A block of ice four times the size of Manhattan has split off from a Greenland glacier and melted--an event so dramatic that it's shocked the scientists who study the area.

Alun Hubbard of Aberystwyth University, Wales, said he was rendered "speechless" when he saw the now much smaller Petermann glacier. The break happened in 2010, but this is the first time photos have been available.

"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 breakup, which rendered me speechless," Hubbard said in a statement. The scientist said no similar event has happened in Greenland since recorded observations began in 1876.

Scientists now worry that another block of ice--about two times the size of Manhattan--is preparing to break off, according to the New York Times.

Ohio State University Professor Alan Box, who also studies the Petermann glacier, told the Times that observers do not know whether the region's rising water and air temperatures contributed to the deterioration of the ice. Researchers they don't have data that goes far back enough in time to document the water temperature beneath the ice.

Greenland's ice sheet may be melting at the rate of 400 billion tons per year. According to MSNBC, Greenland has lost "592.6 square miles of ice between 2000 and 2010."