arctic seabed climate change
September 21, 2015

Antarctic seabed life reduces climate change

A huge chunk of planet Earth three million square kilometers across has been acting as a giant carbon sink and helping to counteract climate change, but why didn’t we know about it before now? It’s because the area in question lies deep beneath the Antarctic Ocean.

Scientists working for the British Antarctic Survey (BAS) have discovered how, as polar ice melts, seabed life is working against climate change, according to a press release.

Less ice means more seabed life

The BAS study used data from more than twenty years of research and found that retreating sea ice over Antarctic waters led to the increased growth of life on the seafloor in some areas.

“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 BAS.

The "blueing" Barnes refers to occurs when sea ice melts, changing the Earth’s surface from reflective white to a much darker blue at the poles. The darker areas absorb more heat and cause even more ice to melt in a dangerous feedback loop.

The impact of climate change is normally a string of bad news stories, like blueing, so this research comes as a welcome surprise.

“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,” said Barnes.

Similar processes have been seen before. For example, scientists knew that new algal blooms found where ice shelves disintegrated, as well as forests across the Arctic regions, were mitigating climate change.

But the BAS team believes their studies of West Antarctic bryozoans, also known as “moss animals”, suggest that other seabed organisms “could be more important than both” when it comes to capturing and storing carbon.

Loss of sea ice in Antarctica is a more complex picture then in the Arctic where we see a big net loss of ice. Antarctic ice has melted over more productive continental shelves but has formed over deeper and less productive waters.

Growth of the bryozoans

Barnes and his colleagues collected bryozoan specimens across West Antarctic seas and used high-resolution images to calculate the density of life on the seabed.

During the two decade long study, the BAS observed big annual increases in the annual production of shelf seabed carbon in the bodies of the West Antarctic bryozoans. The growth of the bryozoans has nearly doubled, with the animals taking in more than 105 tons of carbon a year since the 1980s.

If the same growth levels were applied to other undersea species, there could be an increased drawdown of carbon of about 106 tons a year. That’s equivalent to about 50,000 hectares of tropical rainforest! Better still, because of the depth of the polar continental shelves, the Antarctic seabed could be an extremely efficient and long term carbon capture system.

The amount of carbon taken up in different regions in Antarctica is closely linked to sea ice losses at each location. According to Barnes, one location, the South Orkney Islands—which were the world’s first High Seas Marine Protected Area—“is bang on a carbon hotspot, without us realizing!”

These findings show the importance of studying ocean life for understanding changing climate.

“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,” said Barnes.

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Feature Image: Thomas Lundalv