Sea Ice Dynamics

Physics: Sea ice thickness h grows by the Stefan problem: dh/dt = -k_i(T_s-T_f)/(ρ_i·L·h), giving h ∝ √(freezing degree-days). Ice albedo α_ice ≈ 0.8 vs ocean α_ocean ≈ 0.07 — a powerful positive feedback. Brine rejection during freezing drives haline convection, ventilating the deep ocean. Arctic sea ice extent has declined ~13%/decade since 1979. Summer minimum 2012: 3.41 million km² (record low). First-year ice (FYI) replaces multi-year ice (MYI).