An ice island four times as big as Manhattan has been calved by a glacier in Greenland, the biggest such breaking off of Arctic ice since 1962, researchers say.

Scientist at the University of Delaware said the huge floating mass broke free from the Petermann glacier early Thursday about 620 miles from the North Pole, a university release said.

The glacier lost about one-quarter of its 43-mile long floating ice-shelf, researchers said.

The Petermann glacier is one of the two largest glaciers in Greenland that terminate in floating shelves and connects the Greenland ice sheet directly with the ocean.

The new ice island is at least 100 square miles in area, Andreas Muenchow, associate professor of physical ocean science and engineering at the University of Delaware, said.

"The freshwater stored in this ice island could keep the Delaware or Hudson rivers flowing for more than two years. It could also keep all U.S. public tap water flowing for 120 days," Muenchow said.

earlier related report
Ice age permafrost unearthed in Poland to help clock warming
Warsaw (AFP) Aug 6, 2010 - Permafrost dating from the end of the last Ice Age around 13,000 years ago recently discovered in Poland could prove an invaluable tool in gauging global warming, Polish geologists said on Friday.

The unique discovery of pre-historic permafrost was made on Monday in a corner of north-eastern Poland bordering Lithuania, near the village of Szypliszki.

Geologists drilling at the site were astounded to find the temperature of the drill cores decreasing rather than increasing -- as is normally the case -- the deeper they went.

The core containing ancient frost is the first of its kind found in central Europe and is an invaluable source of information about the climate on the Earth tens of thousands of years ago, the Polish geologists said.

Usually, similar valuable information can be derived from ancient cores found in Antarctica or Greenland.

"It is like touching cold that is 13,000-years-old," Professor Jerzy Nawrocki, director of the Polish Geological Institute (PGI), told reporters in Warsaw on Friday.

"On August 3, our scientists noted 0.07 degrees Celsius (32.12 Fahrenheit) at a depth of 356 meters (389 yards) in an exploratory borehole," he said, adding the finding "confirms the hypothesis of scientists that glaciers were present in Poland".

"Our discovery is important especially in relation to present discussions about global warming," said fellow-PGI Professor Jan Szewczyk, who heads the research project.

"In order to be able to build reliable models of future climate changes, we need to have trustworthy data from the past," he said.