Scientists watch birth of huge Antarctic iceberg

When the massive chunk of ice is fully separated from its even more massive parent ice, expected to happen within a few weeks, it will measure about 308 square miles, scientists say. That's about the size of New York City.

The formation of an iceberg is called calving, and although it's a fairly regular event - probably unrelated to global warming - scientists are awaiting this one with considerable anticipation. Icebergs this big calve off only about once every 10 years.

Claire Parkinson, a climate scientist at the NASA Goddard Space Flight Center in Maryland, said the event would be dramatic.

"When icebergs calve off, it's actually quite a loud noise," she said. "It would definitely be something you would hear - like a loud cracking sound - and visually it would be interesting too because there would be different pieces calving off at the same time, and some of them would end up turning upside down and sideways."

It would be fun to see only from a significant distance, she said. "If you were standing in the midst of it, you would be in a great deal of danger."

Adding to NASA's excitement is that scientists happened to catch the iceberg in the midst of calving.

In mid-October, scientists who monitor Antarctic ice flew to the Pine Island Glacier as part of a project called Operation IceBridge, which NASA describes as "the largest airborne survey of Earth's polar ice ever flown." The scientists were planning to take regularly scheduled measurements of the ice shelf in western Antarctica, when they noticed a giant crack.

"A lot of times when you're in science, you don't get a chance to catch the big stories as they happen because you're not there at the right place at the right time. But this time we were," John Sonntag, instrument team leader for Operation IceBridge, said in a statement. The operation is based at the Goddard Space Flight Center.

The crack, which formed in late September or early October, is fairly dramatic. It's 18 miles long, with shoulders about 820 feet apart at the rift's widest. The crack is about 260 feet wide along most of its length.

Sonntag said the process of an iceberg calving is a discrete event, taking place over just a few weeks.

"We just happened to be here at the right window of time to capture it," he said.

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