Stochastic Forcing of Ocean Variability by the North Atlantic Oscillation
Kettyah Chhak, Georgia Tech
Andy Moore, UC Santa Cruz
Ralph Milliff, Colorado Research Associates

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Perturbation Development
Considerable Interest!
    Veronis and Stommel (1956), Phillips (1966), Veronis (1970), Rhines (1975), Magaard (1977), Willebrand (1978), Philander (1978), Leetmaa (1978), Frankignoul and Muller (1979), Willebrand et al (1980), Wearn and Baker (1980), Muller and Frankignoul (1981), Haidvogel and Rhines (1983), Lippert and Kase (1985), Treguier and Hua (1987), Alvarez et al (1987), Niiler and Koblinsky (1989), Brink (1989), Luther et al (1990), Samelson (1990), Garzoli and Dimionato (1990), Large et al (1991), Samelson and Shrayer (1991), Chave et al (1991, 1992), Lippert and Muller (1995), Fu and Smith (1996), Muller (1997), Frankignoul et al (1997), Moore (1999), Stammer and Wunsch (1999), Hazeleger and Drijfhout (1999), Cessi and Louazel (2001), Sura and Penland (2002), Moore et al (2002), Aiken et al (2002, 2003), Sirven (2005), Berloff (2005), Weijer (2005), Weijer and Gille (2005), Sirven et al (2007), Chhak et al (2006, 2007, 2008).
    What did we observe and how predictable is it?

Conclusions
Stochastically forced variability can be as large as intrinsic variability.
Nonmodal interference dominates perturbation growth during first 10-14 days.
Significant deep circulations due to rectified topographic Rossby waves.
NAO is optimal for inducing variance on subseasonal timescales.

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Comments
Results applicable to stochastic forcing of ocean by other teleconnection patterns.
Implications for interpretion of observations.
Implications for ocean predictability.

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