Researchers believe that the block of ice that stops the melting of the widest glacier in Antarctica will break off in a very short period of time. If the ice shelf breaks off, it will cause a significant rise in global sea level
With the surface of Great Britain, Thwaites, in Antarctica, has earned the nickname of the ‘ doomsday glacier ‘: its collapse could mean a drastic change in sea level and catastrophes and floods across the planet. That is why scientists have been observing their behavior for years, to predict their evolution. And the latest estimates do not provide encouraging data: a block of ice that is slowing down its melting and that acts as a kind of ‘barrier’, could break in just five years, causing new fractures in Thwaites that cause it to detach, causing a significant rise in global sea level.
This is the conclusion reached by the International Thwaites Glacier Collaboration (ITGC), a team of nearly 100 researchers funded by the US National Science Foundation.
and the Natural Environment Research Council of the United Kingdom after investigating the glacier and the adjacent ocean for five years. His work, which has been presented this week at a specialized meeting held in New Orleans (United States), has revealed important changes in the ice, the surrounding water, and the area where it rests on the land.
“Thwaites is the widest glacier in the world,” says Ted Scambos, Senior Research Scientist at the Cooperative Institute for Research in Environmental Sciences (CIRES) and head of the international consortium, in a statement. It has doubled its outflow velocity in the last 30 years, and the glacier as a whole contains enough water to raise sea levels by more than 50 centimeters. And it could lead to an even higher rise, up to more than three meters, if it drags down surrounding glaciers.” That is to say, Thwaites is a great threat in the short term.
Thwaites is located in West Antarctica and traverses a 120-kilometer stretch of frozen coastline. A third of the glacier, along its eastern side, flows more slowly than the rest, as it is ‘contained’ by a floating ice shelf, a ‘seamount’ that slows its flow. However, this ‘seat belt’ “won’t last long,” says Erin Petitt, an associate professor at Oregon State University.
Deep down, warmer ocean water circulating beneath the floating eastern side is attacking this glacier from all angles, his team found. “This phenomenon is melting the ice directly from below, and in doing so, the glacier loses its grip on the seamount. Huge fractures have formed and are growing, accelerating their demise,” says Pettit. “This floating extension of Thwaites Glacier will likely survive only a few more years.”
More threats
The warm water is also a threat to the so-called ‘grounding zone’, the area where the glacier sits on the seabed. Peter Davis, a physical oceanographer with the British Antarctic Survey, and his team use hot water to drill access holes from the surface of the ice shelf to the ocean cavity hundreds of meters below. They have found that the ocean waters in the land-connection zone are, by polar standards, warm, as well as salty, so a ‘perfect storm’ has been generated to melt the ice shelf from below.
Peter Washam, a research associate at Cornell University, also studies the grounding zone. His team plunged a robot through the borehole to take measurements of the ocean, ice, and seafloor in this region. They mapped these properties down to the point where the ice and the seafloor come into contact. Washam describes the grounding zone as “chaotic,” with warm water, steep ice, and a steep, sloping bottom that allows water to rapidly melt the ice sheet from below.
And that’s not all. Upstream of this waterline, researchers have found that tides pump water under the adjacent ice sheet. Lizzie Clyne, an adjunct professor at Lewis and Clark College, and her team study the tidal pumping mechanism that physically forces warm water between ice and bedrock at Thwaites. The floating portion of the glacier rises and falls with the tides, and that movement acts as a lever, pumping water under the ice sheet. Also, downstream of the grounding zone at the bottom of the floating ice shelf, constant stretching and melting are rapidly creating long channels through the ice that water can flow through, affecting long-term stability. term of the ice shelf, says Clyne.
As Thwaites retreat upriver and into the ice sheet, they can form very tall ice cliffs facing the ocean. anna Crawford, a researcher at the University of St. Andrews, and her team use computer modeling to study ice cliff failure: a process by which ice can break off glacier ends into the open ocean. The process can take many forms, but all of them could lead to a very rapid retreat of the huge glacier. The shape of West Antarctica’s bedrock makes the region vulnerable to rapid retreat through breakage of ice cliffs, as higher and higher cliffs could be exposed as the ice retreats. This phenomenon could lead to a chain reaction of fracture, resulting in collapse, as Crawford explains. One challenge for the team is to assess if, when, and how quickly this could happen,
“If Thwaites were to collapse, it would take most of the West Antarctic ice with it,” says Scambos. That is why it is essential to have a clearer idea of how the glacier will behave during the next 100 years.”
