Increased seafloor life seen as negative global warming feedback
Shrinking sea ice around parts of Antarctica has spurred the growth of seafloor life that may help accumulating and bury carbon, researchers reported in the Cell Press journal Current Biology.
“It was a surprise that life had been invisibly responding to climate change for more than a decade below one of the most obviously visible impacts of climate change: the ‘blueing’ poles,” said David Barnes, of the British Antarctic Survey. “We’ve found that a significant area of the planet, more than three million square kilometers, is a considerable carbon sink and, more importantly, a negative feedback on climate change.”
Most of the known consequences of climate change have resulted in positive feedback, which exacerbates global warming. For example as Arctic sea ice melts, the Earth’s surface has turned from reflective white to a much darker blue at the poles, absorbing more heat and melting even more ice.
Some research has shown that expanding Arctic forests and new algae blooms in waters uncovered by sea ice melt were, to some extent, working against climate change. But the new research from Antarctica suggests that the recent growth bryozoans — organisms sometimes referred to as “could be more important than both” when it comes to absorbing excess atmospheric carbon.
The researchers calculate that growth of the bryozoans around West Antarctica has nearly doubled, taking up as much carbon as about 123,000 acres of tropical rainforest. That carbon may be trapped and buried at the bottom of the ocean, given the depth of the polar continental shelves, the researchers said.
Antarctica has not experienced a net loss of sea ice in the way the Arctic has. The ice has melted over more-productive continental shelves as ice has formed over less-productive, deeper waters. In the new study, Barnes and his colleagues collected specimens across West Antarctic seas and used high-resolution images to calculate the density of life on the seabed.
Barnes said the surprising differences in the amount of carbon taken up in different regions in Antarctica linked closely to the sea ice losses at each location.
“The forests you can see are important with respect to the carbon cycle and climate change, but two-thirds of our planet is ocean, and below it the life you can’t see is also very important in climate responses as well,” Barnes said, adding that it’s important to find out whether similar things are happening in the Arctic.