Attractors and bifurcation diagrams in complex climate models

Abstract

The climate is a complex non-equilibrium dynamical system that relaxes toward a steady state under the continuous input of solar radiation and dissipative mechanisms. The steady state is not necessarily unique. A useful tool to describe the possible steady states under different forcing is the bifurcation diagram, that reveals the regions of multi-stability, the position of tipping points, and the range of stability of each steady state. However, its construction is highly time consuming in climate models with a dynamical deep ocean, interactive ice sheets or carbon cycle, where the relaxation time becomes larger than thousand years. Using a coupled setup of MITgcm, we test two techniques with complementary advantages. The first is based on the introduction of random fluctuations in the forcing and permits to explore a wide part of phase space. The second reconstructs the stable branches and is more precise in finding the position of tipping points.