Scientists have deployed an advanced robotic submarine to gain a new perspective on the Thwaites Glacier in West Antarctica, with the groundbreaking seafloor imagery highlighting its precarious state in concerning new detail. The research reveals the glacier has undergone spurts of rapid retreat in the past that scientists now expect to see again in the future, which could have important ramifications for global sea levels.
Around the size of Florida, the Thwaites Glacier is known as the “Doomsday Glacier” owing to its status as one of the most unstable glaciers in Antarctica. Its melt rate is accelerating, with its outflow speed doubling in the last 30 years, and some studies suggesting it could be just years away from a complete collapse. Were that to happen, the amount of water released from the giant ice stream would be enough to drive up global sea levels by several meters.
The Thwaites Glacier is known to be in a phase of fast retreat, but new research led by marine geophysicists at the University of South Florida reveals this might be occurring faster than we realize. In 2019, the team sent an advanced underwater robot loaded with imaging sensors on a 20-hour mission to map the seabed in front of the glacier.
Extreme summer conditions and a lack of sea ice enabled scientists to access this section of the seafloor for the first time ever. This bears a resemblance to another research expedition from 2020 in which scientists sent a robotic sub to inspect the Thwaites Glacier’s grounding line, the point where the seafloor meets the ice, to assess its stability.
This new study focused on the geography of the seafloor in front of the glacier, mapping a region around the size of Houston. This revealed features previously unknown to scientists, most notably a set of 160 parallel ridges formed as the glacier’s grounding line retreated and bobbed upwards and downwards with the shifting tides.
“It’s as if you are looking at a tide gauge on the seafloor,” said Alastair Graham, who led the study. “It really blows my mind how beautiful the data are.”
Matching these ridge formations with tidal cycles for the region revealed that each of these ribs must have been formed every day, enabling the team to draw conclusions about the rate of retreat. They calculate that at some point in the last two centuries, in a duration of five or six months, the glacier retreated at a rate of around 2.1 km (1.3 miles). This is twice the retreat rate measured by satellites between 2011 and 2019.
“Thwaites is really holding on today by its fingernails, and we should expect to see big changes over small timescales in the future – even from one year to the next – once the glacier retreats beyond a shallow ridge in its bed,” said marine geophysicist and study co-author, Robert Larter, from the British Antarctic Survey.
The research was published in the journal Nature Geoscience.
Source: University of South Florida
