Upload
others
View
5
Download
0
Embed Size (px)
Citation preview
!
!
"##$% "#&
$% "#'
$%
()$*
("$*
(+$*
(($*
(#$*
(,$*
(&$*
(-$*
('$* !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*[email protected]
B1399
I.Introduc@on
IV.Spa@alStructureofDivergentEddyHeatFluxes V.Ver@calStructure
VI.TemporalVariability VII.Summary
III.EddyHeatFluxes:[email protected]
€
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)