WASHINGTON – The amount of ice in the Arctic Ocean shrank this summer to the sixth-lowest level on record, but that left much more ice than last year’s all-time 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 U.S. National Snow and Ice Data Center said Friday that Arctic ice covered 5.1 million sq. km when it stopped melting a week ago. It takes scientists several days to confirm sea ice has reached its lowest level and is growing again.

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

Center director Mark Serreze said cooler air triggered a “considerable recovery” from last year, while the ocean temperatures were still warmer than normal. But he added that 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 said. “We are not seeing a long-term recovery here.” Overall, Arctic sea ice since 1979 has been shrinking at about 12 percent per decade.