Mag. 37 (1989) 155-165

Th. physical oceanography ofAustlalian waters-a reyrew*

P. G. BainesPresident, A,qslalian .Meteorological and Oceanographic Society

CSIRO Division of Atmospheric ResearchAspendale, Australia

(Manuscript received March 1989; revised May 1989)

trntroductionThe achievements in Australian oceanographyover the past fifteen years have seen it reacha level of wodd prominencp which greatlyexceeds its reputation in the past. The princi-pal objectives of this review are, first, to givea feeling for the flavour of modern Australianoceanography and what makes it interestingand even exciting, and second, to give someidea of the variety of phenomena involved.The article attempts to cover the whole regionbut is limited because of its length; the topicscovered should be regarded as a personal se-lection. I must apologise in advance to thosepeople whose work is not adequately repre-sented, referenced, or properly acknowledged.The review is intended for a wide audience,with no particular knowledge of physicaloceanography being assumed.

The Australian environment contains a richvariety of oceanographic features which arepeculiar to the region, or which are muchmore pronounced here than elsewhere. Thebottom topography of the region is very var-ied, as may be seen in Fig. l. The nearshoreregion contains long coastlines which runnorth-south and east-west, with both broadand narrow continental shelves, vast coral reefenvironments, extensive shallow tropical seasand the unique environment of Bass Strait.This diversity gives rise to a correspondingdiversity in physical phenomena, many ofwhich are as yet poorly understood. There

* This article is adapted from the President's Address tothe Australian Meteorological and Oceanographic Societyon 24 November 1988.

has, howover, been substantial progress madein recent years, particularly in the area ofcoastal oceanography, and each State now hasan active group working on understanding thelocal environment and addressing its problems.This progress has been made possible by theexpansion of effort by CSIRO and by thesupport provided by the Marine Science andTechnology Grants Scheme.

Fig. I Bathymetry of the Australian marine envi-' ronment. Depth contours are marked in

fathoms.

We may divide the subject up into threemain areas: (a) surrounding ocean currents,(b) tides, and (c) coastal oceanography, andwe will deal with these in turn.

156 Australian Meteorological Magazine 37:3 September 1989

Surrounding ocean currentsThese surface (i.e. upper ocean) currents aremostly driven by the winds acting over thewhole of the relevant ocean basin. Figure 2,which is part of a world chart printed inHamburg in 1943, shows a chart of the surfacecurrents in the Australian region obtained fromship drift data for the summer season' TheLeeuwin Current (see below) is conspicuouslyabsent, but otherwise no significant correctionsfrom more recent observations seem to benecessary. This is a statement of how little weknow about our surrounding oceans, and howlittle detail has been added to the deep sea inthe past 50 years, rather than that we knowit all. For example, the chart represents sum:mer mean conditions, but we are not awareof what the seasonal variations are with anyconfidence, even for the East Australian Cur-rent.

Fig. 2 Ocean currents in the Australian region insummer. From'Weltkarts zur iibersicht derMeerestrdmingen', Deutchen Seewartet1942, Longer arrows imply steadier cur-rents, thicker arrows imply stronger cur-rents. Dashed lines denote lines ofconYergence and divergence.

the coast, which usually happens a little tothe north of Sydney, Most of this warm waterflows back northward further offshore, or flowseastward along the mid-Tasman front to passnorth of New Zealand. Eddies form where thecurrent recirculates and 'pinches off'; exarn-ples are shown in Fig. 3. These d_eep anti-iyclonic warm-core eddies may drift aroundthe southern Tasman Sea, and then rejoin thecurrent by merging with it or possibly escapeinto the circumpolar current to the south'There is no evidence of a substantial meanflux through the Tasman Sea in either direc-tion and the bottom topography (principallythe Lord Howe Ridge) ensures that the deepwater is closed off. Figure 4 shows another

any other ocean basin. The influence of NewZealand, to the east, may be a significantfactor in this difference, and may control themean location where the current separatesfrom the coast.

Fig. 3 The East Australian Current system on ll

December 1980, showing two eddies (Maria

and Leo). Dark shades indicate warm water(from Cresswell and Legeckis 1986).

The Tasman SeaAs shown in Fig. 2, the inflow from the SouthEquatorial Current bifurcatos at the middle ofthe Great Barrier Reef region, with the south-ward flowing portion accumulating to formthe East Australian Current (EAC). The

Baines: The physical oceanography of Austral ian waters-a review t5 '7

Fig. 4 Same as for Fig. 3 but for 20 December1980. Note the extent of the change fromFig. 3 in just 9 days.

t E o ' E t s z '

**3t 5 4 "

The Indian OceanHere the circulation in the deep water in theAustralian region has hardly been observed atall. and a broad northward flow as shown inFig. 2 is largely inferred from ship drift andindirect considerations. No significant variabil-ity in the flow has been detected in this areaby satellite altimetty, except quite close toshore where it is associated with the LeeuwinCurrent.

An important and as yet undeterminedquantity for global ocean circulation is the'Indonesian throughflow', which is the quan-tity of fluid which flows into the Indian Oceannorth of New Guinea and through the Indo-nesian archipelago from the Pacific (the flowthrough Torres Strait is negligible). This fluxis important for global ocean budget and cli-mate calculations as well as for regionaloceanography, but attempts to measure it haveso far been frustrated by political and bureau-cratic factors. The best estimate to date, basedon circumstantial evidence. is about 15 Sver-drup.

TidesThe oceanic tides are forced by the differentialgravitational attraction of the sea waters byeach of the sun and the moon. The effect oncurrents is generally small except in shallowregions such as near coasts, where it may bethe dominant cause of fluid motions. Theoverall effect of tidal forcing may be repre-sented as the forcing of a rather complexoscillator (the oceans) at a number of discretefrequencies, mostly concentrated around al2-hour period (semi-diurnal) and a 24-hourperiod (diurnal), with a few at much longerperiods. The two most significant of theseconstituents are the M, (period 12.42 hours)due to the moon, and the S, (period 12.00hours) due to the sun, with the former havingthe larger amplitude in nearly all locations.The beating between these two componentsgives the familiar fortnightly pattern of springand neap tides.

Figure 5 (from Schwiderski 1979) showsthe pattern of amplitudes (a) and phases (b)of the M, constituent in the Australian region,including the amphidromic points which arecertain points of zero amplitude. Large ampli-tudes may occur in certain regions because theIocal geometry may be close to resonance fora particular frequency. A good analogy is an

j S 6 " r 5 g .

The Southern OceanThe dominant feature of the Southern Oceanis the Antarctic Circumpolar Current. Verylittle is known about the structure of thisbroad, deep current in the Australian region.Total transport is 130 Sverdrup (!20Eo).There are indications that the current followsbottom topography south of Australia, alongthe Indian-Antarctic Ridge which turns south-ward south of Tasmania. There is an interest-ing parallel here with storm tracks in theatmosphere which follow much the same path,and this correspondence has yet to be ex-plored. Observations made in the Drake pas-sage show that the current there has a bandedstructure with several more swiftly flowingcores embedded in a weaker eastward drift; itis not known if this description is also appli-cable to the Australian sector where the cur-rent is broader with smaller speeds. Note thatthe subtropical convergence (a boundary be-tween subtropical or tropical water and waterfrom further south) moves into the TasmanSea towards Cook Strait (see Fig. 2).

158 Australian Meteorological Magazine 37:3 September 1989

z 9

v. o

Fig. 5 The M2 tides in the Australian region. (a)Amplitudes in cm, and (b) Greenwich phasesin degrees. From the numerical interpola-tion model of Schwiderski (f979).

organ pipe which is closed at one end andopen at the other; this pipe resonates forsound waves which have a wavelength equalto four times the length of the pipe. In thesame wayr surfaqe waves in the ocean travelat a speed (gd)'/'which varies from place toplace with the local depth d; waves propagat-ing over a continental shelf towards the coast(the closed end) may resonate if their wave-length is equal to four times the distancebetween the coast and the shelf-break or edge(the open end). This is just one commonexample of resonance and, in general, localgeometry and depth variations result in con-siderable variation in the amplitude of eachtidal constituent in coastal regions. Tides areessentially linear phenomena, but in these

shallow regions they may become non-linearif their amplitude is large enough, and boresmay form in narrowing shallow regions closeto the shore. There are two main regions oflarge amplitude for semi-diurnal tides (and theM, in particular) around Australia, namelythe northwest shelf and the southern GreatBarrier Reef region.

The patterns of amplitudes and phases forS, are very similar to those for M, (which isnot surprising because the frequencies are sim-ilar), with the amplitudes being typicallysmaller by about 50 per cent. This ratio is notconstant; in Spencer Gulf, for example, thetwo amplitudes are equal, so that there is alarge amplitude at spring tide, but at neaptide there is virtually no tide at all.

We may 'zoom in'on the two regions wherethe M, is large. Figure 6 (Griffin et al. 1987)shows the cotidal chart for M, for the GreatBarrier Reef south of Broad Sound (the big'kink' in the Queensland coast, visible inFig. 1) which is the region of largest tides onthe Queensland coast. The geometry here isaffected by dense coral reefs offshore whichact as a barrier to the tidal flow so that itapproaches Broad Sound along the shelf fromthe north and the south, as shown in Fig. 6.This channelling gives rise to a local resonancewhich magnifies the tidal amplitude by a fac-tor of 4 (Middleton et al. 1984). The localestuarine geometry of Broad Sound is itselfclose to resonance, giving a further magnifi-cation of 1.5. When the effects of the otherconstituents (principally 52) are added, thetidal range at Broad Sound can be 35 feet, or10.7 m (Fl inders 1814),

Figure 7 (from Schwiderski (1979), drawnby Holloway (1983)) shows cotidal lines forM, for the northwest shelf; here the lf 4 waveresonance mechanism applies, and the tidesare the most significant part of the local cur-rent pattern. Some further effects of the tidesin this region will be mentioned later. Thelargest tides in Australia are found at SecureBay (near Broome) where the range can reach40 feet, or 12.2m (Easton 1970).

Coastal oceanographyMost of the interesting work in recent yearshas been done in coastal oceanography' Wewill start with the south coast of New SouthWales and move anticlockwise around thecountry.

Baines: The physical oceanography of Australian waters-a review 1 5 9

Fig. 6 M2 tidal height in (a) cm and (b) Green-wich phase lag for the region directly southof Broad Sound from a numerical model(from Griffin et al. 1987).

Fig. 7 Amplitude in metres (solid lines) andGreenwich phase (dashed) for the M2 con-stituent for the northwest shelf, drawn byHolloway (1983) from the results ofSchwiderski (1979).

South coast of New South WalesPerhaps the most significant development incoastal oceanography anywhere in the lastthirty years has been the discovery and com-

prehension of coastally trapped waves. Thesewaves may be regarded as topographic Rossbywaves over the continent slope, with the re-storing force due to potential vorticity varia-tion related to the bottom slope. An outlineof the essential mechanism is illustrated in Fis.8. If the density stratification of the ocean isneglected, a vertical column of water over thecontinental slope satisfies the vorticity equa-tion.

D , t + f6r( - ; - ) :0,

where f is the relative vorticity (that is, rela-tive to the local earth) of the fluid column, fthe Coriolis parameter, and H the local fluiddepth. A column of fluid at middle-level depthwith no relative vorticity (f : 0) will deveiopanticyclonic relative vorticity if it is displacedtoward the shore, owing to compression of thewater column, and cyclonic vorticity if dis-placed toward deep water. If, as shown in theplan view, an along-coast variation in on-offshore displacements is established, the patternof vorticity implies an associated fluid motionwhich causes the pattern to move to the rightfor an observer faiing the shore in the souih-ern hemisphere. In general, the shape of thetopography and stratification are very impor-tant, and there are several modes with differ-ent horizontal and vertical structure, but thesame physical principles apply. These wavesmay be of paramount importance for coastalupwelling, for coastal currents and their vari-ations, for sea level changes, and for associ-ated processes such as sediment movement.pollutant dispersal and fisheries.

\l \,/ l, ,l I "/ ,/.1, \ lv/r\1 ,{/t{"/ /Y,9{

^ o u r d o t o

I T r d . T o b l . s

a M o d a l

M a A m p l i l u d . ( c m l

A o u f d o t o

I Tid. Tqblei. \ Mod. l

M 2 h i g h t i d . ' E '

r60 Australian Meteorological Magazine 37:3 September 1989

Fig. 8 Schematic diagram illustrating the restor'ing force and direction of propagation forcoastally trapped waves, blsed on potentialvorticity eonservation.

with each other and, generally speaking, theCTW theoretical modes fitted the observationsquite well, except for effects attributed to EastAustralian Current eddies which moved intothe arrays. The only major discrepancy wasthat the CTW energy flux through each ofthe three main arrays was approximately thesame, so that instead of being generated onthe NSW coast as originally expected, thewave energy was entering the region some-where between Tasmania (where there waslittle energy on the east coast) and GaboIsland. We will return to this point later.

Fig. 9 A plan of the principal locations in theACE experiment (from Freeland et al.

Fig. l0 A perspective view of the instrument ar-rays deployed in the ACE experiment(from Freeland et al. 1986).

These waves were in fact first discovered

since. CTWs have now been observed in avariety of locations around the world.

To return to the southern NSW coast, thisnow historic stretch of coastline was chosenby Australians from the CSIRO Division ofOceanography and some participating Ameli-cans and eanadians as an ideal location for

place over a period of seven months in 1983and 1984. The design of the experiment con'sisted of three main sections of instruments to

three main lines. They are quite consistent

+

. B Deep

K b N t h t t & d l t

Baines: The physical oceanography of Austral ian waters-a review

Fig. lf Vertical,/offshore structure of the first three coastally trapped wave modes at each of the threeprincipal mooring lines, and the phase speed associated with each mode. Contours representconstant longshore velocity, with dashed lines representing the opposite directions to the solidlines. Dots represent instrument sifes (from Freeland et al. 1986).

Mcd,e2

Line 3

161

Great Barrier ReefThe north Queensland continental shelf is un-usual because of the numerous coral reefswhich are present throughout the region, andwhich are concentrated at the edge of theshelf. Understanding the effects of these reefsand constrictions on the flow on the shelf, andtheir complex effects on the biology of theregion, has been tackled by scientists from theAustralian Institute of Marine Science nearTownsville. In particular, these reefs tend toproduce small-scale fronts where sediments,zooplankton, eggs from spawning coral, and

t62 Australian Meteorological Magazine 37:3 September 1989

Fig. 12 Aerial photograph of a lee eddy behindRattray Island (length 1.5 km), Whitsun-day passage, Great Barrier Reef, on 4December 1982 (from Wolanski et al.r984).

Gulf of CarpentariaIn this unusual broad and shallow area. themean currents and the semi-durnal tides areboth weak. The tidal currents are mainly diur-nal and are not strong, and local winds andstorms seem to be significant for water move-ment, with bottom friction being importantbecause of the shallow depth (20-60 metres),particularly in the south. Evaporation fromthe region is very significant for atmosphericprocesses.

Northwest shelfThis is a very large and remote area and itsphysical phenomena have not yet been verywell explored, although some extensive meas-urements have been made in soecific locationsbecause of the presence of oii and gas fieldsin the region. The tides are quite substantial,as noted earlier, and the wind-driven and othercurrents are generally weak, apart from theoccasional effects of tropical cyclones. Conse-quently, the principal dynamical phenomenain the area seem to be governed by the tides.

An example which is visible from satellites rsshown in Fig. 13. Large tidal motions acrossthe edge of the continental shelf generate largeamplitude internal tides (internal waves oftidal period). These typically have wave-lengths of 20 to 40 km, but they often steepento form undular internal bores with wave-lengths of about 700 m or more. These fea-tures are dynamically similar to the 'morning

glories' observed in the atmosphere in theGulf of Carpentaria region and elsewhere.They may be seen from above the surfacebecause of the effect of the flow convergenceand divergence of the internal waves on thesurface roughness. Hence they are visible inthis Landsat picture which shows packets ofwaves from up to four tidal cycles. Internalwaves with this character have been seen insatellite imagery from many parts of the worldbut this particular picture is remarkable be-cause it contains more of these waves thanany other that I have seen-apart from thesemicircular bands in the centre, most of theright-hand (shallow water) part of the pictureis covered with them! Internal tides are im-portant because they may substantially in-crease the maximum tidal currents experiencedat a particular location, and this may be verysignificant for oil and gas platforms, for ex-ample.

The region is also significant because it isthe source region for the Leeuwin Current(Fig. la). This warm current flows southwardagainst the offshore flow and the prevailingwinds at speeds of about | /2 to I m s-r and isstrongest in autumn and winter. It is situatedover the continental slope with a width ofabout 40 km and continues, intermittently andfor different reasons, all the way to southernTasmania. This makes it one of the longestnarrow streams in the world, possibly evenlonger than the Nile (although the comparisonis facetious). Its properties have only recentlybeen fully recognised (e,g. Cresswell andGolding 1980), although the existence of warmwater offshore for swimming in winter hasbeen well-known to the residents of Perth formany years. The transport is about 2-3 Sver-drups and the factors causing it are not yetcertain. Two suggestions have been made: first,that it is primarily fed by the Indonesianthroughflow, and second, that it is fed byinflow from the Indian Ocean. as shown inFig. 14.

The structure of the Leeuwin Current var-ies substantially with time along its entire

Baines: The physical oceanography of Austral ian waters-a review t63

length. It often has a convoluted eddy char-acter as illustrated in Fig. 15, These eddies arepresumably due to dynamical instabilities(Griffiths and Pearce 1985) and may resulr inthe transfer of warm water offshore. It seemslikely that these eddies may play an importantpart in the life-cycle of the rock lobster in thesouthwest region.

Fig. 13 Northwest shelf. (a) Landsat image (29December 1972) showing internal wavetrains of the region shown in (b). Theprincipal wave trains and the shelf break(the 183 m depth contour) are also shownin the latter. The large shoal in the north-west corner is Ashmore Reef (from Baines1981).

Fig. f4 Schematic diagram of the Leeuwin Cur-rent (courtesy of F. Prata).

Fig. 15 Satellite image of the Leeuwin Currenr,showing the temperature anomaly at eachlatitude (courtesy of f,'. prats).

fnverse estuariesFlow close to the shore around much of theAustralian coast to the north, west and southis inluenced by the 'inverse estuary phenom-enon'. In the Australian coastal environmentfresh water run-off is generally small or non-existent. On the other hand, evaporation incoastal shallows is high due to the persistentsolar heating and this causes an accumulationof dense salty water which flows downhill outto sea. This in turn causes inflow towards thecoast at the surface. This circulation is the

122'E 124'E -?r f i i 126E

t64 Australian Meteorological Magazine 37:3 September 1989

reverse of the usual estuarine pattern, wherefresh water outflow occurs at the surface dueto river run-off, with entrainment causing saltwater inflow below. This contrast is illustratedschematically in Fig. 16 (although the proc-osses involved ate greatly simplified-this'normal' estuarine circulation is only one ofseveral types), This 'inverse estuarine' circu-lation is nbt restricted to estuaries although it

Bass Strait.

Fig. 16 Simplified schematic diagrams showing thecomparison between a'normalt estuary withcirculation driven by river inflow entrain-ing salt water from below, and &n'inverse'esturry, driven by evaporation in shallowwater.

systems have (mostly) only been observedthrough their effects on sea level variations,as recorded by tide gauges. Figure 17 (fromChurch and Freeland 1987)'shows disturb-ances propagating and growing from west toeast. Thetypicalpropagationspeedis - l0 m s',which is the same as that for weather systems.These coastally trapped waves show a signifi-cant degree of correlation with the CTWsobserved on the NSW coast in the ACE' Ifthe CTWs on the NSW coast are caused bythe CTWs on the south coast, their effectmust pass through Bass Strait since they arenot observed to pass around Tasmania.

Fig. l7 Subsurface pressure (sea level plus atmos'pheric) of low frequency disturbances at anumber of south coast locations showingeastward propagation during the ACE ex-periment, and compared with CTW node2 at Cape Howe (from Church and Free-land 1987).

Salt water inllow t

Very sal ly outf low

Coastally trapped waves on the southernshelfThe Australian southern coastline is unusualin that it is a region which supports coastallytrapped waves which propagate in the samedirection as the weather systems which forcethem. Resonance is therefore possible, givingrise to quite large amplitudes. To date, these

Bass StraitBass Strait itself has a number of interesting

portant quantity related to the southern coastbfWs is the flux of water through Bass Strait.Recent observations (Baines, Hubbert andPower 1989, personal communication) haveshown that flow through Bass Strait in winteroccurs in eastward surges lasting 2 to 3 days,which coincide with southwesterly airstreamsfollowing the passage of cold fronts across theregion.

These same southwesterly airstreams gener-ate CTWs on the southern coast; an analysisof the data and the dynamics of the region

t s a 4

Baines: The physical oceanography of Austral ian waters-a review 1 6 5

shows that these CTWs split into two whenthey encounter Bass Strait, The first part passesthrough Bass Strait in the form of a specialCTW termed a Kelvin wave, and the remain-der passes down the west side of Tasmania tothe southern extremity where it disappears,presumably because the bend in the coastalwaveguide is too sharp to be negotiated bythe waves. The flow through Bass Strait isassociated with these Kelvin waves; aboutthree quarters of this flux is due to CTWsgenerated west of Bass Strait, and aboutone quarter is due to Kelvin waves generatedinside it.

The water in these wintertime surges leavesBass Strait in the form of a siant underwaterwaterfall (Godfrey etal, 19801Tomczak 1985;which descends to 400 m; the water then movesnorthward into the Tasman Sea.

This completes our circuit around the con-tinent. There is much that we still don't knowand another review in l0 to 15 years timemay well highlight a completely different rangeof subjects, or some of those only touched onnere.

ReferencesBaines, P.G.

,l981. Satollite observations of internal waves

on the Australian Northwest shelf. Aust. J. mar.Freshwat. Res.. 32. 457-63.

Church, J.A. and Freeland, H.J. 1987. The energy sourcefor the coastal-trapped waves in the Australian coastalexperiment region. J. Phys. Oceanogr., 17,289-300.

Cresswell, G.R. and Golding, T.J. 1980 Observations ofa south-ffowing current in the southeastern IndianOcean. Deep Sea Res., 27A,449-66.

Cresswell, G.R. and Legeckis, R. 1986. Eddies off south-eastern Australia. Deep Sea Res., 33, 1527-62.

Easton, A.K. 1970. The Tides of the Cont inent of Aus-Lralia. Horace Lamb Centre Research paper No. 37,Flinders University of South Australia, 326 pp.

Flinders, M. l814. A Voyage to Terra Australis. Yol. 2G. & W. Nicol , London, 613 pp.

Freeland, H.J., Boland, F.M., Church, J.A., Clarke, A.J.,Forbes, A.M.G., Huyer, A., Smith, R.L., Thompson,R.O.R.Y. and White, N.J. 1988. The Australian coastalexperiment: a search for coastal trapped waves. .I.Phys. Oceanogr., 1 6, 1230-49.

Godfrey, J.S., Jones, I.S.F., Maxwell, J,G.H. and ScottB.D. 1980. On the winter cascade from Bass Straitinto the Tasman Sea. Aust. J. mar. Freshwat. Res..3 I . 275-86.

Godfrey, J.S. and Golding, T.J. 1981. The Sverdrup rela-tion in the Indian Ocean, and the Effect of Pacific-Indian Ocean throughflow on Indian Ocean Circula-tion and on the East Australian Current. J. Phys.Ocianogr., l l ,77l-9.

GriffHn, D.A., Middleton, J.H. and Bode, L. 1987. Thetidal and longer-period circulation of Capricornia,Southern Great Barrier Reef. Aust. J. mar. Freshwat.Res., 38,461-74.

Griffiths, R.W. and Pierce, A.F. 1985. Instability and eddypairs on the Leeuwin current south of Australia. DeepSea Res.. 32, l5ll-34.

Hamon, B.V. 1962. The spectrum of mean sea level atSydney, Coff's Harbour and Lord Howe Island. .I.geophys. Res,,67,5147-55. (Correction, 1963, J. geo-phys. Res., 68 (15), 4635.)

Hamon, B.V. 1966. Continental shelf waves and the ef-fects of atmospheric pressure and wind stress on sealevel. "/. geophys. Res., 7 I, 2883-93.

Holloway, P.E. 1983. Tides on the Australian northwestshelf . Aust. J. mar. Freshwat. Res., 34,213-30.

Middleton, J.H,, Buchwald, V.T. and Huthnance, J.M.1984. The anomalous tides near Broad Sound. Corr.Shelf Res., J, 359-81.

Nunes, R.A. and Lennon, G.W. 1986. Physical propertydistributions and seasonal trends in Spencer Gulf, SouthAustralia: an inverse estuary, Aust. J, mar. Freshwat.Res., 37,39-53.

Schwiderski, E.W. 1979. Global ocean tides, Part II: Thesemidiurnal principal lunar tide (Mr), Atlas of tidalcharts and maps. Rep. No. NSIIC TR, Naval SurfaceWeapons Center, KO5 Dahlgren, Virginia, USA, 79-4 t4 .

Tomczak Jr, M. 1985. The Bass Strait water cascadeduring winter 1981. Cont. Shelf Res., 4,255-78.

Wolanski, E., Imberger, J. and Heron, M. 1984. Islandwakes in shallow coastal waters. ,I. geophys. Res., 89,10553-69.

Wolanski, E. and Hamner, W.M. 1988. Topographicallycontrolled fronts in the ocean and their biologicalinfluence. Science, 241, l'77-81.