The newest iceberg to demolish Pine Island Glacier is big enough to cover Manhattan five times with ice.
Credit: Landsat OLI Images Processed by Stef Lhermitte, Delft University of Technology
A huge iceberg, about five times Manhattan, broke off the Antarctic-Pine Island Glacier yesterday (1
Ever since he discovered the crack in early October, Lhermitte had guessed that the icebergs would take weeks or months, "but it turned out to be on the fast track," he told Live Science. [Photo Gallery: Antarctica’s Pine Island Glacier Cracks]
At 300 square kilometers (300 square kilometers), the enormous amount of ice that was sapping from the ice shelf of the glacier is even greater than the mass that broke off last year, Lhermitte said. Anyway, the newborn iceberg did not stay in one piece for long. Within a day, it was shattered into smaller pieces, with the largest piece measuring a respectable 87 square miles (226 square kilometers) before later breaking apart, Lhermitte said.
The largest iceberg was big enough to get a name, but it's not clear yet if this will happen as it has existed for such a short time. But, if it gets a nickname, it'll probably be called by the US National Ice Center B-46, Lhermitte said.
Lhermitte first noticed the rift that led to this giant calving event as he watched an October 3 image. Lhermitte said he gets a satellite image of the Pine Island Glacier in his inbox every day, "and suddenly I saw something I had not seen the previous day," he told Live Science.
But, after Lhermitte went back and looked at pictures of Sentinel-1, a satellite operated by the European Space Agency (ESA), he found that the crack actually appeared in the last week of September between the 25th and 30th of September. Lhermitte made a GIF that shows how fast the iceberg breaks off the ice shelf.
Even more dramatic is a time lapse from 1972 to 2018 showing how the ice shelf has retreated over the ice floe years. It is normal for ice sheets to grow and shrink over time, as this time lapse shows. But in 2015, the ice sheet slipped dramatically and retreated to the present day without showing any growth, Lhermitte said.
For years, the ice sheet hit a shallow point on the sea floor, the so-called pinning point. which might have prevented Lermitte from developing too far back, Lhermitte said. "After 2015, it lost the connection to this fixture, which could explain the retreat in 2015 and 2017," said Lhermitte. "And now this [ice shelf break] is about 5 kilometers [3.1 miles] further inland."
In addition, the Pine Island Glacier icebergs seem to calve more often than before. At the beginning of 2000, icebergs were salvaged about every six years, and calving events occurred in 2001, 2007 and 2013. There have been four since 2013: 2013, 2015, 2017 and 2018, Lhermitte said.
"The retreat that we see now is beyond what we observed [in modern times]," Lhermitte said. And that's worrying because ice shelves are important structural elements for glaciers; They slow the flow of ice into the ocean much as mud in a clogged outflow obstructs the flow of water.
Comparison of the calving front of the Pine Island Glacier 2018 with historical data from 1973-2011 of @JoeMacGregor shows how heavily PIG has withdrawn from the 1973-2013 series. pic.twitter.com/ifxmk85hMo
– Stef Lhermitte (@StefLhermitte) October 30, 2018
It is unclear why Pine Island glaciers iceberg more often than before. Warm, deep ocean water melts the ice shelf from below. "It depends on the climate, but this warm water that arrives there is also influenced by how the wind patterns change," said Lhermitte. "It's very difficult to say that this is climate change because we're still finding out how it all works."
Originally published on Live Science.