An iceberg in Antarctica that is bigger than Chicago recently broke off a glacier and is now floating free in the ocean.

The gigantic iceberg broke off Antarctica's Pine Island Glacier on Monday; the iceberg is currently floating freely in the Amundsen Sea, German scientists reported.

The iceberg that broke off is about 278 square miles, and thus bigger than Chicago.  It was spotted by TerraSAR-X, an earth-observing satellite that the German Space Agency (DLR) operates.

The Pine Island glacier ice shelf is the fastest-changing and longest glacier in Antarctica. Global warming may have to do with Antarctica's ice sheets being thinned and the glacier retreating faster.

As the Pine Island glacier retreats and melts, the way ice shears off, or "calves", into icebergs is mysterious, Humbert said.

"Glaciers are constantly in motion. They have their very own flow dynamics. Their ice is exposed to permanent tensions and the calving of icebergs is still largely unresearched."

The speed of the melt of icebergs in Antarctica may actually have to do with wind directions in the Amundsen Sea, rather than rising air temperatures.

"The wind now brings warm sea water beneath the shelf ice," Humbert said. "Over time, this process means that the shelf ice melts from below, primarily at the so-called grounding line, the critical transition to the land ice."

However, because the Pine Island Glacier is a "plug" that holds back massive the West Antarctic Ice Sheet, the flow speeding up may portend grave consequences.

Back in October 2011, scientists with NASA's Operation IceBridge first discovered a giant crack in the Pine Island Glacier in Antarctica. A second rift formed near the first crack in May 2012.

"As a result of these cracks, one giant iceberg broke away from the glacier tongue," Angelika Humbert, a glaciologist at the Alfred Wegener Institute, said to press.

Another researcher from the Alfred Wegener Institute, Nina Wilkens, explained,

"Using the images we have been able to follow how the larger crack on the Pine Island Glacier extended initially to a length of 28 kilometers (17 miles)," Nina Wilkens, one of the team researchers from the Alfred Wegener Institute, said in a statement. "Shortly before the 'birth' of the iceberg, the gap then widened bit by bit so that it measured around 540 meters (1,770 feet) at its widest point."