For decades, the Southern Ocean, which wraps around Antartica, has absorbed extraordinary amounts of excess warming, over 90 per cent of the planet’s heat, and a quarter of human-generated CO₂. Scientists now warn that this vast reservoir may not remain contained. New modelling published in AGU Advances suggests the ocean could abruptly release the stored warmth in what researchers describe as a climatic ‘burp’, triggering a renewed rise in global temperatures even after humanity succeeds in cutting emissions. Such a release could keep warming alive for more than a hundred years and emerge only after global cooling has begun.
According to Daily Galaxy, the model shows that this heat release would not unfold gradually. Instead, after several centuries of net-negative emissions, during which carbon is removed from the atmosphere and global temperatures steadily fall, the Southern Ocean could suddenly overturn, sending long-buried heat to the surface. The resulting warming would be comparable to rates driven by human activity today.
The ‘burp’ is marked by gray shading Photograph: (AGU Advances)
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How a Heat ‘Burp’ Forms
The mechanism behind this potential surge lies in the ocean’s structure. As described by the study and reported by Phys.org, the Southern Ocean becomes colder and saltier at the surface as new sea ice forms; the freezing process rejects salt into surrounding waters, making the surface layer denser. Warm water, however, remains trapped at depth. Over time, this imbalance destabilises the water column. Phys.org, quoting Svenja Frey of the GEOMAR Helmholtz Centre, wrote, “At some point, the water column becomes unstable, and that’s when we have the deep convection event”, effectively allowing the deep heat to rise rapidly. The study finds that the resulting warming pulse would be strongest and longest-lasting in the Southern Hemisphere, particularly affecting countries in the global south. While some CO₂ may also be released, Daily Galaxy notes that the primary impact is thermal, not chemical.
Implications for Future Climate Strategy
The scenario remains a projection, not a certainty, yet scientists view it as a crucial insight into long-term climate behaviour. Climate researcher Kirsten Zickfeld, according to Phys.org emphasises that Earth’s response to net-negative emissions is poorly understood and may involve ‘surprises’, including feedbacks like this one. Importantly, overall temperatures still fall in the model, just not smoothly. “To be clear, in this scenario, removing atmospheric carbon significantly reduces global temperatures, even factoring in the burp. And the faster we move away from fossil fuels, the less CO2 we’ll have to remove down the line”, says live science.com.
Ric Williams of the University of Liverpool emphasised that negative emissions remain beneficial but argued that ‘rather than do negative emissions, it’s better not to do the positive emissions in the first place’, according to LiveScience.com.
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