At a Glance
- Despite widespread ocean warming, a persistent cold spot has developed south of Greenland over the last century, a phenomenon scientists refer to as the North Atlantic Warming Hole.
- A new study confirms this cooling is caused by the long-term weakening of the Atlantic Meridional Overturning Circulation, a vital ocean current that distributes heat globally.
- Researchers validated their findings by showing that only climate models with a slowing AMOC could successfully replicate the observed temperature and salinity changes in the region.
- The slowdown of this massive current has significant implications for global weather, as it can alter storm tracks and disrupt marine ecosystems that depend on stable ocean conditions.
- This evidence helps settle a major scientific debate, indicating that ocean dynamics are the primary driver of the cooling and improving the accuracy of future climate change projections.
While Earth’s oceans have steadily warmed over the last century, a large patch of the North Atlantic south of Greenland has defied this trend, creating a mysterious cold spot. A new study, published in Communications Earth & Environment, provides robust evidence that the North Atlantic Warming Hole, an anomaly, is caused by the long-term weakening of a critical ocean current system. By analyzing historical data and a range of climate simulations, researchers have demonstrated that a slowdown in the Atlantic Meridional Overturning Circulation, or AMOC, is the only explanation that matches the observed cooling and decreased salinity in the region.
The AMOC acts as a massive oceanic conveyor belt, transporting warm, salty water from the tropics northward near the surface and sending cooler, deeper water southward. This process is vital for regulating the global climate by distributing heat around the planet. To understand its historical behavior, scientists examined over a century of sea surface temperature and salinity records. They used this data as a fingerprint to test nearly 100 different climate models. The findings were clear: only the models that simulated a weakening of the AMOC successfully reproduced the distinct cooling and freshening pattern observed in the real-world data from 1900 to 2005.
The implications of a slowing AMOC extend far beyond this cold spot. The circulation system has a significant influence on weather patterns across North America and Europe by affecting the position and strength of the jet stream, a high-altitude river of air that steers storms and weather systems. A weaker AMOC means less heat is transported northward, which can lead to altered rainfall patterns and more extreme weather events. Furthermore, the changes in ocean temperature and salinity can disrupt marine ecosystems, impacting the habitats and survival of numerous species that are adapted to specific oceanic conditions.
This research helps settle a key debate among climate scientists about whether the warming hole was primarily caused by ocean dynamics or by atmospheric factors, such as industrial aerosol pollution. By showing that models with a weakening AMOC best fit the observations, the study indicates that many recent climate models may have overestimated the influence of aerosols. This refined understanding strengthens the accuracy of future climate projections, providing a clearer picture of how Earth’s systems will respond as greenhouse gas concentrations continue to rise and further impact this crucial oceanic circulation.
References
- Bernstein, J. & University of California-Riverside. (2025, June 21). Strange Atlantic cold spot linked to century-long slowdown of major ocean current. Phys.Org; University of California-Riverside. https://phys.org/news/2025-06-strange-atlantic-cold-ocean-slowdown.html
- Li, K.-Y., & Liu, W. (2025). Weakened atlantic meridional overturning circulation causes the historical north atlantic warming hole. Communications Earth & Environment, 6(1), 416. https://doi.org/10.1038/s43247-025-02403-0
