Classic Article: Steady flow in a frictionless homogenous ocean

A mathematical model is developed to study the free (frictionless) steady horizontal flow which can occur in a homogeneous ocean of constant depth. The flow satisfies the dynamic constraint that the vertical component of absolute vorticity is constant along a streamline. The conclusion is reached that in an enclosed ocean a free steady circulation cannot have any slow broad eastward currents. The eastward currents must occur as narrow streams of high velocity and high relative vorticity. Intensified currents are present along the eastern and western coasts. The theory which is developed for the homogeneous ocean of constant depth can be applied to the two-layer ocean if the horizontal divergence of flow is negligible. If the horizontal divergence is not negligible, then the intensification of poleward currents is more pronounced and that of equatorward currents less pronounced as compared with the homogeneous ocean

Nonlinear limits to ocean thermal structure

The nonlinear volume changes associated with diffusion and mixing of different seawater types produce significant conversions of gravitational potential energy to kinetic energy to maintain and enhance mixing processes and to limit the magnitudes of temperature gradients that can persist in the ocean. Several examples are given to illustrate these critical temperature gradients beyond which conversion exceeds local energy consumption by mixing. The vertical temperature gradients in the Gulf Stream reduce downstream from Cape Hatteras to the critical limit found in the North Atlantic thermocline. The limiting gradients are also seen in surface thermoclines and in staircase structures. Although the theoretical interpretation of the nonlinear limiting processes is still incomplete, the observational evidence is compelling for further study of these mechanisms

Steady flow in a frictionless homogeneous ocean

A mathematical model is developed to study the free (frictionless) steady horizontal flow which can occur in a homogeneous ocean of constant depth. The flow satisfies the dynamic constraint that the vertical component of absolute vorticity is constant along a streamline...

Specific gravity and density of seawater at atmospheric pressure

Four independent sets of specific gravity measurements are intercompared relative to a least squares polynomial in temperature and salinity over the range - 2 to 30°C and 8 to 40‰. Within this range, individual measurements have a standard deviation of 7.1 ppm about the regression polynomial. Over most of the range, the polynomial formula has a standard deviation of 1 to 3 ppm. The data sets are marginal in defining specific gravity below 0°C and above 25°C and inadequate below 10‰ salinity

Ensemble inequivalence, bicritical points and azeotropy for generalized Fofonoff flows

We present a theoretical description for the equilibrium states of a large class of models of two-dimensional and geophysical flows, in arbitrary domains. We account for the existence of ensemble inequivalence and negative specific heat in those models, for the first time using explicit computations. We give exact theoretical computation of a criteria to determine phase transition location and type. Strikingly, this criteria does not depend on the model, but only on the domain geometry. We report the first example of bicritical points and second order azeotropy in the context of systems with long range interactions.Comment: 4 pages, submitted to Phys. Rev. Let

Oceanic flow over varying bottom topography

A study has been made of steady barotropic flows on the β plane over a bottom topography that varies in a direction inclined to the circles of latitude. The solutions obtained, starting with both the Eulerian and the Lagrangian systems of equations, are shown to be identical in the case of flow over a single-depth discontinuity...

Algorithms for computation of fundamental properties of seawater

Endorsed by Unesco/SCOR/ICES/lAPSO Joint Panel on Oceanographic Tables and Standards and SCOR Working Group 51Algorithms for computation of fundamental properties of seawater, based on the practical salinity scale (PSS-78) and the international equation of state for seawater (EOS-80), are compiled in the present report for implementing and standardizing computer programs for oceanographic data processing. Sample FORTRAN subprograms and tables are given to illustrate usage of the algorithms and to show the range of variation and limits of validity of commonly used seawater properties within the oceanic ranges for salinity, temperature and pressure. The algorithms cover the following: conductivity to salinity conversion; salinity to conductivity conversion; specific volume anomaly and density anomaly of seawater; pressure to depth conversion; freezing point temperature of seawater; specific heat of seawater; adiabatic lapse rate; potential temperature; sound speed in seawater.Compilation of the algorithms and tables was supported by the Office of Naval Research under contracts N00014-74-C-0262, NR083-004 and N0001476- C-0197, NR083-400 and by the National Science Foundation under Grant OCE 78-06886.00

Available potential energy for mode eddies

Also published as: Journal of Physical Oceanography 11 (1981): 30-47Available potential energy (APE) is defined as the difference between total potential plus internal energy of a fluid in a gravity field and a corresponding reference field in which the fluid is redistributed (leveled) adiabatically to have constant stably-stratified densities along geopotential surfaces. Potential energy changes result from local shifts of flu id mass relative to geopotential surfaces that are accompanied by local changes of enthalpy and internal energy and global shifts of mass (because volumes of fluid elements are not conserved) that do not change enthalpy or internal energy. The potential energy changes are examined separately by computing available gravitational potential energy (GPE) per unit mass and total GPE (TGPE) per unit area. A technique for estimating GPE in the ocean is developed by introducirtg a reference density field (or an equivalent specific volume anomaly field) that is a function of pressure only and is connected to the observed field by adiabatic vertical displacements. The full empirical equation of state for seawater is used in the computational algorithm. The accuracy of the estimate is limited by the data and sampling and not by the algorithm itself, which can be made as precise as desired. The reference density field defined locally for an ocean region allows redefinition of dynamic height ΔD (potential energy per unit mass) relative to the reference field. TGPE per unit area becomes simply the horizontal average of dynamic height integrated over depth in the region considered. The reference density surfaces provide a precise approximation to material surfaces for tracing conservative variables such as salinity and potential temperature and for estimating vortex stretching between surfaces. The procedure is applied to the MODE density data collected in 1973. For each group of stations within five 2-week time windows (designated Groups A-E) the estimated GPE is compared with the net APE based on the Boussinesq approximation and to the low-frequency kinetic energy measured from moored buoys. Changes of potential energy of the reference field from one time window to the next are large compared with the GPE within each window, indicating the presence of scales larger than the station grid. An analysis of errors has been made to show the sensitivity of the estimates to data accuracy and sampling frequency.Prepared for the Office of Naval Research under Contract N00014-76-C-0197

W.H.O.I./Brown CTD microprofiler : methods of calibration and data handling

This report describes calibration techniques developed over the past three years for the WHOI/Brown CTD in the Moored Array Program. Comparison is made with classical methods of hydrography for stations obtained in the MODE-1 density program. Methods for temperature lag correction and conversion of conductivity to salinity are given.Prepared for the Office of Naval Research under Contract N00014-74-C0262; NR 083-004

Current measurements from moored buoys

Also published as: Buoy Technology, Transactions 2nd International Buoy Technology Symposium/Exposition, Washington, D.C., September 18-20, 1967, pp.409-418, 1967.Since January 1965,a program has been underway at the Woods Hole Oceanographic Institution, to measure currents at a limited number of fixed sites on a year round basis. Initially, one site was instrumented with both surface and subsurface moorings. The program has now been expanded to 4 major sites, extending along 70°W, from 39°20 ' N to the Hatteras Abyssal Plain at 30°N . In nearly three years of operation, a total of 65 moorings have been placed at the working sites, for periods up to six months. Recoveries from these sites have provided many velocity records of excellent quality. The repetitive exposure of moorings of essentially similar design under relatively standardized conditions has served to define clearly the design and operational problems that are inherent in such a program. A brief account is given of some of the problems encountered in routine buoy setting operations, and some of the results obtained from the measurements.The Office of Naval Research under Contract N00014-66-C0241~ NR 083-004