Volcanic source of decadal predictability in the north atlantic
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Volcanic source of decadal predictability in the North Atlantic. Didier Swingedouw, Juliette Mignot, Sonia Labetoulle , Eric Guilyardi, Gurvan Madec. DJF SST in GIN Seas ( HadISST ). A 20-yr cycle in the North Atlantic?. Swingedouw et al., in rev .

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Volcanic source of decadal predictability in the North Atlantic

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Volcanic source of decadal predictability in the north atlantic

Volcanicsourceofdecadalpredictabilityin the NorthAtlantic

Didier Swingedouw, Juliette Mignot, Sonia Labetoulle, Eric Guilyardi, Gurvan Madec


Volcanic source of decadal predictability in the north atlantic

DJF SST in GIN Seas (HadISST)

A 20-yr cycle in the North Atlantic?

Swingedouw et al., in rev.


Volcanic source of decadal predictability in the north atlantic

A 20-yr cycle in the North Atlantic?

Chylek et al. 2011


Volcanic source of decadal predictability in the north atlantic

A 20-yr cycle in the North Atlantic?

April seaiceedge in the NordicSeas

Divine et al. 2006

Sicre et al. 2008


Volcanic source of decadal predictability in the north atlantic

20-yr cycle in IPSLCM5

10

yrs

Seaicecover -,

SLP-

negativedelayedfeeedback

EGC +

5yrs

3yrs

convection +

T,’ S’ +

2yrs

9yrs

AMOC +

Escudier et al., in rev.


Advection as in great salinity anomalies

Advection as in Great Salinity Anomalies


How can we intialize this 20 yr cycle in the model

How canweintializethis 20-yr cycle in the model?


Experimental d esign

Experimentaldesign

  • 5-member historical ensemble withnatural and antrhopogenicradiatiuve forcing

  • 5-member initialised ensemble nudgedwith SST anomalies (Reynolds et al. 2007) superimposed on eachhistorical simulation over the period 1949-2005:

  • 3-member hindcast ensemble every 5 years (with white noise on SST) and forecast or projection ensemble

  • 3-member ensemble withonlynatural and anthropogenic forcing

Agung

Pinatubo

El Chichon


Amoc initialisation

AMOC Initialisation

Reconstruction

Obs. (Huck et

Nudged

  • Reconstructions of the AMOC using NODC hydrographic data (Huck et al. 2008) and Latif et al. (2003)

  • Agreement betweennudged and reconstructions

  • Synchronisation also in the historical simulations

Historical

Control


Cv sites response

CV sites response

  • Convection sites explain AMOC variations


Mechanisms

Mechanisms

  • Agung eruption 1963-1966

  • GIN SST and sea-icecover

  • Wind stress & EGC

  • SSS Labrador Sea

  • CV sites

  • AMOC

  • Phasing of the second maximum

GSA

GSA

GSA

  • Labrador Sea SSS = 7-10 yearspredictor of the AMOC

  • EGC = more than 10 yearspredictor


Volcanic source of decadal predictability in the north atlantic

Initialisation du cycle à 20 ans

10

yrs

Seaicecover -,

SLP-

negativedelayedfeeedback

EGC +

5yrs

3yrs

convection +

T,’ S’ +

2yrs

Agung eruption

9yrs

AMOC +

Escudier et al. In rev.


A ttribution simulations

Attribution simulations

  • Agung eruption in 1963 resets the 20-yr cycle in natural simulations as in historicalones, not the case in anthropogenicones


Impact of volcanic forcing

Impact of volcanic forcing

Climatic index

Agung

Model free

15 yrs

Model free

Time

1963

1982

1991

2006


Impact of volcanic forcing1

Impact of volcanic forcing

Climatic index

Agung

El Chichon

Model free

15 yrs

Time

1963

1982

1991

2006


Impact of volcanic forcing2

Impact of volcanic forcing

Climatic index

Kanzow et al. 2010

Agung

El Chichon

Pinatubo

Model free

15 yrs

Destructive interference

Time

1963

1982

1991

2006


Impact of volcanic forcing3

Impact of volcanic forcing

Model free

Need of simulations withoutPinatubo to confirmthisidea


A simple physical model

A simple physical model

The purplecurveis a simple model of the 20-yr response to the 3 major volcanoes plus a weakening due to anthropogenic forcing:


Conclusions

Conclusions

  • A 20-yr favoredfrequency in the North Atlantic in IPSL-CM5: agreement with a few data

  • Simple initialisation technique succeeds in synchronizing the AMOC

  • Due to volcanictriggering of the 20-yr cycle

  • And the effect of the NAO in the 1980s and 1990s

  • Effect of Pinatubo: destructive interference?


Thank you

Thankyou

[email protected]

Photo by Bruno Ferron, OVIDE 2010


Hindcasts

Hindcasts

AMOC 48°N

  • Only one member of the nudged ensemble (planned to apply to each)

  • 3-member ensemble of free run

  • Good predictiveskill for the AMOC in perfect model analysis (Persechino et al., sub.)

  • 90’s max. missed


Hindcasts1

Hindcasts

AMOC 48°N

  • Only one member of the nudged ensemble (planned to apply to each)

  • 3-member ensemble of free run

  • Good predictiveskill for the AMOC in perfect model analysis (Persechino et al., sub.)

  • 90’s max. missed


Hindcasts2

Hindcasts

Hind.


Another ensemble

Another ensemble


Cv sites response in projections

CV sites response in projections


Escudier et al mechanism in projections

Escudier et al. mechanism in projections


Discussion iwi et al

Discussion Iwi et al.


Discussion iwi et al1

Discussion Iwi et al.


Propagation of sst anomalies

Propagation of SST anomalies

Box 1

  • Wefollow the mininimum of SST along the gyre

  • 7yearsbetween Labrador and GIN

  • True in the model (known)

  • And in the SST Reynolds data!

Box 2

Box 3

GSA

GSA

GSA

Box 4


A ir sea ice interactions

Air-seaice interactions

NCEP

& HadISST

  • Anomalouswind stress in the NCEP and HadISST seaice, similar to whatisobtained in the simulations.

  • An indication of the existence of the air-sea-seaice interaction fromour 20-yr cycle.

Nudged

ensemble

Historical

ensemble

% seaicecover


Hindcasts3

Hindcasts


What do we expect from initialisation

What do weexpectfrom initialisation?

Climatic index

Observations

Model free

Model initialised

Time

  • Assumptions:

  • Climatic oscillations correctlyrepresented in model (frequency, amplitude)?

  • There existsways to phase the twosignalsusingcoupledmodels?


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