The Great Ocean Conveyor Threat

Guess what, gang! The biggest threat to life on Earth isn't a large asteroid or a comet collision, a gamma ray burst, or a coronal mass ejection. It's the fact that the great ocean conveyor will shut down, causing a massive extinction of life. This has happened before to cause a major extinction of life 250 million years ago.

The great ocean conveyor is also called the Thermohaline circulation. The reason is because it involves the fact that salt (haline) water is heavier than fresh water and thus sinks. This happens at the poles. Melting glaciers feed fresh water into the oceans and the warming oceans at the equator act as a thermal pump to make a current run around the Earth's oceans. Warm water is less dense and rides on top while cold water rides on the bottom. This current is strong and is the reason that Northern Europe and America are habitable. Without the current, they would covered in ice.

Here is what happens: Deep-water masses that sink are formed at specific locations in the North Atlantic and Southern Ocean. Water is cooled in the North Atlantic by cold winds, which also cause further cooling by evaporation. This results in increased salinity, which forms a deep water mass. A similar action occurs in the Antarctic. The end result is that these dense water masses sink under less dense water and create a flow. It's like water running down a hill.

These sinking masses of cold water form currents. The Gulf Stream is one of these and it flows to Europe, warming the British Isles. This is very important to Britain, and in 2007 British researches noted a 20% drop in the current since 1957. The danger here is from the more rapid melting of glaciers, which adds too much fresh water to the oceans. This dilutes the salinity, which is needed for these deep masses of water to work. If this Gulf current shuts down or diverts from Britain, it could mean a drastic change in the climate there.
The main current in the Atlantic is officially known as the Atlantic Meridional Overturning Circulation (AMOC).

These deep ocean currents flow all around the Earth's oceans, both in the Atlantic and the Pacific in a conveyor belt fashion. They are responsible for transporting oxygen and carbon dioxide into the deep parts of the oceans. Without this effect, marine life would go extinct and climates around the globe would be drastically changed. And, the scary part is that global warming of the oceans could cause this to happen.

There is some evidence that the Gulf Stream has already shut down or has slowed appreciably, especially in regard to its interaction with the West Greenland Current, and this could be the reason that the Artic is warming up and the ice is melting too much. It also could be the cause of some strange behavior with storms.

There is also a theory that a shutdown of the AMOC could cause another ice age. This would result in much colder weather patterns in Northern Europe and North America. I believe that there is not enough known about how these ocean currents work and their interaction with weather. The only thing that could be said about this is the fact that the ocean currents have not been constant throughout Earth's geological history. The Earth's climate has changed drastically over millions of years. What happened in the past could happen again. There are no guarantees.

Thanks for reading.