According to scientists, the deep ocean circulation that forms around Antarctica could be headed for collapse. A decline of this ocean circulation will stagnate the bottom of the oceans and affect climate and marine ecosystems for centuries to come.
Cold water that sinks near Antarctica drives the deepest flow of the overturning circulation which is a network of currents that spans the world’s oceans. This overturning carries heat, carbon, oxygen and nutrients around the globe. This influences sea level, climate and the productivity of marine ecosystems.
“Our modeling shows that if global carbon emissions continue at the current rate, then the Antarctic overturning will slow by more than 40 percent in the next 30 years—and on a trajectory that looks headed towards collapse,” says Professor Mathew England of the ARC Centre for Excellence in Antarctic Science.
Approximately 250 trillion tons of cold, salty, oxygen-rich water sinks near Antarctica each year. This water then spreads northwards and carries oxygen into the deep Pacific, Atlantic and Indian Oceans.
“If the oceans had lungs, this would be one of them,” says Prof England.
Their model captures detail of the ocean processes that previous models haven’t been able to, including how predictions for meltwater from ice might influence the circulation.
This deep ocean current has remained relatively stable for thousands of years, but with increasing greenhouse gas emissions, Antarctic overturning is predicted to slow down significantly over the next few decades.
A collapse of this deep ocean current would cause the oceans below 4000 meters to stagnate.
“This would trap nutrients in the deep ocean, reducing the nutrients available to support marine life near the ocean surface,” says Prof England.
“Such profound changes to the ocean’s overturning of heat, freshwater, oxygen, carbon and nutrients will have a significant adverse impact on the oceans for centuries to come.”
https://phys.org/news/2023-03-deep-ocean-currents-antarctica-collapse.html