Melting Antarctic ice could have disastrous consequences for global ocean circulation and the planet’s climate, according to new research published today in the journal Nature. The study warns that deep ocean water flows from the Antarctic could decline by 40 percent by 2050, threatening the collapse of circulation crucial for planetary systems.
The “overturning circulation” of the oceans – driven by the movement of denser water towards the sea floor – helps deliver heat, carbon, oxygen, and vital nutrients around the globe. But as temperatures rise, freshwater from Antarctica’s melting ice enters the ocean, reducing the salinity and density of the surface water and diminishing that downward flow to the sea’s bottom.
The study’s findings also suggest the ocean would not be able to absorb as much carbon dioxide as its upper layers become more stratified, leaving more CO2 in the atmosphere. Warm water intrusions in the western Antarctic ice shelf would increase, but the study did not look at how this might create a feedback effect and generate even more melting.
“If the model holds true, the deep ocean current will be ‘on a trajectory that looks headed towards collapse,'” said University of New South Wales climate professor Matthew England, who coordinated the study. “That’s stunning to see that happen so quickly. It appears to be kicking into gear right now. That’s headline news.”
The effect of meltwater on global ocean circulation has not yet been included in the complex models used by the Intergovernmental Panel on Climate Change to describe future climate change scenarios, but it is going to be considerable, England said. The study team included lead author Qian Li of the Massachusetts Institute of Technology and co-authors from the Australian National University and Australia’s Commonwealth Scientific and Industrial Research Organisation.
“There were many uncertainties about the impact of declining deep ocean circulation,” said UNSW emeritus professor John Church, who was not involved in the study. “But it seems almost certain that continuing on a high greenhouse gas emission pathway will lead to even more profound effects on the ocean and the climate system. The world urgently needs to drastically reduce our emissions to get off the high-emission pathway we are currently following.”
Source: Aljazeera
