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

Nonlinear quadratic and linear dynamical dependencies of large-scale climate modes are disentangled through the analysis of the rate of the information transfer. That is performed in a joint analysis of eight dominant climate modes, covering the tropics and extratropics over the North Pacific and Atlantic. A clear signature of nonlinear and compound 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.