REPAIRS ARE underway to the entrance of the Svalbard International Seed Vault after an unexpected thaw of permafrost led to water leakage.

The building, situated on an Arctic island 620miles from the North Pole, was created to safeguard humanity's food supply by preserving stocks of seed for all the world's major crops. In theory, in the event of a world-wide cataclysm, whether man-made or natural, that destroys crops and conventional seed stores, the Svalbard Vault will offer survivors a means of restarting productive agriculture.

But one threat that the designers did not take into account was the possibility that the usually deep frozen location would suddenly get soggy. The water ingress, following the melt late last year, was mercifully limited to the building's entrance hall, and had no impact on the millions of rice, maize, potato and wheat seeds stored more than 110 meters inside the Svalbard mountainside.

"Svalbard Global Seed Vault is facing technical improvements in connection with water intrusion," stated the Norwegian state construction group Statsbygg, which built the vault that was officially opened back in 2008. Statsbygg has now removed electrical equipment from the entrance – which had been a source of heat – and is building waterproof walls inside and ditches outside to channel away any water. The number of visitors is also now to be reduced to limit human body heat.

Temperatures in the Arctic region have been rising at twice the global average in a quickening trend that climate scientists blame on man-made greenhouse gases, with the result that Svalbard has sometimes had rain even in the depths of winter when the sun does not rise.

"There's no doubt that the permafrost will remain in the mountainside where the seeds are," said Marie Haga, head of the Bonn-based Crop Trust that works with Norway to run the vault. "But we had not expected it to melt around the tunnel."

Ms Haga added that the trust had so far raised just over $200 million towards an $850 million endowment fund to help safeguard seeds in collections around the globe: "That is an extremely cheap insurance policy for the world," she said.