Nonlinear causal dependencies as a signature of the complexity of the climate dynamics

Abstract. Nonlinear quadratic dynamical dependencies of large-scale climate modes are disentangled through the analysis of the rate of information transfer. Eight dominant climate modes are investigated covering the tropics and extratropics over the North Pacific and Atlantic. A clear signature of nonlinear influences at low-frequencies (time scales larger than a year) are emerging, while high-frequencies are only affected by linear dependencies. These results point to the complex nonlinear collective behavior at global scale of the climate system at low-frequencies, supporting earlier views that regional climate modes are local expressions of a global intricate low-frequency variability dynamics, which is still to be fully uncovered.