The climate of our Planet depends largely on what happens in the oceans. However, it is not only the functioning of the atmosphere that is disrupted by broadcastsbroadcasts of greenhouse gases, the oceans too. And one impacts the other, like a snake biting its tail.
The Amoc megacurrent transports warm waters from the South Atlantic Ocean to the high latitudes of the North Atlantic Ocean. This water then cools and forms “cells” of different temperatures which play an important role: they redistribute the heatheat and the carboncarbon in several areas. This mechanism is essential for the overall functioning of the ocean, marine life (by making plankton travel) and the climate. The Amoc current strongly influences the weather reportweather report from Europe, America, but also Africa. It also participates in the circulation of bottom waters of theAntarcticAntarctic, which are the coldest and most oxygenated waters of the ocean. These are found below 4,000 meters depth. Ocean specialists refer to these bottom waters as “ ventilationventilation oceans “.
The most inaccessible areas of the oceans also suffer from the consequences of warming
However, the American study shows that the transport of water, towards the bottom waters of Antarctica, fell by 12% between 2000 and 2020 due to the significant warming of West Antarctica. Rising temperatures in Antarctica weaken the Amoc, which then plays less and less of its role in transporting water. This observed dilution of cold deep waters would therefore be proof that the Amoc is weakening from year to year and that its consequences are already perceptible. This warming not only reduced the amount of cold bottom water, but also contributed to the rise in sea level. The warming of these deep waters would have increased the sea level by an additional 2.8 mm.
According to NOAA, these findings on Antarctica’s bottom waters show that even the most inaccessible areas, such as the deep oceans, are affected by greenhouse gas emissions linked to human activities. The study focuses here on the North Atlantic Ocean, but these first observations tend to suggest that this type of transformation would be present in all oceans.
A marine mega-current on the verge of collapse
Article from Karine DurandKarine Durandwritten on January 19, 2023
The functioning of our Planet and the regulation of the global climate depend largely on several ocean mega-currents. Scientists already knew that the Atlantic Amoc Current was likely to weaken due to warming, but a new, much more pessimistic study explains that another major current is at risk of being interrupted altogether in the future.
Warming sea water causes major currents in the Atlantic and Southern Ocean to slow down, according to scientists at the University of California. In a new study published in Nature Climate Changethey explain that if this process continues, an immense upheaval in the climate will occur.
Weakening of two currents essential to regulating the climate
By analyzing the forecasts of 36 climate modelsclimate modelsresearchers discovered that the Atlantic Meridional Overturning Circulation (Amoc) and the Southern Meridional Overturning Circulation (or Smoc), which are part of the thermohaline circulationthermohaline circulation, will slow down by 42% by 2100. In the worst warming scenarios envisaged by the models, the southern meridional overturning circulation could completely stop by 2300. The main responsible for this weakening, or even complete disintegration, of these essential currents to regulate the climate, is none other than global warming. According to the study’s lead author, J. Keith Moore, “ this would cause a global climate disaster of the same order as if all glaciersglaciers disappeared ».
Worsening warming and disappearance of marine life
Thanks to this circulation mechanism, warm water is pushed north into the Atlantic towards Greenland and Norway: it cools, evaporates, and becomes saltier. Its heavier weight then makes it descend into the depths, heading south. This movementmovement also circulates nutrientsnutrients which are the basis of the food chainfood chain. In addition, this interaction between sea water andairair is at the origin of a chemical reactionchemical reaction which helps absorb CO2 and sequester it in the depths of the ocean. THE phytoplanktonphytoplankton pump then this carbon dioxidecarbon dioxide to carry out its photosynthesisphotosynthesis. The weakening of these major ocean currents would therefore have two major consequences:
- aggravated warming of the climate, because the oceans could hardly absorb CO2one of the main greenhouse gases;
- a massive disappearance of marine life, because phytoplankton and other nutrients at the base of the food chain will be in sharp decline and will no longer be able to travel with the currents.
In addition to these two main effects, the weather will be completely turned upside down: a weakening, even slight, of the Amoc will result in a significant drop in precipitationprecipitation in certain regions of the world, such as Africa. The authors point out that the survival of humanity depends on the proper functioning of this “carbon pump”: without it, all the CO2 that we emit through our activities will have no choice but to disperse into the atmosphere, causing rising temperatures to explode.
