Ice in the Arctic Ocean melted faster last month than it has in 30 previous Junes.

The satellite measurements collected in June show the extent of the sea ice was about 10.87 million square kilometres, according to figures released by the U.S. National Snow and Ice Data Centre. That's 1.3 million square kilometres below the average cover seen in the month from 1979-2000.

The findings follow a similar record-breaking retreat in May.

The most dramatic decline in sea ice is traditionally seen during the summer melt, says the Colorado-based institute on its website.

But in June "Arctic air temperatures were higher than normal and Arctic sea ice continued to decline at a fast pace," the institute said.

The ice was declining an average of 88,000 square kilometres per day in June.

The decline is partially related to the melt in Hudson Bay, the institute said. Usually Hudson Bay still has ice well into July, but it is already virtually clear this year, the institute said.

The Nares Strait — between Ellesmere Island and Greenland — also broke up in May, clearing the way for the flow of thick ice from the Arctic Ocean into warmer waters, the institute said.