What if the ocean stops circulating?

I remember back in the first year sitting down in an environmental science lecture when my professor asked the whole class “What if the global ocean conveyer belt collapse?”. (Also, I know, big words). Of course, like any other university lectures, no one answered anything except a few whispers here and there. Well, all I could think of that time was “Guess it will be slow descend to madness”.

Day after tomorrow visualisation photo by Morrison via Flickr.

The shutdown of the global conveyer belt sounds like something out of fiction but what would happen if the ocean circulation slows down and ‘collapse’?


What a relief.

But what are some of the ramifications from the slowing down of the ocean current?

How does the global ocean circulation regulate the weather system?

The big question is, how does the ocean even begin to circulate?

The Atlantic Meridional Overturning Circulation (AMOC) is the ocean current pattern helping to regulate the weather system carries warm water from the Southern Hemisphere and the North and to the North Atlantic. AMOC is a part of the thermohaline circulation that comprises of the warm gulf stream. In simple term, since the salinity and temperature of the water vary (slightly) from places affect the density of the water, this ocean stratification allows water to be transported from one region to the other.

We all know cold water is denser and tends to be saltier from the sea ice. In high latitude regions like the North Atlantic, this dense cold water will sink deep into the ocean and is transported southwards to the equator (Indian Oceans). As it is generally warmer in the equator, the water gets heated up and becoming less dense and will rise. Since the rate of evaporation is higher in warmer region, the warm water will be salty as well. This warm salty water follows a northwards trend joining the Gulf Stream bringing warmth to Western Europe. When the water releases this heat (by this time the current will be reaching the North Atlantic back again), the water becomes cold once again. This endless cycle continues.

So what if the ocean current is weak?

Thermohaline circulation is highly depended on water density whereby the denser cold water will sink deep into the ocean and start the circulation cycle. When the earth is warm due to global warming, ice sheets at the pole will melt. The melting of ice sheets adds volume to the freshwater making the salinity level lesser than usual preventing the cold waters from sinking. This disrupts the ocean current pattern.

The weakening of the ocean currents brings about some weather change in some parts of the world. Europe will experience more hot and intense summer while in the topics, there will be a different rainfall and monsoon pattern.

No one would have thought the ocean circulation will come to a halt one day and researchers all around the globe have published numerous studies convincing us the population that yes, the ocean will slow down, but it would probably not be going to stop circulating.