Microscopic life melts the ice of Greenland

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“People have been thinking about glaciers and glaciers lately … relatively lifeless places,” says British glacier expert Cook. “But when you look at it under a microscope, especially the Greenland glaciers and other glaciers reveal themselves as frozen rainforests of biodiversity.”

The rainbow hues that Cook encountered are created by a series of small life forms that thrive on the surface of the ice.

Biodiversity is generally considered a good thing, but in this case the spread of microbial life accelerates ice melting, and global sea levels may rise faster than scientists predict.

Three times the size of Texas, Greenland ice covers 656,000 square miles. The vast repository of fresh water is the single largest contributor to global sea level rise, with the potential to raise sea levels up to seven meters (23 feet).
A recent study indicates that the melting of ice – accelerated by the climate crisis – may have already reached irreversible levels.

Cook says the subtle lifestyle patterns he studies contribute to the problem.

One of these organisms is algae that grow in thin water on the surface of ice. It produces a purple-brown pigment that “acts like natural sunscreen,” Cook says, protecting the algae from the full force of Arctic sunlight. The pigment also causes the ice to heat up and melt.

“If you go out on a hot day wearing a black shirt, you’ll be warmer than going out wearing a white shirt on a hot day. The same thing happens in the snow,” Cook says. “These algae, like the black coat of ice, cause it to melt hot and fast in the sun.”

Cook’s research into part of the 3,900-square-mile Greenland ice sheet revealed that algae is responsible for up to 13% of ice melting. In some localized areas, algae accelerated melting by up to 26%.
Algae bloom around a field camp on the ice of Greenland, where Joseph Cook was during a 2016 trip.

“Evil cycle”

Glacier algae are not a new phenomenon – Cook says their records are in the diaries of polar explorers from the 1870s. Global warming has changed. With higher temperatures and reduced snowfall, a greater area of ​​ice is exposed, thus allowing algae to thrive.

Dispersing alkaloids increase ice melting and release more water and nutrients that are contained in the ice, which promotes algae growth – a process Cook describes as a “vicious feedback cycle”.

This is not the only destructive cycle that takes place in the snow. Another microbe – a type of bacteria found on the surface of ice sheets and glaciers – binds dust particles in melting water together to form a dark, dense, soil-like substance called cryogonite. The ice beneath the cryogenite melts, forming pits on the surface of the ice.

“That process creates an ecosystem that would not exist without a prominent place on the ice surface,” Cook says. Melting pores catch more dust and form cryogenic, which leads to more ice melting.

Bacterial melt holes are another threat to Greenland ice. The largest of these is about 20 inches in diameter.

Sources of rapid ice melting

Cook’s research adds growing evidence that ice has underestimated melting rates. A recent study using satellite data found that glaciers are more sensitive to warming climates than previously thought. It showed that Greenland ice is now melting seven times faster than it was in the 1990s.
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Cook says previous estimates of sea level rise may have been somewhat lower due to a lack of information on the role of ice-loving microorganisms.

Accurate forecasts are necessary because even a small rise in sea level can have a major impact – threatening beaches from the Pacific to Miami to India.
Sea level rise to the world economy.2 14.2 trillion lost or damaged property could be lost by the end of this century, and 287 million people could be subject to episodic coastal flooding.

“If we want to make good decisions about how we will manage our land, our infrastructure … and our economy in the future, we must have good forecasts of sea level rise and the risks associated with it,” Cook said.

What is clear is that glaciers are surprisingly dynamic and complex environments. “There are so many questions to answer,” Cook says. “It’s like a theme park for a scientist because there’s so much to do.”

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