bluuebunny/crossref_metadata_2025 huggingface dataset:
Geochemistry and deposition of 7Be in river‐estuarine and coastal waters
Authors: Olsen C. R. , Larsen I. L. , Lowry P. D. , Cutshall N. H. , Nichols M. M.
Published: February 2008

The atmospheric flux of cosmogenic 7Be (53.3‐day half‐life) and the mode of 7Be deposition in river‐estuarine and coastal environments have been examined. The atmospheric flux of 7Be commonly supports inventories ranging from 1.0 to 2.0 pCi/cm2 (1 pCi = 0.037 Bq). Beryllium 7 concentrations in water phase samples, collected across salinity gradients in several estuaries along the eastern coastline of the United States, range from 0.03 to 0.53 pCi/L and primarily reflect variations in 7Be supply and sorption kinetics. The major process controlling the concentration of 7Be on estuarine suspended particles appears to be the length of time that these particles remain in the water column. Field particle‐to‐water distribution coefficients for 7Be have a median value of about 4 × 104 but range over an order of magnitude reflecting short‐term variations in 7Be input, particle dynamics, and particulate iron content rather than equilibrium sorption‐desorption responses to changes in water salinity or particle type. Residence times of 7Be in the water column range from a few days in estuarine areas of rapid fine‐particle deposition, to several weeks in high‐energy environments where pronounced sediment resuspension reintroduces deposited 7Be back into the water column. Inventories of 7Be in sediments range from nondetectable to 3.3 pCi/cm2, with the highest inventories in areas where fine particles are accumulating rapidly. Such sites are also major repositories for other particle‐reactive substances. A 7Be budget for the James estuary indicates that less than 5% of the expected 7Be input is in the water column and that the short‐term estuarine trapping efficiency for atmospherically derived 7Be is somewhere between 50 and 100%.
On satellite scatterometer capabilities in air‐sea interaction
Authors: Brown R. A.
Published: February 2008

The verified capabilities and some practical usage of the satellite scatterometer in geophysical data production have demonstrated the value of this instrument. This evaluation of scatterometer ability to measure marine winds includes the scatterometer verification data, the state of the art planetary boundary layer model relating the wind profile in the atmosphere to the surface stress, and the pertinent results of the Storms Response Experiment.
Aspects of the determination of winds by means of scatterometry and of the utilization of vector wind data for meteorological forecasts
Authors: Pierson Willard J. , Sylvester Winfield B. , Donelan Mark A.
Published: February 2008

Research applicable to measuring winds with a scatterometer and the subsequent use of the data is briefly summarized. Data that demonstrate that (Ū(λ/2)/C(λ)) − 1, which is a quantity closely related to the normal stress, is more closely correlated to the nondimensionalized wave spectrum at L band, (ϕ(ω)ω5/g2), than either Ū(19.5) or u*, which is related to the shear stress, are given. The SOS wind recovery algorithm is shown to fail for light winds (given the power law assumption) and to bias climatological wind data. The data from a scatterometer are far too dense to be used in a synoptic scale analysis. Properties of superobservations to be used for synoptic scale analyses at a 1° resolution are derived and shown to produce very accurate wind fields, given that the scatterometer winds are correct. Superobservations are shown to yield reliable estimates of the horizontal component of the divergence and the curl of the wind stress. Disadvantages of a plus or minus 3‐hour data window for scatterometer data assimilation are described.
Structure of the surface wind field from the Seasat SAR
Authors: Gerling T. W.
Published: February 2008

An intensive analysis of the vector wind field of one Seasat data set: pass 1339 is described. Wind speed and direction signatures are found in Seasat SAR (synthetic aperture radar) images, and the resulting estimates are compared with the Seasat‐A scatterometer system (SASS) and simultaneous NOAA P‐3 aircraft measurements. A power law is presented to relate SAR‐measured backscatter to SASS‐estimated wind speed, and the SAR estimates are shown to agree with the SASS estimates to within a standard error of 0.7 m/s over a range of wind speeds from 3 m/s to 13 m/s. The surface expressions of atmospheric roll vortices are apparent in several of the SAR images and may be responsible for the wind‐direction signature in these cases. Wind field estimates averaged over regions of variable sizes are possible because of the high resolution of SAR imagery. A method for extracting low wave number directionality and its variability from SAR spectra is described, and SAR direction estimates obtained from spectra of 6.4‐km‐square images are shown to have a precision of approximately 10°. Although a comparison data set that could validate these higher resolution estimates is lacking, averages over 40‐km‐square regions are in good agreement with the other wind field information. The SAR wind direction estimates yield a more complete interpretation in a region with a turning wind field near a front that is ambiguous with only SASS observations. In this region the flow patterns of the high‐resolution estimates appear consistent with our knowledge of the overall circulation, considering all the observations. However, in another region the small‐scale variability is too large and random to represent real wind variability, although averages derived from these estimates are still reliable.
On crossover adjustment in satellite altimetry and its oceanographic implications
Authors: Tai Chang‐Kou , Fu Lee‐Lueng
Published: February 2008

It is argued that, to remove the satellite orbital errors, the crossover adjustment method that represents orbital errors in terms of Fourier series is preferable to the conventional bias‐and‐tilt crossover adjustment method. However, no matter what technique is used in the crossover adjustment, orbital errors will introduce a geographically dependent error (mostly a large‐scale slope which, in terms of spherical harmonics, is represented by the degree 1 terms) into the derived sea surface topography. This is because the responsible orbital errors have left no traces in crossover differences and therefore can never be removed. However, it is possible to reduce this fundamental uncertainty substantially if the record length is long enough. Its implications on observing the basin‐scale ocean circulation by satellite altimetry are discussed. We also propose new methods for observing the large‐scale oceanic variability (the conventional approach limited us to observing the mesoscale variability).
Semidiurnal internal tide in JASIN: Observations and simulation
Authors: deWitt L. M. , Levine M. D. , Paulson C. A. , Burt W. V.
Published: February 2008

Temperature was observed in the upper 80 m by moored thermistor chains at three locations in Rockall Channel west of Scotland. Isotherms were interpolated, and a 1‐week period of exceptionally energetic tidal oscillations was analyzed. The moored array (horizontal separations ranging from 6 to 20 km) was used as an antenna to determine the dominant horizontal wavelength and direction of propagation of the internal tide within the array. Rockall Bank, 100 km to the southeast, was identified as the source of the internal tide. The semidiurnal internal tide generated by the interaction of the surface tide with Rockall Bank was simulated by use of a model due to Prinsenberg and Rattray. The model predicts generation of the internal tide at the shelf break and propagation seaward as energetic beams which lie along internal wave characteristics. Some energy is trapped near the surface in association with the pycnocline. There is substantial structure in the velocity and vertical displacement fields. Most of the total energy of the internal tide is in the first vertical mode. However, at particular depths, vertical modes as high as 4 (horizontal wavelengths of 25 km) dominate. The high degree of spatial variability in the modeled internal tide illustrates the potential for error when basing a description of the tide on sparse observations. There is good agreement between the modeled vertical displacements and the 1‐week period of energetic oscillations of isotherm depth observed at the moorings. In addition, there is good agreement between the model and the tidal velocity variance measured during the same week at depths ranging from 10 to 1000 m and distances ranging from 50 to 130 km from Rockall Bank. Richardson numbers associated with the vertical shear of the modeled internal tide range down to values less than 2.
Stem waves along a depth discontinuity
Authors: Liu Philip L.‐F. , Yoon Sung B.
Published: February 2008

The nonlinear Schrödinger equation derived by Liu and Tsay (1984) is used to investigate the forward scattering of the second‐order Stokes waves by a depth discontinuity. It is shown that, due to nonlinearity, stem waves develop along a line caustic. The structure of the present stem waves is similar to that found by Yue and Mei (1980) along the wall of a thin wedge.
A mixed layer beneath melting sea ice in the marginal ice zone using a one‐dimensional turbulent closure model
Authors: Ikeda Motoyoshi
Published: February 2008

A level 2 second‐order turbulent closure model is employed to study the surface mixed layer developing between sea ice and a relatively warmer background water in the marginal ice zone. The model is driven by a suddenly imposed ice‐water stress and warming in the water. The mixed layer rapidly develops in 1 day and afterwards is gradually eroded at its bottom mainly by an inertial oscillation. The ice velocity is larger with the stronger stress, but the mixed layer is thicker. Hence the length scale of ice travel before complete melting is nearly independent of the ice‐water stress. Higher temperature of the background water gives more heat to ice but produces a thinner mixed layer. The product of the travel distance and (the background temperature minus the freezing point) is larger for the warmer water. Heat flux through the ice due to atmospheric forcing is a minor mechanism for melting in the marginal ice zone.
A kinematic analysis of polarized eddy fields using drifter data
Authors: Middleton John F. , Garrett Chris
Published: February 2008

A kinematic formalism for the Eulerian and Lagrangian analysis of drifter data is developed for homogeneous, isotropic, two‐dimensional flows which exhibit a preferred sense of rotation. Principal results include a new measure of rotation h*, defined from orthogonal velocity components, which is related to the covariance of horizontal divergence and rate of change of vorticity. An analogous Lagrangian correlation hL may indicate a rotational sense opposite to h* due to the preferential sampling by drifters of regions of previous net convergence which are regions of cyclonic vorticity for quasi‐geostrophic motions. These kinematic results are illustrated by an analysis of 197 iceberg trajectories from the Labrador shelf, which do indeed show opposite rotational senses for h* and hL.
Temporal variability of lead in the western North Atlantic
Authors: Boyle E. A. , Chapnick S. D. , Shen G. T. , Bacon M. P.
Published: February 2008

Consumption of alkyl leaded gasoline has decreased considerably in the United States over the last 15 years. In order to evaluate the chemical response of the ocean to decreased atmospheric deposition of anthropogenic lead, new 210Pb and stable Pb data have been obtained near Bermuda (June 1983 to December 1984). Concentrations of these tracers in the mixed layer are highly variable during the period of observations (+/− 25%). From June through September, soluble eolian deposits accumulate in the shallow mixed layer because mixing and productivity are inhibited by the seasonal thermocline. In the fall, these enriched surface waters mix with upper thermocline waters, and surface Pb concentrations decrease. In the winter, storms from the east coast of North America cause local episodes of high Pb and 210Pb input into the ocean surface; the resulting areally‐limited high Pb concentrations are dispersed within less than 2 weeks by vertical and horizontal mixing. Pb/210Pb ratios in surface waters are almost invariant over this period (averaging 669 pmol/dpm, ranging from 564 to 718 pmol/dpm). Surface Pb/210Pb appears to have declined by a factor of 2 since 1979, similar to the 2.6‐fold decrease in U.S. leaded gasoline consumption during this period. A substantial fraction (on the order of 10%) of gasoline Pb is transported into the ocean. Pb concentrations in the upper thermocline may have declined by about 15% from 1979 to 1984. The helium‐tritium thermocline ventilation model of Jenkins (1980), coupled with boundary conditions appropriate for Pb and 210Pb, shows that the supply of Pb and 210Pb to the thermocline is dominated by lateral isopycnal ventilation. The shape of the vertical profile is dominated by this physical ventilation, near‐surface biological removal processes, in‐situ scavenging, and (for stable lead) time‐dependent input. Vertical transport by particles is responsible for minimal transport of dissolved lead into the upper ocean. Similar processes are likely to account for the plutonium maximum in the thermocline of the North Pacific. Observations of Pb and other reactive species in winter surface outcrops of thermocline isopycnals would provide valuable constraints on chemical processes within the thermocline.
Simultaneous spatial and temporal measurements of the internal wave field during MATE
Authors: Levine Murray D. , Irish James D. , Ewart Terry E. , Reynolds Stephen A.
Published: February 2008

A statistical description of the deep ocean internal wave field is presented using measurements from the Midocean Acoustic Transmission Experiment, conducted near Cobb Seamount in the NE Pacific (46°46′N, 130°47′W) during June–July 1977. The unique feature of this experiment is the variety of data obtained simultaneously from the same location: time series of temperature and velocity, and vertical and horizontal profiles of temperature. A generalized form of the Garrett‐Munk (GM) internal wave spectrum is developed and used to interpret the data. This spectral model is specified by three parameters,
, t, and p (energy level, wave number bandwidth, and frequency spectral slope, respectively). The variety of measurement types permit these three model parameters to be estimated from more than one measurement. The overall best fit values to the MATE data were p = 2.7 (GM use p = 3), t = 3.1 m−1 s (equivalent to j* = 6, twice the GM value), and
(within 20% of the GM level). Although significant differences were found in the values of the bandwidth (t) and spectral slope (p) from those specified by Garrett‐Munk, the deviations are consistent with the behavior expected in a random internal wave field.
A modal decomposition of the internal tide in a deep, strongly stratified inlet: Knight Inlet, British Columbia
Authors: Webb A. J. , Pond S.
Published: February 2008

This paper seeks to answer the question, How much of the internal tide propagating up Knight Inlet, British Columbia, is reflected by a right‐angled bend? The internal tide in Knight Inlet is generated by the interaction of the barotropic tide with a shallow sill seaward of the bend. It then propagates in both directions as a traveling Kelvin wave. The up‐inlet propagating wave then encounters the bend, where some of it may be reflected. The study is based upon 2⅓ months of cyclesonde current meter data from four stations taken during the summers of 1981 and 1983. The vertical profiles of amplitude and phase of the M2 constituent of longitudinal velocity and density fluctuations are decomposed into a truncated series of normal modes for waves propagating both up‐inlet and down‐inlet. At the two stations up‐inlet of the sill, acceptable fits can be obtained using only two up‐inlet propagating waves, indicating that the data are compatible with the low reflection found by Webb and Pond (1986). At the two stations seaward of the sill, the up‐inlet energy flux is of the same order of magnitude as the down‐inlet flux, indicating a second source of internal tide seaward of those two stations. The results indicate that only 30–50% of the power removed from the barotropic tide is being fed into the internal tide in the summer.
Response [to “Isotopic versus micrometeorologic ocean CO2 fluxes: A serious conflict” by W. Broecker et al.]
Authors: Wesely Marvin L.
Published: February 2008

Measurements of short‐term, local air‐sea exchange of CO2 by eddy correlation in the atmosphere from surface towers have shown that the transfer (piston) velocities in coastal areas are very large in comparison to long‐term oceanic estimates from radioisotope studies. The latter agree with radon evasion and laboratory investigations involving nonreactive gases. Horizontal atmospheric advection seems to be the most likely source of significant error in the eddy correlation estimates but is probably not the cause of the large transfer velocities because they were measured in a wide range of conditions by independent investigators. Furthermore, extrapolation of the large transfer velocities measured by the eddy correlation measurements to world average air‐sea exchange rates does not provide a realistic basis on which to evaluate the validity of the local eddy flux measurements in coastal areas. Important chemical and physical phenomena affecting CO2 exchange rates may be quite different in coastal as opposed to open‐ocean conditions, and further research is needed in both cases.
Measurement of microwave backscattering signatures of the ocean surface using X band and Ka band airborne scatterometers
Authors: Masuko Harunobu , Okamoto Ken'ichi , Shimada Masanobu , Niwa Shuntaro
Published: February 2008

An airborne microwave scatterometer‐radiometer system operated in X band and Ka band was applied to the observations of microwave backscattering signatures of the ocean. The normalized radar cross sections σ0 were measured as combined functions of microwave frequency (10.00 GHz and 34.43 GHz), polarization (HH and VV), incident angle (0°–70°), azimuth angle (0°–360°), and wind speed (3.2–17.2 m/s). The azimuth anisotropic signatures for Ka band are confirmed to be similar to those for X band, and the wind speed dependences are analyzed for each azimuth angle, polarization, and incident angle. For each parameter the behaviors of σ0 for microwave frequencies is shown as compared with the results obtained by other experiments and theories. The effective reflection coefficient, the mean square surface slope, and the two‐dimensional wave number spectrum of the short surface waves are estimated from the microwave scattering signatures.
Hydrography, chemistry, and radioisotopes in the Southeast Asian basins
Authors: Broecker Wallace S. , Patzert William C. , Toggweiler John R. , Stuiver Minze
Published: February 2008

Nutrient constituent, radiocarbon, and radium data are presented for the waters in the Southeast Asian basins. These results suggest very rapid ventilation by waters passing over the sills that separate these basins from one another and from the open Pacific.
On the parameters influencing air‐water gas exchange
Authors: Jähne Bernd , Münnich Karl Otto , Bösinger Rainer , Dutzi Alfred , Huber Werner , Libner Peter
Published: February 2008

Detailed gas exchange measurements from two circular and one linear wind/wave tunnels are presented. Heat, He, CH4, CO2, Kr, and Xe have been used as tracers. The experiments show the central importance of waves for the water‐side transfer process. With the onset of waves the Schmidt number dependence of the transfer velocity k changes from k ∝ Sc−⅔ to k ∝ Sc−½indicating a change in the boundary conditions at the surface. Moreover, energy put into the wave field by wind is transferred to near‐surface turbulence enhancing gas transfer. The data show that the mean square slope of the waves is the best parameter to characterize the free wavy surface with respect to water‐side transfer processes.
Turbidity currents and submarine channel formation in Rupert Inlet, British Columbia: 2. The roles of continuous and surge‐type flow
Authors: Hay Alex E.
Published: February 2008

Acoustic backscatter images are presented of the continuous flow turbidity current resulting from mine tailing discharge into Rupert Inlet. The current flows partially within a submarine channel, which both hooks to the left and meanders. The images show the turbidity current spilling over the outer levees at channel bends. A model for continuous turbidity flow incorporating overspill is developed and applied to the left‐hooking section of the submarine channel. It is very likely that the observed overspill is primarily an inertial effect resulting from the outer bank being more sharply curved than the channel axis. The model results are combined with a sediment accumulation budget based on successive seismic profiling surveys and with results for surge‐type flows (taken from the companion paper (Hay, this issue)). It shows that surges are primarily responsible for the transport of tailing to large distances from the point of discharge and should recur at 1‐ to 2‐day intervals on average. This is consistent with the characteristics of coarse‐grained turbidites observed in cores from the levees. Relative to the intervening fine‐grained mud deposits the turbidites increase both in thickness and frequency in the downchannel direction. Furthermore, the surge recurrence interval obtained from the number of turbidites per core and the local accumulation rate is 2–5 days, essentially the same as that obtained from the model. Suspended tailing transport within the channel appears to be dominated by surge‐type turbidity currents except close to the outfall. It is concluded that the surge‐type flows are most responsible for the formation and morphology of much of the channel. It is not clear, however, that the meanders are formed principally by surges. Although the surges occur frequently and transport most of the sediment in the meander reach, the volume transport is dominated by continuous flow.
Long internal waves and columnar disturbances in the Strait of Messina
Authors: di Sarra A. , Pace A. , Salusti E.
Published: February 2008

During a pilot cruise in the Strait of Messina we observed the interface time evolution between Atlantic and Levantine water layers due to semidiurnal tides. Our data are in fairly good agreement with the models computed by Del Ricco (1982) and by Hopkins et al. (1984), as regards long‐lasting (1 hour or more) water movements. Quick transient perturbations of columnar shape (probably eddies) which we have called Bignami columns, were also observed and analyzed using both a KODEN fish finder and moored temperature sensors.
Excess 3He in the ocean surface layer
Authors: Fuchs Gerhard , Roether Wolfgang , Schlosser Peter
Published: February 2008

The actual ocean‐atmosphere 3He solubility equilibrium is a dynamic one, and it corresponds to δ3He values that are about 0.2% lower than the static equilibrium values reported by Benson and Krause (1980). We estimate this shift theoretically by considering gas transfer between air bubbles and water, and we present evidence from laboratory and field observations. A compilation of ocean surface layer δ3He observations shows widespread occurrence of excess 3He (≤ 2%) relative to a dynamic equilibrium with atmospheric helium. Large excesses are found for deep surface layers under conditions of seasonal thermocline erosion (winter convection). A simulation of observed δ3He depth profiles in an area of deep winter convection west of the British Isles (by means of a simple one‐dimensional model) is generalized to estimate initial tritium‐ 3He ages at the point of formation of a subsurface water mass as a function of the seasonal‐maximum surface layer depth, Dmax. In situations of areally extended seasonal convection with Dmax < 600 m, the remaining initial‐age uncertainty is believed to amount to no more than about ± 0.3 years. Far larger uncertainties must be expected in situations of deep‐reaching chimney‐type convection. The observed occurrence of excess 3He also in summer observations is taken to reflect intermittent surface‐layer/thermocline exchange.
A constraint on a trapped edge wave solution for convex upward topographies
Authors: Shaw Richard Paul , Paskausky David
Published: February 2008

A recent paper (Shaw and Paskausky, 1986) developed an analytical solution for edge waves trapped along a straight coastline with an exponentially increasing offshore bottom topography. A review of the physical constraints used has led to a reduced range of validity of those results.
Bottom ablation and heat transfer coefficients from the 1983 Marginal Ice Zone Experiments
Authors: Josberger Edward G.
Published: February 2008

Bottom ablation in the marginal ice zone (MIZ) is a fundamental process that controls the ice edge position in both the winter and the summer. During the east and west Marginal Ice Zone Experiments (MIZEX West and MIZEX East) in 1983, periodic sonic distance measurements between the overlying ice and transducers fixed on masts below ice floes determined the bottom ablation. The melt rates for floes within 15 km of the ice edge ranged from near zero when the ice was in water at the freezing point to 0.5 m d−1 when the ice entered warm water, greater than 3 K to the south. Simultaneous velocity and temperature measurements at 2 m below the ice in MIZEX West and at 2 m and 10 m below the ice in MIZEX East, show the response of the melt rate to changing oceanographic conditions. For the first time, the combined oceanographic and ablation measurements allow the direct calculation of the bulk heat transfer coefficient Ch between the ice and the ocean at 2 m and 10 m below the ice. For the Bering Sea experiment, Ch was 8 × 10−4, while for the Fram Strait experiment Ch varied from 2 × 10−4 to 4 × 10−4. Within each set of experiments, Ch remained nearly constant over a wide range of melt rates, relative ice water speeds, and seawater temperatures.
Shelf and slope circulation induced by fluctuating offshore forcing
Authors: Chapman David C. , Brink Kenneth H.
Published: February 2008

A linear model which includes continuous vertical stratification, arbitrary cross‐shelf bottom topography, and bottom friction is used to examine the response of shelf and slope waters to fluctuating offshore forcing in the form of a specified pressure field. For forcing which is periodic in the alongshore direction and in time, the response varies dramatically with frequency. For periods of less than about 10 days, the response is dominated by near resonances with free coastally trapped waves. These are not pure resonances because of the mismatch between the forcing structure and the free wave structure. For periods of greater than about 10 days, the velocity response decays away from the forcing with a scale determined by the projection of the forcing onto the flat‐bottom baroclinic modes, typically the first baroclinic Rossby radius. If the continental slope is encountered within this scale distance, then the flow is altered and creates a bottom‐trapped, alongshore velocity maximum seaward of the shelf break. Increased stratification enhances bottom trapping and inhibits flow across the slope, moving the maximum in alongshore velocity seaward, thus reducing the alongshore flow near the shelf break. The shelf response is always weak and barotropic. Furthermore, the slope response is largely independent of the shelf geometry, suggesting that narrow shelves appear to be more easily influenced by offshore forcing only because their coasts are closer to the forcing. The model is used to simulate the response to a Gaussian‐shaped anticyclonic eddy translating uniformly in the alongshore direction. The eddy flow is blocked by the topography and becomes squashed at the shelf break. Some shelf water is entrained creating a weak shelf circulation cell. The shoreward flow in the eddy cannot move onto the shelf and instead forms an alongshore jet near the shelf break. The jet extends away from the eddy in the direction toward which free coastally trapped waves propagate, but the alongshore velocity within the jet is opposite to the alongshore velocity within the eddy.
Processing and analysis of large volumes of satellite‐derived thermal infrared data
Authors: Cornillon Peter , Gilman Craig , Stramma Lothar , Brown Otis , Evans Robert , Brown James
Published: February 2008

Reducing the large volume of TIROS‐N series advanced very high resolution radiometer‐derived data to a practical size for application to regional physcial oceanographic studies is a formidable task. Such data exist on a global basis for January 1979 to the present at approximately 4‐km resolution (global area coverage data, ≈2 passes per day) and in selected areas at high resolution (local area coverage and high‐resolution picture transmission data, at ≈1‐km resolution) for the same period. An approach that has been successful for a number of studies off the east coast of the United States divided the processing into two procedures: preprocessing and data reduction. The preprocessing procedure can reduce the data volume per satellite pass by over 98% for full‐resolution data or by ≈84% for the lower‐resolution data while the number of passes remains unchanged. The output of the preprocessing procedure for the examples presented is a set of sea surface temperature (SST) fields of 512 × 1024 pixels covering a region of approximately 2000 × 4000 km. In the data reduction procedure the number of SST fields (beginning with one per satellite pass) is generally reduced to a number manageable from the analyst's perspective (of the order of one SST field per day). This is done in most of the applications presented by compositing the data into 1‐ or 2‐day groups. The phenomena readily addressed by such procedures are the mean position of the Gulf Stream, the envelope of Gulf Stream meandering, cold core Gulf Stream ring trajectories, statistics on diurnal warming, and the region and period of 18°C water formation. The flexibility of this approach to regional oceanographic problems will certainly extend the list of applications quickly.
Satellite passive microwave studies of the Sea of Okhotsk ice cover and its relation to oceanic processes, 1978–1982
Authors: Alfultis Michael A. , Martin Seelye
Published: February 2008

This paper describes the use of the Nimbus 7 Scanning Multichannel Microwave Radiometer (SMMR) satellite data to study the ice cover in the Sea of Okhotsk during the four winters of 1978–1982. The ice concentration estimates obtained from SMMR are used to study two different polynyas: one over the Kashevarova Bank, and the other over the northwest continental shelf. For the Kashevarova polynya this study shows that the polynya, which may be related to the upwelling observed in historic summer cruises, occurs directly over the bank. For the continental shelf, which because of strong offshore winds and cold temperatures is a region of high ice production, the polynya areas are combined with heat flux estimates from weather station data to yield the production rates of ice, salt, and dense shelf water. As a previous study by Kitani (1973) shows, the mixing of this dense shelf water with Pacific water yields a water mass unique to the Okhotsk, which is the layer of cold, low‐salinity intermediate water between depths of 150 and 800 m. From our calculations, we estimate that the dense shelf water is produced at an annual rate of about 0.5 Sv, and that the intermediate water is produced at a rate of 1–2 Sv, which yields a renewal time for this layer of 10–40 years.
El Niño events and their relation to the Southern Oscillation: 1925–1986
Authors: Deser Clara , Wallace John. M.
Published: February 2008

Relationships among sea surface temperatures (SSTs) at the coast of Peru and offshore, river discharge in northern Peru, and sea level pressure at Darwin, Australia, during the period 1925–1986 are investigated using time series plots, frequency distributions, and a simple statistical analysis. It is shown that SSTs undergo a larger seasonal cycle offshore than at the coast, exhibit more interannual variability during the warm than the cool season, are positively skewed during much of the year, and exhibit greatest month‐to‐month persistence during the cool season. Many, but not all, episodes of above normal coastal SSTs are accompanied by enhanced river discharge in northern Peru. Comparison of the Darwin pressure and coastal SST records during the past 60 years shows that El Niño events (episodes of above normal SSTs along the coast of Peru) have occurred both in advance of and subsequent to major negative swings of the Southern Oscillation (and associated climatic changes in the central equatorial Pacific). In addition, El Niño events and negative swings of the Southern Oscillation have occurred separately. Hence El Niño and the Southern Oscillation are more loosely coupled than other studies would imply.
The equatorial source of propagating variability along the Peru coast During the 1982–1983 El Niño
Authors: Enfield David B. , Cornejo‐Rodriguez Maria Del Pilar , Smith Robert L. , Newberger Priscilla A.
Published: February 2008

Using data obtained from tide gages in South America, current meters along the equator and the Peru coast, and an array of pressure gages and inverted echo sounders within and around the Galapagos archipelago, we have analyzed the equatorial origin of coastal trapped waves observed by Cornejo‐Rodriquez and Enfield (this issue) along the Peru coast during the intense 1982–1983 El Niño. The propagating fluctuations along the coast were much stronger at that time than either before or after the El Niño, and the variability was not locally forced by coastal winds. We find that the coastal variability was also more energetic during previous El Niño occurrences. At periods of 1–2 weeks the meridional component of currents on the equator is up to an order of magnitude more energetic than the zonal fluctuations and is consistently associated with sea level that fluctuates antisymmetrically between hemispheres. At periods longer than 2 weeks the zonal velocity component is more energetic, and the cross‐equatorial sea level variability is symmetric. The meridional and zonal phase structures of cross spectra involving the currents and sea level establish the 1‐ to 2‐week equatorial fluctuations as mixed Rossby‐gravity (Yanai) waves of low wave number with infinite phase speed (standing oscillations) in the middle of the band (10 days); the corresponding structures for longer periods are consistent with nondispersive Kelvin waves. Frequency domain EOF modes of the sea level and current data establish the mixed Rossby‐gravity waves as the principal source of the strong trapped wave variability in the 1‐ to 2‐week band along the Ecuador‐Peru coast during the 1982–1983 El Niño episode.
Changes in oyster condition index with El Niño‐Southern Oscillation events at 46°N in an eastern Pacific Bay
Authors: Schoener A. , Tufts D. F.
Published: February 2008

In 31 years of monitoring the condition index of temperate northeast Pacific oysters (Crassostrea gigas), the lowest annual index value was recorded during the 1982–1983 El Niño‐Southern Oscillation (ENSO) event. Crossspectral analyses of monthly fluctuations of the condition index with sea level height indicate that there are significant correlations between them, although out of phase. Coherent signals with an approximately 2‐year period have been detected in the data in the interval between ENSO events. We conclude that sea level height fluctuations may indirectly influence oyster growth, through alterations in productivity, and the availability of planktonic food resources.
On the deep‐water flow through the Faroe Bank Channel
Authors: Borenäs Karin M. , Lundberg Peter A.
Published: February 2008

A substantial part of the Norwegian Sea deep‐water outflow into the North Atlantic takes place via the Faroe Bank Channel, the deepest passage through the Greenland‐Scotland Ridge. In order to estimate this flux of cold, low‐saline bottom water, a field survey comprising hydrographie observations as well as current measurements was carried out in the channel during May 1983. Transport calculations were undertaken for a total of four sets of observations and yielded values ranging from 1.5 to 1.9 sverdrup. The outflow is most likely subjected to hydraulic control, and consequently, a simple model has been formulated in order to determine the maximum discharge through a rotating channel of parabolic cross section. This geometry is well‐adapted to the topography of the Faroe Bank Channel, and the theoretically predicted magnitude of the transport was found to be in good agreement with the observations.
Diurnal period wind stress and current fluctuations over the continental shelf off northern California
Authors: Rosenfeld Leslie K.
Published: February 2008

Diurnal period wind stress and current fluctuations measured over the continental shelf off northern California during the Coastal Ocean Dynamics Experiment in the summers of 1981 and 1982 are examined. The diurnal currents are strongly surface intensified, with amplitudes of up to 20 cm s−1. At depths of less than 35 m, the diurnal currents are nonstationary, and their amplitude is well correlated with the amplitude modulation of the local diurnal wind stress. Beneath the surface layer, the diurnal current vectors rotate clockwise with ellipse semi‐major axes of 1 to 3 cm s−1. A mixed layer model driven with diurnal wind stress and surface heat flux produces currents similar to those observed in the upper water column. The deeper currents are consistent with the combination of a freely propagating Kelvin and first‐mode coastal‐trapped wave and, over the inner shelf, with the interior flow forced by the diurnal wind stress in the presence of a coast.
Mean and tidal currents in Baltimore canyon
Authors: Hunkins Kenneth
Published: February 2008

The mean and tidal current fields within Baltimore Canyon and on the shelf and slope around it were observed with instrumented moorings at 12 sites. Currents on the shelf are similar to those observed elsewhere over the northeastern U.S. outer shelf with mean flow southwestward at 10 to 15 cm s−1 parallel to the shelf break. Tidal current velocity in the direction of the major axis of the M2 ellipse over the shelf is about 9 cm s−1. Currents within the canyon are complex. Mean flow near the bottom along the canyon axis is downcanyon at 5 cm s at a depth of 275 m, but upcanyon at 7 cm s−1 at 600‐m depth and negligible at depths of 1000 m and 1500 m. At 50 m above the bottom, mean flow at each of these sites is less than it is at 6 m above the bottom. The M2 tidal currents in the canyon tend to be aligned with topography and have velocities ranging up to 22 cm s−1. Maximum instantaneous current speeds were found near the bottom in the canyon axis with a peak speed for the entire survey of 106 cm s−1 near the bottom at the 275‐m level.
Low‐frequency current variability on the Labrador Shelf
Authors: Webster Ian , Narayanan Savithri
Published: February 2008

Current meter measurements from two locations on the northern part of the Labrador Shelf have been analyzed using empirical orthogonal function (EOF) analysis in the three frequency bands 0.09–0.18 cpd, 0.18–0.36 cpd, and 0.36–0.54 cpd. To describe the measurements in each frequency band, a numerical circulation model was developed for the shelf, driven by alongshore and onshore wind stresses and by flow through Hudson Strait. The latter flow is taken to arise from the atmospheric pressure variations over Hudson Bay and from the along‐static wind stress over Hudson Strait. The model appears to be quite successful in describing the circulation in the center frequency band. This suggests that the forcing within this band is primarily due to the alongshore wind stress over the shelf and to the flow through Hudson Strait. The model indicates that in the region of study, the mode 1 shelf wave dominates the velocity field over the upper part of the shelf, whereas mode 2 dominates the flow near the shelf break. In the first and third frequency bands the model is less successful in describing the measured currents. It is likely that this failure is at least in part due to the neglect of other forcing mechanisms, such as shelf waves propagating southward out of Baffin Bay.
The response of the equatorial Pacific Ocean to a westerly wind burst in May 1986
Authors: McPhaden Michael J. , Freitag H. Paul , Hayes Stanley P. , Taft Bruce A. , Chen Zeshi , Wyrtki Klaus
Published: February 2008

Western Pacific westerly wind bursts of 1‐ to 3‐week duration are potentially important in triggering and sustaining El Niño‐Southern Oscillation events. One such burst of 10‐day duration and maximum speeds of greater than 10 m s−1 occurred in May 1986 west of the date line. The response to this westerly wind burst is documented from equatorial current meter moorings, thermistor chain moorings, and sea level and hydrographic data. At 0°, 165°E in the western Pacific the thermocline was depressed by 25 m, sea surface temperature dropped by 0.3°–0.4°C, and sea level rose by 10–15 cm a few days after the maximum in westerly wind speed. Likewise, the South Equatorial Current rapidly accelerated eastward and attained speeds in excess of 100 cm s−1. Vertical shear in an approximately 100 m deep surface layer reversed within a few days of the winds, consistent with a simple model of equatorial mixed layer dynamics in which vertical eddy viscosities are inferred to be O(100 cm2 s−1). A sharp Kelvin wavelike pulse in sea level propagated out of the directly forced region into the central and eastern Pacific. The pulse took 45 days to travel from Tarawa (1°N, 173°E) to La Libertad (2°S, 81°W) on the South American coast, at an average phase speed of about 300 cm s−1. This is of the same order of magnitude as, but significantly higher than, the phase speed of a first baroclinic mode Kelvin wave and is probably the result of Doppler shifting by the Equatorial Undercurrent. A rise in sea surface temperature of about 1°C in 2 days occurred at 0°N, 110°W with the passage of the pulse. However, coincidental meridional advection of a sharp sea surface temperature front, rather than zonal advection of downwelling associated with the pulse, appears to be responsible for this warming. The relevance of this wind‐forced pulse to the subsequent evolution of the 1986–1987 El Niño‐Southern Oscillation event is discussed in the light of these observations.
Poleward flow off central California during the spring and summer of 1981 and 1984
Authors: Chelton Dudley B. , Bratkovich Alan W. , Bernstein Robert L. , Kosro P. Michael
Published: February 2008

Currents and winds measured over the continental shelf and upper continental slope during the first half of 1984 are analyzed to determine the character of the flow off central California (Point Conception to San Francisco). The mean flow was poleward from Point Conception to Point Sur, in opposition to the equatorward wind stress. The mean flow was equatorward north of Point Sur. Fluctuations in alongshore currents over the shelf were highly correlated with local winds everywhere except off Point Conception, where currents were not only uncorrelated with wind but also poorly correlated with currents farther north. North of Point Buchon there is evidence for poleward propagation of shelf current variability at 175–200 cm/s. The correlation between currents and local wind forcing dropped considerably beyond the shelf break, only 10–15 km offshore from the shelf moorings. During extended periods of weak equatorward winds, the poleward shelf flow south of Point Sur spreads farther offshore over the continental slope. A three week period of calm winds in July 1984 resulted in a 100‐km‐wide tongue of poleward flow extending 300 km along the California coast. Similar, but somewhat weaker, poleward surface flow occurred during the same period in 1981; a 2‐ to 3‐week period of calm winds in late June and early July 1981 resulted in a 100‐km‐wide tongue of poleward flow extending at least 150 km along the California coast. In contrast to the poleward flow on the shelf, which appears to be normal during spring and summer, the poleward surface flow observed over the slope in July 1981 and 1984 is unusual, based on historical hydrographic surveys off the central California coast. Poleward surface flow over the continental slope occurs seasonally in the winter but is not generally observed after February.
Optical modeling of the upper ocean in relation to its biogenous matter content (case I waters)
Authors: Morel André
Published: February 2008

The aim of the present study is to review and tentatively to interpret the optical behavior of oceanic case I waters, those waters for which phytoplankton and their derivative play a predominant role in determining their optical properties. Chlorophyll‐like pigment concentration is used as the index to quantify the algal material (living and detrital), and statistical relationships between this index and the depth of the euphotic layer, the spectral values of the attenuation coefficient for downwelling irradiance, or the scattering coefficient are investigated. On the basis of these statistical relationships a pigment‐dependent optical model is developed. It allows the propagation of the visible radiant energy within the ocean or the backscattered radiation from the upper layer to be predicted as a function of the local phytoplanktonic content. Other geophysical or geochemical applications are derived which concern the heating rate due to penetrating visible radiations or the rate of energy storage due to photosynthesis. The nonlinear trends observed in the algal biomass‐attenuation relationships are analyzed by (1) considering the rather regular change of the living‐to‐detrital organic carbon ratio which seems to occur in oceanic waters ranging from oligotrophic to eutrophic, and (2) accounting for the respective contributions of absorption (by pigmented cells) and of scattering (by all kind of particulates) in the attenuation process of radiant energy.
A theoretical study of large sea level oscillations in the western Mediterranean
Authors: Tintoré Joaquín , Gomis Damià , Alonso Sergio , Wang Dong‐Ping
Published: February 2008

Large sea level oscillations (up to 1‐m amplitude and around 10‐min period) have been observed in several bays and harbors of the western Mediterranean. These oscillations appear to be associated with short‐period (10 min) atmospheric pressure fluctuations (amplitude of 1.5 mbar). Using a model with a flat shelf and a sloping‐bottom harbor, we found that these oscillations were the result of a three‐way resonant coupling between an atmospheric gravity wave, a coastally trapped edge wave, and the normal modes of a harbor. The amplification mechanism was studied for the harbor of Ciutadella. Good agreement between the predicted and the observed frequencies and amplitudes is found.
Stability of a three‐dimensional foam layer in seawater
Authors: Peltzer Rodney D. , Griffin Owen M.
Published: February 2008

There are many dynamic events responsible for the production of a multilayer surface foam in seawater. The residence time of foam at the surface depends on the stability of the bubbles in that foam. This paper examines the stability of three‐dimensional foam layers of various thicknesses produced by blowing air through controlled laboratory samples of simulated seawater and a sample of seawater obtained from an Atlantic coastal site. The results clearly show that for oceanographically relevant salt concentrations between 20 and 36 parts per thousand there are no appreciable changes in the foaming characteristics of seawater due to salinity variations. The stability characteristics of real seawater closely followed those of the simulated seawater. Procedures and equations for estimating thickness variations and lifetimes of foam layers on a saltwater surface are contained in this paper. The results also provide some valuable insights into the influence of organic surface active materials that have been scavenged to the surface by rising bubbles and removed by the bursting process near the surface of a three‐dimensional foam layer.