FYI. Breaking news from NASA on Antarctica’s Pine Island Glacier (PIG) where a 72 square mile chunk of ice calved from the ice shelf in early April. The iceberg appears to shatter upon calving. Pine Island Glacier is an enormous ice stream, and is the fastest melting glacier in all of Antarctica, responsible for about 25% of Antarctica's ice loss. It is located in the highly vulnerable region of West Antarctica.
Notice the rift is in the center of the glacier. It does not appear to be attached or grounded.
A new iceberg calved from Pine Island Glacier—one of the main outlets where ice from the interior of the West Antarctic Ice Sheet flows into the ocean.
The Operational Land Imager (OLI) on the Landsat 8 satellite captured this natural-color image on September 21, 2017, just before the break. A rift is clearly visible across the center of the glacier’s floating ice shelf.
The break ultimately produced iceberg B-44, visible in radar imagery captured September 23 with the European Space Agency’s Sentinel-1 satellite. The new berg, afloat in the Amundsen Sea Embayment, has an area of about 185 square kilometers (72 square miles). That’s larger than the pieces that broke away in January 2017, but smaller than the 583-square-kilometer (225-square-mile) berg that was spawned in July 2015.
References U.S. National Ice Center (2017, September 25) Iceberg B-44Calves off Pine Island Glacier into the Amundsen Sea. Accessed September 26, 2017. xAnother calving event at Pine Island Glacier as seen by @Copernicus#sentinel1 as the rift as the SW ice shelf released multiple small icebergs. It will be interesting how the rest of this high damage area will react. pic.twitter.com/PxwLNoaF4w
— Stef Lhermitte (@StefLhermitte) April 4, 2018I shared a story a couple of months ago on the late September 2017 calving at Pine Island Glacier. After moving away from the shelf that berg shattered. They aren’t supposed to crumble like that. They should be intact and break up only when they reach the open ocean. We now have confirming evidence that something new and frightening is going on at Pine Island Glacier. The link below has the September image of the break and provides information on the shattering of that 225 sq mile iceberg. Yikes.
A Giant Iceberg in West Antarctica Is Disintegrating, And Scientists Are Worried.
While the fracturing process itself might seem unremarkable, the way the iceberg broke free from the glacier was not, scientists say, and could signal an alarming new precedent in calving processes.
"What we're witnessing on Pine Island Glacier is worrying," explains marine geophysicist Robert Larter from the British Antarctic Survey.
"We're now seeing changes in the calving behaviour of the ice shelf, when for 68 years we saw a pattern of advance and retreat resulting in the calving of a single large iceberg which left the ice front to approximately the same place."
Unlike those events, which effectively replenished the footprint of the up-to-60 metre tall (197 ft) ice front, continued thinning of the glacier as a whole has produced what scientists fear may be evidence of a new era of structural instability.
"What's both interesting and of concern is the lines along which the iceberg has broken follow the pattern of crevasses developed in the ice shelf that it calved from," Larter says.
"This change of behaviour might reflect the crevasses within the ice shelf having an increasing influence on the spacing and pattern of iceberg calving as a result of the thinning that has taken place over the past few decades."
This calving signature – if that's what it is – could foretell a disturbing trend in the Pine Island Glacier, which accounts for about a quarter of all of Antarctica's ice loss, thought to be some 40 billion tonnes of ice each year.