Vast Arctic landscapes may appear to be desolate, barren places, but take a look through a microscope and you’ll see thriving ecosystems. The top few meters of ice are home to an estimated hundred million billion trillion (or 10 to the power of 29) microorganisms.
That’s why Joseph Cook, a researcher at the University of Sheffield in the U.K., describes it as a frozen rainforest. “I think it’s a very widely held misconception that Arctic ice and snow is sterile and lifeless,” Cook says. “That’s just not the case. It’s fundamentally biological.”
As a glacial microbiologist, Cook studies the things that live and grow on the ice, how they change the ice’s colour, and in turn, the rate at which the ice melts.
Algae that grows on the surface of snow can be bright green or red, while on ice it tends to be brown or grey – so dark it looks like concrete.
Whether it’s algae or contaminants in the air, such as dust or soot from wildfires, that darken the ice, they change how it absorbs the sun’s rays. When the ice is darker, it absorbs more sunlight and melts faster.
For the past five years, Cook has spent summers on the Greenland Ice Sheet, studying algae blooms and taking samples. He is one of several scientists working on a project called Black and Bloom, funded by the U.K.’s Natural Environment Research Council.
“The hypothesis that we’re testing is that the microbial ecosystem on Greenland is darkening it and accelerating its melt,” he says. If there’s a larger melting area, then there’s a larger area where algae can grow, which then darkens more of the ice, causing more of it to melt.
“There’s potentially positive feedback – that’s the hypothesis that we’re testing.”
The melting of the Greenland Ice Sheet has significant ramifications. It’s the largest continuous piece of ice in the Northern Hemisphere, made up of roughly 1.7 million square kilometers (656,000 square miles) of frozen water. Fully melted, it would add about 7m to sea levels around the world.
“As the planet warms, it will melt faster,” Cook says. “That’s not that controversial a thing to say, I don’t think. But what we don’t really understand is all of the cogs in what I refer to as the melt machine.
“If we want to really be able to predict how quickly the ice is going to melt, then we need to understand all of the cogs in the machine, including that darkening process. And one of the main areas that we don’t understand about it is algae growth.”
The algae itself isn’t new. Back in the 1800s, explorers noted discoloration of the Greenland Ice Sheet. One Finnish-Swedish explorer, Adolf Erik Nordenskiöld, even described the algae as the “greatest enemy of the massive ice” because it darkened it, thus causing it to melt faster, says Cook.
“It’s not a new hypothesis,” he says. “It’s just that in a warming climate, these things take on a new significance, and it’s suddenly become a lot more important to understand all the drivers in the ice melting.”
In addition to algae, Cook studies another microbial habitat called cryoconite holes. These are holes formed in the ice by a microorganism called cyanobacteria, which acts like a net on the ice, catching dust particles and mineral fragments and bundles them into granules. Because these are a darker color than the ice, they melt the ice underneath them, forming holes.
The holes play host to a small ecosystem: cyanobacteria and algae photosynthesize within them, then other microorganisms feed on the carbon produced by the photosynthesis.
Last year, Cook won a Rolex Young Laureate award for his research, and with the funding, he bought a drone that he used recently in Svalbard, Norway, to measure specific wavelengths of light on the ice.
He’ll return to Greenland in July. Daytime temperatures can be as warm as 15C (59F), so to prevent melting the ice with their body heat, the research team sets up camp on top of polyfelt and plyboard rather than pitching tents directly on the ice.
But this almost insulates too well, with the frozen water around the camp melting faster. “You end up rocking on a pinnacle of ice like a seesaw after a couple of days,” Cook says. They must rebuild their camp every four or five days.
He became interested in glacial microbiology when he began reading about how microbial life could change the physical environment. He was intrigued by the idea that something microscopic could have an effect on something as massive as the landscape.
“It illustrates an underlying deep complexity in the world that maybe we don’t understand so well,” he says. “As time goes on, it’s becoming more important to understand it.”
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