent water masses.
Temperature fine structure observations in the tropical North Pacific Ocean
Authors: Hayes S. P.
Published: February 2008

Temperature profiles at two locations in the tropical North Pacific Ocean (8°27′N, 150°47′W and 11°43′N, 138°23′W) are analyzed and compared with similar data from the central gyres of the Atlantic and Pacific oceans. The vertical fine structure spectra in the thermocline (300–600 m) divide into two wave number bands, each of which has a distinct slope. For 0.003 < k < 0.1 cpm the power law dependence is about k−2. For 0.1 < k < 0.5 cpm the power law is k−3. The low‐wave number band results agree with internal wave models, and comparison of our data with the other measurements supports the universality of deep ocean internal wave spectra. The high‐wave number spectra suggest that different processes are responsible for these features. Time‐lagged coherence between temperature profiles at one location separated by time lags of up to 10 hours was calculated at the 11°43′N, 138°23′W site. This coherence depended upon the wave number band. For k < 0.04 cpm the coherence had wavelike behavior; however, the semidiurnal tide appeared important. At higher wave numbers, no significant coherence was found.
Microstructure and fine structure in an upper ocean frontal regime
Authors: Gargett A. E.
Published: February 2008

For constant pressure towed measurements a simple temperature/salinity (T/S) technique separates effects of vertical stratification from those of along‐isopycnal variations of water properties indicative of interleaving. This technique is used to examine the occurrence of temperature microstructure and T/S fine structure in relation to a mesoscale feature which may be part of a frontal region between coastal and oceanic waters in the northeastern Pacific. The temperature microstructure seems to be concentrated at the boundaries, both vertical and lateral, of intrusive features which presumably have their origin in the larger mesoscale field. The association of temperature microstructure with lateral variation of water properties in frontlike structures implies problems with the Osborn‐Cox model normally used to estimate vertical heat fluxes from measurements of the temperature microscale.
Fine structure instabilities induced by double diffusion in the shelf/slope water front
Authors: Posmentier Eric S. , Houghton Robert W.
Published: February 2008

Intervals of negative stability have been observed which appear as part of distinct loops in the T‐S diagram of CTD hydrographic stations near the shelf break in the New York Bight. These features occur within the shelf break frontal zone, which is associated with active interleaving between warm salty slope water and cooler fresher shelf water. Double‐diffusive mixing is proposed as the mechanism responsible for the observed T‐S correlations.
Simulation of coastal upwelling frontogenesis with an isopycnic coordinate model
Authors: Bleck Rainer
Published: February 2008

A model ocean composed of four isopycnic layers on a β plane is spun up from rest by anticyclonic wind stress. Model equations are formulated in material isopycnic coordinates with no restrictions against vanishing layer thickness. This permits separation of the western boundary current from the coastline and formation of coastal upwelling fronts. The optimum truncation properties of isopycnic coordinates with regard to frontogenesis are discussed and weighted against numerical stability problems associated with the outcropping of isopycnals at the sea surface. Examples of coastal upwelling fronts are presented.
Atmospherics measurements in San Miguel, Argentina
Authors: Harth W. , Hofmann C. A. , Falcoz H. , Heydt G.
Published: February 2008

Measurements of VLF atmospherics taken at San Miguel, Argentina, are presented. Results from one 13‐year measurement period (1956–1969) as well as one 2‐year interval (1971–1973) are used to document the morphology of the diurnal and annual variations in atmospherics activity at San Miguel. The atmospherics rates obtained during the second interval, which may be ordered according to arrival azimuth, show that most of the activity originates in thunderstorm cells located NE and NW of the observation station. Distance determinations from the dispersion of the atmospherics impulses, together with an estimate of the instrument's range, indicate that these activity cells lie primarily over the South American continent. Additional measurements of atmospherics activity taken in Berlin from 1971 to 1975 are also shown, from which a certain trend in the activity in the South American sector may be inferred. Both the Berlin and San Miguel records indicate a decline in atmospherics activity over the measurement period.
Long‐range acoustic transmission in the northwest Atlantic
Authors: Brown Michael G. , Munk Walter H. , Spiesberger John L. , Worcester Peter F.
Published: February 2008

An acoustic propagation experiment conducted west of Bermuda during the fall of 1978 demonstrated that individual acoustic arrivals at 900‐km range were stable and identifiable over a 48‐day period. The observed arrival pattern is interpreted by geometric ray theory and by comparison with a ‘synthetic sofargram’ (equivalent to a synthetic seismogram) constructed from WKBJ theory. Using geometric ray theory, we examine the expected generation and annihilation of ray paths as a result of the seasonal erosion of the autumnal thermocline. Many rays are converted from purely refracted to surface reflected/refracted rays. The ultimate goal of this work is to interpret variability in acoustic transmission in terms of ocean variability.
Near‐bottom speed and temperature observations on the Blake‐Bahama Outer Ridge
Authors: Weatherly Georges L. , Wimbush Mark
Published: February 2008

Speed and temperature measurement made in the bottom boundary layer (BBL) in the region of the Western Boundary Undercurrent at 28°22′N, 74° 13′W over an ∼11 day period are presented. The observations suggest that the BBL structure is consistent with that of a turbulent Ekman layer formed in an initially stably stratified fluid over a uniform surface even though they were obtained in and above an abyssal furrow. The inferred friction velocities u*(ū* = 0.66 cm/s) generally are larger than those inferred by Weatherly (1972) under the Florida Current and at times sufficiently large to result in erosion of some of the finer cohesive sediments if the criterion for their erosion summarized in McCave (1978) is assumed to apply at the site of the observations.
A two‐dimensional transport simulation model for trace atmospheric constituents
Authors: Hyson P. , Fraser P. J. , Pearman G. I.
Published: February 2008

A two‐dimensional atmospheric transport simulation model is described which is designed to facilitate the interpretation of observed distributions of primary tropospheric trace gases. Transport by large‐scale advection is based on published meridional velocity fields, while the eddy diffusion component of the transport is based on published diffusion coefficients adjusted to produce agreement between model generated and observed global distributions of CCl3F. The observed CCl3F distribution presented here is useful in this context as it is based on recent multiple observations at six globally distributed background monitoring stations which use calibration gases based on a common standard. The model incorporates both northern and southern hemisphere CCl3F release estimates. It is found that in recent years the global rate of increase in tropospheric CCl3F concentration is higher than that consistent with available release data. The model results indicate interhemispheric exchange times (70°N to 70°S) of approximately 8 months.
Observations on acidity in continental and in marine atmospheric aerosols and in precipitation
Authors: Winkler P.
Published: February 2008

From systematic analysis of electrical conductivity and pH value of aerosol leaching solutions, the amount of free acid in the water soluble portion of the aerosol is derived. In continental European aerosols, Aitken particles have a higher percentage of free acid than the particles >0.1 μm radius. In the marine atmosphere we observe an increasing percentage of free acid with decreasing radius. In winter, episodes of high free acidity are observed. Free acid in precipitation usually is low when the pH value is high. With decreasing pH the relative amount of free acid rises to 30–40% of the total amount of inorganic ions dissolved in rain. During evaporation of precipitation samples (pH > 4.2) or of leaching solutions of aerosols, the electrical conductivity changes according to the decrease in volume. The H+ ion concentration, however, increases less, most probably owing to a buffer mechanism. For precipitation samples with pH <4.2, the H+ ions show normal behavior. Mixing of the leaching solutions of Aitken particles and of particles >0.1 μm causes chemical reactions that either decrease or increase the amount of free H+ions. A yearly cycle was observed indicating neutralization in summer and production of free acid in winter. This effect, however, is very small.
Mechanisms of wave transformation in finite‐depth water
Authors: Shemdin O. H. , Hsiao S. V. , Carlson H. E. , Hasselmann K. , Schulze K.
Published: February 2008

Mechanisms of wave transformation in finite‐depth water are investigated. The linear mechanisms examined are percolation, bottom motion, shoaling, and refraction. The nonlinear mechanisms examined are wave‐wave interaction and bottom friction. New exact computations of the nonlinear transfer for finite‐depth waves are presented for some directional wave spectra. These mechanisms are found to explain satisfactorily wave decay observations obtained at several sites with different bottom sediment properties. The decay rates at these sites are found to be dominated by different mechanisms which are determined by the bottom conditions. As an example, detailed calculations are presented for data obtained at the Jonswap site.
Heterogeneous reactions of Cl and ClO in the stratosphere
Authors: Martin L. Robbin , Judeikis Henry S. , Wun Marilyn
Published: February 2008

Experimental measurements of the heterogeneous reactivity of sulfuric acid‐water mixtures at low temperatures are presented. The kinetic data are combined with a stratospheric aerosol‐loading model and simple chemical models to predict the effect of heterogeneous chlorine and chlorine oxide radical reactions on the stratospheric Cl/HCl ratio at several altitudes. The Cl reactions are found to have little influence, but the ClO reaction reduces the Cl/HCl ratio by about 3% at 20 km (within a factor of 2 at 1 standard deviation). The effect at higher altitudes is smaller. Simulated sunlight was found to have no effect on the heterogeneous reactivities.
CACGP Symposium
Authors: Cicerone Ralph J.
Published: February 2008

This is the second of several issues to contain papers presented at the Symposium on Budget and Cycles of Trace Gases and Aerosols in the Atmosphere. (Journal of Geophysical Research, 85, August 20, 1980, contained the first group of papers.) Held August 12–18, 1979, in Boulder, Colorado, the symposium was part of the Fourth International Conference of the Commission on Atmospheric Chemistry and Global Pollution (CACGP). The principal convenor of the symposium was the past CACGP Secretary, P. Goldsmith, of the Meteorological Office, Bracknell, United Kingdom; his efforts were complemented by the past CACGP President, E‐. A. Martell, of the National Center for Atmospheric Research, Boulder, Colorado.
Sources of twelve trace metals in Antarctic snows determined by principal component analysis
Authors: Boutron Claude , Martin Serge
Published: February 2008

More than 3000 concentrations data obtained by the analysis of 12 trace metals in 250 snow samples collected in various locations in Antarctica have been processed through principal components factor analysis. The interpretation of the groups of covariant metals so obtained allows estimation of the relative contributions of the various aerosol sources to the trace metals content of Antarctic aerosols. Al, Fe, and Mn are shown to be crustal‐derived in all locations. The origin of Na, Mg, K, and Ca depends on the distance from the sea: the influence of the marine source decreases from the sea coast to a distance of about 500 km, where the influence of the crustal source becomes predominant; it increases then toward the most central areas of the Antarctic ice cap. The ‘anomalously enriched elements’ Pb, Cd, Cu, Zn, and Ag are clearly shown to be derived from one or possibly several sources independent of both the oceanic and the crustal sources.
A comparison of ship and satellite measurements of sea surface temperatures off the Pacific coast of Canada
Authors: Tabata S. , Gower J. F. R.
Published: February 2008

A comparison of ship and satellite measurements of sea surface temperatures indicates that a simple linear regression appears to be sufficient to relate the two sets of data obtained from a limited area and over a limited period to within a standard error of 0.5°C. A comparison of the distributions of sea surface temperatures based on continuous shipborne measurements along the cruise track and on satellite data indicated that many similar features were present in both sets of data. Some features, such as oceanic fronts and relative maxima and minima of temperatures along cruise tracks, are reproduced in the satellite data. The difference in the features depicted in the two sets of data over the continental shelf is attributed to actual changes in the features rather than to the difference in the methods of the two sets of measurements. Some of the well‐defined features present in the satellite data can be related to characteristic coastal circulation pattern, upwelling, vertical mixing, and instabilities in the flow.
Somali eddy formation during the commencement of the southwest monsoon, 1978
Authors: Bruce J. G. , Quadfasel D. R. , Swallow J. C.
Published: February 2008

An early stage of the Somali eddy circulation was mapped in the period May 29 to June 13, 1978, using expendable bathythermograph data at closely spaced stations. By this time the SW monsoon had been blowing at 5°N for about 4 weeks and the large anticyclonic eddy in the northern Somali Basin was clearly discernible between 3°N and 10°N. It is estimated that the offshore transport at this time was approximately half of that occurring during the period when the eddy reaches maximum size and strength during August and September. A smaller southern eddy was observed just offshore between the equator and 3°N.
Bulk composition of aerosols in the remote troposphere
Authors: Huebert B. J. , Lazrus A. L.
Published: February 2008

Bulk measurements of particulate NO3−, SO3−−, Cl−, and NH4+ were made over continental and marine areas, at altitudes from 0.17 to 7 km, as a part of project Gametag. Above the boundary layer, little difference was noted between marine and continental values for all but NH4+. Average marine/continental values in the free troposphere were NO3−, 0.10/0.13; SO4−−, 0.18/0.30; Cl−, 0.13/0.20; and NH4+, 0.02/0.07 ppbm, respectively. Within the boundary layer, however, NO3− and NH4+ were considerably higher in continental samples because of the anthropogenic and biological sources of NOx and NH3, while Cl− was, as expected, much higher in marine areas. The marine/continental boundary layer averages were NO3−, 0.22/0.62; SO4−−, 0.86/1.11; Cl−, 3.9/0.25; and NH4+, 0.11/0.27. Significant positive correlations were found between most of the bulk particulate concentrations in the continental boundary layer. No significant correlations were found with latitude, however.
Variations of O(1D) photoproduction rate for the 1977 Gametag flights
Authors: Hanser Frederick A. , Sellers Bach
Published: February 2008

An ultraviolet spectroirradiometer (UVS) has been used to measure downward‐going solar flux in the 290‐ to 410‐nm spectral region. Broadband pyranometers were used to measure the ratio of upward‐going to downward‐going flux in the 300‐ to 400‐mn range to derive a band‐averaged effective ground albedo. Use of these data with atmospheric scattering calculations, the ozone UV absorption cross sections, and the spectral O(1D) quantum yield allows the calculation of J0, the local photoproduction rate of (1D) from O3. The photoproduction rate J0 varies strongly with effective ground albedo, total ozone, and solar zenith angle, and less with altitude. Results are consistent with photoproduction rate calculations taking ground albedo into account and show that accurate determination of J0 requires measurement of UV fluxes.
Stratospheric NO measurements: A new balloon‐borne chemiluminescent instrument
Authors: Weiler K. H. , Fabian P. , Flentje G. , Matthews W. A.
Published: February 2008

A description of a new chemiluminescent balloon sonde for measuring stratospheric nitric oxide is given. First results from three flights at mid‐latitudes are presented, including measurements showing a slow reduction in NO mixing ratio beginning 2½ hours before sunset. A hysteresis in the NO mixing ratio between ascent in the morning and descent in the afternoon was observed. The afternoon values were found to be up to a factor of 2 larger than the morning values.
Absorption cross section of CF4 at H Lyman α (121.57 nm)
Authors: Inn Edward C. Y.
Published: February 2008

Measurement of the absorption cross section of CF4 at 121.57 nm is reported with a value of σ = (5.73±0.97) × 10−27 cm2. The applicability of this result to Cicerone's recent calculations of the atmospheric residence time of CF4 assuming photodissociation of CF4 by solar H Lyman α in the mesosphere is noted.
Contents of formaldehyde in the air above the surface of the ocean
Authors: Fushimi Katsuhiko , Miyake Yasuo
Published: February 2008

Contents and distributions of formaldehyde in the air above the open ocean surface of the western North Pacific and the Indian Ocean were observed. The determination was done by the spectrophotometric method with coloring reagents of chromotropic acid and AHMT on board the research vessels during the cruises of Ry–75–05 (April to May 1975, the western North Pacific) and KH‐76‐1 (January to April 1976, the western North Pacific to the eastern Indian Ocean) conducted by the RV Ryofu‐maru and the RV Hakuho‐maru which belong respectively to the Japan Meteorological Agency and the Ocean Research Institute of the University of Tokyo. The formaldehyde content in the air above the western North Pacific Ocean and the Indian Ocean was in the range from less than l microgram to a few micrograms of ·CHO in a cubic meter of air, or from less than 0.8 ppb to a few ppb by volume except in the vicinity of continents and big islands. This content in the maritime air is equal to the smaller values observed so far in rural areas on land, and it may be regarded as a natural background level of formaldehyde in the air in the lower layer of the earth's atmosphere.