More extreme swings of the South Pacific convergence zone due to greenhouse warming

Cai, Wenju; Lengaigne, Matthieu; Borlace, Simon; Collins, Matthew; Cowan, Tim; McPhaden, Michael J.; Timmermann, Axel; Power, Scott B.; Brown, Josephine R.; Menkès, Christophe E.; Ngari, Arona; Vincent, Emmanuel M.; Widlansky, M. J.

doi:10.1038/nature11358

Cited by 178 publications

(188 citation statements)

References 28 publications

(51 reference statements)

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“…Recent modeling work (e.g., Cai et al, 2012) has demonstrated the possibility for warmer surface conditions to produce more extreme equatorward movement of the SPCZ during interannual variability, producing more interannual, El Niño-Southern Oscillation (ENSO)-related drought at our study site. Given our lack of ability to consistently resolve interannual variability in the stalagmite record, we cannot address interannual changes in the SPCZ that may be related to anthropogenic forcing.…”

Section: Stalagmite Variability: External Forcing Vs Internal Variabmentioning

confidence: 95%

Persistent decadal-scale rainfall variability in the tropical South Pacific Convergence Zone through the past six centuries

et al. 2014

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Abstract. Modern Pacific decadal variability (PDV) has global impacts; hence records of PDV from the preinstrumental period are needed to better inform models that are used to project future climate variability. We focus here on reconstructing rainfall in the western tropical Pacific (Solomon Islands; ∼ 9.5 • S, ∼ 160 • E), a region directly influenced by PDV, using cave deposits (stalagmite). A relationship is developed between δ 18 O variations in the stalagmite and local rainfall amount to produce a 600 yr record of rainfall variability from the South Pacific Convergence Zone (SPCZ). We present evidence for large (∼ 1.5 m), abrupt, and periodic changes in total annual rainfall amount on decadal to multidecadal timescales since 1423 ± 5 CE (Common Era) in the Solomon Islands. The timing of the decadal changes in rainfall inferred from the 20th-century portion of the stalagmite δ 18 O record coincides with previously identified decadal shifts in PDV-related Pacific ocean-atmosphere behavior (Clement et al., 2011;Deser et al., 2004). The Solomons record of PDV is not associated with variations in external forcings, but rather results from internal climate variability. The 600 yr Solomon Islands stalagmite δ 18 O record indicates that decadal oscillations in rainfall are a persistent characteristic of SPCZ-related climate variability.

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Section: Stalagmite Variability: External Forcing Vs Internal Variabmentioning

confidence: 95%

Persistent decadal-scale rainfall variability in the tropical South Pacific Convergence Zone through the past six centuries

et al. 2014

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“…3e) is still dominated by a drying of the SPCZ, but rainfall increases in the western Pacific region between 0−10 • S, consistent with the notion that regions warming most become wetter and regions that warm least become drier 20 . This mean northeastward shift of the SPCZ is reminiscent of the zonal SPCZ events that have occurred together with some strong El Niño events 13,40 .…”

Section: T He Observed Spcz (Ref 1) Extends From the Tropical Westernmentioning

confidence: 96%

“…1b). A reduced meridional SST gradient 13 between 0 − 15 • S causes the rainfall increase at the Equator while a larger zonal SST gradient 21 in the eastern tropical South Pacific between 10 • S and 20 • S leads to an intensification of the southeasterly trade winds in this region 26 , thus enhancing transport of dry air towards the eastern side of the SPCZ.…”

Section: T He Observed Spcz (Ref 1) Extends From the Tropical Westernmentioning

confidence: 99%

“…The SPCZ response to ENSO-related changes in SST gradients can be understood to a large extent in terms of a combination of equatorial Kelvin and Rossby wave dynamics 10 , convective nonlinearities 11 and boundary layer processes 12 . Recent climate modelling work provides evidence for an increase in extreme zonally oriented SPCZ events associated with strong El Niño events during the twenty-first century 13 . However, there remains much uncertainty on how ENSO will respond to greenhouse warming 14,15 and how the projected increased occurrence of zonal SPCZ events is related to slower basic-state changes.…”

Section: T He Observed Spcz (Ref 1) Extends From the Tropical Westernmentioning

confidence: 99%

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Changes in South Pacific rainfall bands in a warming climate

et al. 2012

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The South Pacific Convergence Zone (SPCZ) is the largest rainband in the Southern Hemisphere and provides most of the rainfall to southwest Pacific island nations. In spite of various modelling efforts, it remains uncertain how the SPCZ will respond to greenhouse warming. Using a hierarchy of climate models we show that the uncertainty of SPCZ rainfall projections in present-generation climate models can be explained as a result of two competing mechanisms. Higher tropical sea surface temperatures lead to an overall increase of atmospheric moisture and rainfall whereas weaker sea surface temperature gradients dynamically shift the SPCZ northeastward and promote summer drying in areas of the southwest Pacific. On the basis of a multi-model ensemble of 76 greenhouse warming experiments and for moderate tropical warming of 1-2 • C we estimate a 6% decrease of SPCZ rainfall with a multi-model uncertainty exceeding ±20%. For stronger tropical warming exceeding 3 • C, a tendency for a wetter SPCZ region is identified. Supplementary Fig. S1) and delivers considerable amounts of rainfall to South Pacific islands during austral summer 1,5,6 (December-February: DJF), which we focus on in the analyses presented here. The seasonal march of this ∼8,000-10,000-km-long rainband is largely controlled by the seasonal cycle of the underlying sea surface temperature (SST) field, with air-sea interactions playing a key role 7 .On interannual timescales the southwest Pacific is strongly affected by the El Niño/Southern Oscillation 6,8,9 (ENSO). During El Niño conditions, as a result of the reduced meridional SST gradients, the SPCZ and associated maximum rainfall typically shift northeastward 8 while islands to the southwest often experience drying. An opposite, southwestward, shift in rainfall accompanies La Niña events. The SPCZ response to ENSO-related changes in SST gradients can be understood to a large extent in terms of a combination of equatorial Kelvin and Rossby wave dynamics 10 , convective nonlinearities 11 and boundary layer processes 12 . Recent climate modelling work provides evidence for an increase in extreme zonally oriented SPCZ events associated with strong El Niño events during the twenty-first century 13 . However, there remains much uncertainty on how ENSO will respond to greenhouse warming 14,15 and how the projected increased occurrence of zonal SPCZ events is related to slower basic-state changes.Whereas state-of-the-art coupled general circulation models (CGCMs) consistently simulate an enhanced equatorial warming [16][17][18][19][20] in response to increasing greenhouse-gas concentrations (Fig. 1a,c), the present twenty-first-century projections of SPCZ rainfall remain highly uncertain 21 Fig. 1), one finds that the ensemble mean rainfall response to intensified equatorial warming and reduced off-equatorial South Pacific warming (Fig. 1a) is characterized by a large rainfall increase in the equatorial Pacific, slightly more rainfall (5%) in the northwestern area of the climatological SPCZ and a drying o...

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“…1). The anomalous conditions caused severe Page 3 of 14 rainfall deficits in the western Pacific and the Maritime Continent, devastating hurricanes in the central tropical Pacific region (where such phenomena are extremely rare 4,8,10,11 ), and the disappearance of marine life and decimation of the native bird population on Christmas Island 17,18 . The high SSTs led to severe bleaching of corals in the Pacific and beyond 5,6 , including the 1998 mass mortality of corals on lagoonal reefs in Belize -the first time a coral population in the Caribbean collapsed completely from bleaching 6 .…”

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confidence: 99%