July 10, 2013
Massive Iceberg Breaks Off Pine Island Glacier In Antarctica
Brett Smith for redOrbit.com - Your Universe Online
One of the Earth's most watched glaciers, Pine Island Glacier (PIG), has released a massive iceberg about eight times the size of Manhattan Island, according to images released by the German Space Agency (DLR).
The ice chunk was part of the PIG's ice shelf, which floats on and pushes out into the Southern Ocean for tens of miles. A relatively common occurrence that scientists aren't blaming directly on global warming, similar iceberg-creating events took place in 2007 and 2001.
NASA scientists spotted the first sign of an iceberg breaking away, the first crack, on October 14, 2011 when flying over the PIG.
"As a result of these cracks, one giant iceberg broke away from the glacier tongue," said Angelika Humbert, ice researcher at the Alfred Wegener Institute in Bremerhaven, Germany. "It measures (280 square miles) and is therefore almost as large as the city of Hamburg."
The German scientist and her colleagues used radar imagery from the DLR satellite TerraSAR-X to observe the progress of cracks in the glacier, hoping to glean a better understanding of the glacier's movements.
"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)," said Humbert's colleague Nina Wilkens, a recent PhD graduate. "Shortly before the birth of the iceberg, the gap then widened bit by bit so that it measured around (1800 feet) at its widest point."
The German glacierologists used their observations to create computer simulations using a model of the break and flow mechanisms of the 'calving' process.
"Glaciers are constantly in motion," Humbert said. "They have their very own flow dynamics. Their ice is exposed to permanent tensions and the calving of icebergs is still largely unresearched."
Essentially ruling out climate change, Humbert said wind conditions over the nearby Amundsen Sea have forced warmer water under the ice shelf, stressing the glacier from below. She said the only surprise was that the process took two years to complete.
"The wind now brings warm sea water beneath the shelf ice," she 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."
The world's largest recorded iceberg, B-15, separated from the Ross Ice Shelf in 2001 with an initial size of about 4,200 square miles and took years to melt. Scientists are expected to track the new iceberg as it floats out to sea -- most likely relying on TerraSAR-X to provide high resolution radar images.
The PIG has been under scientific scrutiny for some time because it drains about 10 percent of all the ice flowing off the western Antarctic.
"The PIG is the most rapidly shrinking glacier on the planet," Prof. David Vaughan from the British Antarctic Survey (BAS) recently told BBC News. "It's losing more ice than any other glacier on the planet, and it's contributing to sea level rise faster than any other glacier on the planet. That makes it worthy of study."
Image Below: On the left-hand side the newly formed iceberg with a size of 436 square miles is visible. Credit: DLR