carbon dioxide entering the ocean from the atmosphere continually. explain how some og this carbon can become “tied up” in the ocean for hundreds and sometimes millions of years

Carbon can become "tied up" in the ocean for hundreds and sometimes millions of years because dissolved carbon dioxide in water can sink with cold water to the bottom where it is moved slowly by deep ocean currents for hundreds of years before it is released to the atmosphere. This can lead to ocean acidification (the ongoing decrease (more acidic) in the pH of the Earth's oceans, caused by the uptake of carbon dioxide from the atmosphere)