What is the ‘carbon thirst’ of the world’s oceans?

What’s Going On Here?

A recent paper in Nature Communications has found that the world’s oceans could be absorbing significantly more carbon from the atmosphere than previously thought.

What Does This Mean?

The ocean is a carbon sink and absorbs around 25% of global atmospheric carbon dioxide through a process called the ‘ocean-atmosphere CO₂ flux’. This amounts to about 2 billion tonnes of carbon entering global oceans per year.

Yet new research has found that oceans could actually be absorbing between 0.8-0.9 billion tonnes more CO₂ per year. The study’s authors used satellite sensors to measure the ocean surface layer and found that it is slightly cooler than the layer below. Due to CO₂ having greater solubility at lower temperatures, this means the ocean surface layer has a higher capacity to remove CO₂ than previously understood.

Scientists have applied this new understanding to 27 years of measurements and data collected from ships, buoys and satellites, estimating that as much as 67 billion tonnes of CO₂ has been removed by the world’s oceans, as opposed to 43 billion tonnes.

Why Should We Care?

If the flux of carbon into the ocean carbon sink has been previously underestimated, this means that global CO₂ emissions could be greater or the land carbon sink smaller than is currently understood.

This has implications for the global carbon budget – an assessment of the global sources and sinks of carbon that is vital for both the scientific research community and for informing global climate policy and stabilisation targets.

And whilst the world’s oceans are crucial for controlling atmospheric CO₂ levels, the dissolution of CO₂ into the ocean impacts the chemistry of seawater through ocean acidification. As atmospheric CO₂ increases due to carbon-intensive human activities, the ocean acidification effect becomes more detrimental to marine life, in particular corals and other organisms with carbonate shells.

Be Curious!

• Read the new Nature Communications study here.
• Find out more about the importance of the global carbon budget.
• Watch this short-film from National Geographic – ‘How Carbon Dioxide Kills Ocean Life’