Last summer, Zac Peterson was on the adventure of a lifetime.
The 25-year-old teacher was helping archaeologists excavate an 800-year-old log cabin, high above the Arctic Circle on the northern coast of Alaska.
They had pitched tents right on the beach. Over the course of a month, Peterson watched a gigantic pod of beluga whales swim along the beach, came face-to-face with a hungry polar bear invading their campsite and helped dig out the skull of a rare type of polar bear.
But the most memorable thing happened right at the end of the trip.
“I noticed a red spot on the front of my leg,” Peterson says. “It was about the size of a dime. It felt hot and hurt to touch.”
The spot grew quickly. “After a few days, it was the size of a softball,” he says.
Peterson realized he had a rapidly spreading skin infection. And he thought he knew where he might have picked it up: a creature preserved in the permafrost.
Nano-zombies or red herrings?
In the past few years, there has been a growing fear about a possible consequence of climate change: zombie pathogens. Specifically, bacteria and viruses — preserved for centuries in frozen ground — coming back to life as the Arctic's permafrost starts to thaw.
The idea resurfaced in the summer of 2016, when a large anthrax outbreak struck Siberia.
A heat wave in the Arctic thawed a thick layer of the permafrost, and a bunch of reindeer carcasses started to warm up. The animals had died of anthrax, and as their bodies thawed, so did the bacteria. Anthrax spores spread across the tundra. Dozens of people were hospitalized, and a 12-year-old boy died.
On the surface, it looked as if zombie anthrax had somehow come back to life after being frozen for 70 years. What pathogen would be next? Smallpox? The 1918 flu?
The media took the idea of “zombie pathogens” and ran with it.
“Climate change … could awaken Earth's forgotten pathogens,” The Atlantic wrote in November. “Many of these pathogens may be able to survive a gentle thaw — and if they do, researchers warn, they could reinfect humanity.”
“Scientists are witnessing the theoretical turning into reality: infectious microbes emerging from a deep freeze,” Scientific American wrote.
But something is a little fishy about these “zombie pathogen” stories: The evidence presented is as holey as Swiss cheese.
The key researcher cited is a biologist who studies amoeba viruses, not human viruses. These so-called monster viruses have evolved to live in cold soil, deep underground, not in warm, human flesh above ground.
And in terms of zombie bacteria, anthrax is a red herring. Anthrax has been “rising up” from soils all over the world for millennia, even longer.
The bacteria survive by hibernating in the ground until conditions are right and then spring back to life.Back in the Middle Ages, it was common to see fields of dead sheep in Europe, wiped out by “zombie” anthrax.
The French called these fields champs maudits, or the “cursed fields.”
Now there are some tantalizing hints that the Arctic is, indeed, a frozen champ maudits, filled with pathogens even more dangerous than anthrax. Across the permafrost — which covers an area twice the size of the U.S.
— there are tens of thousands of bodies preserved in the frozen soil. Some of these people died of smallpox. And some died of the 1918 flu — a strain of influenza that swept the globe and killed more than 50 million people.
- But is there actually any evidence that these deadly viruses could survive a “gentle thaw” and then start a new outbreak?
- To figure that out, I headed up to the top of the world, where Zac Peterson was last summer, to see exactly what type of creatures — and diseases — are hiding in the permafrost.
- I was not disappointed.
- “We've got a head right here”
- Up on top of an ocean bluff, Zac Peterson and a few students are on their knees, digging inside a hole that's about the size of a Volkswagen minivan.
In 2013, a severe storm ripped off a big chunk of the bluff. Now the 800-year-old cabin is teetering on the edge of a cliff, near the town of Utqiagvik in Alaska. The team is trying to pull off an emergency excavation before the cabin crumbles into the ocean.
Hunters have been using this spot for thousands of years. At one end of the house, somebody was storing fresh kills.
“We've got a head right here, and a main body right there,” says Peterson, as he points to two mummified seals, lying face up in a soup of thawing permafrost and decaying sea mammal flesh inside the cabin.
The Zombie Diseases of Climate Change
From the air, the coast of Greenland appears vast and tranquil. Hundreds of fjords, their surfaces a mirror of blue sky and cloud bottoms, divide the territory. In the gaps between them, the terrain folds over itself, hill over hill, descending into obsidian lakes. The turf is covered in the waxy pastels of alpine dwarf willows and the dull white of age-bleached lichen.
Though an immense ice sheet sits in its interior, Greenland’s ice-free coast encompasses almost 159,000 square miles and and houses 57,000 people.
In other words, it is larger than Germany with a population half the size of Topeka, Peoria, or New Haven.
It is possible to stand on a hill outside the coastal town of Ilulissat and hear only the grass quaking, the harbor ice dully grinding against itself.
I visited Greenland because, lately, the land here has gone soft, and disquieting things threaten to wake in it.
Let me orient you. At the top of the world, there is water. Television anchors sometimes speak of the Arctic Ocean as the “polar ice cap,” but that is a contingency of temperature and a quirk of today’s climate. Consider it instead a landlocked ocean, a northern Mediterranean Sea.
Surrounding it sit great landmasses—Europe, Asia, North America—and a surfeit of islands.
Among the largest are Svalbard, which is due north of Norway and so dense with polar bears that everyone who strays beyond its sole settlement must carry a rifle; Novaya Zemlya, the site of the largest atomic test ever conducted; and Greenland.
In all of these places, rich, marshy soils run from the edge of the interior ice right up to the ocean cliffs. Once, this dirt gave rise to lush ferns and open grasslands; now, after 35,000 years of frigid cold, we call them permafrost.
Despite their name, they are not permanently, or entirely, frozen. Every winter, a sheet of ice blossoms over the Arctic sea, and the soils seize shut with frost. Then, during the long summer days, the ice breaks up and the permafrost partially thaws.
“If there are microbes infectious to humans or human ancestors, we are going to get them.”
Lately, as summers have lengthened and winters have warmed, this seasonal transformation has lost its symmetry. What biologists call the permafrost’s “active layer”—the part of the dirt where microbes and other forms of life can live—now reaches farther underground, and further north, than it has for tens of thousands of years.
The newly active permafrost is packed with old stuff: dead plants, dead animals, mosses buried and reburied by dust and snow. This matter, long protected from decomposition by the cold, is finally rotting, and releasing gases into the atmosphere that could quicken the rate of global warming.
This matter is also full of pathogens: bacteria and viruses long immobilized by the frost. Many of these pathogens may be able to survive a gentle thaw—and if they do, researchers warn, they could reinfect humanity.
Climate change, in other words, could awaken Earth’s forgotten pathogens. It is one of the most bizarre symptoms of global warming. And it has already begun to happen.
The Russian botanist Dmitri Ivanovsky was just 28 when, at a scientific meeting in St. Petersburg, he presented evidence of an unexplainable phenomenon: He had found a disease with no germ.
When he exposed tobacco leaves to a certain clear liquid, he could watch the leaves mottle, but he could not find the bacteria under his microscope that could explain the change.
In the decades before his work—it was 1892—Louis Pasteur and other scientists had demonstrated that microscopic life could cause disease. But here was a disease with no microbe at fault.
Ivanovsky said that the disease must be inherent to the gloop he had put on the leaves. He termed it a virus, from the Latin word for slime.
One hundred and twenty-five years later, we still use Ivanovsky’s term, but we know viruses are far stranger than he ever imagined.
An individual virion, the unit of viral existence, makes many copies of itself over its life cycle, but it never does something that can be described as living. It never breathes or mates.
It punctures a cell’s wall, hijacks its protein factories, and forces it to make more of itself. A single virion can make tens of thousands of copies of itself near instantly. Viruses are living nonlife, a desirous but mindless substance.
At the frontier of viral life are Jean-Michel Claverie and Chantal Abergel, two professors of microbiology at Aix-Marseilles University who happen to be married to each other.
Since the turn of the century, they have established themselves as two of the world’s most famous microbe hunters.
In 2002, while researching Legionnaires’ disease in their lab in Marseilles, they discovered the largest virus ever: Mimivirus, a virion so large that it could be seen under a microscope.
They have identified four more monster viruses since, all several times larger than any virion known to science before 2000. Their menagerie oozes about in a far-flung set of landscapes: one monster virus was found in a shallow lake in Australia, another lurked in a bucket of seawater hauled off the Chilean coast. A third was discovered in a woman’s contact lens.
All of these mammoth viruses infect amoebae, not people. They do not pose an infective risk to us. But they are strange substances. They rival bacteria in size; they can be seen under a microscope. They are quite durable. And some of them produce more proteins than most amoebae.
Claverie and Abergel weren’t thinking of monster viruses when they began poking around in the permafrost. In 2013, Claverie read about a Russian team that had found a seed lodged deep in the permafrost.
The fruit, buried some 125 feet below the surface, had spent thousands of years at about 20 degrees Fahrenheit, never thawing out in the wax and wane of seasons.
But once warmed and placed in a pot, it sprouted waxy arms and delicate white flowers.
“The viruses we are getting [in the permafrost] are extremely abnormal.”
Claverie contacted the Russian team, explained his work with microbes, and asked for a bit of permafrost to test. The team agreed, and they mailed Claverie and Abergel a sample of the same deep-frozen core of permafrost that had contained the seed. The pair pulled a small sample onto a high-resolution microscope, brought it to room temperature, introduced an amoeba as bait, and waited.
And then, as they watched, a virus appeared in their viewfinder: Pithovirus sibericum, a massive ovular virion that had survived 30,000 years frozen in the ice core. It was also the largest virion ever discovered.
“We tried to isolate amoeba viruses without knowing they were going to be giant viruses—and a totally different type of virus than we already know appeared,” Claverie said. “It turns out the viruses we are getting [in the permafrost] are extremely abnormal, extremely fancy.”
Claverie and Abergel’s viruses aren’t a threat to humanity—yet. But human pathogens have also survived freezing and thawing in the permafrost. Last summer, an outbreak of anthrax in Siberia infected dozens of people and killed one child. The vector of disease is thought to be the thawing and decaying carcass of a reindeer killed in 1941.
And a team of Canadian scientists recently found a strain of bacteria, Paenibacillus, in a cave in New Mexico that had been closed off for more than 4 million years.
Though harmless to humans, the ancient bacteria was resistant to most clinical antibiotics, including most of the newest and most aggressive.
The discovery suggested that bacteria can survive the most exotic and remote environments.
“At once, you are going to excavate 16 million tons of permafrost that has not been moved in a million years.”
Researchers are continuing to test the limits of pathogens. Reportedly, a Soviet microbiology lab revived bacteria from the permafrost in the 1980s, but its paper went little noticed. Claverie is traveling to Siberia this year to core even deeper into the soil, to prove that viruses can survive being thawed out after a million years.
“We’re trying to go deeper and deeper in our sampling, to demonstrate that it is possible that viruses could survive—amoeba viruses. We are not going to try to revive human viruses, of course, we are not crazy,” he said.
He already frets about what climate change will unlock in the permafrost, especially when humans help it along.
Will the Thawing of Arctic Ice Release Diseases?
Anthrax bacterium. Credit: BSIP Getty ImagesAdvertisement
Around July and August of 2016 in a remote corner of Siberia called the Yamal Penninsula, more than 2,000 reindeer unexpectedly perished. Initially, a heat wave was suspected to have caused heatstroke in the reindeer, but doctors soon realized they had also become infected by bacillus anthracis, the bacterium responsible for anthrax. (Yes, the same anthrax that gained notoriety after being sent in powdered form to United States senators in 2001.) The Siberian anthrax outbreak also caused the hospitalization of more than 20 people and even one death.
But anthrax had not been seen in Siberia since 1941 so was this a case of bioterrorism? Fortunately not, but the suspected cause is also troubling.
Researchers believe the unusually high temperatures during the heat wave caused the permanently frozen soil – called permafrost – to thaw, releasing formerly frozen spores of anthrax into the air in a case of science fiction playing out in reality.
During the last anthrax outbreak in the region 75 years ago, the bodies of reindeer who succumbed to the infection were buried.
However, the frozen nature of the tundra means that bodies cannot easily be buried too deeply beneath the surface.
The cold, dark, low oxygen conditions of the permafrost also mean that certain bacteria can exist for long periods of time, laying dormant until they are re-released by, for example, the melting of the soil by a heat wave.
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There are diseases hidden in ice, and they are waking up
Throughout history, humans have existed side-by-side with bacteria and viruses. From the bubonic plague to smallpox, we have evolved to resist them, and in response they have developed new ways of infecting us.
We have had antibiotics for almost a century, ever since Alexander Fleming discovered penicillin. In response, bacteria have responded by evolving antibiotic resistance. The battle is endless: because we spend so much time with pathogens, we sometimes develop a kind of natural stalemate.
However, what would happen if we were suddenly exposed to deadly bacteria and viruses that have been absent for thousands of years, or that we have never met before?
We may be about to find out. Climate change is melting permafrost soils that have been frozen for thousands of years, and as the soils melt they are releasing ancient viruses and bacteria that, having lain dormant, are springing back to life.
In August 2016, in a remote corner of Siberian tundra called the Yamal Peninsula in the Arctic Circle, a 12-year-old boy died and at least twenty people were hospitalised after being infected by anthrax.
The theory is that, over 75 years ago, a reindeer infected with anthrax died and its frozen carcass became trapped under a layer of frozen soil, known as permafrost. There it stayed until a heatwave in the summer of 2016, when the permafrost thawed.
This exposed the reindeer corpse and released infectious anthrax into nearby water and soil, and then into the food supply. More than 2,000 reindeer grazing nearby became infected, which then led to the small number of human cases.
The fear is that this will not be an isolated case.
As the Earth warms, more permafrost will melt. Under normal circumstances, superficial permafrost layers about 50cm deep melt every summer. But now global warming is gradually exposing older permafrost layers.
Frozen permafrost soil is the perfect place for bacteria to remain alive for very long periods of time, perhaps as long as a million years. That means melting ice could potentially open a Pandora's box of diseases.
The temperature in the Arctic Circle is rising quickly, about three times faster than in the rest of the world. As the ice and permafrost melt, other infectious agents may be released.
“Permafrost is a very good preserver of microbes and viruses, because it is cold, there is no oxygen, and it is dark,” says evolutionary biologist Jean-Michel Claverie at Aix-Marseille University in France. “Pathogenic viruses that can infect humans or animals might be preserved in old permafrost layers, including some that have caused global epidemics in the past.”
In the early 20th Century alone, more than a million reindeer died from anthrax. It is not easy to dig deep graves, so most of these carcasses are buried close to the surface, scattered among 7,000 burial grounds in northern Russia.
However, the big fear is what else is lurking beneath the frozen soil.
This article is about frozen ground. For other uses, see Permafrost (disambiguation).
PermafrostMap showing extent and types of permafrost in the Northern HemisphereUsed inInternational Permafrost AssociationClimateHigh latitudes, alpine regions
Slope failure of permafrost soil, revealing ice lenses.
Permafrost is ground that continuously remains frozen for two or more years, located on land or under the ocean. Permafrost does not have to be the first layer that is on the ground. It can be an inch to over miles deep into the Earth's surface. Some of the most common permafrost locations are located in the Northern Hemisphere. Almost a quarter of the Northern Hemisphere is underlain by permafrost, including 85% of Alaska, Greenland, Canada, and Siberia. It can also be located in the Southern Hemisphere, just on mountain tops. Permafrost frequently occurs in ground ice, but it also can be presented in non-porous bedrock. Permafrost is formed from ice holding all different sorts of soil, sand, and rock combination together.
Study and classification of permafrost
“In contrast to the relative dearth of reports on frozen ground in north America prior to World War II, a vast literature on the engineering aspects of permafrost was available in Russian.
Beginning in 1942, Siemon William Muller delved into the relevant Russian literature held by the Library of Congress and the U.S.
Geological Survey Library so that he was able to furnish the government an engineering field guide and a technical report about permafrost by 1943″, year in which he coined the term as a contraction of permanently frozen ground. Although originally classified (as U.S.
Army. Office of the Chief of Engineers, Strategic Engineering Study, no. 62, 1943), in 1947 a revised report was released publicly, which is regarded as the first North American treatise on the subject.
Red lines: Seasonal temperature extremes (dotted=average).
Permafrost is soil, rock or sediment that is frozen for more than two consecutive years. In areas not overlain by ice, it exists beneath a layer of soil, rock or sediment, which freezes and thaws annually and is called the “active layer”. In practice, this means that permafrost occurs at an mean annual temperature of −2 °C (28.4 °F) or below. Active layer thickness varies with the season, but is 0.3 to 4 meters thick (shallow along the Arctic coast; deep in southern Siberia and the Qinghai-Tibetan Plateau). The extent of permafrost varies with the climate: in the Northern Hemisphere today, 24% of the ice-free land area, equivalent to 19 million square kilometers, is more or less influenced by permafrost. Of this area slightly more than half is underlain by continuous permafrost, around 20 percent by discontinuous permafrost, and a little less than 30 percent by sporadic permafrost. Most of this area is found in Siberia, northern Canada, Alaska and Greenland. Beneath the active layer annual temperature swings of permafrost become smaller with depth. The deepest depth of permafrost occurs where geothermal heat maintains a temperature above freezing. Above that bottom limit there may be permafrost with a consistent annual temperature—”isothermal permafrost”.
Continuity of coverage
Permafrost typically forms in any climate where the mean annual air temperature is less than the freezing point of water.
Exceptions are found in humid boreal forests, such as in Northern Scandinavia and the North-Eastern part of European Russia west of the Urals, where snow acts as an insulating blanket. Glaciated areas may also be exceptions.
Since all glaciers are warmed at their base by geothermal heat, temperate glaciers, which are near the pressure-melting point throughout, may have liquid water at the interface with the ground and are therefore free of underlying permafrost.
 “Fossil” cold anomalies in the Geothermal gradient in areas where deep permafrost developed during the Pleistocene persist down to several hundred metres. This is evident from temperature measurements in boreholes in North America and Europe.
The below-ground temperature varies less from season to season than the air temperature, with mean annual temperatures tending to increase with depth as a result of the geothermal crustal gradient.
Thus, if the mean annual air temperature is only slightly below 0 °C (32 °F), permafrost will form only in spots that are sheltered—usually with a northern or southern aspect (in north and south hemispheres respectively) —creating discontinuous permafrost.
Usually, permafrost will remain discontinuous in a climate where the mean annual soil surface temperature is between −5 and 0 °C (23 and 32 °F). In the moist-wintered areas mentioned before, there may not be even discontinuous permafrost down to −2 °C (28 °F).
Discontinuous permafrost is often further divided into extensive discontinuous permafrost, where permafrost covers between 50 and 90 percent of the landscape and is usually found in areas with mean annual temperatures between −2 and −4 °C (28 and 25 °F), and sporadic permafrost, where permafrost cover is less than 50 percent of the landscape and typically occurs at mean annual temperatures between 0 and −2 °C (32 and 28 °F).
In soil science, the sporadic permafrost zone is abbreviated SPZ and the extensive discontinuous permafrost zone DPZ. Exceptions occur in un-glaciated Siberia and Alaska where the present depth of permafrost is a relic of climatic conditions during glacial ages where winters were up to 11 °C (20 °F) colder than those of today.
|Qinghai-Tibet Plateau||1,300 km2 (500 sq mi)|
|Khangai-Altai Mountains||1,000 km2 (390 sq mi)|
|Brooks Range||263 km2 (102 sq mi)|
|Siberian Mountains||255 km2 (98 sq mi)|
|Greenland||251 km2 (97 sq mi)|
|Ural Mountains||125 km2 (48 sq mi)|
|Andes||100 km2 (39 sq mi)|
|Rocky Mountains (US and Canada)||100 km2 (39 sq mi)|
|Fennoscandian mountains||75 km2 (29 sq mi)|