The world’s widest glacier is melting “more aggressively” than earlier projections said. According to new research by a team of glaciologists, its effect on global sea level rise could be twice the current estimates.
What the new study found
Thwaites Glacier in West Antarctica is known as the “Doomsday Glacier” because its collapse could cause serious damage, as per CNN. The glacier makes it difficult for scientists to predict future sea level rise.
According to CNN, glaciologists from the University of California, Irvine, and NASA’s Jet Propulsion Laboratory developed a new ice sheet model to better understand what is happening beneath the glacier.
After updating the model to include a “grounding zone,” the scientists found that Thwaites Glacier could add up to 1.2 inches to global sea levels by 2100. This is twice the amount predicted by earlier estimates, and it could happen even without further global warming. The findings were published Monday in the journal Nature Communications.
Why it is hard to predict
Florida-sized glacier lies in one of the least accessible places on Earth. It has been retreating for decades. Its melting ice now adds around 4% to global sea level rise. The reasons behind its retreat are very complex, which makes its future hard to map.
What is a ‘grounding zone’?
According to CNN, the glacier’s rapid retreat is driven by processes at its “grounding line.” This is the point where the ice rises off the seabed and starts to float on the ocean as an ice shelf.
A typical ice sheet models have treated the grounding line as fixed and mostly stable. But “we have come to acknowledge a different arrangement beneath Earth’s major ocean-terminating glaciers,” said the report’s lead author Mattia Poinelli. He is a project scientist at UCLA who was an Earth system science researcher at UC Irvine at the time of the study.
As per CNN, satellite data shows the grounding line is really a “grounding zone,” sometimes miles wide. Seawater flows in and out with the tides here, lifting and lowering the thick ice. This is called “tidal pumping.” According to Poinelli, this lets relatively warm ocean water get “deep underneath the ice sheets and causing vigorous melting.”
Underwater ridges may no longer hold back the glacier
According to CNN, the land beneath Thwaites Glacier slopes downward. As the glacier melts, more ice comes into contact with warm ocean water. Two underwater ridges currently help hold the ice back and stop it from flowing into the ocean too quickly.
The study found that melting is making the ice slowly detach from one of these ridges, called the Mouginot Ridge.
Scientists estimate there is a 60% chance that the ice will break free from the ridge by the end of the century.
If this happens, the glacier could retreat quickly down the sloping ground towards the next major ridge.
Why it matters
Thwaites holds enough water to raise sea levels by more than 2 feet if it collapses. It also acts like a cork holding back the huge Antarctic ice sheet. So its collapse could lead to around 10 feet of sea level rise, which could badly hurt coastal communities from Miami to Manila.
The findings suggest the impact of losing Thwaites may have been underestimated. It added that 1.2 inches may not sound like much, but it is enough to greatly increase dangers for coastal people.
The results “predict greater risk of and exposure for coastal flooding than anticipated in the coming decades,” said Eric Rignot, a report author and professor of Earth system science at UC Irvine, as per CNN.
What happens next
As per CNN, Rignot said the next step is to get observational data from the grounding line. The scientists plan to travel there in 2028 and set up instruments to record the flow of seawater in and out.
“We have been aware of the impacts of climate change on our planet’s sensitive ice sheets for decades,” Rignot said, “but a mounting realization gained in recent years of what is really happening on the undersides of glaciers like Thwaites is leading to an even greater sense of alarm.”
He said the world must cut planet-heating pollution now to limit the impacts. But he warned, “even if we do, we can expect higher sea levels in the future resulting from the damage that has already been done.”
