In a 2004 film "Day After Tomorrow," a climate scientist, played by Dennis Quaid, has lectured world leaders on global warming. Climate change caused by man, he warned, could cause cataclysm in the ice age.
Although the concept of global warming leading to a cooling trend seems contradictory to intuition, Hollywood's film about the crash does not necessarily have to be wrong. The real show star (sorry, Denis Quaid) is an oceanic fluid called AMOC, which moves warm water from equatorial tropics to Europe and the northern Atlantic. This influx of warmer water contributes to the mild, moderate climate in Western Europe.
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In the film, the current stops cause almost one-night ice age in Europe and North America. Temperatures drop to 1
These effects (and the speed at which they appear) are hyperbolised in the movie in the name of film lovers, but the idea that the Atlantic Ocean's water circulation may close is not out of the box. In fact, such a change has already begun. According to a study in 2018, circulation has been the worst for at least 1600 years.
"We are definitely going into a world where AMAC is becoming weaker," said Francesco Musquisto, author of a new study for AMO. Mushtitilo's research, published earlier this month in Nature Communications, suggests a potential time line for the cause and effect of this slowdown. According to the model of the new study, AMOC changes predict large climate fluctuations that will happen about 400 years in the future.
The results show that the changes in the power of the Atlantic water circulation really precede the sudden climate changes – something like a proverbial canary in the climate mine.
The Atlantic Conveyer
AMO carries ocean waters north and south into the Atlantic, while spreading it from the surface to the depths of the water. Scientists compared the system with a conveyor belt.
Once warmer water reaches the area around the United Kingdom, it cools and sinks to the bottom of the Labrador and the Scandinavian seas. Then this cold water turns a turn and sneaks down the ocean floor to the South Ocean of Antarctica. The Atlantic meridional transfer circulator brings warm tropical water to the North Atlantic (in red), where the water cools and sinks before it flows south (blue).
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Adding this fresh water makes the salty surface water lighter and less likely to sink by clogging the flow of circulation.
Changing the AMO could cause climate change 400 years later
The new study gives us an idea of how quickly cooling AMOC has triggered during climate change in the past – information that can serve as a model for the future.
To make their analysis, Mushtieillo and his team looked at core samples drilled from the bottom of the Norwegian Sea, a lake in Southern Scandinavia and ice in Greenland. Their results showed that AMOK began to weaken approximately 400 years before a major cold 13,000 years ago. The AMO also began to grow stronger around 400 years before the rapid warming 11,000 years ago (during which temperatures climbed 14 degrees Fahrenheit). The authors note that after these 400-year delays, rapid warming or cooling have only occurred for a few decades or less.
"It's madness," Mushtitielo said. "If you look at ice cores, there are some climatic indicators that suggest a shift of 2 to 5 years." Muskiteillo's studies are the first to calculate how quickly change in AMOK causes a change in the global climate.
But he does not think today's melting of the ice is enough to trigger the dramatic delay of AMOK, which the world saw 13,000 years ago. "It's really scary though," he said. "You see that AMOK has been slow in the last few centuries." Can the current stop completely?
According to Muschietylo, "there are reconstructions that suggest that AMO has completely stopped in the past and that these large distortions of AMOK have led to the coldest events ever recorded." But such an event would require a significant amount of melt. The distortions of the past, Mushtitielo, mean that it happened after the big swarms of icebergs interrupted the glaciers and slid into the North Atlantic Ocean. When the iceberg ardors melted, it added a surplus of fresh water in the ocean that caused chaos in the AMO.
But this type of fresh water flow is a few orders of magnitude higher than today's melting rates. "If Greenland's glacier cover melts for several days, that would probably be bad," Mushtitielo said.