8km of ice vanished from Antarctic glacier in 2.5 years puzzling scientists

A large glacier in West Antarctica lost 8 kilometres of ice in just two-and-a-half-years, British scientists have found, suggesting a “glaciological tipping point” had been crossed.

It suggests relatively stable glaciers can quickly deteriorate when exposed to environmental changes, like warming oceans.

The Cadman Glacier covers an area of about 39km² and is located on the Antarctic Peninsula – the continent’s protruding ‘arm’ – south of Chile.

Along with other glaciers in this region, it acts as a conduit that drains – at a literally glacial pace – ice from the nearby icesheet into the Southern Ocean.

Imagery from the European Union’s Copernicus satellite shows a substantial loss of ice from the Cadman Glacier in recent years, following the collapse of an iceshelf at the glacier’s end. Ice shelves support glaciers by anchoring these icy masses to the seafloor. Exposure to warmer waters following the shelf collapse likely caused the rapid acceleration of icebergs calving from the glacier.

Given it extends towards the equator, the Antarctic Peninsula encounters the warmest conditions of any part of the southernmost continent. While rapidly warming ocean waters may have accelerated the process in recent years, the study, published today in Nature, came from data from three decades and nine satellites to analyse regional shifts.

The use of this historic information suggests the process may have been underway as far back as the 1970s, with warm bottom water effectively melting the iceshelf from its foundations.

Cadman was previously considered stable, so its record ice loss has scientists worried that warming oceans can quickly destabilise protective ice and lead to glacier decline. What’s less clear is why other structures,  like the nearby Funk and Lever glaciers, underwent this transformation.

“Cadman went from being an apparently stable glacier to one where we see sudden deterioration and significant ice loss,” says Benjamin Wallis, a glaciologist doctoral researcher at the University of Leeds, UK, who led the study.

“What was also curious was that the neighbouring glaciers on this part of the west Antarctic Peninsula did not react in the same way, which may hold important lessons for the way we can better project how climate change will continue to affect this important and sensitive polar region.  

“Our study brought together data from three decades, nine different satellite missions, and in-situ oceanographic measurements to understand the changes happening in Antarctica. This demonstrates how important it is to have long term monitoring of the Earth’s polar regions with a range of sensors which all tell us a different piece of the story.” 

The need to closely monitor the changing face of the Antarctic coast has the study’s authors calling for better observations, among them Professor Michael Meredith, an oceanographer at the British Antarctic Survey.

“This emphasises the need for a comprehensive ocean observing network around Antarctica, especially in regions close to glaciers that are especially hard to make measurements,” Meredith says.