Nullcline of the seasonally averaged sea ice I (olive) together with the nullcline of the Stommel atmosphere θ (wine). Due to the ice albedo feedback the sea ice model features a bistable region where an ice-rich and a low-ice solution coexist. The difference in the slope of the two stable branches is controlled by the strength of the sea ice export R0. The lower θ-nullcline is the same as in Fig. A1 with θ0 = 1.3 upon using the transformation γ = γ(I) given by Eq. (A22). The upper θ-nullcline results from setting θ0 = 1.6. The mutual relaxation rate γ(I) as a function of the sea ice is shown in light gray on the right ordinate. Intersections of the θ and I nullclines define fixed points of the entire coupled system defined by Eqs. (A17) and (A21). Larger atmospheric backgrounds θ0 yield more pronounced stadial conditions with colder Arctic atmosphere and larger sea ice cover.
Citation: Journal of Climate 37, 8; 10.1175/JCLI-D-23-0308.1
