Carbonate Saturation Horizon

This simulator renders a vertical slice of ocean water column and lets calcium-carbonate shells sink through it as a real InstancedMesh "marine snow" field. Each shell dissolves once it crosses the depth where the carbonate saturation state Ω = [Ca2+][CO3^2-]/Ksp drops below 1 — the saturation horizon. Toggling between aragonite and calcite shows why the more soluble polymorph has a shallower horizon, and the CO2 and temperature sliders reproduce the two real drivers that move it: rising atmospheric CO2 lowers carbonate ion concentration and shoals the horizon (the mechanism behind measured ocean-acidification shoaling of the aragonite saturation horizon), while warmer surface water raises it via CaCO3's retrograde solubility. Live readouts track the current horizon depth, the surface saturation state Ω0, and the fraction of shells that survive the sinking journey to the seafloor intact.