The Atlantic Ocean Current

This article explores what the Atlantic Meridional Overturning Circulation is, its importance to the planet, and its tipping point for demise.

Written by: Thomas Tinmouth

This summer has really been unlike any other for a multitude of reasons. First off, we proudly watched our Canadian athletes have a historic summer Olympic Games, but with no fans in attendance. Our Canadian Women’s National Soccer Team won gold, the day after the game was supposed to be played due to temperatures being in the high 40s. We saw Canada set records with the hottest temperatures ever recorded in the West, with wildfires ravaging the forests. If the wildfires and extreme heat that have swept the globe this summer are not enough to show you that our current actions are destroying our planet, here’s one more thing to add to the list. The Atlantic Ocean Current, more specifically called the Atlantic Meridional Overturning Circulation (AMOC), is losing its stability. 

What is the Atlantic Meridional Overturning Circulation and how Does it Work?

_{Figure 1 – Video on what the AMOC is.}

So, what exactly is the Atlantic Meridional Overturning Circulation (AMOC). The AMOC is like a conveyor belt for the Atlantic ocean circulating and distributing heat and nutrients through the world’s ocean basins. It starts in the Tropics where warm water on the surface of the ocean flows North. By the time this current reaches Greenland, it has mixed with enough water laden with salt that it can sink deep beneath the surface. This bottom current water then pushes back south toward Antarctica where it mixes and is distributed to various other ocean basins via the Antarctic circumpolar current. The AMOC is critical to the planet because it is like a balancing act for our earth’s oceans. Earth’s climate system depends on this circulatory current to redistribute heat and regulate weather patterns worldwide.

What is causing the AMOC to Weaken?

_{Figure 2 – AMOC current pattern.}

Yes, you guessed it, climate change. There are two main results of a changing climate that are tampering with the AMOC. As temperatures around the globe get hotter, so does the temperature of the ocean. Warmer oceans mean the water is lighter and sticks closer to the surface, hindering its ability to sink to the bottom which is a necessary part of this current system. The second reason is that warmer temperatures cause ice sheets and glaciers in the north to melt, pouring in large amounts of freshwater diluting the saltiness of the North Atlantic. When the AMOC passes through the North Atlantic it mixes with this influx of freshwater and reduces the water’s density. If the waters in the AMOC current are not dense enough to sink, then the circulation will be hindered and the AMOC can actually shut off.

The Tipping Point

_{Figure 3 – Loss in Sea ice from 1950’s to 2050’s.}

It is difficult to predict exactly when the tipping point is for the AMOC to be irreversibly damaged. The good news is this time frame is in decades to centuries rather than years as it takes time to slow the oceans circulatory system. Just because there is time does not mean the action is not necessary. The consequences of an AMOC collapse would be devastating. The AMOC is responsible for the mild climate in Europe and the east coast of America. Without this current modelling has shown an intense cooling in the Northern Hemisphere and decreased rainfall in Europe. Studies have shown that a similar event has taken place in the past near the end of the last ice age. A massive glacial lake popped and flooded fresh water into the Atlantic, stopping the AMOC. The result was Europe and North America fell into an intense spell of cold that lasted for 1,000 years. Stefan Rahmstorf was part of a study on the AMOC published by Nature Geoscience and says “If we continue to drive global warming, the Gulf Stream System will weaken further – by 34 to 45 percent by 2100 according to the latest generation of climate models. This could bring us dangerously close to the tipping point at which the flow becomes unstable“

_{Figure 4 – Impacts from climate change seen around the globe.}

If there was any more concrete evidence needed to sway your life in the direction of living more sustainably then hopefully this does it. Though the collapse of the AMOC is most likely many years away, and probably not going to happen in our lifetime, there are many other systems that are imperative to our earth’s climate with much shorter time frames for demise (the Amazon). One thing we are not coming up short on is facts and research about the changes in our earth’s climate. We have been presented the information, now we must listen and act on it. Share what you know, and spread the word that future generations are at risk. It is up to us right now to alter our direction.