Late Quaternary Climate Response at 100 kyr: A Noise-Induced Cycle Suppression Mechanism

Late quaternary climate proxies suggest the presence of a strong cycle at a period of about 100 kyr. It is thought that this cycle could be due to variations in the eccentricity of the Earth’s orbit, as part of the Milankovitch forcing. However, based on simple energy balance arguments, the eccentricity variations are too small to explain the strength of the climatic response. Some amplification mechanisms based on ice sheet dynamics or ocean circulation models have been suggested to explain this paradox. But recently (Wallmann 2014), a different explanation was proposed. There, a non-linear biogeochemical model coupling seawater alkalinity, dissolved phosphate, dissolved inorganic carbon, and atmospheric carbon dioxide without any orbital forcing was developed. As the parameters vary, the system may undergo a Hopf bifurcation and exhibits self-organized oscillations with a period that has the appropriate order of magnitude but remains larger than 100 kyr. In this contribution, I revisit Wallmann’s model by adding a weak stochastic periodic Milankovitch forcing at 100 kyr in the spirit of stochastic resonance phenomena. It is seen that for sufficiently high noise intensity, a noise-induced cycle suppression occurs, whereby the self-sustained oscillation of biogeochemical origin is destroyed and a strong signal persists at 100 kyr. This mechanism could thus provide an amplification mechanism for the presence of a strong response under the influence of a weak Milankovitch forcing.