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Wed May 20, 2020, 01:51 PM

Antarctic algal blooms: 'Green snow' mapped from space


Antarctic algal blooms: 'Green snow' mapped from space

By Jonathan Amos
BBC Science Correspondent

8 hours ago
UK scientists have created the first wide-area maps of microscopic algae growing in coastal Antarctica. Satellite observations were used to count nearly 1,700 patches where large blooms had turned snow cover green.

The team says the photosynthesising organisms are an important "sink" for pulling carbon dioxide out of the atmosphere. They are also key actors in the cycling of nutrients in what is one the most remote regions on Earth.

"These are primary producers at the bottom of a food chain. If there are changes in the algae, it obviously has knock-on effects further up the food chain," explained study leader Dr Matt Davey from Cambridge University. "And even though the numbers we're talking about are small on a global scale, on an Antarctic scale they're substantially important," the ecologist, who has since joined the Scottish Association for Marine Science in Oban, told BBC News.

Detecting the green algae from space was a tricky task.

While it's easy to spot the organisms' discolouration when walking in the snow on the ground, from orbit it becomes much harder to tease out the blooms' signal against what is a highly reflective surface.

Fortunately for the team, the European Union's Sentinel-2 spacecraft have high-fidelity detectors that are sensitive in just the right part of the light spectrum to make the observation.

The study mapped the Antarctic Peninsula, the finger of land which points up from the White Continent towards South America. The blooms are seen predominantly to be on the western side of this feature. Two-thirds were on the many islands that dot the coastline.

Totalled, the microscopic algae covered an area of almost 2 sq km. It means they're tying up roughly 500 tonnes of carbon a year. This is equivalent to the amount of carbon that would be emitted by about 875,000 average petrol car journeys in the UK, the team calculates.

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Reply Antarctic algal blooms: 'Green snow' mapped from space (Original post)
nitpicker May 20 OP
Judi Lynn May 22 #1

Response to nitpicker (Original post)

Fri May 22, 2020, 11:01 PM

1. Antarctic snow is turning green and climate change is to blame

Chris Davies - May 22, 2020, 11:13 am CDT

Antarctica’s iconic white terrain is turning green, and the problem is only going to get worse, scientists warn, as climate change wreaks havoc on some of the most distant areas of the Earth. Green snow algae is proving a stubborn addition to the Antarctic Peninsula coast, a new study has shown, and rising temperatures suggest greater spread is likely.

Researchers from the University of Cambridge and the British Antarctic Survey tracked two years of algae growth in the region, combining on-site measurements with images taken by the European Space Agency’s Sentinel 2 satellite. That snapped photos of the Antarctic regions between 2017 and 2019, allowing the first ever map of the spreading green snow to be created.

The results are ominous. 1,679 separate blooms of green algae were identified in total, working out to roughly 0.73 square miles – or almost 500 acres – overall. While that may not sound like a huge area, it’s a significant change in the Antarctic’s capacity to capture carbon dioxide from the atmosphere via photosynthesis.

What has already grown is capable of absorbing more than 500 tons of carbon each year, the researchers calculate, and is likely having a significant impact on downstream terrestrial and marine ecosystems. While that could actually reduce carbon dioxide beneficially, it will also leave the Antarctic regions darker and thus more likely to absorb heat. That could end up resulting in a faster pace of melting, with a knock-on impact on sea levels and more.


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