!

!

"##$% "#&

$% "#'

$%

()$*

("$*

(+$*

(($*

(#$*

(,$*

(&$*

(-$*

('$* !0Cp

! !H1

!H2v "T "dyn

dz

"

+ ( #

,

!./0!

.1")&0!23!4

!"5

!,))

!#))

!())

!+))

!"))

)

"))

+))

())

#))

,))

!-,) !,)) !+,) ) +,) ,)) -,)

)

+))

#))

&))

'))

")))

"+))

"#))

"&))

6789:!245

!0Cp(u"b tT

")n [kW m!2]

!

!!.;0!

!!!<!"##)!4+!=!"!

!!!<!"'#+!4+!=!"!

!!!<!+(-'!4+!=!"!

!!!<!!"',+!4+!=!"!

!!!<!!"'"#!4+!=!"!

"

+

(

#

,

DivergentEddyHeatFluxesintheKuroshioExtensionat143o‐149oEStuartP.Bishop*,D.RandolphWa7s,KathleenA.Donohue

GraduateSchoolofOceanography,UniversityofRhodeIsland,215SouthFerryRoad,Narraganse@,RI02882*sbishop@gso.uri.edu

B1399

I.Introduc@on

IV.Spa@alStructureofDivergentEddyHeatFluxes V.Ver@calStructure

VI.TemporalVariability VII.Summary

III.EddyHeatFluxes:Rota@onalvs.DivergentII.EddyHeatFlux

€

ρ0Cp ′ u ′ T = ρ0Cp ′ u bc ′ T + ρ0Cp ′ u bt ′ T

KuroshioExtensionSystemStudy(KESS)

€

u = ubc + ubt

CPIESAbsoluteGeostrophicCurrents

• Mesoscale‐resolvingarrayof46currentandpressureequippedinvertedechosounders(CPIES).• LocatedeastofJapaninregionofhighestEKE.• Provides3‐Dmapsofgeostrophicvelocityandtemperaturefor16months(Donohueetal.2010)1.• ThisposterpresentseddyheatfluxesZmatesfromtheKESSobservaZons.

Longitude [°E]

La

titu

de

[°N

]

135 140 145 15029

30

31

32

33

34

35

36

37

38

39

40m

ete

rs

!10000

!9000

!8000

!7000

!6000

!5000

!4000

!3000

!2000

!1000

0

16 Month

La

titu

de

[°N

]

Longitude [°E]

250x106 W m

!1

a)

144 146 14830

32

34

36

38

Stable

Vertically!Integrated Eddy Heat Flux

b)

144 146 148

Unstable

c)

144 146 148

!0.1 !0.05 0 0.05 0.1

PW

Poleward Eddy Heat Transport

d)

16 Month

Stable

Unstable

!500 0 500

(x106) W m

!1

La

titu

de

[°N

]

500 kW m!2

(a) 400 m

Full

!0Cpu!T !

144 146 14830

32

34

36

38

T!2

["C

2]

5

10

15

20 (b)

Rotational

!0Cpu!

b cT!

144 146 14830

32

34

36

38 (c)

Dynamic

!0Cpu!

b tT!

144 146 14830

32

34

36

38

Longitude [°C]

La

titu

de

[°N

]

20 kW m!2

(d) 1500 m

Full

144 146 14830

32

34

36

38

T!2

["C

2]

0

0.02

0.04

0.06

0.08 (e)

Rotational

144 146 14830

32

34

36

38 (f)

Dynamic

144 146 14830

32

34

36

38

Longitude [°E]

La

titu

de

[°E

]

558

(a)

0.5 m s!1

°C

144 146 14830

32

34

36

38

563

(b)

568

(c)

573

(d)

!0.06 0 0.06

dbar

CurrentandPressureEquippedInvertedEchoSounders(CPIES)

KESS

Mo@va@on

Overview

€

ψ−

€

ψ+

€

ubc

€

ubt

€

u

• Eddy‐meanflowinteracZons:1.  EddiesreleasemeanpotenZalenergy

ofbaroclinicjet.2.  Eddiesactasaneddyforceonthe

meanflow.

!"# $## $"# %## %"# &## &"# "## ""# '## '"#!!"#

!!##

!"#

#

"#

!##

!"#

()*+,-*.,/$##&0

/1!#$0,23,4

!$

,

,,/50,&##,4,

!0Cpn̂ · u!b tT

!

!

$

%

&

"

'

6

789:;<=>),?°@A

7*<;<=>),?°BA

"##,23,4!$

,/>0,!"$!%##,

!

$ % &

"

'6

,C<*DE),

!&& !&' !&F%#

%!

%$

%%

%&

%"

%'

%6

%F

789:;<=>),?°@A

,/)0,%$"!&##,

,G;9:,H8+4*<;89,

!&& !&' !&F,

,

,

,

,

,

,

,

,

789:;<=>),?°@A

,/I0,&$"!""#,

,G;9:!J)<,K9<)+*5<;89,

!&& !&' !&F,

,

,

,

,

,

,

,

,

789:;<=>),?°@A

,/:0,""#!"F#,

,-))L,@>>;)M,

!&& !&' !&F,

,

,

,

,

,

,

,

,

!$N" !$N# !!N" !!N# !#N" ,,#, ,#N" ,!N# ,!N" ,$N#/1!#

%0,23,4

!$

,C<*DE),,/*0,

7*<;<=>),?°BA

, , ,

%#

%"

&#

,O9M<*DE),,/D0,

789:;<=>),?°@A

7*<;<=>),?°BA

!&# !"# !'#

%#

%"

&#

€

Qdyn = ρ0Cp ′ u bt ′ T dz∫Ver@cally‐IntegratedEddyHeatFlux

a)  16month:asymmetryalongmeanpath‐Down‐gradientupstreamoftrough‐Up‐gradientdownstreamoftrough

b)  “Stable”regime:1st6months–mostlydown‐gradient.

c)  “Unstable”regime:10months–similarto16monthmeanwithasymmetryalongmeanpath.

PolewardEddyHeatTransportd)Peaksnear35oNat~0.04PW

Parameteriza@on

€

ˆ n ⋅ ′ u bt ′ T = −κ∂T ∂n

kWm‐2

Cross‐streameddyheatfluxprofiles

Weaklydepth‐dependentreferencecurrentsdrivedivergentfluxes

•  Down‐gradientparameterizaZongoodupstreamoftrough.

•  κranges1000‐3000m2s‐1

•  ParameterizaZondoesn’taccountforup‐gradientfluxesdownstreamoftrough.ObservaZons

ParameterizaZon

Ver@calStructure•  VerZcally‐coherentcross‐stream

fluxespeak200‐500m,mid‐thermocline.

•  Peakfluxesareinexcessof±500kWm‐2.

!

!

"##$% "#&

$% "#'

$%

()$*

("$*

(+$*

(($*

(#$*

(,$*

(&$*

(-$*

('$* !0Cp

! !H1

!H2v "T "dyn

dz

"

+ ( #

,

!./0!

.1")&0!23!4

!"5

!,))

!#))

!())

!+))

!"))

)

"))

+))

())

#))

,))

!-,) !,)) !+,) ) +,) ,)) -,)

)

+))

#))

&))

'))

")))

"+))

"#))

"&))

6789:!245

!0Cp(u"b tT

")n [kW m!2]

!

!!.;0!

!!!<!"##)!4+!=!"!

!!!<!"'#+!4+!=!"!

!!!<!+(-'!4+!=!"!

!!!<!!"',+!4+!=!"!

!!!<!!"'"#!4+!=!"!

"

+

(

#

,

€

ˆ n = − ∇T ∇T

€

ˆ n

€

ˆ s

TimeSeriesat400ma)  EpisodicZmeseriesb)  Days152‐300–1st6months“Stable”regime:‐  Dominatedby10‐15daylow‐amplitude

eastwardpropagaZngbaroclinicwaves.‐  Heatfluxesareweakanddown‐gradient.c)  Days325‐400–Cold‐CoreRingFormaZon:‐  Strongdown‐gradientfluxesdirectlyupstream

ofwheretheringformed.‐  Up‐gradientfluxeswithinwheretheringformed

anddownstream.d)  Days425‐550–Cold‐CoreRing/JetInteracZon:‐  SimilarspaZalstructuretocold‐corering

formaZone)  Days550‐580–Remotely‐generatedabyssal

eddy/jetinteracZoninabsenceofrings:‐  Strongdown‐gradientfluxes35oN145oE.‐  Weakup‐gradientfluxesdownstream.

150 200 250 300 350 400 450 500 550 600 650!150

!100

!50

0

50

100

150

Year Day (2004)

(x1

02)

kW

m!

2

(a) 400 m

!0Cpn̂ · u!

b tT!

1

2

3

4

5

6

7

La

titu

de

[°N

]

Longitude [°E]

500 kW m!2

(b) 152!300

1

2 3 4

5

67

Stable

144 146 14830

32

34

36

38 (c) 325!400

Ring Formation

144 146 148

(d) 425!550

Ring!Jet Interaction

144 146 148

(f) 550!580

Isolated Deep Eddies

144 146 148

!2.5 !2.0 !1.5 !1.0 !0.5 0 0.5 1.0 1.5 2.0(x10

3) kW m

!2

€

ρ0Cp ˆ n ⋅ ′ u bt ′ T Presenceofremotely‐generateddeepeddies

RegimeShiZ

TheKuroshioExtensionexhibitsdecadalvariabilitywithin1000kmofJapancoast(QiuandChen2005)4.

•  Jetaxis:Thickblackcontour

•  30‐60dayband‐passfiltereduppergeopotenZalheightanomaly(CI=1cm):

‐  Darkgray:posiZve‐  Lightgray:negaZve•  30‐60dayband‐

passfilteredbo@ompressureanomaly:colorcontour.

•  Eddyheatfluxvectorsat400m.

FigureLegend

ExternalDeepCyclone‐Jet:Interac@onandHeatFlux

a)  Deepcyclonebeginscrossingjet.b)  Polewardheatfluxassociatedwithjoint‐developmentbetweendeepcyclone

anduppergeopotenZalheightanomaly.c)  Strongpolewardheatflux.‐  JointdevelopmentbetweenupperanddeepconZnues.‐  Axisofjetsteepensintoatrough.d)  Jointdevelopmentreachesamaximumasdeepcyclonepassesalmost

completelysouthofjet.

•  Theeddyheatfluxisthedepth‐averageddensity,ρ0,Zmesthespecificheatatconstantpressure,Cp,ZmesthetemporalcorrelaZonbetweenthegeostrophiccurrents,u,andthetemperaturefield,T:

€

ρ0Cp ′ u ′ T

CPIESMappedEddyHeatFlux

1)  DivergenteddyheatfluxesintheKuroshioExtensionaredrivenbyweaklydepth‐dependentcurrents.

2)  16monthmeandivergentfluxeschangealongstreamfromdown‐gradienttoup‐gradientatthemeantrough.

3)  FluxesareverZcallycoherentwithextremaexceeding500kWm‐2between200‐500m.

4)  ThemeanspaZalstructurearosefromepisodicmesoscalephenomena:cold‐coreringformaZon,ring‐jetinteracZon,andremotely‐generateddeepeddy‐jetinteracZons.

•  AbsolutegeostrophiccurrentsarethevectorsumbetweenaverZcallyalignedcurrentinthermal‐windbalancecalledthebarocliniccurrent,ubc,andaweaklydepth‐dependentreferencecurrentcalledthebarotropiccurrent,ubt,measuredat5300m.

€

′ u bc ′ T ∝ ˆ k ×∇ ′ T 2

Rota@onalFluxes•  ThebarocliniccomponentiscompletelyrotaZonal

(nondivergent)(MarshallandShu@s1981)2:

UpperOceanat400m(a‐c)•  Totalfluxes(a)are~2000kWm‐2andcomparabletothe

GulfStream(CroninandWa@s1996)3.•  RotaZonalfluxes(b)dominatethetotalfluxes(a),follow

temperaturevariancecontours,andmaskthedivergentfluxes(c)whichare<25%aslarge.

•  Thedivergentcomponent(c)crossesthefront.

SubthermoclineOceanat1500m(d‐f)•  Totalfluxes(d)haveequalcontribuZonfromrotaZonal

(e)anddivergent(f)fluxes.•  RotaZonalfluxes(e)diminishwithdepth.

•  Divergentfluxesaredrivenbytheweaklydepth‐dependentreferencecurrents.

VIII.ReferencesandAcknowledgements1.  Donohue,K.A.,D.R.Wa@s,K.Tracey,A.D.Greene,andM.Kennelly,2010.MappingcirculaZonintheKurohsioExtension

withanarrayofCurrentandPressurerecordingInvertedEchoSounders.J.Atmos.OceanicTechnol.,27:507‐527.2.  Marshall,J.,andG.Shu@s,1981.AnoteonrotaZonalanddivergenteddyfluxes.J.Phys.Oceanogr.,11,1677‐1680.3.  Cronin,M.,andD.R.Wa@s,1996.Eddy‐meanflowinteracZonsintheGulfStreamat68oW.PartI:EddyEnergeZcs.J.

Phys.Oceanogr.,26,2107‐2131.4.  Qiu,B.,andS.Chen,2005.VariabilityoftheKuroshioExtensionjet,recirculaZongyreandmesoscaleeddiesondecadal

Zmescales.J.Phys.Oceanogr.,35,2090‐2103.

ThisworkwassupportedunderNSFgrantsOCE‐0221008andOCE‐0851246

TheKuroshioExtensiondiffersfromtheGulfStreaminthatithasashallowerthermoclineanditflowsoveramuchdeepersubthermoclinelayer.Asaresult,meandergrowththroughselfdevelopmentthathasbeenobservedintheGulfStreamisnotaseffecZveintheKuroshioextension.Instead,meandergrowthanddecayprocessesaredrivenbyexternalmesoscaleperturbaZons.Thelargestdown‐andup‐gradienteddyheatfluxesaredrivenbyremotely‐generateddeepeddiesandringinteracZonswiththeKuroshioExtension.

(0.5ms‐1oC=2055kWm‐2)