How is the ocean both a "carbon sink" and a "carbon source"?

One of the things related to the oceans that is making climate change worse is the albedo effect, especially at the polar regions. What happens is that the polar ice caps usually reflect the sunlight and re-cool itself overnight when it isn't as hot, and there is no sunlight. Now that it is beginning to warm up, the ocean water starts to show. The ocean is a very dark color compared to ice and snow, therefore it absorbs the sun and then at night, releases the heat, therefore the ice caps are melting faster than ever. This also cause the sea level to rise. - Emily

Oceans absorb more than a quarter of CO2 (Carbon Dioxide) that is put into the air by humans, making it the largest active carbon sink. It was also found that in the Northeast Atlantic Ocean, (1991-2000) there was a higher respiration rate than in photosynthesis, meaning that the ocean was releasing carbon dioxide back into the atmosphere, and this happens in many oceans making it a carbon source. - Henry

The ocean is a carbon sink when carbon dioxide dissolves and sinks down. The ocean naturally has a cycle to contain it and rid itself of excess carbon. Carbon can off-gas at the ocean surface or be incorporated into the bodies of coral reefs and come out as limestone. But now extra carbon is sent into the atmosphere and later sinks into the ocean. This disrupts the cycle and causes the ocean to acidify with Carbonic acid, which causes things to die, which then causes the cycle to be disrupted even more and make things worse. - Ryan

The ocean is the world's largest carbon sink. The oceans store carbon dissolved in seawater, in coral reefs, and in ocean plant and algal life. When the ocean plants and algae die, that adds organic matter (carbon) to the ocean. - Alan

The ocean is always absorbing more and more carbon, and that’s not good. Because of the carbon that has collected in the ocean, the ocean is acidifying and making life harder on the animal life that lives there. If the ocean becomes too acidic, then we will lose much of our sea life, which will destroy the entire ocean ecosystem. - Josh

The ocean is a carbon sink. Which means the ocean stores any carbon it can in it, but the high amount of carbon in the air is now turning the ocean to acid. - Piper

The ocean is a huge bowl of carbon because it absorbs carbon from the atmosphere and stores it. - CJ

The ocean is a carbon “source” when fish and other animals breath out CO2 and there is not enough phytoplankton and subterranean to absorb this carbon.  Because of this the carbon that would have been absorbed instead enters the atmosphere.  These organisms are killed because of man-made disasters such as oil spills, pollution, acidification etc.
The ocean is a carbon “sink” when carbon dioxide sinks into the ocean and dissolves. This can only occur however when there is minimal pollution and acidification. - Aidan

In addition to carbon dioxide dissolving in the ocean, as organisms like plankton and coral grow in the ocean, they absorb sunlight AND carbon dioxide, making the ocean a carbon sink. Dissolved Carbon Dioxide also makes the oceans more acidic. However after that, the carbon dioxide from respiration could also escape as gas from the ocean surface. - Owen

The ocean is filling with carbon and is acidifying. The ocean currently holds most of the world’s carbon. This makes it a carbon sink. The ocean is also a carbon source because when the fish and plants decompose and when plants and animals respire, they release carbon, which can escape the ocean's surface as gas.    - Husdon

The ocean mostly holds carbon, but when it is stirred by currents, it can release it. - Leo