1,721,085 research outputs found
Kuroshio Extension bimodality and the North Pacific Oscillation: a case of intrinsic variability paced by external forcing
No full textA previous North Pacific Ocean circulation model forced by climatological winds is extended here to include
a time-dependent North Pacific Oscillation (NPO) forcing. The Kuroshio Extension (KE) decadal
bimodal cycle (which is a self-sustained intrinsic relaxation oscillation in the climatologically forced case) is
now excited by the NPO forcing. Both the timing of the cycles and the Rossby wave teleconnection mechanism
that is found to govern the synchronization from 1993 to 2012 are in good agreement with altimeter
observations. Sensitivity numerical experiments are carried out by varying the zonal location and amplitude
of the NPO forcing, and the lateral eddy viscosity. The emergence of the KE bimodality with a correct timing
is found to be extremely sensitive to changes in the dissipative parameterization; the implications of such
sensitivity for deficiencies found in more realistic North Pacific Ocean general circulation models are discussed.
The dynamical mechanism that emerges from this study is explained as a case of intrinsic variability in
an excitable dynamical system triggered, and therefore paced, by an external forcing
A divergent quasi-geostrophic model for wind-driven oceanic fluctuations in a closed basin
No full text
Stochastic tipping points in climate dynamics
No full textA crucial question recently raised in climate dynamics concerns abrupt climate transitions: Are they due to
a tipping point (TP) being exceeded, or is fast noisy dynamics the cause of their excitation? In this respect,
a case study based on a low-order ocean model is developed to show that in an excitable dynamical system
perturbed by noise (a possible climate condition) the TPs may have limited physical meaning, with the coherence
resonance mechanism being predominant. The analysis is based on an operational definition of stochastic TP,
which accounts for the effect of noise and reconciles formally the TP and coherence resonance views
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