Atlantic forcing of Pacific decadal variability
This paper investigates the Atlantic Ocean influence on equatorial Pacific decadal variability. Using an ensemble of simulations, where the ICTPAGCM (“SPEEDY”) is coupled to the NEMO/OPA ocean model in the Indo-Pacific region and forced by observed sea surface temperatures in the Atlantic region, it is shown that the Atlantic Multidecadal Oscillation (AMO) has had a substantial influence on the equatorial Pacific decadal variability. According to AMO phases we have identified three periods with strong Atlantic forcing of equatorial Pacific changes, namely (1) 1931–1950 minus 1910–1929, (2) 1970–1989 minus 1931–1950 and (3) 1994–2013 minus 1970–1989. Both observations and the model show easterly surface wind anomalies in the central Pacific, cooling in the central-eastern Pacific and warming in the western Pacific/Indian Ocean region in events (1) and (3) and the opposite signals in event (2). The physical mechanism for these responses is related to a modification of the Walker circulation because a positive (negative) AMO leads to an overall warmer (cooler) tropical Atlantic. The warmer (cooler) tropical Atlantic modifies the Walker circulation, leading to rising (sinking) and upper-level divergence (convergence) motion in the Atlantic region and sinking (rising) motion and upper-level convergence (divergence) in the central Pacific region.
KeywordsClimate shift Pacific mean state change Atlantic forcing Climate variability
The authors thank three anonymous reviewers for their constructive comments that helped improving the quality of the paper.
- Kucharski F, Syed FS, Burhan A, Farah I, Gohar A (2014) Tropical Atlantic influence on Pacific variability and mean state in the twentieth century in observations and CMIP5. Climate Dyn. doi: 10.1007/s00382-014-2228-z
- L’Heureux ML, Lee S, Lyon B (2013) Recent multidecadal strengthening of the Walker circulation across the tropical Pacific. Nat Clim Change. doi: 10.1038/NCLIMATE1840
- Madec G (2008) NEMO ocean engine. Note du Pole de modlisation, Institut Pierre-Simon Laplace (IPSL), France, No 27 ISSN No 1288–1619Google Scholar
- McGregor S, Timmermann A, Stuecker MF, England MH, Merrifield M, Jin F-F, Chikamoto Y (2014) Recent Walker circulation strengthening and Pacific cooling amplified by Atlantic warming. Nat Clim Change. doi: 10.1038/NCLIMATE2330
- Molteni F (2003) Atmospheric simulations using a gcm with simplified physical parametrizations. I: model climatology and variability in multi-decadal experiments. Clim Dyn 20(2):175–191Google Scholar
- Polo I, Martin-Rey M, Rodriguez-Fonseca B, Kucharski F, Mechoso CR (2014) Processes in the Pacific La Nina onset triggered by the Atlantic Nino. Clim Dyn. doi: 10.1007/s00382-014-2354-7
- Rayner NA, Parker DE, Horton EB, Folland CK, Alexander LV, Rowell DP, Kent EC, Kaplan A (2003) Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century. J. Geophys. Res. 108, doi: 10.1029/2002JD002670
- Valcke S (2006) OASIS3 User Guide (prism\_2-5). CERFACS Technical Report TR/CMGC/06/73, PRISM report no 3, Toulouse, France, p 60Google Scholar
- Xiang B, Wang B (2012) Mechanisms for the advanced Asian Summer Monsoon onset since the mid-to-late 1990s. J. Clim. doi: 10.1175/JCLI-D-12-00445.1
- Xiang B, Wang B, Li T (2012) A new paradigm for the predominance of standing Central Pacific Warming after the late 1990s. Clim Dyn. doi: 10.1007/s00382-012-1427-8
- Yang C, Giese BS, Wu L (2014) Ocean dynamics and tropical Pacific climate change in ocean reanalyses and coupled climate models. J Geophys Res Oceans. doi: 10.1002/2014JC009979
- Zhang R, Delworth TL (2007) Impact of the Atlantic multidecadal oscillation on north pacific climate variability. Geophys Res Lett 34:L23708Google Scholar