OSLO, Norway — Refrigeration units on Friday begin cooling a new doomsday vault dug into an already frigid Arctic mountainside to protect the world’s seeds in case of a global catastrophe.

Norway blasted the Svalbard Global Seed Vault deep into the permafrost of a remote Arctic archipelago to protect as many as 4.5 million of the world’s agricultural seeds from climate change, plant epidemics, natural disasters or war. It is due to open Feb. 26.

The Svalbard Archipelago, 300 miles north of the mainland, was selected because of its remote location far from many threats, as well as for its cold climate and permafrost.

“It’s very satisfying to see the vault evolve from a bold concept to an impressive facility that has everything we need to protect crop biodiversity,” said Norway’s agriculture minister, Terje Riis-Johansen.

Norway first proposed building what it called a “Noah’s Ark” for the world’s seeds in June 2005, and started construction a year later, blasting a nearly 400-foot tunnel into a frozen mountain and placing the vault for foil-wrapped seeds deep inside. Each sample holds about 500 seeds.

Over the next two months, powerful cooling units will bring its temperature down to the target of about zero degrees from the current 23 degrees.