Shrinking Antarctic ice shelf Pine Island Glacier sheds giant iceberg
In one of the fastest-changing areas of the Antarctic ice sheet, satellites have captured the formation of a giant, 300-square-kilometre iceberg.
Researchers monitoring satellite imagery of the Pine Island Glacier (PIG), in west Antarctica, first noticed two large rifts forming in the shelf in 2019.
Over the next few months, as the glacier moved out towards the Amundsen Sea, the rifts expanded, eventually leading to the splitting of the iceberg from the glacier on February 9.
Within a day, the iceberg had broken up into smaller pieces.
Only one of the pieces was large enough to be named (B-49) and tracked by the United States National Ice Centre.
It comes just days after a station on the Antarctic Peninsula logged its hottest day on record, registering a temperature of 18.3 degrees Celsius.
The peninsula, which juts out to the north-west of the Pine Island Glacier, is among the fastest-warming regions on the planet. Temperatures there have increased almost 3C over the last 50 years, according to the World Meteorological Organisation.
Last month, scientists also recorded unusually warm water beneath the Thwaites Glacier, a neighbour to Pine Island.
While the calving of icebergs from shelves such as the Pine Island Glacier is a natural process in the life of a giant glacier, the rate at which this glacier and others in the region have been disintegrating is a cause of concern for scientists.
Previously the ice shelf calved once a decade. By the early 2000s, it started calving once every five years. But since 2013, the glacier has calved five times, according to Stef Lhermitte, a remote sensing scientist from the Delft University of Technology in the Netherlands.
“The sequence of calving events over the last years shows that they have become more frequent, that the icebergs disintegrate more quickly and that the Pine Island ice shelf is reaching its smallest extent in recent observational history,” he said.
Satellite data has shown that the glacier’s flow out towards the sea is speeding up to a rate of more than 10 metres a day, it is thinning out and is retreating inland.
“This indicates that Pine Island ice shelf is weakening as a result of warm ocean water and this is important as the ice in the Amundsen Sea Embayment, where PIG is located, is the area where we scientists are most worried about contributions to sea-level rise,” Dr Lhermitte said.
The largest mass loss from the icy continent comes from this region in west Antarctica. According to the World Meteorological Organisation, almost 90 per cent of glaciers along the west coast of the Antarctic Peninsula have retreated in the last 50 years with most of these showing an accelerated retreat in the last 12 years.
It is estimated the region has enough vulnerable ice to raise sea levels by 1.2 metres.
A year of satellite imagery shows the formation of an iceberg from the Pine Island Glacier.
“It’s one of the fastest changing areas on the Antarctic ice sheet,” said Ben Galton-Fenzi, a senior scientist with the Australian Antarctic Division.
“It is incredibly worrying.
“The problem is that when you start to change the area of the ice sheet that’s in contact with the ocean by a little bit then you get this runaway effect, it’s called marine ice sheet instability.
“Once that effect starts to go it causes more ice to flow from the continent into the ocean, so they speed up even faster and that feedback process keeps happening.”
The biggest iceberg on record was 11,000 square kilometres. It calved off the Ross Ice Shelf in 2000.