Beaufort Sea
The sea is frozen over most of the year. Only a narrow pass up to  opens in August–September near its shores. The seacoast was populated about 30,000 years ago. The sea has many resources of petroleum and natural gas. They were discovered between the 1950s and 1980s.  People started exploring the resources in the 1980s. There is a large amount of beluga whales. The United States and Canada do not agree about the sea border.