A MECHANISM FOR DECADAL CLIMATE VARIABILITY
M. LATIF, A. GROTZNER, M. MUNNICH, E. MAIER-REIMER, S. VENZKE, T. P. BARNETTl
M ax-Planck-Institut fur M eteorologie
Hamburg, FRG
Contents
1 Introduction
2 Coupled ocean-atmosphere general circulation
model and observational data
2.1 Coupled model ..
2.2 Observational data . . . . . .
3 The decadal variability in the North Pacific
3.1 Observations . . . . . . . . . . . . . . . . . .
3.2 Coupled general circulation model simulation
3.3 Atmospheric response experiments
3.4 Oceanic response experiments
4 Simple coupled model
5 The decadal variability in the North Atlantic
6 Summary and discussion
Abstract
We describe in this paper a mechanism for decadal climate variability that can
lead to decadal climate cycles in the North Pacific and North Atlantic Oceans. A
hierarchy of numerical models and observations are used to understand the fundamental dynamics of these decadal cycles. They are generated by large-scale oceanatmosphere interactions in mid-latitudes and must be regarded as inherently coupled
modes. The memory of the coupled system, however, resides in the ocean and is
associated with slow changes in the subtropical ocean gyres.
When, for instance, the subtropical ocean gyre is anomalously strong, more warm
tropical waters are transported poleward by the western boundary current and its
extension, leading to a positive SST anomaly in mid-latitudes. The atmospheric
response to this SST anomaly involves a weakened storm track and the associated
lScripps Institution of Oceanography, La Jolla, Ca. , U. S. A.
NATO AS] Series, VoL] 44
Decadal Climate Variability
Dynamics and Predictability
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266
270
271
271
273
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287
Edited by David L. T. Anderson and JUrgen Willebrand
© Springer-Verlag Berlin Heidelberg 1996
M. LATIF, A. GROTZNER, M. MUNNICH, E. MAIER-REIMER, S. VENZKE, T. P. BARNETTl
M ax-Planck-Institut fur M eteorologie
Hamburg, FRG
Contents
1 Introduction
2 Coupled ocean-atmosphere general circulation
model and observational data
2.1 Coupled model ..
2.2 Observational data . . . . . .
3 The decadal variability in the North Pacific
3.1 Observations . . . . . . . . . . . . . . . . . .
3.2 Coupled general circulation model simulation
3.3 Atmospheric response experiments
3.4 Oceanic response experiments
4 Simple coupled model
5 The decadal variability in the North Atlantic
6 Summary and discussion
Abstract
We describe in this paper a mechanism for decadal climate variability that can
lead to decadal climate cycles in the North Pacific and North Atlantic Oceans. A
hierarchy of numerical models and observations are used to understand the fundamental dynamics of these decadal cycles. They are generated by large-scale oceanatmosphere interactions in mid-latitudes and must be regarded as inherently coupled
modes. The memory of the coupled system, however, resides in the ocean and is
associated with slow changes in the subtropical ocean gyres.
When, for instance, the subtropical ocean gyre is anomalously strong, more warm
tropical waters are transported poleward by the western boundary current and its
extension, leading to a positive SST anomaly in mid-latitudes. The atmospheric
response to this SST anomaly involves a weakened storm track and the associated
lScripps Institution of Oceanography, La Jolla, Ca. , U. S. A.
NATO AS] Series, VoL] 44
Decadal Climate Variability
Dynamics and Predictability
264
266
266
270
271
271
273
275
277
278
283
287
Edited by David L. T. Anderson and JUrgen Willebrand
© Springer-Verlag Berlin Heidelberg 1996