For decades, Earth’s oceans have acted as powerful allies in the fight against global warming.
They have absorbed about a quarter of all human-made carbon dioxide (CO₂) emissions and more than 90% of the extra heat trapped by those emissions.
But a new study suggests that one ocean in particular—the Southern Ocean surrounding Antarctica—might not hold onto that heat forever.
According to new research published in AGU Advances, scientists have discovered that if global temperatures eventually start to fall due to large-scale CO₂ removal from the atmosphere, the Southern Ocean could suddenly release a huge amount of stored heat back into the air.
This unexpected event, described as an “oceanic burp,” could briefly warm the planet again even as overall emissions decline.
The study, led by Ivy Frenger and her colleagues, explored what might happen in the Southern Ocean under a future scenario of “net negative emissions”—a condition where humans remove more carbon from the atmosphere than they emit.
While most studies focus on how oceans will continue to absorb carbon and heat as emissions rise, this one looked at the opposite: how oceans might respond if emissions go down.
The Southern Ocean plays a crucial role in regulating the planet’s temperature.
It constantly circulates water between the deep ocean and the surface, allowing it to store vast amounts of carbon and heat.
To simulate how this system might react to a cooling climate, the researchers used the University of Victoria’s Earth system model (UVic v2.9), which combines atmospheric, oceanic, and land processes into one long-term climate simulation.
In their model, atmospheric CO₂ levels first doubled over 70 years, mimicking the rise in greenhouse gases due to human activity.
After that, emissions were sharply cut, and CO₂ removal led to centuries of cooling. But then, after several hundred years, the model showed something surprising: the Southern Ocean released a sudden burst of stored heat into the atmosphere.
This “burp” triggered a new phase of warming that lasted from decades to centuries—comparable in rate to past human-caused warming. Interestingly, while the ocean released a lot of heat, it gave off only a small amount of CO₂, due to the chemical properties of seawater.
The researchers emphasized that this study is based on an idealized model and doesn’t predict an exact timeline for such an event.
However, they say the results highlight the need to better understand the Southern Ocean’s behavior, especially its ability to release heat after centuries of storage.
As the planet works toward reducing greenhouse gases, scientists warn that Earth’s natural systems may not respond as smoothly as expected.
The Southern Ocean’s potential “heat burp” serves as a reminder that even when human activity slows down, the planet’s powerful feedback systems may still surprise us.
