The Atlantic Meridional Overturning Circulation (AMOC), a massive oceanic conveyor belt current, is a complex grouping of water currents that move huge amounts of warm water from the tropics northward, from the Atlantic up toward the Arctic.
Thus, the AMOC plays a critical role in creating the mild climate of the UK and other parts of Western Europe. Without the AMOC, much of that part of the world would likely plunge into an Ice Age.
While scientists have long known the current is under threat from the impacts of anthropogenic climate disruption (ACD) — and, as Truthout reported last year, has already become a huge and growing contributor to global sea level rise — new, more accurate scientific modeling of the current now shows that the AMOC could literally collapse within 300 years.
A new study published in the journal Science Advances, titled “Overlooked possibility of a collapsed Atlantic Meridional Overturning Circulation in warming climate,” corrects for previous model biases and shows that if (or when) global atmospheric CO2 concentration is abruptly doubled from the 1990 level, the AMOC will collapse within 300 years.
If that doubling does prompt the collapse of the AMOC, it would have a profound impact on our planet. Given that the AMOC works to regulate both climate and weather patterns across the entire globe, its collapse could completely reshape what many parts of the planet look like.
Aside from transporting warmer water and atmospheric temperatures to the North Atlantic, the other functional aspect of the AMOC is that when the current reaches the North Atlantic, it cools, sinks towards the bottom of the ocean, and then flows southward again. Like other similar overturning conveyer belt currents, it plays a critical role in regulating both ocean and atmospheric temperatures across the planet.
Authors of the new study emphasize the fact that many climate models are constructed with the assumption of a stable AMOC. However, this stability should not be taken for granted. This incorrect assumption means that many climate predictions, as well as many models of oceanic changes, are deeply flawed. Thus, the new study corrects for this bias.
“By correcting the model biases, we show that the AMOC collapses 300 years after the atmospheric CO2 concentration is abruptly doubled from the 1990 level,” reads the study’s abstract. “Compared to an uncorrected model, the AMOC collapse brings about large, markedly different climate responses: a prominent cooling over the northern North Atlantic and neighboring areas, sea ice increases over the Greenland-Iceland-Norwegian seas and to the south of Greenland, and a significant southward rain-belt migration over the tropical Atlantic.”
In other words, in uncorrected studies — that is, studies that fail to account for dramatic atmospheric CO2 increases — the AMOC is predicted to weaken over time, but then recover to its normal state. The corrected study still shows the AMOC weakening over time, but, after three centuries, it predicts a complete collapse instead of a recovery.
Given that the AMOC is deeply tied to the global oceanic conveyor system, which works to transport warm and cold currents between the tropics and both the north and south poles, the new modeling from the study predicts a heavy impact on the Atlantic tropics.
The corrected model, according to the study, shows a strong warming pattern south of the tropics, which causes a dramatic shift in precipitation patterns across Central America and Brazil. For example, northeastern Brazil would see far more rain, while Central American countries would see far less rain.
The new model also shows a dramatic reduction in sea ice across the Antarctic, which is already in rapid decline, as Truthout recently reported.
The implications of this new AMOC study for climate modeling around the globe cannot be understated.
Speaking about the study, Thomas Haine, an expert on ocean circulation at Johns Hopkins University, told The Washington Post, “I would say that it is reasonably well-accepted that a current generation of climate models [is] missing the essential physics in representing the AMOC.”