The Global Seed Vault is sometimes called the doomsday vault, as it is meant to store the Earth's genetic bounty in the event of a natural or human-made disaster that wipes out vital crops needed to sustain human and animal populations.

With a capacity to store 4.5 million crop varieties and 2.5 billion seeds, it's billed as the world's largest collection of crop diversity.

While the designers of the vault seem to have taken the possibilities of nuclear wars and global pandemics into account, they may have given too little thought to one other serious threat: global warming.

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The vault was purposefully constructed far away from major population centers, and was built 400 feet into an icy mountainside in Spitsbergen, Norway. The seed collection, currently numbering between 800,000 and 900,000 samples, is kept at a chilly temperature of minus-18 degrees Celsius, or about 0 degrees Fahrenheit.

Entrance to the Global Seed Vault in Spitsbergen, Norway. Image: Heiko Junge/Epa/REX/Shutterstock

The frozen soil surrounding the vault, known as permafrost, however, may turn out to be the vault's undoing as air and sea temperatures rise due to human-caused global warming. According to a report on Friday in The Guardian, a series of highly unusual wintertime heat waves during the 2016-17 winter resulted in enough thawing of the permafrost that water rushed into the vault's entrance.

Once inside the entrance, the water froze into ice as temperatures cooled again, before any water could penetrate the vault itself. However, the incident may have been enough to demonstrate that rapid Arctic climate change — the region is warming at twice the rate of any other area on Earth — could upend key assumptions used to build the vault, which opened with much fanfare just seven years ago.

Air temperature departures from average during the Arctic winter of 2016-17. Image: nsidc

"It was not in our plans to think that the permafrost would not be there and that it would experience extreme weather like that," Hege Njaa Aschim, from the Norwegian government, which owns the vault, told the Guardian.

"A lot of water went into the start of the tunnel and then it froze to ice, so it was like a glacier when you went in," she told the paper.

The seed bank was supposed to operate on autopilot, but right now, workers are watching it around the clock, Aschim told the UK newspaper. "We must see what we can do to minimize all the risks and make sure the seed bank can take care of itself."

In comments to Mashable on Monday, Aschim said any media stories about "flooding" in the vault were overblown.

"It was not flooding but a lot of rainwater — and it's unusual –- we have not experienced that before," she said in an email. However, she added, "The seeds and the vault [were] never at risk."

High temperatures and heavy rainfall in October 2016 caused "water intrusion" into the tunnel leading to the seed vault, she noted. Although the seeds were unaffected, she said the Norwegian government, which operates the vault, is consulting with climate researchers and taking other precautions to ensure "we do the right thing to protect the tunnel and the vault in the future."

"We will not take any chances," Aschim added.

Vault operators are making building improvements to minimize any water intrusion at the entrance to the vault. Some of these fixes include the removal of a power transformer to take away a heat source in the entranceway, as well as digging drainage ditches nearby.

Animation of temperature anomalies in the Arctic, showing record warmth in 2016/17. Image: zack labe

Operators published press statements over the weekend laying out the renovations in detail, making clear that they concern the entranceway to the vault rather than the area where the seeds are stored.

There is no question that the climate is warming faster throughout the Svalbard Archipelago than was anticipated just a couple decades ago.

And the melting of permafrost is not just putting the seed vault's original design at risk. It is also threatening to increase the rate at which greenhouse gases are pouring into the atmosphere, since as the frozen soil melts, bacteria within it break down organic matter and emit methane, carbon dioxide and other planet-warming gases. In addition, permafrost melt is destabilizing buildings, roadways, and other infrastructure in the Arctic, from Alaska to Siberia and beyond.

The past year was the warmest on record in the Arctic, and sea ice, which normally surrounds the Svalbard Archipelago, remained north of the area through much of January, which is unusually late, according to the National Snow and Ice Data Center in Boulder, Colorado.

A series of warm air pulses from the North Atlantic swept across Svalbard, including the location of the seed vault, pushing air temperatures well above the freezing point. Connected to major storm systems, these waves of above average air temperatures then swept across much of the high Arctic, at times bringing air temperatures near or just above freezing at the geographic North Pole as well.

Map of air temperature departure from avg. across the Arctic in Dec. 2016, with an arrow pointing to Svalbard. Image: nsidc

This pattern was partly due to a lack of sea ice across the Barents and Kara Seas, which provided a supply of moisture and warm air for these storms to tap into and draw into the central Arctic.

For example, on Dec. 21, 2016, the high temperature in Svalbard was 4.8 degrees Celsius, or 40.6 degrees Fahrenheit. This was nearly 19 degrees Celsius above average for the date. Similarly, on Feb. 6, 2017, Svalbard saw a high temperature of 5.9 degrees Celsius, or 42.6 degrees Fahrenheit, well above the average for the date, which was just minus-16.1 degrees Celsius, or 3 degrees above zero Fahrenheit.

Ryan Maue, a meteorologist at WeatherBell Analytics in the U.S., tweeted his suspicion about the Guardian story's accuracy on Friday, saying that if true, the vault must be relocated. However, winter conditions are variable there as weather systems pass through. The area where the vault is located is not in an area permanently surrounded by sea ice, for example.

On other hand, if rain-on-snow melt-water simply ran into the tunnel at bottom of mountain, then it's a weather event to mitigate. — Ryan Maue (@RyanMaue) May 19, 2017

These unusually mild days this winter were not isolated examples, either, as Svalbard saw more rain on snow events than average, and several other temperature spikes that threatened to break records.

The question now is whether there is anything the seed vault operators can do to bolster the facility's defenses against climate change and weather extremes, which will only grow worse in coming years.

One recent study that examined Svalbard climate trends during the past century found significant winter warming has taken place in the past few decades, and it projected that a typical winter in the year 2100 will be about 10 degrees Celsius milder than those today.

This story has been updated with comment from the Norwegian government on May 22, 2017.