What dark secrets are waking up in our melting ice caps?

At its thickest point, the Antarctic ice sheet measures almost five kilometres, which makes it taller than many of Earth’s mountains, and five times as tall as humanity’s tallest skyscraper. What lies beneath this ice is largely unknown, sometimes preserved for hundreds of thousands of years without exposure to the open air. It’s a mystery that has been mined for dramatic effect in films like John Carpenter’s The Thing – where a shapeshifting extraterrestrial is set loose after 100,000 years of cryogenic sleep – and also forms the basis of some IRL alien conspiracy theories. Some even speculate that our planet’s icy poles hide entrances to a secret subterranean realm.

Putting all the alien tales and conspiracies aside, though, is there really anything spooky lurking under the ice? The answer is yes. In fact, there are probably lots of organisms trapped in deep freeze, biding their time. And, while they might not be as glamorous as crashed UFOs or chilly cryptids, they could prove just as dangerous when the ice eventually thaws.

What’s the evidence for these mysterious organisms you ask? Well, in 2003, samples of bacteria were recovered by drilling down into a Tibetan ice cap, where the ice was more than 750,000 years old, and were able to be revived and cloned by researchers. Similarly, a “zombie” virus was revived from 30,000-year-old Siberian permafrost in 2014 (why you’d want to do that is anyone’s guess). More worryingly, a 2016 outbreak of anthrax in Siberia was eventually traced back to the rapid thawing of spores in ancient permafrost, after killing thousands of reindeer and infecting dozens of human beings.

Essentially, these phenomena confirm that potentially-harmful organisms can be brought back to life after spending hundreds of thousands of years on ice, and directly affect modern-day ecosystems. With estimates suggesting that we can expect four sextillion microorganisms (that’s a four followed by 21 zeroes) to be released each year as ice melt accelerates due to climate change, that’s not great news.

Giovanni Strona, a researcher at the European Commission’s Joint Research Centre, is at the forefront of the effort to understand just how much impact pathogens – organisms that cause disease in their host – released from ice melt could have on our world. Last month, he co-authored a study that mapped the introduction of such “time-travelling pathogens” into artificial ecosystems, in an attempt to understand how alien pathogens can find viable hosts in ecological communities, and how far they might spread. Unfortunately for us, the study concluded that “unpredictable threats so far confined to science fiction and conjecture could in fact be powerful drivers of ecological change”.

Below, Strona digs deeper into the implications, how the risks are amplified by man-made climate change, and what (if anything) we can do to prepare for the worst.

PATHOGENS CAN SURVIVE MILLENNIA UNDER THE ICE

Scientists have speculated about bringing woolly mammoths back to life using DNA from frozen specimens for years, and recently managed to “wake up” 46,000-year-old worms that were frozen in permafrost, but the vast majority of living things that survive millennia by being frozen under the ice are relatively simple, says Strona. In other words, we’re probably not going to witness a dino renaissance any time soon. Much more likely is the return of ancient organisms like bacteria or viruses.

“The main principle is: the simpler you are, the higher the chance you can survive in a frozen state,” Strona says. Another key finding in his research was that pathogens that thrived in the past have more chances to emerge from the ice and become a successful invader in the future. “That’s not necessarily good news,” he notes.

CLIMATE CHANGE IS SETTING THE PATHOGENS FREE

If pathogens are frozen, they’re relatively harmless, but once they’ve defrosted it’s sometimes possible that they re-integrate with today’s natural world, affecting existing bacteria populations and potentially affecting humans. This process has only sped up as humans drive global warming levels through the roof, with ice melt approaching irreversible tipping points.

“Of course, there is some natural seasonality, where the water freezes and the ice melts, but what we are witnessing now in terms of permafrost melting is 99 per cent due to climate change,” says Strona. “40 per cent of permafrost could disappear by the end of the century, if climate change is not slowed down.”

THE PATHOGENS BASICALLY TRAVEL THROUGH TIME

Imagine you’re preserved in suspended animation for a few thousand years. The world you wake up in would likely be very different to the one you left behind. You might cause disruption in the future society, or – in a Terminator-style future where AI has gone rogue – you could be killed off immediately. The same can basically be said for the defrosted pathogens.

“Our time-travelling invaders can be considered a sort of alien species,” says Strona. “But in a different dimension. In the temporal dimension.”

STRONA’S SIMULATIONS GIVE US SOME IDEA OF THE EFFECTS

For the reasons mentioned above, it’s hard to estimate exactly what effects these “alien invaders” could have when they leave their chilly slumber. Strona stresses that the simulations run by him and his team aren’t perfect predictors, since they’re based on artificial ecosystems modelled “in silico” (in other words, inside a computer). Nevertheless, they give us some of the best chances of understanding what might happen before it actually does.

Essentially, says Strona, the simulations work by setting up artificial ecosystems governed by the same rules as our biological environment, which produce dynamics like natural selection. “Then, you just let the simulation go.” This allowed the researchers to gather data on the pathogens themselves, as well as their interactions with existing organisms. AI technology was also brought in to help build a model that could predict the potential risk of invasion.

THE RESULTS OF THE EXPERIMENT WERE CHAOTIC

Despite the sophistication of Strona’s simulations and the vast quantity of data collected, it wasn’t possible to develop an accurate, reliable model that could predict whether any given alien pathogen would find a successful host in ecological communities. “The conclusion is that these invasion events are dominated by chaotic dynamics,” he says.

This means that the same alien pathogen can be successful or unsuccessful when introduced to very similar communities, for a “set of very complex combinations of conditions”. Similar dynamics are present in the science of earthquakes and large weather systems, which are both notoriously difficult to make predictions about.

THERE IS SOME GOOD NEWS

Strona was disappointed by the chaotic and surprising nature of the results, saying: “We were hoping to be able to provide something [that] might have improved preparedness and [...] had some predictive power.”

Another surprise, however, was the relatively small effect of the time-travelling alien organisms on the novel communities they were introduced to during the simulations. Strona compares this to the effects of globalisation: even though we’re all travelling around in planes and shipping goods across the world now, Earth’s ecosystems have emerged relatively unscathed from contact with the “alien” organisms we carry along for the ride.

“Some of them are just finding their place in local communities,” Strona says. “Of course, they have some impact, but the impact is not dramatic.” Hopefully, most organisms released from melting ice will similarly slot in with their surroundings.

THEN, THERE’S THE WORST-CASE SCENARIO

Unfortunately, not all defrosted organisms are likely to enjoy such a peaceful relationship with the modern world. Over hundreds of millennia, they could have lost their ecological adaptations, like an old man growing out of touch with younger generations. This kind of organism “would find itself in a hostile environment” and could take on an aggressive approach to survive and gain dominance.

Again, Strona emphasises that his study doesn’t model the actual implications of ancient pathogens released into human populations. However, his team’s models did discover that – in one per cent of cases – just one ancient pathogen could lead to a diversity drop of 30 per cent in its host community. This would have devastating consequences, causing major environmental damage, killing off host organisms, and even leading to species extinction.

HOW WE CAN PREPARE FOR THE WORST

Since it’s so hard to predict the risks of pathogens streaming out of melting ice and into our ecosystems, it’s also very hard to prepare for the most disastrous (and hopefully rare) scenarios. There are preventative measures, though. “The most obvious one is cutting emissions and trying to slow down the melting of the ice and permafrost,” says Strona. “Of course, that’s important for multiple reasons.”

Some more specific measures include a widespread effort to monitor the actual organisms that are being released from melting ice, which can be compared to what we know about existing pathogens, and used to build more accurate models.

An important thing to note is that the one per cent risk of ancient pathogens wiping out a third of their host community’s diversity is just what happened in Strona’s virtual ecosystems. This doesn’t necessarily translate to the actual risks in the real world. “On the other hand, our study might be seen as conservative,” he says. “What we did was move one virus strain from a past community to a modern one. What we are seeing in the real world is a continuous release of a high diversity of organisms. If we simulated something like that in our study, we would probably have recorded much stronger effects.”

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