concept

Thermohaline circulation

The ocean's great heat conveyor, driven by differences in water density - which temperature (thermo) and salinity (haline) together set. Cold, salty water at high latitudes sinks to the deep, flows through the basins, and upwells in warmer regions, closing a loop that moves heat around the planet. On Pandora, tidal-heating warms the seafloor, so its circulation leans toward nutrient-rich local upwelling rather than Earth's sink-at-the-poles pattern.