bluuebunny/crossref_metadata_2025 huggingface dataset:
Factors influencing the degree of saturation of the surface and intermediate waters of the North Pacific Ocean with respect to aragonite
Authors: Feely Richard A. , Byrne Robert H. , Betzer Peter R. , Gendron James F. , Acker James G.
Published: February 2008

New carbonate chemistry data obtained during a 1982 cruise have been combined with earlier GE‐OSECS and INDOPAC data to determine the degree of aragonite saturation of surface and intermediate waters of the North Pacific. Large gradients in saturation state occur in the region of the Subarctic Front in the north‐south direction and across the Subtropical Gyre in the east‐west direction. These gradients are primarily due to the extensive mixing that occurs in the intermediate waters of the western North Pacific. The major variations in saturation state were primarily related to the carbonate ion concentration, which, in turn, is primarily a function of mixing and biological processes. The present aragonite saturation depth at our northernmost station in the western North Pacific was calculated to be within 120 m of the surface. This result was directly corroborated by observations of aragonite dissolution under in vitro conditions. Our calculations show that one possible effect of fossil fuel‐derived CO2 on the surface of the North Pacific will be a steady progression of undersaturation from the northern to southern and western areas, with the first sign of undersaturation possibly occurring as early as the second half of the next century.
Near equatorial CTD observations at 85°W in October 1982
Authors: Toole John M.
Published: February 2008

CTD data collected about the equator along 85°W between October 8 and 12, 1982, are used to investigate stratification changes in the upper 1 km associated with the 1982/83 El Niño. With respect to the thermal field observed in November 1981, virtually the entire section exhibited downward displacements in the upper kilometer of the water column. Observed displacements at the depth of the mean thermocline were large (∼150 m) and relatively symmetric about the equator. Displacements around 1 km depth were near zero. This stratification change appears to have been produced by a zonal convergence of mass at temperatures above 15°C, with divergence below. Least square modal decompositions of the vertical displaced profiles revealed significant contributions from modes 1 and 2 with meridional structure consistent with Kelvin waves. The observations thus support current theories that relate El Niño onset in the eastern Pacific to anomalous wind forcing in the west.
Observations of surf beat
Authors: Guza R. T. , Thornton Edward B.
Published: February 2008

The magnitudes of cross‐shore velocity and elevation oscillations at surf beat frequencies observed on three ocean beaches are significantly correlated with the significant height of incident wind waves. Measured surf beat run‐up spectra are coupled with numerical integrations of the long wave equations to predict the energy spectrum at offshore sensors, and the coherence and phase between offshore sensors and run‐up meter. As in previous studies, valleys in the observed surf beat energy spectra at offshore sensors, and jumps in the relative phase between sensors, occur at the nodal frequencies of simple standing wave (either leaky or high mode edge wave) models. The variance observed in the surf beat cross‐shore velocity field is between 10 and 100 times larger near the shoreline than in 5 m depth, and decays more rapidly with increasing offshore distance than the variance in the surf beat elevation field. The standing wave model is qualitatively consistent with this structure.
Numerical simulation of northern hemisphere sea ice variability, 1951–1980
Authors: Walsh John E. , Hibler William D. , Ross Becky
Published: February 2008

The dynamic‐thermodynamic sea ice model of Hibler (1979) is used to simulate northern hemisphere sea ice growth, drift, and decay over a 30‐year period, 1951–1980. The model is run with a daily time step and is forced by interannually varying fields of geostrophic wind and temperature‐derived thermodynamic fluxes. The results include documentation of the sensitivities to the source of the thermodynamic forcing data and to the number of thickness levels in the thermodynamic formulation. The fields of ice velocity and thickness show strong seasonal as well as interannual variability. The Pacific gyre is found to be well‐developed in spring and autumn but less so in winter and summer. The mean drift pattern results in thicknesses of 4–5 m offshore of northern Canada and Greenland, while winter thicknesses of ∼2 m are typical of the Alaskan and Eurasian coastal waters. Annual net growth ranges from 0.1 to 0.6 m over much of the Arctic Basin and Baffin Bay to over 1.0 m in the eastern Bering Sea. Annual net melt of 0.5–1.5 m occurs in the western Bering Sea and the North Atlantic marginal ice zone. No significant temporal trends are detectable in the total mass of simulated ice. The simulated interannual fluctuations in 20° longitudinal sectors correlate at 0.4–0.9 with corresponding observed fluctuations during 1961–1976. The correlations are smaller when dynamics are omitted from the model. The simulated velocities show no bias but considerable scatter relative to the drift of the Arctic buoys in 1979 and 1980. An analysis of the regional mass budgets shows that the normal seasonal cycle is controlled primarily by the thermodynamic processes but that the thickness anomalies in much of the Arctic are attributable primarily to dynamic processes during winter, spring, and autumn. Thermodynamic processes contribute more strongly to summer anomalies and to anomalies near the ice edge. The tendency for ice anomalies to be advected by the pattern of mean drift is apparent in multiseason lag correlations involving subregions of the Arctic Basin and the peripheral seas. The simulated outflows of ice mass through the Fram and Bering straits vary by factors of 2–3 in successive years. The simulated outflow in the Fram Strait is 20–30% smaller when ocean currents are omitted from the model.
Stratification and shelf‐slope interaction in the Middle Atlantic Bight: A numerical study
Authors: Aikman Frank , Posmentier Eric S.
Published: February 2008

A one‐dimensional, two‐layer, bulk‐mixing model, driven by the climatic inputs of heat, fresh water, and wind, simulates the predominant evolving thermohaline characteristics of the shelf and slope waters in the Middle Atlantic Bight. The inclusion of sea surface temperature‐dependent heating and implicit “lateral fluxes” has proven important to the model sensitivity and accuracy. The shape of the Margules frontal boundary separating shelf and slope waters depicts the transition from a monotonically sloping front of winter to the convoluted shape of summer, and suggests that the shelf‐slope frontal shape is primarily density controlled. Cross‐frontal diffusive fluxes of heat and salt are calculated, and their importance in relationship to features of the stratification such as the cold pool and the pycnocline salinity maximum intrusion is evaluated. The calculated cross‐frontal salt fluxes are found to contribute a major part to the shelf water and cold pool salt budgets. Sensitivity studies establish that the model is most sensitive to parameters related to cross‐pycnocline diffusion and that reasonable values of these parameters lead to simulations which agree with hydrographic observations. Further sensitivity studies show that, as expected, interannual variations in runoff should cause observable variations in shelf salinity, and that variations of wind speed should also cause significant hydrographic changes, but that the sea surface temperature is only moderately sensitive to air temperature variations.
Distribution and flux of 226Ra and 228Ra in the Amazon River estuary
Authors: Key R. M. , Stallard R. F. , Moore W. S. , Sarmiento J. L.
Published: February 2008

Measurements of 226Ra and 228Ra in the Amazon River estuary show that desorption from river‐borne suspended particulate matter in the estuary increases the riverine flux of both isotopes to the ocean by a factor of approximately 5 over the flux attributable to radium dissolved in the river water alone. The total Amazon flux supplies approximately 0.20% of the 226Ra and approximately 2.6% of the 228Ra standing crops in the near‐surface Atlantic (0–200 m). Diffusive flux from estuarine and shelf sediments and desorption from resuspended sediments in the region of the estuary approximately double the estuarine 226Ra concentration and quadruple the estuarine 228Ra concentration above that caused by the dissolved and desorbed river components alone.
Wave refraction by warm core rings
Authors: Mapp George R. , Welch Christopher S. , Munday John C.
Published: February 2008

A numerical model for refraction of ocean swell by currents associated with a warm core ring was developed and tested with Seasat synthetic aperture radar (SAR) data. The wave field of SAR orbit 1232 was measured using optical Fourier transforms. The wave refraction model produced rays by simultaneous, numerical integration of the Hamiltonian ray equations applied to a moving medium. Wave orthogonals were constructed from wave number vectors calculated at each incremental time step. The flow field used by the model to simulate a warm ring was a steady, circular jet, with the radial profile of tangential velocity composed of a power function joined to a Gaussian. Initial wave conditions for simulation of refraction by the SAR‐imaged ring were determined from measurements outside the ring. No data were available from which to determine the current field of the SAR‐imaged ring, so the current field input to the model was adjusted until the output wave field most nearly resembled the SAR observations. The relative locations of convergence and divergence of rays were as observed on the SAR image, and the relative energy density in crossed seas was correctly predicted. However, predicted patterns of wavelength variation (presuming that incident waves were uniform in wavelength) were not observed.
Some features of the Algerian Current
Authors: Millot Claude
Published: February 2008

An analysis of infrared images leads to a new conception of the dynamics of the Atlantic Water in the Algerian Basin. In situ current measurements are not yet available, but coherent hypotheses are presented with the aim to initiate further experimental and theoretical works. The Algerian Current flows steadily along the coast near 0° and becomes unstable near 1–2°E. Eddies of both signs are generated that are advected by the mean current, but only the anticyclonic eddies increase in size (diameter about 100 km). As they extract more energy from the mean current they are advected more slowly, and they may detach from the coast and drift for several weeks in the Algerian Basin. They grow as deep as 1000m at least, and they are able to pull lenses of Intermediate Water seaward from the Sardinian continental slope. Coastal upwelling cells are generated near 1–2°E between the cyclonic and the anticyclonic eddies; they are also advected by the mean current and are definitively not wind induced. These turbulent structures create intense mixing between the Atlantic and Mediterranean waters, which account for the large eastward gradient of salinity encountered in the surface layer. Therefore the Algerian Basin is characterized by a large mesoscale variability mainly due to the instability of the Algerian Current. It appears to be a reservoir in which the water of Atlantic origin is amassed, and it forms a buffer zone which disconnects the flow of Atlantic Water coming in at Gibraltar from the flow of hygly modified Atlantic Water exiting the basin through the Strait of Sardinia and into the Ligurian Sea.
A note on the internal Kelvin waves generated by tidal flow over a two‐dimensional ridge in a rotating fluid
Authors: Liu Y. N. , Maxworthy T.
Published: February 2008

A number of experiments on the internal Kelvin waves generated by tidal flow over a two‐dimensional ridge have been performed in a long, narrow rotating tank. The plan form, phase speed, amplitude, and induced velocity of the internal Kelvin waves were observed for several tidal periods, tank rotation rates, and density differences.
A two‐layer diagnostic model of the long‐term physical evolution of warm‐core ring 82B
Authors: Olson D. B. , Schmitt R. W. , Kennelly M. , Joyce T. M.
Published: February 2008

Shipboard data from cruises in the 1982 time series on a single Gulf Stream warm‐core ring are composited in a cylindrical coordinate system following the motion of the ring. Measurements of 10°C isotherm depth are used with a two‐layer model of the ring's structure to compute gradient current, kinetic energy, available potential energy (APE), and potential vorticity in the ring, The momentumrelated quantities are compared with surface‐derived velocity measurements by using an acoustic Doppler log (APOC; Joyce and Kennelly, this issue). The volume of waters carried with the ring are also computed on the basis of thermal data. The changes in these quantities as the ring evolves are discussed. The evolution of the ring can be divided into two periods. The first, from April to late June, while the ring is isolated from strong interactions with the Gulf Stream, is associated with slow changes in ring properties. During this period, the ring loses APE at a rate of 94×106 W (94 MW). Kinetic energy is constant within the measurement errors. Ring volume for waters warmer than 10°C decreases at 0.04×106 m3 s−1 (0.04 Sv). A shift in ring volume out to larger radius is observed. After this interval the ring is involved in several interactions with the Gulf Stream and topography. Ring energy is lost at rates exceeding 900 MW. The ring volume is diminished at 1.4 Sv during the July period. Within the measurement errors, however, the potential vorticity at the center of the ring is conserved from April through August, implying nearly inviscid dynamics.
Statistics for the evaluation and comparison of models
Authors: Willmott Cort J. , Ackleson Steven G. , Davis Robert E. , Feddema Johannes J. , Klink Katherine M. , Legates David R. , O'Donnell James , Rowe Clinton M.
Published: February 2008

Procedures that may be used to evaluate the operational performance of a wide spectrum of geophysical models are introduced. Primarily using a complementary set of difference measures, both model accuracy and precision can be meaningfully estimated, regardless of whether the model predictions are manifested as scalars, directions, or vectors. It is additionally suggested that the reliability of the accuracy and precision measures can be determined from bootstrap estimates of confidence and significance. Recommended procedures are illustrated with a comparative evaluation of two models that estimate wind velocity over the South Atlantic Bight.
Measurements of total alkalinity, calcium, and sulfate in natural sea ice
Authors: Anderson Leif G. , Jones E. Peter
Published: February 2008

We report precise measurements of salinity, chlorinity, alkalinity, calcium, and sulphate in various types of sea ice collected at the Canadian Expedition to Study the Alpha Ridge (CESAR) Ice Camp in the Arctic Ocean and in both first‐year and multiyear ice collected in Fram Strait. Several of the samples showed some relative enrichment of alkalinity and sulphate compared to what would be observed in seawater of the same salinity. The relative enrichment was quite varied and did not correspond quantitatively with what has been observed in sea ice produced in the laboratory. Our results indicate that the temperature and salinity history of sea ice must be crucial in determining the relative composition of salts in natural sea ice and that quantitative geochemical predictions based on the composition of sea ice produced in the laboratory or on a particular specimen of natural sea ice must be made with caution.
Gyre‐scale acoustic tomography: Biases, iterated inversions, and numerical methods
Authors: Spiesberger John L.
Published: February 2008

Travel times of acoustic ray paths are computed between a source and a receiver placed at mid‐depth at a range of 1000 km. The times are computed for a smooth reference profile and for a profile containing a mesoscale eddy field. The differences between the travel times for the reference and “eddy‐populated” fields are used to iterate a linearized model (Wiener filter) of the sound‐slowness field. The model is iterated until it fits the data. The final iterate, however, is statistically inconsistent with the correct result according to error bars computed from linear theory. At long ranges the travel times are biased by the eddy field. The bias is small (but not insignificant) compared with the travel time fluctuations arising from climatological fluctuations of the ocean. A correction for the bias is used to compute a model that fits the data and is statistically consistent with the correct result. In addition, a numerical technique is described that significantly reduces the computation required for the Wiener filter in this application.
Ice drift and regional meteorology in the southern Bering Sea: Results from MIZEX West
Authors: Reynolds Michael , Pease C. H. , Overland J. E.
Published: February 2008

In February 1983 a multifaceted study of the air‐ice‐ocean interaction was made in the southern Bering Sea. The study, MIZEX West, addressed a broad spectrum of physical problems related to the Bering Sea marginal ice zone (MIZ). As a part of that study an array of eight Argos‐tracked floes on a scale of 50 km provided information on the mesoscale behavior of the ice pack. Wind and current measuring platforms on two of the floes gave detailed information on the forces on individual floes which were compared with the larger‐scale motions. Under relatively steady northeast winds and with weak or negligible regional currents, the floes accelerated considerably as they crossed the MIZ. The array showed little distortion, even though it skirted around St. Matthew Island and changed trajectory direction by over 90° during the 12‐day study period. Similarly, individual floes remained within 20° of their original orientation, although their angular motions were erratic and often rapid. A baroclinicly forced acceleration of the wind over the MIZ contributed to floe acceleration. The relative currents at 2 and 6 m under the ice were highly variable and random in time, although well correlated in depth. One of the floes was much smoother than the other, and higher winds and currents were noted at the smoother floe. The motion of the floes reflect strong coupling to the currents at tidal and lower frequencies and low‐frequency (greater than 6 hours) response to the wind. Both floes drifted to the right of the mean wind by approximately 30° at about 4% of the wind speed at 3 m, and relative wind and current directions were within 20° of being colinear, traits that are consistent with free drift hypothesis. Using quadratic drag representations for wind and current stress, the near colinearity allowed calculation of the ratio of the air/ice to ice/water drag coefficients, Ca/Cw, relative to measurement heights of 3 m and −2 m. For the rough floe this ratio changed in mean from 0.06 to 0.2 in its movement to the MIZ. For the smooth floe the variation in the ratio was less, from 0.14 to 0.2. However, for the rough flow the angle between wind and current was generally less than 180°, and for the smooth flow it was greater. It is possible that another type of drag related to the bow effect of the floe pushing through the water can account for this observation. Finally, the motion of the ice floes and ice edge are compared by examination of satellite photos. Two regions of the ice pack—one thick with rafting and rubble, one thin and broken—showed a ratio of edge velocity to floe velocity of 0.64 and 0.43, respectively. Thinner ice overtakes the edge and melts more rapidly than the thicker ice. A simple thermodynamic model explains this observation.
The impact of Seasat‐A scatterometer data on the numerical prediction of the Queen Elizabeth II storm
Authors: Duffy D. G. , Atlas R.
Published: February 2008

The development of the Queen Elizabeth II storm from 1200 UT on September 9, 1978, to 0000 UT on September 11, 1978, is forecast with a limited‐area, fine resolution (100 km) numerical weather prediction model. Forecasts from initial conditions that include and exclude Seasat scatterometer surface winds are performed. When the Seasat winds are allowed to influence the upper levels of the atmosphere, a large positive impact is found.
An analysis of errors in sea surface temperature in a series of infrared images from NOAA 6
Authors: Kelly K. A. , Davis R. E.
Published: February 2008

As part of the Coastal Ocean Dynamics Experiment, 58 infrared satellite images were analyzed for the magnitude and source of their errors in predicting sea surface temperature. Comparisons with near‐surface thermistors on moorings and differences between images from consecutive days showed that a two‐channel atmospheric correction using the 3.7‐μ m and the 11‐μ m channels was ineffective in reducing errors. Large systematic errors, which have the form of a constant over an image, were found in both channels. A simple viewing angle correction reduced fluctuations in the area‐mean 11‐μ m channel temperature from 0.74° to 0.45°C; a satisfactory correction could not be found for the larger fluctuations in the 3.7‐μ m channel, which appears to be degraded by reflected or scattered solar radiation. By taking account of the known dependence of atmospheric effects on viewing angle geometry, it was possible to isolate the primary causes of error, to estimate typical magnitudes, and to correct for them. The 11‐μ m channel temperature error from the northern California atmosphere was found to be nearly constant in time over a 100‐day period, but to vary slowly with distance from the coast.
A surface density and wind‐driven model of the thermocline
Authors: Janowitz G. S.
Published: February 2008

A simple analytical model is used to determine the density and flow fields in the subtropical gyre. The flow, which is taken to be steady, nondiffusive, and in geostrophic balance, is driven by a vertical velocity induced by the overlying convergent Ekman layer and a specified surface density field. The thermocline region, in which the density increases continuously with depth, overlies a stagnant homogeneous layer. It is shown that if the surface density increases monotonically to the north along the eastern boundary, where the zonal transport is taken to vanish, then the thermocline depth increases monotonically to the north; this implies westward flow (outflow) at the eastern boundary near the thermocline base with compensating inflow occurring higher in the water column. Although the model is formulated for a general specified surface density field, some general conclusions are reached for surface density fields which vary with latitude alone. It is shown that in this case the simplest and possibly the only choice of the potential vorticity is a function of density divided by the Bernoulli function. For this potential vorticity function, density profiles are similar at each latitude, and the potential vorticity is a minimum at the core of recirculating regions. A specific surface density field is then considered, and a solution is obtained in terms of Bessel functions for the density and pressure field. The results show that for submerged surfaces there is a transfer of water from the eastern to the western boundary along the southern boundary of the gyre, with a clockwise recirculating gyre elsewhere. For outcropped isopycnal surfaces, downwelling into the western boundary is the primary transport mode, with recirculation and east to west transport playing secondary roles. Finally, the relation of this model to layered models is discussed.
A climatological field of mean optical properties of the world ocean
Authors: Simonot Jean‐Yves , Le Treut Hervé
Published: February 2008

A 5° × 5° climatological field of the extinction coefficient of solar irradiance versus depth is obtained for the world ocean. A simple method of merging various data (prior to 1974) concerning the water transparency has been used. The final product is obtained through a careful subjective analysis. It should be useful for the purpose of climatological modeling.
A study of the relationship among wind speed, sea state, and the drag coefficient for a developing wave field
Authors: Huang Norden E. , Bliven Larry F. , Long Steven R. , DeLeonibus Pat S.
Published: February 2008

Laboratory experiments have indicated that waves have a noticeable influence on the value of the drag coefficient. On the basis of data from our laboratory and others, as well as field studies, we conclude that for a developing wave field under neutral stability conditions the roughness length formula proposed by Kitaigorodskii (1970) offers a reasonable parameterization of the roughness length and the drag coefficient under a variety of wind and wave conditions. Additionally, it is shown that the Kitaigorodskii formula is a generalization for both the Charnock (1955) and Hsu (1974) formulae. The results of this study also offer an explanation for the scatter in the previous studies of drag coefficient as a function of wind speed alone.
Energy and action flow through the internal wave field: An eikonal approach
Authors: Henyey Frank S. , Wright Jon , Flatté Stanley M.
Published: February 2008

The energy and action flow through the small‐scale part of the oceanic internal wave field is modeled by use of the eikonal technique, which is not subject to a weak interaction assumption. Both Monte Carlo calculations and a simplified model are presented and found to agree. It is found that the action flows toward slightly higher frequency (and thus the waves gain energy), in striking contrast to weak interaction predictions of a strong frequency decrease. The energy dissipation scales with depth as N2 cosh−1 (N/f), in agreement with measurements. The overall level is, however, a factor of 4 smaller than measurements. Possible sources of this discrepancy are discussed. A comparison is made with previous theoretical approaches for the depth dependence of dissipation.
A two‐scale model of short wind‐generated waves and scatterometry
Authors: Plant William J.
Published: February 2008

The principle of conservation of action is applied to derive a spectral form for short, wind‐generated waves on the ocean which is valid to second order in the slopes of longer surface waves. Using this form, composite surface theory is applied to microwave backscatter from the ocean surface in the Bragg regime to derive an expression for the normalized radar cross section of the sea, σ0, which is also valid to second order in long‐wave slope. This expression is compared with previous data and empirical models of σ0 and is shown to account for the observed incidence angle, azimuth angle, wind speed, and polarization dependence. Comparisons are made at Ku and C band for incidence angles between 20° and 70°. The theory indicates the manner in which atmospheric stability, long‐wave spectra, and sea surface temperature may influence σ0. Upwind‐downwind asymmetry of σ0 is shown to occur because of the second‐order interaction of short‐wave modulation with the orbital velocities of long waves. Furthermore, the results suggest that the wind speed dependence of σ0 varies only slightly with microwave frequency, while the magnitude of σ0 increases somewhat with frequency until viscous or turbulent dissipation reduces short‐wave growth rates and thus amplitudes. Implications for scatterometer algorithm development are discussed.
On the origin of the chemical properties of the Arctic Ocean halocline
Authors: Jones E. P. , Anderson L. G.
Published: February 2008

Profiles of chemical constituents in seawater above the Alpha Ridge in the central Arctic Ocean obtained during the Canadian Expedition to Study the Alpha Ridge (CESAR) support a model in which the halocline is maintained by dense, saline water produced on the continental shelves within the Arctic Ocean by the formation of sea ice. It is argued that nutrient regeneration on the continental shelves largely accounts for the nutrient maximum that has been observed in the upper halocline over a wide region of the Arctic Ocean, and that while the Bering Sea and North Altantic can be recognized as origins of halocline water, water masses from these regions undergo sufficient changes in their chemical properties within the Arctic Ocean significant that they no longer retain their identity in the halocline.
CO2 fluxes in the tropical Atlantic during FOCAL cruises
Authors: Andrié Chantal , Oudot Claude , Genthon Christophe , Merlivat Liliane
Published: February 2008

CO2 partial pressures in the atmosphere and in surface seawater have been measured in the equatorial Atlantic Ocean during Programme Français Océan‐Climat en Atlantique Equatorial cruises extending from July 1982 to August 1984 along the 4°W, 22°W, and 35°W meridians. Gas transfer coefficients based on recently reported field data combined with information deduced from wind tunnel experiments are used to compute the CO2 fluxes. The global mean net flux between 5°N and 5°S is equal to 1.05 mmol m−2 d−1 and is from the ocean to the atmosphere. The escape of CO2 increases strongly from the east to the west and is always lower in the north than in the south. The importance of wind speed, pCO2 in atmosphere, PCO2 in surface seawater, and temperature on the flux variability is discussed. The relative influence of the equatorial upwelling on one hand and of the advection and warming of surface waters on the other hand is studied in order to explain high partial pressure in seawater.
A simplified second‐order solution for a spiral wave maker
Authors: Trowbridge John , Dalrymple Robert A. , Suh Kyungduck
Published: February 2008

A second‐order solution for the spiral wave field produced by a rotating circular cylinder in a basin of constant depth is presented. The analysis is limited to cases in which the wave amplitude is small compared with the wave maker radius, which is in turn small compared to the wavelength. Under these circumstances, we show by an order‐of magnitude argument that one may consistently simplify the second‐order analysis by neglecting the quadratic terms in the free surface boundary conditions while retaining the leading terms in the wave maker boundary condition. The resulting solution indicates the presence of free secondary waves which do not propagate at the same speed or in the same direction as the first‐order waves. Laboratory measurements are presented which demonstrate the ability of the solution to reproduce measurements of the surface displacement with reasonable accuracy. At large distances from the wave maker, the free waves completely dominate the second‐order waves forced by the nonlinear terms in the free surface boundary conditions. Consequently, a cylindrical spiral wave maker does not simulate correctly the second‐order component of regular plane waves.
Mesoscale hydrographic variability in the vicinity of Points Conception and Arguello during April–May 1983: The OPUS 1983 experiment
Authors: Atkinson Larry P. , Brink Kenneth H. , Davis Russ E. , Jones Burton H. , Paluszkiewicz Theresa , Stuart David W.
Published: February 2008

In April and May 1983, interdisciplinary oceanographic observations were made of upwelling events in the Point Conception area off southern California. The principal objective was to observe the structure and time dependence of the upwelling system. To accomplish this, two ships, two aircraft, moorings, drogues, and satellite imagery were all included in the observational effort. During the intensive measurement period three main upwelling events and two intervening relaxation or downwelling intervals were sampled during what was a period of overall longer‐term sea surface warming. Surface temperatures during upwelling were as low as 10.5°C in the upwelling center between Point Arguello and Point Conception, while during periods of nonupwelling winds, temperatures reached 14°–15°C in the same area. The upwelling center was also a source of higher‐salinity water (33.7‰) relative to the offshore waters that were anomalously fresh (33.3‰). Upwelling was observed off Point Arguello, Point Conception, and the area between with a possible lag of up to a day at Point Conception relative to the other areas. The upwelling plume as observed by surface mapping and remote sensing tended to move in a variety of directions from SE to SW. Part of the movement was usually into the Santa Barbara Channel, but other parts of the plume occasionally moved southwestward. There was no obvious correlation of plume direction with the wind. During relaxation events the entire region was covered by a 10‐ to 20‐m‐thick warm (14°–16°C), fresh (<33.5‰) buoyant layer. Spatial correlations of water temperature with 24‐hour lagged winds showed logical patterns, but the distributions were not as seen in other California studies.
Laboratory experiments on the steady gravitational circulation excited by cooling of the water surface
Authors: Harashima A. , Watanabe M.
Published: February 2008

A gravitational circulation excited by cooling of the water surface was investigated based on laboratory experiments. Our main object is to construct a framework to predict bulk characteristics of the phenomena from a rational assemblage of the external parameters. Water surface of the shallower section of the experimental channel (bay section) was cooled by circulating a cooled, dehumidified air above, while the deeper section (outer ocean section) was thermally kept constant. This setup represented the situation of the “inverse estuary.” Excited flow was directed to the dead end of the shallower section in the upper layer with a remarkable turbulent convection and returned back to the deeper section in the lower layer with relatively laminar characteristics. Sixteen sets of experiments were performed by changing the buoyancy flux bf and the water depth H. The measured flow rate q distribution and the buoyancy b were basically expressed by the power of the longitudinal coordinate x and bf. However, the dependence showed a systematic departure from the power law parts of the similarity solution given by Phillips [1966]. Defining “buoyancy flux velocity” U* (≡ bf1/3L1/3), we derived a nondimensional equation system that is characterized by “flux Reynolds number” Ref (≡ bf1/3H2L−2/3υv−1). Ref is composed solely of the external parameters and is interpreted as being the ratio of the motive force to the viscous force unlike the usual Reynolds numbers. The nondimensional flow rate q′ (≡ q1U*−1H−1) was found to increase monotonically with respect to Ref. A dimensional reasoning with the scale analysis showed the relation q′ = C1Ref1/2 and q′ = C2 − C3Ref−1/2 in the ranges of substantially small and large Ref, respectively. The experimental data coincided with these two curves, and the coefficients C1, C2, and C3 were determined to be 0.044, 0.43, and 1.67, respectively.
Properties of long equatorial waves in models of the seasonal cycle in the tropical Atlantic and Pacific Oceans
Authors: Philander S. G. H. , Hurlin W. J. , Pacanowski R. C.
Published: February 2008

In general circulation models of the seasonal cycle, westward propagating waves, with an approximate wavelength of 1000 km and period of 3 to 4 weeks, in the western equatorial Atlantic and eastern equatorial Pacific derive their energy from the kinetic and potential energy of the mean flow. There is intense downwelling in the cold crests of the wave and upwelling in the warm troughs. The local meridional heat flux associated with the waves is of the order of 100 W m−2, but their contribution to the net heat transport across the equator is small. The waves are highly nonstationary in time and inhomogeneous in space.
Pressure variations on the Atlantic equator
Authors: Cartwright D. E. , Spencer R. , Vassie J. M.
Published: February 2008

Records of more than a year's duration from three deep ocean pressure sensors and three island shallow pressure sensors, all close to the equator between 30°W and 7°E, are analyzed spectrally at frequencies below the diurnal tides. The records were taken as integral parts of the FOCAL‐SEQUAL experiments in the equatorial Atlantic, 1983–1984. The low‐frequency gravitational tides at 1, 2, 3 cycles per month formed an important, nearly simultaneous part of the signal and had to be removed. The seasonal variations associated with equatorial upwelling are prominent in the shallow but not the deep pressure signals. Practically all the non tidal deep pressure signals at 0.1–0.7 cycles per day (cpd) are highly coherent between 20°W and 6°E, some 2900 km, and show no sign of zonal propagation. A comparison of the coherent part of the signals between the equator and Ascension Island (8°S) suggests a southward component of propagation, at least in the region of the Mid‐Atlantic Ridge. These motions are evidently barotropic and are not trapped near the equator. A close relationship to the atmospherically forced barotropic waves at 4–6 days period in the Pacific, identified by Luther (1980), is suggested. Special consideration is given to a comparison of a 3.6‐km‐deep pressure record at 6°E with a shallow pressure record from Ilha São Tomé' (supplied by J. M. Verstraete). Their ordinary tidal components are practically identical, as befits purely barotropic motion, but the sub‐tidal continuum shows fairly low (though significant) coherence, with higher energy in the island record. This is attributed to the presence of internal wave modes of several meters internal amplitude. Theoretically, the contribution of internal waves should give a much stronger signal in the surface pressure than in the deep pressure signal. The relationships are demonstrated by calculations based on acoustic return times by two inverted echo sounder recorders placed close to deep pressure sites by E. J. Katz. Deduced coherences agree reasonably with observed values and are consistent with internal waves dominated by mode 1, uncorrelated with the barotropic motion, sensed in both deep and shallow pressure gauges.
Island wakes and headland eddies: A comparison between remotely sensed data and laboratory experiments
Authors: Pattiaratchi Charitha , James Alec , Collins Michael
Published: February 2008

Island wakes and headland eddies in coastal waters are identified from spaceborne and airborne remotely sensed imagery in the visible wavelengths. The imagery were obtained for the Bristol and English channels, United Kingdom, which are characterized by high tidal currents and levels of turbidity. Suspended matter in the surface waters is used as a passive tracer for the flow features. Scaling parameters (e.g., the Reynolds, Ekman, and Rossby numbers), obtained from the depth averaged equation of motion, are presented based upon information on oceanographic conditions at the times of the overpasses. The parameters are compared then with data obtained from laboratory model investigations, presented by other experimenters in the published literature. The remotely sensed data demonstrate that in coastal waters with nonuniform obstacles and bathymetry, for a given Ekman number the flow regimes occur at a lower Rossby number than might be expected from laboratory experiments. In the absence of a method for the accurate determination of the horizontal eddy viscosity, hence the Reynolds number, it is concluded that an “island wake parameter” (Wolanski et al., 1984a) should be adopted to describe such features in coastal waters.
Mesoscale surveys over the shelf and slope in the upwelling region near Point Arena, California
Authors: Huyer Adriana , Kosro P. Michael
Published: February 2008

Repeated mesoscale surveys of a 40‐km‐wide, 100‐km‐long, coastal region near Point Arena, California, were conducted during the upwelling season (April–August) in 1981 and 1982. Each survey included conventional conductivity‐temperature‐depth casts at standard locations over the continental shelf and slope between 38°N and 39°10′N, and continuous operation of a Doppler acoustic log to obtain velocity profiles in the 20‐ to 150‐m depth range. “Synoptic” surveys covered the entire grid in 2–3 days. Winds were strongly favorable for upwelling during the three 1981 surveys and were weak or variable during the three 1982 surveys. Surface temperature and salinity fields reflect the influence of both the seasonal winds and day‐to‐day variations in the wind. Persistently low surface salinities offshore reflect the general southward advection of subarctic waters, and sporadic low salinities over the inner shelf reflect north‐ward advection of local runoff through an intermittent narrow countercurrent along the coast. Circulation patterns during all but one of the surveys were very complex and included meandering equatorward flow, cyclonic and anticyclonic eddies, and inshore countercurrents. The simple two‐dimensional, equatorward, baroclinic coastal jet usually associated with coastal upwelling was observed during only one of our surveys. Overall average fields are relatively simple. They show broad equatorward surface flow, a very weak inshore countercurrent, and a definite poleward undercurrent at the shelf break. Average temperature, salinity, and density fields are generally congruent with the average flow pattern. Average isotherms and isohalines are not strictly parallel to the coastline: south of the coastline bend at Point Arena, they diverge gradually from the coast. Comparison of average sections calculated from 10 matched pairs of Central and Arena lines (separated by 50 km) shows there are systematic differences between them. Warmer, fresher waters lie nearer shore (and in shallower water) off Point Arena than on the Central line; this suggests that the surface waters flowing past Point Arena have sufficient southward momentum to cross isobaths. Comparison of average velocity sections on these two lines shows some differences in structure; since the variability is large, these may not be significant. Comparison of the measured and geostrophic average shears suggests there is a significant ageostrophic component in the upper layers above 40 m; it may be the signature of an average wind‐driven Ekman spiral.
The large‐scale coastal wind field along the west coast of North America, 1981–1982
Authors: Halliwell George R. , Allen J. S.
Published: February 2008

We study the statistical properties of the coastal wind field along the west coast of North America for two summers, 1981 and 1982 (Coastal Ocean Dynamics Experiments 1 and 2, respectively), and the intervening winter using measured winds and geostrophic winds calculated from Fleet Numerical Oceanography Center atmospheric pressure analyses. Summer wind fluctuations are driven primarily by the interaction between two relatively stationary pressure systems, the North Pacific subtropical high and southwest U.S. thermal low, and by their interactions with propagating atmospheric systems to the north. In particular, propagating cyclones and associated fronts are often followed by a northeastward intensification of the high, producing strong upwelling events along the California coast. This summer event sequence occurs more frequently and is displaced farther to the south on average during summer 1981. Winter wind fluctuations are primarily driven by propagating cyclones and anticyclones, and they tend to have larger variance and space scales than in summer. A preference for poleward (equatorward) propagation exists in summer (winter), and the largest time scales are observed in summer 1982. Coastal atmospheric boundary layer processes substantially modify winds within 100–200 km of the coast. Consequently, measured wind fluctuations are strongly polarized in the alongshore direction and have means and rms amplitudes that can vary considerably between nearby stations along the coast. Calculated wind fluctuations are less polarized in the alongshore direction and have alongshore correlation scales about 60% larger than those for measured winds. They represent fluctuations with alongshore wavelengths of ≧ 900 km rather well but represent poorly those with smaller wavelengths and those due to coastal atmospheric boundary layer effects.
The contribution of rainwater to variability in surface ocean hydrogen peroxide
Authors: Cooper William J. , Saltzman Eric S. , Zika Rod G.
Published: February 2008

Hydrogen peroxide concentrations have been determined in marine rain from the Gulf of Mexico

, the western Atlantic Ocean

, and one rain event off the Florida Keys
. In several cases, simultaneous measurements of the concentration of H2O2 in the surface ocean were also determined. These measurements were made with the ship under way using a continuous flow sampling system with the intake at the bow. In shallow stratified layers, rain events can increase the existing hydrogen peroxide concentration by a factor greater than 10 and dramatically increase the mean H2O2 concentration of mixed depth layers of 50 m or more. Rain is a significant transient source of H2O2 in the surface ocean.
Further studies on the response of the equatorial thermocline in the Atlantic Ocean to the seasonally varying trade winds
Authors: Weisberg R. H. , Tang T. Y.
Published: February 2008

Upper ocean temperature data obtained during the Seasonal Response of the Equatorial Atlantic experiment and the Francais Ocean et Climat dans l'Atlantique Equatorial program are used to describe the variations of the thermocline observed along the equator from February 1983 to September 1984. In response to rapid seasonal changes in zonal wind stress, the thermocline underwent sequences of upwelling followed by downwelling or conversely, depending upon whether the winds were intensifying or relaxing. These sequences increased systematically in magnitude and duration to the east. Both the sequential behavior and its zonal inhomogeneity represent departures from the slowly varying and in‐phase climatological description of the annual thermocline response. An analytical, reduced‐gravity, equatorial long wave model forced by zonal wind stress distributions representative of the variations observed along the equator was employed to reconcile the differences between the 1983–1984 synoptic measurements and the climatologically averaged description. Qualitative agreements between the model results and the data were found for many salient features of the annual cycle, including the zonal pressure gradient calculated by finite difference. The features in the model arise as interference patterns between directly forced and reflected Kelvin and long Rossby waves that are generated with each change in the wind stress. The manner in which the wind stress changes from year to year is therefore crucial to the equatorial ocean's response.
The West Spitsbergen Current: Disposition and water mass transformation
Authors: Aagaard K. , Foldvik A. , Hillman S. R.
Published: February 2008

Recent work suggests that the West Spitsbergen Current, which provides the principal contribution to the Arctic Ocean of salt and sensible heat, as well as of a variety of anthropogenic tracers, is a rather complex circulation feature. North of 79°N, where the isobaths diverge markedly, the current contains two separate warm cores that follow different isobaths. The western core, carried by the offshore branch of the current, follows the western flank of the Yermak Plateau, and north of 80°N at least part of this flow detaches from the plateau, probably to contribute to the recirculation in Fram Strait. In contrast, the inshore branch follows the shelf break into the Arctic Ocean. It is this inshore branch that provides the primary focus in this paper. During the transit of the inshore waters past northwestern Spitsbergen, the core properties change primarily through vertical heat flux, which during ice‐free conditions in winter is estimated to be of the order of 200 W m−2 from the core layer alone. Together with some freshening within the Arctic Ocean, this process is responsible for fully transforming the original Atlantic water into arctic intermediate water within about 600 km of Fram Strait.