Iceberg larger than Chicago breaks off in Antarctica
Floating freely in Amundsen Sea, iceberg broke off from Pine Island Glacier
Floating freely in the Amundsen Ocean, a huge iceberg, larger than Chicago, broke off of Antarctica's Pine Island this week. German scientists say the newborn iceberg measures about 278 square miles and was seen by TerraSAR-X, an earth-observing satellite operated by the German Space Agency.
Satellite images in May of last year revealed a second rift had formed near the northern side of the first crack.
The fissure at that time spanned about 15 miles in length and 164 feet in width. Satellite images in May of last year revealed a second rift had formed near the northern side of the first crack.
"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 in a statement.
Humbert along with fellow scientists studied high resolution radar images taken by the TerraSAR-X satellite to track the changes in the two cracks.
"Using the images we have been able to follow how the larger crack on the Pine Island Glacier extended initially to a length of 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 1,770 feet at its widest point."
The way the ice breaks, or "calves," is still somewhat mysterious, Humbert notes.
"Glaciers are constantly in motion," she said. "They have their very own flow dynamics. Their ice is exposed to permanent tensions and the calving of icebergs is still largely unresearched."
The longest and fastest-changing on the West Antarctic Ice Sheet, the Pine Island Glacier ice shelf is the part of the glacier that extends out into the water. The glacier last produced large icebergs in 2001 and 2007.
While Humbert and her colleagues did not draw direct connections between this week's calving event and climate change, other scientists are investigating whether global warming is thinning Antarctica's ice sheets and speeding up the glacier's retreat.
Humbert says that the flow of the Pine Island Glacier may be driven by other factors. The glacier flows to the Amundsen Sea at a rate of about 2.5 miles per year. Whether the flow speeds up or slows down is based more on changing wind directions in the Amundsen Sea, and less by 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."
If the glacier's flow speeds up, it could have serious consequences, the researchers said. The Pine Island Glacier currently acts as a plug, holding back part of the immense West Antarctic Ice Sheet whose melting ice contributes to rising sea levels.
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