Faint hopes for Arctic sea ice recovery as levels drop to 4th lowest on record

Summer Arctic sea ice shrank to its fourth lowest level on record this month, dispelling faint hopes of a recovery, U.S. scientists said.

The National Snow and Ice Data Center announced Tuesday that Arctic ice hit its summer minimum last week with 4.4 million square kilometres of sea ice, down 620,000 square kilometres from 2014.

"The ice is decreasing over time, which you would expect as the Arctic is warming," data centre scientist Julienne Stroeve said.

Summer minimum sea ice has shrunk since satellites began measuring in 1979. It reached a peak of 7.5 million square kilometres in 1980 and hit an all-time low of 3.3 million square kilometres in 2012. It went back up to 5 million square kilometres in 2013 and hovered near there in 2014.

Variations in weather mean sea ice levels drift a bit year to year, but Stroeve said there's a long term trend that is best seen when looking at averages of five years or more.

The five years between 1979 and 1983 averaged 7.15 million square kilometres during the summer minimum. The last five years averaged 4.45 million square kilometres, a decrease of 38 per cent.

That means there's no recovery in Arctic sea ice, despite claims of some climate change doubters, said Stroeve and Pennsylvania University climate scientist Michael Mann, who wasn't part of the government measurement team.

The world overall so far this year is easily the hottest it has been in more than a century of record keeping, according to NASA and the National Oceanic and Atmospheric Administration. However, the El Nino that has been helping push temperatures even warmer isn't having as much an effect up North, which is farther away from the tropical Pacific Ocean, Stroeve said. It has been hot, but not near record-breaking in the Arctic this summer.

With human-caused warming continuing, computer simulations show on average that around the year 2040, sea ice will disappear from the Arctic during some summers, Stroeve said.

"We remain on a trajectory that is actually ahead of model predictions," Mann said. "Arctic sea ice is one of several aspects of climate change that is happening even faster than predicted."

Sea ice in Antarctica, which had been at record high levels recent years, are about average, Stroeve said.