Another Antarctic warning shot: the “Doomsday Glacier” is losing its last shield

Antarctica’s Thwaites Glacier is almost the size of Victoria, and more than two kilometres thick in places. It holds enough land-based ice to raise global sea levels by around 65 centimetres when fully melted. Now scientists believe its remaining eastern ice shelf - the floating extension that protects the glacier’s front - could break apart as early as this year.

“The last bit of ice shelf in front of the glacier is poised to disintegrate,” British Antarctic Survey scientist Robert Larter ⁠told Live Science.

This doesn’t mean the entire glacier will collapse this year, but it’s still a very serious warning. The glacier’s ice shelf is already floating, so its breakup will add little water directly to the ocean. The danger is what comes afterwards. Because an ice shelf acts like a brace for the glacier, restraining the immense mass of land-based ice behind it. As it weakens and disappears, the glacier behind it can flow more rapidly into the sea.

Satellite observations show large cracks have been spreading across the Thwaites Eastern Ice Shelf since 2016. Full-depth rifts have appeared. And the shelf is increasingly losing contact with the seabed ridge that has been holding it in place - a ⁠peer-reviewed study from Cambridge University described this as the shelf’s “last act”.

The deeper danger

Thwaites is especially vulnerable because much of it sits on bedrock below sea level.

Warm, salty ocean water is reaching underneath the glacier and melting it from below. Tides are already pumping seawater as far as 10 kilometres beneath the grounded ice. And worse, much of the bedrock slopes downwards further inland. As the glacier retreats, thicker ice will be pushed to deeper water, encouraging still more melting and retreat. Scientists call this ‘marine ice-sheet instability’.

While the ⁠International Thwaites Glacier Collaboration concluded that complete disintegration of the glacier is unlikely during the next few decades, its retreat will definitely continue and accelerate. A 2026 modelling study found that Thwaites’ rate of ice loss has increased more than fivefold since the 1990s. By the 2060s, it could be losing around 180 to 200 billion tonnes of ice each year.

The eventual loss of Thwaites will also contribute to the destabilisation of surrounding West Antarctica, which contains enough ice to raise seas by approximately 3.3 metres. These changes will unfold over more than our lifetimes. But ice sheets have long memories. Tipping points crossed now will commit Earth to rising seas for centuries to come.

What does this mean for Australia?

Global sea levels have already risen by more than 22 centimetres since 1900. And the rate of rise has accelerated from about 1.5 centimetres per decade during the twentieth century to nearly four centimetres per decade since 1993, according to the ⁠BOM and CSIRO.

Higher seas give every king tide, storm surge, east coast low and tropical cyclone a higher launching pad. Coastal erosion accelerates. Salt enters wetlands and groundwater. Homes, roads, ports and sewage systems become more vulnerable. Properties don’t have to be permanently underwater to become uninsurable, unmortgageable or effectively unsellable.

Australia’s ⁠National Climate Risk Assessment assesses that sea-level rises will place an additional 1.5 million Australians in high-risk coastal areas by 2050.

The consequences for low-lying Pacific nations and Torres Strait Islanders are more existential. Rising seas already threaten freshwater, food production, homes, cultural sites and the habitability of entire islands. First Nations coastal Country and irreplaceable cultural heritage will also be inundated and eroded.

The bad news is that breakup of the Thwaites ice shelf is inevitable. But that doesn’t mean the fate of the entire glacier is fixed. Every fraction of a degree of avoided warming matters. Every centimetre of avoided sea-level rise matters. Every additional decade available for communities to prepare matters.

Thwaites is showing us what a climate tipping process looks like: it’s not like a spectacular Hollywood disaster, it’s the progressive loss of structures that hold a vast natural system together. And Australia can’t credibly acknowledge the danger while continuing to approve new coal and gas projects that will operate for decades.

Photo of the Thwaites Glacier from Live Science.