A Gold Coast theme park is celebrating after the birth of two polar bear cubs.

Sea World marine scientist Trevor Long says the cubs' delivery last Wednesday to the park's 16-year-old female Liya is "critical" to the long-term survival of polar bears.

The twins are the third and fourth cubs to be born at the park's Polar Bear Shores exhibit since it opened in 2000.

Henry and another cub, which didn't survive, were born in 2013 to Liya, and Mr Long says the new arrivals continue to highlight the importance of the park's exhibit.