Nonlinear feedback and memory in an Ising model of sea ice

Abstract. Sea ice retreat depends on how ice and open water are arranged and on the heat available for melting. We extend a kinetic Ising model of ice and water by allowing neighbour coupling to respond to the surrounding pattern and retain its history. This coupling sets the resistance to changing an interface. We keep the average coupling fixed to isolate the effect of making some regions easier to melt and others harder. We derive the finite-block reversal energy and show why changing the coupling affects corners and straight fronts differently. In the global mean-field closure near ordering, coupling memory can destabilise a water-rich state through a subcritical Hopf bifurcation. In the strongly ordered seasonal regime, memory delays changes in interface barriers. Calculations driven by ERA5 reanalysis for the Pacific Arctic, initialised from satellite concentration in June 2022–2024, illustrate the seasonal interface response through September. Feedback increases front activity even under spatially uniform forcing. Additional melting occurs at exposed sites as the ice pattern evolves. A field shift matches the threshold for a front with equal incident bonds but not the full retreat pattern. With their early coupling amplitudes matched, memory and reduced instantaneous gain give similar seasonal transition counts but different histories. The model connects the geometry of retreat to environmental feedback and its response time.