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Satellite image of an ice shelf with a crack.
Photo Credit: German Aerospace Center (DLR)
A German satellite captures an image on July 8 of an iceberg forming to the left of Pine Island Glacier Ice Shelf. While the calving event is considered a natural phenomenon, the glacier upstream that feeds into the ice shelf is one of the fastest moving in Antarctica, contributing to sea-level rise.

Breaking away

Giant iceberg calves from Pine Island Glacier Ice Shelf

Nearly two years after NASA External U.S. government site scientists discovered a huge crack across the Pine Island Glacier (PIG) Ice Shelf, an iceberg bigger than the city of Chicago calved off into the Amundsen Sea.

Scientists at the Alfred Wegener Institute-Helmholtz Centre for Polar and Marine Research broke the news External Non-U.S. government site this week. They had been studying the ice shelf from space using a German satellite called TerraSAR-X External Non-U.S. government site. [View a time-lapse video External Non-U.S. government site of the calving iceberg.]

Satellite composite of an ice shelf.
Photo Credit: German Aerospace Center (DLR)
The combination of several satellite images gives an overview of the glacier (red outline), the flow direction (yellow) and the position of the crack (green).
Field camp on an ice field.
Photo Credit: August Allen/Antarctic Photo Library
A field camp set up during the 2012-13 Antarctic season on Pine Island Glacier, near the ice shelf where an iceberg recently calved off.

The iceberg measures about 720 square kilometers (Chicago is about 600 square kilometers). Scientists at the Polar Geospatial Center (PGC) External Non-U.S. government site at the University of Minnesota External Non-U.S. government site posted on their Facebook page External Non-U.S. government site this week that there is still a small remnant of the iceberg clinging to the rest of the ice shelf.

Pine Island Glacier (PIG) is the fastest flowing glacier in Antarctica, moving about 4,200 meters per year where it feeds into the ice shelf, which floats on the ocean. While PIG has been the focus of climate change studies in recent years, the calving of the ice shelf is believed to be a natural phenomenon.

The crack was first seen and photographed on Oct. 14, 2011, by scientists aboard NASA’s DC-8 External U.S. government site — a flying laboratory that boasts a suite of radars and other instruments —as part of Operation IceBridge External U.S. government site. [See previous article — Cracked: Rift spotted in Pine Island Glacier Ice Shelf before upcoming expedition.]

The six-year airborne campaign has conducted measurements of ice in the Arctic and Antarctic since 2009 after the Ice, Cloud, and land Elevation Satellite (ICESat) External U.S. government site was decommissioned that same year. NASA plans to launch ICESat-2 by 2016 to continue space-based monitoring of the polar regions.

The IceBridge project has been based out of Punta Arenas, Chile, during its previous field seasons. This year NASA plans to base the mission out of McMurdo Station External U.S. government site, the hub of the U.S. Antarctic Program External U.S. government site, which is managed by the National Science Foundation External U.S. government site.

During the 2012-13 season, U.S. and British scientists collaborated on a logistically intensive field project called PIG External U.S. government site (for PIne Island Glacier) to study the ice shelf. A team drilled through the 500-meter-thick ice shelf in three locations to deploy instruments below the ice shelf to learn about how the ocean below is melting the underside. [See previous article — Antarctica's ground zero: Expedition heads to Pine Island Glacier region to study thinning ice shelf — and NSF press release External U.S. government site.

The field work took place more than 15 kilometers south of the crack where the iceberg broke away from the ice shelf.

The thinning ice shelf allows the glacier behind it to flow faster. PIG, along with nearby Thwaites Glacier, are draining the most ice from the West Antarctic Ice Shelf. The entire ice shelf holds enough frozen water to raise sea level by an estimated five meters. The much larger and higher — and more stable — East Antarctic Ice Shelf would raise sea level by about 60 meters.

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