Changes in the Atlantic Ocean cycle are threatening climate

The Atlantic Meridional Overturning Circulation is a critical part of the Earth’s energy balance which regulates the climate.
Posted at 7:52 PM, Aug 09, 2021

Millions of Americans flock to the Atlantic Ocean beaches along the east coast of the country for summer vacations. The warm waters and hot sun combine to make a relaxing experience. But, while they are relaxing, the Atlantic Ocean is hard at work.

The global water conveyor belt wraps around the planet. It transports water through the Earth's oceans. In the northern, western hemisphere, it is called the Atlantic Meridional Overturning Circulation (AMOC).

The AMOC is a critical part of the Earth’s energy balance which regulates the climate.

The sun heats up the water near the equator causing it to become more salty through evaporation. The warm water then flows northward. As it approaches the tip of Florida, its name is changed to the "Gulf Stream." This stream of warmer water then turns and flows across the Atlantic Ocean toward Europe.

As the water flows across the deep Atlantic heading northward, its temperature drops and the water becomes more dense. The colder, denser water starts to sink towards the bottom of the Atlantic Ocean.

Once it reaches the ocean floor, the dense cold waters start to flow southward toward the equator. When it arrives, the process starts over again.

A new scientific study reports proxy data shows the AMOC is slowing down and could stop flowing. The ramifications would alter life in the Northern Hemisphere.

In the 2004 blockbuster movie, "The Day After Tomorrow," the plot suggested dramatic temperature drops, damaging storms and rising sea water levels.

As depicted in the movie, human-caused global temperature increases led to the melting of polar ice sheets. In real life, similar large-scale glacier and ice sheets are melting in Greenland. Last month, enough ice melted in Greenland to flood all of Florida with 2 inches of water.

The melted water from these glaciers and ice sheets is freshwater. When it flows into the North Atlantic Ocean it is less dense because of the lack of salt. This causes the new water to float and not sink to the bottom, which disrupts the AMOC cycle.

The AMOC has not stopped moving yet, but it's flowing at its slowest rate in 1,000 years.

It has stopped at least once before. The last known time was at the end of the most recent ice age. A large amount of freshwater from a North American glacier flooded the Atlantic Ocean.

The results were catastrophic for Europe and North America. It caused significant sea level rises which flooded the coastlines of the continents. Temperatures plunged on both sides of the Atlantic. The cold temperatures stopped plants from growing. Along the equator, the temperatures rose dramatically, because the hot water was not flowing away from the region.

The size of the AMOC makes it difficult to tell if it is still moving or coming to a stop. Unlike in the movie, the ramifications will not be instantaneous, but will happen just like they did thousands of years ago.

This story was originally reported by Scott Withers on