The ice that lies on top of the earth’s deepest canyon stands on shaky ground.
A detailed survey of Denman Glacier in East Antarctica – the most accurate to date – has revealed an uncertain foundation, the shape of which can leave the heart of this glacier incredibly vulnerable to climate change.
In almost three decades, Denman Glacier has already retreated about five kilometers (nearly three miles) and lost over 250 billion tons of ice. In the worst case, the damage can be much greater.
Unlike other glaciers in Antarctica, Denman is particularly thick – sitting on a canyon of 3,500 meters below sea level. In addition, it slopes in the opposite direction, facing away from the sea instead of towards it, and it can make all the difference.
It may sound intuitive. Wouldn̵
If the point where the glacier floats on the sea – known as the land line – continues to retreat all the way back to the Aurora Subglacial Basin, about 160 kilometers or 100 miles inland, the situation may grow out of control.
As the line moves further back, researchers say it will inevitably face thicker and thicker ice, which means that ever-increasing amounts of meltwater flow into the ocean.
“Because of the shape of the ground below Denman’s west side, there is the potential for rapid and irreversible retreat,” says NASA geoscientist Virginia Brancato, “and that means significant increases in the global sea level in the future.”
If the entire glacier collapses, the authors predict that it may cause a 1.5 meter rise in sea level, and there is no small amount in the big thing.
While Western Antarctica is generally considered to be the most vulnerable to melting, these results support the idea that eastern Antarctica may be more vulnerable than we once thought.
“The ice in West Antarctica has melted faster in recent years, but the large size of the Denman Glacier means its potential impact on long-term sea level rise is equally significant,” says Earth system scientist Eric Rignot at the University of California Irvine.
Using satellite data from the Italian Space Agency between 1996 and 2018, the study reveals a clear asymmetry in Denman Glacier’s baseline.
Compared to the eastern side of the glacier, which is narrower, the western flank looks much more vulnerable and shows a steep trough-like appearance that can spell trouble for rapid melting.
With a strong sea that continues to spin at the edge of the ice, the slope can act as a kind of slide and take the sea and the melted ice further and further inland – a jumping effect that is not often taken into account in today’s ice sheet models.
“This study provides further evidence that, based on current knowledge, we cannot rule out at least a small opportunity for much more sea level rise than the most likely value in [Intergovernmental Panel on Climate Change] forecasts, “said Richard Alley, a glaciologist at Pennsylvania State University who did not work with the study The Washington Post.
At the end of last year, research revealed for the first time that Denman Glacier covered the world’s deepest land canyon – almost as deep as the average ocean depth and eight times deeper than the Dead Sea beaches.
That’s how much ice we can drop, and we just realized.
The study was published in Geophysical research letters.