We are all connected by one ocean, which moves water, heat, nutrients, dissolved gasses (such as oxygen and carbon dioxide), and microscopic life around Earth through ocean currents.
The Atlantic Meridional Overturning Circulation (AMOC) is a complex system of ocean currents and eddies (circular currents of water) that form a huge vertical loop spanning the whole length of the Atlantic Ocean.
What does the AMOC do?
In the Atlantic Ocean, the AMOC drives warm water northwards along the ocean’s surface and cold, deep waters back southwards. This delivers heat and nutrients to colder latitudes and transfers carbon to the ocean depths.
Every second, it moves an incredible 17 million cubic meters of water northwards, equivalent to 6,800 Olympic-sized swimming pools! This moves 1.2 Peta Watts (PW) of heat, which is about 100 times bigger than the total global energy production on Earth from all power sources.
The AMOC is critical in regulating the climate in Europe. For example, the mild winters experienced in the UK and north-western Europe are partly due to the AMOC bringing heat northwards from southern latitudes.
How does climate change impact the AMOC?
The atmosphere and ocean are interconnected: as climate change makes air temperatures warmer, the ocean surface also becomes warmer. This warming leads to more freshwater (from additional precipitation and melting ice) entering subpolar regions from Greenland and the Arctic.
Fresher and warmer waters at the ocean surface are less dense, meaning they do not sink as deep as they would during cooler conditions. The slowdown of this process reduces the rate at which the Ocean can transfer carbon dioxide from the atmosphere to the ocean depths, leading to larger amounts of greenhouse gases remaining in the atmosphere, accelerating changing climate.
Are the AMOC and the Gulf Stream the same thing?
The Gulf Stream is commonly confused with the AMOC itself. The Gulf Stream is an important part of the AMOC system, but how do they fit together?
Gulf Stream
The Gulf Stream is a surface current in the ocean that is partly driven by the wind. If you think of this as part of a transport system like our roads, it acts like a motorway for part of the journey taken by the warm water through the AMOC, as it travels from the South Atlantic to the far north. When this ‘motorway’ ends, the warm water takes different ‘A’ roads as it continues its journey northward.
How do scientists measure what’s happening in the AMOC?
Scientists measure the AMOC using scientific instruments deployed in different latitudes across the North and South Atlantic Ocean.
The National Oceanography Centre (NOC) is the UK lead of two international programmes in the North Atlantic: Rapid Climate Change (RAPID) and UK Overturning in the Subpolar North Atlantic (OSNAP).
Both programmes deploy sensors attached to wires that are hundreds to thousands of metres deep, known in oceanography as moorings. These instruments have special sensors attached to them which measure things like ocean current speed, temperature, salinity and direction of the water crossing the arrays.
Scientists use these measurements to inform climate models, which give them a glimpse into the future and make predictions about what could happen to the AMOC as our climate changes.
AMOC Impacts
Without an effectively operating AMOC, we will likely experience increasingly extreme weather systems, with the potential to impact everyone on the planet.
Will the Atlantic Meridional Overturning Circulation (AMOC) slowdown or collapse?
With human-caused climate change continuing to increase global temperatures, scientists say it’s likely that the Atlantic Meridional Overturning Circulation (AMOC) will slow down. But what does this mean for people and our planet?
What does current research tell us?
Climate models show it’s very likely that the AMOC will slow down throughout the 21st century. The AMOC could shut down completely, which would have even more severe impacts on our planet and people. However, scientists think this is very unlikely, and is what’s known as a low-risk, high-impact climate tipping point.
Scientists use complex climate models combined with ocean circulation measurements to make predictions about the AMOC, but due to uncertainties in these methods, the potential for a complete collapse of the circulation is subject to ongoing research and debate.
Therefore, it’s critical that we maintain AMOC observing arrays, which are crucial in understanding and predicting the potential impacts of an AMOC slow down or collapse.
If the AMOC were to slow down or collapse, what would the impact be on our planet?
Cooling of Northern Europe: The AMOC transports warm water from the tropics northward, contributing to the relatively mild climate of Western Europe and the UK.
A slowdown or collapse of the AMOC would disrupt this northwards heat transport, possibly leading to a cooling of Northern Europe. While this might seem counterintuitive given climate change trends, it's important to note that regional climate effects can differ from the global trend due to complex interactions between ocean currents, atmospheric circulation patterns, and other factors.
Changes in Weather Patterns: The slowdown or collapse of the AMOC could also alter atmospheric circulation patterns, potentially leading to changes in precipitation patterns, storm tracks, and the frequency and intensity of extreme weather events.
Sea Level Rise: Changes in the AMOC may also influence sea level rise along the UK coastlines and beyond. For example, in 2009-2010 a short-term reduction in the AMOC caused a 13cm increase in sea level along the New York coastline. In addition, a slowdown in the AMOC may lead to a redistribution of ocean heat, potentially causing sea levels to rise more rapidly in some regions due to the thermal expansion of seawater.
Impacts on Marine Life: The AMOC plays a crucial role in transporting nutrients and regulating oceanic circulation patterns, which in turn influence marine ecosystems. A slowdown or collapse of the AMOC could disrupt these ecosystems, impacting fisheries and other marine resources.
Global Climate Feedbacks: Changes in the AMOC could have broader implications for global climate systems. For example, a slowdown in the AMOC could affect the distribution of heat and moisture around the world, potentially influencing global climate patterns such as the El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD).
Could a collapse or slowdown of the AMOC lead to a scenario like in The Day After Tomorrow film?
No. In the film the Day After Tomorrow a collapse in the AMOC takes place over a matter of days and the fictional weather immediately switches to extreme cold so the characters are completely unprepared. Such a rapid transition will not happen in real life, and if the AMOC does reach a tipping point it will happen over several decades at least.
However, a slowdown of the AMOC, whether it is fast-acting or takes place over many decades, will lead to major changes in regional climate as well as the generation of more extreme and violent weather systems that have the potential to cause major damage to people and property.
** Add page to config of the ‘It’s time to turn the tide – donations’ block **
It’s time to turn the tide. Will you help our ocean thrive?
Knowledge is power. Without the knowledge, we lack the power to make change.
By deepening understanding and sharing knowledge of our ocean, we create opportunities for people to play a part in shaping a healthy future for it.
Will you be part of an Ocean Alliance, working to build a world where everyone feels empowered to make the change we need for a thriving ocean?