New modeling suggests a full AMOC collapse could drive deep-ocean mixing near Antarctica, releasing huge CO₂ amounts and accelerating warming.
A weakening of a major North Atlantic ocean current system—part of the planet’s heat-transport “conveyor belt”—may carry an alarming additional risk: releasing long-stored carbon near Antarctica.
The Atlantic Meridional Overturning Circulation (AMOC). closely linked to the Gulf Stream. has been slowing as human-driven warming changes the density of seawater.. In Misryoum’s coverage of the new findings. the central concern isn’t only the familiar story of shifting temperatures and rainfall patterns.. The research points to a potentially powerful feedback in which deep Southern Ocean waters could be stirred upward and allow carbon dioxide (CO₂) to return to the atmosphere.
To understand why scientists are focused on the Southern Ocean, it helps to picture how AMOC works.. Driven by differences in water density, the system transports warm, salty water northward.. There, the water cools, becomes denser, and sinks—before returning southward at depth.. That sinking is crucial.. But melting ice and freshwater input can dilute seawater. reducing the density that allows the water to sink in the first place.. That dilution is one reason the AMOC has been declining. with recent measurements showing a weakening of the deep return flow.
The new computer modeling explores what happens if AMOC shutdown occurs in different climate futures.. Under scenarios where atmospheric CO₂ reaches at least 350 parts per million. the AMOC does not recover once it shuts down—suggesting a kind of irreversibility.. Misryoum readers should see this as a shift from “possible” tipping behavior to “commitment” behavior: once key physical thresholds are crossed. the climate system may slide into a new mode rather than returning to today’s pattern.
The most striking element of the work centers on carbon stored in deep water around Antarctica.. Near the Antarctic surface. freshwater and sea-ice processes create a layered ocean in which deeper waters are largely isolated from the air for long periods.. Over time. those deep waters can accumulate CO₂—from atmospheric uptake and from the slow sinking and breakdown of organic matter.. If AMOC collapse triggers stronger mixing or convection near Antarctica, that barrier could weaken.. The model suggests much of the carbon in those deep reservoirs could be released. turning an ocean sink into a source.
That matters because it changes the shape of the warming problem.. Carbon dioxide released from the ocean would add to the greenhouse gases already driving climate change—amplifying warming beyond what human emissions alone would cause.. In the modeling. the additional heating tied to this released CO₂ reaches an extra 0.2°C globally. while the Antarctic region warms substantially.. The study also projects large temperature swings elsewhere, including cooling over the Arctic linked to the circulation’s failure.
There is a second implication that goes beyond carbon.. The ocean “conveyor belt” doesn’t act alone; it influences regional climates—winter severity in Europe. rainfall patterns affecting monsoons. and broader temperature distribution.. Misryoum emphasizes that the current concern is not just whether AMOC collapses. but how chain reactions across components of the climate system can multiply impacts.. When one part of the Earth system shifts. other parts can respond in ways that are difficult to anticipate in advance.
Still, scientists caution that uncertainty remains.. Even if the physical logic makes sense—less-salty waters altering stratification and enabling deeper water to reach the surface—the strength of Southern Ocean convection under warming is not settled across models.. Misryoum’s editorial takeaway is that this kind of uncertainty is not a reason for complacency; it’s a reminder that the risk is partly determined by processes we are still working to represent precisely.
The time horizon adds urgency in a different way.. The carbon-release effects in the model unfold over a long period—on the order of a thousand years or more after shutdown.. But the “commitment time. ” the window in which human greenhouse gas emissions may effectively lock the system into collapse. could be much shorter.. That is the crux of the warning: even if the worst consequences emerge later. decisions and emissions now can shape whether the tipping point is approached.
The study’s projections also intersect with ice-sheet vulnerability.. A stronger warming signal near Antarctica could contribute to conditions that threaten ice sheets already under pressure.. Misryoum highlights that while global average warming is often discussed in terms of a few tenths of a degree. regional temperature extremes and ocean-driven processes can determine whether ice behaves smoothly or destabilizes.
What AMOC collapse would mean for carbon and climate
The uncertainty that still matters
Why the “commitment time” changes the stakes
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