L’Atlantic Meridional Overturning Circulation (AMOC) is a complex system of ocean currents that plays a key role in regulating global climate. This mechanism, often compared to a giant conveyor belt, transports warm, salty water from the Gulf of Mexico to Northern Europe. Along the way, these waters cool and plunge into the depths of the Atlantic Ocean, creating a perpetual motion that influences temperatures and precipitation on a global scale.
The importance of AMOC cannot be underestimated:
- It softens the winters in Western Europe
- It regulates monsoon patterns in the northern hemisphere
- It contributes to the stability of marine ecosystems
- It impacts global weather patterns
Unfortunately, recent studies published in Nature Geoscience reveal that the AMOC is lower today than it has been over the last millennium. This worrying situation is largely attributed to global warming of anthropogenic origin.
The impact of melting ice on ocean circulation
Global warming has particularly marked consequences in the Arctic regions. Since the industrial revolution, the Earth has warmed by 1.5°C on average, but the Arctic is warming almost four times faster than the rest of the planet. This dizzying rise in temperatures is leading to massive melting of polar ice and continental glaciers.
The researchers have highlighted the considerable impact of this melting on the AMOC:
| Source of cast iron | Impact on AMOC |
|---|---|
| Greenland Ice Sheet | Massive supply of fresh water |
| Glaciers canadiens | Dilution of salt water |
| Arctic sea ice | Change in water density |
The influx of fresh water from melting disrupts the diving mechanism of cold and salty water, thus weakening the Gulf Stream and, by extension, the entire AMOC. This phenomenon could have major climatic repercussions on a global scale.
The potential consequences of a collapse of the amoc
A significant slowdown or collapse of the AMOC would have profound implications for the global climate. Scientists predict several worrying scenarios:
- Cooling of Northern Europe : Winters could become much harsher, similar to those observed in Canada at the same latitude.
- Disruption of tropical monsoons : Rainfall patterns in the northern hemisphere could be seriously affected, impacting agriculture and food security.
- Accelerating warming in the southern hemisphere : The thermal imbalance between the two hemispheres could increase.
- Sea level rise : The continued melting of the Greenland ice sheet could lead to a rise in ocean levels of around 10 cm.
The most recent modeling suggests that these changes could occur much more quickly than initially thought. According to the researchersthe AMOC could weaken by 30% by 2040, two decades earlier than previous estimates.
Towards urgent and global climate action
Faced with accelerating ice melt and slowing AMOC, the scientific community is calling for immediate and ambitious climate action. The drastic reduction of greenhouse gas emissions appears to be the only viable solution to preserve the fragile balance of our climate system.
The stakes are colossal and time is running out. There global climate stabilitythe preservation of ecosystems and the food security of millions of people depend on our ability to act quickly and effectively. Every action, no matter how modest, counts in this race against climate time.
The collapse of the ocean circulation system is no longer a distant hypothesis, but an ongoing reality. Our understanding of the complex interconnections between oceans, atmosphere and cryosphere is being refined, revealing the urgency of unprecedented mobilization to preserve the habitability of our planet.
https://www.nature.com/articles/s41561-024-01568-1
