What will the oceans look like in 100 years?

It’s no longer a surprise, but this new study reaffirms the negative effects of global warming on the oceans.

That’s the result of several researchers at North Carolina State University looking back, trying to predict what might happen 100 years from now if we don’t cut our greenhouse gas emissions quickly. They actually looked at data from the Pliocene epoch (-5.3 to -2.6 million years ago).

“The Pliocene is the last time we had a globally stable, warm climate. The average temperature at that time was 2-3°C warmer than today, which scientists predict will be in about 100 years.Professor of Marine, Earth and Atmospheric Sciences Kathryn Davis made a statement to the press after the publication of this study.

Lots of dead zones

The object of their research concerns the existence of dead zones. The “dead zones” that have been observed since the late 1990s refer to the so-called hypoxic, that is, large regions with a lack of dissolved oxygen. In the dead zones of our oceans, scientists observe a decrease in oxygen concentration of up to 50%, which causes the fauna to suffocate. And this only at depths between 100 and 1000 meters below the surface.

Some of them are of natural origin, especially in the Black Sea, where the lack of oxygen has lasted for millions of years, or even in the great depths of the sea. Dead zones are mainly found along the coast of the United States, on the West African side, and in the western part of Indonesia.

The first identified cause of ocean oxygen depletion was intensive agriculture due to nitrogen, pesticide or heavy metal pollution. However, scientists have been warned by their presence in open waters, out of the reach of agricultural waters.

Later, they were able to prove that the increase in the number of these zones and their scale goes hand in hand with the exacerbation of climate change: the warming of the climate actually causes an increase in the temperature of the sea water and the oxygen melts. less good in hot water. Human activity will be a direct result.

>> Also read: Priority of the decade: protecting the ocean

Disturbing predictions

Already in 2004, the number of dead zones in the world was considered equal to 150, while in 1970 their number was insignificant. Today, they are growing not only in number, but especially in terms of territory, by about 5% per year.

It is enough to look at the cartography of the established “dead zones” related to the constants of the Pliocene period. Fossilized plankton, single-celled organisms the size of large grains of sand called foraminifera, have thus allowed scientists to find dead zones during the Pliocene, a species found only in marine areas with low oxygen.

This map thus constructed shows that oxygen-poor waters are now more common in the Atlantic Ocean, especially in its northern part. The map below shows the Pliocene “dead zones”.

“This map of the Pliocene dead zones can give us an idea of ​​what the Atlantic Ocean might look like in 100 years on a warmer Earth. Because there is less oxygen in warm water. We are already seeing itCatherine Davis commented.

Global warming: effects on ecosystems

Lack of oxygenation of water leads to environmental modification, which affects marine biodiversity. When there is little or even too little oxygen, fish that need to breathe become hypoxic and migrate to better oxygenated areas, affecting the ecosystem as a whole and therefore local biodiversity.

Especially for animals that cannot run fast, such as crustaceans and crayfish, these areas are at risk of suffocation. In addition to destroying many species and ecosystems, dead zones affect the entire fishing industry, depleting fish stocks.

Also, changes in oxygen levels can trigger the release of dangerous chemicals such as nitrous oxide, a greenhouse gas up to 300 times more potent than carbon dioxide, and hydrogen sulfide.