Scientists Solve Ocean ‘Carbon Sink’ Puzzle

The oceans are a hugely important “carbon sink”, helping absorb CO2 emissions from human activities.  Without them, CO2 would accumulate more quickly in the atmosphere, raising temperatures more quickly.

A new study, published in Nature, finds that recent changes in circulation patterns in the world’s oceans are playing a key role in how much CO2 they take up.

Weakening circulation patterns have boosted how much CO2 the oceans absorb since the 2000s, the researchers say, but there’s no guarantee that this will continue into the future.

Circulation patterns
The Earth’s oceans have absorbed about a third of the CO2 that humans have emitted into the atmosphere since the beginning of the Industrial Revolution.

But the amount of CO2 that the oceans absorb isn’t constant.  In the 1990s, ocean CO2 uptake dropped off, before increasing again in the 2000s.  Recent research shows that the Southern Ocean was central to these changes.

The Southern Ocean is the most prolific of the oceans for carbon storage – accounting for approximately 40% of the global ocean CO2 uptake.  In the 1990s, strengthening winds circulating around Antarctica affected ocean currents and brought carbon-rich water to the surface.  This meant the ocean was less able to absorb CO2 from the atmosphere.

In the 2000s, the winds continued to strengthen, yet the CO2 uptake in the Southern Ocean rebounded.  This, combined with increasing CO2 uptake in other oceans, suggested to scientists that there was, ultimately, another factor affecting the ocean carbon sink.

The new study says the reason lies in circulation patterns in the top 1,000m of the world’s oceans.

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