According to new research, a shutdown of a major current in the Atlantic Ocean would transform wind, temperature, and precipitation patterns around the world.
Climate change is likely to be a factor in the slowing of the current. There would be never-before-predicted impacts if the AMOC collapses completely, according to a study published last week.
Without the AMOC the tropical Pacific Ocean cools and trade winds intensify. The resulting climate state would be similar to a permanent La Nia and could cause catastrophic monsoons and flooding in the South Pacific.
Climate chaos would be worse if human actions made the AMOC run amok.
There is a critical pattern of flow that moves warmer water from the south into the North Atlantic Ocean. It helps to regulate Europe's mild climate by transporting heat and carbon. London is very close to L'Anse-au-Loup in Canada's Newfoundland and Labrador but has an average January temperature that is 39 degrees hotter.
The conveyer belt is driven by heat and salty water. Water is pushed around by differences in density. Currents and the relative temperature of water change as ice is melted. At times the AMOC has stopped and at other times it has shifted.
The last time the AMOC slowed down was at the end of the last ice age when the planet began to warm. The Northern Hemisphere was plunged back into cold weather for another 3000 years.
Since the 1950s, research has shown that the critical current has slowed due to atmospheric and ocean shifts caused by climate change. Climate scientists consider a collapse of the current to be a major tipping point, or an irreversible and worrying threshold, since the flow is so important.
The collapse of the AMOC isn't imminent just because it's slowing. A study published in April concluded that the current is less sensitive to ice melt and freshwater influx than was thought. The report projected that the AMOC will only slow down by about one-third by the end of the century. The Amazon Rainforest is close to being a major climate tipping point within our lifetimes.
You should know that there are more pressing apocalyptic benchmarks to focus on before you start to worry about a sudden Day After Tomorrow scenario.
If the ocean's current conga line hits a wall, what will happen? A full portrait of that possible but unlikely future can be found in the new study.
The Northern Hemisphere and most of the Atlantic Ocean get a lot colder without the AMOC. Over the course of a few decades, some sections of the North Atlantic and coastal Europe would experience an average temperature drop of more than 15 degrees Celsius.
The collapse of AMOC wouldn't just mean changes in the Atlantic Basin or the Northern Hemisphere, according to the researchers' models. Matthew England broke down the results with a map.
The northern Pacific Ocean would get cooler. There would be patches of the Northern Hemisphere that were dry. The atmospheric pressure would go up over parts of the northern hemisphere. The trade winds from the north would strengthen. Other winds would increase as well. The ice could melt more quickly.
Everything about the planet we know and love gets thrown out of whack. The new research shows that no corner of the planet will be unaffected by the collapse of the AMOC.
The collapse of the Atlantic overturning circulation has global climate impacts according to the study author. Orihuela-Pinto is a candidate for a PhD in oceanography. He said that an AMOC collapse changes the tropical Pacific ocean currents and winds in a way that resembles a La Nia mean state.
La Nia is the opposite of El Nio. Patterns of ocean surface temperature change atmospheric pressure. Every two to seven years, there are fluctuations. Parts of the South Pacific, southern China, and India get a lot of rain when La Nia occurs. A swathe of the southern US becomes warmer and dryer.
The worst flooding in Australia has been linked to La Nia.
I'm here to remind you not to freak out. This is not a projection study. Orihuela-Pinto wrote that their work only looked at what this might mean for global climate if the current collapses. Even if we work to mitigate climate change, nothing is certain.
The models were used to come to their conclusions. There are big limits to model-based studies and how definitive they can be.
According to a climate scientist at the University of Wisconsin-Madison who is not involved in the new study, their modeling methods are robust and in line with previous work. The paper is less convincing due to the lack of data verification.
The paleo record can be used to reconstruct what climates were like when the AMOC was slower. The study doesn't double-check the model's results by comparing them to the record I would like to see more studies to confirm this finding, as we have extensive proxy data in the past when AMOC was thought to be less strong.
We should look to the past for a better idea of our future. Climate change can affect how far back we need to look.
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