Massive Thwaites Glacier ‘could be gone by 23rd century’, warns British Antarctic Survey

Thwaites Glacier and much of the West Antarctic Ice Sheet could be lost by the 23rd century, according to findings from British Antarctic Survey (BAS) researchers and their colleagues.

The glacier spans an area equal to the size of Great Britain and in places is more than 2,000m (6,500ft) thick, making it one of the largest in the world. Its total collapse would cause sea levels to rise by 65cm.

The team of UK and UK researchers, who met at the BAS in Madingley last week, say Thwaites Glacier is due to retreat further and faster than it has been doing.

They have uncovered a complex and rapidly changing environment at the remote glacier in West Antarctica since 2018.

Little was known about the mechanisms controlling the retreat of the enormous glacier before the launch of their project, named the International Thwaites Glacier Collaboration (ITGC).

But the volume of ice flowing into the sea from Thwaites and its neighbouring glaciers more than doubled between the 1990s and the 2010s. The wider region – the Amundsen Sea Embayment – accounts for 8 per cent of the current rate of global sea level rise of 4.6mm a year.

ITGC was set up to understand the critical physical processes controlling the glacier in the present climate and over the last few thousand years and to build a more reliable prediction of how and why it will change in the future.

“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,” according to Dr Rob Larter, from the science co-ordination of the ITGC, and a marine geophysicist at BAS.

“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 project team want to predict the rate and magnitude of sea level rises, which will have a huge impact on hundreds of millions of people on coasts from Bangladesh to low-lying Pacific islands, and from New York to London.

They suggest Thwaites Glacier – the widest on the planet at about 120km across –and much of the West Antarctic Ice Sheet could be lost by the 23rd century.

Thwaites is exceptionally vulnerable because its ice rests on a bed far below sea level, which slopes downwards towards the heart of West Antarctica.

The team used advanced technology – including underwater robots, along with novel survey techniques and new approaches to ice flow and fracture modelling – to gain insights into the processes, improving predictive computer models, although they say much remains to be understood about the glacier’s future.

Thwaites is a keystone of the West Antarctic Ice Sheet, much of which sits on a bed below sea level. If the whole ice sheet melted, sea levels would rise by 3.3 metres.

“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,” said Dr Ted Scambos, US science coordinator of the ITGC and glaciologist at the University of Colorado.

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.”

Warmer water in the Amundsen Sea is thawing the underside of the ice in Thwaites Glacier, particularly in the region of the grounding zone, where the ice is lifted and lowered off the seabed by tides.

Under a worst-case scenario, the team says fast-collapsing ice cliffs of 100 metres height or more could form at the front of the Thwaites and rapid, repeated calving of icebergs from them would lead to runaway retreat.

The ITGC also detected worrying and previously unknown processes in which tides could weaken the ice. In areas where Thwaites rests on the seabed, warmer water seeps underneath as the tide rises. When the tide falls, the water is pumped at high pressure up to 10km under the ice and it is thought this rising and falling may accelerate melting at the base of the glacier, allowing it to slide faster into the sea.

Using a torpedo-shaped robot known as Icefin, lowered through a 600m deep hole drilled through the ice shelf with hot water, the researchers found a thin layer of cold water insulates much of the flat-lying underside of the ice, which is slowing the thaw. But stronger melting was found in other areas where the ice base is tilted more steeply and at cracks in the bottom of the ice.

Meanwhile, maps of ridges and channels on the seabed have been developed, which help us understand how natural ‘pinning points’ can slow the flow of Antarctica’s glaciers.

Global sea levels are predicted to rise between 40cm and 80cm this century, according to the Intergovernmental Panel on Climate Change, depending on future greenhouse gas emissions, driven by melting and ice flow in Greenland, Antarctica and the world’s mountain glaciers, and the natural expansion of ocean water as it warms.

In a worst-case scenario, said to be of ‘low likelihood’, the IPCC has estimated that sea levels could rise by up to almost two metres by 2100.