Arctic ice melting may have accelerated to a "tipping point" that will produce a vicious cycle of melting and heating, U.S. scientists say.

Another record loss of sea ice in the Arctic this summer is expected by Arctic specialists at the National Snow and Ice Data Center at Colorado University, who have been studying polar sea ice since 1978, the Independent reported Friday.

Scientists fear that the Arctic has now entered an irreversible phase of warming that will further accelerate the loss of the polar sea ice creating a rise in ocean levels.

In the past, polar ice would melt in the summer and refreeze in the winter, however, for the fourth year in a row the sea ice in August has fallen below the monthly downward trend -- indicating the melting has accelerated.

"This will be four Septembers in a row that we've seen a downward trend," said Mark Serreze, a scientist at the Snow and Ice Data Center. "The feeling is we are reaching a tipping point or threshold beyond which sea ice will not recover."

Copyright 2005 by United Press International