Ice shelves of Antarctica’s Pine Island Glacier may go earlier than expected

The melting of the glacier could result in a 0.5 metre global sea-level rise
Ice shelves of Antarctica’s Pine Island Glacier may go earlier than expected

The ice shelves of Pine Island Glacier are breaking apart rapidly and may collapse faster than previously projected, according to a study by Washington University and British Antarctic Survey. 

Pine Island Glacier is one of the largest ice streams in Antarctica. It contains approximately 180 trillion tonnes of ice, melting of which could result in 0.5 meters or 1.6 feet of global sea level rise.

It is Antarctica’s largest contributor to sea-level rise, causing about one-sixth of a millimeter increase to the sea-level each year or about two-thirds of an inch per century. Several studies have shown that past speedups were due to melt-driven thinning, concentrated near the grounding line.

In this study, researchers analysed satellite images from January 2015 to March 2020. For most of the first two years, the satellites took high-resolution images every 12 days. The researchers found that recent changes in the ice shelf were not caused by processes directly related to ocean melting.

From 2017 to 2020, a large iceberg on the edge of the ice shelf collapsed and glaciers accelerated, the study revealed. The ice shelf lost about one-fifth of its area in this period, as captured by the Copernicus Sentinel-1 satellites, operated by the European Space Agency on behalf of the European Union. The glacier's surface also sped up by 12 per cent in this time.

The authors used an ice flow model to confirm that the loss of the ice shelf caused the observed speedup. High-resolution videos of glaciers stitched together from satellite data showed the sides of the ice shelf were gridded with respect to the coastline. But a large crack in the centre of the ice shelf caused a sudden snap.

Ian Joughin, glaciologist at the UW Applied Physics Laboratory and lead author of the paper, said:

The recent changes in speed are not due to melt-driven thinning; instead they're due to the loss of the outer part of the ice shelf. The glacier's speedup is not catastrophic at this point. But if the rest of that ice shelf breaks up and goes away then this glacier could speed up quite a lot.

Pine Island Glacier has a large ice shelf, which supports the glacier. Recent speedups due to edge weakening may shorten the timeline for the Pine Island Glacier to finally collapse into the ocean.

The study was published in the open access journal Science Advances on June 11.

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