Scientists have been watching the Thwaites Glacier with growing dread for years. Thwaites is the largest glacier in West Antarctica, and is roughly the size of Florida.
It’s more than 6,560 feet (2,000 meters) thick in places and 75 miles (120 kilometers) wide.
The glacier’s full collapse would raise global sea levels by around 26 inches (65 centimeters), flooding coastal communities on every inhabited continent. That collapse would take centuries.
But a new warning suggests one of the main things slowing it down is about to disappear.
An ice shelf poised to disintegrate
The Thwaites eastern ice shelf – a floating body of ice attached to the glacier’s front that acts as a natural brake on the flow of ice toward the sea – could begin breaking apart as early as 2026.
Robert Larter is a marine geophysicist at the British Antarctic Survey who coordinates the UK side of the International Thwaites Glacier Collaboration, the joint US-UK research effort studying the glacier.
“The last bit of ice shelf in front of the glacier is poised to disintegrate,” said Larter. “We don’t know quite how this ice shelf is going to break up, but it’s definitely going to go,” said Larter.
Cracks are spreading
The nickname “Doomsday Glacier” sounds like an exaggeration, but it isn’t. Thwaites isn’t just a very large glacier – it’s a structural pillar holding back much of the West Antarctic Ice Sheet.
If Thwaites goes, it destabilizes the ice behind it. If the whole West Antarctic Ice Sheet eventually follows, sea levels rise by around 11 feet (3.3 meters).
That’s not a distant theoretical scenario for modellers to argue about.
A climate tipping point
Scientists consider the eventual collapse of Thwaites Glacier and the ice behind it a genuine long-term possibility.
They treat the glacier’s trajectory as a climate tipping point – a threshold that triggers irreversible changes lasting thousands of years once crossed.
Thwaites has been losing ice at an accelerating pace since the 1980s, shedding hundreds of billions of tons and retreating around 12 miles (20 kilometers) since 1992.
The mechanism is brutal. Warm, salty ocean water pushes up from the deep ocean and attacks the glacier at its weakest point, melting the ice from below where it meets the bedrock.
This configuration makes the melting hard to stop once it gets going.
The doorstop is breaking
The eastern ice shelf sits at the glacier’s mouth, held in place partly by an underwater ridge on the ocean floor.
Its job is to act as a doorstop wedged against the outward flow of ice and slowing how quickly Thwaites reaches the sea.
Satellite images show the shelf fracturing at the points where it’s anchored, and Larter said that movement on the western side of the shelf has roughly doubled over the past eight months.
The fracturing is happening where the shelf meets the ridge and at the glacier’s front – the two places where it’s most constrained. When those constraints go, the ice behind them moves faster.
Once the shelf breaks apart, it can no longer slow the glacier’s flow into the ocean. No other ice formation is in place to replace that restraining function.
What is the cause?
Larter is careful about how he describes the cause. It’s not simply that the ocean is warmer – it’s that changes in how the ocean circulates are pushing warm water where it wasn’t reaching before.
The westerly winds circling Antarctica have been shifting, altering ocean circulation in ways that drive warm deep water up onto the continental shelf and under the ice.
“There is an active scientific debate about exactly how this works, but it seems pretty clear that in some way, the changes to the Southern Hemisphere westerly winds are what is driving warm water onto the continent,” Larter said.
“And those wind changes are part of the wider pattern of climate change that we’re seeing.”
A glacier without brakes
No one is saying Thwaites is about to collapse next year. A glacier this large takes centuries to fully disintegrate. Scientists still struggle to model exactly how that process will unfold.
One recent study projected the glacier could be losing between 180 and 200 billion tons of ice per year by 2067. That rate of ice loss would raise sea levels long before the glacier disappears.
What the imminent loss of the eastern ice shelf means is that one of the main things slowing that process down is about to be removed.
The path to collapse
The glacier has been retreating with a brake on. Soon it won’t have one.
“We don’t know quite how this ice shelf is going to break up, but it’s definitely going to go,” Larter said.
The doomsday scenario includes a full glacier collapse, about 26 inches (65 centimeters) of sea level rise, and widespread coastal flooding. Scientists expect that process to unfold over centuries rather than years.
But the direction of travel has been clear for years, and losing the eastern ice shelf is another step in that direction. One that’s now, apparently, just months away.
The study can be found here.
—–
Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates.
Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.
—–