In a new study, scientists from University of Sydney found how carbonate accumulation from ‘marine snow’ in oceans has helped regulate Earth’s temperature over the past 120 million years.
Marine snow is the falling debris of dead organisms in the ocean, such as plankton and algae.
It forms a blanket on the seafloor up to many hundreds of meters thick.
Previous research has shown that the deep ocean floor is covered with the remains of these tiny sea creatures.
They produce more than 25% of the oxygen humans breathe and form the Earth’s largest carbon sink.
When organic particles fall from the surface ocean to the seafloor, a small but significant proportion of atmospheric carbon is stored away.
According to the researchers, these marine snow deposits become carbonate structures when compacted over millions of years.
Examples include the White Cliffs of Dover and similar structures along England’s south coast.
These chalk cliffs and their related structures under the ocean act as millennia-old carbon capture devices.
Because deep-sea carbonates represent a huge volume, even small changes in the sequestration of carbonate carbon into this enormous sink are quite important for scientists to understand the net changes in atmospheric carbon dioxide and climate.
In the current study, the team found that the amount of carbon stored in carbonate layers on the seafloor has increased tremendously over time.
For example, only one megatonne of carbon ended up in carbonate layers annually about 80 million years ago.
The rate grew to about 30 megatonnes about 35 million years ago and 200 megatonnes today.
The team suggests that while the carbonates forming in shallow waters decreased, the rise in deeper deposits was far greater.
This has created a net increase in the total volume of carbonate sediments in the oceans in the past 80 million years.
The researchers believe the findings help advance our understanding of the ocean’s future capacity to store carbon dioxide.
This is very important given warming-ocean acidity has increased 30 percent since 1800.
The team believes that the growth of a significant carbon sink over millions of years may be responsible for the removal of carbon dioxide from the atmosphere.
It led to global cooling 50 million years ago and triggered the transition from a hothouse to an icehouse climate around 35 million years ago.
The team also warned that global warming could release some of that carbon into the atmosphere.
The study is published in Geology. The study’s lead author is Dr. Adriana Dutkiewicz.
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