Coastal Upwelling Dynamics

Physics: Along-shore wind stress τ generates Ekman transport M_E = τ/(ρf) directed 90° to the right of wind (NH). When this moves water offshore, continuity requires deep, cold, nutrient-rich water to rise — coastal upwelling. Upwelling velocity w ~ (∂M_E/∂x)/H. Major upwelling zones: California, Humboldt, Benguela, Canary currents. Productivity ~10× background; supports ~20% of global fish catch.