Danish Research Team Publishes Paper in Nature
Atlantic Meridional Overturning Circulation Likely to Disappear Within Decades
A study has revealed that the Atlantic Meridional Overturning Circulation (AMOC), one of the deep ocean circulation systems that plays a crucial role in Earth's climate system, could begin to collapse starting in 2025 and may disappear entirely within a few decades.
On the 26th (local time), a research team led by Professors Peter and Susanne Ditlevsen from the University of Copenhagen in Denmark published a paper in the international journal Nature Communications, reporting that based on observations of North Atlantic sea surface temperatures and ocean currents from 1870 to 2020, the AMOC could completely vanish before 2095.
It could nearly disappear as early as 2025, with a high possibility of fully stopping within this century. The median estimate is 2050.
The AMOC is a representative deep ocean circulation in the Northern Hemisphere, starting near the Gulf of Mexico and including currents flowing along the eastern coast of North America. Deep ocean circulation involves cold polar seawater sinking deeply and flowing toward warmer equatorial regions. This circulation supplies heat, carbon, oxygen, and nutrients to the oceans and influences various climate system changes such as sea level, temperature, and composition.
The collapse of such an important ocean circulation is considered one of the tipping points in the Earth's climate system?points beyond which changes become irreversible. The researchers expressed concern that the AMOC is currently at its weakest level in 1,600 years.
According to the paper, the ocean circulation has become significantly unstable over the past 150 years. As global temperatures rise, polar ice melts, and freshwater inflow lowers salinity, seawater sinks more slowly at high latitudes.
The research team explained that the last collapse of the AMOC occurred 12,800 years ago during the last Ice Age. At that time, Earth's temperature changed by 10 to 15 degrees Celsius within a decade?a much larger change than the 1.5-degree variation observed over the past century.
Scientists are raising their voices that the collapse of the AMOC must be avoided at all costs. Consequently, there is heated debate about the timing of the collapse based on current greenhouse gas emission trends.
The research team concluded that if greenhouse gas emissions continue as currently planned, the AMOC could collapse by 2095, possibly as early as 2025. The most likely collapse period is between 2039 and 2070. Professor Peter Ditlevsen, who participated in the study, described the findings as "frightening" but also stated, "However, we have strong confidence in the (AMOC collapse) prediction."
The team noted, "This conclusion is based on the assumption that predictive models are nearly accurate," but added, "Other mechanisms could also be at play, so uncertainty may increase, and partial collapse of the AMOC is also possible." However, they emphasized, "The analysis and projections in this study are based on conservative assumptions as much as possible," and stressed, "Considering the importance of the AMOC in the climate system, clear indicators suggesting an imminent collapse should not be ignored."
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