Ocean Carbon Cycle

Physics: The ocean holds ~38,000 Gt C (vs 860 Gt atmosphere). CO₂ solubility follows Henry's Law: [CO₂(aq)] = K_H·pCO₂, with K_H ∝ exp(ΔH/RT) — cold water absorbs ~3× more CO₂ than warm. Dissolved CO₂ hydrates: CO₂+H₂O ⇌ H₂CO₃ ⇌ H⁺+HCO₃⁻ ⇌ 2H⁺+CO₃²⁻. pH from 8.2→8.1 (30% more acidic since 1750). Biological pump: phytoplankton fix ~50 Gt C/yr; 10–20% sinks as organic particles. Aragonite saturation Ω = [Ca²⁺][CO₃²⁻]/K_sp — coral reefs dissolve when Ω<1.