ENSO-Related PDO and Its Changesdue to Global Warming

MinHo Kwon1, Jong-Ghap Jhun1, Sang-Wook Yeh2,and Young-Kyu Park2

1Seoul National University,2Korea Ocean Research and Development Institute

1 July 2008, Tokyo, Japan

UAW2008 (University Allied Workshop)

Introduction

EOF1 EOF2

Winter SST

Deser and Blackmon (1995)

► Pacific Decadal Oscillation (PDO) : Leading EOF mode of non- filtered North Pacific SST (Mantua et al., 1997)

Stochastic process : Hasselmann (1976), Barsugli and Battisti (1998)

Dynamic ocean : Frankignoul et al. (1997), Saravanan and McWilliams (1998), Weng and Neelin (1999) Frankignoul et al. (2000), Schneider et al. (2002), Schneider and Cornuelle (2005) westward Rossby wave propagation at Ocean, c.f. Jacobs et al. (1994)

NP Decadal Variability

Mid-latitude coupled modes : Latif and Barnett (1994; 1996),Weng and Neelin (1999), Miller et al. (1994),Seager et al. (2001), Deser et al. (1999)

Atmospheric bridge : Graham (1994), Graham et al. (1994),Newman (2003), An et al. (2007)

Ocean transports : Gu and Philander (1997),McPhaden and Zhang (2002), Lysne et al. (1997)

Connections with coupled process : Vimont et al. (2001; 2002)

PDO and ENSO

► PDO (North Pacific SST variability) origin?ENSO, the Aleutian Low, the Kuroshio-Oyashio

Extension multiple origins(Schneider and Cornuelle, 2005)

► ENSO-related PDOReddened ENSO signal(e.g. Newman et al, 2003; An and Wang, 2005)

► Effects on continental climate of ENSO-PDO relationshipModified PNA pattern…(e.g. Pavia et al., 2006)

Questions?

► ENSO changes due to global warming ENSO-related PDO changes?

► What about ‘non-ENSO’-related PDO changes due to global warming in current-state coupled GCMs (AR4-IPCC participating models).► Relationship between ‘non-ENSO’- and ENSO-related PDO, its changes under global warming climate state?

Persistence and Wintertime Coupling

► An and Wang (2005)

Winter anomalies recover via subsurface temperature in the next wintertime.

► Reemergence theory : SST persistence (Alexander et al., 2001)

AR4-IPCC Scenarios

► 20C3M (1900-1999) DJF► SRES A1B (2100-2199) DJF

12 IPCC coupled models

GHG

Commitment period

The analysis is focused on the commitment period in DJF mean.

SST Trends in IPCC models

PDO (Pacific Decadal Oscillation)

30.1%

16.9%

10.8%

Detrended DJF ERSST(1894-2007)

There are three separable EOF modes of SSTs in North Pacific in observation.

Changes in EOFs over NP

EOF structure of North Pacific SST changes in time.The spatial pattern of PDO has

changed.

PDOs in IPCC models

PDOs in IPCC models

North’s criteria

ENSO-related SST in IPCC models

ENSO-related North Pacific SST variability has increased.

12-model ensemble

Changes in ENDO-PDO relationship

20C3M

A1B

ENSO and PDO composite

Western and Central PDOsERSST (DJF)

Two distinctive variability

WPDO and CPDO are related to each other but their regression patterns have distinctive differences.

Decoupled Indian Ocean

ES10CORR(WPDO, CPDO) = 0.49

ESdICORR(WPDO, CPDO) = 0.71

► SINTEX-F1 Coupled GCM OPA 8.2-2 degree,31 levels ECHAM4–T106, 19 levels Luo et al. (2003; 2005) ES10 : control run (100yrs) ESdI : decoupled run (70yrs) (Indian Ocean)

Indian Ocean SST could make complex variability of WPDOassociated with CPDO.

Western and Central PDOs

WPDO CPDO

Conclusions

► The relationship between PDO and ENSO has a tendency to be enhanced in greenhouse gas-saturated climate state according to AR4-IPCC coupled models.► ‘Western PDO’ favors Indian SST anomalous condition. Indian SST anomaly could interfere the relationship between Western and Central PDOs.► Indian Ocean decoupled run confirms the role of Indian SST on the Western PDO.► The western and Central PDOs would be more separable under global warming climate state. ► EOF structure over North Pacific has changed around the 1960s in observation.

PDO Nonlinearity

Nonlinear tool : Hsieh et al. (1999)

Western and Central PDOs