The 2011 maximum extent of Arctic sea ice appears to be tied for the lowest amount in area since satellite measurements began 32 year ago, U.S. researchers say.

Researchers at the University of Colorado Boulder said the maximum ice extent was 463,000 square miles below the 1979-2000 average, an area slightly larger than the states of California and Texas combined, a CU-Boulder release said Wednesday.

The measurements tied with those from 2006 as the lowest maximum sea ice extents measured since satellite record keeping began in 1979, they said.

Climate scientists say they believe shrinking Arctic sea ice is tied to warming temperatures in the region, caused by an increase in human-produced greenhouse gases in Earth's atmosphere.

Citing the downward trend of Arctic sea ice extent in the last decade, some University of Colorado scientists are predicting the Arctic Ocean may be ice free in the summers within the next several decades.

"I think one of the reasons the Arctic sea ice maximum extent is declining is that the autumn ice growth is delayed by warmer temperatures and the ice extent is not able to 'catch up' through the winter," Walt Meier of CU-Boulder's National Snow and Ice Data Center said. "In addition, the clock runs out on the annual ice growth season as temperatures start to rise along with the sun during the spring months."