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

• Published in: Journal of Climate
• Main Authors: Robson, Jon, Sutton, Rowan, Lohmann, Katja, Smith, Doug, Palmer, Matthew D.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: American Meteorological Society 2012
• Subjects: North Atlantic; North Atlantic oscillation
• Online Access: https://centaur.reading.ac.uk/25560/

In the mid-1990s the subpolar gyre of the North Atlantic underwent a remarkable rapid warming, with sea surface temperatures increasing by around 1C in just 2 years. 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 we show 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, we infer 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. Our results provide persuasive evidence of significant oceanic memory on multi-annual timescales, and are therefore encouraging for the prospects of developing skillful predictions.