Undersea anchors of ice that help prevent Antarctica’s land ice from slipping into the ocean are shrinking at more than twice the rate compared with 50 years ago, research shows.

Experts from the University of Edinburgh reveal that over a third of these frozen anchors, known as pinning points, have diminished since the early 2000s.

The decline in pinning points, responsible for securing the floating ice sheets that support Antarctica's land ice, could expedite the continent's contribution to rising sea levels, caution scientists. This discovery stems from a novel study tracking changes in Antarctic ice shelf thickness dating back to 1973, utilising satellite imagery from the NASA/United States Geological Survey Landsat programme.

Pinning points materialise when sections of a floating ice sheet fasten to elevated points on the ocean floor, creating discernible protrusions on the otherwise smooth ice shelf surface. By observing alterations in these features, researchers gauged fluctuations in ice shelf thickness across three intervals: 1973 to 1989, 1990 to 2000 and 2000 to 2022.

Analysis revealed that while only 15% of pinning points diminished in size from 1973 to 1989, leading to localised thinning of ice shelves, a widespread trend of accelerated ice shelf unanchoring started in the 1990s. This trend intensified in the western Antarctic Peninsula and the Amundsen Sea, with the proportion of shrinking pinning points rising to 25% from 1990 to 2000, and 37% from 2000 to 2022.

Published in Nature, the study underscores the remarkable shift over five decades from limited and localized ice shelf melt to widespread unanchoring.

“The switch over the past 50 years from relatively limited and regionally concentrated ice shelf melt, to much more widespread unanchoring, is striking. The ongoing concern is how many more of these vitally important pinning points will begin to melt away in the coming 50 years,” said Dr Bertie Miles, lead author.

“What we are seeing around Antarctica is a sustained attack by climate warming to the buttresses, that slow the conversion of ice melting, into global sea-level rise. This reinforces the need for us to take action where we can to reduce global carbon emissions,” added Professor Robert Bingham, also a lead author.