The answer to that question is simple: yes. First, if the Atlantic circulation (AMOC) were to collapse, Europe would experience a sudden cooling, which, paradoxically, would be a consequence of global warming. But that's not all.
A Frightening Prospect
"Few people realize that if such a collapse were to happen, sea levels around the entire North Atlantic could rise by about 20-30 cm instantly. Circulation causes the Atlantic to have a lower sea level than it would otherwise. Why instantly? Paleoclimate data from the cold period at the end of the last ice age indicates that circulation changes can occur within a single year" - explains Prof. Jacek Piskozub of the Institute of Oceanology, Polish Academy of Sciences.
One year seems shockingly short - climate change usually unfolds over decades. But scientists know this because it’s happened before. During the last ice age, a collapse in AMOC halted the end of glaciation for years—a period known as the Younger Dryas. "If that effect were to happen again, it would add to the slow but steady sea-level rise caused by climate warming and glacial melting," points out Prof. Piskozub.
Recently, studies have reemerged, suggesting that the Atlantic current system might collapse soon (in our lifetime). This would be a catastrophic scenario. Is it realistic? We asked a Polish Academy of Sciences expert for clarification and opinion.
Why is AMOC Important?
Many may not realize just how crucial Atlantic Ocean circulation is for Europe, the living conditions there, and perhaps even its history. The current system, known as AMOC (Atlantic Meridional Overturning Circulation) or thermohaline circulation, plays a critical role in shaping Europe’s climate. Thanks to it, southern Europe is as warm as it is, and in the far north, like the Norwegian Lofoten archipelago, ports do not freeze even in winter. How does it work?
"The Atlantic receives less freshwater from rainfall - blocked by the mountains in North America—than it exports to the east. This makes the North Atlantic saltier than the North Pacific, enabling deep water formation. This mixing releases heat into the atmosphere, helped by strong winter storms that mix water to depths of 3 kilometers, releasing a heat stream comparable to that received from the Sun in summer. The Atlantic is the only ocean that transports heat from the southern to the northern hemisphere; normally, heat flows from the equator to the poles. And this Atlantic heat goes largely towards warming Europe in winter. That’s why Italian cities have a warm climate, despite being on the same latitude as some Canadian cities," explains Prof. Piskozub.
Without this "heater" system - of which the Gulf Stream is a part - Europe’s climate would cool significantly. Some say temperatures could drop by more than a few degrees, possibly as much as a dozen degrees Celsius in some places, like parts of Ireland. The weaker or nonexistent AMOC circulation would likely alter weather patterns, affecting not only Europe but other parts of the world. And that’s still not all.
"Eighty percent of the deep water in the Earth’s oceans is produced in the North Atlantic. If that stops, like in the ice age, the deep ocean will be deprived of oxygen and cut off from the surface. This would also have a consequence, which may sound beneficial to us - carbon would become trapped on the ocean floor. But it would also mean a fundamentally different ocean environment for marine life - oxygenless deep waters," says the IO PAN expert.
Rising Concerns: Recent Research Findings A few weeks ago, the AMOC circulation was back in the media spotlight, thanks to an appeal by dozens of scientists to the governments of Northern Europe. In their letter, the experts warned ("urgently drawing attention") against underestimating the climate threat posed by the "significant risk of a major change in Atlantic ocean circulation". They emphasized that the collapse of ocean currents would have "devastating and irreversible consequences, especially for Nordic countries, but also for other parts of the world".
"We all agree that if a lot of freshwater is added to the North Atlantic, it could stop the circulation. The question is, when will this happen? None of the models we’ve tested to predict this directly have shown a collapse happening this century. By the end of the century, the amount of heat carried by this circulation may decrease—by how much depends on the model, but the average estimate is around one-third. Perhaps we are witnessing the start of this process, but a sudden collapse in the near future is far from certain," says Prof. Jacek Piskozub.
Where could the extra freshwater in the North Atlantic come from? Melting glaciers, especially Greenland. So, this is a real threat—as global warming causes more intense melting in this region, and scientists fully agree on this. Therefore, what we are doing to the climate drives the melting, which could have a profound impact on ocean currents. We just don’t know when the process will reach a tipping point strong enough to collapse the AMOC.
