bluuebunny/crossref_metadata_2025 huggingface dataset:
Southern hemisphere western boundary current variability revealed by GEOS 3 altimeter
Authors: Gordon Arnold L. , Horai Ki‐iti , Donn Matthew
Published: February 2008

GEOS 3 altimeter data are adjusted to minimize differences at the intersections or crossovers between ascending and descending orbits. This procedure removes noise created by orbital uncertainty and permits study of sea level variations without knowledge of the geoid. The root mean squares (rms) of the adjusted differences, grouped within 2° latitude by 2° longitude boxes, are mapped for the western boundary current regime and adjacent Antarctic Circumpolar Current segment for each southern hemisphere ocean, as well as for the eastern Indian Ocean, where sufficient crossover data are available. The rms crossover values are compared to surface‐based hydrographic data studies of ocean transients for verification of the altimeter results. The altimeter data clearly reveal reasonable patterns of sea level transients associated with the western boundary currents and Antarctic Circumpolar Current. In addition, the rms values reveal regions of locally amplified tidal features adjacent to the Patagonian coast of Argentina and in the region west of New Zealand. The altimeter data verify and expand on the results of limited surface‐based data sets, particularly in the case of the circulation transients south of Madagascar, and southwest of New Caledonia. In the eastern Indian Ocean the altimeter data suggest variable sea level conditions near 10°–20°S, near 20°–30°S, and near 50°S. The last is associated with the Antarctic Circumpolar Current, but the source of the northern variable regions is not clear.
Preliminary study of CO2 variations at Amsterdam Island (Territoire des Terres Australes et Antarctiques Francaises)
Authors: Gaudry A. , Ascencio J. M. , Lambert G.
Published: February 2008

The preliminary measurements of atmospheric CO2 concentrations performed at Amsterdam Island between April and the end of 1980 showed two kinds of short‐term variations. The first one, attributed to local effects of the photosynthesis of the island vegetation, does not seem considerably to affect the monthly mean CO2 concentrations. The second one has been attributed to long range transport phenomena. That corresponds to large scale meteorological perturbations and generally is correlated with variations of the atmospheric radon concentrations. Therefore, the existence of regional CO2 sources and sinks in the southern hemisphere can be felt at a very large distance. Consequently, isolated measurements of geographical gradients, could correspond to a transitory situation and should not be utilized for the determination of these sources and sinks.
Tropospheric NOx and O3 budgets in the equatorial Pacific
Authors: Liu S. C. , McFarland M. , Kley D. , Zafiriou O. , Huebert B.
Published: February 2008

By combining the results of model calculations and simultaneous measurements of O3, NO, HNO3, particulate NO3−, and meteorological parameters in the mid‐Pacific, we have investigated the budget and photochemistry of near surface atmospheric ozone and odd nitrogen. The observed decrease of O3 toward the Intertropical Convergence Zone is consistent with the transport of O3 from higher latitude and a photochemical sink for O3 by the reaction between H2O and O(1D). The total deposition flux of odd nitrogen deduced from the data is about 1.3×109 cm−2 s−1, or 5 MT(N)/yr averaged globally. Most of the deposition flux is due to HNO3 and particulate NO3−. This deposition flux is probably representative of values over most of the Pacific because the HNO3 and particulate NO3− densities measured over the Pacific during the GAMETAG experiments are consistent with our values. Since the residence time of odd nitrogen in the lower troposphere is short, a widely distributed, diffuse source of odd nitrogen is required to balance the deposition flux. It seems that the NO formed by cloud to cloud lightning in the tropical upper troposphere is the most likely source.
The measurement of the synoptic scale wind over the ocean
Authors: Pierson Willard J.
Published: February 2008

Mesoscale and microscale features of the turbulent winds over the ocean are related to the synoptic xscale winds in terms of published spectral forms for the microscale, a mesoscale valley, and published values of u*, Var u′, Var v′, and z/L, as defined in the text and as obtained for moderate to gale force winds. The frequencies involved correspond to periods longer than 1 hour and extend to the microscale, which starts at a period near 2 min, or so, and continues to the Kolmogorov inertial range. Nondimensional spectra that span both the mesoscale and the microscale are derived as a function of u*,f/(=nz/ū), and z/L, where z is 10 m, L is the Monin‐Obukhov stability length, and ū is evaluated at 10 m. For the same ū, different values of z/L produce a range of values of u* which in turn result in variations of the eddy structure of the mesoscale and microscale spectra. Both conventional anemometer averages and remotely sensed winds contain a random component of the mesoscale wind in their values. These components are differences and not ‘errors’ when winds are compared, and quantitative values for these differences are given. Ways to improve the measurement of the synoptic scale wind by transient ships, data buoys, and scatterometers on future spacecraft are described. These ways are longer averaging times for ships and data buoys, depending on the synoptic conditions, and pooling spacecraft data to form superobservations. Design considerations for future remote sensing systems are given.
Unusual behavior in the condensation nuclei concentration at 30 km
Authors: Rosen J. M. , Hofmann D. J.
Published: February 2008

The results obtained with an improved balloon‐borne condensation nuclei (cn) counter that is capable of operating to altitudes of at least 30 km are presented. Of major interest is the appearance of a quasiannual variation near 30 km which could be described by a sudden concentration increase of unusually small particles occurring in the winter or spring followed by a 1‐ to 3‐month decay period to background levels. The magnitude of the variation has increased dramatically following the recent generally higher levels of volcanic activity affecting the lower stratosphere. Several potential explanations for the event are considered, but none appear entirely satisfactory or complete at the present time. The explanation with the fewest drawbacks would attribute the production of growth of the new cn to a highly supersaturated H2SO4 vapor layer generated by any one of several proposed processes in the upper high latitude stratosphere.
Stratospheric water vapor
Authors: Ellsaesser Hugh W.
Published: February 2008

We present a tutorial review of our understanding of stratospheric H2O and the processes controlling it. We attempt to synthesize a consistent global picture that requires rejection of a minimum of the conflicting observational data. As such, this synthesis is determined somewhat by the personal opinions and beliefs of the author. We note the paradoxes posed by currently available observational data and suggest ways they might be resolved. Resolution of the stratospheric H2O budget appears to require (1) either that the bulk of our current data provides unrepresentative and misleading latitudinal H2O gradients immediately downstream from the presumed tropical tropopause source of H2O or that there are unidentified polar stratospheric sinks for H2O; (2) that it also provides an unrepresentative vertical gradient in H2O immediately above the tropical tropopause source or that there is a stratospheric sink for H2O in this region; or (3) that there exist within the troposphere a mechanism different from or in addition to the tropical tropopause ‘cold trap’ for drying air to the mixing ratios found in the lower stratosphere. Satisfaction of conditions such as these are required to reconcile a rather large mass of puzzling observational data. Satisfaction of the third option would also permit tropospheric to stratospheric exchange through the mid‐latitude tropopause gaps, a path suggested by minima in O3 profiles.
Eddy kinetic energy in the North Atlantic from surface drifters
Authors: Richardson Philip L.
Published: February 2008

One hundred ten satellite‐tracked freely drifting buoys measured velocities and trajectories of the near‐surface currents in the North Atlantic. Mean velocity values and the velocity variance about the mean were calculated for different regions. A horizontal map of eddy kinetic energy was prepared on a 2°×2° grid between latitudes 20° and 55°N. Maximum eddy energy (∼3000 cm2 s−2) coincides with the high speed Gulf Stream jet where it begins large amplitude meanders near 37°N 67°W. A tongue of high eddy energy coincides with the Stream's path eastward and around the Grand Banks into the Newfoundland Basin where values of 1000 cm2 s−2 are found. A weaker tongue extends eastward across the mid‐Atlantic Ridge near 45°N. A second weak extension reaches southeastward from the Stream and crosses the mid‐Atlantic Ridge between 30° and 35°N. North and south of the Stream, eddy energy diminishes rapidly reaching an e folding at 300 km from the axis. Values of 200 cm2 s−2 were observed in the mid‐gyre region and 100 cm2 s−2 in the Eastern North Atlantic and North Equatorial Current. Although the gross distribution of eddy energy is similar to that determined from ship drift measurements, there are significant differences. Eddy energy from drifters amounts to about twice the value measured by ship drift in the Gulf Stream and one half the ship drift values in the mid‐gyre. It is suggested that these differences are due to the horizontal averaging of mesoscale motion and the errors in navigation, both of which are problems with the ship drift technique.
Wave‐current interactions on a slowly varying topography
Authors: Liu Philip L‐F.
Published: February 2008

A parabolic approximation formulation is presented herein to study the wave‐current interactions on a slowly varying topography. Model equations are first derived from the mild‐slope assumption. A parabolic approximation is then applied to convert a boundary value problem to an initial value problem. Several limiting cases are discussed. Numerical examples are given for the case concerning the interactions between jet‐like currents and normal incident waves on a sloping beach (Arthur, 1950).
10Be and Be in the Maurice River‐Union Lake system of southern New Jersey
Authors: Lundberg L. , Ticich T. , Herzog G. F. , Hughes T. , Ashley G. , Moniot R. K. , Tuniz C. , Kruse T. , Savin W.
Published: February 2008

The 10Be and Be contents of 22 samples taken from seven locations in the Maurice River‐Union Lake system of southern New Jersey are reported. Bulk 10Be contents range from 0.05 to 2.7 dpm/kg and Be from <0.1 to 2 ppm. Silicate minerals separated from Union Lake sediments appear to have a constant surface concentration of ∼5 × 105 atom 10Be/cm2. Organic material is greatly enriched in Be: Hand‐picked samples contain over 10 dpm/kg of 10Be and 5 ppm of Be. The deposition rate of l0Be in Union Lake is ∼1 atom/cm2s.
Atmospheric trace elements at Enewetak Atoll: 1. Concentrations, sources, and temporal variability
Authors: Duce R. A. , Arimoto R. , Ray B. J. , Unni C. K. , Harder P. J.
Published: February 2008

The concentrations of 29 elements were measured in aerosol particles collected in 1979 during SEAREX experiments at Enewetak Atoll (11°N, 162°E) in the tropical North Pacific. The concentrations of Na, Mg, Cl, K, Ca, and Br were dominated by marine sources; these elements had similar mass‐size distributions, and their atmospheric concentration ratios (normalized to Na) were similar to the corresponding ratios in bulk seawater. Atmospheric inputs of aluminosilicate particles from crustal weathering controlled the aerosol particle concentrations of Al, Sc, Mn, Fe, Co, Cs, Ba, Ce, Eu, Hf, Ta, and Th. Mean concentrations of these crustally derived elements decreased by an average of 91% (±4.1%) from the local dry season (April to May) to the wet season (July to August); this general decrease was attributed to the abatement of dust storms in Asia. At times the influx of dust from Asia dominated the concentrations of V, Cr, Rb, and Cu in aerosol particles, but when dust concentrations decreased, noncrustal sources for these elements became apparent. A fourth group of elements (Zn, Se, Ag, Cd, Sb, I, and Pb) exhibited average, atmospheric concentrations that were higher than those expected from the flux of sea salt or the dispersal of mineral aerosol particles. Enrichments of these trace elements relative to average crustal material increased as the atmospheric dust concentrations subsided. Supplement is available with entire article on microfiche. Order from American Geophysical Union, 2000 Florida Avenue, N.W., Washington, D.C. 20009. Document C83‐001; $2.50. Payment must accompany order.
The solar absolute spectral irradiance 1150–3173 Å: May 17, 1982
Authors: Mount George H. , Rottman Gary J.
Published: February 2008

The full‐disk solar spectral irradiance in the spectral range 1150–3173 Å was obtained from a rocket observation above White Sands Missile Range, New Mexico, on May 17, 1982, halfway in time between solar maximum and solar minimum. Comparison with measurements made during solar maximum in 1980 indicate a large decrease in the absolute solar irradiance at wavelengths below 1900 Å to approximately solar minimum values. No change above 1900 Å from solar maximum to this flight was observed to within the errors of the measurements. We find irradiance values lower than the Broadfoot results in the 2100–2500 Å spectral range, but we find excellent agreement with Broadfoot between 2500 and 3173 Å. The absolute calibration of the instruments for this flight was accomplished at the National Bureau of Standards Synchrotron Radiation Facility which significantly improves calibration of solar measurements made in this spectral region.
Near‐inertial motions off the Oregon Coast
Authors: Anderson Iain , Huyer Adriana , Smith Robert L.
Published: February 2008

Near‐inertial motions were observed at all current meters in an array of five moorings spanning the continental margin off central Oregon during October 1977 to January 1978. All moorings were between 10 and 130 km from shore, in water depths between 100 m and 2500 m. Largest near‐inertial amplitudes (>30 cm/s) were observed at the uppermost current meters of the offshore moorings, although these were below the surface mixed layer. The near‐inertial energy generally decreased with increasing depth, and there was less near‐inertial energy over the continental shelf than at similar depths offshore. The energy levels observed over the shelf were about the same as observed there during summer 1973, and the energy levels observed offshore were comparable with those observed in the open North Atlantic. Horizontal coherence scales were large, exceeding 115 km during the first half of the observational period and about 60 km during the second half; estimates of the horizontal wavelength (50 km during the first half and 20 km during the second half) suggest that the coherence scale is of the order of three wavelengths. Although we did not have current data in the surface mixed layer nor wind measurements over each mooring, the available meteorological data (synoptic pressure charts and hourly wind and pressure at Newport) suggest that most of the near‐inertial energy was forced by the local wind.
Equilibration times for reversing thermometers
Authors: De Visser Alexandra M. , Hodgson Robert T.
Published: February 2008

The proper relaxation time necessary before reading deep sea reversing thermometers depends on the time constants of the main and auxiliary thermometers. In a computer simulation, the maximum error in corrected water temperatures is centered at a lag time equal to the average of the time constants, while the magnitude of the error is proportional to the difference in time constants. For the thermometers we tested, a maximum error of 0.03°C was incurred by prematurely reading deep sea reversing thermometers.
A non‐Gaussian statistical model for surface elevation of nonlinear random wave fields
Authors: Huang Norden E. , Long Steven R. , Tung Chi‐Chao , Yuan Yeli , Bliven Larry F.
Published: February 2008

Probability density function of the surface elevation of a nonlinear random wave field is obtained. The wave model is based on the Stokes expansion carried to the third order for both deep water waves and waves in finite depth. The amplitude and phase of the first‐order component of the Stokes wave are assumed to be Rayleigh and uniformly distributed and slowly varying, respectively. The probability density function for the deep water case was found to depend on two parameters: the root‐mean‐square surface elevation and the significant slope. For water of finite depth, an additional parameter, the nondimensional depth, is also required. An important difference between the present result and the Gram‐Charlier representation is that the present probability density functions are always nonnegative. It is also found that the ‘constant’ term in the Stokes expansion, usually neglected in deterministic studies, plays an important role in determining the details of the density function. The results compare well with laboratory and field experiment data.
Wind measurements from an array of oceanographic moorings and from F/S Meteor during JASIN 1978
Authors: Weller Robert A. , Payne Richard E. , Large W. G. , Zenk Walter
Published: February 2008

During the Joint Air‐Sea Interaction (JASIN) experiment conducted in the northern Rockall Trough in the summer of 1978, oceanographic moorings with surface buoys carrying wind recorders were deployed in an array designed to investigate the variability of the near‐surface wind field at scales of from 2 to 200 km. The wind records together with observations taken on board the research vessels participating in JASIN have provided ground truth measurements for the sea surface wind velocity sensors on the Seasat satellite. During most of the experiment the wind field was characterized by spatial scales large in comparison with the separations between the buoys. On several occasions, spatial differences associated with cold fronts were identified, and it was possible to track the passage of the front through the array. However, quantitative analysis of the variability of the wind field was complicated both by a lack of data due to mechanical failures of some instruments and by significant differences in the performance of the diverse types of wind recorders. Reevaluation of the instruments used in JASIN and recent comparison of some of these instruments with more conventional sets of wind sensors confirm the possibility that there is significant error in the JASIN wind measurements made from the buoys. In particular, the vector‐averaging wind recorder on W2, which was one of the few instruments to recover a full length record and which was chosen during a Seasat‐JASIN workshop as the JASIN standard, had performance characteristics that were among the most difficult to explain.
Theory and validation of the multiple window sea surface temperature technique
Authors: McMillin L. M. , Crosby D. S.
Published: February 2008

The development of the “split window” approach for correcting satellite measurement of radiance for atmospheric attenuation is reviewed. Then the theoretical results are compared to results from actual measurements which consist of satellite measurements in the three infrared windows of the AVHRR. Ground truth for the comparisons comes from buoys. The satellite measurements were screened for clouds, and the remaining ones were used in the analysis. Using this data set, several statistical analyses were performed. These showed that, when the two channels that are truly a split window are used, the result of the statistical model agrees with the one derived from theoretical considerations. When the 3.8‐μm channel is combined with one in the 10–12 μm region, the result of the statistical model does not take the split window form. Results show that the method is capable of producing sea surface temperatures with a standard deviation of 1 K or less.
Coastal temperature and salinity in the northern Gulf of Alaska, 1970–1983
Authors: Xiong Qingcheng , Royer Thomas C.
Published: February 2008

Analysis of the time series of the temperature and salinity in the northern Gulf of Alaska from December 1970 to September 1983 shows annual signals in water properties with warm, low‐salinity surface water in summer and cold, high‐salinity surface water in late winter. The mean surface temperature and salinity were 11.5°C and 27.33‰ in summer and 4.3°C and 31.16‰ in winter. Over the nearly 13‐year observational period the surface temperature range was from 2° to 14%C and the surface salinity range was 26 to 31.5‰. Abnormal warming throughout the water column was evident in 1976–1977 and 1983. These thermal features appear to be caused by advection, rather than local effects. The salinity anomalies in the upper 50 m are primarily correlated with freshwater discharge and secondarily with wind stress.
Influence of the oceanic scattering phase function on the radiance
Authors: Plass Gilbert N. , Kattawar George W. , Humphreys Terry J.
Published: February 2008

Accurate model calculations are made by the matrix operator method of the radiance of the atmosphere‐ocean system. The purpose of these calculations is to show that the shape of the scattering phase function can influence the radiance values. Three different phase functions are used in the calculations: two of these are realistic for the oceans, whereas the third is introduced to help understand the effect of the shape of these functions. All three functions have the same backscattering coefficient. The up welling radiance ratio for the two realistic phase functions can be greater than 3 just above the ocean surface and larger than 2 at the top of the atmosphere. We have also calculated the irradiances just above and just below the ocean‐air interface. The results show that the simple one‐dimensional model can be in error by at least 30% for realistic ocean volume scattering functions having the same backscattering coefficient.
Techniques for precise mapping of 226Ra and 228Ra in the ocean
Authors: Moore Willard S. , Key Robert M. , Sarmiento Jorge L.
Published: February 2008

Improvements in the analyses of 226Ra and 228Ra in seawater made possible by better extraction and processing techniques reduce significantly the errors associated with these measurements. These improvements and the extensive sampling for Ra isotopes conducted on the TTO North Atlantic Study should enable us to use the distribution of 228Ra to study mixing processes on a 3–15 year time scale in both the upper and deep North Atlantic. The 228Ra profiles already analyzed show a closer resemblance to GEOSECS tritium data than to TTO tritium data in the upper ocean. This is because the transient tracer tritium was responding on a 10‐year time scale during GEOSECS and a 20‐year time scale during TTO. The steady state tracer 228Ra should always respond on a time scale of 8 years. Thus the 228Ra data obtained on TTO should provide a means to extend the features of the GEOSECS tritium field to the regions of the TTO study. The 226Ra data are of high enough quality to identify features associated with different water masses. Changes in the positions of the deep‐water masses since the GEOSECS cruise are revealed by the 226Radata.
Turbulent flows over a wavy bed
Authors: Kobayashi Nobuhisa , Madsen Ole Secher
Published: February 2008

A hydrodynamic model is developed for the calculation of shear stress and pressure along a sinusoidal boundary that is fixed or propagating very slowly in a wide rectangular open or closed channel. The model uses curvilinear coordinates that follow the wavy boundary, and it is similar to that for two‐dimensional wavy boundary flows of infinite extent proposed by Benjamin (1959), except that the present model takes account of turbulent stresses on the basis of the turbulent eddy viscosity concept employed by Hussain and Reynolds (1970). The compact analytical expressions for the perturbed shear stress and pressure on the wavy boundary are derived for the cases of hydraulically smooth turbulent and fully rough turbulent flows. The developed model is shown to be in good agreement with the experiments conducted by Zilker et al. (1977). The developed hydrodynamic model is applied to the problem of the formation of ripples in erodible channels by Kobayashi and Madsen (1985).
Hydraulic control of flow over the sill in Observatory Inlet
Authors: Farmer David M. , Denton Richard A.
Published: February 2008

Observations of density, velocity, and acoustic backscatter obtained over the sill in Observatory Inlet, British Columbia, during the ebb tide illustrate several features of internal hydraulic control in a tidally forced stratified flow. Following high water slack, the flow field was initially determined by critical control of the second internal mode at the sill crest. As the flow speed increased, a transition occurred, and control changed to an “approach control” of the second internal mode located upstream of the sill crest. Whereas the critical control represents a minimum energy condition at the crest, the approach control corresponds to a maximum energy condition upstream of the sill crest. Later, when the ebb currents were just past their maximum values, the control condition changed to critical control of the first internal mode. The concept of approach control of flow over topography has not previously been discussed in the literature. The data described here are believed to represent the first field observations of this phenomenon. The changing hydraulic conditions are analyzed in terms of two‐ and three‐layer hydraulic models. Model results are consistent with the evolution of the flow patterns, although the model cannot reproduce the apparent hysteresis in the response after maximum ebb. The concept of an approach control is demonstrated with a simple two‐layer laboratory model.
Sampling strategies and model assimilation of altimetric data for ocean monitoring and prediction
Authors: Kindle John C.
Published: February 2008

Numerical forecasts using simulated altimeter data are generated in order to examine the assimilation of altimeter‐derived sea surface heights into numerical ocean circulation models. A one‐layer reduced gravity primitive equation circulation model of the Gulf of Mexico is utilized; the Gulf of Mexico is chosen because of its amenability to modeling and the ability of low vertical mode models to reproduce many of the observed dynamical features of gulf circulation. The simulated data are obtained by flying a hypothetical altimeter over the model ocean and sampling the model sea surface in a manner similar to a real altimeter. The data are used to examine spatial sampling requirements for accurate resolution of oceanic eddies and, in forecast mode, the assimilation of asynoptic altimeter data into numerical models. Results indicate that for a stationary circular eddy, approximately two tracks (either ascending or descending) across the eddy are sufficient to ensure adequate spatial resolution. An irregularly shaped eddy may require three or four tracks. In addition, the study reveals that if the track spacing is sufficient to resolve the height field of an eddy, the along‐track geostrophic velocity component is determined with equivalent accuracy to that of the cross track component. Simulated Gulf of Mexico circulation forecasts suggest that the numerical model can effectively assimilate asynoptic altimeter measurements. Optimum sampling strategies for a single beam altimeter and intermittent updating of the nowcast/forecast are examined.
A calibration diagram of specific beam attenuation
Authors: Spinrad Richard W.
Published: February 2008

A diagram has been developed to demonstrate the response of the beam attenuation coefficient per unit volume (termed the specific beam attenuation coefficient) to changes in particulate size distribution and refractive index. Upon examination, the diagram accurately predicts the optical behavior of particulate samples measured by previous researchers. With estimates of the particle refractive index and size distribution, the diagram provides a higher degree of resolution than was previously assumed in using light transmission measurement to determine the volume of suspended particulate matter.
Measurement of the ocean wave‐radar modulation transfer function at 35 GHz from a sea‐based platform in the North Sea
Authors: Feindt F. , Schröter J. , Alpers W.
Published: February 2008

The ocean wave‐radar modulation transfer function (MTF) at 35 GHz (Ka band) was measured with a coherent pulsed Doppler scatterometer from a research platform in the North Sea. The Bragg waves corresponding to this radar freqency at intermediate incidence angles are capillary waves with a wavelength of about 0.5 cm. During the experiment the air‐sea temperature varied between −1°C and −5°C, which implies that the boundary layer at the air‐sea interface was unstable. The measurements at 35 GHz yield the following results: The modulus of the dimensionless MTF decreases with increasing wind speed and is larger for horizontal (HH) than for vertical (VV) polarization. The value of the dimensionless MTF for HH polarization varies between 3.5 and 9.5 in the frequency range between 0.11 and 0.14 Hz, and that for VV polarization varies between 2.5 and 7.5 depending on wind speed. The phase of the MTF for HH polarization is such that the maximum of the radar return originates from the leeward (forward) face of the long ocean waves between 0° and 15° away from the wave crests. The phase of MTF for VV polarization lies between −75° and −30°, which means that the maximum of the radar return originates from the windward (rear) face of the long ocean waves. We conclude that the phase dependence of the Ka band MTF implies that the maximum of the hydrodynamic modulation for these capillary waves occurs at the windward face of the long ocean waves. The nonuniform distribution of the 0.5‐cm waves with respect to the long ocean wave profile is probably caused by a wave‐induced spatially variable air flow.
Scavenging of thorium in the ocean
Authors: Nozaki Yoshiyuki , Yang Hang‐Soeb , Yamada Masatoshi
Published: February 2008

The distributions of Th isotopes in both suspended participate matter and sea water were measured in the western North Pacific and Japan Sea. Suspended particulate matter was collected simultaneously on four 142‐mm‐diameter Nuclepore filters (1.0 μm in pore size) by using an in situ deep‐sea pumping system. Particle associations were found to be 6–40% for 228Th, 9–52% for 230Th, and 9–72% for 232Th with mean values of 26–32% for all three isotopes. In order to explain the observed Th isotope distributions in the Pacific, a reversible exchange model was developed that includes two classes (fine and large) of particle population in the ocean. The fine particles are defined as those collected by filtration and comprising most of the standing crop of particles in seawater with no significant settling flux. The large particles, on the other hand, are defined as those collected via sediment traps and represent a negligible standing stock in the water but play a predominant role in the vertical flux. The model calculation suggests that the transfer of Th from solution to fine particles is controlled by an adsorption/desorption process which depends upon the chemical reactivity of elements. Aggregation of fine particles to fast sinking large particles was estimated to occur throughout the water column on a time scale of one to five months. The large aggregates seem to disintegrate on a time scale of less than a few days, suggesting their extremely fragile nature.
Seasonal response of the sea surface to the wind in the equatorial Atlantic
Authors: Katz Eli Joel
Published: February 2008

From February 1983 through September 1984, 18 inverted echo sounder deployments yielded time series from 10 locations as part of the Seasonal Response of the Equatorial Atlantic (SEQUAL) program. Using historical and in situ data, the sounders' travel time data are interpreted as dynamic height (0 relative to 500 dbar) and then related to representations of the synoptic wind field. The seasonal variations of the zonal pressure gradient along the equator and the height of the dynamic ridge along 3°N relative to the equator and 9°N are described. The pressure gradient between 10°W and 34°W has a minimum each April and a maximum each July. Its value ranges between 1.4 (not significantly different from zero) and 8.3 × 10−5 dyn g−1 during the observational period. The zonal pressure gradient is correlated with zonal wind stress from an in situ wind sensor at midfetch, and a 10‐day lag time is indicated. The North Equatorial Countercurrent trough attains a maximum in the late boreal summer and fall and a minimum in the spring. It ranges from +39 to −8 dyn cm deep at 38.5°W and from 18 to −1 dyn cm at 28°W. A two‐layer model calculation, using monthly mean winds derived by Servain et al. (1986) for the appropriate time period, generally reproduces the observed seasonal variation along the two meridians and the large zonal variation between them. Tracking the individual terms, month by month, illustrates the rate of the Sverdrup adjustment to the local wind stress with surface elevation rising as fast as 10 cm per month.
The North Equatorial Countercurrent observed during the Programme Francais Ocean Climat dans l'Atlantique Equatorial Experiment in the Atlantic Ocean, July 1982 to August 1984
Authors: Hénin C. , Hisard P.
Published: February 2008

Observations from Programme Francais Océan Climat dans l'Atlantique Equatorial (FOCAL) cruises in 1982 and 1984 have confirmed that in the central Atlantic Ocean the North Equatorial Countercurrent (NECC) has a well‐defined seasonal regime with a very reduced flux during spring. The main core of the NECC always lies between 4°N and 6°N. Focal observations have also shown that a long‐term change of NECC may occur and contribute to the development of an “El Niño” type event in the eastern Atlantic Ocean.
Multiple receivers in single vertical slice ocean acoustic tomography experiments
Authors: Howe Bruce M.
Published: February 2008

Range‐dependent information about the ocean can be obtained from a vertical slice tomography experiment with a single source‐receiver pair (Howe et al., 1987). For this situation we consider the improvement to the estimated fields of sound speed (∼temperature) and current velocity possible from receiving hydrophones widely spaced in the vertical at each end of the slice. Simulations were carried out varying the number of receivers (1–5), the range, and the travel time data error. The ocean was represented by a quasi‐geostrophic spectral model with a Gaussian correlation length scale of 100 km. Results are as follows: (1) the range‐dependent sound speed field is well resolved at 300 km with additional receivers but poorly resolved at 1000 km, (2) the error in the range‐averaged sound speed is reduced substantially by adding more receivers, and (3) errors in the range‐dependent and range‐averaged current velocity are unaffected by adding receivers.
The transilient model of the upper ocean
Authors: Stull Roland B. , Kraus Eric B.
Published: February 2008

The transilient method deals with the parameterization of turbulent transports by a spectrum of eddies that transport fluid properties over a range of distances. After explanation and discussion of the concept the results of a prediction are tested against an observed development in the upper ocean. This is followed by comparisons between the transilient model and other forms of mixed‐layer or upper ocean modeling.
A coupled one‐dimensional sea ice‐ocean model
Authors: Lemke Peter
Published: February 2008

A prognostic one‐dimensional mixed layer‐pycnocline model describing the vertical structure of the upper ocean is coupled to a thermodynamic sea ice model. The coupled prognostic model is compared with the more usual sea ice model overlying a fixed mixed layer with constant oceanic heat flux and is then applied to investigate the effect of temporal and regional variations of the entrained oceanic heat flux on the sea ice cover in both polar regions. In the southern ocean a standard simulation is compared with two perturbation experiments which both describe the occurrence of a polynya. In the Arctic Ocean the effect of possible Soviet river diversions is investigated. Finally, the response of the coupled model to paleoclimatic forcing and boundary conditions is presented.
Towed thermistor chain observations of fronts in the subtropical North Pacific
Authors: Samelson Roger M. , Paulson Clayton A.
Published: February 2008

A thermistor chain was towed 1400 km through the eastern North Pacific subtropical frontal zone in January 1980. The observations resolve surface layer temperature features with horizontal wavelengths of 0.2–200 km and vertical scales of 10–70 m. The dominant features, which have horizontal wavelengths of 10–100 km, amplitudes of 0.2°‐1.0°C, and random orientation, likely arise from baroclinic instability. Associated with them is a plateau below 0.1 cpkm in the horizontal temperature gradient spectrum. Strong temperature fronts O(1°–2°C/3–10 km) are observed near 33°N, 31°N, and 27°N. Temperature variability is partially density compensated by salinity, with the fraction of compensation increasing northward. There is evidence of vertical mixing during high winds. Temperature at 15‐m depth is roughly normally distributed around the climatological surface mean, with a standard deviation of approximately 0.5°C. The standard deviation would correspond to an adiabatic meridional displacement of 80–100 km in the mean gradient. Horizontal temperature gradient at 15‐m depth has maximum values in excess of 0.25°C/100 m and kurtosis near 80. In the band 0.10–1 cpkm, the 15‐m gradient spectrum is inversely proportional to wave number, consistent with predictions from geostrophic turbulence theory, while the spectrum at 70‐m depth has additional variance that is consistent with Garrett‐Munk internal wave displacements.
Modeling of oceanic fronts using a particle method
Authors: Pavia Edgar G. , Cushman‐Roisin Benoit
Published: February 2008

A particle‐in‐cell method, which has been successfully applied to problems in plasma physics, is adapted to the problem of oceanic geostrophic fronts. The thrust of the present article is the development, exposition, and testing of the method by means of synthetic examples. The advantage of this approach is its direct applicability to a class of oceanic problems which, for the most part, have remained unsolved. The method is computationally straightforward and efficient. It is also robust (the overall solution does not depend on the details of the initial distribution of material points) and numerically accurate (invariants are well conserved ).
Wind stress curl variability over the North Pacific from the comprehensive ocean‐atmosphere data set
Authors: Rienecker Michele M. , Ehret Laura L.
Published: February 2008

Wind stress curl patterns over the north Pacific, between 3° and 55°N, are calculated from the Comprehensive Ocean‐Atmosphere Data Set (COADS). The mean wind stress curl pattern consists of a basin‐wide band of negative curl south of about 30°N and a basin‐wide band of positive curl to the north. Most of the variance lies in the northern half of the domain, associated with variability in the Aleutian low during winter. The dominant modes of variability are associated with the changes in position and intensity of the Aleutian low and the north Pacific (subtropical) high, each of which extends across the basin, the former in winter and the latter in summer. The seasonal signal accounts for about 40% of the variability in the region of the Aleutian low, about 30% of the variability in the northeast of the basin, and about 60% of the variability in the southwest of the basin between 20° and 30°N. The seasonal signal and first three nonseasonal empirical orthogonal functions (eofs) account for about 60% of the total variability in the mid‐latitude interior Pacific. The first eof represents variations in intensity of the Aleutian low, the second eof represents changes in intensity of the subtropical high and in the latitudinal position of the Aleutian low, and the third eof represents changes in the longitudinal position and orientation of the low. These three eofs together account for about 30% of the nonseasonal variability. On an interannual time scale, a negative (positive) wind stress curl anomaly in winter in the northeast often coincides with a positive (negative) SST anomaly in that region, although the relationship is far from perfect because of the importance of other mechanisms which influence SST variability. There is no distinct relationship between El Nino‐southern oscillation events and wind stress curl anomalies, although weak El Ninos seem to coincide with a positive wind stress curl anomaly across the central north Pacific.
Instability of a buoyancy‐driven coastal jet: The Gaspé Current and its St. Lawrence precursor
Authors: Mertz Gordon , El‐Sabh Mohammed I. , Proulx Denis , Condal Alfonso R.
Published: February 2008

The discharge of the St. Lawrence River drives a buoyant jet which extends along the south shore of the lower St. Lawrence estuary and, combining with the northwest Gulf of St. Lawrence cyclonic gyre, becomes the Gaspé Current. In both the estuarine jet and the Gaspé Current, strong lateral and vertical shears are present. Satellite thermal imagery has shown that the Gaspé Current is unstable. Its instabilities are manifested as prominent wave disturbances and eddy features. We use satellite thermal images from 3 different years to show that unstable disturbances are also characteristic of the estuarine jet. We update previous work to show that Gaspé Current is both baroclinically and barotropically unstable. Our model studies also show that this conclusion is valid for the estuarine jet as well. Finally, we discuss a sequence of satellite images showing the development of an unstable disturbance apparently triggered by an eastward wind pulse.
Geosat crossover analysis in the tropical Pacific: 1. Constrained sinusoidal crossover adjustment
Authors: Tai Chang‐Kou
Published: February 2008

A new method (called constrained sinusoidal crossover adjustment) for removing the orbit error in satellite altimetry is tested (using crossovers accumulated in the first 91 days of the Geosat nonrepeat era in the tropical Pacific) and found to have many excellent qualities. Two features distinguish the new method from the conventional bias‐and‐tilt crossover adjustment. First, a sine wave (with wavelength equaling the circumference of the Earth) is used to represent the orbit error for each satellite revolution, instead of the bias‐and‐tilt (and curvature, if necessary) approach for each segment of the satellite ground track. Second, the indeterminacy of the adjustment process is removed by a simple constraint that minimizes the amplitudes of the sine waves rather than by fixing selected tracks. Overall, the new method is more accurate, more efficient, and much less cumbersome to implement than the old method. The idea of restricting the crossover adjustment to crossovers between tracks that are less than certain days apart in order to preserve the large‐scale long‐term oceanic variability is also tested with inconclusive results because the orbit error was unusually nonstationary in the initial 91 days of the Geosat mission.
Bomb radiocarbon in the Red Sea: A medium‐scale gas exchange experiment
Authors: Cember Richard
Published: February 2008

The history of bomb‐produced radiocarbon in the surface waters of the Red Sea and the western Gulf of Aden was reconstructed from annual growth bands of corals. Gulf of Aden surface water entering the Red Sea and flowing to the north at the surface of the Red Sea becomes progressively enriched in bomb 14C by air‐sea exchange of carbon dioxide. With physical oceanographic observations and analysis as the basis of a simple model, this progressive northward enrichment can be used to calculate a mean invasion flux for CO2 across the Red Sea surface. The CO2 invasion flux so calculated is 8 mol/m2/yr with an uncertainty of approximately 2 mol/m2/yr. When combined with the extensive historical observations of wind speeds in the Red Sea, the calculated CO2 invasion flux supports the empirical relationship between CO2 invasion and wind speed proposed by other workers. Sea surface pCO2 was measured at seven stations along the length of the Red Sea in January 1985. These pCO2 data show that in midwinter the net flux of CO2 across the Red Sea surface (i.e. the difference between the invasion and evasion fluxes) is approximately zero for the Red Sea as a whole.
Influence of local and remote wind forcing in the Gulf of Guinea
Authors: Houghton Robert W.
Published: February 2008

SEQUAL/FOCAL (Seasonal equatorial Atlantic/Programme Francais Ocean et Climat dans l'Atlantique Equatorial) data are analyzed to investigate the question of the relative importance of local and remote wind forcing in the equatorial Gulf of Guinea. The difference in the timing and rate of intensification of the winds in the eastern and western equatorial Atlantic Ocean for 1983 and 1984 is used to distinguish local and remote forcing efforts. It is found that, although asymmetry of the mixed layer thermal structure in the Gulf of Guinea can be attributed to the shallow circulation driven by the local meridional wind, the rapid cooling and the formation of a sharp thermal front at the equator and a local sea surface temperature (SST) minimum just south of the equator are correlated with the shoaling of the thermocline and this in turn is attributed to the remote forcing effect of the zonal wind intensification to the west. These results provide credence for previous conclusions by Servain et al. (1982) that the Gulf of Guinea SST is more strongly correlated with wind stress in the western equatorial Atlantic Ocean.
Distributions of suspended sediment at high water in a macrotidal estuary
Authors: Uncles R. J. , Stephens J. A.
Published: February 2008

A turbidity maximum is consistently observed in the upper reaches of the Tamar estuary at high water. Neap tide suspended particulate matter (SPM) concentrations are typically 20 ppm at high water; spring tide concentrations are typically an order of magnitude greater. The location of the turbidity maximum is usually associated with the freshwater‐saltwater interface but occasionally occurs further up‐estuary. At neap tides the maximum is less defined and can be masked by freshwater SPM concentrations. The spring tide maximum is generally small during winter periods, when it is located down‐estuary, and reaches its largest concentrations during summer when it is close to the head. About 65% of the variance in the magnitude of the maximum at spring tides can be explained in terms of its distance from the head. The position of the maximum is determined mainly by freshwater runoff with a logarithmic regression explaining about 80% of the variance. Only 30–35% of the variance in the turbidity maximum magnitude and location at neap tides can be explained in terms of tidal range and runoff. A tidal resuspension model is considered which ignores density effects but which has a spatially independent, runoff dependent (but otherwise time independent) erodibility constant as a single “free” parameter. The model provides a reasonable description of the magnitude and location of the turbidity maximum in the Tamar, both at spring and neap tides, despite the fact that the maximum usually occurs near the freshwater‐saltwater interface (which in itself would strongly suggest that gravitational circulation and intratidal stability effects have a strong influence on the location of the maximum). It is possible that all three mechanisms act together to produce a much narrower maximum than we have simulated, with resuspension being enhanced in the strongly mixed fresh water behind the interface, and tidal pumping and gravitational circulation accumulating sediment close to the interface.