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The strengthening East Australian Current, its eddies and biological effects - an introduction and overview

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Suthers, IM and Young, JW and Baird, ME and Roughan, M and Everett, JD and Brassington, GB and Byrne, M and Condie, SA and Hartog, JR and Hassler, CS and Hobday, AJ and Holbrook, NJ and Malcolm, HA and Oke, PR and Thompson, PA and Ridgway, K, The strengthening East Australian Current, its eddies and biological effects - an introduction and overview, Deep-Sea Research II, 58, (5) pp. 538-546. ISSN 0967-0645 (2011) [Refereed Article]


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DOI: doi:10.1016/j.dsr2.2010.09.029

Abstract

The polewardflowingEastAustralianCurrent(EAC)ischaracterisedbyitsseparationfromthecoast, 100–200nauticalmilesnorthofSydney,toformtheeastwardflowingTasmanFrontandasouthward flowingeddyfield.Theseparationzonegreatlyinfluencescoastalecosystemsfortherelativelynarrow continentalshelf(only15–50kmwide),particularlybetween32–341S. Inthisregionthecontinental shelfhasamarkedshiftintheseasonaltemperature-salinityrelationshipandelevatedsurfacenitrate concentrations.ThiscurrentparallelstheportionofthecoastwhereAustralia’spopulationis concentratedandhasalonghistoryofscientificresearch.However,understandingofphysicaland biologicalprocessesdrivenbytheEAC,particularlyinlinkingcirculationtoecosystems,islimited.In this specialissueof16papersontheEAC,weexaminetheeffectsofclimaticwind-stressforcedocean dynamicsonEACtransportvariabilityandcoastalsealevel,fromENSOtomulti-decadaltimescales; eddy formationandstructure;finescaleconnectivityandlarvalretention.Comparisonswiththe poleward-flowingLeeuwinCurrentonAustralia’swestcoastshowdifferencesinecosystem productivitythatcanbeattributedtotheunderlyingphysicsineachregion.Onaveragethereis double thechlorophyll a concentrationontheeastcoastthanthewest.IncomparisontotheLeeuwin, the EACmayhavelesslocalretentionoflarvaeandactasapartialbarriertoonshoretransport,which may alsoberelatedtothelocalspawningandearlylifehistoryofsmallpelagicfishoneachcoast.Inter- annualvariationsintheEACtransportproduceadetectablesea-levelsignalinSydneyHarbour,which could provideausefulfisheriesindexasdoestheFremantlesealevelandLeeuwinCurrentrelationship. The EAC’seddystructureandformationbytheEACareexamined.Aparticularcold-coreeddyisshown to havea‘‘tilt’’towardsthecoast,andthatduringarotationtheflowofparticlesmayriseuptothe euphoticzoneandthendownbeneath.Inawarm-coreeddy,surfacefloodingisshowntoproducea new shallowersurfacemixedlayerandpromotealgalgrowth.Anassessmentofplanktondatafrom 1938–1942showedthatthelocal,synopticconditionshadtobeincorporatedbeforeanycomparison with thepresent.ThereareusefulrelationshipsofwatermasscharacteristicsintheTasmanSeaand separationzonewithlarvalfishdiversityandabundance,aswellaswithlong-linefisheries.These fisheries-pelagichabitatrelationshipsareinvaluableforfisheriesmanagement,aswellasforclimate changeassessments. There isfurtherneedtoexaminetheEACinfluenceonrainfall,stormactivity,dustdeposition,and on themovementsbyfish,sharksandwhales.TheAustralianIntegratedMarineObservingSystem (IMOS)hasprovidednewinfrastructuretodeterminethechangingbehaviouroftheEACandits bio-physicalinteractionwiththecoastsandestuaries.Theforecastingandhindcastingcapability developedundertheBluelinkprojecthasprovidedanewtoolfordatasynthesisanddynamical analysis.TheimpactofastrengtheningEACandhowitinfluencesthelivelihoodsofoverhalfthe Australianpopulation,fromBrisbanetoSydney,HobartandMelbourne,isjustbeingrealised.

Item Details

Item Type:Refereed Article
Keywords:East Australian Current, Leewin Current, Separation zone, Tasman Front, Eddy, Climatology, Bluelink
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Physical Oceanography
Objective Division:Environment
Objective Group:Ecosystem Assessment and Management
Objective Field:Ecosystem Assessment and Management of Marine Environments
Author:Holbrook, NJ (Professor Neil Holbrook)
ID Code:69634
Year Published:2011
Web of Science® Times Cited:79
Deposited By:Geography and Environmental Studies
Deposited On:2011-05-09
Last Modified:2017-12-07
Downloads:7 View Download Statistics

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