A glacier in Antarctica is breaking from the inside out – proof that the ocean ice is weakening on the edges of the continent, Phys.org says.
The Pine Island Glacier, which is part of the ice shelf that covers the West Antarctic Ice Sheet, is one of the two glaciers that scientists think are most likely to melt, bringing more ice from the inside of the ice sheet to the ocean. This in turn would flood coastlines around the world.
In 2015, a massive iceberg measuring 225 square miles broke off from the glacier, but researchers from Ohio State University noticed something different in the satellite images before the incident.
While testing some new imaging software, the researchers saw that a rift had formed at the base of the ice shelf some 20 miles inland in 2013. This rift then cracked more in two years, until it broke through the surface and cut the iceberg loose.
Ian Howat, lead researcher and associate professor of earth sciences, says, “”It’s generally accepted that it’s no longer a question of whether the West Antarctic Ice Sheet will melt, it’s a question of when.” He explains,
This kind of rifting behavior provides another mechanism for rapid retreat of these glaciers, adding to the probability that we may see significant collapse of West Antarctica in our lifetimes.
This is the first time researchers have seen a deep subsurface rift coming up in Antarctic ice, but similar events have happened in the Greenland Ice Sheet. In this case, ocean water seeped inland on the bedrock and melted the ice from underneath. “Rifts usually form at the margins of an ice shelf, where the ice is thin and subject to shearing that rips it apart,” he says. “However, this latest event in the Pine Island Glacier was due to a rift that originated from the center of the ice shelf and propagated out to the margins. This implies that something weakened the center of the ice shelf, with the most likely explanation being a crevasse melted out at the bedrock level by a warming ocean.”
Howat said the satellite images offer the first strong evidence that the Antarctic ice shelves are responding to climate change in the same manner as Greenland ice.
The rift also opened in the bottom of a valley on the ice shelf, where the ice had thinned. This is further proof that the ice is melting in unseen portions of Antarctica.
Over half of the world’s fresh water is frozen in the continent. The Pine Island Glacier and the Thwaites Glacier sit on the outer edge of one of the Antarctic’s most active streams, keeping the ice flow at a pace that doesn’t drain and flood the seas.
Studies have said that the West Antarctic Ice Sheet is unstable, and could collapse in the next 100 years. This would lead to a rise in sea level water up to 10 feet, which would engulf major coastal cities such as New York and Miami.
“We need to understand exactly how these valleys and rifts form, and what they mean for ice shelf stability,” Howat says.
The study was published in Geophysical Research Letters.
