In Arctic Svalbard, there is a vault that might sound like a sci-fi plot device. Completed in 2008, the Global Seed Vault is a remote archive for safeguarding seeds for thousands of crop varieties. If anything dramatic should happen elsewhere around the world, we want these seeds to be there.

The vault consists of a giant freezer room bored into a mountain, protected by the bedrock around it and the permafrost above it. But according to a report in The Guardian, the vault experienced an unhappy surprise recently—melting permafrost in winter.

The Arctic just experienced its second-warmest winter on record (surpassed only by 2016), and Svalbard saw remarkable temperatures and even rain. In fact, Svalbard averaged more than 4 °C above even the 2004-2013 average.

As a result, meltwater trickled into the seed vault’s entrance tunnel before refreezing. The freezer room itself was safe, but the ice in the tunnel had to be chipped out. Hege Njaa Aschim, a spokesperson for the Norwegian government, told The Guardian, “It was supposed to [operate] without the help of humans, but now we are watching the seed vault 24 hours a day.”

Whether or not these conditions become common as the Arctic warms, precautions are being taken to avoid a repeat of this event. Precautions include waterproofing improvements for the entrance tunnel and drainage channels to divert meltwater. It might take a little more than sticking a freezer inside an Arctic mountain to keep these seeds cold and safe, it seems.