Physical oceanography

Oceanographic Literature Review (1988) 35

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The citations are those received in the editorial office during the period 1-29 February, 1988. 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

AI0. Apparatus and methods 88:2525 Anderson, J.M. and R.D. Callison, 1987. The general applicability of airborne thermographic surveys to the measurement of sea surface temperatures. Proc. R. Soc. Edinb., 92B(3-4):237-255. The principles of airborne thermography are outlined including a general introduction to instrumentation, imaging and data correction methods, with examples of some methods used. Specific applications of work done on Tay Estuary and English Channel imagery are described to illustrate some results which can be achieved. Carnegie Lab. of Phys., Univ. of Dundee, DD1 4HN, Scotland, UK. 88:2526 Bai, Iindong, 1987. Some results about Hammerstein nonlinear integral operators. J. Shandong Coll. Oceanol., 17(1):168-173. (In Chinese, English abstract.)

The relationship between two hypotheses about the kernel function, and eigenvalue problems associated with the Hammerstein nonlinear integral operator, are discussed. Dept. of Math., Shandong Coll. of Oceanol., Qingdao, People's Republic of China. (fcs)

88:2527 Bennett, A.F. and W.P. Budgell, 1987. Ocean data assimilation and the Kalman filter: spatial regularry. J. phys. Oceanogr., 17(10):1583-1601. Because ocean circulation models are dimensionally infinite, the use of a Kalman filter to assimilate data requires that the issue of convergence be addressed. Using numerical and asymptotic analyses, it is shown that Kalman gains converge only if the wavenumber spectrum of the system noise is suitably colored. Linear ocean models with both continuous and discrete data are discussed in this context. It is concluded that rigorous application of the Kalman filter to linear ocean circulation models is reasonably

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computationaily economical. Coll. of Oceanogr., Oregon State Univ., Corvallis, OR 97331, USA. (emm) 88:2528 Cornillon, Peter, Craig Gilman, Lothar Stramma, Otis Brown, Robert Evans and James Brown, 1987. Processing and analysis of large volumes of satellite-derived thermal infrared data. J. geophys. Res., 92(C12): 12,993-13,002. The practical integration of satellite-derived data into oceanographic studies requires suitable datareduction processes. The scheme presented here for a number of representative studies using TIROS-N series thermal infrared data rests upon two steps: (i) preprocessing can reduce data volume per satellite pass (by ~98% for full resolution data; by ~84% for lower-resolution data) while maintaining the number of passes; (2) compositing of the resultant data (SST fields in the example presented) allows reduction to a scale suitable for analysis. Grad. School of Oceanogr., Univ. of Rhode Island, Narragansett, RI O2882, USA. 88:2529 Miyazaki, Tadakuni, Hiroshi Shimizu and Yoshifumi Yasuoka, 1987. High-speed spectroradiometer for remote sensing. Appl. Opt., 26(22): 4761-4766. A high-speed spectroradiometer designed for spectral reflectance measurement is described which uses a monochromatic grating and a photomultiplier system for light detection and sweeps the 400-850nm wavelength spectral range with the spectral resolution of 2 nm within 1 s. The instrument's portability and speed of operation make it particularly suitable for field work in the area of fast moving surfaces, e.g., water with wave motion. Some applications in laboratory and field experiments and the instrument's use for ground data collection in remote sensing are discussed. Natl. Inst. for Environ. Studies, Yatabe-machi, Tukuba, lbaraki 305, Japan. 88:2530 Piterbarg, L.I. and S.V. Semovskiy, 1985. Statistical evaluation of the Green function for the ocean surface temperature field. Dokl. Earth Sci. Sect. (a translation of Dokl. Akad. Nauk SSSR), 285(6):21-24. Based upon the hypothesis that SST anomalies are randomly generated, the authors propose analyzing large-scale variational response of the SST field to synoptic atmospheric processes. The method relies upon the Green function of the ocean/atmosphere system, which here is computed statistically from

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observed data rather than explicitly. A sample application to SST anomalies in the North Pacific is given. Shirshov Inst. of Oceanol., Acad. of Sci., Moscow, USSR. (emm) 88:2531 Tang, C.L. and J.D. Woods, 1987. Statistics of upper ocean variables measured by depth-cycling towed instruments. Deep-Sea Res., 34(9A):1579-1592. Data collected along inclined sampling tracks contain horizontal as well as vertical variations of measured variables, therefore cannot be treated exactly like vertical profiles in statistical analysis. A general method is developed to estimate measurement errors due to non-vertical sampling; in particular vertical wavenumber spectrum and probability distribution of isopycnal spacing are considered. In an equilibrium internal wave field, nonvertical measurement has a negligible effect on the vertical wavenumber spectrum due to the very small root mean squared slope of isopycnal surfaces relative to the slope of the sampling track, S. The distribution of isopycnal spacing however, is sensitive to S. Deviation from a normal distribution becomes significant if a/S:>0.1, where o~ is the standard deviation of the isopycnal slope. Inclined sampling introduces a sizeable error which should not be ignored in data interpretation. At low latitudes when the wave field is dominated by low modes, the small measurement error in isopycnal spacing can be neglected. Bedford Inst. of Oceanogr., Dartmouth, NS B2Y 4A2, Canada. 88:2532 Zhang, Dexian, 1987. On the algebraic independence of the value of certain gap series in transcendental points. J. Shandong Coll. Oceanol., 17(1): 174-180. (In Chinese, English abstract.) Dept. of Math., Shandong Coll. Oceanol., Qingdao, People's Republic of China.

A40. Area studies, surveys 88:2533 Kumar, P.V.H. and R.R. Rao, 1987. Diurnal scale variability in vertical thermal structure of coastal waters off southwest coast of India during May 1985. Indian J. mar. Sci., 16(2):71-76. Diurnal scale variations observed in the vertical thermal structure at 3 stations on the continental shelf are analysed with short time series data sets. Heating and cooling cycles observed in the surface layer are qualitatively discussed in terms of surface heat exchange processes. Large amplitude variations

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A. PhysicalOceanography

in the thermocline suggest the prominence of internal waves. The vertical eddy diffusivity coefficient at one station was 72 cm-' sec ~. Naval Phys. and Oceanogr. Lab., Cochin 682 004, India. 88:2534 Tomosada, Akira, K.-H. Segawa and Kazunori Kuroda, 1986. Closely-spaced observations across the Kuroshio Front south of the Cape Shionomisaki. Bull. Tokai reg. Fish. Res. Lab., 120:11-26. (In Japanese, English abstract.) Physical parameters across the Kuroshio Front are described in detail in relation to plankton distributions. Divergence and convergence of surface waters is calculated by using the continuity equation and velocities derived from the ship drift. Settling volume of zooplankton is largest at the cyclonic shear zone of the Kuroshio Front, suggesting that this is the convergence zone. Model results suggest that the geostrophic shear of the main current induces the secondary flow causing convergence and divergence along the section.

AS0. General hydrography (distribution of common oceanic properties) 88:2535 Leetmaa, A., D.W. Behringer, A. Huyer, R.L. Smith and J. Toole, 1987. Hydrographic conditions in the eastern Pacific before, during and after the 1982/83 El Nifio. Prog. Oceanogr., 19(1):1-47. At the surface little evidence was found for a major southward flooding of warm, low salinity water from north of the Equator that has been observed during some previous El Nifios. Major changes took place in the subsurface hydrographic structures. The thermostad between 13°C and 16°C, which is a prominent feature of the hydrography in this region, disappeared early in 1983 and reappeared early in 1984. The vertical temperature gradient along the Equator and along the coast, usually quite variable with depth, became much more uniform in early 1983; it regained its normal structure by early 1984. Changes were evident over the whole depth interval sampled (1000 m). During November 1982 evidence was found for symmetric poleward spreading of the equatorial disturbance along the eastern boundary. These observations presented a unique opportunity for observing the ocean response to a major interannual change in the wind forcing. Climate Analysis Center, Natl. Weather Serv., NOAA, Washington, DC 20233, USA.

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88:2536 Thorpe, S.A., 1987. Current and temperature variability on the continental slope. Phil Trans. R. Soc., 323(1574):471-517.

Moored and lowered instruments were used to study the bottom boundary layer and lower portion of the water column on the western slope of Porcupine Bank off Ireland, and to identify processes leading to mixing and diapycnal transfer. General features of the measurements are described. Temperature inversions were frequent in the lower 150 m. Indirect estimates of vertical diffusivity and turbulent dissipation suggest a major role for inversion in contributing to turbulence. Dept. of Oceanogr., The Univ., Southampton SO9 5NH, UK. (fcs)

ASO. Circulation 88:2537 Cessi, Paola, Glenn Ierley and William Young, 1987. A model of the inertial recirculation driven by potential vorticity anomalies. J. phys. Oceanogr., 17(10): 1640-1652. Some essential features of a recirculating inertial gyre can be analyzed with a very simple, analytically tractable model. In wind-driven, eddy-resolving general circulation models the recirculation appears as a strong sub-basin-scale inertial flow with homogeneous potential vorticity. The constant value of potential vorticity decreases with increasing forcing/dissipation ratio while the size and strength of the recirculating gyre increases. In the subtropical gyre the recirculating gyre might be driven by anomalous values of low potential vorticity carried northward by the western boundary current. We have modeled this process using a barotropic model and prescribing the values of potential vorticity at the edge of the gyre. Our model gyre is contained in a rectangular box to simplify the geometry and to isolate processes occurring in the recirculating region. MIT-WHOI Joint Prog. in Phys. Oceanogr., MIT Center for Meteorol. and Phys. Oceanogr., Cambridge, MA 02139, USA. 88:2538 Garfield, Newell III and D.L. Evans, 1987. Shelf water entrainment by Gulf Stream warm-core rings. J. geophys. Res., 92(C12):!3,003-13,012. Satellite imagery has revealed that shelf water export due to streamer entrainment by warm core rings is a frequent occurrence. Estimates of streamer formation frequency south of Georges Bank together with instantaneous streamer transport values yield an

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annual mean shelf water export value of 5700 km~/yr. When combined with other boundary transport values, a net export results for Gulf of Maine transport; this lack of balance suggests a degree of inaccuracy in existing transport measurements. Grad. School of Oceanogr., Univ. of Rhode Island, Kingston, RI 02881, USA. (emm) 88:2539 Griffin, D.A. and J.H. Middleton, 1987. Steady wind-driven flow in long channels or lakes. Continent. Shelf Res., 7(9):987-1000. The steady, wind-driven, barotropic circulation in an infinitely long frictional channel of parabolic depth profile is examined. The results are made applicable to long homogeneous 'narrow' lakes with steady uniform wind-forcing, and a constant wind-stress may be approximated. For 'wider' lakes such as Lake Ontario, the results are less directly applicable but indicate that flow should be diagonally symmetrical. Dept. of Oceanogr., Univ. of British Columbia, Vancouver, BC, Canada. 88:2540 Houry, Sabine, Eric Dombrowsky, Pierre De Mey and J.-F. Minster, 1987. Brunt-V/iis/lili frequency and Rossby radii in the South Atlantic. J. phys. Oceanogr., 17(10):1619-1626. Brunt-V~tis~il~i frequency profiles have been calculated on a 5 ° x 5 ° grid between 30°N and 70°S, 70°W and 70°E, using annual mean temperature and salinity profiles computed by Levitus. These frequency profiles are used in the computation of first and second internal Rossby deformation radii; the external Rossby radius is computed for reference. These results compare very well with those of Emery et al. for the equatorial Atlantic. Very small values of the radii are evidenced in the extreme south. High vertical variability in Brunt-V~tisala frequency profiles is also observed at the center of the subtropical gyre, probably due to the lack of deep data in this region. Groupe de Rech. de Geodesie Spatiale, 31055 Toulouse Cedex, France. 88:2541 Hunter, J.R. and C.J. Hearn, 1987. Lateral and vertical variations in the wind-driven circulation in long, shallow lakes. J. geophys. Res., 92(C12): 13,106-13,114. Solutions are derived for steady state lateral and vertical variations of horizontal velocity using linear viscous and mixing length assumptions. The bathymetry is represented by a depth distribution function which describes the occurrence of different depths over a cross-section of the basin. The relative

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importance of the lateral (depth integrated) and overturning (vertically varying) circulations is dependent mainly on bottom roughness and shape of the depth distribution. For natural bathymetries, lateral circulation is generally dominant and becomes increasingly so as bottom roughness decreases or the depth distribution becomes broader. Natural bathymetries can be characterized, in this context, by a single dimensionless number, related to the moments of the depth distribution. School of Phys. and Geosci., Curtin Univ. of Tech., Bentley 6102, Western Australia. 88:2542 Ikeda, M., 1987. Wind effects on the buoyancy-driven general circulation in a closed basin using a two-level model. J. phys. Oceanogr., 17(10): 17071723. Wind effects on buoyancy-driven circulation in a two-level rectangular basin are studied. Relative importance of the wind-driven circulation to the buoyancy-driven circulation for meridional density transport is dependent on total Sverdrup transport of the wind-driven circulation, but independent of the buoyancy flux intensities: the wind-driven circulation is less important with weaker wind stress and in a smaller zonal-size basin. A variable wind stress is also given, to examine effects of seasonal variabilities in wind. The results are applied to the Baffin Bay/Labrador Sea system. Bedford Inst. of Oceanogr., Dartmouth, NS B2Y 4A2, Canada. 88:2543 Pedlosky, Joseph, 1987. On Parsons' model of the ocean circulation. J. phys. Oceanogr., 17(10): 1571-1582. A model is constructed for the circulation of a combined subtropical and subpolar ocean. The model is similar to that first proposed by Parsons with the important difference that where the isopycnal separating the upper and lower layer outcrops, the Ekman flux is allowed to freely cross the outcrop line instead of being blocked by the isopycnal. It is shown that this completely alters the global circulation pattern. Outcropping of the cold layer still occurs but along the path described by Luyten, Pediosky and Stommel, i.e., without an associated separated 'Gulf Stream' current. The Ekman flux across the outcrop line implies a water mass conversion which can be calculated directly from the wind stress distribution and is of the order of 5 Sverdrups. This water is allowed to return to the cold water domain along the northern rim and forms a novel branch to the classical Stommel-Arons circulation picture. WHOI, Woods Hole, MA 02543, USA.

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A. Physical Oceanography

88:2544 Spaulding, M., T. Isaji, D. Mendelsohn and A.C. Turner, 1987. Numerical simulation of winddriven flow through the Bering Strait. J. phys. Oceanogr., 17(10): 1799-1816.

A 2-D vertically averaged hydrodynamic model is applied to the wind-forced circulation in the Bering and Chukchi seas. A simulation of the steady state flows induced by a 10 ~'sea surface slope between the North Pacific and Arctic oceans gives a northward transport of 1.97 Sv with 67% and 33% of the flow passing through the Anadyr and Shpanberg straits, respectively. The transport and velocities in the straits scale linearly with the imposed slope. A sensitivity study investigating the influence of open boundary-condition specification, model grid size, bottom friction coefficient and wind-forcing representation showed that the wind is the most important parameter. The model, however, normally underpredicts the wind-driven response. Appl. Sci. Assoc., Inc., Narragansett, RI 02882, USA. 88:2545 Stigebrandt, Anders, 1987. A model for the vertical circulation of the Baltic Deep Water. J. phys. Oceanogr., 17(10): 1772-1785.

A horizontally integrated model of high vertical resolution incorporates a seasonal pycnocline and an advection-vertical diffusion model to compute T and S field evolution. An entraining dense bottom current carries the intruding seawater and drives vertical advection. Model depictions are quite similar to observations, indicating a perennial halocline at ~ 6 0 m depth above strongly stratified deeper water. When the model is run with constant volume flow and salinity of the intruding seawater, stratification below the halocline is weak. Results clearly demonstrate that inflow water characteristics profoundly influence the resulting stratification. Dept. of Oceanogr., Univ. of Gothenburg, Sweden.

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velocity and compared with previously obtained values. Inst. fur Meeresk. an der Univ. Kiel, Abt. Theoretische Ozeanogr., Dusternbrooker Weg 20, 2300 Kiel 1, FRG. (emm)

A90. Currents 88:2547 Ahinas, Kristina, T.C. Royer and T.H. George, 1987. Multiple dipole eddies in the Alaska Coastal Current detected with Landsat thematic mapper data. J. geophys. Res., 92(C12):13,041-13,047.

Seventeen dipole eddies were observed near Kayak Island in one single scene of the Landsat thematic mapper on April 22, 1985. Enhancement techniques showed the eddies were evident only in the visible IR bands which can detect distribution of near surface sediments. The eddies had no significant thermal signature. Eddies of this configuration and frequency have never been observed here previously, although oceanographic and meteorological conditions were typical for the time of year. These eddies should be important to the cross-shelf mixing processes in the Alaska Coastal Current and indicate that the flow here can be unstable at certain times of the year. Geophys. Inst., Univ. of Alaska, Fairbanks, AK 99775, USA. 88:2548 Benilov, Ye.S., 1985. Instability of a large-scale zonal current above an uneven bottom. Dokl. Earth Sci. Sect. (a translation of Dokl. Akad. Nauk SSSR), 285(6):206-209.

88:2546 Wenzel, M.K.C., 1986. [The central circulation of the North Atlantic on the basis of climatological hydrographic data.I Ber. Inst. Meeresk. Christian-Albrechts-Univ., 157:109pp. (In German, English abstract.)

This paper extends the results of Charney and Flied concerning the dynamics (in particular the instabilities) of zonal currents above bottom irregularities of 1-D sinusoidal character to uneven bottoms given by random functions of two variables. The problem is presented in a form which allows descriptions of arbitrary wave types above irregular bottoms. Although the physical interpretation used here is inappropriate for the treatment of Rossby waves, the mathematics of the two problems are seen to be largely similar. Shirshov Inst. of Oceanol., Acad. of Sci., Moscow, USSR. (emm)

Circulation in the North Atlantic is inferred from hydrographic data using a version of the beta-spiral method modified so that mass is conserved and boundary conditions fulfilled. The resultant velocity field agrees well with observed mean large-scale circulation patterns, and differs dynamically from results of the beta-spiral method in regions of strong current. Heat and salt fluxes are computed from the

88:2549 Doering, J.C. and A.J. Bowen, 1987. Skewness in the nearshore zone: a comparison of estimates from Marsh-McBirney current maters and co-located pressure s e n s o r s . J. geophys. Res., 92(C12): 13,173-13,183.

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In response to recent doubt concerning the suitability of Marsh-McBirney current meters for surfzone studies and estimates of higher order velocity moments, a comparison was made of skewness estimates obtained from: (1) co-located current meters and (2) co-located current and pressure measurements. The coherence in co-located current measurements indicated by cross-spectral analyses was reflected in the near equality of skewness estimates. The differences observed between current and pressure-derived skewness estimates were consistent with the nonlinear relation between velocity and pressure. Results support the applicability of the Marsh-McBirney current meter, even in the surf zone. Dept. of Oceanogr., Dalhousie Univ., Halifax, NS B3H 4J1, Canada. (emm)

88:2550 Feliks, Y. and S. Itzikowitz, 1987. Movement and geographical distribution of anticyclonic eddies in the eastern Levantine Basin. Deep-Sea Res., 34(9A): 1499-1508. Deep anticyclonic eddies in the eastern Mediterranean Basin consist of warm salty water. They are characterized by a downward decline of 200 m or more of 14-16°C isotherms over a horizontal distance of 50 km. These eddies are strongly nonlinear; their radium is ~ 4 0 km and corresponding geostrophic currents are about 20 cm s ~at 350 m depth. Life-time of the eddies could be several years, and up to three or four could form annually. The eddies probably form along the coasts of Asia Minor and move first southward, then eastward. Israel Inst. for Biol. Res., Dept. of Math., NessZiona 70450, Israel.

88:2551 Kenyon, K.E., 1987. Why a corrugated coast only influences a longshore current within a wave length of the coast. J. oceanogr. Soc. Japan, 43(2): 135-138. It is postulated from a physical model that an inviscid zone of influence, with a thickness calculated to be a constant times the wave length of the wall, occurs when a steady homogeneous fluid flows by a two-dimensional corrugated wall with small slopes. The method used balances pressure differences between extreme points along the wall and between the wall and outer edge of the influence zone. Curvature of the boundary induces crossstream accelerations and pressure gradients, forming an influence zone. The result for influence zone thickness agrees qualitatively with the exponential decay scale of a potential flow solution to a similar problem, suggesting the influence zone may occur in

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some rotational flows also. 4632 North Lane, Del Mar, CA 92014, USA.

88:2552 Leaman, K.D. and R.L. Molinari, 1987. Topographic modification of the Florida Current by Little Bahama and Great Bahama hanks. J. phys. Oceanogr., 17(10): 1724-1736. The ensemble average of all PEGASUS velocity data shows that the effect of the constriction imposed on the mean Florida Current by Little Bahama Bank can be detected up to 30 km into the Straits of Florida. A simple model is proposed to explain how this effect can produce the subsurface maximum of northward flow commonly observed in the eastern straits. PEGASUS and acoustic Doppler data obtained during March 1984 are used to describe the temporal and spatial variability of the flow. Intermittent southward flow can exist in a band 10-15 km wide off Little Bahama Bank; one such event was detected. The PEGASUS data suggest that these events are associated with meandering of the Florida Current. These results may explain earlier observations of small-scale vortices moving southward across the mouth of the Northwest Providence Channel. RSMAS, Univ. of Miami, FL 33149, USA.

88:2553 Legeckis, Richard, 1987. Satellite observations of a western boundary current in the Bay of Bengal. J. geophys. Res., 92(C12):12,974-12,978. Satellite infrared observations during the latter part of February 1985 reveal two bands of warm water that resemble western boundary currents along the east coasts of India and Sri Lanka. A recently formed elliptical warm core eddy, with a major axis of nearly 150 km, appears at long. 90°E and lat. 19°N at the end of the axis of the current. Color infrared images of SSTs are used to illustrate the SST patterns and to estimate their displacements with time. Natl. Environ. Satellite Data Info. Service, NOAA, Washington, DC 20233, USA.

88:2554 Lynn, R.J. and J.J. Simpson, 1987. The California Current system: the seasonal variability of its physical characteristics. J. geophys. Res,, 92(C 12): 12,947-12,966. The amplitude and phasing of seasonal variation in dynamic height and overall standard deviation of dynamic height of the California Current system, determined by harmonic analysis of data from 1950-1978, define three domains: oceanic, coastal, and transition. The transition zone is a broad band, 200-300 km offshore, parallel to the coast, in which

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the seasonal range of dynamic height is a minimum and the standard deviation is a maximum. Recurrent mesoscale eddies and energetic meanders apparently create this zone, which is coincident with the core of flow of the California Current. Seasonal variations in temperature, salinity, o~, and oxygen are related to variations in the California Current, the Inshore Countercurrent, and the California Undercurrent through vertical adjustments in the density field and changes in transport. SWFC, NMFS, P.O. Box 271, La Jolla, CA 92038, USA.

88:2555 Osgood, K.E., J.M. Bane Jr. and W.K. Dewar, 1987. Vertical velocities and dynamical balances in Gulf Stream meanders. J. geophys. Res., 92(C12): 13,029-13,040. Using velocity and temperature data and the nondiffusive heat equation, a time series of vertical velocity was derived from current meter moorings deployed within the cyclonic flank of the Gulf Stream in the South Atlantic Bight (September 1981-April 1982). A mean vertical velocity of-0.013 cm s Eand standard deviation of 0.078 cm s ~ were obtained. Flow along the trailing edge of a Gulf Stream meander and within the leading portion of a cold core frontal eddy had an upward component while that within the trailing portion of the frontal eddy and along the leading edge of a meander had a downward component. Using the horizontal and vertical velocity time series, cross-stream and along stream momentum balances were calculated. Downstream flow was in geostrophic balance; the Coriolis and nonlinear terms contribute equally to determination of the cross-stream flow. Mar. Sci. Prog., Univ. of North Carolina, Chapel Hill, NC 27514, USA. 88:2556 Seaver, George, 1987. Geographic and temporal eddy variability in the western North Atlantic as sensed by satellite: an eddy generation mechanism. J. phys. Oceanogr., 17(10): 1602-1618. This paper has two objectives: to establish the satellite-derived mesoscale SST anomaly as a useful oceanographic measure and to use this to explore an eddy generation mechanism. The distribution in space and time of 65 coherent eddies sensed by satellites in the western North Atlantic (west of 50°W, March 1981 to December 1984) is presented. A region and season of enhanced warm core eddy formation that becomes apparent from the data is discussed, a connection made with seasonal interior wind stress, and an instability and generation mechanism associated with the recirculation is proposed. The shedding of warm core eddies is seen

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as the mechanism by which the Gulf Stream remains compatible with the gyre interior during seasonal wind stress spin-up. Seaver Engng Assoc. Co., Cataumet, M A 02534, USA.

88:2557 Taira, Keisuke, Toshihiko Teramoto and Kensuke Takeuchi, 1987. Centrifugal forces estimated

from trajectories of drifting buoys in winding paths of the Kuroshio. J. oceanogr. Soc. Japan, 43:104-110. Radii and angular velocities in the motions of drifting buoys are estimated by fitting circles to the trajectories of two drifting buoys, one with a drogue at 300 m depth the other at 800 m depth, deployed in the Kuroshio where it flows counter-clockwise around the large cold water mass south of Honshu, and to two drifting buoys with drogues at 300 m placed where the Kuroshio flows clockwise around Oshima Island in Sagami Bay. Centrifugal forces were 7% and 6% as large as Coriolis forces in the Kuroshio around the cold water mass, and -56% and -42% as large as Coriolis forces in the current around Oshima Island. The temperature gradient in the Oshima-West Channel suggested that the pressure gradient there was smaller due to centrifugal force acting against the Coriolis force. Ocean Res. Inst., Univ. of Tokyo, Minamidai, Nakanoku, Tokyo 164, Japan. 88:2558 Van Gastel, K., 1987. Velocity profiles of tidal currents over sand waves. Neth. J. Sea Res., 21(3):159-170. Velocity profiles were measured over a sand wave in the Southern Bight of the North Sea. The height of the sand wave is ~ 8 m, its wavelength 300 m, and trough depth 36 m. The current behaviour in the trough was very similar to that over a flat seabed, except that a van Veen fit during the quasistationary period around maximum tide had a larger power. Exactly on the crest and just downstream of it, the profiles were significantly different; compared with a van Veen fit, the flow was faster in the lowest 8 m and at 4 m beneath the surface: the highest measuring point. Advection was shown to be important in forming these profiles. Royal Netherlands Meteorol. Inst., P.O. Box 201, 3730 AE de Bilt, Netherlands.

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Water masses and fronts

88:2559 Onken, Reiner, 1986. Numerical simulation of the

generation and instability of mesoscale fronts.

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Ber. Inst. Meeresk. Christian-,41brechts-Univ., 156:143pp. (In German, English abstract.) Two numerical models representing the generation and hydrodynamic instability respectively of mesoscale potential vorticity (MPV) fronts in the ocean are presented here. The existence of such fronts is derived from quasi-geostrophic turbulence theory; observational studies and modelling are discussed. Simulations agree well with observation and theory and yield insights into the physics at MPV fronts and their role in oceanic dynamics. Inst. fur Meeresk. an der Univ. Kiel, Abt. Regionale Ozeanogr., Dusternbrooker Weg 20, D-2300 Kid, FRG. (emm) 88:2560 Paidor, Nathan and P.D. Kiilworth, 1987. Instabilities of a two-layer coupled front. Deep-Sea Res., 34(9A): 1525-1539. The linear instability of a two-layer fluid, whose mean state consists of a motionless lower layer and a surface layer confined between two parallel fronts, is considered. An inverted form occurs at many locations in the deep ocean, notably in the Denmark Strait overflow. Because of the vanishing surface layer depth, quasigeostrophy cannot hold, and primitive equations must be used. Two modes of long wave instability are found. The first, valid for intermediate values of the ratio of total fluid depth to surface layer depth, is analogous to a mode found for an isolated front in an otherwise similar geometry. The second mode is the extension to two layers of the mode already discovered for the same geometry but with an infinitely deep lower layer. Numerical extensions of these results show that the former mode would be observed in practice. Results are in excellent agreement with observations. Dept. of Atmos. Sci., The Hebrew Univ., Jerusalem 91904, Israel. 88:2561 Siedler, Gerold, Anni Kuhl and Walter Zenk, 1987. The Madeira Mode Water. J. phys. Oceanogr., 17(10): 1561-1570. Quasi-homogeneous layers in vertical profiles of T and S in the eastern North Atlantic near Madeira indicate a subtropical Mode Water in the eastern basin. Temperature sections show a maximum horizontal extent of at least 500 kin. The frequency distribution analysis of homogeneous layers in a historical XBT dataset shows a Mode Water formation region near and north of Madeira, at increasing depths, and displaced west and southwest during the year after its formation by wintertime convection. It disappears almost completely, due to mixing, before the next winter. Volume estimates

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suggest this Madeira Mode Water accounts for 15-20% of the total Central Water formation in the corresponding density range as obtained from tracer studies in the North Atlantic gyre. Inst. fur Meeresk., Kiel Univ., 2300 Kiel, FRG. 88:2562 Stramma, Lothar, 1984. Water mass spreading in the warm water sphere of the eastern subtropical North Atlantic, Bet. Inst. Meeresk. ChristianAlbrechts-Univ., 125:108pp. (In German, English abstract.) Mean geostrophic transport in the upper 1000 m between 35°W and the African coast is determined from historical hydrographic and recent CTD measurements to be ~ 11 × 10~ m3/sec. Local values for the level of no motion are obtained by using the dynamic method together with the conservation of mass. The general current pattern is described and shown to be consistent with maps of potential vorticity obtained from smoothed density profiles. Inst. fur Meeresk., Abt. Meeresphys., 2300 Kiel 1, Dusternbrooker Weg 20, FRG. (emm)

A120. Convergences, divergences, upwelling 88:2563 Atkinson, L.P. et al., 1987. Observations of upwelling around the lzu Peninsula, Japan: May 1982. J. oceanogr. Soc. Japan, 43(4):89-103. Hydrographic observations between Izu Peninsula and Oshima Island showed upwelling around the tip of the peninsula and possibly also in the lee of Oshima Island. The upwelling introduced water as cold as 18°C with nitrate concentrations of 3/~M to the surface. Temperature/salinity analyses indicated the upwelled water had Kuroshio characteristics. Slightly fresher water was advected out of Sagami Bay in a coastal counter current. Dept. of Oceanogr., Old Dominion Univ., Norfolk, VA 23508, USA. 88:2564 Bula-Meyer, German, 1985. [A new core of coastal upweiling in the Colombian Caribbean, detected in correlation with certain macroalgal species.] Bo/n. Ecotropica, 12:3-26. (In Spanish, English abstract.) The dynamics of a newly discovered coastal upwelling off Cabo de la Aguja are described. Species diversity and biomass of the macroalgal community are highest during the January-April upwelling period; in contrast, phytoplankton productivity is

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highest during rainy seasons (June and SeptemberNovember) when riverine nutrient input is high. The high species richness for macroalgae in this region is attributed to geographic isolation and unique ecological and meteorological conditions. Dept. de Biol., Univ. Tecnol. del Magdalena, Apartado Aereo 890, Santa Marta, Colombia. (gsb)

88:2565 Nurser, A.J.G. and J.A. Johnson, 1987. Secondary upwelling over a smooth shelf break. Continent. Shelf Res., 7(9): 1063-1078. An unsteady model of secondary upwelling over the break at the edge of the continental shelf is described for bottom topography with a smooth but distinct shelf break. Numerical solutions are determined for examples using a simple spin-up wind to illustrate the circulation and a moving pulse of wind to generate continental shelf waves. Dept. of Phys., Imperial Coll., London SW7 2AZ, UK.

88:2566 Petrie, Brian, B.J. Topliss and D.G. Wright. 1987. Coastal upwelling and eddy development off Nova Scotia. J. geophys, Res., 92(CI2): 12,979-12,991. Satellite photos (summer 1984) show a band of cool water developed along the seaward coast during a month-long period of upwelling-favorable winds, and the timing of its appearance, the rate at which it broadened, and the bottom-temperature evolution at representative points along the coast are in good agreement with a two-layer model of wind-driven shelf circulation. After the temperature front moves offshore, wavelike features develop with alongshore wavelengths of 50-75 km and similar maximum cross-shore displacement amplitudes. Associated alongshore propagation speed is at most 0.02 m s ' to the northeast. Length and time scales are consistent with results from linear instability models which allow for potential and kinetic energy release from the mean state by perturbations. Results suggest the wavelike features are primarily due to baroclinic instability of the upwelling-associated base state. Bedford Inst. of Oceanogr., P.O. Box 1006, Dartmouth, NS B2Y 4A2, Canada.

AI50. Tides and sea level 88:2567 Denness, Bruce, 1987. Sea-level modelling: the past and the future. Prog. Oceanogr., 18:41-59. An analytical expression is derived which describes the natural variation of global temperature and related climatic variables over periods from a year to

407

a billion years, and is niiown to match the variation of eustatic sea level over similar periods. An additional greenhouse effect factor is then added and yields a close correlation with observed history over the past century. This provides grounds for confidence in the subsequent deterministic forecast of a sea-level rise of about 0.7 m by 2050 AD. A tentative physical explanation of the natural climate model is given by invoking a variable Universal Gravitational Constant. In parallel, the anthropogenic climate model is underlined by alluding to a population growth mechanism which largely drives it. The interactive nature of the impact of man on sea-level rise and vice versa is stressed. Bur. of Appl. Sci., Wydcombe Manor, Whitwell, Isle of Wight, PO38 2NY, UK.

88:2568 Devoy, R,J.N., 1987. Sea-level applications and management. Prog. Oceanogr., 18:273-286. The International Geological Correlation Programme's Project 61 and other sea level studies have led to a wealth of publications since 1975. The potential for application of the data is wide, and the value of the shoreline data in testing models of Earth crustal behavior and mantle rheology is well established. In biogeography, data may be used to test the feasibility of land bridge development and the consequent movements of plants and animals. The probable continuing rise of sea level, resulting from man-induced environmental changes, scares all concerned with shoreline management, and although ingeneous solutions have been developed, is mankind technically able and prepared to manage a long-term rising sea level? The aims of Project 61 were unattainable, will the results of Project 200 be of greater practical relevance? Dept. of Geogr., Univ. Coll., Cork, Ireland.

88:2569 Diamante, J.M., T.E. Pyle, W.E. Carter and Wolfgang Scherer, 1987. Global change and the measurement of absolute sea-level. Prog.

Oceanogr., 18:1-21. Accurate assessment of 'absolute' sea level responses to climatic change requires the dissociation of land-motion effects from tide/sea level measurements. Recent advances in space-based geodesy (GPS and VLBI techniques) together with a proposed global sea-level network would make such measurements feasible on a 1-2 mm/yr scale. In addition to applications in oceanography and global climatology, measurements of actual land motion will help test models relating mantle viscosity and deglaciation history to present rates of vertical

408

A. Physical Oceanography

crustal motion. Office of Oceanic and Atmos. Res., NOAA, Rockville, MD 20852, USA. (emm) 88:2570 Kagan, B.A. and N.B. Masiova, 1985. A stochastic model of the tidal evolution of the Earth-Moon system in the presence of a cyclic change in the resonance frequency. Dokl. Earth Sci. Sect. (a translation of Dokl. Akad. Nauk SSSR), 285(6): 40-43. Given the dependence of the ocean's resonance properties upon continental drift, and assuming that continental drift is determined by convective processes in the Earth's mantle, it is pointed out that cyclic changes in the associated convective structures would produce cyclic changes in the Earth's characteristic vibration spectrum. The authors have studied the modelled changes in diurnal and semidiurnal characteristic vibrations during continental merger and separation. Presented here is a stochastic model to evaluate the consequences of those changes for the tidal evolution of the Earth-Moon system. Shirshov Inst. of Oceanol., Acad. of Sci., Leningrad, USSR. (emm) 88:2571 Kawabe, Masaki, 1987. Spectral properties of sea level and time scales of Kuroshio path variations. J. oceanogr. Soc. Japan, 43(2):111-123. The large meander of the Kuroshio occurs with a primary period of about 20 years and secondary period of 7 to 8.5 years. During the non-largemeander period, the Kuroshio alternately takes the nearshore and offshore paths with a primary period of 1.6-1.8 years; this variation is composed of l l0-day, around 195-day and annual periods. The l l0-day variation of the Kuroshio path appears to influence coastal sea levels between the Kii Peninsula and the Izu Ridge: the level rises and falls with one-month time lag after the Kuroshio has begun to approach and leave the coast. During the largemeander period, the 70 and l l0-day variations are remarkable in sea levels south of Japan. Sea-level variations are incoherent between the onshore and offshore sides of the Kuroshio, except for seasonal variation. Ocean Res. Inst., Univ. of Tokyo, Minamidai 1-15-1, Nakano-ku, Tokyo 164, Japan. 88:2572 Nakamura, Shigehisa, 1987. A response of wide-open bay in a numerical model. Mar. Geod., 11(4):241250. Using a finite difference method and Tanabe Bay as a specific case, numerical response profiles for water level at crest and trough and current at ebb and

O L R ( 1988) 35 (5)

flood are obtained for the resonant mode. The resonant mode exhibits a node off the bay mouth on the continental shelf, suggesting that a coupled treatment of bay and shelf may be more appropriate. The relevance of this problem to that of tsunamis is stressed. Shirahama Oceanogr. Observ., DPRI, Kyoto Univ., Katada-Hatasaki, Shirahama, Wakayama 649-22, Japan. (emm)

88:2573 Pelegri, J.L. and P~mfilo Masciangioli, 1987. [An analytical method for prediction of tides in channels.] Revta t~c. lntevep, 7(I):59-68. (In Spanish, English abstract.) A new method for solving unidimensional continuity and linear unforced momentum equations for tides consists in obtaining a single equation for the elevation and solving it by separation of variables. Temporal dependence is immediately obtained, and the spatial dependence equation can be solved when channel width and depth are expressed as functions of distance. Solutions for cases when width is constant, linearly variable and exponentially variable are presented, and the method's advantages and disadvantages are discussed. The method is employed for the Maracaibo Straits using known values for the tidal elevation as boundary conditions, and explicit solutions obtained compare well with observations. Dept. de Tecnol. de Produccion, INTEVEP, S.A., South America.

88:2574 Pingree, R.D. and G.T. Mardeil, 1987. Tidal flows around the Channel Islands IU.K.I.J. mar. biol. Ass. U.K., 67(4):691-707. Tidal streams in the Channel Islands region are rotary anticlockwise. At spring tides anticlockwise Eulerian residual currents ~ 2 0 cm s ~ develop around Guernsey which indicate that frictional effects exceed those due to the Earth's rotation. Lagrangian anticlockwise residual currents can exceed 60 cm s J at spring tides, indicating Stokesinduced currents are larger than Eulerian residual currents around Guernsey. Remote sensing studies show anticlockwise-directed jets, also indicating an anticlockwise circulation around the island. A tidal circulation pattern for the area is presented based on anticlockwise gyres around all major topographic features in the region. This flow pattern is consistent with formation of the front between Guernsey and Jersey and the residual currents derived from a numerical model. The Lab., Mar. Biol. Assoc., Citadel Hill, Plymouth PLI 2PB, UK.

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A. PhysicalOceanography

88:2575 Thomas, R.H., 1987. Future sea-level rise and its early detection by satellite remote sensing. Frog. Oceanogr., 18:23-40. Based upon an average projected rise in global temperature of about 3C °, a l-m rise in sea level is possible by the year 2100. The importance and feasibility of an 'early warning system' centered on satellite monitoring of changes in relevant parameters (e.g., surface temperatures, sea ice area and volume, summer melting and glacier discharge of ice caps, etc.) are discussed. Joint Oceanogr. Inst., Inc., 1755 Massachusetts Ave. N.W., Washington, DC 20036, USA. (emm)

AI60. Waves, oscillations 88:2576 Bishop, C.T. and M.A. Donelan, 1987. Measuring waves with pressure transducers. Coast. Engng, Amst., I 1(4):309-328. The measurement of waves with pressure transducers has been practised since around 1947, but there remains a considerable difference in findings on the adequacy of linear wave theory to compensate the pressure records. Measurements of surface elevation in gravity waves are compared with corresponding estimates from simultaneous subsurface pressure measurements. A review of previous work precedes a description of laboratory tests in a 103-m-long wave flume. Pressure transducers and surface-piercing capacitance wave probes are used to collect data in water depths of 0.9 and 1.2 m with monochromatic and irregular waves. Results indicate linear theory is adequate to compensate pressure records to give surface wave heights to within five percent. Reasons for greater discrepancies in previous studies are discussed. Nat. Water Res. Inst., P.O. Box 5050, Burlington, ON L7R 4A6, Canada. 88:2577 Ewing, J.A. and A.K. Laing, 1987. Directional spectra of seas near full development. J. phys. Oceanogr., ! 7(10): 1696-1706. Four years of simultaneous wave and wind data from a buoy in the southwest approaches to the British Isles were screened for conditions approaching full development. For wind speeds below 16 m s ~, the averaged frequency spectrum lies consistently below the Pierson-Moskowitz spectrum for fully developed seas; for higher wind speeds, spectra in the region of the peak have similar values to this spectrum. Values of nondimensional wave energy are significantly lower than the Pierson-Moskowitz

4()9

value for wind speeds less than 16 m s ~; for higher wind speeds, nondimensional wave energy is close to the P - M value. The spread parameter s. was more reliable for studying directional spread, l~stimates of s~ as a function of wave frequency relative to peak frequency differ from the expression for fetchlimited waves; peak value is comparable, but the decrease with increasing frequency is less rapid. Inst. of Oceanogr. Sci., Wormley, Surrey GU8 5UB, UK. 88:2578 Gordon, R.L. and J.M. Huthnance, 1987. Stormdriven continental shelf waves over the Scottish continental shelf. Continent. Shelf Res., 7(9): 1015-1048. Currents and winds were observed over 3 years at two stations east and west of the Shetland Islands. Two types of responses to severe winter storms were observed: an oscillatory response and a 'quasi-steady response.' Both appeared to be lowest mode continental shelf waves (CSW) but from different places on the dispersion curve. A model is presented for CSW generation at all frequencies, with particular emphasis on results for the 'resonant' regime, which predicts the dominant characteristics of both oscillatory and quasi-steady responses. RD Instruments, 9855 Businesspark Ave., San Diego, CA 92131, USA. 88:2579 Hayer, Sverre, 1987. On the joint distribution of heights and periods of sea waves. Ocean Engng, 14(5):359-376. In the design of offshore structures, a consistent method of choosing the height and period for the adopted design wave may be crucial. Here the joint probability density function for height and period is considered. The adequacy of a simple theoretical model for the joint distribution under stationary conditions is investigated, using measurements achieved during storms in northern North Sea. Slightly modified, the model is of reasonable accuracy for the highest waves. Design curves regarding simultaneous values of heights and periods are estimated with this model and their impact on design is discussed. Statoil, P.O. Box 300, N-4001 Stavanger, Norway. 88:2580 Langley, R.S., 1987. A statistical analysis of nonlinear random waves. Ocean Engng, 14(5):389407. A statistical analysis is presented based on secondorder random wave theory. The analysis technique is similar to a method available for the statistical analysis of a two-term Volterra series. The statistical

410

A. Physical Oceanography

problem can be reduced to that of finding the eigenvalues and eigenvectors of two real symmetric matrices, from which the cumulants, characteristic function, and probability density function of the surface elevation can be found. Various numerical examples are considered, and the possibility of extending the technique to deal with spreading seas is discussed. Offshore Structures Group, Coll. of Aeronautics, Cranfield Inst. of Tech., Cranfield, Beds. MK43 0AL, UK. 88:2581 Madsen, P.A. and J. Larsen, 1987. An efficient finite-difference approach to the mild-slope equation. Coast. Engng, Amst., 11(4):329-351. A system of differential equations, the stationary part of which can be reduced to the elliptic mild-slope equation, is derived. The transient terms make the system of equations hyperbolic and similar to the system of equations governing nearly horizontal flow. The highly efficient ADI algorithm for the latter is used iteratively to find the stationary solution. By extracting the time-harmonic part and using a varying time step in the iterations, computational time is reduced greatly compared with previous techniques. Danish Hydraulic Inst., Agern Alle 5, DK-2970 Horshoim, Denmark. 88:2582 Nakano, Masito and Naohiro Fujimoto, 1987. Seiches in bays forming a coupled system. J. oceanogr. Soc. Japan, 43(2): 124-134. The seiches occurring in two adjacent bays situated at the mouth of Tokyo Bay are very regular, and the phenomenon of beat appears in their amplitudes of oscillation. A theoretical explanation of this phenomenon suggested that a kind of coupling takes place between the two bays through a portion of water flowing across the mouth of each bay. In this paper, the validity of the theory has been proved in a series of hydraulic model experiments. The experiments have shown that, in the case of the bays mentioned, there are two distinct modes of oscillation: (1) the co-phasic oscillation and (2) the contra-phasic oscillation; because the frequencies of these oscillations are close to each other, when they interfere the beat phenomenon occurs. 4-8-14, Higashi, Kunitachi, Tokyo, 186, Japan. 88:2583 Pinkel, R. and J.A. Smith, 1987. Open ocean surface wave measurement using Doppler sonar. J. geophys. Res., 92(C12):12,967-12,973. Doppler sonars were used to scatter 75-kHz sound from the underside of the sea surface at low angle, as

OI. R (1988) 35 (5)

well as from the interior of the mixed layers. Surface gravity waves were seen in velocity estimates from the surface scattering sonar, even though wave conditions were unusually calm. Valid measurements of surface motion were obtained at distances of 600 to 1400 m. A second sonar which transmitted horizontally and scattered from the mixed layer interior also sensed surface waves, although with amplitude reduced in proportion to decay of the motions with depth. Wave number-frequency spectra of observed motions are consistent with linear theory. This technology enables the synthesis of kilometer-long surface wave arrays in the open sea, without the cost and logistical support associated with large-aperture arrays. The Doppler acoustic approach can also provide information on lowerfrequency surface currents and on spatial variations which might affect wave propagation. Scripps Inst. of Oceanogr., Univ. of Calif., La Jolla, CA 92093, USA. 88:2584 Soulsby, R.L., 1987. Calculating bottom orbital velocity beneath waves. Coast. Engng, A mst., 11(4):371-380. Methods are presented for calculating directly from a known wave height, period and water depth the orbital velocity produced at the sea bed by surface waves. Two curves are sufficient to calculate rootmean-square bottom orbital velocity for wavespectra having any one of the JONSWAP, PiersonMoskowitz, Bretschneider, ISSC or ITTC forms. A third curve covers the monochromatic case. Other curves allow the ratio of the peak periods of bottom orbital velocity and surface elevation to be calculated. Values are deduced for the height and period of the monochromatic wave which most closely matches the bottom orbital velocity obtained from a full spectral representation, optimised over water depths ranging from deep water to breaking. Hydraulics Res, Ltd., Wallingford, Oxfordshire OXI0 8BA, UK. 88:2585 Sun, Wenxin, 1987. A further study of ultra-shallow water storm surge model. J. Shandong Coll. Oceanol., 17(1):34-45. (In Chinese, English abstract.) Inst. of Phys. Oceanogr., Shandong Coll. Oceanol., Qingdao, People's Republic of China. 88:2586 Tsai, W.-T. and D.K.P. Yue, 1987. Numerical calculation of nonlinear axisymmetric standing waves in a circular basin. Phys. Fluids, 30(11): 3441-3447.

O I, R ( 1988 ~3fi 131

A. Physical O c e a n o g r a p h y

The solution is obtained numerically by direct collocation of truncated Fourier and Dini series in time and radial coordinates, respectively. The method produces accurate results which offer substantial improvements, especially in shallow depth, over existing solutions based on perturbation expansions. Numerical results for frequency, partition of energy, surface profiles, and particle trajectories are presented for both deep and shallow water for a range of steepnesses. Salient features such as the nonmonotonic dependence of frequency on steepness at certain depths, characteristic of two-dimensional standing waves, are also observed for axisymmetric standing waves. Dept. of Ocean Engng, MIT, Cambridge, MA 02139, USA. 88:2587 Xu, Delun, Decai Jiang and Fengcong Wang, 1987. Numerical calculation for wave ray under the effects of topography and current. J. Shandong Coll. Oceanol., 17(i):1-9. (In Chinese, English abstract.) Dept. of Phys. Oceanoi. and Mar. Meteorol., Shandong Coll. Oceanol., Qingdao, People's Republic of China.

AI80. Internal waves and tides 88:2588 Hebert, Dave, 1987. An estimate of the effective horizontal eddy viscosity in the Gulf Stream due to internal waves. J. phys. Oceanogr., 17(10): 1837-1841.

Variation in the horizontal Reynolds stress due to the internal wave field with respect to location of the Gulf Stream is examined. These measurements are from an array of current meter moorings placed in the mean path of the Gulf Stream at 59°W. Temperature was used as an indication of the current meter's position relative to the Gulf Stream. No systematic variation in Reynolds stress with respect to location of the Gulf Stream can be seen. From estimates of the large-scale horizontal shear, an upper limit for the magnitude of the horizontal eddy viscosity coefficient was 50 m: s ~. Dept. of Oceanogr., Dalhousie Univ., Halifax, NS B3H 4Jl, Canada. 88:2589 Marmorino, G.O., L.J. Rosenblum and C.L. Trump, 1987. Fine-scale temperature variability: the influence of near-inertial waves. J. geophys. Res., 92(C 12): 13,049-13,062.

Measurements made in the seasonal thermocline of the Sargasso Sea are examined for relationships

411

among small-scale temperature 'activity,' shear, "and internal wave variability. Patches of intense activity, 5-10 m high and several kilometers in length, persist within a near-inertial wave packet. The packet was tagged with a drogue and followed for about 16 hours as it was advected along an edge of a cold-core ring. Patches occur along surfaces of high vertical shear, where the Richardson number falls to values less than one. Within the patches are groups of small-scale internal waves and fluid overturns I-3 m high, associated with wave-breaking events. Away from the wave packet, activity levels are less, and the active fraction of the water column appears linked to variability in the internal wave field. Ocean Dynamics Branch, Acoustics Div., Naval Res. Lab., Washington, DC 20375, USA. 88:2590 Maze, R., 1987. Generation and propagation of non-linear internal waves induced by the tide over a continental slope. Continent. Shelf Res., 7(9): 1079-1104.

This model assumes a perfect fluid and small baroclinic variations in the level of the free surface with internal motion governed by Euler's and continuity equations. Equations for the two layers are coupled through the relationship between pressure gradients in these layers. Amplitude of the internal waves can reach up to 30 m at the shelf edge, increasing linearly with thickness of the upper layer, decreasing when stability increases, and decreasing away from the shelf edge on both sides. Wave shapes over the continental shelf and abyssal plain are very different. Averaged over time, group and phase velocities are close to values predicted by the linear theory. Interaction between the internal wave and barotropic tide, together with the forced wave near the shelf edge, result in a continuous current parallel to the shelf break showing spatially periodic changes of about the same wavelength as the internal waves. Lab. d'Oceanogr. Phys., Univ. de Bretagne Occidentale, F-29287, Brest Cedex, France. 88:2591 Mied, R.P., G.J. Lindemann and C.L. Trump, 1987. Inertial wave dynamics in the North Atlantic subtropical zone. J. geophys. Res., 92(C12)" 13,063-13,074. Doppler current profiler observations of an inertial wave packet are presented from a region where a cold-core ring impinges on a front. As a deployed drogue is advected by the current, the ship zigzags across the drogue's trajectory and vertical rotary velocity spectra indicate a downgoing inertial wave with a vertical wavelength which slowly changes

412

A. Physical O c e a n o g r a p h y

from ~ 5 0 to ~ 1 0 0 m. The wave's intrinsic frequency was measured for the first time. A horizontally synoptic data set is obtained at drogue depth by correcting for frontal advection and temporal rotation of the wave velocity. Examination of these data indicates a southgoing near-inertial wave with horizontal wavelength ~ 2 0 km, confined to a 25-km region. The wave is strongly influenced by Doppler shifting, accompanied by a slow counterclockwise turning of the horizontal wave number vector, decrease in intrinsic frequency, and an increase in vertical wavelength, in qualitative agreement with the data. Acoustics Div., Ocean Dynamics Branch, Naval Res. Lab., Washington, DC 20375, USA. 88:2592 Pinkel, Robert, Albert Plueddemann and Robin Williams, 1987. Internal wave observations from FLIP in MILDEX [Mixed Layer Dynamics Experimentl. J. phys. Oceanogr., 17(10):17371757. Off the coast of southern California, the velocity and density structure of the mixed layer was investigated in a series of experiments. From these data a set of 320 isopycnal surfaces was tracked, to indicate the vertical displacement of the internal wavefield. Both horizontal velocity, vertical displacement, and their vertical derivatives (shear and strain) are reasonably well measured in the same place at the same time. This co-occurrence is exploited to investigate the statistical properties of the observed motions and to quantify the degree of consistency with linear, shear-free internal wave theory. Attention is focused on t h ( depth range 200-300 m, below the depth where significant intrusive effects can be seen in the CTD data. Scripps Inst. of Oceanogr., La Jolla, CA 92093, USA.

A210. Ice 88:2593 Alfultis, M.A. and Seelye Martin, 1987. Satellite passive microwave studies of the Sea of Okhotsk ice cover and its relation to oceanic processes, 1978-1982. J. geophys. Res., 92(C12):13,01313,028. Ice concentration estimates obtained from SMMR are used to study two polynyas: one over the Kashegarova Bank, the other over the northwest continental shelf. The Kashevarova polynya, which may be related to the upwelling observed in historic summer cruises, occurs directly over the bank. For the continental shelf, a region of high ice production,

OI. R I 1988) 35 ( 5 )

the polynya areas are combined with heat flux estimates from weather station data to yield the production rates of ice, salt, and dense shelf water. The mixing of this dense shelf water with Pacific water yields a water mass unique to the Okhotsk: the layer of cold, low-salinity intermediate water between depths of 150 and 800 m. It is estimated that the dense shelf water is produced at an annual rate of about 0.5 Sv, and the intermediate water at a rate of 1-2 Sv, which yields a renewal time for this layer of 10~0 years. Internatl. Ice Patrol, Avery Point, Groton, CT 06340, USA. 88:2594 Anderson, M.R., 1987. The onset of spring melt in first-year ice regions of the Arctic as determined from scanning multichannei microwave radiometer data for 1979 and 1980. J. geophys. Res., 92(C12): 13,153-13,163. Satellite-derived melt signatures, determined by 18and 37-GHz vertical brightness temperatures, are associated with the initial melt of the snow pack on the sea ice surface. Within the Arctic Basin the melt signature is observed first in the Chukchi Sea and the Kara and Barents seas and moves westward from the Chukchi Sea and eastward from the Kara and Barents seas to the Laptev Sea region. The initial location of the melt signal varies with year; in 1979 the melt signature occurs first in the Chukchi Sea, in 1980 in the Kara Sea. The date for the initial melt varies between 1979 and 1980 by an average of 7-10 days with a maximum of 25 days in the Chukchi Sea region. Monitoring the occurrence of melt signatures can be used as an indicator of climate variability in the Arctic's seasonal sea ice zones. Climatol. Prog., Dept. of Geogr., Univ. of Nebraska, Lincoln, NE 68588, USA. 88:2595 Belitz, H.-J., C. Kottmeier, Rt~diger Hartig and H.-U. Stuckenberg, 1987. On the aerodynamic roughness of sea ice areas in the Arctic. Meteoro Iogische Rdsch., 40(4):97-107. (In German, English abstract.) Aerodynamic roughness over sea ice was studied at a number of Arctic locations using two approaches. A diabatic profile method using wind measurements from three heights of the Prandtl layer yielded credible results with respect to roughness dependence on surface structure and wind velocity accompanying beginning snow transport. A diagrammatic approach based upon atmospheric resistance laws showed large variations and deviations, attributed to inaccuracy of geostrophic wind estimates and local influences on wind measurements, z. Zt. Wetterdienstschule, Neustadt/Weinstr., FRG. (emm)

OLR (1988) 35 (51

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88:2596 Chu, P.C., 1987. An ice breeze mechanismJor an ice divergence-convergence criterion in the h~rginal ice zone. J. phys. Oceanogr., 17(10): 1627-i'632. A coupled air-ice--ocean theoretical model is used to show that an off-ice and divergent wind field not only produces a dilation of the MIZ but also generates a compaction of MIZ for some circumstances. An ice divergence-convergence criterion in the MIZ is used to help explain some features, such as ice edge bands, and the formation and maintenance of polynyas and leads. The model contains three parts: a thermally forced boundary layer air flow, a mechanically driven ice drift, and a reduced gravity ocean which are linked through the surface temperature gradient and various interfacial stresses. Results show that in the MIZ, a thermally generated surface wind blowing from ice to water is generally divergent over ice owing to the maximum surface temperature gradient at the ice edge. Such divergent local winds can make the ice flow either divergent or convergent, depending on the properties of ice and water underneath. For thin ice and a relatively deep surface water layer, the ice turning angle is small and the ice flow divergent. For thick ice and a relatively shallow surface water layer, the turning angle is large and the ice flow convergent. Dept. of Oceanogr., Naval Postgrad. School, Monterey, CA 93943, USA. 88:2597 Fomin, V.A. and V.N. Rodionov, 1985. Dissipation of mechanical energy in ice. Dokl. Earth Sci. Sect. (a translation of Dokl. Akad. Nauk SSSR), 285(6) :49-51. The ubiquity of ice in nature and its tendency to exist near melting suggest the existence of a mechanism for the dissipation of mechanical energy relying upon ice-water phase transition. A number of physical considerations suggest that such phase ~ transitions occur in ice even when mechanical energy is low on average. Experimental evidence for a distinctive dissipative mechanism is presented and discussed. Shmidt Inst. of Phys. of the Earth, Acad. of Sci., Moscow, USSR. (emm) 88:2598 Jeffries, M.O., 1987. The growth, structure and disintegration of Arctic ice shelves. Polar Rec., 23(147):631-649. The only known ice shelves in the Northern Hemisphere are on the north coast of Ellesmere Island. Present Arctic ice shelves, as much as 40-50 m thick, are remnants of the once extensive Ellesmere Ice Shelf, whose disintegration created many ice islands known to circulate in the Arctic Ocean

413

for 35 years or more. Both ice islands andice shelves are distinguished by their parallel ridges and troughs, probably due to the effects of wind and meltwater. Ice shelf growth began about 4000 BP when glaciers flowed off the land and sea ice grew thick and remained fast to the coast, acting as platforms for snow and ice accumulation and under-surface accretion of ice. Although much has been learned about Arctic ice shelves in recent decades, many questions remain concerning calving mechanisms, bottom freezing, sea ice growth and ridge and trough origins. Geophys. Inst., Univ. of Alaska, Fairbanks, AK 99775-0800, USA. 88:2599 Lemke, Peter, 1987. A coupled one-dimensional sea ice-ocean model. J. geophys. Res., 92(CI2): 13,164-13,172. A prognostic one-dimensional mixed layer.-pycnocline model describing the vertical structure of the upper ocean is coupled to a thermodynamic sea ice model, and compared with the more usual sea ice model overlying a fixed mixed layer with constant oceanic heat flux. It is then applied to investigate the effect of temporal and regional variations of the entrained oceanic heat flux on sea ice cover in both polar regions. In the Southern Ocean a standard simulation is compared with two perturbation experiments, both describing the occurrence of a polynya. In the Arctic Ocean the effect 6f possible Soviet river diversions is investigated. The response of the coupled model to paleoclimatic forcing and boundary conditions is presented. Max P[anck Inst. fur Meteorol., Bundestr. 55, D-2000 Hamburg 13, FRG. 88:2600 Ross, Becky and J.E. Walsh, 1987. A comparison of simulated and observed fluctuations in summertime Arctic surface albedo. J. geophys. Res., 92(C 12): 13,115-13,125. The melt cycle during two Arctic summers is simulated with a dynamic-thermodynamic sea ice model. Regional, seasonal and interannual variability of the surface albedo is compared directly with corresponding estimates. Despite the large seasonal variability of the observationally derived regional albedos, the largest error in the simulated albedo for any region or month is approximately 0.10. The model also captures the interannual variability of the regional albedos, lower in 1977 than in 1979 because of earlier onset of melt. The air temperature component of the model's thermodynamic forcing explains most of the interannual variability of regional albedo. Sensitivity tests show the model is at least as sensitive to the specification of monthly

414

A. Physical Oceanography

snowfall as to parameterization of the snow and ice albedos. Dept. of Atmos. Sci., Univ. of Illinois, Urbana, IL 61801, USA. 88:2601

Saigne, C. and M. Legrand, 1987. Measurements of methanesulphonic acid in Antarctic ice. Nature, Lond., 330(6145):240-242. Coastal area precipitations exhibit unexpectedly high MSA/n.s.s. SO4-" (methanesulphonic acid/non-seasalt sulphate) weight ratios (r) compared with those of mid-latitude atmospheres. At higher elevations the r values suggest a marine biogenic input of more global significance. The MSA concentrations confirm that n.s.s. SO4-" in Antarctic ice is mainly derived from marine biogenic activity. During the last ice age, MSA contents were 2-5 times higher than today. This study demonstrates the feasibility of reconstructing past marine biogenic activity of global significance. Lab. de Glaciol. et Geophys. de I'Environ., BP 96, 38402 St Martin d'Heres Cedex, France.

A260. Acoustics 88:2602

Fisher, C.A. and F.K. Duennebier, 1987. A technique for calculating bottom reflection loss from borehole data. J. acoust. Soc. Am., 82(5):!727-1735. NORDA, NSTL, MS 35929, USA. 88:2603

Kachoyan, B.J. and C. Macaskill, 1987. Acoustic scattering from an arbitrarily rough surface. J. acoust. Soc. Am., 82(5): 1720-1726. Dept. of Appl. Math., Univ. of Sydney, NSW 2006, Australia. 88:2604

Lin, Junxuan, Shuquan Wang, Zhenhua Yang and Shaohua Hui, 1987. The remote sensing of the acoustic characteristics of shallow sea sediment by the ray parameter method. J. Shandong Coll. Oceanol., 17(1):63-70. (In Chinese, English abstract.) Dept. of Mar. Phys., Shandong Coll. of Oceanol., Qingdao, People's Republic of China. 88:2605

McDaniel, S.T. and D.F. McCammon, 1987. Composite-roughness theory applied to scattering from fetch-limited seas. J. acoust. Soc. Am., 82(5): 1712-1719. Appl. Res. Lab., Pennsylvania State Univ., P.O. Box 30, State College, PA 16804, USA.

OLR (1988) 35 (5)

88:2606

Miller, A.R. and Emanuel Vegh, 1987. Comparison of the rough surface reflection coefficient with specularly scatterod acoustic data. J. acoust. Soc. Am., 82(5):1836-1838. Naval Res. Lab., Wash-

ington, DC 20375-5000, USA. 88:2607

Mailer, M., 1987. Experimental investigations on focusing of weak spherical shock waves in water by shallow ellipsoidal reflectors. Acustica, 64(2): 85-93. 88:2608

Namazi, Mohamad and J.A. Stuller, 1987. A new approach to signal registration with the emphasis on variable time delay estimation. IEEE Trans. Acoust. Speech Signal Process, ASSP-35(12): 1649-1660. Dept. of Elect. Engng, Michigan Tech. Univ., Houghton, MI 49931, USA. 88:2609

Poir6e, B., 1987. The characteristic equation of acoustic gravity-waves in a plane stratified flow. Acustica, 64(2):80-84. (In French, English abstract.) The characteristic differential equation of acoustic gravity-waves in a planar flow, which is continuously stratified, heavy, heterogeneous, and in adiabatic evolution is given. This equation is obtained from Gaibrun's equation, which describes the evolution of the Lagrangian acoustic displacement, in the mixed representation (Lagrangian perturbations, Euler variables). DRET/SDR/G63, 26, bd Victor, 75996 Paris-Armees, France. 88:2610

Smith, J.O. and J.S. Abel, 1987. Closed-form leastsquares source location estimation from rangedifference measurements. IEEE Trans. Acoust. Speech Signal Process., ASSP-35(12): 1661-1669. Systems Control Tech., Paio Alto, CA 94304, USA. 88:2611

Sun, Yueyan, Deming Lu and Peiqiang Zhou, 1987. An analysis of the sound speed characteristics in the sea near the estuary of the Yangtze River and in the northwestern Pacific Ocean. J. Shandong Coll. OceanoL, 17(1):54-62. (In Chinese, English abstract.) Dept. of Mar. Phys., Shandong Coll. of Oceanol., Qingdao, People's Republic of China. 88:2612

Yang, T.C., 1987. A method of range and depth estimation by modal decomposition. J. acoust.

OLR (1988)3515)

A. PhysicalOceanography

Soc. Am., 82(5):1736-1745. Naval Res. Lab., Washington, DC 20375-5000, USA. 88:2613 Ziomek, L.J. and R.J. Blount Jr., 1987. Underwater acoustic model-based signal processing. IEEE Trans. Acoust. Speech Signal Process., ASSP35(12):1670-1683. A model-based signal processing algorithm, used with an FFT beamformer for planar arrays, computes phase weights that correct for deterministic, ocean medium, phase effects due to ray bending as a signal propagates in the inhomogeneous ocean medium whose index of refraction is a function of depth. Performance was evaluated in the context of an underwater acoustic communication problem, to determine the impact of the algorithm on the probability of detecting single rectangular-envelope continuous wave and linear frequency modulated pulses as a function of the input signal-to-noise power ratio at a single element in the receive array for a given probability of false alarm. Preliminary results show significant increases in performance for a correlator receiver. Dept. of Elect. and Computer Engng, Naval Postgrad. School, Monterey, CA 93943, USA.

A290. Physical processes, properties (diffusion, turbulence, etc.) 88:2614 Baker, M.A. and C.H. Gibson, 1987. Sampling turbulence in the stratified ocean: statistical consequence of strong intermittency. J. phys. Oceanogr., 17(10): 181%1836. Turbulence and turbulent mixing are strongly intermittent in amplitude, space, and time. 'Intermittency factor' departures from lognormality are remarkably similar to those for Monte Carlo distributions contaminated with simulated noise and undersampling effects. Modelling shows that large intermittency factor values cause large uncertainty in mean estimation unless the number of data samples is extremely large. If intermittency is ignored, mean dissipation (viscous and temperature) rates will probably be underestimated from a small number of samples, lntermittency may cause qualitative errors as well: minimum values in vertical profiles of mean dissipation rates are commonly inferred from profiles at the seasonal thermocline depth and the equatorial undercurrent high-velocity core depth where maxima may actually exist. Such minima are shown to be artifacts of the extreme intermittency in these strongly stratified layers. Appi. Phys. Lab., Johns Hopkins Univ., Laurel, MD 20707, USA.

415

88:2615 Bowers, D.G. and G.W. Lennon, 1987. Observations of stratified flow over a bottom gradient in a coastal sea. Continent. Shelf Res~ 7(9): 1105-1121. The outflow from Spencer Gulf (south coast of Australia) is described. In summer, salt accumulates due to high evaporation rates, and in winter the horizontal density gradient drives a gravity current traceable from the mouth for ~ 1 0 0 km across the continental shelf. The current has a mean width of ~ 2 0 km and thickness of --20 m. Its mean speed is ~0.1 m s t, but time series measurements indicate episodes ranging between 0 and 0.2 m s t. Mean velocity is consistent with predictions of a Ch6zy type formula using bottom and interfacial friction coefficients both of order 3 x 10 2. Friction causes the current to slip down-slope at an angle of ~ 4 0 ° to the isobaths. Outflow salt flux is consistent with the rate of salinity decrease in the gulf during winter. Flinders Inst. of Atmos. and Mar. Sci., Flinders Univ., Bedford Park, SA 5042, Australia. 88:2616 Dunbar, D.S. and R.W. Burling, 1987. A numerical model of stratified drculation in Indian Arm, British Columbia. J. geophys. Res., 92(C12): 13,075-13,105. The model is time dependent and includes adveetive terms, horizontal and vertical turbulent diffusion of momentum and salt, and variations in width and depth. Initial and boundary conditions based on winter measurements were used to study the inlet's response to tidal forcing. The friction term was tuned to match calculated and observed dissipation rates. Evidence for a standing wave pattern in the response of the M. and K~ tidal constituents is discussed. A comparison of model results with cyclesonde current meter time series at two locations is consistent with resonance. A modal decomposition of the calculated response shows that most of the energy is contained in the barotropic and first baroclinic modes, with the former dominating near the sill and the latter in the deep basin. Second-mode energy was significant for the K~ at some locations. Seaconsuit Mar. Res. Ltd., 820-1200 W. 73rd Ave., Vancouver, BC V6P 6G5, Canada. 88:2617 Fedorov, K.N. and A.I. Pereskokov, 1986. Classification of thermohaline conditions of stratification in the World Ocean. Soy. Met. Hydrol. (a translation of Meteoro/ogiya GidroL), 12:59-63. The ultimate role of dipycnic transfer due to differential-diffusion convection in climate formation motivates this study, a layer by layer probabilistic measure of the distribution of temperature

416

A. Physical Oceanography

and salinity components of hydrostatic stability in the water column. The predominant thermohaline conditions in the upper 1000 m favor differentialdiffusion convection. Conditions of stable stratification predominate as a whole in the World Ocean only because of their overwhelming prevalence in deeper waters. (emm)

88:2618 Freilich, M.H. and S.S. Pawka, 1987. Statistics of S,, estimates. J. phys. Oceanogr., 17(10): 1786-1797. The statistics of S,, (the onshore flux of longshore momentum) estimates derived from orthogonalcomponent measurements are examined. The probability density function (pdf) for S,,(f) estimates is derived, and a closed-form solution for arbitrary moments of the distribution is obtained. Characteristic functions are used to derive the exact pdf of total S,,. In practice, a simple Gaussian approximation is found to be highly accurate even for relatively few degrees of freedom. Implications for experiment design are discussed, and a maximum likelihood estimator for a posteriori estimation is outlined. Jet Propulsion Lab., Calif. Inst. of Tech., Pasadena, CA 91109, USA.

88:2619 Geyer, W.R. and J.D. Smith, 1987. Shear instability in a highly stratified estuary. J. phys. Oceanogr., 17(10): 1668-1679. Sheai" instability is the principal mechanism of vertical exchange within the pycnocline of a salt wedge estuary. High-resolution velocity and density measurements, as well as high-frequency acoustic imagery, allowed direct comparison of instantaneous Richardson number distributions to shear instability. The theoretical stability threshold of 0.25 is consistent with the measurements, based on estimates of gradients that contain the mean as well as fluctuations due to internal waves. An effective stability threshold based on mean gradients is approximately one-third, reflecting a significant contribution of internal wave shear. The integral effect of the mixing process is to homogenize the gradients of velocity and density, producing linear profiles of these quantities across the pycnocline. A turbulent Prandtl number o f unity is suggested by the vertical distributions of velocity and density during periods of active vertical mixing. A simple model for mixing in stratified shear flows is proposed, which is applicable to estuaries and other environments with a dominant mean shear. WHOI, Woods Hole, MA 02543, USA.

O L R (1988) 35 {5 )

88:2620 Kelley, Dan, 1987. Interface migration in thermohaline staircases. J. phys. Oceanogr., 17(10): 1633-1639. A theory for the vertical migration speed of interfaces within thermohaline staircases is developed and illustrated with several oceanic examples. It is expressed in terms of layer-to-layer variations in the vertical buoyancy flux. Three mechanisms can induce migration: (1) the nonlinearity of the equation of state; (2) layer-merging; and (3) interfacesplitting. The theory predicts that migration will be much slower for nonlinearity than for the others. Even so, the net effect of migration associated with layer-merging and interface-splitting should be small, since the interfaces will not have time to migrate very far before the staircase readjusts to a new, migration-free, equilibrium state. The largescale effects of interface migration are predicted to be small, with migration-induced heat and salt fluxes being less than 20% of the double-diffusive fluxes. The migration itself will be difficult to observe: for example, we calculate the speed to be 10 ~ m s ~ for Arctic halocline staircases. This is much too small to explain the apparent migration speed derived by •. tracking interfaces in CTD Arctic profiles. Therefore, the apparent migration is probably a sampling artifact associated with advection of staircase anomalies. WHOI, Woods Hole, MA 02543, USA. 88:2621 1987. Vorticity control. J. phys. • Oceanogr., 17(10): 1758-177 I.

Nof,

Doron,

When fluid with relative vorticity intrudes into a barotropic channel, it is pressed by the ambient fluid against one of the channel walls. Because of the excess pressure behind, it propagates along the wall and forms a 'nose' at the leading edge. As the nose advances, the ambient fluid escapes to compensate for the intruding mass. The speed at which the leading edge advances, and the associated mass flux through the channel is the focus of this study. Possible applications to oceanic situations are mentioned. Dept. of Oceanogr., Florida State Univ., Tallahassee, FL 32306, USA. 88:2622 Stern, M.E,, 1987. Large-scale lateral entrainment and detrainment at the edge of a geostrophic shear layer. J. phys. Oceanogr., 17( I 0): 1680- i 687. Evolution of large-amplitude disturbances at the outer edge of a quasi-geostrophic shear layer depends on the sign of the outward gradient of potential vorticity. Entrainment of ambient water can occur when the gradient of relative vorticity

OLR (1988)35(5)

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dominates in the potential vorticity. Detrainment from the current can occur when the gradient of isopycnal thickness dominates, and long, thin filaments of finite area are 'pinched off' into the surrounding water mass. This is verified using" a quasi-geostrophic model having piecewise uniform potential vorticity. Contour dynamical calculations for many initial conditions allow definition and tabulation of an entrainment/detrainment velocity, used for an order of magnitude estimate of heat or salt flux on an isopycnal surface in a warm core ring. Dept. of Oceanogr., Florida State Univ., Tallahassee, F L 32306, USA. 88:2623 Stern, M.E., 1987. Horizontal entrainment and detrainment in large-scale eddies. J. phys. Oceanogr., 17(10): 1688-1695.

The evolution of disturbances on a circularly symmetric eddy having uniform vorticity in a central

core, in a surrounding annulus, and in the irrotational exterior water mass is computed. This vortex is unstable when its annular width is less than the core radius. Calculations for the nonlinear regime show that amplification of azimuthal wavenumber n = 2 causes the vortex to split into two dipoles, in agreement with previous calculations for a smoothed vorticity field. This paper concentrates on largeamplitude disturbances on the outer edge of a stable, robust eddy. Lateral wave breaking of vorticity isopleths causes intrusions of the exterior water mass into the central core of the vortex, a physical process relevant to lateral diffusion and isopycnal mixing in baroclinic ocean eddies. Similar intrusive features occur for an n = 1 disturbance, which also causes 'self-propagation' of the entire eddy. Large-amplitude disturbances can be initiated by external eddies or currents. A simple model exhibits filaments detraining from the eddy, as well as intrusive features. Dept. of Oceanogr., Florida State Univ., Tallahassee, FL 32306, USA.

B. MARINE METEOROLOGY

BI0. Apparatus and methods 88:2624 Enting, I.G. and J.V. Mansbridge, 1987. Inversion relations for the deconvolution of CO 2 data from ice cores. Inverse Problems, 3(4):L63-L69. CSIRO Div. of Atmos. Res., Private Bag No. ,1, Mordialioc, Vic. 3195, Australia. 88:2625 Forbes, A.M.G., 1987. M E T S P A R - - a marine METeorological SPAR buoy. CSIRO mar. Labs Rept, 162:6pp.

The first configuration in a CSIRO instrument development program designed to provide a meteorological data acquisition system, including a buoy and mooring suitable for long-term deployment in both shallow and deep water, Metspar is a spar buoy with radio beacon and Aanderaa meteorological instruments. Seven were built and deployed during the Australian Coastal Experiment (ACE) in 1983/84, which proved an ideal test for instruments,

buoys and moorings. Experience gained with Metspars contributed significantly to the next generation of offshore meteorological buoys, currently on trial off Western Australia. CSIRO Div. of Oceanogr., Mar. Lab., GPO Box 1538, Hobart, TAS 7001, Australia.

B40. Area studies, surveys, weather 88:2626 Cadet, D.L. and Steve Greco, 1987. Water vapor transport over the Indian Ocean during the 1979 summer monsoon. Part !I. Water vapor budgets. Mon. Weath. Rev., 115(10):2358-2366.

Over the Arabian Sea the terms of the moisture balance equation, except evaporation, strongly fluctuate depending on monsoon activity. The relative contribution to the monsoon moisture supply by water vapor transport across the Equator and Arabian Sea evaporation varies as monsoon intensity changes from active through break and back to