Same real chemistry as the 3D version, shown as two 2D-native diagrams instead of a rotating coral mesh. Whether seawater lets a shell-forming organism build calcium carbonate — or slowly dissolves it — is set by the saturation state:
Ω = [Ca²⁺][CO₃²⁻] / K'sp
Ω > 1 → supersaturated, precipitation favoured
Ω < 1 → undersaturated, dissolution favoured
[CO₃²⁻] comes from the same carbonate equilibrium system: Henry's law CO₂ solubility (K₀), carbonic-acid dissociation (K₁, K₂) and the alkalinity balance TA ≈ [HCO₃⁻] + 2[CO₃²⁻], solved exactly as in the 3D model (Weiss 1974 K₀, Mehrbach/Dickson-Millero 1987 K₁/K₂, fixed salinity 35).
- Top panel — Ω isopleth field: a 2D grid over atmospheric pCO₂ (x) and sea-surface temperature (y), with every cell's own Ω solved independently from the same equilibrium equations and coloured cyan (supersaturated) through white (Ω=1, drawn as a bright contour line) to orange (undersaturated). The crosshair marks the current slider settings; dragging alkalinity re-solves and redraws the whole field, showing directly how more buffering capacity pushes the Ω=1 line toward higher CO₂ / colder water.
- Bottom panel — radial growth-band chronology: a cross-section of concentric bands, the way sclerochronologists actually read a coral or bivalve's growth history. Each band is deposited in real time at rate dR/dt ∝ (Ω−1) using the live Ω of whichever mineral is selected; band colour records the Ω regime at the moment it formed, so a shell's history of acidification exposure is literally visible as its ring pattern, from center (oldest) to rim (newest) — mirroring how real growth-band width and geochemistry are used to reconstruct past ocean chemistry.
- Mineral toggle — aragonite (dissolves first, K'sp ≈1.5× calcite's) vs. the more resistant calcite; switching mineral changes which Ω drives both panels.
Real-world relevance: since 1850 surface-ocean pH has fallen from ~8.2 to ~8.05 and aragonite Ω has dropped by roughly 20% globally; some polar and upwelling waters are already seasonally undersaturated (Ω<1) for aragonite.