A frozen chunk of land scientists thought was impossible to thaw is melting — and the effects could be catastrophic

There seems to be an ever-growing list of ominous consequences of melting ice— especially when it's the kind scientists expected would remain frozen forever.

"Until recently, permafrost was not a major concern of climate scientists, because, as the name suggests, it was soil that stayed permanently frozen," New York Magazine's David Wallace-Wells wrote in a recent piece about climate change.

Permafrost is a combination of ice, soil, plants, and other materials that stays frozen all year round, even as layers on the very top thaw out seasonally. The United States Geological Survey compared it to a "sponge" that soaks up carbon and nutrients.

But by the middle of this century, scientists project that the area of permafrost in the Northern Hemisphere will decrease between 20-35%.

The most obvious challenge of melting permafrost is flooding, which poses a threat to sea levels as well as facilities in the Arctic circle like the "doomsday" vault, which stores seeds for every known crop on the planet. Melted ice water recently flooded the vault, but ultimately the water was kept away from the seeds.

But melting permafrost can also lead to unanticipated effects that humans haven't had to worry about for thousands of years.

"Arctic permafrost contains 1.8 trillion tons of carbon, more than twice as much as is currently suspended in the Earth’s atmosphere," Wallace-Wells wrote.

As the permafrost in the Arctic melts, it could release that carbon dioxide, along with methane, an even more potent gas that traps in 30 times as much heat as carbon dioxide. Such a release could influence the global climate, researchers concluded in 2014.

Even more daunting, scientists working in the Arctic circle in recent decades have unearthed several massive viruses that some say could be re-awakened if the permafrost that imprisons them dissolves.

Some researchers have suggested that these enormous viruses could thaw out, escape, and make lots of people sick. There's even a possibility that some infections that were a problem in Siberia around the 18th and 19th centuries could make a comeback as well.

It sounds like something out of a horror film, but you shouldn't get too concerned — at least not yet.

What thawed-out viruses could mean for humans

In 2015, researchers in Siberia uncovered the Mollivirus sibericum, a 30,000-year-old behemoth of a virus that succeeded in infecting a rather defenseless amoeba in a lab experiment. About a decade earlier, scientists discovered the first Mimivirus, a 1,200-gene specimen measuring twice the width of traditional viruses, buried beneath layers of melting frost in the Russian tundra. (For comparison, HIV has just nine genes.)

The likelihood that these viruses will break free and sicken humans is slim, according to New York Times science columnist Carl Zimmer, whose recent book, "A Planet of Viruses," digs into what we know about viruses and the diseases they cause.

"These particular viruses infect amoeba. So if you're an amoeba, yeah you should be really scared," Zimmer told Business Insider in a 2015 interview. "There are no human pathogens that have burst out of the Siberian permafrost. That's not to say that viruses won't emerge, but there are so many viruses circulating in living animals, I think we should put these frozen viruses very low on our list of concerns."

Zimmer added in a recent email that most of these massive viruses have been found after samples of Arctic ice were melted in a lab — they're not currently crawling along the the Russian tundra like some microscopic Frankenstein.

They "didn't just thaw themselves out," he says. "They were carefully processed in labs. That's yet another clue that the odds of an ancient outbreak are very low."

But that doesn't mean the recent discoveries are useless. They're currently teaching us about the nature of viruses, which we previously assumed to be fairly small and simple. These ancient viruses, on the other hand, are about 30 times bigger than our average virus, and rival the size of a bacterium.

Mollivirus sibericum, for example, looks like this under a microscope:

mollivirus

In addition to its unusual size, Mollivirus sibericum differs from the majority of viruses in that it has more than 500 genes that give instructions for making proteins. If we're ever going to reevaluate the characteristics of viruses, these ancient thawed-out ones could help us take a fresh look.

"They're in and of themselves fascinating and they really challenge us to think about what viruses are," Zimmer said.

Between the threats of thawed-out viruses and greenhouse gases from melting permafrost, climate scientists have a lot to consider when confronting the consequences of rising global temperatures.

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