In western Antarctica, the titanic Thwaites glacier could, in the future, retreat more than twice as fast as its current rate, reveals a scientific study published on Monday, September 5. Its total disappearance would lead to a rise in the sea of ​​several meters.

Seven times the size of Brittany, the Thwaites glacier flows into the bay of Ile du Pin in western Antarctica. It juts out into the sea as a gigantic floating ice shelf. This frozen titan is placed on

feet of clay for decades, the fault of natural climatic variations and climate change due to human activities, scientists point out.

He is followed like milk on fire by teams all over the world. “Its floating ice platform is like a cork on a bottle, it retains the part of the glacier located upstream. However, it is in the process of fracturing more and more”, observes glaciologist Olivier Gagliardini, from the Institute of Environmental Geosciences in Grenoble.

A possible sea level rise of 3.3 m

The ice that Thwaites loses contributes to 4% of global sea level rise today, The International Thwaites Glacier Collaboration reminds us, but its impact could be much greater in the future, because the acceleration of its decline, which is said to have doubled over the past 30 years. According to some simulations, the complete collapse of the Thwaites glacier would raise global sea levels by 65 cm. Worse, its disappearance could cause a chain reaction on neighboring glaciers, which could lead to the total loss of the West Antarctic ice sheet, anticipates the magazine Science. Consequence, then, for the global sea level: a cataclysmic rise of 3.3 m… What is worth to the Thwaites glacier the media nickname of “glacier of the apocalypse”.

The question is to know when such an event could occur. “Over a very long period of several centuries”, estimates Olivier Gagliardini. “But today, models of the future of the polar ice caps are limited by the fact that we lack data on the maximum speed of the retreat of the line of stranding of the glaciers, which marks the limit between the ice resting on rock and the one floating on the ocean (see infographic). When this line recedes, the part of the glacier resting on the continent will decrease in quantity and all that is lost will contribute to the rise in the level of the oceans”, notes the Grenoble glaciologist.

A decline of more than 2.1 km per year

It shows that the receding speed of the grounding line could go up to more than double that known recently. The team led by Alastair Graham, a marine geologist from the University of South Florida, mapped the seabed in front of the Thwaites Glacier, which it once covered. Using an autonomous submarine, scientists have discovered hundreds of parallel ribs on the ocean shelf, ancient stranding lines. These ribs formed daily to the rhythm of the movements initiated by the tides. The scientists measured the spacing between them and were able to conclude that the glacier had experienced a very rapid episode of retreat in the relatively recent past, before the emergence of satellite technology which makes it possible to follow, with supporting images, the evolution of the ice shelves: “Over a period of 5.5 months, the Thwaites stranding line retreated at a rate greater than 2.1 km per year, twice the rate observed by satellite in the part of the stranding area that is shrinking the fastest between 2011 and 2019”. They don’t know exactly when it happened, probably between 50 and 200 years ago; possibly in the 1940s. The authors suggest that these episodes of accelerating glacier retreat alternate with slower ones similar to today, during which the glacier’s floating shelf remains “stuck” on a rocky ridge , which keeps it in place and also reduces the destructive passage of warm ocean waters under it…

Too late to act?

Worrying, these new results make Robert Larter, co-author of the study, tell the Washington Post that “Thwaites is holding on by the end of its nails today. We should expect to see big changes on small timescales in the future – even from year to year – once the glacier retreats beyond a shallow ridge in its bed.” .

What can be done to try to stem the process? “We must, of course, continue to reduce our greenhouse gas emissions. But for the Thwaites glacier, the possibilities of human intervention are now limited, as the time of inertia is great – several decades no doubt – between our actions and the effects they could have on it”, concludes Olivier Gagliardini.

What happens when the Thwaites Glacier in Antarctica, the so-called “Glacier of the Apocalypse”, breaks up?

Many Climate Change activists have recently suggested that the “doomsday” that the term “Doomsday Glacier” – the nickname given to the Thwaites Glacier in Antarctica – could be coming soon. But how will that day be?

As mentioned in a scary new sheet in the journal Natural Earth Sciences According to a team led by oceanographer geologist Alistair JC Graham, Antarctica’s Thwaites Glacier may be closer to a major breakup event than previously thought. thought before.

Here’s what’s new in our understanding of this situation: This new study analyzed ridges on the sea floor. These rib-like formations reveal powerful clues to the centuries-old location of the glacier, pushed by the tide every day. This differs from data previously collected on the glacier, taken from satellite maps of the ice as it moves ever closer to full (or near full) avalanche in the ocean,