Low-Frequency Variability Of The Large-Scale Ocean Circulation: A Dynamical

• Main Authors: Henk A. Dijkstra, Michael Ghil
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2002
• Subjects: Southern Ocean
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.15.1783; http://www.atmos.ucla.edu/tcd/PREPRINTS/rg_dijkstra_ghil.pdf

Oceanic variability on interannual, interdecadal and longer time scales plays a key role in climate variability and climate change. Paleoclimatic records suggest major changes in the location and rate of deep-water formation in the Atlantic and Southern Ocean on time scales from millennia to millions of years. Instrumental records of increasing duration and spatial coverage document substantial variability in the path and intensity of ocean surface currents on time scales of months to decades. We review recent theoretical and numerical results that help explain the physical processes governing the stability and low-frequency variability of the large-scale ocean circulation. To do so, we apply systematically the methods of dynamical systems theory. In this approach, one follows the road from simple, highly symmetric model solutions, through a "bifurcation tree," toward the observed, complex behavior of the system under investigation. The dynamical systems approach is proving successful for more and more detailed and realistic models, up to and including oceanic and coupled ocean-atmosphere general circulation models. The observed variability can be shown to have its roots in simple transitions from a circulation with high symmetry in space and regularity in time to circulations with successively lower symmetry in space and less regularity in time. This road of successive bifurcations leads through multiple equilibria to oscillatory and eventually chaotic solutions. Key features