A Carbon Sink is any process, activity, or mechanism that absorbs more carbon dioxide from the atmosphere than it releases. 
Forests, oceans, and soil are the world’s largest natural carbon sinks. Oceans absorb carbon dioxide from the atmosphere through marine ecosystems and the plant and animal life they harbor.
Sequestering carbon in marine ecosystems is generally referred to as Blue Carbon.
Forests and soil are the other main natural carbon sinks of the planet,storing carbon in trees and vegetation, wetlands and peat bogs, and plant litter.
Today, human activity, like burning fossil fuels and deforestation, causes more carbon to be released into the atmosphere than the Earth’s natural carbon sinks can absorb, leading to global warming and climate change. Human activities and climate change are also causing the degradation of these natural carbon sinks, threatening the release of the carbon they store back into the atmosphere. Therefore, protecting carbon sinks and expanding their capability to absorb carbon and store it long-term is a key strategy for tackling climate change and stabilizing the climate.