Research Finds AMOC Overturning Faster Than Originally Thought

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Climate adaptation Ocean’s AMOC overturns more rapidly than previously thought – up to “sixfold a year”

The ocean consisting of 71% of the earth’s surface, acts as a more potent regulator of the earth’s temperature than the atmosphere, a reality humans often overlook.

According to the Economist, without the movement of the seawater near the equator to the poles and vice versa through the Atlantic Meridional Overturning Circulation (AMOC), the temperature difference between the poles and the tropics would be around 110°C, compared to the 30°C because of it.

The article says that because humans are a dry-land species, we tend to focus more on the earth’s atmosphere to study the climate and forget the ocean’s role – which is far greater. The climate is driven by heat, and although the atmosphere and oceans circulate the heat, redistributing it across the globe, the ocean, in many ways, is more important than the other.

It not only absorbs the heat which would otherwise remain in the atmosphere making the climate change effects worse, but it also soaks up a third of carbon dioxide emissions from human activities, storing it deep in the abyss for many centuries and not adding to the greenhouse effect on the planet.

It was not only towards the end of the 20th century that oceanographers discovered that the AMOC’s engine room is in the North Atlantic, where warm water coming from the tropics to the Atlantic cools down and sinks to the bottom – up to 3 kilometres deep, pulling moisture to the surface to replace it. As a result, the cold water that has sunk will begin to move southward.

This overturning that occurs is responsible for 90% of the transfer of seawater from the surface to the deep, driving the world’s system of currents, also known as the “global conveyor belt.” The overturning of ocean water also results in surplus heat and CO2 burial.

Another critical matter pointed out by the Economist article is the findings of the 2005 study in Nature that reveals a 30% drop in the volume of AMOC between 1992 and 2004 is erroneous. The report says that if the AMOC is slowing down, it poses a serious concern as it could change weather patterns, particularly in Europe, and reduce the ocean’s ability to absorb CO2.

Thankfully 2004 was the year of deployment of a set of recording instruments known as RAPID AMOC in the same area where these surveys for the 2005 study were conducted. In 2014 RAPID AMOC was joined by an arctic counterpart, OSNAP (Overturning in the Subpolar North Atlantic Programme).

“The upshot has been the discovery that the rate of overturning can vary, apparently at random, as much as six-fold during a year. The fall described in the Nature paper was an artefact of an impoverished data set” on the “basis of the five pertinent shipborne surveys which had been made since 1957.”

Another discovery from the RAPID AMOC and OSNAP is that most of the overturning in the North Atlantic occurs on the east rather than the west side of the ocean. Although this new finding may not matter much, it is yet another example of how we could have better understood what is happening in the sea.

The next goal for the OSNAP is to look at the carbon dioxide uptake of the ocean.

The AMOC is known for regulating the ocean’s temperature, circulating water from north to south and back, bringing warmth to various parts of the globe, and cold water from the north to the tropics. Previous studies show that the AMOC is slowing down and could worsen the effects of climate change.

However, the Economist article states that new findings debunk the idea that it is slowing down and reveals that the overturning of warm through the global conveyor belt could occur six-fold a year. This finding will undoubtedly have an important implication on climate change and its projected impacts.

Read the full article by clicking the link in the “Source” section below.


The ocean is as important to the climate as the atmosphere. (2023, March 8). The Economist. Retrieved from

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