What is a Carbon Sink and Why Are They Important?

Carbon sinks, as opposed to carbon sources, are places where carbon from the atmosphere can be sequestered and stored. Carbon sinks are increasingly important today given their crucial role in reducing atmospheric carbon concentrations and helping mitigate climate change.

Examples of carbon sinks include the lithosphere, ocean, biosphere, and the cryosphere.

The lithosphere refers to the rocks that make up Earth, or in other words, the crust. The lithosphere is the largest carbon sink on Earth. Although it seems like carbon – which usually exists in the form of carbon dioxide in the atmosphere – couldn’t exist in rocks. Yet, many of these rocks are made from the carbon that comes from sediments on the ocean sea floor which came from the carbon-containing shells of aquatic organisms. Thus, rocks in the Earth’s crust are rich in carbon.

The ocean is another carbon sink that absorbs carbon by having carbon dioxide diffuse from the air into the water and combine with water molecules to form carbonic acid.

The biosphere is another carbon sink which involves wood, soil, and biomass.

The cryosphere stores carbon by having it as carbon dioxide trapped in ice.

Together, these carbon sinks work together to store carbon on the planet, reducing the amount of carbon stored in the atmosphere.