The mystery of the “Blue Tact” of the North Atlantic resolved?

We know that the temperature on the surface of the oceans has been up all over the planet for a hundred years. However, a small region in the north of the Atlantic resists the phenomenon again and again. In English, we talk about it like blob or mysterious cold blob.

A hypothesis has been circulating for a few years already, wanting that it was the weakening of the meridian traffic of Atlantic reversal (AMOC, for Atlantic Meridional Overturning Circulation) – A system of ocean currents – which would be responsible.

When all is well, the Amoc works like a treadmill: it first transports the hot and salty water from the tropics to the North Atlantic. At this location, water cools and becomes more dense, which leads it to the bottom. This cold water then returns south and the cycle starts again.

In an article published in May in the newspaper Communications Earth & EnvironmentCalifornia researchers explain that they have conducted simulations from two types of data: observations on the Amoc collected for 20 years and temperature and salinity of the sea collected in the last 100 years.

This analysis allows them to confirm that the AMOC slowed down between 1900 and 2005, due to the melting of the Greenland ice cream. This supply of fresh water to the Water of the Atlantic would have disrupted the dynamics of the system.

What is happening in the ocean would however be a small part of the problem, said a team of Pennsylvania scientists in an article published in June in the newspaper Science Advances.

According to them, the weakening of the Amoc would also cause dry and colder atmospheric conditions, which would amplify the cooling of surface water in this region of the Atlantic. This would help keep the spot cold at a temperature lower than those of surrounding waters.

Researchers from Pennsylvania recall that the cold spot influences not only the local climate, but also certain phenomena such as the jet current, the trajectory of storm systems and until the European climate, hence the importance of better understanding its causes.