the problem: what sets the size of the...
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![Page 1: The problem: what sets the size of the ACC?pordlabs.ucsd.edu/wryoung/theorySeminar/pdf16/Pres3_Masich.pdfMcWilliams et al., 1978: A 2-layer, eddy-resolving QG model of the ACC with](https://reader033.vdocument.in/reader033/viewer/2022053020/5f2bc238b8939f5a8d58080f/html5/thumbnails/1.jpg)
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Theproblem:whatsetsthesizeoftheACC?Stommel1957,1962:EarlymodelsadaptSverdrupdynamicstotheACC,relaEngwindstresscurltotransport.MunkandPalmen,1951:Suchmodelsrequire‘uncomfortablylarge’valuesofeddyfricEoncoefficientstolimittheACCtransporttoreasonablevalues.Gill1968:LinearmodeloftheACCrequiresaboRomfricEoncoefficentof103cm2/salateralfricEoncoefficientof108cm2/s.
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Theproblem:whatsetsthesizeoftheACC?Stommel1957,1962:EarlymodelsadaptSverdrupdynamicstotheACC,relaEngwindstresscurltotransport.MunkandPalmen,1951:Suchmodelsrequire‘uncomfortablylarge’valuesofeddyfricEoncoefficientstolimittheACCtransporttoreasonablevalues.Gill1968:LinearmodeloftheACCrequiresaboRomfricEoncoefficentof103cm2/salateralfricEoncoefficientof108cm2/s.Evenworse:howbig*is*theACC?ReidandNowlin,1971:Eastwardtransportof237SvthroughtheDrakePassageFoster,1972:Westwardtransportof15SvthroughtheDrakePassage(backwards!)InternaEonalSouthernOceanStudies(ISOS)programmeasuresDrakePassagetransport,structure,dynamics.NowlinandKlinck,1986:134Sv+-10%(eastward),withEmevariabilityof20%.
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NowlinandKlinck,1986:134Sv+-10%(eastward),withEmevariabilityof20%.
ACCcharacterisEcs:- NOTanarrowjetorboundary
currentwithwithRo
- ThreenarrowfrontalregionsofwidthtwoorthreeEmestheRossbyradius
- ThecurrentpenetratesdowntotheboRomofthewatercolumn,withsubstanEalmeridionaldensitygradientsatdepth.
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McWilliamsetal.,1978:A2-layer,eddy-resolvingQGmodeloftheACCwithvariousconfiguraEonsoftopographyandwindforcing.Inallmodelruns,eddiesplayedakeyroleintransporEngzonalmomentumdownward.Inmodelrunswithouttopography,fricEonwasonlystrongenoughtoholdmodeltransportvaluesaround400-600Sv.Inmodelrunswithtopography,topographicformdragwasstrongenoughtolimitthemodeltransportto100Sv.BoRomandsidewallfricEonisnotenough!Thus:
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Steadystatezonalmomentumbalance:
NoEngthat:
Wecanwriteeqn(1)as
and
(eqn1)
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TakingtheverEcalintegral:
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TakingtheverEcalintegral:
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InthecircumpolarregionoftheSouthernOcean,integratedzonalmomentumbalancebecomes:
Momentumsource:FricEonalwindstressatthesurfaceofthefluid
SOSE mean τx [N/m2]!
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InthecircumpolarregionoftheSouthernOcean,integratedzonalmomentumbalancebecomes:
Momentumsource:FricEonalwindstressatthesurfaceofthefluidPotenEalmomentumsinks:1) FricEonalstressattheboRom;
SOSE mean τx [N/m2]!
![Page 11: The problem: what sets the size of the ACC?pordlabs.ucsd.edu/wryoung/theorySeminar/pdf16/Pres3_Masich.pdfMcWilliams et al., 1978: A 2-layer, eddy-resolving QG model of the ACC with](https://reader033.vdocument.in/reader033/viewer/2022053020/5f2bc238b8939f5a8d58080f/html5/thumbnails/11.jpg)
InthecircumpolarregionoftheSouthernOcean,integratedzonalmomentumbalancebecomes:
Momentumsource:FricEonalwindstressatthesurfaceofthefluidPotenEalmomentumsinks:1) FricEonalstressattheboRom;2) FricEonalstressatthesidewalls,viameridionalmomentumfluxdivergence;
SOSE mean τx [N/m2]!
![Page 12: The problem: what sets the size of the ACC?pordlabs.ucsd.edu/wryoung/theorySeminar/pdf16/Pres3_Masich.pdfMcWilliams et al., 1978: A 2-layer, eddy-resolving QG model of the ACC with](https://reader033.vdocument.in/reader033/viewer/2022053020/5f2bc238b8939f5a8d58080f/html5/thumbnails/12.jpg)
InthecircumpolarregionoftheSouthernOcean,integratedzonalmomentumbalancebecomes:
Momentumsource:FricEonalwindstressatthesurfaceofthefluidPotenEalmomentumsinks:1) FricEonalstressattheboRom;2) FricEonalstressatthesidewalls,viameridionalmomentumfluxdivergence;or3) Topographicformstress.
SOSE mean τx [N/m2]!
![Page 13: The problem: what sets the size of the ACC?pordlabs.ucsd.edu/wryoung/theorySeminar/pdf16/Pres3_Masich.pdfMcWilliams et al., 1978: A 2-layer, eddy-resolving QG model of the ACC with](https://reader033.vdocument.in/reader033/viewer/2022053020/5f2bc238b8939f5a8d58080f/html5/thumbnails/13.jpg)
Topographicformstress
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Howdoesmomentumtravelfromsurfacesourcetoseafloorsink?Interfacialformstress.
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Howdoesmomentumtravelfromsurfacesourcetoseafloorsink?Interfacialformstress.
geostrophycontinuous stratification
and
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Interfacialformstress:
VerEcalfluxofeastwardmomentumisproporEonaltoeddyheatflux.
Polewardheatfluxcorrespondstothedownwardfluxofeastward
momentum.
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Givenafewnumbers…….thismodelcanbetestedobservaEonally.
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1977DrakeClusterArrayFDRAKE75Mooring8
FDRAKE75Mooring10
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ObservaEonsusedtotest
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SOLIDLINE
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Secondtest:Candown-gradienteddyheatfluxbeparameterizedintermsofEme-averagedbaroclinicfieldsalaGreen(1970)andStone(1972)?
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ObservaEonsusedtotest
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SOLIDLINE
DOTTEDLINE
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EsEmaEngtransport
SOLIDLINE
DOTTEDLINE
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EsEmaEngtransport:
=
SeqngeddyheatfluxesEmatesequaltoeachother:
AllowsustocalculateEmeaveragedACCverEcalshear:
FromwhichwecanesEmateanACCtransport:
.
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Fordiscussion:theauthorsassumethattheRHSisjustasevenlydistributedastheLHS.IsthisareasonableassumpEon?
EKEfromsurfacealEmetry,2003-2013.Sheenetal.,2014.
Windstress(N/m2)fromNCEPreanalysis,1980-2000.MarshallandSpeer,2012.
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ZoomintoDrakePassage:cDrakeExperiment,2007-2011.
1977DrakeClusterArrayFDRAKE75Mooring8
FDRAKE75Mooring10
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Pressure (dbar)!
cDrakespaEalandtemporalvariability.
VerEcal,EmemeanIFS. TimemeanIFSprofiles.