Causes of the rapid warming of the North Atlantic Ocean in the mid-1990s

• Published in: Journal of Climate
• Main Authors: Robson, Jon, Lohmann, Katja, Smith, Doug, Palmer, Matthew D.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2012
• Subjects: North Atlantic; North Atlantic oscillation
• Online Access: https://hdl.handle.net/1983/c62158f4-26f6-4e84-89d7-c47a8d3ea100; https://research-information.bris.ac.uk/en/publications/c62158f4-26f6-4e84-89d7-c47a8d3ea100; https://doi.org/10.1175/JCLI-D-11-00443.1; http://www.scopus.com/inward/record.url?scp=84864683275&partnerID=8YFLogxK

In the mid-1990s, the subpolar gyre of the North Atlantic underwent a remarkable rapid warming, with sea surface temperatures increasing by around 18C in just 2 yr. This rapid warming followed a prolonged positive phase of the North Atlantic Oscillation (NAO) but also coincided with an unusually negative NAO index in the winter of 1995/96. By comparing ocean analyses and carefully designed model experiments, it is shown that this rapid warming can be understood as a delayed response to the prolonged positive phase of the NAO and not simply an instantaneous response to the negative NAO index of 1995/96. Furthermore, it is inferred that the warming was partly caused by a surge and subsequent decline in the meridional overturning circulation and northward heat transport of the Atlantic Ocean. These results provide persuasive evidence of significant oceanic memory on multiannual time scales and are therefore encouraging for the prospects of developing skillful predictions.