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Showing papers in "Journal of Physical Oceanography in 1976"


Journal ArticleDOI
TL;DR: In this article, a model is presented whereby the thickness and extent of sea ice may be predicted in climate simulations, where a basic one-dimensional diffusion process is taken to act in the ice, with modifications due to penetration of solar radiation, melting of internal brine pockets, and accumulation of an insulating snow cover.
Abstract: A model is presented whereby the thickness and extent of sea ice may be predicted in climate simulations. A basic one-dimensional diffusion process is taken to act in the ice, with modifications due to penetration of solar radiation, melting of internal brine pockets, and accumulation of an insulating snow cover. This formulation is similar to that of a previous study by Maykut and Untersteiner, but the introduction of a streamlined numerical method makes the model more suitable for use at each grid point of a coupled atmosphere-ocean model. In spite of its simplicity, the ice model accurately reproduces the results of Maykut and Untersteiner for a wide variety of environmental conditions. In 25 paired experiments, annual average equilibrium thicknesses of ice agree within 24 cm for 75% of the cases; and the average absolute error for all cases is 22 cm. The new model has fewer computational requirements than one layer of ocean in the polar regions, and it can be further simplified if additional ...

1,200 citations


Journal ArticleDOI
TL;DR: In this article, the authors examined the variability of sea level pressure (SLP) and sea surface temperature (SST) in the mid-latitude North Pacific Ocean and found that SLP variability is concentrated in a few large scale modes but has a nearly white frequency spectrum.
Abstract: Nonseasonal variability of sea level pressure (SLP) and sea surface temperature (SST) in the mid-latitude North Pacific Ocean is examined. The objective is examination of the basic scales of the variability and determination of possible causal connections which might allow prediction of short-term climatic (time scales between a month and a year) variability. Using empirical orthogonal function descriptions of the spatial structure, it is found that SLP variability is concentrated in a few large-scale modes but has a nearly white frequency spectrum. SST variability is spatially complex (being spread over many spatial modes, some of which have small-scale changes) but is dominated by low-frequency changes. The use of linear statistical estimators to examine predictability is discussed and the importance of limiting the number of candidate data used in a correlation starch is underscored. Using linear statistical predictors, it is found that (A) SST anomalies can be predicted from SST observations ...

907 citations


Journal ArticleDOI
TL;DR: In this paper, the shape invariance of the spectral shape is exploited in a wave prediction model by projecting the full transport equation for the two-dimensional spectral continuum onto two variables characterizing the energy and frequency scales of the spectrum.
Abstract: Measurements of fetch-limited wave spectra from various sources indicate an approximate invariance of the normalized spectral shape with fetch. It has been suggested from investigations of the spectral energy balance that this can be explained by the shape-stabilizing influence of nonlinear resonant wave-wave interactions, which are also responsible for the migration of the spectral peak to lower frequencies. Analyses of a series of further data sets obtained under non-uniform, non-stationary wind conditions show that the invariance of the spectral shape is not restricted to uniform-wind, fetch-limited situations, but applies generally for a growing wind sea. The observed shape invariance is exploited in a wave prediction model by projecting the full transport equation for the two-dimensional spectral continuum onto two variables characterizing the energy and frequency scales of the spectrum. Inspection of the resultant equations reveals further simplifications, enabling the system to be reduced ...

434 citations


Journal ArticleDOI
TL;DR: In this paper, it was shown that the phase angle of the complex correlation coefficient is a good measure of the average relative angular displacement (veering) between a pair of two-dimensional vector series, and the correlation coefficient between the low-frequency (ω < 0.6 cpd) components of the current vectors at 20 m and 5 m heights from the ocean bottom at a station near the Oregon coast reveals an Ekman veering of 6°.
Abstract: It has been shown that the phase angle of the complex correlation coefficient is a good measure of the average relative angular displacement (veering) between a pair of two-dimensional vector series. The correlation coefficient between the low-frequency (ω<0.6 cpd) components of the current vectors at 20 m and 5 m heights from the ocean bottom at a station near the Oregon coast reveals an Ekman veering of 6°.

333 citations


Journal ArticleDOI
TL;DR: In this paper, an analysis of the low-frequency fluctuations of the currents near the Oregon coast is presented, based on the 1972 and 1973 measurements from moored current meters in CUEs 1 and CUE-2, where the mean alongshore velocity v has the structure of a baroclinic coastal jet, whose maximum speed occurs near the surface at a distance of about 15-20 km from the shore, whereas the fluctuating part of v has a roughly barotropic coastal jet whose maximum occurs very near the shore.
Abstract: An analysis is presented of the low-frequency fluctuations [ω<0.6 cycle per day (cpd)] of the currents near the Oregon coast, based on the 1972 and 1973 measurements from moored current meters in CUE-1 and CUE-2. Let u and v denote the eastward (approximately onshore) and northward (approximately alongshore) components of the currents. The mean alongshore velocity v has the structure of a baroclinic coastal jet, whose maximum speed occurs near the surface at a distance of about 15–20 km from the shore, whereas the fluctuating part of v has the structure of a roughly barotropic coastal jet whose maximum occurs very near (<4 km) the shore. The standard deviation of v is approximately depth-independent whereas that of u decreases with depth. As one approaches the coast, the standard deviation of u decreases whereas that of v rises steeply, consistent with the behavior expected of coastally trapped wave motion. A scatter plot of the velocity fluctuations in a hodograph plane indicates that the fluctu...

285 citations


Journal ArticleDOI
TL;DR: In this paper, the long-term mean heat balance of the earth and its normal seasonal variation are investigated over the Northern Hemisphere, based on the best presently available satellite radiation, atmospheric and oceanic data sets.
Abstract: Based on the best presently available satellite radiation, atmospheric and oceanic data sets, the long-term mean heat balance of the earth and its normal seasonal variation are investigated over the Northern Hemisphere. Quantitative estimates for the various flux and storage terms in the atmospheric and terrestrial branches of the heat balance are given for 10-deg-wide latitude belts and for each calendar month. The results are presented in both graphical and tabular form. As was known before, the storage of heat in the oceans is found to dominate the energy storage in the combined atmosphere-ocean-land-cryosphere system. In the tropics, large changes in oceanic heat storage are found in the 10 N-20 N belt with a maximum in spring and a minimum in late summer. The main new finding of this study is that the inferred oceanic heat transports appear to undergo very large seasonal variations especially in the tropics.

258 citations


Journal ArticleDOI
TL;DR: In this article, a model is used to follow the initial baroclinic response of the eastern Pacific Ocean to different distributions of interior wind stress change, and it is shown that changes in the meridional wind field outside of the equatorial band (roughly ± 5° of latitude) are not important in generating El Nino.
Abstract: El Nino is an anomalous condition that historically has been studied in the coastal region of the eastern tropical South Pacific. The phenomenon is commonly characterized there by the rapid appearance of anomalously high sea level and sea surface temperatures, and southward transport of the warmer, fresher equatorial waters. Observational evidence also suggests that El Nino is associated with a large-scale weakening of the equatorial wind systems over a large extent of the ocean interior. The problem investigated here is whether these ocean and atmosphere events are dynamically connected. A model is used to follow the initial baroclinic response of the eastern Pacific Ocean to different distributions of interior wind stress change. Model results suggest the following conclusions. Changes in the meridional wind field cannot cause an El Nino event. Changes in the zonal wind field outside of the equatorial band (roughly ±5° of latitude) are not important in generating El Nino. A symmetric weakening ...

243 citations


Journal ArticleDOI
TL;DR: In this article, an empirical orthogonal function analysis has been performed on monthly mean sea surface temperatures for the greater part of the Pacific Ocean between 55°N and 20°S. The analysis identifies the most important modes of seasonal and non-seasonal variability during the period 1949-73.
Abstract: An empirical orthogonal function analysis has been performed on monthly mean sea surface temperatures for the greater part of the Pacific Ocean between 55°N and 20°S. The analysis identifies the most important modes of seasonal and non-seasonal variability during the period 1949–73. A mode is defined spatially in terms of an empirical orthogonal function which describes the degree of coherence of variation. The function's corresponding coefficient portray the evolution of the mode in time. The seasonal variation is dominated by a mode having a 12-month periodicity and greatest coherence in the higher latitudes. A second important seasonal mode has a period of approximately 6 months and is dominated by deviations in the North Pacific. The most important non-seasonal variation is identified with the, long-recognized El Nino. The spatial pattern of this mode demonstrates the large-scale nature of the El Nino phenomenon. Other important non-seasonal modes are discussed.

222 citations


Journal ArticleDOI
TL;DR: In this article, the sensible heat and moisture fluxes by the bulk aerodynamic formulas were determined from a compilation of existing data, together with some new results, and the least square error fits were performed on the data.
Abstract: The parameterizations of the sensible heat and moisture fluxes by the bulk aerodynamic formulas are determined from a compilation of existing data, together with some new results. The data set comprised 152 determinations of the sensible heat flux and 30 of the moisture flux from experiments in which the fluxes were measured directly over water with suitable turbulence instrumentation. Least-square-error fits were performed on the data. The moisture flux (and therefore the latent heat flux) is adequately described by the bulk formula with a coefficient of 1.32 × 10−3. The parameterization of the sensible heat flux is complicated, for the data show 1) a small positive heat flux for zero temperature difference between the air and sea surface, 2) the coefficient for stable conditions is smaller than for unstable conditions, and 3) the coefficient appears to increase at high wind speeds, as shown by the data of Smith and Banke (1975). Separate bulk formulas are presented for the sensible heat flux fo...

187 citations


Journal ArticleDOI
TL;DR: The Weddell Sea is part of a large cyclonic gyre as mentioned in this paper, and a section taken across this gyre from the Scotia Ridge to Cape Norvegia shows that the Warm Deep Water forms an asymmetric lens-like structure with the thickest portion south of the center of the sea.
Abstract: The general circulation of water in the Weddell Sea is part of a large cyclonic gyre. A section taken across this gyre from the Scotia Ridge to Cape Norvegia shows that the Warm Deep Water forms an asymmetric lens-like structure with the thickest portion south of the center of the sea. This large-scale feature of the Weddell Sea is evidently due to a divergent Ekman flux driven by the general atmospheric circulation and upwelling in the center of the gyre. Vertical profiles of temperature and salinity in the center of the gyre show small step-like structures in the upper part of the transition from colder, less salty Winter Water to the warmer, saltier Warm Deep Water below and large step-like structures in the tower part of the transition region. Double-diffusive convection can take place in both regions. Circumstantial evidence leads one to believe that the cabbeling instability is effective in the large-step region. Internal waves and shear instabilities may also he mechanisms that contribute ...

159 citations


Journal ArticleDOI
TL;DR: In this article, a new mechanism, the breaking of internal waves, is proposed to explain vertical mixing within the lower layers of sill fjords, and the energy input into the internal waves and the damping of barotropic seiches are computed using linear theory.
Abstract: A new mechanism, the breaking of internal waves, is proposed to explain vertical mixing within the lower layers of sill fjords. The generation of the waves at the sill of a fjord is modelled assuming constant depth except at the narrow sill whose height is the thickness of the lower layer. A barotropic tide oscillating across the still creates internal waves which propagate both seaward and landward from the still. These waves break against the bottom, creating boundary turbulence which mixes water of different density in the lower layer. This is demonstrated experimentally. The mixture flows away from the boundaries into the interior of the fjord, causing an effective vertical mixing. The energy input into the internal waves and the damping of barotropic seiches are computed using linear theory. Possible instability, except at the bottom, is discounted by considering representative Richardson and Froude numbers. The theory is then qualitatively applied to the Oslofjord with particular attention ...

Journal ArticleDOI
TL;DR: In this article, an 8% increase in the frequency of the inertial peak (ω≈0.064 cph) above the local f was observed, indicating an upward propagation of phases throughout the water column, at a speed of about 0.1 cm s−1 within the depth range 20-60 m, but generally higher both above and below this mid-depth.
Abstract: Nearly two months of current meter data taken during the summer of 1973 at eleven depths at a station off the coast of Oregon in 100 m of water have been analyzed. The spectra show an 8% increase in the frequency of the inertial peak (ω≈0.064 cph) above the local f (=0.059 cph). Because of the close proximity of the tidal frequencies to the local f, a sharp bandpass filter centered at ω = 0.064 cph was used to isolate the inertial motions. The results showed that the amplitude of the inertial oscillations decayed slowly with depth, but the decay within about 10 m of the bottom was more rapid. A lagged correlation of the inertial currents clearly showed an upward propagation of phases throughout the water column, at a speed of about 0.1 cm s−1 within the depth range 20–60 m, but generally higher both above and below this mid-depth. The inertial currents were found to turn clockwise (looking down) with depth, which corresponds to an upward phase and downward energy propagation, and the vertical pha...

Journal ArticleDOI
TL;DR: In this article, the theory of coastal-trapped waves is extended to include the general features of continuous density stratification, variable bottom topography, and a finite coastal wall.
Abstract: The theory of coastal-trapped waves is extended to include the general features of continuous density stratification, variable bottom topography, and a finite coastal wall. In the limit of a vanishing coastal wall, topographic Rossby waves are the only class of sub-inertial frequency, trapped wave motion. The stratification effect on topographic Rossby waves depends on both the local baroclinic radius of deformation and the characteristic offshore length scale of the wave motion. For intermediate density stratification, long waves are nearly depth-independent in the shelf region, and are bottom-trapped in the slope region. The topographic Rossby waves reduce to the barotropic shelf waves and the bottom-trapped waves in the limits of small and large density stratification, respectively. In the general case of comparable influences from the coastal wall and bottom slope effects, baroclinic Kelvin waves and topographic Rossby waves are eigenmodes of the system. The eigenfunctions are modified from t...

Journal ArticleDOI
TL;DR: In this article, the frontal zone of the coastal upwelling region off Oregon, from observations made in two successive years, was determined by combining direct measurements and geostrophic calculations, and the cross-stream flow was estimated to be seaward near the surface, shoreward at the top of the inclined frontal layer.
Abstract: We studied the frontal zone of the coastal upwelling region off Oregon, from observations made in two successive years. The measurements were made between July and September in 1965 and 1966. The alongshore flow field was determined by combining direct measurements and geostrophic calculations. A near-surface southward jet and a subsurface northward undercurrent existed in the frontal zone. They were separated by an inclined frontal layer (permanent pycnocline). The frontal layer tended to intersect the sea surface about 10 km offshore, where a surface front was formed. Through a combination of direct current measurement and water mass analysis, the cross-stream flow was estimated to be seaward near the surface, shoreward at the top of the inclined frontal layer, but seaward at the bottom of the inclined frontal layer and shoreward below that. During a 25 h anchor station, a high degree of correlation existed between the vertical structure of the alongshore and cross-stream flows. An anomalously ...

Journal ArticleDOI
TL;DR: In this article, the authors tested the hypothesis that these rare events occur after a substantial reduction of the atmospheric trade winds over the central Pacific Ocean, and found that the rapid downwelling and the sudden reversal of the coastal current are consistent with observations during El Nino.
Abstract: El Nino may be defined oceanographically as a massive influx of warm water into the coastal region of Ecuador and Peru. We have tested the hypothesis that these rare events occur after a substantial reduction of the atmospheric trade winds over the central Pacific Ocean. An idealized nonlinear, two-layer, equatorial beta-plane ocean is spun-up with easterly winds for 50 days after which the wind is relaxed over several days. The relaxation of the wind initiates internal Kelvin wave fronts at both sides of the ocean at the equator. The eastern wave fronts propagate poleward and the western ones eastward. Internal Rossby waves are generated which propagate westward from the eastern boundary. As the Kelvin wave fronts move poleward along the eastern boundary, strong downwelling occurs and the coastal currents reverse direction and become poleward. The rapid downwelling and the sudden reversal of the coastal current are consistent with observations during El Nino. This downwelling is much more rapid ...

Journal ArticleDOI
TL;DR: In this article, a 51-day velocity record measured 2 m from the bottom of the Providence River (a partially mixed estuary) was used to examine wind-induced velocity fluctuations at time scales between the steady state gravitational convection and the tidal oscillations.
Abstract: Atmospherically driven flow in the Providence River (a partially mixed estuary) has been examined using a 51-day velocity record measured 2 m from the bottom. Velocity fluctuations at time scales between the steady-state gravitational convection and the tidal oscillations were large and almost exclusively wind-induced. The mean and variance of the velocity component lying along the channel axis were 11.7 cm s−1 (landward) and 166.9 cm2 s−2. Of this axial current variance 48% resided at subtidal frequencies as compared to 45% associated with semidiurnal tides (the remaining 7% was mostly due to higher tidal harmonies). Over the most energetic portion of the axial current spectrum (periodicities of 4–5 days), 97% of the variance was coherent with the wind velocity component lying along the direction of maximum fetch, with the current lagging the wind by about 4 h. Owing to this extremely high coherence, a linear time-invariant stochastic model reproduced the axial current from the two orthogonal wi...

Journal ArticleDOI
TL;DR: In this article, the effects of bottom topography and coastline configuration on the onset and decay of the ocean upwelling circulation were investigated by using the wind driven, x-y-t, two-layer β-plane numerical model developed by Hurlburt (1974).
Abstract: The wind driven, x-y-t, two-layer β-plane numerical model developed by Hurlburt (1974) is used to investigate the effects of a bottom topography and coastline configuration, like that off Oregon, on the onset and decay of the ocean upwelling circulation. The digitized nearshore Oregon bathymetry is analyzed for dominant scales, and a smoothed version is used in model cases with several different initial states and wind stresses. Cases with topography are compared to cases with plane sea beds. Topographic variations are found to dominate over coastline irregularities in determining the longshore distribution of upwelling. Results indicate that stronger upwelling observed near Cape Blanco is primarily due to the local bottom topography and not the cape itself. Observed variations in the meridional and zonal flow are attributed to the topographic β-effect. In particular, during spin-up with an equatorward wind stress, a nearshore poleward undercurrent is most likely to develop in regions where topog...

Journal ArticleDOI
TL;DR: In this paper, a model of the thermally mixed layer in the upper ocean was further extended to investigate the effects of salinity in the tropical and subtropical Atlantic Ocean, where rapid increases in salinity occur at the bottom of a uniformly mixed surface layer.
Abstract: A model of the thermally mixed layer in the upper ocean as developed by Kraus and Turner and extended by Denman is further extended to investigate the effects of salinity. In the tropical and subtropical Atlantic Ocean rapid increases in salinity occur at the bottom of a uniformly mixed surface layer. The most significant effects produced by the inclusion of salinity are the reduction of the deepening rate and the corresponding change in the heating characteristics of the mixed layer. If the net surface heating is positive, but small, salinity effects must be included to determine whether the mixed layer temperature will increase or decrease. Precipitation over tropical oceans leads to the development of a shallow stable layer accompanied by a decrease in the temperature and salinity at the sea surface.

Journal ArticleDOI
TL;DR: The mean and turbulent flow structure under pack ice was measured during the 1972 AIDJEK pilot study with small mechanical current meter triplets at eight levels in the planetary boundary layer as discussed by the authors.
Abstract: The mean and turbulent flow structure under pack ice was measured during the 1972 AIDJEK pilot study with small mechanical current meter triplets at eight levels in the planetary boundary layer. CTD profiles showed a well-mixed layer of nearly neutral stability to about 35 m, bounded below by a strong pycnocline. The skin friction velocity u* was determined by measuring the Reynolds stress at 2 and 4 m below the ice (beyond the surface layer) and from consideration of other terms in the mean momentum equation. Local pressure gradients and advective acceleration due to topography could not be ignored; when an estimate of the effect was included, u* was 1.0±0.1 cm s−1 when the ice velocity relative to the ocean was 24 cm s−1. With the proper coordinate transformation, the planetary boundary layer of the ocean resembles that of the atmosphere. Composite averages of non-dimensional Reynolds stress and mean flow in the ocean, when compared with recent models of a neutrally buoyant, horizontally homoge...

Journal ArticleDOI
TL;DR: In this article, three slab models of the surface mixed layer of the ocean are given simple and fast computer implementations, and actual meteorological data from Ocean Weather Station N are used for a year-long forecast.
Abstract: Three slab models of the surface mixed layer of the ocean are given simple and fast computer implementations. Actual meteorological data from Ocean Weather Station N are used for a year-long forecast. The results compare quite well with the observations of vertical temperature profiles, with correlations up to 0.98 between predicted and observed sea-surface temperature and of 0.8 between predicted and observed mixed-layer depths. Temperature anomalies introduced in the spring can be covered up in the summer, yet reappear in the winter. A constant-thickness slab is suitable as a lower boundary for some atmospheric climatological studies, if a depth of 25 m is used. The model based on a Foude number criterion worked best for the available data set; this is physically appealing since the model contains no adjustable parameters.

Journal ArticleDOI
TL;DR: In this article, a quasi-geostrophic two-layer model for channel flow with a sloping bottom is developed to explain the low-frequency variability, using measured values of shear and other physical parameters, the model is found to be unstable over a limited range of wavelengths and frequencies.
Abstract: Current meter records and hydrographic data taken in the Denmark Strait overflow during a one-month experiment in August-September 1973 are analyzed. Mean conditions indicate that a strong, cold overflow current existed throughout the experiment. The most outstanding feature of the velocity and temperature spectra is a strong peak at a period of 1.8 days. These oscillations appear to amplify in the downstream direction and are highly correlated over the entire flow at the southern end of the Strait. Phase estimates indicate that velocity components are in quadrature, while the cross-stream perturbation heat flux acts to reduce the mean potential energy associated with the sloping isotherms. To explain the low-frequency variability, a quasi-geostrophic two-layer model for channel flow with a sloping bottom is developed. Using measured values of shear and other physical parameters, the model is found to be unstable over a limited range of wavelengths and frequencies. The most unstable wave is 80 km...

Journal ArticleDOI
TL;DR: In this paper, the vertical profiles of horizontal ocean currents are used to study the vertical structure and temporal behavior of internal waves in the ocean, particularly those near the local inertial frequency.
Abstract: Vertical profiles of horizontal ocean currents are used to study the vertical structure and temporal behavior of internal waves in the ocean, particularly those near the local inertial frequency. The polarization, or direction in which the horizontal velocity vector of an internal wave rotates with depth, is an important feature of the vertical structure, since it provides information on the direction and magnitude of the vertical wave energy flux. Analysis of a time series of profiles at one location over smooth topography shows that the observed wave polarization and phase propagation in the vertical are consistent, at least within the limits of the observational technique that was employed, with the linear dispersion relation for internal waves. The fact that the waves are polarized in the clockwise sense with increasing pressure shows that they have a net downward energy flux. A spectral decomposition of the profiles into clockwise and anti-clockwise components provides an estimate of 0.2–0.4...

Journal ArticleDOI
TL;DR: In this article, the vertical distribution of horizontal velocity was observed in the West Passage using moored current meters and the instantaneous motion was characterized by semi-diurnal tidal currents of amplitude 25-60 cm s−1.
Abstract: Narragansett Bay is a weakly stratified estuary comprised of three connecting passages of varying depths. The vertical distribution of horizontal velocity was observed in the West Passage using moored current meters. The instantaneous motion was characterized by semi-diurnal tidal currents of amplitude 25–60 cm s−1. These currents exhibited a phase advance with depth (total water depth=12.8 m) ranging with lunar phase from 0–3 h. The net current time series obtained by filtering out motions at tidal and higher frequencies were found to be an order of magnitude less than the instantaneous motion and well correlated to the prevailing 2–10 m s−1 winds. For periodicities of 2–3 days, the coherence between the longitudinal components of wind and net near surface current was as high as 0.8 with the current lagging the wind by about 3 h. The mean near surface speed, obtained by averaging over one month, was 1.2±1.6 cm s−1. The large error bounds were a result of the large variability of the net current ...

Journal ArticleDOI
TL;DR: In this article, a slug of water-soluble rhodamine dye solution was introduced at appropriate depths to study large-scale horizontal diffusion characteristics of fluorescent dye patches in Lake Ontario, where the growth of the diffusing dye patch was followed up to 80 h after dye release using fluorometric sampling.
Abstract: Experimental data on the diffusion of fluorescent dye patches were obtained in Lake Ontario, to study large-scale horizontal diffusion characteristics. In each experiment, a slug of water-soluble rhodamine dye solution was introduced at appropriate depths. The growth of the diffusing dye patch was followed up to 80 h after dye release, using fluorometric sampling. The data covered a length scale (i.e., patch size) of 100 m to 15 km and the corresponding eddy diffusivities varied from 102 to 106 cm2 s−1. Several horizontal diffusion characteristics are constructed based on a simple theoretical framework. Although the diffusion characteristics cannot be justified entirely from theoretical arguments, they could be viewed as purely statistical since they have been constructed from experimental data obtained in widely varying environmental conditions and provide useful guidelines for modeling practical diffusion problems.

Journal ArticleDOI
TL;DR: In this paper, vertical profiles of temperature microstructure in Lake Kivu were obtained with mini-microstructure recorders developed by C.S. Cox and William Johnson at Scripps Institution of Oceanography, revealing three depth intervals containing many isothermal layers typically 0.25-2 m thick and of increasing temperature increments 0.01-0.03°C from layer to layer.
Abstract: Vertical profiles of temperature microstructure in Lake Kivu were obtained with “mini-microstructure recorders” developed by C.S. Cox and William Johnson at Scripps Institution of Oceanography. The profiles reveal three depth intervals containing many isothermal layers typically 0.25–2 m thick and of increasing temperature increments 0.01–0.03°C from layer to layer. Approximately 150 such layers appear in a single profile. We assume double-diffusive convection and apply the results of Huppert and of Turner to calculate an upward heat flux of 0.71 to 1.6 W m−2 and a corresponding upward salt flux equal to one-fifth of the average salt output of the lake's only outflow. The chief source of heat and salt is probably geothermal springs in the lake bottom.

Journal ArticleDOI
TL;DR: In this article, the mean of the measured currents was 25 cm s−1 toward the northeast, such that water moved out of the canyon from the Chukthi Sea toward the Arctic Ocean.
Abstract: Simultaneous current and temperature measurements were made at two depths in Barrow Canyon for a period of 120 days from April through August, 1973. The mean of the measured currents was 25 cm s−1 toward the northeast, such that water moved out of the canyon from the Chukthi Sea toward the Arctic Ocean. The measurements, however, are characterized by higher speeds, commonly in excess of 50 cm s−1, and large variations which resulted in periods of reversed (southwest) up-canyon motion. During these reversed flow periods increased temperatures indicate the presence in the canyon at 126 m depth of Atlantic Water from 200–300 m depth in the Arctic Ocean. A close relationship exists between the measured currents and the north-south atmospheric pressure gradient, such that when the pressure rose to the north, the northward flow of water through the canyon decreased. A simple dynamic model is presented to account for the observed current-pressure relationship.

Journal ArticleDOI
TL;DR: In this article, an analytical expression of the internal wave spectra and coherences is presented, based on a variant of the Garrett and Munk (1975) model, and the change is from a slope of −2.5 to −2 in wavenumber spectra, as suggested by recent measurements.
Abstract: Analytical expressions of internal wave spectra (and coherences) are presented, based on a variant of the Garrett and Munk (1975) model. The change is from a slope of −2.5 to −2 in wavenumber spectra, as suggested by recent measurements. This proves convenient analytically. The final results depend on one ocean parameter n/f, the ratio of buoyancy to inertial frequency; and two model parameters corresponding to energy level and bandwidth. There is no need to assume an exponential dependence of the buoyancy frequency with depth. The properties of coherence measured along characteristics are also discussed.

Journal ArticleDOI
TL;DR: In this article, the changes in the circulation and hydrographic structure over the continental shelf south of Tema, Ghana, during the 1974 upwelling are described, and no simple driving mechanism is apparent.
Abstract: The changes in the circulation and hydrographic structure over the continental shelf south of Tema, Ghana, during the 1974 upwelling are described. For the first time in this region an Aanderaa current meter mooring provided a continuous record of currents at three levels. During the onset of the upwelling there is evidence of a vertical flow of 8 × 10−5 m s−1 and an offshore flow at the surface of 7 × 10−2 m s−1. A large vertical shear, which is a permanent feature throughout most of the year, vanishes during the upwelling. Sea level changes are predominantly steric in origin. The upwelling event and the subsequent changes in the hydrography and circulation do not correlate with changes in the coastal wind. These are important differences between the Ghana regime and that observed in other coastal upwelling areas, and no simple driving mechanism is apparent. As a result, existing theoretical models may not be applicable. The possibility that waves of oceanic origin play an important role in the ...

Journal ArticleDOI
TL;DR: In this paper, the total dynamic pressure (or, in the geostrophic approximation, stream function) has been constructed for different vertical levels and time periods by the interpolation technique of objective analysis.
Abstract: From measurements made during the 1973 Mid-Ocean Dynamics Experiment in the western North Atlantic, horizontal maps of the total dynamic pressure (or, in the geostrophic approximation, streamfunction) have been constructed for different vertical levels and time periods by the interpolation technique of objective analysis. The space and time sampling of the observations—several tens of kilometers horizontally, hundreds of meters vertically and several days in time—were adequate for resolving mesoscale eddies. The data consisted of velocities (displacement rates) at 1500 m depth from neutrally buoyant floats and vertical density profiles throughout the water column. The resulting maps have been considered from several, essentially phenomenological, points of view. These include descriptions of the synoptic eddy structure, the time evolution and propagation of the eddies, the adequacy of linear modal vertical structure, and the correspondences and energy partition between motions in the two vertical...

Journal ArticleDOI
TL;DR: In this article, internal wave records from a variety of deep water locations in the North Atlantic have been reduced by common analysis methods in search for systematic deviations from a universal spectral model such inhomogeneities are probably necessary conditions for sources and sinks of the motion.
Abstract: Internal wave records from a variety of deep water locations in the North Atlantic have been reduced by common analysis methods in a search for systematic deviations from a universal spectral model Such inhomogeneities are probably necessary conditions for sources and sinks of the motion For a number of reasons, only records at 2000 m and below were used Real variations in energy level of up to an order of magnitude were found, but the only clear inhomogeneities are associated with bottom topography, especially in those records obtained near Muir seamount The effects, if any, on the internal wave field by the large velocity and shear of the Gulf Stream region are weak Apparent topographic sources are inconspicuous at very short distances, suggesting a very rapid, nonlinear recovery of the spectrum to an equilibrium form