The oceans are important climate regulators
- "Sinks" or "carbon-sinks"
Processes that take carbon dioxide from the air and move it to the ocean, vegetation, corals or soil for a longer period of time are called carbon sinks.
Examples are phytoplankton (small plants in the sea) that through photosynthesis absorb the gas from the air and places it in the water. Corals also use carbon when they build their reefs.
The oceans may also absorb CO2 directly from the air by diffusion.
The physical rule is that the colder the water is, the more gas it can absorb.
Cold water is as a rule denser than warm water.
Cold water will sink in vertical currents, while warm water will remain on the surface.
Cold periods, when surface water is significantly cooled down is therefore vital to the bioproduction of lakes and the oceans.
In those periods, oxygen-rich surface water sinks down towards the bottom, making it possible for oxygen-breathing organisms to live there.
At the same time, the bottom-water with lots of minerals in it will be pushed upwards by the cold surface water coming down.
The plants - the phytoplankton - living in the upper layers of the seas, where sunlight can reach, need those minerals to grow.
Periods with vertical currents and cold flushes of sea currents make temperate and polar seas very productive, while the warmer parts of the oceans may be compared to deserts.
Cold, salty water, typically found around the poles, is a very important carbon sink.
Carbon dioxide that is brought deep down in the oceans may remain there for hundreds of years.