A recent study highlighted in the IPCC 6th Assessment Report has brought attention to the potential collapse of the Atlantic Ocean's circulation due to melting glaciers. Researchers reveal that the circulation has visibly slowed over the past two decades, possibly reaching its weakest state in nearly a millennium. If the tipping point is reached, the circulation could fully shut down within a century, leading to drastic temperature drops of several degrees in North America, parts of Asia, and Europe.

The study simulated the flow of fresh water in Earth's climate models until the circulation reached a tipping point and revealed that the shutdown could occur within a century of hitting that point. As the circulation weakens, heat transport towards northern regions diminishes, causing abrupt climate shifts. Regions influenced by the Gulf Stream, such as North America and Europe, will experience significant cooling, with parts of Norway potentially facing temperature drops of more than 36°F (20°C).

Notably, the impact of the Atlantic circulation collapse extends beyond temperature changes, affecting sea levels, precipitation patterns, and other ecosystems. The Amazon rainforest, for example, could transition to grassland due to declining precipitation, releasing carbon into the atmosphere and accelerating climate change further. Such abrupt shifts in climate have profound implications for societies worldwide.

While uncertainties remain regarding the exact timing of the Atlantic circulation's tipping point, a physics-based early warning signal based on salinity transport at the ocean's southern boundary suggests that the tipping point could occur within one to four decades once a threshold is reached. The study emphasizes the urgency of addressing climate change to prevent catastrophic consequences associated with an abrupt collapse of the Atlantic Ocean's circulation.