According to deep ocean models, 250 trillion tonnes of cold, salty, oxygen-rich water sinks near Antarctica annually. As it flows north, this water transports oxygen to the Indian, Pacific, and Atlantic seas.
The deep ocean circulation that occurs around Antarctica is in danger of disintegrating, according to scientists. If this kind of ocean circulation were to drastically decrease, it would have far-reaching consequences for climate and marine ecosystems.
Scientia Professor Matthew England, Deputy Director of the ARC Centre of Excellence in Antarctic Science (ACEAS) at UNSW Sydney, oversaw the research and compiled the report detailing the findings. Authors from the Australian National University (ANU) and the Commonwealth Scientific and Industrial Research Organization (CSIRO) join Dr Qian Li (previously of UNSW and now at MIT) as the primary authors of their study published today in Nature.
The overturning circulation is a system of currents that covers the world's oceans, with its deepest flow driven by cold water that descends near Antarctica. The overturning distributes energy, carbon, oxygen, and nutrients all across the world. Because of this, climate, sea level, and marine ecosystem production are all affected.
Over 250 trillion tonnes of cold, salty, oxygen-rich water sinks near Antarctica every year, according to models of the deep ocean. Oxygen is carried by this water to the depths of the Indian, Pacific, and Atlantic oceans as it moves northward.
Under the IPCC's "high emissions scenario," the group of experts calculated how much deep water will be formed in Antarctica between now and 2050.
The model accounts for factors in the ocean that have eluded earlier models, such as how forecasts for meltwater from glaciers may affect the circulation.
While the speed of this deep ocean current has been fairly constant for thousands of years, scientists expect that as greenhouse gas emissions continue to rise, Antarctic overturning will gradually slow down over the next several decades.
What does it mean?
Consequences of decreased Antarctic overturning If this deep ocean movement were to stop, the waters below 4,000 metres in depth would become stagnant. "This would trap nutrients in the deep ocean, reducing the nutrients available to support marine life near the ocean surface," explains Prof England.
Model simulations reveal a slowdown of the overturning, which subsequently leads to fast warming of the deep ocean, according to co-author Dr. Steve Rintoul of CSIRO and the Australian Antarctic Program Partnership.
Direct observations, as Dr. Rintoul puts it, show that deep ocean warming is already happening. The research discovered that the Antarctic overturning circulation is slowed because melting ice makes the surrounding ocean waters less thick. The melt of the Antarctic and Greenland ice sheets is predicted to continue to intensify as the earth warms.
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"Our study shows that the melting of the ice sheets has a dramatic impact on the overturning circulation that regulates Earth`s climate, explains Dr Adele Morrison, also from ACEAS and the ANU Research School of Earth Sciences.
It's conceivable that a legendary body of water may vanish forever, as Professor England puts it.
Significant negative effects on the seas will last for millennia if the overturning of heat, freshwater, oxygen, carbon, and nutrients is drastically altered.
(With ANI inputs)
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