Hotspots are beginning to form along the coast of East Antarctica.
The ice shelf, which collapsed for no reason a few years ago, has been steadily weakening for 30 years, with scientists barely noticing. The researchers reported on Dec. 3. natural earth science. The discovery, based on decades of satellite observations, raises concerns about the Antarctic region, which was long thought to be stable.
“The East Antarctic ice sheet has 10 times more ice than West Antarctica,” said Matthieu Morigem, a glaciologist at Dartmouth College who was not involved in the study. West Antarctica is already hemorrhaging ice at an alarming rate (SN: 2/15/23). But if the East Antarctic ice sheet also retreats, the rate of sea level rise could dramatically increase over the next few centuries.
A recent reminder of this concern is East Antarctica’s Conger Ice Shelf, a former slab of floating glacier ice about 20 times the size of Manhattan. In 2022, it suddenly broke into an iceberg and drifted apart over several days.
“No one thought it would go away,” says Katherine Walker, a glaciologist at Woods Hole Oceanographic Institution in Massachusetts who led the new study. “It didn’t melt that quickly either.”
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Satellite images taken 11 weeks later, on March 23, 2022, show the ice shelf rapidly disintegrating just weeks earlier. Lauren Dauphin, NASA Earth Observatory
Before its collapse, the Conger Ice Shelf likely existed for thousands of years. It was formed by several adjacent glaciers that oozed from the coastline and floated into the sea. Walker discovered the 2022 collapse by chance.
While studying satellite imagery to determine another nearby ice shelf, she noticed that the 1,200 square kilometer Conger Ice Shelf was present in a photo taken on March 10 that year. , I noticed it was missing in another photo taken 6 days later.
So began a two-year effort to understand what had been destroyed.
Polar meteorologist Jonathan Will, along with Walker and 50 other scientists, reported an important clue earlier this year: a powerful storm. During that time we passed along the coasttilting the sea level up or down by a fraction of a degree. As the ice shelf bent, it broke along pre-existing cracks. Powerful winds then pried the debris apart.
“We have good reason to think so.” [these storms] “As the Earth warms, this phenomenon will become even more intense in the future,” says Wille, of the ETH Institute for Atmospheric and Climate Sciences in Zurich, Switzerland. These more powerful storms can damage the protective ice shelves that line Antarctica’s coastline (SN: September 25, 2019).
But in the case of the Conger Ice Shelf, the story is more complicated. New research shows that conditions were already dire when the storm hit.
The collapse of several famous ice shelves was preceded by massive melting of the top surface at warm temperatures. However, because conger eels were generally in areas where the air was cold, the melting of their undersides was caused by seawater. Walker and his colleagues looked at archival satellite measurements and found that the floating shelf gradually thinned, going from about 200 meters thick in 1994 to 130 meters in 2021. Satellite radar measurements suggest that cracks have penetrated the thin, fragile ice, allowing salty seawater to seep in. Penetrates and weakens it further.
The conger ice shelf remained stable for a long time because it was pressed against an island 50 kilometers from the coast. But as the ice shelf thinned, it became too weak to withstand its compressive forces. Walker said the island has become “a slow-motion rock coming through the windshield.” Spider web-like cracks form at the point of contact between the ice shelf and the island, a new study reports. Then, on March 7, 2022, they fled the island and lost support in the face of an oncoming storm.
The glaciers stabilized by conger eels are small, so their collapse has no noticeable effect on sea levels. But the fact that it happened in this supposedly stable region of Antarctica “worries me,” Morigem said.
The region’s coastal waters have historically been very cold, but small changes began around 2010. Ocean currents have changed, making the water 0.6 degrees Celsius warmer than before. invade the coastlineresearchers reported last year. This may have hastened the end of the Conger Ice Shelf.
It could also eventually destabilize the giant glacier just 130 kilometers west of Conger. Denman Glacier stores enough ice to raise global sea levels by 1.5 meters if it all slid into the ocean. It alone contains almost half of the ice in West Antarctica. As Denman flows off the coastline, it slips between a floating ice shelf on one side and an island on the other, slowing its progress out to sea. But the ice that connects it to those stabilizing structures Gradually lose weight and become weaker. It may eventually be released and speeds may increase.
“This part of the East Antarctic ice sheet is very stable,” Morigem said. In some computer simulations, East Antarctica is It may also add some weight Over the next century. But if Denman and its surrounding areas become unstable, “the situation will change completely.”
