The answer to the last of the above questions is short: yes. Firstly, if the Atlantic circulation (i.e. the AMOC) broke down, Europe would cool down rapidly – although paradoxically it would be a result of global warming. But that's not all.
A terrifying prospect
– Few people realize that if such a breakdown occurredsea level around the whole the North Atlantic could rise by about 20-30 cm. And that right away. The circulation causes the Atlantic to be lower than it would be without it. And why immediately? Paleoclimate data from the colder period at the end of the last ice age indicate that a change in circulation can occur within one year – says prof. Ph.D. Jacek Piskozub from the Institute of Oceanology of the Polish Academy of Sciences.
One year seems to be a shockingly short period – climate change provokes processes that develop over years. But scientists know this because this has happened before. In the last ice age and there is evidence of it. The collapse of the AMOC interrupted the recovery from glaciation for many years – this period was called the Younger Dryas. – If this effect were repeated, it would contribute to a slow but continuous increase in sea level caused by global warming and melting glaciers – points out Prof. Piskozub.
Recently again research studies were cited and discussedwhich, according to their authors, indicate that the current system in the Atlantic may collapse soon (in our lifetime). This would be a terrible scenario. Is it real? We asked an expert from the Polish Academy of Sciences for an explanation and opinion.
AMOC is scary. What is it anyway and why is it important?
Perhaps many people do not realize how important the ocean circulation in the Atlantic is for our continent – for the living conditions on it, and probably for the history of the people living there. current system, called from English AMOC [Atlantic Meridional Overturning Circulation – Atlantycka Południkowa Cyrkulacja Wymienna] or else thermohaline circulation plays a very important role in shaping Europe's climate. Thanks to it, the European south remains as warm as it is, and in the far north, e.g. in the Norwegian archipelago of Lofoten, the ports do not freeze even in winter. How does it work?
– The Atlantic receives less freshwater from rainfall – because it is blocked by the mountains in North America – than it exports further east. That's why the North Atlantic is saltier than the North Pacific and that's why deep sea waters sink here. This causes mixing and heat is released into the atmosphere. This happens under the influence of strong winter storms that mix water up to a depth of 3 kilometers, releasing heat flux to the atmosphere comparable to what we receive from the Sun in summer. The Atlantic is the only ocean that transfers heat from the southern hemisphere to the northern one, because heat is normally transferred from the equator to the poles. And this Atlantic heat goes largely to heating Europe in winter. This is why Italian cities have such a warm climate, even though they are located at the same latitude as Canadian ones – explains prof. Piskozub.
Without the “radiator” that this system of currents is – a part of it called the Gulf Stream or the Gulf Stream reaches Europe – the climate would significantly cool down (some say not even a few, or in extreme scenarios a dozen or so degrees Celsius less than now, e.g. in some areas of Ireland ). In addition, the sea level on European coasts would rise significantly. Weaker Atlantic circulation (or lack thereof) would probably also change weather patterns, affecting not only our continent. And that's still not all.
– 80 percent deep sea water on Earth is produced in the North Atlantic. If this stops, as it did during the Ice Age, there will be no deep ocean oxygenwill be cut off from the surface. It will also have an effect that may suit us individually – coal will be trapped at the bottom of the ocean. But this also means a fundamentally different ocean for marine life – depths without oxygen – says the IO PAN expert.
What's the fuss about, i.e. disturbing research results?
The topic of AMOC's potential collapse comes up at least once a year. We wrote about it ourselves at least a few times – after the results of scientists' research were widely commented on. Here it is worth keeping in mind the process by which scientific consensus is formed. The mere publication of the results of a study in a journal does not mean that its conclusions become generally applicable and supported by all experts in a given field. They often provoke discussion, exchange of opinions and similar research by other teams so that it can be checked whether their results are repeatable.
A few weeks ago the Atlantic circulation appeared in the media space again, this time thanks to… appeal submitted by several dozen scientists to the governments of Northern European countries. In the letter, experts warn (“urgently pay attention”) against underestimating the climate threat, which is “a serious risk of a major change in ocean circulation in the Atlantic.” They emphasize that a breakdown of ocean currents would have “devastating and irreversible consequences, especially for the Nordic countries, but also for other parts of the world.”
– That's what you're up to we all agreethat if you add lots of fresh water into the North Atlantic, then you can stop this circulation. Question, When it will happen. All the models we use to test this directly have so far failed to show that a collapse could occur at this age. By the end of the century, the amount of heat carried in this circulation may decrease – by how much depends on the model, but the average is about one third. We may be seeing the beginning of this process right nowbut it is not certain that a sudden collapse is imminent – says prof. Jacek Piskozub.
Where could a lot of fresh water in the North Atlantic come from? From melting glaciers, especially Greenland. So this is a real threat – as a result of global warming, the ice in this region is melting more and more, and scientists fully agree on this. So what we do to the climate drives melting, which can powerfully affect ocean currents. We just don't know when the process will cross the tipping point enough to break the AMOC.
– This is an echo of scientific articles that are loud, but I do not entirely agree with their conclusions. There is no scientific consensus on them at all – says prof. Piskozub, referring to the above-mentioned letter of scientists.
In several of the articles, scientists argue that the Atlantic circulation system may collapse because this is indicated by the cooling of the region south of Greenland, the so-called subpolar vortex. However, as an expert from the Institute of Oceanology of the Polish Academy of Sciences emphasizes in a conversation with us, it is not certain that this vortex is cooling down because the AMOC is weakening.
– It so happens that over the last decade, the North Atlantic has experienced exceptionally strong winds from the west during winter. These winds, apart from bringing us very warm winters in Europe, cool down the very part of the ocean in question – south of Greenland – this correlation can be checked using historical data. These winds are part of the Jet Stream – the one that causes planes from Europe to America to fly in one direction faster than the other. The Jet Stream is getting stronger and this is a direct result of global warming. Therefore, it is certainly stronger because of us, because of our pressure on the climate, and probably – although there is no consensus here – also the atmospheric circulation at the Earth's surface, these winds from the west, are also stronger because of us – explains the IO PAN expert.
– There is also a second group of articles – two have appeared recently – based on statistical and mathematical analyses, similar to chaos theory. Modeling studies from these papers indicate that the thermohaline circulation (AMOC) can collapse very quickly. But these scientists themselves admit that their model does not accurately reflect how freshwater flows between the Atlantic and the rest of the world currently flow. The assumptions of their model are not realistic. Hence my skepticism – explains prof. Piskozub.
Does this mean that warnings about the consequences of AMOC are unnecessary? Absolutely not. Very disturbing things are happening to the climate thingswhich may affect a very important (especially for Europe) sea current system. There are signs that something unusual is starting to happen to him and such voices cannot be ignored. Scientists should – and will – continue to study the topic. We should all be aware of the consequences of various scenarios, including the most pessimistic one.
– Voices about the collapse of the Atlantic current system soon or in 20 years – which is also a not-too-distant prospect – are based on a model that we know does not work well. So far, no one has convincingly proven that this will happen in our lifetime. Direct measurements of this circulation do not indicate that it is significantly decreasing. Can be seen true slight decline in the last 10 years, but it is too small to draw such conclusions and it is not something that surprises us. You need it here be careful and continue to observe – sums up prof. Jacek Piskozub.