Researchers at the University of Colorado's National Snow and Ice Data Center said the average sea ice extent for the month of September was 1.65 million square miles -- the lowest September on record -- shattering the 2005 September record by 23 percent. At the end of the melt season, September sea ice was 39 percent below the long-term average from 1979 to 2000.

If ship and aircraft records from before the satellite era are taken into account, scientists said sea ice coverage might have fallen by as much as 50 percent from the 1950s.

"The sea ice cover is in a downward spiral and may have passed the point of no return," said NSIDC researcher Shari Gearheard. "As the years go by, we are losing more and more ice in summer, and growing back less and less ice in winter.

"We may well see an ice-free Arctic Ocean in summer within our lifetimes," added Professor Mark Serreze. "The implications for global climate, as well as Arctic animals and people, are disturbing."