Anglophones call him the “doomsday glacier“, or glacier of the apocalypse. And there is reason for it: if this giant, 120 km wide and 600 km long, were to melt completely, it would alone cause a rise in the level of the oceans estimated between one and three meters.
A rise in water levels of such magnitude could engulf part of the world’s coastal areas, while more than 40% of humanity lives less than 100 km from the coast (UN). However, a previous study had highlighted the high risk of bursting, in the next 5 years, of the part of the glacier which, until now, kept it from collapsing into the Southern Ocean.
Tracing the history of the glacier, to better anticipate its future
If uncertainty reigns as to the time frame of the announced disaster, a team of American, British and Swedish researchers has decided to map – for the first time in high resolution – the ocean floor located at the edge of the Thwaites. Their objective: to shed light on the history of the glacier, in order to be able to better anticipate its future.
To collect the necessary images and data, these scientists embarked in 2019 on board an oceanographic vessel, the “R/V Nathaniel B. Palmer”, from which they launched “Rán” – a robotic vehicle, covered with sensors ultra-precise.
For 20 hours, the robot had to brave extreme weather conditions – because that summer was marked by an absence of surface ice – in order to cover an underwater territory of more than 1600 km2, sounding its radar at around 700 meters below the surface of a raging polar ocean.
The imprint of a melting glacier
According to the study resulting from this high-risk expedition, published in the journal Nature Geoscience, the ocean floor is etched with some 160 parallel ridges, forming a sort of imprint. This would correspond to the trace of a melting of the glacier, which would have occurred at an undetermined date during the last 200 years, and which would have lasted, in all and for all, less than six months.
The spacing between these streaks, each corresponding to the advance and then the retreat of the ice according to the daily tides, enabled the scientists to calculate the speed of this past melting. Result: more than 2 km per year, double the speed recently estimated by satellite between 2011 and 2019.
However, according to the authors of the study, the change in the rate of melting – that is to say its acceleration – observed in our time could turn out to be much higher than in the past. This does not bode well for the near future, warn the researchers.
“The Thwaites Glacier is hanging by a thread”
“Thwaites Glacier is now hanging by a thread, and we should expect to see big changes on small timescales in the future, even from year to year, as the glacier retreats to the beyond a shallow ridge in its bed“, warns Robert Larter, marine geophysicist and co-author of the study, member of the British Antarctic Survey, quoted in a communicated.
“Just because he’s out of our sight doesn’t mean Thwaites should stay out of our minds“, underlines for his part Tom Frazer, dean of the College of Marine Sciences at the University of South Florida (USF). The gaze of researchers, on the other hand, should remain riveted on this colossus of ice as threatened as it is threatening for the months and years to come.
Read also :