Final answer:
Carbon dioxide diffuses between the ocean and the atmosphere as part of the carbon cycle, which is essential for regulating the global climate.
Step-by-step explanation:
Carbon dioxide diffuses between the ocean and the atmosphere. This exchange is a crucial part of the carbon cycle, where carbon dioxide (CO₂) from the atmosphere dissolves in the ocean water and turns into carbonic acid, which then ionizes to form carbonate and bicarbonate ions. The oceans act as a major reservoir for carbon, absorbing CO₂ from the atmosphere through various processes, including the photosynthesis by marine plants and the dissolution of CO₂ in seawater. Conversely, CO₂ is also released back into the atmosphere from the ocean. This exchange helps to regulate the global climate by controlling the amount of carbon dioxide in the atmosphere.