A "warm, crazy" winter has left sea ice in the Arctic at its lowest levels on record for the season, scientists said.
It is the second year in a row in which the record has been broken for the lowest area of ice in winter - a time when cold temperatures see the ice sheet over the North Pole increase to a maximum extent before melting again during the summer.
This year, air temperatures over the Arctic Ocean for December, January and February were 2C to 6C (4F to 11F) above average in nearly every region, the US's National Snow and Ice Data Centre (NSIDC) and Nasa experts said.
NSIDC director Mark Serreze said: "I've never seen such a warm, crazy winter in the Arctic. The heat was relentless."
Sea ice extent over the Arctic Ocean averaged 5.607 million square miles (14.52 million square kilometres) at its peak extent on March 24, below last year's record low of 5.612 million square miles (14.54 million square kilometres), the experts said.
It is 431,00 square miles (1.12 million square kilometres) below the 1981 to 2010 average for the maximum coverage of Arctic sea ice in the winter.
The maximum extent for the winter was reached later than average in the 37-year satellite record, setting up a shorter than average spring and summer ice melt season, the scientists said.
Minimum sea ice coverage, which is at its lowest extent around September, has been receiving attention since 2005 when it first shrank to a record low, with the record broken again in 2007 and in 2012.
Now the Arctic is seeing record lows for its maximum winter ice coverage too.
Ted Scambos, NSIDC lead scientist, said: "The Arctic is in crisis. Year by year, it's slipping into a new state, and it's hard to see how that won't have an effect on weather throughout the northern hemisphere."