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July 16th, 2012 - the Petermann Glacier in northwest Greenland

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lost a massive iceberg, for the second time in three years.

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As the ice floating in the fjord broke up, the ice island was carried by the current

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down the glacier's outlet channel and toward the Nares Strait.

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Known as Petermann Ice Island 2012, it was about 12 square miles -

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half the size of Manhattan - and floating at one kilometer per day.

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NASA's Aqua and Terra satellites made multiple passes each day over the polar regions,

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allowing scientists to track the ice island - whenever clouds didn't block the view.

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Scientists have been watching this crack develop since 2001.

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Ocean temperatures are one factor determining when glaciers will calve an iceberg.