Physical oceanography

Physical oceanography

Oceanographic Literature Review (1989) 36 (12) The citations are those received in the editorial office during the period 1-31 August, 1989. Most are ...

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Oceanographic Literature Review (1989) 36 (12) The citations are those received in the editorial office during the period 1-31 August, 1989. Most are accompanied by a short annotation or abstract and, when obtainable, by the first author's address. The citations are classified under six main headings and about 130 sub-headings (see the table of contents). Subject and author indexes are published for the first three quarters of the year with an annual cumulation. See the preface for additional explanatory material.

A. PHYSICAL OCEANOGRAPHY

A10. Apparatus and methods 89:6791 Barrick, D.E., B.J. Lipa and K.E. Steele, 1989. Comment on 'Theory and application of calibrotion techniques for an NDBC directional wave measurements buoy' [by Steele et al., 1985]: nonlinear effects. I E E E Jl ocean. Engng, 14(3): 268-272.

The existence and properties of sharp horizontal mesoscale inhomogeneities in the principal thermocline of the Canary Upwelling and at four other sites during January-April 1987 are discussed. Shirshov Inst. of Oceanol., Acad. of Sci., Moscow, USSR. (emm)

A80. Circulation A50. General hydrography (distribution of c o m m o n oceanic properties) 89:6792 Monin, A.S., R.V. Ozmidov and V.T. Paka, 1988. Horizontal mes0structure of the principal thermeeline. Dokl. Earth Sci. Sect. (a translation of Dokl. Akad. Nauk SSSR), 297(1-6):246-249.

89:6793 Busalacchi, A.J. and Fr~i~rique Blanc, 1989. On the role of closed and open boundaries in a model of the tropical Atlantic Ocean. J. phys. Oceanogr., 19(6): 831-840. In response to forcing by idealized winds and a realistic seasonal cycle, the large-scale interior solutions are relatively insensitive to the choice of

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A. PhysicalOceanography

boundary condition, which does, however, have an important impact on the western boundary circulation and its relation to the interior flow field. Transient effects during spinup produced significant differences in western boundary coastal upwelling and downwelling re~mes; the mere existence of certain western boundary features such as coastally trapped jets was strongly dependent on the choice of boundaries under mean and seasonal equilibrium conditions. Only those solutions with an open western boundary were able to simulate the continuous northwestward coastal flow of the North Brazil Current during spring and the complete eastward veering of this current into the NECC during the fall. NASA, Goddard Space Flight Ctr., Greenbelt, M D 20771, USA. ID:6794 Cessi, Paola, 1989. On the role of topography in the ocean circulation: diffusive and inertial effects. J. phys. Oceanogr, 19(6):841-852. If the topography has a structure in the east-west direction, then the solution found in the inviscid limit by Cessi and Pedlosky predicts the occurrence of strong jets in the interior of the model ocean. A numerical model is used here to test whether the jets survive when inertia and diffusion are included explicitly. These internal jets can occur in both vertically homogeneous and stratified models. If the topographic slope changes sign, one kind of jet occurs in both baroclinic and barotropic models. This phenomenon is observed with moderate amounts of diffusion and is not disturbed by the occurrence of recirculating inertial gyres within the basin. If the topographic slope is constant, then another kind of internal jet is theoretically predicted in stratified models only; numerical calculations did not exhibit this kind of jet in the presence of inertia and weak diffusion. Scripps Inst. of Oceanogr., A-021, La Jolla, CA 92093, USA. 89:6795 Hallock, Z.R., J.L. Mitchell and J.D. Thompson, 1989. Sea surface topographic variability near the New England Seamounts: an intercomparison among in-situ observations, numerical simulations, and Geosat altimetry from the regional energetics experiment. J. geophys. Res., 94(C6): 8021-8028. Intercomparisons are made among three sets of results for two regions of the Gulf Stream, upstream and downstream of the New England Seamount Chain (NESC). Standard deviations of sea surface topography show generally good agreement for the three data sources. No significant difference between upstream and downstream regions is observed in the

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actual data. I E S / P G records and Geosat topographic variability have values of about 30 cm on both sides of the NESC, although model results show a discrepancy in the eastern region. Barotropic fluctuations account for ~ 3 0 % of the total surface topographic variability and are only partially correlated with baroclinic fluctuations. NORDA, Code 331, Stennis Space Center, MS 39539, USA. 89:6796 Smith, N.R., 1989. The Southern Ocean thermohaline circulation: a nmerical model sensitivity study. J. phys. Oceanogr~ 19(6):713-726. A two-dimensional primitive equation model is driven by surface flux of momentum, heat and salt, and is implemented with and without the dynamic component in order to delineate important thermodynamic interactions. The fundamental climatic balance is characterized by downward and poleward diffusion of heat, predominantly by diffusive processes, and subsequent convection at high latitudes. The balance is sensitive to seasonal effects, particularly salt-forced convection in winter, and the details of the parameterizations. The convection and diffusion representations are critical for Antarctic water mass formation and frontogenesis. Bur. of Meteorol. Res. Ctr., GPO Box 1289K, Melbourne, Vic. 3001, Australia. 89:6797 Suginohara, Nobuo and Masao Fukasawa, 1988. Set-up of deep circulation in multi-level numerical models. J. oceanogr. Soc. Japan, 44(6):315-336. Cooling of the whole ocean starts with introduction of cold water from the Southern Ocean formation region into the deepest part of the ocean in the equatorial and eastern boundary regions by Kelvin wave-type density currents. Cold water along the eastern boundary extends westward as a Rossby wave-type density current setting up an interior poleward flow, and hits the western boundary to form a northward flowing boundary current in the Northern Hemisphere. Only then does the western boundary current cross the Equator. Cooling of the rest of the ocean basin is accomplished by upwellings in the interior and along the coasts. Circulation at a steady state has a significant vertical structure such that maximum upwelling in the interior occurs in the mid-depths, and only the deeper part of the deep ocean yields the Stommel and Axons circulation, pattern. In the equatorial region higher vertical mode motions dominate, and a set of alternating zonal jets forms along the Equator. Geophys. Inst., Univ. of Tokyo, Yayoi, Bunkyo-ku, Tokyo 113, Japan.

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A. Physical Oceanography

A90. Currents 89:6798 Brooks, D.A. and D.W. Townsend, 1989. Variability of the coastal current and nutrient pathways in the eastern Gulf of Maine. J. mar. Res., 47(2):303321. Dept. of Oceanogr., Texas A&M Univ., College Station, TX 77843, USA. 89:6799 Crisciani, F., 1988. Barotropic instability of a coastal current: semicircle theorems revisited. Boll. Oceanol. teor. appl., 6(2):59-68.

In the context of the barotropic instability theory of a coastal current, two semicircle theorems are reexamined and a new eigenvalue confinement procedure is formulated. This procedure simplifies the proof of the theorems and is extendable to other problems concerning the instability of geophysical flows. C.N.R., Ist. Sperimentale Talassografico, Trieste, Italy. 89:6800 Fu, L.-L. and Victor Zlotnicki, 1989. Observing oceanic mesoscale eddies from Geosat altimetry: prefimlnary results. Geophys. Res. Lefts, 16(5): 457-460.

Sea level variations measured by the Geosat radar altimeter are used to study the spatial and temporal scales of eddy motion and to map the temporal evolution of the eddy field in the region of the Agulhas Current south of Africa, where eddy motions are among the strongest in the world. Results demonstrate that Geosat has provided an unprecedented opportunity to map from space the temporal evolution of sea level variability associated with energetic eddies in the ocean. Jet Propulsion Lab., California Inst. of Tech., M / S 300-323, 4800 Oak Grove Dr., Pasadena, CA 91109, USA. 89:6801 Ichiye, Takashi and Kenzo Takano, 1988. Mesoscale eddies in the Japan Sea. Mer, Tokyo, 26(2):69-75.

Isotherms at 100 m depth in the Japan Sea in May and June, 1987 show isolated warm and cold eddies of 30-160 km diameter and two to three fronts with meanders of wavelength 100-400 kin. Climatological data from 1900 to the 1970s indicate that surface currents determined with G E K have best correlation with temperature gradients at 100 m compared with those at the surface and at 200 m. Field experiment and numerical modeling plans are proposed for obtaifiing data sets of temperature fields with AXBTs and corresponding eddy resolving numerical models of the Japan Sea. Dept. of Oceanogr., Texas A&M Univ., College Station, TX 77843, USA.

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89:6802 Kawabe, Masaki, 1988. Variability of Km'oshio velocity assessed from the sea-level difference between Naze and Nishinoomote. J. oceanogr. Soc. Japan, 44(6):293-304.

Variations in current velocity of the Kuroshio are evaluated with respect to sea level differences between the offshore (Naze) and onshore (Nishinoomote) sides of the Kuroshio in the Tokara Strait. Interannual variations are shown to be highly coherent with offshore sea level at periods longer than 1.7 yr and incoherent with the onshore level at periods longer than 2.8 yr. Mean seasonal variations are classified by amplitude, dominant period and phase and related to cycles of the large Kuroshio meander and to El Niflo. Ocean Res. Inst., Univ. of Tokyo, Minamidai 1-15-1, Nakano-ku, Tokyo 164, Japan. (emm) 89:6803 Mertz, Gordon, M.I. EI-Sabh and V.G. Koutitonsky, 1989. Low frequency variability in the lower St. Lawrence Estuary. J. mar. Res, 47(2):285-302. Dept. d'Oceanogr., Univ. du Quebec, 300 Allee des Ursulines, Rimouski, PQ G5L 3AI, Canada. 89:6804 Mosetti, Ferruccio, 1988. Some news on the currents in the Straits of Messina. Boll. Oceanol. teor. appl., 6(3):119-203. C a t t e d r a di Misure Oceanogr., Univ. di Trieste, Italy. 89:6805 Noble, Marlene and Bradford Butman, 1989. The structure of subtidul currents within and around Lydonia Canyon: evidence for enhanced erossshelf fluctuations over the mouth of the canyon. Y. geophys. Res., 94(C6):8091-8110.

Amplitude of the subtidal currents over the shelf and slope ranged 10-30 cm s-l, but within the canyon, they were typically smaller than 5 cm s-t. Currents within the canyon and just above it were driven up and down the canyon by the cross-shelf pressure gradient in geostrophic equilibrium with the alongshelf flow. Measurements suggest that the Coriolis force on the cross-canyon flow, turbulent Reynolds stresses, and acceleration of the along-canyon flow balanced the imposed pressure gradient for flow near the rim. The horizontal turbulent viscosity coefficient for subtidal flow in this narrow canyon is 106 to 107 cm 2 s-I. The mixing indicated by the large amplitude of the viscosity coefficient was probably caused by the strong tidal currents present within Lydonia Canyon. Wind stress was not correlated with currents over the slope in water deeper than 450

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m or with currents within the canyon. USGS, 345 Middlefield Rd., Menlo Park, CA 94025, USA.

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mates. Inst. fur Meereskunde, Dusternbrooker Weg 20, D 2300 Kiel, FRG.

89:6806

Rikiishi, Kunio and Katsunori Sasaki, 1988. C,¢ostrophic balance of the Kuroshio as inferred from surface current and sea level observations. J.

oceanogr. Soc. Japan, 44(6):305-314. Historical observations of the surface current and daily mean sea level during the period 1965-1985 are analyzed in order to examine the geostrophic balance of the Kuroshio Current in the Tokara Strait and near the Izu Islands. The variation in sea level difference across the Kuroshio is associated with a variation in surface current velocity as predicted by the theory of geostrophic balance. However, the slope of the linear relation between the current velocity and sea level difference is smaller than the theoretically predicted value by about 30%. This disagreement may be ascribed to the effects of centrifugal force and the occasional rise in sea level due to storm surges. Dept. of Earth Sci., Hirosaki Univ., Hirosaki 036, Japan.

89:6809

Svendsen, IB.A. and R.S. Lorenz, 1989. Velocities in combined undertow and

Iong-~re

currents.

Coast. Engng, Amst., 13(1):55-79. The flow composed of a periodic wave motion with turbulent fluctuations caused by breaking and a (slowly varying) mean current, consisting of the combined cross-shore and longshore current velocities generated by the waves, is considered. For the special case of a cylindrical coast and turbulent shear stresses modelled by an eddy viscosity, the equations for the longshore velocity variation V(x,z) over depth and distance from the shore satisfy a Poisson equation. A perturbation solution is derived to a second order for V(x,z) and the classical solutions for V(x) from the literature are found to be logically related to the new solution. Dept. of Civil Engng, Univ. of Delaware, Newark, DE 19716, USA. 89:6810

89:6807 Shapiro, G.I., 1988. Long-lived solitary eddies in the

Thompson, J.D. and W.J. Schmitz Jr., 1989. A limited-area model of the Gaff Stream: design,

ocean. DokL Earth Sci. Sect. (a translation of Dokl. Akad. Nauk SSSR), 297(1-6):222-224.

initial experiments, and model--data intercomparison. J. phys. Oceanogr., 19(6):791-814.

The objective of this paper is to elucidate the cause of the anomalously long lifetimes of solitary eddies and to obtain theoretical estimates of their lifetimes as a function of their intensity and horizontal size. Taking into account new factors resulting from finite amplitude effects, and focusing on slowly evolving solutions, two classes of long-lived eddies of the non-soliton type are discussed. Shirshov Inst. of Oceanol., Acad. of Sci., Moscow, USSR.

A primitive-equation, n-layer, eddy-resolving circulation model has been applied to the Gulf Stream System from Cape Hatteras to east of the Grand Banks. Within the limitations of the model, realistic coastlines, bottom topography, and forcing functions have been used. A two-layer version of the model was driven by observed mean climatological wind forcing and mass transport prescribed at inflow. Outflow was determined by a radiation boundary condition and an integral constraint on the mass field in each layer. Specification of a Deep Western Boundary Current (DWBC) was included in some model runs. Six numerical experiments were selected for detailed description and intercomparison with observations. Results suggest an important role for the DWBC in determining the mean path of the Gulf Stream and consequently the distribution of eddy kinetic energy, and the character of the deep mean flow. The mean flow is characterized by recirculations to the north and south of the Gulf Stream and a deep cyclonic gyre just east of the northern portion of the New England Seamount Chain, as found in the data. NORDA, Code 323, NSTL Station, MS 39529-5004, USA.

89:6808

Stramma, Lothar, 1989. The Brazil Current transport south of 23°S. Deep-Sea Res., 36(4A):639-646. Geostrophic computations from historical data across the Brazil Current at 23 ° and 24°S lead to transports of 10.2 and 9.6 Sv, respectively. At 33°S the transport is estimated to be 17.5 Sv. A recirculation cell of 7.5 Sv is found in the western South Atlantic south of 28°S. The major problem in computing transport of the current is not with determining the correct reference depth, but with the Brazil Current flowing partially over the shelf and therefore not being sampled completely by deepwater hydrographic stations. As long as the vertical distribution of water masses is taken into account for choosing a reference depth, geostrophic computations lead to results consistent with previous esti-

89:6811 Wong, K.-C., 1989. Tidally generated residual currents in a sea level ¢,~nal or tidal strait with

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A. PhysicalOceanography

constant breadth and deoth. J. geophys. Res.,

94(C6): 8179-8192. The sea level canal is forced by tides from both open ends; residual Eulerian and Lagrangian currents induced by nonlinear interactions are strongly influenced by the tidal amplitude and phase differences between the two open boundaries. Depending on the type of boundary tidal forcing, the residual Eulerian velocity may flow in either direction; the Stokes velocity may work either in concert or in opposition with it, so the residual Lagrangian velocity may be even greater. Coll. of Mar. Studies, Univ. of Delaware, Newark, DE 19716, USA.

All0.

Water masses and fronts

89:6812 Bagriantsev, N.V., A.L. Gordon and B.A. Huber, 1989. Weddell Gyre: temperature maximum stratum. J. geophys. Res., 94(C6):8331-8334.

At depths below 200 m, relatively warm, salty water spreads poleward from the Antarctic Circumpolar Current (ACC). This deep water mass is cooled, through interaction with the atmosphere, feeding the formation of dense bottom water which in turn influences much of the World Ocean. Significant poleward spreading is accomplished within the Weddell Gyre. The seasonal sea ice growth and retreat pattern reflects the T-max distribution. There is evidence for subdivision of the T-max into two cold centers, which may reflect secondary circulation features within the gyre. The primary inflow of warm deep water is derived from the southern edge of the ACC near 20°-30°E. The inflow spreads to the west along 65°S and is divided into smaller pools of relatively warm water west of Maud Rise with a cold feature directly over the rise. Arctic and Antarctic Res. Inst., ulitsa Beringa, 38, 199226 Leningrad, USSR. 89:6813 Bourke, R.H., V.G. Addison and R.G. Paquette, 1989. Oceanography of Nares Strait and northern Baff'm Bay in 1986 with emphasis on deep and bottom water formation. J. geophys. Res., 94(C6): 8289-8302.

Temperatures and salinities were measured from northern Baffin Bay through Nares Strait to the southern edge of the Lincoln Sea in September 1986. Close station spacing led to the recognition of the rapid rate of dilution of Arctic Intermediate Water as it debouches into deeper water from the southern end of Kane Basin. As a result, this intermediate

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water becomes a much less likely source for the deep and bottom waters of Baffin Bay, which are more likely initiated by the formation of cold, saline water in winter in the shallows of eastern Smith Sound under the thin ice of the North Water. This water then undergoes multicomponent mixing en route to Baffin Bay. Dept. of Oceanogr., Naval Postgrad. School, Monterey, CA 93943, USA. 89:6814 Ogawa, Yoshihiko and Shimpei Moriwaki, 1986. A possible mechanism of fluctuations of so-called 'Bottom Cold Water' on the continental shelf. Bull. Tbhoku reg. Fish. Res. Lab., 48:97-114. (In Japanese, English abstract.)

This paper describes a possible mechanism to explain fluctuations of the low-temperature water on the continental shelves of the southwestern Japan Sea off Hamada, and reveals that the mechanism may be a coastal upwelling. Current fluctuations accompany changes in wind at sea; the long-shore component of current increases when that of wind stress increases, and vice versa. Long-shore velocity generated by a long-shore wind is found only in the surface mixed-layer. The geostrophic adjustment causes the rise or fall of a pycnocline known as up/downwelling. Such processes can be observed as fluctuations of the 'Bottom Cold Water'. 89:6815 Okuda, Kuniaki, 1986. Occurrence of extremely low temperature in the coastal region of the Tohoku area associated with interannual variations of the Oyashio. Bull. Tbhoku reg. Fish. Res. Lab., 48:87-96. (In Japanese, English abstract.)

This paper describes some specific features of the intrusion of Oyashio Water into the Tohoku coastal region using data gathered during the 1984 occurrence of extremely low near-surface temperature there. It is shown that this phenomena, which occurs at intervals of several years, is due to the outflow of ice-melt water from the Okhotsk Sea associated with the Oyashio intrusion. (emm) 89:6816 Smethie, W.M. Jr. and J.A. Swift, 1989. The tritium:krypton-85 age of Denmark Strait Overflow Water and Gibbs Fracture Zone Water just south of Denmark Strait. J. geophys. Res., 94(C6):8265-8275.

DSOW was the densest water observed in the section and there were two types, a low salinity type and a slightly higher salinity, more dense type; both originated from Arctic Intermediate Water behind the Greenland-Iceland Ridge. The low salinity type

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resided behind the Greenland-Iceland Ridge for about 1 year before flowing into the lrminger Sea, compared to about 15 years for the higher salinity type. The volume transport of the low salinity type of DSOW was estimated to have a lower limit of 0.8 Sv. G F Z W forms in the northeastern Atlantic from a mixture of water flowing out of the Norwegian Sea at about 900 m depth and the northeastern Atlantic water into which it flows. The age of G F Z W just south of Denmark Strait relative to its formation in the northeastern Atlantic is ~7.5 yr. LamontDoherty Geol. Observ., Palisades, NY 10964, USA.

89:6817 Watts, D.R., K.L. Tracey and A.I. Friedlander, 1989. Producing accurate maps of the Gulf Stream thermal front using objective analysis. J. geophys. Res., 94(C6):8040-8052. This extension of the OA method involves removing the mean field and normalizing the variance prior to performing OA; both fields are restored afterward. We test the sensitivity of the adapted OA method to variations in four control parameters: mean field, correlation function, standard deviation field, and input sampling interval. Specification of the mean field has the most influence upon the mapped fields, whereas the correlation function has more influence upon the estimated error fields. Using a timeaveraged mean field produces the best maps of the thermal field. The space-time correlation function is determined empirically from 5 years of inverted echo sounder data collected in the Gulf Stream. An input sampling interval 8t = 1 day (with input data only accepted within T = _+1 day) proved to be best. Within a reasonable variation of the control parameters, this adapted OA method is robust, and accurate maps of the thermal field are obtained. Grad. School of Oceanogr., Univ. of Rhode Island, Narragansett, RI 02882, USA. 89:6818 Whitehead, J.A., 1989. Surges of Antarctic Bottom Water into the North Atlantic. J. phys. Oceanogr., 19(6):853-861. Current meter records show that Antarctic Bottom Water surges into the western North Atlantic with roughly a sixty-day period. A time-dependent mass budget which incorporates estimated volume fluxes surges with a sixty-day period, a known time-average volume of the very coldest water in the North Atlantic, and a constant mixing coefficient predicts vertical excursions of 160-230 meters for the 1.1 ° isotherm and 45--60 meters for the 1.2 ° isotherm. Available data do not reveal such an excursion because earlier estimates of volume of the very coldest water were too small. Corrected tables are

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presented. The disagreement between current meter results and geostrophic calculations remains. Dept. of Phys. Oceanogr., WHOI, Woods Hole, MA 02543, USA.

AI20. Convergences, divergences, upwelling 89:6819 Flegal, A.R., T.F. Duda and S. Niemeyer, 1989. High gradients of lead isotopic composition in northeast Pacific upwelling filaments. Nature, Lond., 339(6224):458-460. Measurements of lead isotopes in two upwelling filaments off central California (39°N, 124°W) confirm that marked differences exist in stable lead isotopic composition in NE Pacific coastal waters. The distinct, filamentary structures appear in association with surface jets which transport cold upwelled water hundreds of kilometers offshore. Surface-water ratios of stable lead isotopes within the core of the filament (for example, 2°6Pb/2°TPb = 1.17) contrasted with those of surrounding coastal waters (2°6Pb/2°7pb = 1.19) and those of industrial lead aerosols (2°6Pb/2°7pb = 1.22). The lead within the cores was primarily derived from aeolian inputs of Asian industrial lead to remote waters, which were then upwelled near the North American coastline. High gradients in coastal waters illustrate the complexity of trace-element cycles in coastal waters. Inst. of Mar. Sci., Univ. of California, Santa Cruz, CA 95064, USA.

89:6820 Garzoli, S.L. and Zulema Garraffo, 1989. Transports, frontal motions and eddies at the BrazilMalvinas currents confluence. Deep-Sea Res., 36(5A):681-703. The time-averaged geostrophic velocity of the Brazil Current (relative to 800 m) during the observed period is 35 + 2.2 cm s-~ and the mean transport is 11 Sv. For the Malvinas Current return flow, the mean geostrophic velocity is 9_+ 2.0 cm s ~ and the mean associated transport 3.5 Sv. The main motion of the front is an E-W displacement for distances of about 100 kln; the observed period occurs with a periodicity of 12 months and is related to a variability in the latitude of maximum northward penetration of the Malvinas Current. Motions of the front, with a period of 1-2 months, are probably related to a N-S variation of the latitude of return of the Brazil Current. Lamont-Doherty Geol. Observ., Palisades, NY 10964, USA.

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A. Physical Oceanography

89:6821 Halpern, David et al., 1989. Estimates of equatorial upwemng between 140 ° and l l 0 ° W during 1984. J. geophys. Res, 94(C6):8018-8020. The equation of continuity is used to estimate profiles of vertical velocity between 25 and 120 m from moored current measurements in arrays nested within the triangle with vertices located at 1°30"S, 140°W and along the Equator at 140 ° and 110°W during December 1983 through March 1984 and May-September 1984. All directions of the 4- to 5-month mean values were upward. The ensemble averaged mean vertical velocity was 2.2 × 105 m s ~. Upwelling speeds decreased eastward. Jet Propulsion Lab., California Inst. of Tech., 4800 Oak Grove Dr., Pasadena, CA 91109, USA. 89:6822 Monin, A.S., R.V. Ozmidov and V.T. Paka, 1988. Hydrophysical mesostructure of a coastal upwelting. DokL Earth Sci. Sect. (a translation of Dokl. Akad. Nauk SSSR), 297(1-6):218-221. The Canary Upwelling is considered here as an example of a coastal upwelling, using measurements made on a variety of hydrophysical fields at high spatial resolution ( ( 1 0 cm) during a 1987 cruise of the R/V Akademik Mstislav Keldysh as a basis for the discussion. Shirshov Inst. of Oceanol., Acad. of Sci., Moscow, USSR. (emm)

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Pacific tides govern the whole of the China Sea, Philippine waters and the Sulawesi Sea, while Indian Ocean tides govern the Timor, Banda, and Andaman seas and the Malacca Strait; the Maluku Sea, the Makassar Strait and the Java Sea comprise the boundary region between. At the boundary region, the amplitudes are generally very small. As an example of a boundary region, the tides of the Sunda Strait are considered in some detail. Ctr. for Oceanol. Res. and Develop., LIPI, Jakarta, Indonesia. 89:6825 Miller, R.N. and M.A. Cane, 1989. A Kalman filter analysis of sea level height in the tropical Pacific. J. phys. Oceanogr., 19(6):773-790. In this study, it is assumed that the model errors are dominated by the errors in the wind stress analysis. The error model is a simple covariance function with parameters fit from the observed differences between the tide gauge data and the model output, consistent with independent estimates. The calibrated error model is used in a Kalman filtering scheme to generate monthly sea level height anomaly maps which exhibit finestructure that is absent from the unfiltered model output, even in regions removed from the data insertion points. Error estimates suggest that the filter reduces the error in the equatorial waveguide by about 1 cm. Coll. of Oceanogr., Oregon State Univ., Corvallis, OR 9733 l, USA.

AI50. Tides and sea level 89:6823 Carton, J.A., 1989. Estimates of sea level in the tropical Atlantic Ocean using Geosat altimetry. J. geophys. Res., 94(C6):8029-8039.

89:6826 Molodensky, S.M., 1989. Asymptotic behaviour of solutions to Laplace's tidal equations at low frequencies. Geophys. J., 97(3):459-469.

Between l0 ° and 20°N the sea level shows a westward North Equatorial Current from July to April. Between 4 ° and 6°N an intense North Equatorial Countercurrent (NECC) exists throughout much of the year with geostrophic velocities exceeding I m/s. The branch of the South Equatorial Current south of the Equator prevails throughout most of the year west of 10°W. The zonal sea level slope along the Equator reflects intensification of currents and large-scale redistribution of water in response to seasonal winds. Of the month-to-month variability of sea level, over half is described by the annual cycle. Dept. of Meteorol., Univ. of Maryland, College Park, M D 20752, USA.

The method used is based on perturbation in small parameters, these being the ratios of tidal frequency and the coefficient of bottom friction to the angular frequency of the Earth's rotation. The resulting solutions are unstable; because of this, direct methods of numerical integration are inefficient. We propose replacing the original set of equations in partial derivatives by ordinary differential equations that have a stable solution. For the case of an ocean of uniform depth over the whole Earth, they coincide with the well-known Lamb's equations. Their asymptotic behaviour is examined as modified by basin shape, bottom topography and bottom friction. Inst. of the Phys. of the Earth, Bolsehaya Gruzinskaya 10, 123810 Moscow D-242, USSR.

89:6824 Kastoro, 1987. The semidim'nal M 2 tide in the southeast Asian waters. Mar. Res. Indonesia, 26:13-28.

89:6827 Nakamura, Shigehisa, 1988. Spectrum of the annual tide S, and its side rohe along the southwest coast of the Kii Penlmala. Mer, Tokyo, 26(2):76-80. (In

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Japanese, English abstract.) Shirahama Oceanogr. Observ., Disaster Prevention Res. Inst., Kyoto Univ., Katada-Hatasaki, Shirahama, Wakayama, 649-22, Japan. 89:6828 Rosenthal, Gerald and Stephen Grant, 1989. Simpfified tidal prediction for the South Mrican coastline. S. Aft. J. Sci., 85(2):104-107. The tide level predictions, which use some precalculated constants, may be obtained with a calculator or small computer. A comparison is given between results obtained using this simplified approach and those of a more detailed 51-constituent analysis such as is used by the S.A. Navy Hydrographic Office. Dept. of Civil Engng, Univ. of Cape Town, Rondebosch, 7700 South Africa.

AI60. Waves, oscillations 89:6829

Cavaleri, Luigi, Luciana Bertotti and Piero Lionello, 1989. Shallow water application of the thirdgeneration WAM wave model. J. geophys. Res., 94(C6):8111-8124. The results of detailed tests of the third-generation WAM wave model, carried out under well-known conditions, and chosen to check different aspects of the model are presented. The test area is the shallow northern part of the Adriatic Sea, east of Italy. Results show the model's capability of responding equally well to different meteorological situations. Some discrepancies present at short nondimensional fetch and in shallow water are addressed with different formulations for breaking and bottom friction. Inst. per lo Studio della Dinamica delle Grandi Masse, Palazzo Papadopoli, 1364 San Polo, 30125 Venice, Italy. 89:6830

Herrmann,

Peter and Wolfgang Krauss,

OLR (1989) 36 (12)

Atlantic. Krauss: Inst. fur Meereskunde Kiel, Dursternbrooker Weg 20, D-2300 Kiel 1, FRG. 89:6831 Holthuijsen, L.H., N. Booij and T.H.C. Herbers, 1989. A prediction model for stationary, shortcrested waves in shallow water with ambient currents. Coast. Engng, Amst., 13(1):23-54. The model is based on a Eulerian presentation of the spectral action balance of the waves rather than on the more conventional Lagrangian presentation; wave propagation is correspondingly computed on a grid rather than along rays. The effects of wave growth and dissipation due to wind generation, bottom dissipation and wave breaking are represented as source terms in the action balance equation. The computational efficiency of the model is enhanced by two simplifications: the removal of time as an independent variable to obtain a stationary model, justified by the relatively short travel time of waves in coastal regions; and parameterization of the basic balance equation in terms of a mean frequency and a frequency-integrated action density, both as function of the spectral wave direction. The discrete spectral representation of wave directionality is thus retained. Delft Univ. of Tech., P.O. Box 5048, 2600 G A Delft, Netherlands. 89:6832

Le M6haut¢, Bernard et al., 1987/88. Generation of transient waves by snake paddle. Ocean Phys. Engng, 12(3,4): 197-213. A general formulation is presented for determining the motion required of a programmable 'snake paddle' wave machine for simulating impulsive water waves such as tsunamis. The formulation, as well as the theory of transient wave propagation and transformation, are verified by wave tank experiments. Div. of Appl. Mar. Phys., RSMAS, 4600 Rickenbacker Cswy, Miami, FL 33149-1098, USA. (fcs)

1989.

Generation and propagation of annual Rossby waves in the North Atlantic. J. phys. Oceanogr~

19(6):727-744. Annual Rossby waves emanating off the eastern coast are strongly influenced by the Mid-Atlantic Ridge. West of the M A R a relative minimum of energy is observed. The waves are influenced and modified by variable bottom topography. In the western basin Rossby waves are generated in two regions, the Gulf Stream and its extension toward the east, and the southern flank of the subtropical gyre. Compared to the North Pacific, annual Rossby waves seem to be less energetic in the North

89:6833

Maggs, W.W., 1989. News. New fide on an old wave [inverse theory applies to tsDamls I. Eos, 70(23): p.642. For many years inversion theory has been used to reconstruct from seismic waves the complex tectonic motions along fault planes associated with earthquakes. Now a Japanese seismologist, Kenji Satake, has shown that the same methodology can be applied to tsunami waveforms, thus providing a method independent of seismic analysis (when tide gauge time series are available) for looking at past earthquakes for which seismic data are not available.

OLR (1989) 36 (12)

A. Physical Oceanography

89:6834

Myrhaug, Dag, 1989. A rational approach to wave friction coefficients for rough, smooth and transitional turbulent flow. Coast. Engng, Amst., 13(1):11-21. The wave friction coefficient (fw) and the phase lead of the bottom shear stress over the free-stream velocity (ep) for rough, smooth and transitional smooth-to-rough turbulent flow are presented. The analogy between wave boundary layer flow and planetary boundary layer flow is utilized using similarity theory; results are obtained forfw and ep by determining the constants. An approximation for f~ by disregarding the phase q, is also presented. Comparisons are made with experimental data. Div. of Mar. Hydrodyn., Norwegian Inst. of Tech., N-7034 Trondheim-NTH, Norway. 89:6835

Nielsen, Peter, 1989. Wave setup and runup: an integrated approach. Coast. Engng, A mst., 13(1): 1-9. It is shown that the elevation of the shore line on an impermeable beach is logically at the runup limit, not at the average water-line level. Thus, the runup limit becomes a point on the setup profile. A first approximation to a universal description of setup profiles is derived, i.e. the most appropriate vertical and horizontal scaling parameters are suggested for the shape of the mean water surface in the inner surf zone. Traditional models are inadequate for modelling the shape of the most landward part of the mean water surface and hence for predicting the shoreline setup; instead, it is suggested that estimates of the shoreline setup be based on the relation between this quantity and the maximum runup height together with well-proven runup formulae. Coast and Rivers Br., Public Works Dept., 140 Phillip St., Sydney, NSW 2000, Australia. 89:6836

Ryu, C.-R., H.-J. Kim and J.-W. Kim, 1989. Analysis on variation of ocean wave statistics. Bull. Korean Fish. Soc., 22(1):41-47. (In Korean, English abstract.) Using computer simulated irregular waves, variations of ocean wave statistics according to sea state are analyzed, and the reasonable conditions that transform the energy spectrum to individual wave statistics are discussed. Ocean wave statistics varying with sea state respond linearly to the spectral peakedness parameter and spectrum moments. The 2nd-order spectrum moment is a reasonable parameter which represents the wave statistics including wave periods, and the spectrum analysis should be

1051

carried out under conditions of minimum data length of 10 times of peak period Tp with time lag of 7 Tp to satisfy stable wave statistics. Dept. of Engng, Natl. Fish. Univ., Pusan 608-737, Korea. 89:6837

Schmitz, H.P., D. Habicht and H. Volkert, 1988. Barotropic numerical experiments on external

surge generation at the edge of the northwestern European shelf. Gerl. Beitr. Geophys., 97(5):422437. The development of external surges and conditions for their propagation into the North Sea are examined on the base of circular surface pressure distributions on two passages, with regard to the available simulation of the external surge generation during storm surge events on 19-21 January 1976. An eastward course of a cyclone propagating from the sea between Ireland and Iceland to Mid-Norway proves predestined to send a surge into the North Sea, whilst a low moving south-easterly over Scotland seems to prevent the induced oceanic surge from entering. Inst. fur Geophys., Wissenschaften der Freien Univ. Berlin, Thielallee 50, D-1000 Berlin, FRG. 89:6838

Tou, S.K.W., 1987/88. Statistical and spectral analysis of sea waves in the South China Sea. Ocean Phys. Engng, 12(3,4): 167-196. A statistical and spectral analysis of sea waves in the South China Sea is made that shows favorably in comparisons with theoretical/empirical formulations. Wave characteristics and structure are also discussed. School of Mech. and Prod. Engng, Nanyang Tech. Inst., Nanyang Ave., 2263 Singapore. (fcs)

AI70. Wind-wave interactions 89:6839

DeLeonibus, P.S. and L.S. Simpson, 1989. Observations of the yon Karman constant over openocean waves. I E E E Jl ocean. Engng, 14(3):248-

253. Forty-six open-ocean observations of the yon Karman constant k, estimated from the momentum flux, wind velocity, and air temperature differences observed at the Argus Island tower, yielded an average value of 0.40___0.18 for Ri <0.014. This average value agrees with recent determinations of k over land. Scatter in these oceanic data sets may be due in part to ocean-wave influence as well as to

1052

A. PhysicalOceanography

instrumental and statistical variability. Oceanic Sci. Branch, NOAA, NESDIS, Suitland Prof. Ctr., Washington, DC 20233, USA.

A180. Internal waves and tides 89:6840 Chereskin, T.K. et al., 1989. Observations of nearinertial waves in acoustic Doppler current profiler measurements made during the Mixed Layer Dynamics Experiment. J. geophys. Res., 94(C6): 8135-8145.

Measurements of upper ocean shear provide evidence of large horizontal scale motion at nearinertial frequency. Velocity time series from the drifting buoy and from sonar measurements made from F L I P also indicated the presence of motions at near-inertial frequency. Estimates of the length scale of the waves range from 500 to 1000 km, and the frequency is ~ 1. If. Phase behavior is consistent with a model of narrow-band inertial waves with vertical structure such that there is a zero crossing in velocity at the base of the mixed layer (40-60 m). Scripps Inst. of Oceanogr., La Jolla, CA 92093, USA. 89:6841 Levine, M.D. and J.G. Richman, 1989. Extracting the internal tide from data: methods and observarious from the Mixed Layer Dynamics Experiment. J. geophys. Res., 94(C6):8125-8134.

Several methods are developed for analyzing data containing a highly variable internal tide. The analysis depends upon an 'elliptical decomposition' that is a generalization of the familiar 'rotary decomposition." The observed propagation direction and amplitude of the internal tide about 700 km west of Santa Barbara, California, was highly variable in time. It was anticipated that the wave could be propagating from the continental shelf where it is presumed to be generated; however, most of the time the internal tide appears to be propagating parallel to the coast. This suggests the importance of mesoscale and frontal-scale density and velocity structure in affecting the propagation of the internal tide. Coll. of Oceanogr., Oregon State Univ., Corvallis, OR 97331, USA. 89:6842 Padman, Laurie and T.M. Dillon, 1989. Thermal m i c ~ and internal waves in the Canada Basin diffusive staircase. Deep-Sea Res., 36(4A): 531-542.

Measurements of thermal microstrncture in the Canada Basin thermohaline staircase are used to

OLR (1989) 36 (12)

investigate the mechanisms of oceanic doublediffusive convection. Thermal interface thicknesses, the presence and scales of anomalous parcels near the diffusive interfaces, and an estimated decay time scale for these anomalies are all consistent with previous models based on laboratory and analytical studies in which heat transport consists of molecular diffusion through a stable interface core, intermittent separation of unstable boundary layers, and subsequent diffusion into the adjacent convective layers. It is shown, however, that in the Canada Basin shear instabilities driven by the internal wave field may significantly modify the vertical fluxes, in particular salt, and may be sufficient to reverse the direction of total buoyancy transport without destroying the staircase. Coll. of Oceanogr., Oregon State Univ., Corvallis, OR 97331, USA. 89:6843 Pierini, Stefano, 1989. A model for the Alboran Sea internal solitary waves. J. phys. Oceanogr., 19(6): 755-772.

The propagation into the Alboran Sea of the interface depression generated at the Strait of Gibraltar by the interaction of the semidiurnal tidal current with the main sill is studied numerically. An initial waveform within the strait is determined whose evolution corresponds with the train of internal solitary waves detected in the Alboran Sea. The shape and amplitude of this initial condition are in agreement with a typical interface depression generated in the strait by the interaction of the tidal current with the sill. A series of numerical experiments with different initial conditions is performed to study the sensitivity of model results to changes in the initial internal wave; the reason why solitary waves may or may not be observed in the western part of the Alboran Sea is thus clarified. Ist. di Oceanol., Ist. Univ. Navale, Via Acton 38, 80133 Napoli, Italy. 89:6844 Pingree, R.D. and A.L. New, 1989. Downward propagation of internal tidal energy into the Bay of Biscay. Deep-Sea Res., 36(5A):735-758.

The generation and propagation of internal tidal energy from the continental shelf break is determined by the gradient of the topography and the static stability of the water column. This paper presents convincing evidence for the existence of a beam of internal tidal energy propagating downward, from a source region on the upper continental slopes, into the deep ocean interior along a theoretical ray path. Although this phenomenon has been previously described, it has never before, to our

OLR (1989)36 (12)

A. PhysicalOceanography

knowledge, been observed in nature. The observations are compared with model results and good agreement is obtained. Plymouth Mar. Lab., Citadel Hill, Plymouth, Devon PLI 2PB, UK. 89:6845 Tee, K.-T., 1989. Subtidal salinity and velocity variations in the St. Lawrence Estuary. J. geophys. Res., 94(C6):8075-8090. Dept. of Fish. and Oceans, Bedford Inst. of Oceanogr., Dartmouth, NS, B2Y 4A2, Canada.

A210. Ice

1053

are also distinguishable by the lidar backscatter from adjacent thicker, older sea ice. Wide leads release enough energy to create buoyant plumes which penetrate the Arctic boundary layer inversion, transporting heat and moisture into the troposphere. These results show that the role of the Arctic as a global heat sink may need to be re-evaluated, and that lead plumes have a significant effect on the radiation budget. CIRES, Univ. of Colorado, Boulder, CO 80309, USA.

A240. Optical properties

89:6846 Bredow, Jonathan et al., 1989. Radar backscnttering from artificially grown sea ice. IEEE Jl ocean. Engng, 14(3):259-264. Radar Syst. and Remote Sensing Lab., Univ. of Kansas, Lawrence, KS 66045-2969, USA.

89:6850 Nosov, V.N. and S.Yu. Pashin, 1988. Effect of large-scale waves on the accuracy of optical measurements of sea surface characteristics. Izv. Atmos. Ocean Phys. (a translation of Fiz. Atmos. Okeana), 24(1):37-40.

89:6847 DeLisle, G. et al., 1989. Radio echo-sounding of Erebns Glacier Tongue. N.Z..4nturct. Rec., 9(1):!5-30.

A260. Acoustics

A radio echo-sounding survey in December 1985 was continued up onto the neve east of the tongue, where ice thicknesses were obtained for the first time. Results for the floating section in general confirm those of previous surveys in 1967, 1978 and 1984. Limits on presumed depths and extents of surface crevassing are offered. The general southerly flow of neve area ice turns westward and debouches into the tongue at a depression presumed to be a volcanic crater. Surface slopes and deep snow drift indicate that a significant part of the tongue ice originates from accumulation in and around this depression. Fed. Inst. for Geosci. and Nat. Res., Hannover, FRG. 89:6848 Eicken, Hajo and M.A. Lange, 1989. Development and properties of sea ice in the coastal regime of the southeastern Weddell Sea. J. geophys. Res., 94(C6):8193-8206. Alfred Wegener Inst. fur Polar und Meeresfors., Columbusstr., D-2850 Bremerhaven, FRG. 89:6849 Schnell, R.C. et al., 1989. Lidar detection of leads in Arctic sea ice. Nature, Loud., 339(6225):530-532. Vertical profiles of backscattered radiation demonstrate strong returns from hydrometeor plumes originating from leads having a surface water temperature near -1.8°C. Recently refrozen leads

89:6851 Bogdanov, K.T. et al., 1988. An experiment on the propagation of acoustic signals in a new type of acoustic channel. Dokl. Earth Sci. Sect. (a translation of Dokl. Akad. Nauk SSSR), 297(16):216-218. Acoustic experiments were performed within the frontal zone of the northwestern Pacific Ocean to study a novel type of sound channel. A vertical string of hydrophones towed along the sound channel over a distance of 620 miles recorded acoustic tones emitted at 850 Hz by a relatively stationary ship. Although preliminary, the data confirm both the existence and relative stability of the putative sound channel. Pacific Oceanol. Inst., Far Eastern Dept., Acad. of Sci., Vladivostok, USSR. (emm) 89:6852 Cobo-Parra, P. and C. Ranz-Guerra, 1989. Impedance profile and overall attenuation estimation of layered sea bottoms from their normal incidence acoustic reflection response. J. acoust. Soc. Am., 85(6):2388-2393. Inversion of high-frequency acoustic reflection data in low-noise layered sea bottoms is presented. The assumed geoacoustic model includes attenuation effects. An overall attenuation coefficient of the whole sedimentary column is estimated by logarithmic regression on the spectral ratio of honorerlapped replicas. The attenuation response is filtered

1054

A. PhysicalOceanography

out of the impulse response by the minimum square inversion of the sea bottom lossy transfer function, previously computed by deconvolving the input pulse from the reflection response. Applying this inversion scheme to a known artificial bottom, experimental values lying within a 7.4% range below actual data are obtained. Hydroacoustics Lab., Inst. de Acustica, CSIC, C/Serrano, 144-28006 Madrid, Spain. 89:6853 Ferguson, B.G., 1989. Improved time-delay estimates of underwater acoustic signals using beanfforming and prefiltering techniques. I E E E J l ocean. Engng, 14(3):238-244. Maritime Syst. Div., Defence Sci. and Tech. Org. (Syndey), P.O. Box 706, Darlinghurst, NSW 2010, Australia. 89:6854 Feuillade, C., D.R. Del Baizo and M.M. Rowe, 1989. Environmental mismatch in shallow-water matched-field processing: geoaconstic parameter variability. J. acoust. Soc. Am., 85(6):2354-2364. The effects of variations in geoacoustic environmental parameters on the performance of a matched-field localization processor in shallow water were investigated. It was found that small perturbations in a downward-refracting summer water sound-speed profile of _+ 1o from average measured values caused severe degradation in localization performance, with predictions of source range and depth becoming highly unstable. However, similar perturbations of an almost isospeed winter profile caused comparatively little degradation. Similarly, perturbations in the sediment soundspeed profile of up to _+ lo from average measured values were possible while still giving stable and reliable estimates of source location. The source was correctly localized even when the density and attenuation deviated by significantly more than _+ lo from average measured values. Syntek Engng and Computer Syst. Inc., 2101 E. Jefferson St., Rockville, MD 20852, USA. 89:6855 Goncharov, V.V. and V.M. Kurtepov, 1988. Numerical experiments on ocean tomography. Dokl. Earth Sci. Sect. (a translation of Dokl. Akad. N a u k S S S R ) , 297(1-6):239-242. In this paper we describe the derivation of a tomographic image of the sound velocity field in a real ocean eddy and evaluate the accuracy and stability with which that medium can be reconstructed when various elements of the tomographic scheme are varied. In synoptic inhomogeneities the rays almost never wander from the vertical plane

OLR (1989)36 (12)

containing the emitter and receiver, but incur an additional variation in their travel time of several milliseconds. It is therefore useful to reconstruct the medium independently in each such vertical cross section and to use some existing method of interpolation for the intervals between them. Shirshov Inst. of Oceanol., Acad. of Sci., Moscow, USSR. 89:6856 McDaniel, S.T., 1989. Vertical spatial coherence of scattering from the Arctic ice canopy: comparison of theory with experiment. J. acoust. Soc. Am., 85(6)'2378-2382. Appl. ges. Lab., Pennsylvania State Univ., Univ. Park, PA 16804, USA. 89:6857 Mellen, R.H., 1989. On underwater sound scattering by surface waves. I E E E J l ocean. Engng, 14(3): 245-247. An angular-scattering approach is outlined that provides insight into some of the elementary acoustics involved in the perturbation theory of underwater sound scattering by surface waves. 89:6858 Pogorzelski, S.J., 1989. Detection of oil-derivative contamination of water surfaces by statistical analysis of scattered acoustical signals. J. acous y Soc. A m , 85(6):2382-2387. The statistical distribution of the amplitude of the acoustical signal scattered by a water surface undulated by an air stream was studied under laboratory conditions. The surface was covered with layers of oil substances of different physical properties. Statistical parameters of the distribution were determined as functions of the speed of the air stream and thickness of the oil layer. Values of obtained parameters differ from those expected for the scattering on the surface of clean water. Simultaneous analysis of all the statistical parameters could be a starting point for determining the weight fraction of the given substance and its thickness. Environ. Acoustics Lab., Univ. of Gdansk, Wita Stwosza 57, 80-952 Gdansk, Poland. 89:6859 Tolstoy, A., 1989. Sensitivity of matched field processing to sound-speed pmf'fle nismatch for vertical arrays in a deep water Pacific environment. J. acoust. Soc. A m y 85(6):2394-2404. A 10-Hz source is considered whose field is generated by a normal mode model and only the waterborne energy is used, thereby eliminating issues relating to the estimation of bottom parameters. This paper will examine how array parameters (number

OLR (1989) 36 (12)

A. Physical Oceanography

of phones and array depth) affect range and depth localization for various degrees of mismatch, in particular where an array is most and least sensitive to sound-speed mismatch as a function of depth from the surface and range from the source, and the degree to which range and depth resolution are possible under ideal, as well as under likely, mismatch conditions. U.S. Naval Res. Lab., Washington, DC 20375-5000, USA.

A290. Physical processes, properties (diffusion,

turbulence, etc.)

89:6860 Boyd, J.D., 1989. Properties of thermal staircases off the northeast coast of South America, spring and fall 1985. J. geophys. Res., 94(C6):8303-8312.

AXBT surveys revealed an extensive field of subthermocline thermal staircases which is probably the site of vigorous salt fingering. During both seasons the staircases were shallowest in the south (180-360 m) and deepest in the northwest (420-650 m), occurring on the average between the 8 ° and 13°C isotherms. Typically, each staircase consisted of 10 well-mixed layers with average thickness of 16 m and average interlayer temperature change of 0.52 ° . Thicker layers seemed to be associated with larger temperature changes. The sharp northeastern staircase field boundary occurs at the confluence of the Subtropical Underwater and the Antarctic Intermediate Water, suggesting that the staircases may be formed in this region and then extend south and west to form the rest of the field. Phys. Oceanogr. Br., NORDA, Stennis Space Ctr., MS 39529, USA.

89:6861 Lewis, J.K., A.D. Kirwan Jr. and G.Z. Forristall, 1989. Evolution of a warm-core ring in the Gulf of Mexico: Lagrangian observations. J. geophys. Res., 94(C6):8163-8178.

During 1985 and 1986, a Gulf of Mexico ring shed by the Loop Current was observed to migrate toward the western Gulf of Mexico. This movement across the gulf was well documented, and the drifter data were used to infer the movement of the ring center as well as the eccentricity and orientation of the major axes. Data from the drifters bridge gaps between detailed surveys so that a daily history of the position and shape of the ring can be constructed. Synthesis of these diverse data sources provides a detailed description of how the ring interacted with

1055

the bathymetry of the northern Gulf of Mexico as well as with previously and subsequently shed rings. Sci. Applic. Intl. Corp., 1304 Deacon, College Station, TX 77840, USA. 89:6862 Nelson, J.M. and J.D. Smith, 1989. Mechanics of flow over ripples and dunes. J. geophys. Res., 94(C6): 81 46-8162.

The production of a wake due to flow separation near the bedform crest and the subsequent interaction of this wake region with a developing nonuniform boundary layer downstream of the flow reattachment point are treated using a modification of McLean and Smith's (1986) model. Results are in good agreement with laboratory measurements taken over immobile bedforms using a laser-Doppler velocimeter. Our finite amplitude flow model is shown to yield accurate predictions of the fluid dynamical effects ultimately responsible for the morphology of well-developed natural bedforms. USGS, Water Resources Div., Lakewood, CO 80225, USA. 89:6863 Samelson, R.M., 1989. Stochastically forced current fluctuations in vertical shear and over topography. J. geophys. Res., 94(C6):8207-8215.

The effects of constant vertical shear of zonal velocity, uniform meridional bottom slope, and a deep meridional wall (representing the Mid-Atlantic Ridge) on the response of a linear two-layer quasi-geostrophic ocean to stochastic wind stress curl forcing are investigated. Results indicate that the presence of mean shear can significantly enhance the wind generation of surface-intensified oceanic kinetic energy at frequencies above the zero-shear cutoff for free baroclinic waves. The primary effect of the sloping topography is enhanced barotropic response. The wall inhibits the barotropic response and increases coherences on the mooring side of the wall. WHOI, Woods Hole, M A 02543, USA. 89:6864 Speer, K.G., 1989. A forced Imroclinic vortex around a hydrothermal plume. Geophys. Res. Letts, 16(5):461-464.

A steady, frictional flow around a hydrothermal plume is described which is forced by the entrainment of water into the buoyant part of the plume as it rises above its source. The circulation is anticyclonic near the equilibrium density level or spreading level of the plume, and cyclonic below this

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OLR (1989) 36 (I 2)

level. The strength of this flow is adequate to trap anomalous properties from the hydrothermal fluid near the source in the presence of weak background flow. Some observational support for such a flow is presented. I F R E M E R DERO/EO, B.P. 70, 29263 Plouzane, France.

89:6869 Fiedler, B.H., 1989. Validation study of scale selection in low-order models of Rayleigh-B6nard convection. Tellus, 41A(4):285-291. School of Meteorol., Univ. of Oklahoma, Norman, OK 73019, USA.

89:6865 Whitfield, D.W.A., G. Holloway and J.Y. Holyer, 1989. Spectral transform simulations of finite amplitude double-diffusive instabilities in two dimensions. J. mar. Res., 47(2):241-265. Whitfield Software Serv., Hornby Island, BC V0R IZ0, Canada.

89:6870 Gvaramadze, V.V., G.A. Khomenko and A.V. Tur, 1989. Large-scale vortices in helical turbulence of incompressible fluid. Geophys. astrophys. Fluid Dynam., 46(1-2):53-69. Tbilisi City Dept., Abastumani Astophys. Obs., Acad. of Sci. Georgian SSR, Pavlova ul., 2-A, Tbilisi SU380060, USSR.

89:6866 Yasuda, Ichiro, Kuniaki Okuda and Keisuke Mizuno, 1986. Numerical study on the vortices near boundaries: considerations on warm core rings in the vicinity of east coast of Japan. Bull. Tbhoku reg. Fish. Res. Lab., 48:67-86. (In Japanese, English abstract.)

The behavior of nonlinear isolated vortices near the western boundaries on a beta-plane are modelled numerically with consideration given to dependencies on the local Rossby number, the internal Froude number, and boundary conditions. Results for inviscid and anticyclonic vortices, with beta zero or non-zero, and in the presence or absence of slip are given and the mechanism of the northward movement of warm core rings along the Japan and Kurile-Kamchatka trenches is discussed. (emm)

A300. Fluid mechanics 89:6867 Christensen, U.R., 1989. The heat transport by convection roils with free boundaries at high Rayleigh number. Geophys. astrophys. Fluid Dynam., 46(1-2):93-103. Dept. of Geochem., Max-Planck-lnst. fur Chem., Saarstr. 23, 6500 Mainz, FRG.

89:6868 Fiedler, B.H., 1989. Scale selectioh in nonlinear thermal convection between poorly conducting

boundaries. Geophys. astrophys. Fluid Dynam., 46(3):191-201. School of Meteorol., Univ. of Oklahoma, Norman, OK 73019, USA.

89:6871 McDougall, T.J., 1989. Streamfunctions for the lateral velocity vector in a compressible ocean. J. mar. Res., 47(2):267-284. CSIRO, Div. of Oceanogr., GPO Box 1538, Hobart, Tas. 7001, Australia.

89:6872 Robinson, W.A., 1989. On the structure of potential vorticity in baroclinic instability. Tellus, 41A(4): 275-284. Dept. of Atmos. Sci., Univ. of Illinois, Urbana, IL 61801, USA.

89:6873 Ruddick, B.R., T.J. McDougall and J.S. Turner, 1989. The formation of layers in a uniformly stirred density gradient. Deep-Sea Res., 36(4A): 597-609.

Experiments are described in which an initially smooth density gradient breaks down into a regular series of steps and layers when it is stirred weakly by an array of vertical rods. When stirring is more vigorous, layers do not form, and irregularities in the density gradient tend to be smoothed out. The observed behaviour lends strong support to the hypothesis that if the buoyancy flux is a decreasing function of Richardson number, then an instability occurs that leads to the formation of finestructure from a smooth density gradient. Any local increase in density gradient inhibits the buoyancy flux at that level, allowing the density gradient to steepen further. The scale of the layers that are formed, the variation of buoyancy flux with stirring rate, and the effects of intermittent stirring are also discussed. Dept. of Oceanogr., Dalhousie Univ., Halifax, NS B3H 4JI, Canada.