A vast area of the Antarctic Ice Sheet – Thwaites Glacier – continues to retreat and much of it could be lost by the 23rd century, experts say.
The glacier spans an area equal to the island of Great Britain or the US state of Florida, and in some places is more than 2,000 metres thick.
The volume of ice flowing into the sea from Thwaites Glacier and its neighbouring glaciers has more than doubled from the 1990s to the 2010s.
Experts say the glacier and the wider region, called the Amundsen Sea Embayment, account for 8% of the current rate of global sea level rise of 4.6mm a year.
The glacier is one of the largest and fastest-changing in the world, and if it collapsed entirely, sea levels would rise by 65cm.
Latest computer models predict that ice loss will accelerate through the 22nd century and could lead to a widespread collapse of the West Antarctic Ice Sheet in the 23rd.
Experts say immediate and sustained climate intervention is needed to make a positive difference.
Since 2018, researchers have uncovered a complex, rapidly changing environment at the remote glacier, and scientists from the UK and US are meeting at British Antarctic Survey (BAS) in Cambridge this week to discuss their observations.
Before the start of the project, named the International Thwaites Glacier Collaboration (ITGC), little was known about the mechanisms controlling the retreat of the huge glacier.
Dr Rob Larter, from the Science Co-ordination of the ITGC and a marine geophysicist at BAS, said: “Thwaites has been retreating for more than 80 years, accelerating considerably over the past 30 years, and our findings indicate it is set to retreat further and faster.
“There is a consensus that Thwaites Glacier retreat will accelerate sometime within the next century.
“However, there is also concern that additional processes revealed by recent studies, which are not yet well enough studied to be incorporated into large-scale models, could cause retreat to accelerate sooner.”
The latest findings suggest Thwaites Glacier and much of the West Antarctic Ice Sheet could be lost by the 23rd century.
Its ice rests on a bed far below sea level that slopes downwards towards the heart of West Antarctica, making Thwaites Glacier particularly vulnerable.
Researchers have used underwater robots, new survey techniques, and new approaches to ice flow and fracture modelling, to gain new insights into these processes.
They say that although this has improved the ability of computer models to predict what might happen, there is still a lot that is not known about the glacier’s future.
At roughly 120km across, Thwaites is the widest glacier on the planet and is a keystone of the West Antarctic Ice Sheet, much of which sits on a bed below sea level and would raise sea levels by 3.3 metres if it all melted.
Dr Ted Scambos, US science co-ordinator of the ITGC and glaciologist at the University of Colorado, said: “It’s concerning that the latest computer models predict continuing ice loss that will accelerate through the 22nd century and could lead to a widespread collapse of the West Antarctic Ice Sheet in the 23rd.”
He continued: “Immediate and sustained climate intervention will have a positive effect, but a delayed one, particularly in moderating the delivery of warm deep ocean water that is the main driver of retreat.”
So far, results from the studies indicate that the rate of ice loss from the retreating glacier will increase in response to climate and ocean changes.
Among several potential scenarios for ice loss, some of the most rapid and concerning potential processes are now found to be less likely than once feared.
But ITGC studies have also revealed previously unknown processes that could weaken the glacier and change current projections.
The researchers also say that the Thwaites Eastern Ice Shelf (TEIS), currently covering about half of the 120km-wide front of the glacier, is likely to disintegrate in the coming decade.
But data from the research indicates that Thwaites Glacier has recovered from past retreat.
Rock samples taken by drilling through the ice near the glacier edge show that the glacier was thinner, and the rocks were at the surface, a few thousand years ago.
The glacier later thickened to cover them, indicating that re-advance and recovery of the glacier is possible.
This raises the future research question of whether there are any mechanisms that might arrest or suspend retreat, and if so, what climate conditions would they need.
Other issues researchers were considering included how they could improve computer models, and how conditions in the area evolved in the coming years.
