New photographs taken of a vast glacier in northern Greenland have revealed the astonishing rate of its breakup, with one scientist saying he was rendered "speechless."
In August 2010, part of the Petermann Glacier about four times the size of Manhattan island broke off , prompting a hearing in Congress.
Researcher Alun Hubbard, of the Centre for Glaciology at Aberystwyth University, U.K., told msnbc.com by phone that another section, about twice the size of Manhattan, appeared close to breaking off.
In 2009, scientists installed GPS masts on the glacier to track its movement.
But when they returned in July this year, they found the ice had been melting so quickly — at an unexpected 16-and-a-half feet in two years — that some of the masts stuck into the glacier were no longer in position.
Hubbard, who has been working with Jason Box, of Ohio State University, and others, said in a statement issued by the Byrd Polar Research Center that scientists were still trying to work out how fast the glacier was moving and the effect on the ice sheet feeding the glacier.
But he said he was taken aback by the difference between 2009 and 2011 when he visited the glacier in late July.
"Although I knew what to expect in terms of ice loss from satellite imagery, I was still completely unprepared for the gob-smacking scale of the break-up, which rendered me speechless," he said in the statement.
"I'm very familiar with the glacier. It's very hard to sort of envisage something so big not being there ... to come back and basically see an ice shelf has disappeared, which is 20 kilometers across (about 12 miles) ... I was speechless and started laughing because I couldn't sort of believe it," Hubbard added, speaking to msnbc.com.
"It was really weird when the helicopter first came over," he added.
Hubbard told msnbc.com that he had gone to the glacier to recover instruments used to monitor the glacier and time-lapse photographs.
"What I saw there is this ice shelf is riddled with rifts and cracks. You can see another big rift another 10 to 15 kilometers (6 to 9 miles) back into" the glacier, he said.
Hubbard said the large rift, which the researchers have dubbed "The Big Kahuna," was getting bigger. He was cautious about predicting when it would create a new vast ice island, but said it could happen "maybe next year, something like that."
He said while sea glacier's "calving" of ice bergs was a natural process, they were witnessing something out of the ordinary.
"The break-off last year is bigger than anything seen for at least 150 years," Hubbard said.
"This region (northern Greenland) is experiencing temperatures which are abnormally warm ... I think the far northwest of Greenland is seeing a kind of new regime of climate," he added.
The Humbolt Glacier, the widest in the northern hemisphere, is also retreating, Hubbard said. He said he was not a climate scientist, but said the pattern of ice melting in the area was "a definite consequence of climate change and global warming."
Writing in the Annals of Glaciology journal, published on Aug. 22, the researchers said Greenland's glaciers had collectively lost 592.6 square miles of ice between 2000 and 2010.
The August 2010 "calving" event saw the creation of an ice island of 112 square miles, causing the Petermann Glacier to retreat by about 8 miles.Story: Giant ice island breaks off Greenland
The island contained enough water to keep the Delaware or Hudson rivers flowing for two years or to provide the entire U.S. with tap water for 120 days, Andreas Muenchow, professor of ocean science and engineering at the University of Delaware, said at the time.
The Byrd center statement, which summarized the journal report, said while this loss of ice was "extreme compared with others ... it is part of a larger pattern of ice area loss concentrated in north Greenland."Story: Greenland glaciers show record losses
Twice as many glaciers are retreating as the number that are advancing, and the area of ice lost was nine times the amount gained, the researchers found.
'Harbinger of many changes'
At the Congressional hearing in August 2010, the then chairman of the Select Committee on Energy Independence and Global Warming, Rep. Edward Markey, said the melting of the Greenland ice sheet was "but one harbinger of the many changes to come."
"Scientists, skeptical by both nature and training, always urge a dose of caution when looking at any one event as evidence of climate change," he said in his opening statement. "This level of professional skepticism is what makes the overwhelming scientific consensus that climate change is real and caused by man all the more powerful."As Greenland ice thins, shoot the dogs, drill for oil
Markey listed extreme weather events, such as a record-breaking heatwave and drought in Russia, extreme floods in Asia, record-breaking temperatures on the Eastern Seaboard of the United States and "mega storms and floods" in many parts of the country.
"Take a step back from these individual pieces and we see a mosaic that could not be clearer. Our world is becoming less hospitable with every passing year," he added.
© 2013 msnbc.com Reprints