Fig. 2.

(A) Scheme of a marsh basin. (B) Scheme of the marsh boundary. (C) w-h phase space of the marsh basin dynamic model, with r = 1.4 m, C_o = 30 mg/L, k_a = 2, k_e = 0.1 m³·y⁻¹·W⁻¹, RSLR = 2 mm/y, U_wind = 8 m/s. A single unstable non-trivial equilibrium (white circle) is present. The unstable manifold (red curve) quickly attracts all trajectories. Initial conditions to the left of the stable manifold (green curve) belong to the basin of attraction of the point [0, h_m], while initial conditions to the right of the stable manifold belong to the basin of attraction of the point [∞,h_∞], where h_∞ is the fetch-unlimited depth equilibrium. The stars and crosses represent the depths and diameters of 10 marsh basins along the US Atlantic Coast (Fig. 1 and Table S1).