Oceanographic Literature Review

(1990) 37 (3)

The citations are those received in the editorial office during the period 1-31 December, 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

90:1402 Derber, John and Anthony Rosati, 1989. A global

oceanic data assimilation system. J. phys. Oceanogr~ 19(9): 1333-1347.

The system uses a high resolution global ocean model to extrapolate the information forward in time; data inserted into the model currently consists only of conventional SST observations and vertical temperature profiles. Large scale features in the SST analyses are consistent with those from independent analyses. Subsurface fields created from the assim- ilation are much more realistic than those produced without the insertion of data. Information contained in the assimilation field is retained in the model solution after the assimilation procedure is termi- nated. NOAA, NWS, World Weather Bldg., Rm 204, Washington, DC 20233, USA.

90:1403 Durden, S.L. and J.F. Vesecky, 1989. On the ability

of rough surface scattering approximations to predict hydrodynamic modulation of the ocean radar cross section: a numerical study. J. geophys. Res~ 94(C9): 12,703-12,708.

In this report we study the ability of the Bragg and two-scale (composite) models to predict spatial or temporal modulation of the normalized radar cross section caused by spatial or temporal changes in ocean surface roughness, such as those due to the presence of internal wave surface effects. Bragg and two-scale cross section models are compared with cross sections calculated by a numerical electro- magnetic approach. For slightly rough surfaces, the Bragg model is very accurate; however, for much rougher surfaces, the two-scale model is superior and should be used for calculating both the absolute cross section and the change in cross section due to

214 A. Physical Oceanography OLR (1990)37 (3)

spatial or temporal modulation of the ocean wave height spectrum. Jet Propulsion Lab., California Inst. of Tech., 4800 Oak Grove Dr., Pasadena, CA 91109, USA.

A40. Area studies, surveys

90:1404 Hanawa, Kimio and Naoto Iwasaka, 1988. Char-

acteristics of SST variations in the western North Pacific: partition of the North Pacific based on similarity in temporal variation of SST and its relationship to the ENSO events. Umi to Sora, 64(1):31-42. (In Japanese, English abstract.)

Two approaches to partitioning the western North Pacific are reported here. Iwasaka et al. (1988), using cluster analysis, have shown that the North Pacific can be partitioned into 4 distinct domains based on cluster analysis with respect to similarities in tem- poral variations of SST, while Hanawa et al. (1988), using composite analyses, have demonstrated spatial heterogeneity in. the western North Pacific during ENSO years. Dept. of Geophys., Tohoku Univ., Sendal, Japan. (cram)

90:1405 Meyers, Gary et al., 1989. Design of an ocean

temperature observing network in the seas north of Australia. Part 1. Tropical Pacific Ocean: statistics. CSIRO mar. Labs Rept, 204:50pp.

This report is a compilation of the statistical data required for design of an ocean temperature ob- serving network in the tropical Pacific, using the method of optimum interpolation (OI). The statistics were estimated from a data base of XBT obser- vations on shipping routes between New Caledonia and Japan and Hawaii and Tahiti-Panama. The temporal:and meridional autoeorrelation function (ACF) for SST and depth of the 20~ isotherm was estimated at each degree latitude on each route. Additional data were used to estimate the zonal ACF. The ACF statistics permit estimation of the parameters required for OI; these parameters are then summarised in large areas selected to represent the major currents. CSIRO Div. of Oceanogr., Hobart, Tas., Australia.

90:1406 Perillo, G.M.E. et al., 1989. Hydrography and

circulation of the Chubut River Estuary (Argen- tim). Estuaries, 12(3):186-194. Inst. Argentino de Oceanogr., Av Alem 53, 8000 Bahia Blanca, Argentina.

90:1407 Ripa, P. and S.G. Marinone, 1989. Seasonal varia-

bility of temperature, salinity, velocity, vorticity and sea level in the central Gulf of California, as inferred from historical data. Q. Jl R. met. Soc. 115(488):887-913.

Temperature, across-gulf integrated velocity, sea level, and salinity have a significant seasonal cycle. The last variable has an important semi-annual component, presenting four extremes per year. The others are mainly annual, reaching their maximum values in summer and their minima in winter. By interaction with the atmosphere, the central gulf is gaining heat and losing fresh water during the whole year; this implies net heat and salinity fluxes into the open ocean, through the gulf's mouth. Temperature and salinity vertical gradients at the surface are well correlated with atmospheric forcing, through tur- bulent diffusion of heat and salt. Horizontal proc- esses (advection and diffusion) are as important as, or more important than, vertical diffusion for both heat and salt balances in the upper layers. Vorticity, the across-gulf derivative of the velocity field, does not show a seasonal cycle. Oceanologia, CICESE, Mexico.

A50. General hydrography (distribution of common oceanic properties)

90:1408 Nishiyama, Katsunobu, 1988. The difference of

oceanographical structure between the Pacific Ocean and the Atlantic Ocean. Umi to Sora, 64(1):43-48.

The difference in oceanographical structure between the Atlantic and Pacific oceans is considered with the aid of The Ocean's charts and the GEOSECS atlas. Temperature and salinity differences in the upper layer, and differences in density structure dependence on temperature and salinity in the lower layer are noted, and estimates of evaporation and precipitation for both oceans are compared. Kobe Mar. Observ., Kobe, Japan. (emm)

A80. Circulation

90:1409 Askari, Farid, L.J. Pietrafesa and G.S. Janowitz,

1989. Steady, three-dimensional circulation on a cuspate continental sheff. Continent. Shelf Res, 9(6):497-526.

OLR (I 990) 37 (3) A. Physical Oceanography 215

A 3-D diagnostic model is constructed to investigate the steady circulation on a cuspate continental shell ~, including coastline curvature and variable bottom topography. The model is forced by alongshore wind stress, offshore wind stress, wind stress curl, wind stress divergence, and the spatial variations of the density field. The effects of nonuniform wind forcing introduced by the coastal curvature and those purely due to the effects of the wind stress curl and divergence with no flux normal to the coast are compared and discussed. Dept. of Mar., Earth and Atmos. Sci., North Carolina State Univ., Raleigh, NC 27695-8208, USA.

90:1410 Foreman, M.G.G. and A.F. Bennett, 1989. On

calculating vorticity balances in primitive equa- tion models. J. phys. Oceanogr. 19(9): 1407-1411.

A note of caution is provided to users of the widely-distributed Cox ocean circulation model. The discrete conservation of vorticity equation associated with the finite difference approximations to the primitive equations on an Arakawa B grid contains a term that approximates flAy2O2u/OxOy. Although this term has no counterpart in the continuous equation, it is consistent with a beta term in which the v velocity is evaluated by a streamfunction difference over 2Ax and must be included when model velocities are used to calculate vorticity balances. Regions within ocean models where the spurious term might be significant are discussed and the relative magnitude of the term with respect to fly is calculated for a simple barotropic model of the North Pacific. A similar spurious term can also arise with a C grid model. Inst. of Ocean Sci., P.O. Box 6000, 9860 West Saanich Rd., Sidney, BC V8L 4B2, Canada.

90:1411 Frankignoul, Claude, Christine Duchene and M.A.

Cane, 1989. A statistical approach to testing equatorial ocean models with observed data. J. phys. Oceanogr, 19(9): 1191-1207.

A model testing procedure based on multivariate statistical analysis has been developed to provide an objective measure of the fit between ocean model simulations and observations. The method is applied to seasonal variations in an ocean model of the tropical Atlantic. A wind-driven linear multimode model with a simple mixed-layer is tested against surface currents estimated from ship drifts. Uncer- tainties in the observations, and in model response create a substantial indeterminacy in the sample, but do not explain the large discrepancies found between observed and modeled seasonal surface currents. Nor are uncertainties in the wind stress bulk

formulation sufficient to account for the differences. Use of the method in model tuning is illustrated by determining the vertical resolution that provides an optimal fit to the observed surface currents. The linear model works best with only one vertical mode, and a mixed-layer depth of 40 m. However, dis- crepancies with observations remain too large for improvement in model performance to be statis- tically significant. Univ. Paris VI, LODYC, 4 Place Jussieu, 75232 Paris Cedex 05, France.

90:1412 Garcia, C.A.E. and I.S. Robinson, 1989. Sea surface

velocities in shallow seas extracted from sequen- tial coastal zone color scanner satellite data. J. geophys. Res~ 94(C9): 12,68 I- 12,691.

Sequential CZCS images of visible wavelength reflectance have been used for computing advective velocities in the eastern English Channel, using the maximum cross-correlation technique. Matched filtering has recently been applied by oceanogra- phers to detect sea surface motion from satellite infrared images. Provided accurate coregistration of images is achieved by matching ground control points, significant Correlation is obtained when the technique is applied to CZCS data, and coherent velocity distributions are obtained for United King- dom shelf waters. Residual circulation patterns for the English Channel are consistent with previous studies and recent observations. Dept. de Fisiea, Fundacao Univ. do Rio Grande, Rio Grande, Brazil.

90:1413 �9 Hukuda, H., R.J. Greatbatchand A.E. Hay, 1989. A

simple three-dimensional model of the circulation off Newfoundland. J. geophys. Res, 94(C9): 12,607-12,618.

The model uses linear dynamics, a vertical eddy viscosity to parameterize the vertical mixing, and a linear parameterization of bottom friction in which the bottom stress is related to the bottom velocity. The model is driven by specifying the sea level along the northern boundary, the inflow corresponding to the inshore and offshore branches of the Labrador Current. We investigate the dependence on the friction parameters of the transport through several sections, as well as the onshore/offshore mass exchange over the southeastern edge of the Grand Banks. The model Labrador Current flowing south- ward along the shelf break leads to an onshelf flux in the upper part of the water column and an offshelf flux in the bottom Ekman layer; caused by the frictional torque, this leads to an along-slope decay of the current amplitude. Dept. of Phys., Memorial Univ. of Newfoundland, St. John's, NF A1B 3X7, Canada.

216 A. Physical Oceanography OLR (I 990) 37 (3)

90:1414 Mt~ller, Peter and Greg Holloway, 1989. The Ocean-

ography Report. Parameterization of small-scale processes. Eos, 70(36):818-820, 830.

Sub-grid scale motions must be parameterized in numerical oceanic circulation models, and this is generally done with diffusion terms. But many questions arise as to the accuracy of these terms and the sensitivity of the models to them. Such questions were discussed at the Fifth 'Aha Huliko'a Hawaiian Winter Workshop by numerical modellers, theore- ticians and small-scale observers. This report out- lines some of the main problems (and conclusions) that were discussed. Dept. of Oceanogr., Univ. of Hawaii, Honolulu, HI 96822, USA. (fcs)

90:1415 Nagata, Yutaka, 1988. Study of the subarctic gyre

system in World Ocean Circulation Experiment OVOCE). Umi to Sora, 64(1):49-62. (In Japa- nese.) Dept. of Geophys., Tokyo Univ., Tokyo, Japan.

90:1416 Ozsoy, E., A. Hecht and U. Onloata, 1989. Circu-

lation and hydrography of the Levantine Basin. Results of POEM coordinated experiments 1985-1986. Prog. Oceanogr~ 22(2):125-170.

Details of the circulation such as the intensity, the multiple scales and the structure of the various vortices and the Central Levantine Basin Current are displayed extensively. A variety of sub-basin, meso- and sub-mesoscale vortices occur with highly asym- metric (baroclinic) vertical structures. Some eddies split into multiple centres with depth, interpreted as indicating possible coalescences. A number of long-lived eddies were persistent in both surveys. Inst. of Mar. Sci., Middle East Tech. Univ., PK 28, Erdemli, Icel, 33731, Turkey.

90:1417 Pedlosky, J. and R.M. Samelson, 1989. Wind forcing

and the zonal structure of the equatorial under- current. J. phys. Oceanogr, 19(9): 1244-1254.

A nonlinear inviscid model of the equatorial under- current is coupled to a wind-driven surface layer. Wind stress drives a poleward Ekman flow, causing equatorial divergence of surface layer transport. This divergence is balanced by upwelling of fluid supplied by zonal convergence of the undercurrent. In this manner, the imposed wind stress controls the zonal structure of the undercurrent transport. Solutions are presented for two profiles of zonal wind stress. For westward wind stress increasing linearly westward,

eastward transport increases nearly linearly west- ward. For westward wind stress with a midbasin maximum, eastward transport has a maximum just west of the basin middle, and there is recirculation along the Equator. Solutions are also presented for uncoupled models with several layers and with a deep constant potential vorticity layer. WHOI, Woods Hole, MA 02543, USA.

90:1418 Perigaud, Claire and Pascale Delecluse, 1989. Sim-

ulations of dynamic topography in the north- western Indian Ocean with input of Seasat altimeter and scatterometer data. Ocean-air In- teractions, 1(3):289-309.

Seasat altimeter data are used to constrain a nonlinear shallow-water model simulation of dy- namic topography during summer in the north- western Indian Ocean. With this constraint it appears possible to predict oceanic variations for the region a month in advance. Various experiments, linear and nonlinear, with varying and differently acquired wind stress fields, are described. Jet Propulsion Lab., MS 300-323, 4800 Oak Grove Dr., Pasadena, CA 91109, USA: (fcs)

90:1419 Roemmich, Dean and Tracy McCallister, 1989.

large scale circulation of the North Pacific Ocean. Prog. Oceanogr, 22(2):171-204.

This study represents an attempt to assimilate modern data gathered by myriad investigators concerning the large-scale circulation and transport of the North Pacific Ocean by requiring the data set as a whole to conform to a consistent basin-scale circulation. From a 'reasonable" guess at a level of known motion based on basin scale tracer data, topographical flow constraints, and direct velocity measurements, a least squares inverse method is applied to obtain a solution which satisfies mass conservation constraints but deviates minimally from the initial field. Mar. Life Res. Group, Scripps Inst. of Oceanogr., La Jolla, CA 92093, USA. (emm)

Ag0. Currents

90:1420 Abramov, V.M. et al., 1988. Dynamic errors of

oceanic current meters with rotor transducers. Oceanology (a translation of Okeanologiia), 28(3):390-392. Leningrad Hydrometeorol. Inst., Leningrad, USSR.

OLR (1990)37 (3) A. Physical Oceanography 21"/

90:1421 Alvarez, L.G., A. Badan-Dangon and A. Valle, 1989.

On coastal currents off Tehuantepec [SW Mex- icol. Estuar. coast. Shelf Sci, 29(1):89-96. CICESE, Apdo. 2732, Ensenada, B.C., Mexico.

90:1422 Bower, A.S. and T. Rossby, 1989. Evidence of

cross-frontal exchange processes in the Gulf Stream based on isopycnal RAFOS float data. J. phys. Oceanogr, 19(9): 1177-1190.

The KAFOS drifters revealed a striking pattern of vertical and cross-stream motion in Gulf Stream meanders. Floats were consistently observed to upwell (downweli) and move onshore (offshore) as they approached anticyclonic (cyclonic) meander crests (troughs). The rms vertical velocity in the center of the stream was observed to be 0.08 cm s -t on the 12~ surface. No mean vertical motion was detected in the main thermocline of the Gulf Stream between 70 ~ and 55~ Using a model of the mean cross-stream thermal structure of the current, rms cross-stream velocities were estimated to be 8 - t0 cm s -t. This meander-induced circulation represents an important mechanism for cross-frontal exchange. When the Gulf Stream is meandering, fluid parcels from the center of the current are brought to the edges and often escape completely. Clark 315A, WHOI, Woods Hole, MA 02543, USA.

90:1423 Brenner, Stephen, 1989. Structure and evolution of

warm core eddies in the eastern Mediterranean Levantine Basin. J. geophys. Rest 94(C9): 12,593-12,602.

A variety of warm core and cold core mesoscale eddies is revealed for both summer and winter seasons. Some appear to retain their identities from summer to winter. In particular, there are two intense anticyclonic eddies, one of which appears to have formed off the coast of Egypt as a meander of the North African current; the other is a rather persistent quasi-stationary feature to the southeast of Cyprus which has been seen near this location for over 3 years. Each eddy had a unique signature in its TS diagram which changed very little over the 6 months covered. Israel Oceanogr. and Limnol. Res., Natl. Inst. of Oceanogr., P.O. Box 8030, Haifa 31080, Israel.

90:1424 Cooper, Cortis and J.D. Thompson, 1989. Hurri-

cane-generated currents on the outer continental shelf. 1. Model formulation and verification. J. geophys. Res, 94(C9): 12,513-12,539.

Emphasis is on the mixed-layer response within a few hours of storm passage; however, some attention is given to the lower layer and shelf wave responses. Model comparisons are presented for three Gulf of Mexico hurricanes using a 0.2 ~ grid. For two of the storms, the model reproduces better than 80% of the observed velocity variance with correlation coeffi- cients of greater than 0.8 for the mixed layer; discrepancies are traced to unresolved local topog- raphy and nonstorm forcing such as warm-core rings. Substantial shelf waves were generated with phase speeds of 4 to 10 m s-~; response is primarily baroclinic even in water as shallow as 200 m. Deviations from a straight-line storm path can significantly alter the response. Coastal Leasing, Inc., 179 Sidney St., Cambridge, MA 02139, USA.

90:1425 Cooper, Cortis and J.D. Thompson, 1989. tlurri-

cane-generated currents on the outer continental shelf. 2. Model sensitivity studies. J. geophys. Res~ 94((;9): 12,540-12,554.

The sensitivity of model response to changes in storm parameters, direction of storm approach, and topography is quantified. Response is measured in terms of the .mixed-layer velocity and depth at sites along the storm track. Results reveal the most important factors are (in decreasing order) wind speed, storm translation speed, direction of storm approach, asymmetry in the wind field, entrainment parameterization, and advection at slower storm translation speeds. Response is largely insensitive to radius of maximum wind, shelf and slope config- uration, bottom friction, atmospheric pressure gra- dients, and further reductions in the model grid size. For a storm approaching cross shelf, the response is primarily baroelinie and only weakly dependent on depth. Coastal Leasing, 127 Sidney St., Cambridge, MA 02139, USA.

90:1426 Cornillon, Peter, Richard Weyer and Glenn Flierl,

1989. Translational velocity of warm core IGuif Stream I rings relative to the slope water. J. phys. Oceanogr, 19(9): 1317-1332.

Five warm core rings east of 72~ were examined during short time intervals using thermal infrared satellite imagery. The observations concentrated on the translational velocity of the rings and the mean velocity of the surrounding slope water. These rings were found to move relative to the surrounding slope water with a mean northward component of 2.8_ 1.7 cm s -t and a mean westward component of 3.2-+2.3 cm s -t. The observations presented here are in disagreement with previous observations of ring displacements which show a general southerly trend,

218 A. Physical Oceanography OLR (1990) 37 (3)

as well as with most theoretical analyses of eddy propagation which show either westward or south- westward velocities. Because the continental shelf constrains rings to move generally in a southwesterly direction it is not surprising that estimates derived over long periods show a southerly trend. Only tings free of such interactions were considered in this study. This resulted in the observation intervals being short (12-36 h) and in a limited number of observations (12), hence in a relatively high uncer- tainty in the estimates. Nevertheless, 8 of the 12 observations showed a northward component. Grad. School of Oceanogr., Univ. of Rhode Island, Nar- ragansett, RI 02881-1197, USA.

90:1427 Cresswell, G.R. et al., 1989. Continental shelf

currents near the Ahrolhos Islands, Western Australia. Aust. J. mar. Freshwat. Res~ 40(2): 113-128. Div. of Oceanogr., CSIRO Mar. Lab., G.P.O. Box 1538, Hobart, Tas. 7001, Australia.

90:1428 Detain, Yu.L. and D.I. Trukhchev, 1988. Numerical

experiments on hydrodynamic adjustment of ocean currents. Oceanology (a translation of Okeanologiia), 28(3):285-289.

A model of the hydrodynamic adjustment of ocean currents and results of numerical experiments with it are presented. Results obtained by first- and sec- ond-order approximations are compared. The results obtained for the field adjustment stage and for the steady-state solution differ significantly. Dept. of Computational Math., Aead. of Sci., Moscow, USSR.

90:1429 Essen, H.-H., K.-W. Gurgel and F. Schirmer, 1988.

Horizontal and temporal variability of surface currents in the 'Lfibecker Bucht,' [western Baltic Seal as measured by radar. Dt. hydrogr. Z~ 41(2):57-74.

90:1430 Johnson, E.R., 1989. Boundary currents, free currents

and dissipation in the low-frequency scattering of shelf waves. J. phys. Oceanogr. 19(9): 1291-1300.

The low-frequency scattering of barotropie shelf waves is considered in the limit of small but nonzero dissipation. For a rectilinear shelf an intense oscil- latory boundary layer forms on the incident side of any obstacle, it destroys incident shelf wave energy and turns volume flux to pass smoothly round the obstacle. By confining attention to low frequencies the results of Wilkin and Chapman for scattering at a discontinuity in shelf width are extended to more

general changes in width and shelf profiles. A spreading along-shelf free shear layer is present downstream of a widening shelf. For a narrowing shelf this layer carries fluid from the dissipation layer and for a headland the layer represents an intense free midshelf current. A change in shelf width can scatter energy from an oscillatory geo- strophic current into shelf waves. This corresponds in a flow with a free surface to scattering of Kelvin wave energy into shelf waves. Dept. of Math., Univ. Coll. London, Gower St., London WCIE 6BT, UK.

90:1431 Larouche, Pierre and J.-C. Deguise, 1989. Field

intercomparison of three current meters in an [Arcticl environment free from high frequency motion. Continent. Shelf Res, 9(6):555-568.

The instruments were an Aanderaa RCM4S, an Inter Ocean $4 and an EG&G-Neil Brown SACM. The $4 and the SACM both showed ability to measure very small currents as opposed to the RCM4S, which is limited by a mechanical rotor threshold. Agreement of direction was better be- tween the RCM4S and the SACM than between the RCM4S and the $4. Due to the misalignment of the Aanderaa vane in very weak currents, direction differences between the instruments of either pair can, however, reach 180 ~ The misalignment also shields the Aanderaa rotor, leading to underesti- mation of current speed; the threshold for a good speed reading for the Aanderaa can be put conser- vatively at 5 cm s -I. Above this value, the RCM4S over-responded compared to both the $4 and the SACM. The RCM4S, when not influenced by wave action, can produce a measure of the energy as good as that of a vector averaging instrument. Inst. Maurice-Lamontagne, Ministere des -Peches et des Oceans, Div. d'Oeeanogr. Phys., C.P. I000, Mont- Joli, PQ G5H 3Z4, Canada.

90:1432 Lentz, S.J. and D.C. Chapman, 1989. Seasonal

differences in the current and temperature vari- ability over the northern California shelf during the Coastal Ocean Dynamics Experiment. J. geophys. Res~ 94(C9): 12,571-12,592.

The Coastal Ocean Dynamics Experiment (CODE) was conducted over the northern California con- tinental shelf to identify and study the dynamical processes which govern the wind-driven circulation over the continental shelf. The focus was on the summer upwelling season, however, to characterize the seasonal differences in this region, sparser measurements were made in fall and winter. The present study has two main objectives: (1) to characterize the current and temperature variability

OLR (1990) 37 (3) A. Physical Oceanography 219

of the fall and winter CODE observations which have not previously been examined, and (2) to compare the fall, winter, and summer observations to determine the seasonal differences in the current and temperature variability. WHOI, Woods Hole, MA 02543, USA.

90:1433 Lozier, M.S. and S.C. Riser, 1989. Potential vorticity

dynamics of ,boundary currents in a quasi- geostrophlc ocean. J. phys. Oceanogr~ 19(9): 1373-1396.

Boundary layer potential vorticity dynamics for a quasi-geostrophic, eddy-resolving general circulation ocean model are studied using both Lagrangian and Eulerian analyses. Active western boundary layers are found not only in the upper wind-driven layer but also in lower layers. At the western wall dissipative and inertial boundary regimes are con- trolled by the time-mean dynamics except for the deepest layer where eddy fluxes drive the mean flow across mean potential vorticity contours. Boundary layers formed at the southern wall in this model are dynamically distinct; they are controlled solely by the eddy flux of potential vorticity, found in this region. Basin-integrated vorticity balances reveal a strong contribution to the vorticity cycle by lateral boundaries with such input overshadowed by vor- ticity exchange across the midbasin gyre boundary in the surface layer. School of Oceanogr. WB-10, Univ. of Washington, Seattle, WA 98195, USA.

90:1434 Lutjeharms, J.R.E., R. Catzel and H.R. Valentine,

1989. Eddies and other boundary phenomena of the Agulhas Current. Continent. Shelf Res., 9(7):597-616.

A descriptive study of shear-edge features of the Agulhas Current based on ten years of satellite imagery and two research cruises is presented. The mean location of the landward boundary of the current becomes more diffuse downstream, and its modal location relative to the 200 m isobath depends on distance downstream. Amplitudes of current meanders, plumes and eddies all grow downstream, and the penetration of warm water onto the Agulhas Bank increases downstream. All these border fea- tures may extend throughout the water column of the shelf. Natl. Res. Inst. for Oceanol., CSIR, P.O. Box 320, Stellenbosch 7600, South Africa.

90:1435 Prinsenberg, S.J. and E.B. Bennett, 1989. Vertical

variations of tidal currents in shallow land fast ice-covered regions. J. phys. Oceanogr, 19(9): 1268-1278.

Arctic tidal currents with periods near the local inertial period are strongest and rotate clockwise at mid-depth, and decrease in amplitude toward the bottom and the ice-cover, experiencing a change in direction of rotation of the current vector to counterclockwise near the boundaries. Such obser- vations are explained by analytical solutions to a simple model in which the current vector of fre- quency is the sum of oppositely rotating compo- nents. The frictional boundary layer thickness is markedly different for the two components. In the case of semidiurnal tidal components at high latitudes, the positive rotary component has a thin boundary layer and dominates near the boundaries, whereas the negative rotary component with a much larger boundary layer dominates at mid-depth. Ocean Circulation Div., Phys. and Chem. Sci., Bedford Inst. of Oceanogr., P.O. Box 1006, Dart- mouth, NS B2Y 4A2, Canada.

90:1436 Reed, R.K. and J.D. Schumacher, 1989. Some

mesoscale features of flow in Shelikof Strait, Alaska. J. geophys. Res, 94(C9):12,603-12,606.

Moored current obsercations were obtained from a small region of Shelikof Strait during 1986-1987. Results frorfi two sites < 4 km apart revealed very similar energy spectra and highly correlated along- stream component flow. At separations >11 km, however, correlations were quite weak. A new feature, intense 13-day spectral peaks of narrow horizontal and vertical scale, was also revealed. The feature appears to be a baroclinic, residual flow linked to tidal currents. PMEL, NOAA, 7600 Sand Point Way NE, Seattle, WA 98115, USA.

90:1437 Rienecker, M.M. and C.N.K. Mooers, 1989. Meso-

scale eddies, jels, and fronts off Point Arena, California, July 1986. J. geophys. Re.s, 94(C9): 12,555-12,569.

A broad (40 kin) cold filament observed off Point Arena in AVHRR images at the end of June 1986 evolved into a narrow (10-20 km) cold filament embedded in a large-scale (200 km alongshore) cool anomaly by mid-July. The cool anomaly was part of a much larger-scale anomaly, stretching from north of Cape Mendocino to south of San Francisco, in which several cold filaments were embedded. The filament off Point Arena, surveyed by ship from July 7 to 19, 1986, extended offshore around the edge of a cyclonic center. In this paper the horizontal and vertical and mesoscale physical structure of the filament and offshore jet are described from the in-situ data; sman-scale intrusive features are shown in vertical sections of temperature and salinity from

220 .A. Physical Oceanography OLR (1990) 37 (3)

CTD data. Lab. for Oceans, NASA Goddard Space Flight Ctr., Code 671, Greenbelt, MD 20771, USA.

90:1438 Schott, Friedrich, J.C. Swallow and Michele Fieux,

1989. Deep currents underneath the equatorial Somali Current. Deep-Sea Res, 36(8A):1191- 1199.

Moored current measurements were carried out for 2 years underneath the Somali Current on the Equa- tor. The mean currents at 1000, 1500, 2000 and 3000 m are basically indistinguishable from zero. At the 3000 m level there is, however, an apparent strong seasonal current parallel to the boundary approx- imately in phase with the near-surface monsoon- driven regime. Seasonal means are 10.3_+ 1.8 cm s -t northeastward June to September and 6.6_+2.7 cm s -t southwestward November to February; at 2000 m no seasonal cycle is detected. Properties of the deep water of the western Somali Basin are discussed in the context of a seaonally reversing deep boundary current. Inst. fur Meereskunde an der Univ. Kiel, Dusternbrooker Weg 20, D-2300 Kiel 1, FRG.

AIIO. Water masses and fronts

90:1439 Fedorov, K.N. and S.L. Meshchanov, 1988. Struc-

ture and propagation of Red Sea waters in the Gulf of Aden. Oceanology (a translation of Okeanologiia), 28(3):279-284.

In the western part of the gulf Red Sea waters propagate in three branches, each of which is transformed in two stages. In the first stage, the transformation results from vigorous mixing with surrounding waters, and in the second it is produced by double diffusion. The structure of the Red Sea waters is discontinuous and their propagation is nowhere strictly isopycnic. Shirshov Inst. of Oceanol., Acad. of Sci., Moscow, USSR.

90:1440 Ishikawa, Koichi, 1988. The Oyashlo water system in

the sea of south Hokkaldo. Umi to Sofa, 64(1):9- 18. (In Japanese, English abstract.) Hakodate Mar. Observ., Hakodate, Japan.

90:1441 Sekine, Yoshihiko, 1988. On the anomalous south-

ward intrusion of the Oyashlo east of Japan. Umi to Sora, 64(1):19-30. (In Japanese, English abstract.) Inst. of Geosci. and Astron., Natl. Defense Acad., Yokosuka, Japan.

90:1442 Yoshida, Takashi, 1988. Two origins of the Oyashlo

�9 water and those distributions in the Oyashio area. Umi to Sora, 64(1):1-8. (In Japanese, English abstract.) Hakodate Mar. Observ., Hakodate, Japan.

A150. Tides and sea level

90:1443 Godin, Gabriel, 1989. On 'radiational' tides and their

interpretation as frictional effects. Continent. Shelf Res, 9(7):589-596.

When the observed sea levels are fitted linearly with the tidal potential, using cross-spectral methods, an apparent discontinuity in the response of neigh- bouring harmonics, like S 2 and K2, becomes no- ticeable. The hypothesis of radiational tides would reproduce this discontinuity by introducing an additional input. However, closer scrutiny shows this hypothesis to be untenable: it would require a diffuse and irregular source of energy, the radiation at the water surface, to induce oscillations of a fixed frequency, of constant amplitude and phase lag. A more plausible 'cause for the discontinuity in re- sponse is quadratic friction which creates a linkage between the spectral elements of the observed water levels. Consequently the spectra of water levels, whenever nonlinear effects are present, will exhibit unusual features such as discontinuities in amplitude and phase, line splitting, and other irregularities. 2936 Aries News, Mississauga, ON L5N 2N2, Canada.

90:1444 Lie, H.-J., 1989. Tidal fronts in the southeastern

Hwanghae (Yellow Sea). Continent. Shelf Res, 9(6):527-546.

A numerical model for the Simpson-Hunter crite- rion predicts the occurrence of strong tidal mixing in four regions of the Hwanghae: northwestern, mid- western, and southwestern regions of Korea, and the mid-east coast of China. In support of the model result NOAA infra-red images taken in summer also give a clear evidence of the existence of three mixing regions west of Korea. Seasonal change of vertical stratification in the southeastern Hwanghae is described using CTD data collected during 1984- 1986. Frontal fine structure in the two small areas of Chindo and Huksando inside the southwestern mixing zone is discussed by analysing CTD data obtained during the summer of 1985. Phys. Oceanogr. Lab., KORDI, P.O. Box 29, Ansan, Seoul, 425-600, Korea.

OLR (1990) 37 (3) A. Physical Oceanography 221

90:1445 Westerink, J.J., K.D. Stolzenbach and J.J. Connor,

1989. General spectral computations of the nonlinear shallow water tidal interactions within the Bight of Abaco [Bahamas]. J.phys. Oceanogr~ 19(9):1348-1371.

An iterative frequency-time domain finite element tidal circulation model is applied to study the nonlinear interactions that occur between the var- ious astronomical, overtide and compound-tide constituents. The nonlinear origin of the significant shallow-water constituents is determined by sup- pressing the various nonlinear terms in the shallow- water equations. Furthermore, the extent to which nonlinear constituents interact with and affect each other is studied in detail by suppressing the inter- action of selected tides within the framework of the iterative frequency-time domain formulation. It is found that secondary nonlinear interactions between the astronomical tides and the shallow water tides themselves can significantly affect overtides, com- pound tides and even astronomical tides. Ocean Engng Progr., Civil Engng Dept., Texas A&M Univ., College Station, TX 77843, USA.

AI60. Waves, oscillations 90:1446

Abe, Katsuyuki, 1989. Estimate of tsunami heights from magnitudes of earthquake and tsunami. Bull. Earthq. Res. Inst, Univ. Tokyo, 64(I):51-69. (In Japanese, English abstract.) Earthquake Res. Inst., Univ. of Tokyo, Japan.

90:1447 Beloshapkov, A.V., 1988. Description of longshore

wave flow in the presence of irregular waves and an arbitrary underwater slope profile. Oceanology (a translation of Okeanologiia), 28(3):363-365.

The transverse velocity distributions of longshore energy flow are derived. With a mixing parameter P of 0.04--0.4, representing typical conditions of the shallow-water areas of sandy beaches, the transverse flow velocity distribution is little dependent on P. When there is an underwater bar, the velocity distribution plot has two maxima, one on the seaward slope of the bar and the other in the zone near the water's edge. Soyuzmoreinzhgeologiya, Riga, Latvian SSR, USSR.

90:1448 Buzyna, George, R.L. Pfeffer and Robin Kung,

1989. Kinematic properties of wave amplitude vacillation in a thermally driven rotating fluid. 3".

atmos. Sci, 46(17):2716-2729. Geophys. Fluid Dynamics Inst., Florida State Univ., Tallahas- see, FL 32306-3017, USA.

90:1449 Johnson, E.R., 1989. Connection formulae and

classification of scattering regions for low-fre- quency sheff waves. J. phys. Oceanogr, 19(9): 1301-1310.

The scattering of shelf waves at simultaneous changes in depth, direction and width is considered. In the low-frequency limit the scattering is shown to be determined by the connection of f / H contours. The description 'simple' is introduced for regions in which no incident f / H contour terminates and then restarts. An explicit connection formula is derived for simple regions. Energy is transported without loss across a scattering region if no incident f /H contours terminate there. This subclass of simple regions is described as conservative. Particular examples are given for exponential shelves joined by both simple and nonsimple, conservative and non- conservative scattering regions, and for both inci- dent shelf waves and irrotational flows driven across the region. It is noted that if the irrotational flow determined by a particular shelf geometry is geo- strophic then even at arbitrary frequencies no scattering of energy occurs from the flow or among shelf waves. Dept. of Math., Univ. Coll. London, Gower St., London WC1E 6BT, UK.

90:1450 "Johnson, E.R., 1989. Scattering of shelf waves by

islands. J. phys. Oceanogr~ 19(9): 1311-1316.

The domain exterior to an island in a channel with topography is not simply connected and so the circulation about the island is indeterminate. Rhines shows that, in a rotating flow with a rigid lid, requiring the pressure to be continuous forces the circulation to be constant in time. It is shown here that the constant-circulation continuous-pressure solution also conserves energy and, moreover, the circulation associated with scattering of incident shelf waves is identically zero. The scattering problem is then well posed and a method is given for constructing the scattered field at arbitrary fre- quencies. The problem simplifies greatly in the low frequency limit and an explicit solution for waves scattered by a thin barrier follows by decomposing the motion into propagating modes and a geo- strophic current. Explicit values are given for the round-island flux and the distribution of scattered wave energy for a long, thin island in the center of a channel. Dept. of Math., Univ. Coll. London, Gower St., London WC1E 6BT, UK.

222 A. Physical Oceanography OLR (1990) 37 (3)

90:1451 Koaishi, Tatsuo, 1989. Numerical forecast of storm

surges on real time basis. Oceanogrl Mag., 39(1-2):21-42. Japan Meteorol. Agcy., Tokyo, Japan.

90:1452 Ocampo-Torres, F.J. and I.S. Robinson, 1989.

Wind-directional effects on the hydrodynamic modulation of microwave radar images of ocean waves. Int. J. Remote Sens., 10(8):1339-1355. CICES, Ensenada, Espinoza 843, Ensenada, BC, Mexico.

90:1453 Swart, D.H. and J.B. Crowley, 1989. Approximate

solution for water waves on a sloping bottom. CS1R Res. Rept, S. Afr, 641:ca.50pp.

This paper describes the derivation from first principles of a water wave theory applicable to all relative water depths for non-breaking waves and for mildly sloping beds which in the context of this paper is taken to be slopes less than one in five. The analytical soundness of the theory is calculated and compared with that for well-known wave theories applicable on a horizontal bed. Comparison with experimental data showed that the new theory gives a very good first estimate of the systematic trend in wave characteristics with slopes between 0 and 1 in 10. The mass transport field predicted with the aid of this theory will allow for much more accurate prediction of wave-induced sediment movement in the nearshore region just outside the breaker line. CSIR, P.O. Box 320, Stellenbosch 7600, South Africa.

90:1454 White, W.B., Youhai He and S.E. Pazan, 1989.

Off-equatorial westward propagating Rossby waves in the tropical Pacific during the 1982-83 and 1986-87 ENSO events. J. phys. Oceanogr, 19(9):1397-1406.

Analysis of anomalous vertically averaged temper- atures (TAV) in the tropical Pacific finds the development during the onset phase of ENSO events having dynamically significant similarities both north and south of the Equator. The development of positive TAV anomalies in northern autumn/winter along the tropical maritime western boundary of both hemispheres was associated with wind-driven baroelinic long (Rossby) wave activity which had been transmitting positive TAV anomalies from the eastern and central tropical Pacific into the western tropical Pacific over the previous one-to-two years. There were positive anomalies on the maritime western boundary in both hemispheres during

autumn/winter of the onset phase. Dynamical off-equatorial influence only initiated the ENSO event; 0ff-equatorial influence dominated the first half of the ENSO year, and was replaced during the second half by strictly equatorial influences related to the development of anomalous westerly winds on the Equator in the western equatorial Pacific. Pazan: Scripps Inst. of Oceanogr., A-303, La Jolla, CA 92093, USA.

A180. In ternal waves and tides

90:1455 Winters, K.B. and E.A. D'Asaro, 1989. Two-dimen-

sional instability of finite amplitude internal gravity wave packets near a critical level. J. geophys. Res, 94(C9): 12,709-12,719.

A high-resolution 2-D numerical model is used to simulate the propagation of finite amplitude internal wave packets into a mean shear flow that varies slowly in space. For moderate packet amplitudes the interaction is well described by weakly nonlinear asymptotic theory. At higher amplitude, however, a region develops near the critical level in which the wave packet becomes unstable, and convectively unstable density gradients persist for many buoy- ancy periods. The eventual rapid transition is triggered by an instability driven by the intensified wave shear. This illustrates that unstable stratifi- cation does not necessarily lead to convective instability in two dimensions. Appl. Phys. Lab., Univ. of Washington, 1013 N.E. 40th St., Seattle, WA 98105-6698, USA.

A210. Ice

90:1456 Andreas, E.L., 1989. A year of Bowen ratios over the

frozen Beaufort Sea. J. geophys. Res, 94(C9): 12,721-12,724.

A year of 6-hourly measurements of sensible (Hj) and latent (Ht) heat fluxes over multiyear ice in the Beaufort Sea was used to compute the Bowen ratio (Bo = H,/Ht..) for each set of observations; histo- grams of Bo values were plotted for the four seasons. In every season except summer the Bowen ratio is as likely to be negative as positive; thus the histograms are generally bimodal. In summer, when moisture exchange is most rapid, the peaks in the histogram are near Bowen ratios of 1 and - 1 ; in winter, when the rate of moisture exchange is smallest, the peaks are at Bo ~ 20 and Bo ~ -20. Spring and autumn are transition seasons with a broader range of values.

oLR (I 990) 37 (3) A. Physical Oceanography 223

U.S. Army Cold Regions Res. and Engng Lab., 72 Lyme Rd., Hanover, NH 03755, USA.

90:1457 Hobson, George (Canadian Ice Island scientific

party), 1989. Ice island field station: new features of Canadian Polar Margin. Eos, 70(37):833, 838-839.

perennial sea ice 5-7 m thick prevents access to the Arctic Ocean by ship and has restricted research opportunities to the few camps located on the rare but relatively stable thick tabular ice islands calved from the ice shelves of Ellesmere Island. A newly calved (1983) island is now the site of a camp run by Canada's Polar Continental Shelf Project, and has provided the first opportunities to study in detail an area known as the Canadian Polar Margin. Physical, geological and biological results from the project are overviewed. Polar Continental Shelf Project, Geol. Survey of Canada, Ottawa, ON, Canada. (fcs)

90:1458 Kano, Yuji, Kiyotomi Sato and Shoumei Shirato,

1989. Statistical study on sea ice in the Okhotsk Sea observed by GMS for 10 years. Oceanogrl Mag, 39(1-2):43-58.

Sea ice charts compiled by the GMS over a ten-year period (1977-87) in the Okhotsk Sea are used as the basis for a gridwise statistical analysis. The proba- bility of sea ice existence and mean concentration when sea ice exists, as well as mean maximum and minimum sea ice extent are calculated at 5-day intervals. Annual and subannual variations in sea ice extent are also determined and discussed. Japan Meteorol. Agcy, Tokyo, Japan. (emm)

90:1459 Martin, Seelye and D.J. Cavalieri, 1989. Contri-

butions of the Siberian sheff polynyas to the Arctic Ocean Intermediate and Deep Water. 3.. geophys. Res, 94(C9): 12,725-12,738.

The polynyas which occur north of Svalbard, around Franz Josef Land, along the west coast and north end of Novaya Zemlya, and to the east of Severnaya Zemlya and the Taymyr Peninsula are the primary oceanographic contributors. For the region north of Svalbard, historically known as Whalers Bay, heat loss is sufficient to provide the observed cooling of the Wes~t Spitsbergen Current. For the other polyn- yas the heat loss is used to compute the ice production rates and the oceanic salt flux. We then use the historic oceanographic salinities with the salt fluxes to estimate the contribution of each polynya to the Arctic Ocean water masses. Our results imply

that there is insufficient water produced in the shelf polynyas to perform all of the roles that have been historically assigned to it. School of Oceanogr., Univ. of Washington, Seattle, WA 98195, USA.

90:1460 Steele, Michael, J.H. Morison and Norbert Unter-

steiner, 1989. The partition of air-ice--ocean momentum exchange as a function of ice con- centratlon, floe size, and draft. J. geophys. Res, 94(C9): 12,739-12,750.

A coupled sea ice-ocean model includes two terms that have previously been neglected, oceanic form drag and wave radiation pressure, both of which are lateral forces that act on the sides of floes. The former is generally decelerative, while the latter is accelerative. The model accepts as input variables average ice draft, areal concentration, and floe diameter. Form drag can be greater than or of the same order as skin friction drag for small, thick floes at low concentrations except when the effect of wakes between floes reduces the local form drag. The higher net drag that generally exists at low concentrations implies lower ice floe speeds. Wave radiation pressure is negligible in all cases, although this is sensitive to choice of fetch. Ocean drag is often parameterized in numerical models of sea ice as a skin friction term alone, with a constant drag coefficient between ice and (prescribed) geostrophic current velocities. Results from the present model are plotted in terms of such a drag coefficient, which is a function of concentration, floe size, and draft. Polar Sci. Ctr., Appl. Phys. Lab., Univ. of Wash- ington, Seattle, WA 98195, USA.

90:1461 Tison, J.-L. and J. Haren, 1989. Isotopic, chemical

and crystallographic characieristics of first-year sea ice from Breid Bay (Princess Ragnhiid Coast-Antarctica). Antarct. Sci~ 1(3):261-268.

The core consists mainly of frazil ice (77%); the remainder of the core consists of congelation ice. The typical substructure of ice plates/brine lamellae occurs only at the bottom oi the core. Otherwise fine-grained congelation ice is sandwiched between layers of frazil. Thermodynamics satisfactorily ex- plains the isotopic, chemical and textural charac- teristics of the core. It is proposed that the topmost part of the core consists of frazil ice produced by wind- and wave-induced turbulence. Once a con- solidated ice cover is provided, the growth proceeds at a slower rate, through congelation ice formation and frazil ice production, initiated by thermohaline convection processes in the water column. Fac. des Sci., Univ. Libre de Bruxelles, 50 av. F. Roosevelt, 1050 Bruxelles, Belgium.

224 A. Physical Oceanography OLR (1990) 37 (3)

A240. Optical properties 90:1462

Otto, K.-R. and Bodo Furch, 1989. Measuring of underwater light-fields (PAR) with spheric quan- tum sensors. A method to approximate the real values. Arch. Hydrobiol, 116(2):245-252.

The possibilities of characterization of underwater light-fields with spheric and cosine-corrected sensors are presented by means of theoretically designed fields. In relative terms the real values are compared with the corresponding readouts of spheric sensors in normal and upside-down position. A calculation method to compensate the angular sensitivity error of spheric sensors to approximate the real values of underwater light-fields is suggested, and illustrated with application examples on field-data of three water bodies of different biogeochemical properties. Botanisches Inst. der Univ. Kiel, Olshausenstr. 40-60, D-2300 Kiel 1, FRG.

A260. Acoustics

90:1463 Artel'nyi, V.V., I.N. Didenkulov and M.A. Raevskii,

1988. Low-frequencynoise field in an ocean with a rough surface. Soy. Phys. Acoust. (a translation of Akust. Zh.), 34(6):559-562. Inst. of Appl. Phys., Aead. of Sci., Moscow, USSR.

90:1464 Belousov, A.V. and Yu.P. Lysanov, 1988. Angular

structure of the scattered sound field during guided-wave transmission in the ocean with mild surface roughness. Soy. Phys. Acoust. (a trans- lation of Akust. Zh.), 34(6):63%640. N.N. An- dreev Acoust. Inst., Acad. of Sci., Moscow, USSR.

90:1465 Carrion, P.M. and D.J. Foster, 1989. Analysis of

wave motion in even- and odd-dimensional acous- tic media using Radon transform. J. acoust. Soc. A m , 86(3):1093-1096. UFBA, IGEO, PPPG, Campus Univ., Federacao, 40210 Salvador- Bahia, Brazil.

90:1466 Collins, M.D., 1989. Applications and time-domaln

solution of hlgher-order parabolic equations in underwater acoustics. J. acoust. Soc. A m , 86(3): 1097-1102.

A higher-order parabolic equation and the corre- sponding higher-order time-domain parabolic equa- tion are derived from a Pad6 series and solved

numerically. These models provide accurate solu- tions for problems involving very-wide-angle prop- agation; propagation in domains in which sound- speed variations are large; and propagation out to very long ranges. The possibility of modeling elastic wave propagation with a similar approach is con- sidered. Naval Res. Lab., Washington, DC 20375, USA.

90:1467 Gavrilov, A.N., 1988. Correlation of normal modes in

a near-surface channel. Soy. Phys. Acoust. (a translation of Akust. Zh.), 34(6):579-582. N.N. Andreev Acoustics Inst., Acad. of Sci, Moscow, USSR.

90:1468 Goland, V.I., 1988. Statistical characteristics of

normal modes of a sound field in a randomly inhomogencous ocean. Soy. Phys. Acoust. (a translation of Akust. Zh.), 34(6):585-586. Pacific Ocean Oceanogr. Inst., Far-Eastern Sci. Union, Acad. of Sci, USSR.

90:1469 Hall, M.V., 1989. A comprehensive model of wind-

generated bubbles in the ocean and predictions of the effects on sound propagation at frequencies up to 40 kHz. J. acoust. Soc. A m , 86(3):1103-1117. Defence Sci. and Tech. Organisation, Maritime Syst. Div., P.O. Box 706, Darlinghurst, NSW 2010, Australia.

90:1470 Krolik, Jeffrey and David Swingler, 1989. Multiple

broad-band source location using steered covar- iance matrices. IEEE Trans. Acoust. Speech Signal Process, 37(10): 1481-1494. Dept. of Elect. and Computer Engng, Concordia Univ., Mon- treal, PQ H3G IMS, Canada.

90:1~71 Medwin, Herman and M.M. Beaky, 1989. Bubble

sources of the Knudsen sea noise spectra. J. acoust. Soc. A m , 86(3):1124-1130. Phys. Dept., Naval Postgrad. School., Monterey, CA 93943, USA.

90:1472 Mitchell, S.K. and F.W. Machell, 1989. Observations

of low-frequency acoustic interaction with the o c e a n surface. J. acoust. Soc. A m , 86(3):1118- 1123. Appl. Res. Lab., Univ. of Texas, Austin, TX 78713-8029, USA.

OLR (1990) 37 (3) A. Physical Oceanography 225

90:1473 Tollman, P.A. and P.N. Denbigh, 1989. Sonar

beamforming based upon monaural localization techniques. J. aeoust. Soc. Am, 86(3): 1131-1135. 136 Chelmsford Rd., Glenwood, Durban 4001, South Africa.

90:1474 Yefimov, A.V., A.N. Ivakin and Yu.P. Lysanov,

1988. A geoacoustle model of sound scattering by the ocean bottom based on deep sea drilling data. Oceanology (a translation of Okeanologiia), 28(3):290-293.

The acoustic characteristics of bottom sediments as indicated by deep drilling data in several areas of the Pacific Ocean are analyzed and empirical equations for I-D fluctuation spectra of the porosity and relative density at wave numbers from 0.2 to I00 m -t are derived. The values of the sound scattering coefficient calculated with these figures are com- pared with measurements; agreement is good in the case of anisotropic inhomogeneities. Andreyev Inst. of Acoustics, Acad. of Sci., Moscow, USSR.

90:1475 Zavadskii, V.Yu. and Yu.S. Kryukov, 1988. Finite-

difference calculation of sound fields in an irregular waveguide modeling a continental shelf. Soy. Phys. Acoust. (a translation of Akust. Zh.), 34(6):605-608. N.N. Andreev Acoust. Inst., Acad. of Sci., Moscow, USSR.

A290. Physical processes, properties (dif- fusion, turbulence , etc.)

90:1476 Bormans, Myriam and Chris Garrett, 1989. A simple

criterion for gyre formation by the surface outflow from a strait, with application to the Alboran Sea. J. geophys. Res, 94(C9): 12,637-12,644.

A survey of relevant studies suggests that the surface outflow from a strait generally forms a gyre in the adjacent sea if the exit comer is sharp. The gyre grows from an initial 'separation bubble' of radius u/f where u is the current speed and f the Coriolis frequency. The criterion for the maintenance of a coastal jet along a curved coast, instead of sepa- ration and gyre formation, seems to be such that the Coriolis force can hold the current to the coast. Applied to the flow through the Strait of Gibraltar into the Alboran Sea, results suggest that a gyre should always form as the exit comer is sharp. We suggest, though, that the relevant curvature is that where the interface between the two layers intersects

the seafloor rather than where the sea surface meets the coast. Res. School of Earth Sci., Australian Natl. Univ., GPO Box 4, Canberra ACT 2601, Australia.

90:1477 Davey, M.K. and P.D. Killworth, 1989. Flows

produced by discrete sources of buoyancy. J. phys. Oceanogr, 19(9): 1279-1290.

The response of an ocean with a single active dynamical layer to localized buoyancy forcing on a beta-plane is considered. When forcing is very weak, the response is linear, and consists of a quasi-steady ' tube' of fluid stretching westward from the forcing region, with a front advancing at the long Rossby wave speed, and some transient structure in the vicinity of the forcing. When the amplitude of forcing is increased, potential vorticity contours are sufficiently deformed to permit instability both in the forced region and to its west. The response becomes a series of shed eddies, each propagating westward. The time scale to generate an eddy is proportional to the time taken for a long Rossby wave to propagate across the forced region. Further increase in forcing amplitude yields a completely unsteady response. Ho0ke Inst. for Atmos. Res., Clarendon Lab., Parks Rd., Oxford OXI 3PU, UK.

90:1478 Eidsvik, K.J. and B~trd Brors, 1989. Self-accelerated

turbidity current prediction based upon (k--~) turbulence. Continent. Shelf Res, 9(7):617-627.

One-equation and (k-f) turbulence models with Boussinesq viscosity and algebraic stress closures are applied to predict the vertical structure of turbidity currents. Many features of such a flow are associated with weak scientific basis. A 'simple' one is the turbulence near a stably stratified mean velocity maximum. Only when the density flux term is significantly smaller than the turbulent dissipation is a non-reasonable kinetic energy minimum avoided. However, even with fundamental uncertainties, some aspects of model predictions appear to be plausible and realistic. Norwegian Hydrotech. Lab., N-7034 Trondheim, Norway.

90:1479 Klein, tlolger, 1988. A note on momentum transfer in

the bottom mixed layer of the West European Basin. Dt. hydrogr. Z~ 41(2):45-56.

About 20 benthic storms, originated by deep reach- ing eddies, have been observed. These eddies influence the dispersion of tracers in the near- bottom layers significantly, e.g., due to deformation by shear. This paper is an attempt to estimate the eddy viscosity tensor in the bottom mixed layer, with

226 A. Physical Oceanography O LR (1990) 37 (3)

respect to how benthic storms and vortices result in changes of momentum transfer within this layer. Results indicate that their influence is mainly restricted to meso-scale processes.

90:1480 Luketina, D.A. and JOrg Imberger, 1989. Turbulence

and entrainment in a buoyant surface plume. J. geophys. Res, 94(C9): 12,619-12,636.

In winter, tidal outflow from the Leschenault Estuary forms a buoyant sheared stratified plume in Koombana Bay (Western Australia) on each out- going tide. Turbulence in the plume and local entrainment into the plume are examined based on field measurements. Coherency measurements be- tween horizontally separated sensors are used to examine the anisotropy of the turbulence. The effects of viscosity and buoyancy on the turbulence are studied using an activity diagram which is also art indicator of the mixing efficiency and total mixing. The Osborne-Cox model is tested and found to be valid in the plume. Ctr. for Water Res., Univ. of Western Australia, Nedlands, WA 6009, Austra- lia.

90:1481 Medwin, Herman and N.D. Breitz, 1989. Ambient

and transient bubble spectral densities in qui- escent seas and under spilling breakers [obtained from both optical and acoustical techniques]. J. geophys. Res, 94(C9): ! 2,751-12,759. Phys. Dept., Naval Postgrad. School., Monterey, CA 93943, USA.

90:1482 Middleton, J.H. and S.E. Humphries, 1989. Ther-

mohaline structure and mixing in the region of Prydz Bay, Antarctica. Deep-Sea Rest 36(8A): 1255-1266.

Mixing processes responsible for Prydz Bay ther- mohaline circulation are similar to those in the Weddell Sea. In particular, Circumpolar Deep Water intrudes over the shelf break, aided by periodic upwelling processes associated with the tides and continental shelf waves, and mixes with the colder Shelf Water associated with the formation of sea ice

over the continental shelf. Mixing is enhanced by shear, and the resultant cold and salty mixture, termed here Prydz Bay Bottom Water, flows west- ward and downslope under the influence of the Coriolis force and Antarctic coastal winds. PBBW is insufficiently dense to reach abyssal depths, and probably interleaves with the Circumpolar Deep Water at intermediate depths..In the summer months, the mixture may be insufficiently dense to flow down the continental slope. School of Math., Univ. of New South Wales, Kensington, NSW 2033, Australia.

90:1483 Soloviev, A.V., N.V. Vershinsky and V.A. Bez-

verchnii, 1989. Corrigenda. Small-scale turbu- lence measurements in the thin surface layer of the ocean. Deep-Sea Res~ 36(8A):1283-1284.

A300. Fluid mechanics

90:1484 Cullen, M.J.P. and R.J. Purser, 1989. Properties of

the Lagrangian semlgeostrophlc equations. J. atmos. Sc'i~ 46(17):2684-2697.

The Lagrangian form of the semigeostrophic equa- tions has been shown to possess discontinuous solutions that have been exploited as a simple model of fronts and other mesoscale flows. In this paper, it is shown that these equations can be integrated

�9 forward in time for arbitrarily long periods without breaking down, to give a 'slow manifold' of solu- tions. In the absence of moisture, orography and surface friction, these solutions conserve energy, despite the appearance of discontinuities. There is a unique solution to the equations with general piecewise smooth data, to which the finite parcel approximation converges; the time integration pro- cedure is well defined, and solutions remain bound- ed for all finite times. Results are extended to non-Boussinesq fluids, free-surface and periodic boundary conditions, and variable Coriolis param- eter. Meteorol. Off., London Rd., Bracknell, Berk- shire, RG12 2SZ, UK.