Global climate-regulating ocean currents at risk of ceasing circulation

A new study warns of the risk that a vital ocean current in the Earth's climate system could stop circulating in the near future.

Warming oceans and melting ice are threatening to destabilize a vital Atlantic current system - Photo: REUTERS

The Atlantic Meridional Overturning Circulation (AMOC) is a key ocean current that regulates global climate. It carries warm water from the tropics up to Europe and the Arctic, where it cools and sinks, forming a deep-sea countercurrent.

According to research published in the journal Environmental Research Letters cited by the Guardian on August 28, AMOC is at its weakest level in 1,600 years due to climate change.

If the AMOC were to fail, the consequences would be dire. The tropical rain belt would shift, threatening the food security of hundreds of millions of people around the world; Western Europe would suffer from extremely cold winters, drought-stricken summers, and global sea levels would rise by about 50cm. Scientists have long warned that this is a scenario that “must be avoided at all costs.”

Previously, climate models showed a low chance of the AMOC ceasing to circulate before 2100. However, with projections extending to 2300-2500, the new study suggests that in just a few decades, the AMOC could cross a tipping point—the point at which collapse becomes certain, although it could take another 50-100 years.

Professor Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research (Germany), a member of the research team, said the tipping point "will probably occur within the next 10-20 years".

The study found that if carbon emissions continue to rise, 70% of climate models show the AMOC will collapse. At medium emissions, that number is 37%, and even in a low-emissions scenario, a collapse is still possible in 25% of models.

"These results are quite shocking, because I have always said that the probability of AMOC collapse due to climate change is less than 10%," Professor Rahmstorf emphasized. "This is a matter of risk assessment, and even 10% is too high."

Warning signs of a tipping point have been evident since 2021, and AMOC has collapsed in the past.

"Observations in the North Atlantic over the past 5-10 years show a decreasing trend in the AMOC, consistent with model predictions," said study co-author Professor Sybren Drijfhout of the Royal Netherlands Meteorological Institute.

Due to climate change, the Arctic is warming rapidly, making it difficult for seawater to sink. Warmer water is lighter, and more rain dilutes the salinity, further hindering the sinking process.

This loop is self-amplifying and could push the AMOC to a tipping point around mid-century.

The real situation could be even worse, Mr Rahmstorf said, because the models did not take into account the huge amount of meltwater from Greenland ice - a factor that is diluting the ocean's salinity.

Despite differing opinions, experts agree that the risk of AMOC ceasing to circulate is much greater than previously assumed. Dr. Aixue Hu (USA) said that more data is needed to determine the exact time of collapse, while some experts said that the worst-case scenario is unlikely to happen this century.

However, the weakening of the AMOC is certainly happening and is enough to cause major changes to Europe's climate in the coming decades.

XUAN THAO

Source: https://tuoitre.vn/dong-hai-luu-dieu-tiet-khi-hau-toan-cau-nguy-co-ngung-luu-thong-20250831130153551.htm