The marshy, tundra landscape surrounding Newtok is seen from a plane on July 6, 2015, outside Newtok, Alaska.

(Andrew Burton/Getty Images)

At a Glance

Researchers say thawing permafrost could release dangerous pathogens.The Intergovernmental Panel on Climate Change estimates that the area of the permafrost will decrease 20 to 35 percent by 2050.

There could be something worrisome lying beneath the surface of the Arctic.

According to researchers, an untold number of dangerous pathogens and diseases frozen beneath the ground for millenniacould be unleashed as the Arctic's permafrost melts.

In fact, microbes frozen for decades and later thawed are to blamefor several deadly animal outbreaks and at least one human death in recent years.In the summer of 2016, believed to have been released from the thawing carcass of a frozen reindeer. Another 90 residents in the remote northern Russia region were hospitalized with the disease.

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The permafrost is the layer of frozen soil that covers . It can act like a giant freezer, preserving carbon and pathogens for decades or even millennia.But global warming is thawing the permafrost to a greater degree every year, increasing the likelihood that frozen diseases will be exposed to animals and humans.

The Intergovernmental Panel on Climate Change estimates that the , while the United Nations Environmental Programme estimates the .

French biologists Jean-Michel Claverie and his wife Chantal Abergel, both professors atAix-Marseille University in France, have spent decades studying microbes and have most recently turned their attention to the dangers lying deep in the permafrost. They note that it's not necessarily the known bacteria, viruses and other pathogens thatare worrisome but those that are unknown to the scientific community.

“There are hints that Neanderthals and Denisovans could have settled in northern Siberia and were plagued byvarious viral diseases, some of which we know, like smallpox, and ,” Claverie told ScientificAmerican. “The fact that there might be an infection continuity between us and ancient hominins is fascinating – and might be worrying.”

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A Russian study published in 2011 cataloged numerous deadly outbreaks of anthrax in Siberia between 1949 and 1993, while cases of anthrax in animals were recorded in 28,986 settlements of the Russian Federation. All are believed to have been a result of the melting permafrost.

“As a consequence of permafrost melting, the vectors ofdeadly infections of the 18th and 19th centuries may come back, especially near the cemeteries where ,” reads the study, published in the journal Global Health Action.

Russian scientists Boris A. Revich and Marina A. Podolnaya wrote in that "as a consequence of permafrost melting, the vectors of deadly infections of the 18th and 19th centuries may come back, especially near the cemeteries where the victims of these infections were buried."

Whether a pathogen survives the freezing temperatures of the permafrost all depends on the hardiness of the bacteria, virus or another microbe. Anthrax,for example, is particularly hardy.

"Most viruses are rapidly inactivated outside host cells, due to light, desiccation," Claverie toldBBC.com. "For instance, if their DNA is damaged beyond possible repair, the virions will no longer be infectious. However, among known viruses, the giant viruses tend to be very tough and almost impossible to break open."

It's not just the danger of disease that is worrisome as the permafrost melts, according to scientists like microbiologist Janet Janssonof the Department of Energy's Pacific Northwest National Laboratory.

"Estimates are that permafrost stores between 780 and 1,400 gigatons of terrestrial carbon. That's a huge reservoir. What happens whenpermafrost thaws and trapped carbon " she said in a 2015 press release. "The microbes in permafrost are part of Earth's dark matter. We know so little about them because the majority have never been cultivated and their properties are unknown."