bluuebunny/crossref_metadata_2025 huggingface dataset:
Volcanic hot spots on Io: Correlation with low‐albedo calderas
Authors: McEwen Alfred S. , Matson Dennis L. , Johnson Torrence V. , Soderblom Laurence A.
Published: April 2008

Comparison of Voyager imaging data with Voyager 1 infrared observations (IRIS) and with ground‐based telescopic infrared data demonstrates a strong correlation between hot spots and low‐albedo features (reflectivity ≤0.3 in all visual wavelengths) on Io. Most of these low‐albedo areas occur on the floors of volcanic calderas, and many are associated with active or recent volcanism. We use this correlation to identify additional hot spots in regions not observed by IRIS and to model their temperatures. The major features discovered by this method are in a ringlike structure in the south‐polar region (centered at 140°W, 75°S) and Amaterasu Patera (307°W, 38°N). Our model temperature for the south‐polar feature is 280±50 K. Taking account of the high latitudes of these features, the estimated global average heat flow from the hot spots becomes 1.8±0.5 W m−2. Most of this heat emanates from just a few very large hot spots. The global distribution of hot spots is further evidence that Io is a dimorphous body: the hemisphere centered on ∼310°W, 30°S is much more volcanically active than the opposite hemisphere. The styles of heat transfer in Io (conductive versus convective) may be related to the global distribution of hot spots, large eruptive plumes, and large‐scale topographic relief. The correlation between hot spots and dark areas is due to (1) the absence of the bright materials, such as SO2 frost, which cover most of the surface, and (2) the presence of a low‐albedo substance. Spectral properties of the low‐albedo features, extracted from the Voyager multispectral data, are consistent with a number of candidate materials: liquid sulfur, boiled sulfur, silicate‐sulfur mixtures, zinc sulfide, Fe sulfate, and Fe chloride. Quenched sulfur allotropes, on the other hand, are redder than the low‐albedo features on Io and are incompatible with the elevated temperatures of the hot spots. Some of the dark caldera floor materials may be liquid sulfur and/or thermally altered (boiled) sulfur. Liquid sulfur would tend to collect in the topographic depressions and fractured bedrock of the calderas, and this would explain the concentration of low‐albedo material in the calderas. The presence of liquid sulfur is also suggested by the hot spot temperature distribution (typically, 200–400 K) and by morphologies suggestive of lava lakes. However, the liquid/boiled sulfur model does not seem to work for Babbar and Amaterasu Paterae, and the evidence for liquid sulfur is not conclusive.
The nature of crater rays: The Copernicus example
Authors: Pieters Carle M. , Adams John B. , Mouginis‐Mark Peter J. , Zisk Stanley H. , Smith Milton O. , Head James W. , McCord Thomas B.
Published: April 2008

Crater rays are formed during a cratering event as target material is ballistically ejected to distances of many crater radii forming narrow, generally high albedo, approximately linear features extending out‐ward from the crater. The nature of crater rays was examined for the lunar crater Copernicus using new information on the composition of surface material (from near‐IR reflectance measurements), surface roughness (from radar backscatter measurements), and photogeologic data (from available images). Part of the data analysis included use of mixing models to quantify the mixing systematics observed between primary ejecta and local substrate of the ray on the basis of compositional parameters from reflectance spectra. Primary material from Copernicus can be detected in the surface material of rays in decreasing amounts with increasing radial distance (e.g., 20–25% primary ejecta at six crater radii). For distances greater than three crater radii the proportion of local material to primary ejecta observed from these compositional reflectance data is approximately equal to that predicted by previous laboratory and ballistic studies of craters. Within three crater radii the compositional data indicate a higher proportion of primary ejecta than predicted. For extended areas along the ray that do not contain large secondary craters the primary ejecta is intimately mixed on the granular scale with local material throughout the regolith. The relatively high albedo of the rays of Copernicus is due to the feldspathic composition (highland) of the primary ejecta in rays emplaced on a mare substrate. Immature local substrate is only observed in Copernicus's ray at large unmantled secondary craters or other areas with sufficient topographic slope to prevent the accumulation of mature soils.
Neogene tectonic rotation of the San Gabriel Region, California, suggested by paleomagnetic vectors
Authors: Terres Richard R. , Luyendyk Bruce P.
Published: April 2008

Previous paleomagnetic work in the western Transverse Ranges and the islands offshore of California has suggested that these regions have experienced large clockwise rotations since middle Miocene time. This study is aimed at testing how far east these rotations extend into the continent. Neogene volcanic rocks from the region bounded by the San Gabriel and San Andreas faults were selected for paleomagnetic study. The sampled units are lavas from the late Oligocene to early Miocene continental Vasquez Formation, and water‐laid tuff beds from the middle to late Miocene Mint Canyon Formation. These rocks possess a stable remanent magnetization which was acquired soon after deposition and is believed to be primary. Seventy‐four lava flows from eleven locations in the Vasquez Formation were studied. The average direction for seven locations near the center of the study area suggests that this area has rotated a net clockwise amount of 37.1°±12.2° since the early Miocene. There is no suggestion of north or south translation. A location west of the central region is rotated almost 90° clockwise, although this is believed to be a local effect. Detailed magnetic stratigraphy at the western and central location can be correlated over 6 km. Locations in the east near the San Andreas fault yielded highly dispersed directions which cannot now be interpreted in terms of rotation. The mean paleomagnetic direction from six sites (four different beds) in the Mint Canyon formation west of the Vasquez study area is deflected in a counterclockwise sense by 16°±30°. These data are consistent with a proposed model in which the San Gabriel region first was rotated clockwise 53° (37° + 16°) in the early Miocene and later rotated 16° counterclockwise as it slid northward into the leftward bend region of the San Andreas fault. The clockwise rotation is believed to be due to dextral shear within the Pacific‐North American plate shear zone; counterclockwise rotation in the Mojave region is believed to be responsible for the bend in the San Andreas fault.
A method for bounding uncertainties in combined plate reconstructions
Authors: Molnar Peter , Stock Joann M.
Published: April 2008

We present a method for calculating uncertainties in plate reconstructions that does not describe the uncertainty in terms of uncertainties in pole positions and rotation angles. If a fit of magnetic anomalies of the same age and fracture zones that were active as transform faults at that time can be found, such a reconstruction can be perturbed and degraded by small rotations about each of three orthogonal axes (partial uncertainty poles). If the uncertainty in the reconstruction is a consequence of independent, small, but acceptable, rotations about these axes, then the uncertainties in reconstructed points will be elliptical in shape. The dimensions and orientation of such ellipses will depend upon the magnitudes of the perturbing rotations and upon the relative geometry of the partial uncertainty poles and the points in question. In a sequence of rotations, each rotation will contribute an elliptical region of uncertainty for each reconstructed point, and these ellipses can be combined as independent statistical quantities to obtain a confidence ellipse for the sequence of rotations. As a test, we calculated uncertainties for three points on the Pacific plate with respect to North America at the time of anomaly 6 (20 Ma). The computed uncertainties are similar in shape to those that we previously obtained for a sequence of marginally acceptable rotations, but the major axes of the ellipses presented here are about 25% shorter.
Resistivity monitoring of an active volcano using the controlled‐source electromagnetic technique: Kilauea, Hawaii
Authors: Jackson Dallas B. , Kauahikaua James , Zablocki Charles J.
Published: April 2008

A controlled‐source electromagnetic monitoring system located near the summit of Kilauea has been in operation since mid‐1979. Prominent changes in the controlled‐source magnetic fields have been observed both preceding and following two seismic swarms that are interpreted to be related to shallow magma intrusions in August 1980 and January 1981. The vertical magnetic field (Hz) sensor nearest the sites of intrusion showed the largest field changes. All comparisons to date have been made at 1 Hz, which corresponds to a depth of penetration of several kilometers. Large and rapid vertical‐magnetic field changes were measured following the intrusion into the upper east rift of Kilauea on August 27, 1980. Similar fluctuations were measured both before and during the intrusion into the southern caldera on January 20, 1981. Located earthquakes and data from a recording tiltmeter within 2 km of the Hz sensor, which showed anomalous field changes over the January 20 event, indicate that the Hz sensor was located nearly over the zone of intrusion. The Hz field changes recorded over both the August 1980 and January 1981 intrusive events appear too large to have been caused by conductivity changes within a horizontally layered section. More probably, they were caused by relatively shallow intrusion of high‐conductivity magma into open high‐angle fractures or by establishing continuity of short sections of preexisting magma storage zones, thereby producing long linear conductors from short, normally discontinuous conductive segments.
Broad bandwidth study of the topography of natural rock surfaces
Authors: Brown Stephen R. , Scholz Christopher H.
Published: April 2008

The mechanical and hydraulic behavior of discontinuities in rock, such as joints and faults, depends strongly on the topography of the contacting surfaces and the degree of correlation between them. Understanding this behavior over the scales of interest in the earth requires knowledge of how topography or roughness varies with surface size. Using two surface profilers, each sensitive to a particular scale of topographic features, we have studied the topography of various natural rock surfaces from wavelengths less than 20 microns to nearly 1 meter. The surfaces studied included fresh natural joints (mode I cracks) in both crystalline and sedimentary rocks, a frictional wear surface formed by glaciation, and a bedding plane surface. There is remarkable similarity among these surfaces. Each surface has a “red noise” power spectrum over the entire frequency band studied, with the power falling off on average between 2 and 3 orders of magnitude per decade increase in spatial frequency. This implies a strong increase in rms height with surface size, which has little tendency to level off for wavelengths up to 1 meter. These observations can be interpreted using a fractal model of topography. In this model the scaling of the surface roughness is described by the fractal dimension D. The topography of these natural rock surfaces cannot be described by a single fractal dimension, for this parameter was found to vary significantly with the frequency band considered. This observed inhomogeneity in the scaling parameter implies that extrapolation of roughness to other bands of interest should be done with care. Study of the increase in rms height with profile length for two extreme cases from our data provides an idea of the expected variation in mechanical and hydraulic properties for natural discontinuities in rock. This indicates that in addition to the scaling of topography, the degree of correlation between the contacting surfaces is important to quantify.
Subsurface loading and estimates of the flexural rigidity of continental lithosphere
Authors: Forsyth Donald W.
Published: April 2008

The flexural rigidity of the lithosphere is often estimated from the linear transfer function (admittance) between gravity anomalies and topography. Admittance estimates strongly weight provinces with large topographic relief, which will tend to be those provinces with low flexural rigidity if the cause of the topography is subsurface variations in density. If the observed admittance of continents is modeled in terms of surface loading of an elastic plate, there is a strong bias toward low flexural rigidities. Models incorporating both surface and subsurface loading yield much higher rigidities. Although the two models may match the observed admittance equally well, only those with both surface and subsurface loading are consistent with the observed pattern of coherence between gravity and topography as a function of wavelength. A new method of analysis shows that surface and subsurface loading are approximately equal in importance in the vicinity of the Kenya rift valley. The flexural rigidity of the East African lithosphere is about 2×1023 N m, or an effective elastic thickness of the plate of 25–30 km. Data from the conterminous United States are consistent with the presence of provinces with a wide range of flexural rigidities, averaging tens of kilometers in effective elastic thickness.
Geometry and mechanism of faulting of the 1980 El Asnam, Algeria, earthquake from inversion of teleseismic body waves and comparison with field observations
Authors: Nábělek John
Published: April 2008

The El Asnam earthquake of October 10, 1980 (Ms = 7.3), provided a wealth of geological and seismological data and is an ideal event for comparing geologically and seismologically derived models. The event produced extensive surface faulting. In addition to the main tectonic deformation, which is clearly a thrust, widespread secondary normal faulting was observed at the surface. In the southwest region the surface break of a thrust fault could be traced for 24 km. In the northeast part of the fault zone, normal faults with throws of several meters were observed. Although no clear thrust type surface breaks were observed in this region, geodetic measurements and aftershocks indicate that thrusting was nonetheless the main tectonic mode of deformation. In this paper the rupture process of the El Asnam earthquake is investigated by inversion of teleseismic P and SH waves. The effort is concentrated on the late part of the waveforms which carries information about the faulting in the least understood, north‐eastern segment of the fault zone. During the earthquake, rupture initiated at the southern terminus of the southwestern fault segment and propagated northward as indicated by the epicentral location and the observable azimuthal directivity of the body wave shapes and amplitudes. The seismogenic faulting in the southwestern segment has a thrust mechanism with the following average parameters: seismic moment 3.9×1019 N m, depth 6 km, strike 220°, dip 46°, and rake 72°. The duration of rupture on this fault segment was approximately 10 s which, together with the observed fault length of 24 km, indicates a rupture velocity of 2.4 km/s. Unconstrained inversions suggest normal faulting in the northeast part of the source region that began immediately following the arrival of the rupture to the northeast region. The normal faulting mechanism is in agreement with that observed for the large surface fault scarps in this region. Guided by the evidence from aftershocks and geodetic measurements, a solution with a thrust‐type mechanism was also sought. Using a priori constraints based on the field observations (the observed strike and slip angle), we obtain the following thrust source mechanism for the northeast segment: seismic moment 3.6×1019 N m, depth 6 km, strike 230°, dip 20°, and rake 91°. This solution requires that the thrusting in the northeast be initiated 10 s after the arrival of the rupture from the southwest, suggesting that some time is required to overcome the geometric barrier marked by the abrupt change in the dip and azimuth. Inversions are nonunique with respect to the seismic moment associated with normal faulting; the ambiguity being caused by the limited bandwidth of the observed body waves. The moment estimated from the surface waves at periods about 300 s, however, favors thrust faulting to be dominant in the northeast region.
Synthesis of realistic oceanic Pn wave trains
Authors: Ereno Thomas S. , Orcutt John
Published: April 2008

The synthesis of realistic oceanic Pn phases was accomplished using wave number integration. Wave trains with durations of the order of 100 s following the initial compressional wave arrival were generated for a laterally homogeneous, vertically inhomogeneous oceanic lithosphere model. The excitation of these long wave trains is primarily a result of near‐receiver water and sediment reverberations and does not involve scattering. A late arriving wave train with a group velocity of 1.6 km/s having an emergent onset and substantial duration, characteristic of oceanic abyssal T phases, was also generated even with phase velocities restricted to be greater than 5.5 km/s. The synthetic Pn wave train was compared to data collected in the southwest Pacific during the Ngendei Seismic Experiment. Many of the spectral characteristics associated with sediment and water reverberation observed in the synthetics were also observed in the data. First, it was found that the amplitude falloff rate of the Pn wave train is a strongly increasing function of frequency, in direct contrast to results predicted for forward scattered coda. This leads to a predominance of low frequencies late in the wave train which is easily interpreted in terms of the constructive interference of different modes of reverberation. Second, the presence of spectral peaks at frequencies associated with both sediment and water reverberations was observed. The predicted frequencies were computed using values of the water depth, sediment thickness, and sediment velocity obtained in an independent study. Strong alignment of the spectral peaks with the predicted frequencies illustrates the reverberating nature of the Pn wave train. The presence of substantial power in excess of 15 Hz can be attributed to the confinement of Pn to the oceanic lithosphere. The oceanic Pn phase is thus characterized as a refraction from the lower lithosphere with multiple reverberations in the oceanic water column and sediment layer comprising the subsequent coda. Complicated oceanic lithosphere models are not needed to explain the gross characteristics of Pn propagation.
Separated earthquake location
Authors: Pavlis Gary L. , Hokanson Neil B.
Published: April 2008

We present a practical method of locating earthquakes in laterally varying media. The procedure has two distinct phases: an estimation phase, and an application phase. In the estimation phase, all existing arrival time residuals relative to some reference, one‐dimensional velocity model for a region are used to estimate a set of path anomalies (station corrections) that vary as a function of source position. This is done by sorting earthquakes into groups localized in space and applying a novel multiple event location algorithm. This algorithm uses a pair of complementary projection operators to combine a priori information about the lateral structure that is indeterminate from the available data with the information that can be determined uniquely from the available data. Having estimated path anomalies as a function of source location, we can generate a table of path anomalies that can be accessed and interpolated for future earthquake location. This is the application phase of the method. We have tested the method on synthetic data designed to study how well earthquakes can be located in the vicinity of the rupture zone of the 1984 Morgan Hill, California, earthquake. We found precise absolute locations could be obtained, provided the a priori information was specified appropriately. Distortion of relative locations occurred near large lateral velocity gradients and for groups of events spread over large areas because of the inadequacy of fitting a single set of path anomalies to the whole group.
The kinetic photochemistry of the marine atmosphere
Authors: Graedel T. E.
Published: April 2008

The diurnal kinetic photochemistry of the natural marine atmosphere has been simulated by a series of computations including oxygen‐, hydrogen‐, nitrogen‐, halogen‐and carbon‐containing species. Concentrations consistent with oceanic data for the ‘precursor compounds’ CH4, C2H2, C2H4, C2H6, C3H6, CO, CH3Cl, HCl, H2, NH3, NOx, and O3 result from the calculation. The low concentrations of hydrocarbons and NOx cause relatively high concentrations of free radicals such as HO ·, HO2 ·, CH3O2 ·, and ClO · and of the radical recombination products CH3OOH, H2O2, and HOCl. Global oceanic fluxes of the precursor compounds are estimated from the amounts required to balance chemical removal. The values for CH3Cl (1.8×1012 g/yr) and HCl (2.0×1012 g/yr) are among the first flux estimates derived to date. The values for CH4 and total hydrocarbons are small fractions of the total global emission fluxes of these compounds as estimated by alternate techniques. For NH3 and NO the oceanic source fluxes appear to constitute several percent of total global emissions. The oceanic emission flux for CO (0.3–1.8×1014 g/yr for two different assumptions of the average background concentration) is a significant fraction (7–39%) of the total global emission flux of this important atmospheric compound.
A large‐scale numerical model of sea ice
Authors: Parkinson Claire L. , Washington Warren M.
Published: April 2008

Work at the National Center for Atmospheric Research has resulted in the construction of a large‐scale sea ice model capable of coupling with atmospheric and oceanic models of comparable resolution. The sea ice model itself simulates the yearly cycle of ice in both the northern and the southern hemispheres. Horizontally, the resolution is approximately 200 km, while vertically the model includes four layers, ice, snow, ocean, and atmosphere. Both thermodynamic and dynamic processes are incorporated, the thermodynamics being based on energy balances at the various interfaces and the dynamics being based on the following five stresses: wind stress, water stress, Coriolis force, internal ice resistance, and the stress from the tilt of the sea surface. Although the ice within a given grid square is of uniform thickness, each square also has a variable percentage of its area assumed ice free. The model results produce a reasonable yearly cycle of sea ice thickness and extent in both the Arctic and the Antarctic. The arctic ice grows from a minimum in September, when the edge has retreated from most coastlines, to a maximum in March, when the ice has reached well into the Bering Sea, has blocked the north coast of Iceland, and has moved southward of the southernmost tip of Greenland. Maximum arctic thicknesses are close to 4 m. In the Antarctic the ice expands from a minimum in March to a maximum in late August, remaining close to the continent in the former month and extending northward of 60°S in the latter month. Maximum thicknesses are about 1.4 m. The distribution of modeled ice concentrations correctly reveals a more compact ice cover in the northern hemisphere than in the southern hemisphere. Modeled ice velocities obtain both the Beaufort Sea gyre and the Transpolar Drift Stream in the arctic summer as well as the Transpolar and East Greenland Drift streams in the winter. In the Antarctic, simulated velocities reveal predominantly westerly motion north of 58°S, with smaller‐scale cyclonic motions closer to the continent.
A note on the internal solitary waves produced by tidal flow over a three‐dimensional ridge
Authors: Maxworthy T.
Published: April 2008

Using a simple laboratory model we believe that we have clarified the mechanisms whereby a train of solitary waves can be generated by the barotropic tidal flow of a stratified fluid over a three‐dimensional obstacle. As the tidal flow reaches critical value of the internal Froude number a downstream depression is formed in the mixed layer. When the tide slackens and turns, this depression moves upstream and evolves into a sequence of solitary waves. Under some circumstances the depression becomes turbulent, and intense mixing takes place. In this case it is also the collapse of the mixed region that generates solitary waves which mainly propagate upstream. Available field data are consistent with this explanation, and we can estimate the number of waves formed using existing theory.
Nitrous oxide production in the Ocean
Authors: Cohen Yuval , Gordon Louis I.
Published: April 2008

Examination of vertical profiles of N2O, oxygen, and nitrate from the Northeast and Northwest Atlantic, Northeast Pacific and eastern tropical North Pacific reveals a striking consistency in the relationships among them. With the exception of zones of active denitrification, N2O is negatively correlated with oxygen and positively correlated with nitrate throughout the water column and it is, therefore, concluded that N2O production in the ocean is associated with the oxidative regeneration of nitrate. In both the Atlantic and Pacific Oceans, the difference between the measured N2O concentration and its equilibrium solubility is linearly correlated with apparent oxygen utilization and from this relationship and the Redfield plankton decomposition model it is estimated that N2O‐nitrogen comprises about 0.1 to 0.4% of the nitrogen regenerated in the ocean. From the ratio of N2O to nitrate production during nitrate regeneration and estimates of the overall regeneration of nitrate in the ocean, it is concluded that the total marine production of N2O is in the range of 4 to 10 Tg‐N yr−1 (6 to 16 Tg‐N2O yr−1). This estimate is in good agreement with estimates of the N2O loss to the atmosphere derived from N2O measurements at the sea surface.
Dual doppler radar observations of clear air wind perturbations in the planetary boundary layer
Authors: Doviak Richard J. , Jobson Charles T.
Published: April 2008

The National Severe Storm Laboratory's dual Doppler weather radars map clear air planetary boundary layer winds using only the intrinsic scatterers of the medium. Perturbation winds have correlation lengths of a few kilometers on this day of moderate shear and advect with the mean wind. The structure function of wind shows good agreement with the two thirds law of turbulence theory. Reflectivity has a cellular structure with weak echo interiors. Independently measured reflectivity fields have correlations as large as 0.86.
Some properties of em radiation from lightning
Authors: Clegg R. J. , Thomson E. M.
Published: April 2008

Simultaneous records of electrostatic fields and optical and HF (10 MHz) radiation from ground and cloud flashes occurring in Suva, Fiji, have been made, and gaps (brief cessations) in the HF radiation from lightning discharges have been analyzed. Gaps in the HF noise following return strokes appear to be terminated by K changes, the gap duration distribution following closely that of previously observed K change interval distributions. These observations support conjecture that in‐cloud junction streamers, rather than ceasing immediately following a return stroke, proceed from the top of the return stroke channel until a pocket of charge is tapped to produce the K change which terminates the noise gap. The streamer itself is presumed to radiate HF only weakly. Earlier proposals that HF noise gaps of duration greater than a certain length are associated with return strokes and therefore can be used to discriminate, for lightning counting purposes, between cloud‐ground discharges and intracloud discharges are not supported.
Mineral and sea salt aerosol concentrations in various ocean regions
Authors: Prospero J. M.
Published: April 2008

Two hundred and forty six aerosol samples collected in the Atlantic, Pacific and other ocean regions were analyzed for their mineral and sea salt aerosol content. The geometric mean mineral aerosol concentrations over most oceans were low: 0.36 μg m−3 in the central and northern North Atlantic, 0.35 μg m−3 in the Pacific between 30°N and 40°S, and 0.69 μg m−3 in the South Atlantic north of 40°S. The highest mean concentration, 14.2 μgm−3, was obtained in the tropical North Atlantic. High mineral aerosol concentrations were also obtained in the Mediterranean (4.29 μg m−3) and the Indian Ocean (4.76 μg m−3). Thus, arid regions appear to be the principal source of mineral aerosol in the marine atmosphere. In contrast, the sea salt aerosol concentrations are relatively constant from one region to the other with geometric means ranging from 3.34 μg m−3 to 8.71 μg m−3
On heat and mass flux through dry snow
Authors: Palm Enok , Tveitereid Morten
Published: April 2008

The conditions for obtaining thermal convection in dry snow are examined. It is shown that thermal convection will occur in dry snow layers with strong vertical temperature gradients and large air permeabilities (i.e., old snow). Thermal convection will lower the insulating power of the snow and increase the flux of water vapor through the snow layer. The magnitude of the heat and mass flux in convection is computed for several values of the Rayleigh number.
On the internal wave variability during the internal wave experiment (IWEX)
Authors: Frankignoul Claude , Joyce Terrence M.
Published: April 2008

The relation between internal wave variability and larger and smaller scales of motion is investigated, using the IWEX data set. To investigate the role of internal waves in the vertical diffusion of large scale momentum, the time variability of the vertical flux of horizontal internal wave momentum (estimated from temperature and current data) is compared to that of the mean vertical shear. It is found that internal waves cannot cause a vertical viscosity as large as proposed by Müller (1976), but that the data are too noisy to detect a possible wave‐induced viscosity in absolute value of the order of 10−2 m2 s−1 or less. Similarities in the time behavior of the total internal wave energy and that of the square mean vertical shear suggest that some kind of dynamical coupling exists between internal waves and larger scale flows. There is some evidence that the level of temperature finestructure activity also varies in a related way. An analysis of CTD station data taken during Mode demonstrates the mappability of the finestructure activity, and again suggests a relation with the geostrophic eddy flow.
The birth and death of a warm core ring
Authors: Csanady G. T.
Published: April 2008

The birth of a warm core ring is conceptualized as a catastrophic separation process governed by the strong inertial forces within a western boundary current. A frictionless theory based on this postulate and assumed geostrophic balance on completion of the separation process yields a description of ring geometry and velocity distribution in first‐order agreement with observation. In particular, maximum velocities of the order of 1 m s−1 are predicted to occur near the perimeter. The initial decay rate of the ring is estimated from an interface friction and entrainment model (using the above maximum velocity) to be about 0.05 day−1, which reduces rapidly, however, as the ring slows down. Interface friction is found to be much more important than entrainment in producing the decay.
A simple model for the structure of warm and cold core rings
Authors: Flierl Glenn R.
Published: April 2008

We consider the simplest model describing the shape and strength of warm and cold core rings. The model has an upper layer of constant potential vorticity and a lower layer at rest. The Coriolis parameter is taken to be constant. The flows are strong enough so that the interface between the two fluids rises to the surface. We describe the velocity and interface depth profiles and compare the model to field data.
A dynamical analysis of currents near the New Jersey Coast
Authors: Bennett John R. , Magnell Bruce A.
Published: April 2008

A numerical model is used to analyze currents measured on the continental shelf near the shore of New Jersey. The model neglects longshore variations of current and all variations of density, but includes inertial accelerations and a nonlinear eddy viscosity. Local wind stress, sea level changes, and a constant longshore pressure gradient are the forcing terms. The model successfully reproduces most of the current variance; however, the predicted currents do not exhibit the dominant 4‐hour response time of the observed currents, and the model sometimes misses energetic current events. These differences are ascribed to three‐dimensional setup effects elsewhere in the New York Bight.
An experimental study of brine drainage and convection in Young Sea ice
Authors: Niedrauer Terren M. , Martin Seelye
Published: April 2008

In a series of experiments using a 1.6‐mm‐thick freezing tank, thin sections of salt water ice were grown which exhibit the same drainage features as natural sea ice. The tank design permitted photographs to be taken, while thermocouples mounted in the tank walls recorded the temperature profiles within the ice. Convection was observed in both the skeletal layer and in the brine channels by the flow of dyed brine. Flow in the skeletal layer was cusplike in appearance, consisting of narrow downflow regions separated by broad upflow regions. Above the skeletal layer, several brine channels were also usually present in the ice, and convective overturning occurred in these channels. The convection caused temperature fluctuations of 0.05°C, which calculations show increase the vertical heat flux by 1%. The brine drainage channels, which were usually sloped 30° to 60° to the horizontal, always had isotherms tilted from 0° to 13° in the same direction. The brine channels move both horizontally and vertically through the ice by melting their lower walls and freezing on the upper walls. An analysis based on the heat flux due to brine channel convection shows that convection can drive these wall movements. Our observations suggest that most of the brine movement in the channels is caused by recirculation of water from below the ice. On a small scale we also observed the formation of brine pockets from brine tubes.
Tropospheric arsenic over marine and continental regions
Authors: Walsh Paul R. , Duce Robert A. , Fasching James L.
Published: April 2008

Particulate and vapor concentrations of atmospheric as have been measured over various marine and continental areas. Particulate samples were collected on double Whatman 41 filters. Particulate‐vapor samples were collected using an in‐line filter system with a 0.45‐μm pore size Nuclepore filter as a particle prefilter in front of two Whatman 41 filters impregnated with tetrabutylammonium hydroxide and glycerol for vapor As collection. Arsenic determinations were by destructive neutron activation. The data from the Nuclepore‐impregnated filter samples indicates that the major fraction of As in the atmosphere is particulate but a vapor component of As is detectable, most frequently associated with high sampling temperatures and high total As concentrations. With the data presented here, estimates of representative global near‐surface concentrations of atmospheric arsenic have been made.
The atmospheric nuclear tests of the 1950's and 1960's: A possible test of ozone depletion theories
Authors: Chang Julius S. , Duewer William H. , Wuebbles Donald J.
Published: April 2008

It will be shown that the model chemistries used to calculate the effects of supersonic transports for Climatic Impact Assessment Program (Grobecker et al., 1975) and National Research Council (1975a) studies and of large‐scale nuclear exchanges for National Research Council (1975b) studies cause our one‐dimensional model to predict ozone depletions in 1963–1964 resulting from NOx injected into the stratosphere by the atmosphere nuclear tests of 1956–1962 larger (4–14% ozone reduction in 1963) than is easily consistent with observation. However, calculations carried out with more recent model chemistries result in ozone reductions that are more easily consistent with observation.
Umkehr vertical ozone profile errors caused by the presence of stratospheric aerosols
Authors: DeLuisi John J.
Published: April 2008

The unusually large increase in stratospheric aerosol concentration resulting from the eruption of Agung in 1963 is shown to produce fictitious anomalies in the record of vertical ozone profiles determined from Umkehr observations at Aspendale, Australia. The anomalies are of sufficient magnitude that an empirical haze error to the profiles can be extracted from a comparison between seasonal averages of ozone profiles observed shortly after the Agung event and ozone profiles observed during periods of volcanic quiescence. Haze errors to the ozone profiles are also theoretically calculated for various models of vertical profiles of aerosols, ranging from relatively large concentrations of tropospheric aerosols to large concentrations located exclusively in the stratosphere. It is shown that the theoretically determined haze errors are essentially of the same character as those determined empirically. Haze error corrections are applied to a long‐term Umkehr record of north temperate upper stratospheric ozone concentration following Agung. The results imply that the anomalously low ozone concentrations in the upper stratosphere, noted after the eruption of Agung and Fuego in 1974, may not be real.
Stratospheric heterogeneous decomposition of ozone
Authors: Olszyna Kenneth , Cadle Richard D. , dePena Rosa G.
Published: April 2008

The heterogeneous decomposition of ozone at −50°C, on surfaces coated with 75% sulfuric acid solutions and with 75% sulfuric acid solutions containing a variety of metallic ions and NH4+, has been studied in a static system. The collision efficiency γ (the ratio of the number of reactive collisions to the total number of collisions) for the reaction on each surface has been determined. It was found that the addition of the ions Ni2+, Cu2+, Al3+, Fe3+, and NH4+ did not appreciably modify the reaction rate observed over clean glass or glass coated with the sulfuric acid solution. Mn2+ and Fe2+ did enhance the reaction but only by 2 orders of magnitude for the last ion. However, the largest value of γ observed, 10−9, is still too small to be of any significance in the stratosphere. We conclude that the heterogeneous decomposition of ozone on the stratospheric particle surfaces is of minor importance.
The deformation of pack ice by ridging
Authors: Bugden G. L.
Published: April 2008

Some ideas on modeling the deformation of pack ice by ridging are presented. A theory is proposed which, by assuming a constant shape for ridge sections and coupling the ridge frequency to the mean ridge height, provides a thickness redistribution function related to previously developed statistical ridge models.
The transport and resuspension of sediments in a shallow lake
Authors: Sheng Y. Peter , Lick W.
Published: April 2008

The time‐dependent flow and dispersion of suspended sediments in the western basin of Lake Erie are being studied by means of numerical models utilizing data from remote‐sensing studies and flume experiments. Mechanisms of sediment dispersion included in the models are convection and turbulent diffusion, river loading, gravitational settling, and physical resuspension and deposition at the sediment‐water interface. The time‐dependent currents are computed by means of a free surface hydrodynamic model. A wave‐hindcasting model is used to compute the wave parameters needed for estimation of shear stress generated at the sediment‐water interface under given wind conditions. The rate of sediment resuspension as a function of bottom shear stress and sediment properties is based on data from flume experiments using lake sediments. A series of numerical calculations with the models were performed on a two‐dimensional lake with a variable bottom representing a transverse cross section of Lake Erie. It was found that wind direction and fetch length can significantly affect the sediment dispersion patterns. The two‐dimensional and the three‐dimensional models were both used to simulate realistic short‐term events in Lake Erie, and the model outputs compare favorably with the synoptic surface sediment dispersion patterns deduced from the multispectral scanner data.
Parameterization of the thermal relaxation rate in the stratosphere
Authors: Strobel Darrell F.
Published: April 2008

The thermal relaxation rate of large vertical scale disturbances in the stratosphere is parameterized in terms of the Newtonian cooling rate, the heating rate, and a transmission function that represents opacity effects.
Radon evasion rates in the Atlantic and Pacific oceans as determined during the Geosecs Program
Authors: Peng T.‐H. , Broecker W. S. , Mathieu G. G. , Li Y.‐H. , Bainbridge A. E.
Published: April 2008

During the Geosecs expedition in the Atlantic and the Pacific oceans, more than 100 stations were occupied for the measurement of surface radon profiles. The radon deficiency in these profiles gives estimates of the gas transfer rate across the sea‐air interface. The global mean transfer rate is estimated to be 2.9 m/d (at 20°C) which is corresponding to a hypothetical stagnant film thickness of about 36 microns. No clear relationship can be found between the gas exchange rate and wind speed. The CO2 exchange rate as determined by the radon method is 80% of that given by the distributions of natural and of bomb‐produced radiocarbon. One possible explanation may be that the Geosecs radon measurements were made during periods of lower than average wind speed. Another is that the conversion of CO2 to HCO3− is catalyzed within the sea.
On the statistical distribution of pressure ridges in sea ice
Authors: Lowry R. T. , Wadhams P.
Published: April 2008

Probability distributions for the heights and spacings of sea ice pressure ridges are described and compared with data from airborne laser profiles and submarine sonar profiles. The distributions are based on the variational calculations of Hibler et al. (1972) but take into account the effects of finite slope angles of ridges and of the criterion used to identify an independent ridge during computer reduction of data. The modified distributions are shown to give a much better fit for small ridge spacings and slightly better fit for small ridge heights than the 1972 theory.
A water mass model of the World Ocean
Authors: Bryan K. , Lewis L. J.
Published: April 2008

A numerical model of the world ocean is developed to investigate the role of the ocean in the earth's heat balance. Climatological wind stress, temperature, and salinity are imposed as upper boundary conditions. An equilibrium solution is obtained based on an extended numerical integration over the equivalent of 1000 years. Seasonal variations are included. A series of numerical integrations over shorter periods indicate that quantitative aspects, such as the scale depth of the thermocline, are very sensitive to the closure parameterization representing the effect of unresolved scales of motion. The mean depth of the thermocline is found to be in proportion to the global available potential energy. Larger wind driving increases the scale depth of the thermocline, while larger lateral friction or diffusion leads to a shallower thermocline. The model predicts three major meridional cells in the upper thermocline in each hemisphere, corresponding to the three meridional cells of the atmosphere. The tropical and mid‐latitude cells are largely wind driven. Thermohaline effects are dominant in the polar meridional cells. Seasonal changes in winds have a profound effect on the meridional circulation in the tropics and cause a flux of surface water from the summer to the winter hemisphere. It is suggested that this mechanism is an important factor in moderating climate by transferring excess heat from the summer hemisphere into the winter hemisphere.
A Kelvin wave in the eastern North Pacific Ocean
Authors: Platzman George W.
Published: April 2008

Among the normal modes calculated in a barotropic model of the world ocean is a Kelvin‐like wave on the west coast of North America, whose period is 15.6 hours. On the California coast this wave has a phase speed of about 140 m s−1. If its amplitude is scaled to 50 cm at La Jolla (the M2 tide there), the 15.6‐hour mode has a stored energy of 1.7×1017 J, about one fourth the global energy of the M2 tide. With the same scaling the power of the wave is between 3×1011and 4×1011 W. The possibility is discussed that this mode is an important element of the M2 tide, but definite conclusions require a complete modal synthesis which has not yet been made.
Inferences drawn from atmospheric CO2 data
Authors: Rust Bert W. , Rotty Ralph M. , Marland Gregg
Published: April 2008

Detailed analyses of the atmospheric carbon dioxide concentration measurements from Mauna Loa Observatory have produced a model which describes most of the variability in the data. The final model is y(t) = a + deαt + Σi = 1 2Aisin[(2π/Ti)(t + ϕi)] + Σj = 12Fj sin[(2π/τj)(t + Θj)], where a is the preindustrial value, α is the exponential long‐term growth rate, i represents the annual cycle and its harmonics, and j represents longer‐term periodicities. The exponential growth rate is nearly identical to that calculated for the production of CO2 from fossil fuel burning. A long‐period component of about 44 months correlates with the southern oscillation index. Another long‐period oscillation—about 142 months—has tentatively been identified with the solar activity cycle and complicates the determination of α because the two sources of curvature interact in the fitting procedure, and the data record is not long enough to specify both of them independently. The generality of the model has been demonstrated by testing it against shorter data sequences from the South Pole and Australia.
Turbulent air‐water mass transfer under varied stratification conditions
Authors: Resch F. J. , Selva J. P.
Published: April 2008

Influence of neutral, stable, and unstable stratification conditions upon turbulent momentum, heat, and mass transfers is shown. Velocity, temperature, and humidity profiles have been recorded for various global Richardson numbers in the large IMST air‐sea interaction simulating facility. Corresponding fluxes and dimensionless exchange coefficients are estimated by indirect methods, and their variations with Reynolds and bulk Richardson number are found. The shape of humidity profiles appears to be affected by stratification, as should be expected from the Monin‐Obukhov semiempirical theory. Results obtained by the various techniques show good internal agreement, and they are compared with both theory and previous experimental results. A semi‐empirical relationship between the Sherwood (Sh) and both the Reynolds numbers (Re) based on fetch and the bulk Richardson number (Rig) is proposed: Sh = · 0073 Re0.9 (1 ‐ 17 Rig).