NAO-ocean circulation interactions in a coupled general circulation model

• Published in: Climate Dynamics
• Main Authors: Bellucci A, Gualdi S, Scoccimarro E, Navarra A
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2008
• Subjects: NAO; coupled; climate; North Atlantic; North Atlantic oscillation
• Online Access: http://hdl.handle.net/11585/793811; https://doi.org/10.1007/s00382-008-0408-4

The interplay between the North Atlantic Oscillation (NAO) and the large scale ocean circulation is inspected in a twentieth century simulation conducted with a state-of-the-art coupled general circulation model. Significant lead-lag covariance between oceanic and tropospheric variables suggests that the system supports a damped oscillatory mode involving an active ocean-atmosphere coupling, with a typical NAO-like space structure and a 5 years timescale, qualitatively consistent with a mid-latitude delayed oscillator paradigm. The two essential processes governing the oscillation are (1) a negative feedback between ocean gyre circulation and the high latitude SST meridional gradient and (2) a positive feedback between SST and the NAO. The atmospheric NAO pattern appears to have a weaker projection on the ocean meridional overturning, compared to the gyre circulation, which leads to a secondary role for the thermohaline circulation in driving the meridional heat transport, and thus the oscillatory mode.