Antarctic Ocean of the last ice age reveals how a ‘critical’ process of CO2 storage may slow again

Southern Ocean surrounds Antarctica [image credit: theozonehole.com]

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Here the ‘critical process of CO2 storage may slow’ headline seems to be another way of saying: ‘Warming oceans absorb and retain less CO2’, which is already known. It’s also known that historically such warming preceded any CO2 rise, as found in ice cores. The article soon raises the familiar alarmist spectre of a tipping point, but do we have a logic issue here?
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Off the coast of Antarctica, the sea ice retreated toward the southernmost continent and, like a bottle cap taken off a soda bottle, that reduced pressure slowed down a process of critical carbon dioxide capture, dramatically accelerating the warming of the planet.

But all that happened thousands of years ago, one of the death knells of the last ice age, says Phys.org.
. . .
Deep water storage
Antarctic Bottom Water—or AABW, in marine scientist speak—”forms when extremely cold, salty water sinks near Antarctica due to sea ice formation,” He says.

“This dense water then flows northward along the ocean floor, eventually rising at the surface,” He continues. How much of and how quickly this deep water rises is called the overturn rate, a process that links all the oceans together in a cycle called thermohaline circulation.

The AABW formation sequesters massive quantities of “atmospheric CO2 in the deep ocean for centuries,” He says. If its overturn rate increases—that is, if the carbon-trapping waters in the deep ocean rise to the surface and release that CO2 more quickly—it could represent “a critical tipping point that could dramatically alter regional climates, disrupt weather patterns globally and reduce the ocean’s capacity to absorb carbon dioxide.”

And yet, the sea ice of our own age is also retreating, so it’s critical that we understand these oceanic processes that have such a profound effect on the globe.

Deep water storage
Antarctic Bottom Water—or AABW, in marine scientist speak—”forms when extremely cold, salty water sinks near Antarctica due to sea ice formation,” [assistant professor] He says.

“This dense water then flows northward along the ocean floor, eventually rising at the surface,” He continues. How much of and how quickly this deep water rises is called the overturn rate, a process that links all the oceans together in a cycle called thermohaline circulation.

The AABW formation sequesters massive quantities of “atmospheric CO2 in the deep ocean for centuries,” He says. If its overturn rate increases—that is, if the carbon-trapping waters in the deep ocean rise to the surface and release that CO2 more quickly—it could represent “a critical tipping point that could dramatically alter regional climates, disrupt weather patterns globally and reduce the ocean’s capacity to absorb carbon dioxide.”
. . .
A climatic bellwether
According to the researchers’ model, this suggests that two bottom water formations—the North Atlantic and the Antarctic—weakened simultaneously, like two massive storage units suddenly failing to accept any more CO2.

“Suddenly,” here, is on the order of about 2 millennia, but accounted for half of the total CO2 rise throughout the full 8,000-year deglaciation, according to the paper.

“We’re seeing similar patterns today,” He writes. “Recent observations show AABW is weakening as the Southern Ocean warms.

“Understanding how these massive water masses behaved during past climate transitions helps us better predict future changes,” He says.

As the oceans continue to warm, deep ocean carbon trapping will slow down more and more, “potentially affecting global heat distribution, carbon sequestration and regional climate patterns.” [Talkshop comment – but ice cores show warming precedes ocean CO2 release].

Full article here.
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Image: Southern Ocean surrounds Antarctica [credit: theozonehole.com]