Stochastic resonance in the thermohaline circulation

A wide variety of climate records have revealed the existence of sudden a r ecurrent climatic changes. An important part of this variability might be r elated to transitions between stable equilibrium states of the thermohaline circulation. Here, we employ a box model of the ocean thermohaline circula tion to show that in the presence of environmental fluctuations, a subthres hold periodic perturbation in the fresh water fluxes can induce quasiperiod ic transitions between the stable states of the thermohaline circulation Th is enhanced response occurs for a wide range of frequencies, including the Milankovic orbital forcing, and amplitudes. The mechanism that allows such response of the system under small perturbations arise from a nonlinear coo peration between the periodic perturbations and the fluctuations. Through t his nonlinear mechanism, called stochastic resonance, significant climatic variability may be originated due to small perturbations enhanced by enviro nmental noise and dynamics.