Thwaites Glacier Melting Faster Than Forecast, Raising Sea-Level Risk
Al Jazeera Staff
A new study in Nature Communications finds that Antarctica's Thwaites Glacier is losing mass faster than predicted as warm seawater intrudes beneath the ice. In the worst case, the glacier could raise global sea levels by about 30mm by 2100 — twice earlier estimates.
Research published this week in Nature Communications shows that the Thwaites Glacier in West Antarctica is losing mass rapidly as warm seawater seeps beneath it and melts its core. According to the findings, even if global warming does not accelerate further as forecast, the glacier could still push sea levels up by about 1.2 inches (30mm) by 2100 — double current estimates.
The team was made up of glaciologists at the University of California in the United States working with NASA's Jet Propulsion Laboratory (JPL). The findings add to growing evidence that the glacier, which has been retreating for decades, is losing mass faster than scientists had thought.
What is Thwaites and why does it matter?
Nicknamed the "Doomsday Glacier," Thwaites is the largest glacier on Earth, covering roughly 192,000 square kilometers — about the size of Senegal and larger than the US state of Florida. It lies on the Walgreen Coast in the Marie Byrd Land region of far West Antarctica and forms part of the West Antarctic Ice Sheet, which is 14 times the size of Thwaites itself.
Thwaites was first mapped in 1947 and is named after the late American glaciologist Fredrik T. Thwaites, although he never set foot there. Since the 1980s, scientists have found that the glacier is melting quickly and have monitored it closely amid mounting concern.
Given its vast size, a collapse of Thwaites would drive a catastrophic rise in global sea levels — though researchers say such a scenario is still decades, perhaps centuries, away. Along with glaciers such as Pine Island, Thwaites forms a barrier that holds back the vast and fragile West Antarctic Ice Sheet; if that sheet melts, it could submerge many coastal cities around the world.
Ice lost from Thwaites currently accounts for about 4% of global sea-level rise. Studies calculate that the glacier has lost more than 1 trillion tons of ice since 2000 and continues to lose 50 billion tons a year.
Why it is melting
According to numerous studies, the main driver is warm seawater actively melting Thwaites from below. Ocean warming is caused by human-driven climate change, in particular the burning of fossil fuels.
In 2019, NASA's Jet Propulsion Laboratory discovered a huge undersea cavity beneath Thwaites Glacier, covering an area two-thirds the size of Manhattan, which researchers believe may be speeding up the glacier's thinning. According to the European Space Agency, rising temperatures have cost glaciers about 5% of their ice mass since 2000.
What the new study found
The research shows Thwaites could raise sea levels by as much as 1.2 inches (30mm) by 2100, double the current estimate, even without any additional global warming.
The team used new computer models that give a sharper picture of melting beneath the threatened glacier at the grounding line — the boundary where the glacier shifts from resting entirely on bedrock to spreading out over the sea as an ice shelf.
Whereas other ice-sheet models treat the grounding line as fixed, the scientists developed the broader concept of a "grounding zone." In this scenario, seawater lifts and lowers the ice mass through a "tidal pumping" process, allowing warm water to reach "deep beneath the ice shelf and cause strong melting," lead author Mattia Poinelli, a project scientist at UCLA, told reporters.
This melting is accelerating Thwaites' detachment from the Mouginot Ridge, an important undersea bedrock structure that currently stabilizes the glacier from below. The study concludes there is a 60% chance that Thwaites will detach from the ridge by the end of the century.
However, experts say more research is needed to forecast accurately how much ice Thwaites will lose.
In a separate study, scientists at the British Antarctic Survey concluded that Thwaites will keep losing ice for at least the next 150 years, even under the most extreme ocean cooling imaginable. That research, which used computer simulations of the ocean's melting impact over the next century and a half, was published in the journal Geophysical Research Letters in July.
