Climateresponsetochangesinthe
meridionalenergytransport:
roleofoceandynamics
FrancisCodron
LOCEAN/IPSL,UPMC,Paris
Introduc8on
Responseofatmosphericcircula8onandITCZto
inter-hemisphericenergyimbalance(Kang,2009)
Kang(2008,09),Frierson(2012,13),L’Héveder(2015),
Donohue(2013,14),TRACMIPproject…
Allthesestudiesusea«slab»ocean...
Butenergytransportsbyatmosphereandoceanarenotindependent
Tropics:
Shallowcircula8oncells
•  Drivenbytradewinds/
Ekmantransport
•  Masstransport=Hadley
cells
•  Transportenergypoleward
(Schneideretal,2014)
Ekmanheattransportforslabocean
(Codron2012,Clim.Dyn)
Momentumbalance,surfacemixedlayer:
Ver8calintegra8on(ignoringpressuregradient)
Wind-drivenhorizontalmassfluxes:
(ε<<fexceptneartheequator)
1.5-Layerscheme
SlabtemperatureTs,returnflowatTd
Deeptemperature:
y
2-layerscheme
2slablayers,prognos8ctemperaturesTsandTd
• 
Surfaceheatfluxesgointhesurfacelayer
•  Convec8veadjustment
Implementa8on
•  LMDZAGCM,96x96gridpoints,39levels
•  Ocean-planetgeometry,noseaice
•  Obliquity(seasons),noeccentricity
•  Ekmantransportandhorizontaldiffusion(constantK)
•  Noaddi8onalheatflux(Q-flux=0)
Meannorthwardenergytransportbytheocean
4
3
2
total
Ekman
diffusion
PW
1
0
−1
−2
−3
−4
−80 −60 −40 −20
0
20
latitude
40
60
80
•  Ekman:polewardtransportintheTropics,
weakerequatorwardinmid-la8tudes
•  DiffusionwherelargeTemperaturegradients
Annualcycle:SSTandprecipita8on
40
latitude
20
0
−20
−40
J
F
M
15
A
M
20
J
J
month
A
25
S
O
N
30
StrongSST/surfacewind/ITCZ
meridionalcouplingneartheequator
D
Sensi8vityexperiments:
add1PWnorthwardtransportbetween40°Sand40°S
(asaddi8onalprescribedQ-fluxintheslab)
1.  Interac8veEkmananddiffusivetransports
2.  Ekmananddiffusionprescribedascontrolseasonalcycle
DifferenceofnorthwardenergytransportbyOceanandAtmosphere
•  FixedEkman/diffusion
•  Interac8veEkman/diffusion
2
PW
1
0
−1
−2
−3
ocean
atmos
−50
0
latitude
50
Ø  Largedifferencesbetweenfixed/intercases(esp.Tropics)
Ø  Goodcompensa8onbetweenoceanandatmosphere
00
00
fixed OHT
200
200
200
400
400
400
600600
600
800800
800
1000
−80 −60 −40 −20
0
20 40 60
−80 −60 −40 −20
latitude
−160 −120 −80
−40
80
0
latitude
0
Zonalwind
interactive
fixed OHTOHT
fixed OHT
interactive OHT
pressure (hPa)
00
fixed OHT
pressure (hPa)
00
MeridionalStreamfuncJon(109kg/s)
pressure (hPa)
00
Atmosphericcircula8onresponse,fixedOHTcase
interactive O
200
200
200
200
400
400
400
400
600
600
600
600
800
800
800
800
1000
1000
1000
1000
1000
1000 020 20
40
60
80
−80 −60 −40 −20
0
2
−80−80
−60−60
−40 −40
−20 −200 −80
40
60
80
−80
20 40 60 80
−80 −60
−60 −40
−40 −20
−20 0 0 2020 4040 6060 80 80
latitude
latitude
latitude
40
latitude
latitude
80
120
160
−160 −120 −80
−40
0
−10
40
80
−5
120
160
0
−10
5
−5
10
0
Ø  Northwardjetshims
Ø  Cross-equatorialHadleycell&oppositetradewindchanges
5
fixed OHT
interactive OHT
Oceanheattransport:
Tropics(off-equator)
200
400
600
800
1000
60 −40 −20
0
20
latitude
40
60
80
−80 −60 −40 −20
PW
Tradewindchangesdrive
southwardtransport
−10
−5
0
Ø  Strongcompensa8on
0
20
latitude
40
60
2
15
10
0
−1
−2
−3
ocean
atmos
−50
0
latitude
50
80
fixed OHT
interactive OHT
Oceanheattransport:
Equator
200
400
600
800
1000
0
20
latitude
40
60
Cross-equatorialcell:
Northwardtransport
Ø  Posi8vefeedback
−160 −120 −80
−40
80
−80 −60 −40 −20
2
0
20
latitude
40
60
1
0
40 0 80
PW
0 −60 −40 −20
120
160
−1
−2
−3
ocean
atmos
−50
0
latitude
50
80
2
•  Confinedtoequator
•  Moreintense
1
PW
Hadleycellresponsewith
interac8veOHT:
0
−1
ocean
−2
atmos
−3
−50
pressure (hPa)
fixed OHT
200
400
400
600
600
800
800
1000
1000
0
20
latitude
50
interactive OHT
200
−80 −60 −40 −20
0
latitude
40
−160 −120 −80
60
80
−40
0
−80 −60 −40 −20
40
80
120
160
0
20
latitude
40
60
80
Precipita8onresponse:
•  Medianshimsto7.5°inbothcases..
•  Butverydifferentstructures
•  Stormtracksshimnorthward
20
precip (mm/day)
Control
15
Fixed OHT
Inter OHT
10
5
0
−80 −60 −40 −20
0 20
latitude
40
60
80
Summary-Conclusion
•  AddingEkmanheattransportsignificantlychanges
theresponsetoaprescribedenergyimbalance
•  Atmosphericcircula8onmuchweakerintheTropics
(exceptattheequator?)
•  Energytransportsbytheatmosphereandocean:
solu8ontoacoupledproblem?
PresentEarth
Annual-meanSSTandsea-ice
latitude
60
Meanseasonalcycle:
40
Precipita8onand
northwardenergytransport
20
bytheatmosphere
0
Energyfluxequator
Inred
−20
−40
−60
J
F
−10
M
A
−5
M
J
J
month
0
A
S
5
O
N
10
D