Stommel Box Model: Thermohaline Circulation Bistability

The ocean's "conveyor belt" isn't a fixed pipe — it is a self-sustaining flow held up by a delicate balance between temperature and salinity, and it has more than one stable state. This simulator implements the classic Stommel two-box ocean model in 3D: a polar box and an equatorial box exchange heat and freshwater, and the density difference between them drives an overturning circulation. Turn up the freshwater forcing slider and watch the flow weaken; fire a meltwater pulse and watch a strong overturning cell collapse into a reversed, stagnant one — and stay collapsed even after the pulse is over, because for the same forcing both states are stable. Live readouts track the flow strength, temperature and salinity indices, and elapsed model time as the "conveyor" visibly slows, reverses, or restarts.