Little White and Little Grey will be taken next year from Changfeng Ocean World to Klettsvik Bay, organisers told a press conference at the Sea Life London Aquarium on June 26.
The 12-year-old female cetaceans will still be in human care in the netted-off sea inlet as it is thought they will never survive on their own in the wild.
But the founders said it will give them a better life – and help research into how captive whales could one day be prepared for release out of human dependency.
British-based Merlin Entertainments operates attractions including Legoland, The Tussauds Group and the Sea Life aquarium.
It took over Changfeng Ocean World in 2012 and started looking for a new environment to house Little White and Little Grey.
Originally from Russian Arctic waters, it is thought they were two or three years old when captured. They weigh around 900 kilograms and are around four metres long.
Their 30-hour transfer planned for next year will involve stretchers and transport semi-submerged in tanks, by truck, chartered flight and then ferry.
They will be assessed in a care pool before being released into Klettsvik Bay at Heimaey, one of the Westman Islands off the south coast of Iceland.
The bay, which is leased, measures up to 32,000 square metres with a depth of up to 10m.
Klettsvik is where Keiko, the killer whale in the 1993 film “Free Willy”, was flown to in 1998. The orca was fully released in 2002 but did not fully adapt to life in the wild and died 18 months later in a Norwegian fjord.
“We hope that by showing the way with our sanctuary, we will help to encourage the rehabilitation of more captive whales into natural environments and one day bring an end to whale and dolphin entertainment shows,” said Andy Bool, head of the Sea Life Trust charity.
Campaigners have criticised Merlin for continuing the beluga whale shows ahead of the transfer and pointed to the irony of choosing Iceland as a destination since it openly defies an international ban on hunting whales.
The Shanghai whales are being trained to hold their breath for longer, become physically stronger to cope with tides and currents, and are putting on blubber to help them cope with the colder water temperatures.
A third beluga whale at the aquarium, Jun Jun, died from a bleed on the brain in June last year, aged 17.
Belugas typically live for 40 to 60 years.
More than 3,000 whales and dolphins are kept in captivity and it is hoped that up to eight other belugas could join Little White and Little Grey in the future.
“There is a real alternative now for these animals,” Bool said.
“The argument has been in the past that you can’t just put them back in the sea – and that’s right. But hopefully, people will see what we’re doing and want to replicate it.”
Cathy Williamson, from the Whale and Dolphin Conservation charity, said public support for aquarium shows was waning.
“The world’s first whale sanctuary presents a pathway towards the end of the keeping of whales and dolphins in captivity,” she said.