Calcium Carbonate Saturation State (Ω) — 2D Isopleth & Growth-Band Chronology

This is the 2D counterpart to the 3D coral-skeleton saturation simulator. It solves the exact same carbonate-chemistry equilibrium — Henry's law CO₂ solubility, carbonic-acid dissociation, and the alkalinity balance — from atmospheric CO₂, sea-surface temperature and total alkalinity, but renders the result two ways that are native to 2D rather than a flattened 3D view: a live isopleth field mapping saturation state Ω across the full CO₂-versus-temperature parameter space with the Ω=1 boundary traced as a contour line, and a radial growth-band cross-section — the same kind of ring chronology a sclerochronologist reads from a real coral or bivalve shell — that accretes or erodes bands in real time at a rate set by the live Ω of whichever mineral, aragonite or calcite, is selected.