Decadal interactions between the western tropical Pacific and the North Atlantic Oscillation |
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| Authors: | Fred Kucharski Franco Molteni Annalisa Bracco |
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| Institution: | (1) Physics of Weather and Climate Section, The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, 34014 Trieste, Italy |
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| Abstract: | The relationship between interdecadal variations of tropical sea surface temperature (SST) in the last 120 years and circulation
anomalies related to the North Atlantic Oscillation (NAO) is investigated in this study. Using an atmospheric general circulation
model (AGCM), we confirm observational evidence that variations in the SST gradient in the western tropical Pacific are related
to the NAO anomalies on decadal timescale, and may be contributing to the shift towards the positive NAO phase observed in
the late 20th century. The role played by the Indian Ocean-NAO teleconnection, advocated in recent studies focused on the
last 50 years, is also assessed in the context of the 120-year long record. It is suggested that a positive feedback between
the Pacific SST and the hemispheric circulation pattern embedding the decadal NAO signal may act to enhance the internal variability
of the coupled ocean–atmosphere system, and justify the stronger teleconnection found in observational data than in SST-forced
AGCM experiments.
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