Answer:
Option D, Regional and possibly global climate
Explanation:
The ocean conveyor belt is very essential for maintaining the level of nutrients in water at the surface of ocean. Whenever the nutrients in the surface water are depleted, it is enriched with nutrients as the surface water passes through the conveyor belt. It is system that constantly moves with the help of deep and surface ocean currents thereby causing water to move across the globe. When ocean becomes hot water rises to the surface and when it losses heat to the atmosphere it becomes cool and make the surface water cool and dense. Being a global conveyor belt, it regulates global climate.
Hence, option D is correct