The amount of ice in the Arctic Ocean shrank this summer to the sixth lowest level, but that is much higher than last year's record low.

The ice cap at the North Pole melts in the summer and grows in winter; its general shrinking trend is a sign of global warming. The National Snow and Ice Data Center said Friday that Arctic ice was at 1.97 million square miles (5.1 million sq. kilometers) when it stopped melting late last week.

It takes scientists several days to confirm sea ice hit reached its lowest level and is growing again.

The minimum level reached this summer is about 24 per cent below the 20th Century average, but 50 per cent above last year when a dramatic melt shattered records that go back to 1979.

Center director Mark Serreze says cooler air triggered a "considerable recovery," from last year, while the ocean temperatures were still warmer than normal. But he adds climate change deniers who point to the bounce back from last year — which skewed the trend — would be wrong.

"If you threw out last year, this year would be very much in line of what we've seen in recent years," Serreze says. "We are not seeing a long term recovery here. No way."

Overall, since 1979 Arctic sea ice has been shrinking at a "pretty darn big" rate of about 12 per cent per decade and "this is not going to reverse your trend, not in the least," Serreze says.