How are density currents formed?

Surface currents form on the surface when wind blows and pushes it, forming a current ... Density currents form when water becomes cold and dense and sinks to the bottom and travels along the see floor, then it reaches warmer water and it warms and rises and repeats the cycle.

Density currents form when water becomes cold and dense and sinks to the bottom and travels along the sea floor, then it reaches warmer and it warms and rises and repeats the cycle.