Thwaites Glacier ‘holding on by its fingernails’ says British Antarctic Survey as speed of earlier retreats revealed
The massive Thwaites Glacier - which is the size of the UK - is “holding on by its fingernails” say British Antarctic Survey (BAS) scientists, who have learned more about its past retreats from new high resolution images of the seafloor in West Antarctica.
There are heightened concerns over the massive ice shelf after the images revealed that at times its retreat was even quicker than it is today.
The glacier is already in a phase of fast retreat, or “collapse”, which it is thought could lead to global sea-level rises up to an astonishing 65cm.
Scientists mapped a critical area of the seafloor in front of the glacier to understand the speed with which Thwaites has moved and retreated before, uncovering 160 parallel ridges that were created like footprints as its leading edge retreated and bobbed up and down with the daily tides.
Analysing the rib-like formations that are submerged 700 metres beneath the polar ocean, and factoring in the region’s tidal cycle, they worked out that one ‘rib’ must have been formed every single day.
They found that at some point in the last 200 years and over a duration of less than six months, the front of the glacier lost contact with a seabed ridge and retreated at a rate of more than 2.1 kilometres, or 1.3 miles, per year. This is twice the rate documented using satellites between 2011 and 2019.
Marine geophysicist and study co-author Dr Robert Larter, from the BAS in Cambridge, said: “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.”
The team of scientists from the UK, US and Sweden used an orange robotic vehicle called ‘Rán’, laden with imaging sensors, to map an area the size of Houston on the seafloor in a risky 20-hour mission in 2019.
Anna Wåhlin, a physical oceanographer from the University of Gothenburg who deployed Rán at Thwaites, says: “This was a pioneering study of the ocean floor, made possible by recent technological advancements in autonomous ocean mapping and a bold decision by the Wallenberg Foundation to invest into this research infrastructure. The images Rán collected give us vital insights into the processes happening at the critical junction between the glacier and the ocean today.”
The summer was notable for its lack of sea ice, which allowed the team to access the glacier front for the first time.
“It’s as if you are looking at a tide gauge on the seafloor,” says lead author Dr Ali Graham from Florida University. “Our results suggest that pulses of very rapid retreat have occurred at Thwaites Glacier in the last two centuries, and possibly as recently as the mid-20th century.
“It was truly a once in a lifetime mission.”
The data will help inform global planning for sea rises. About 40 per cent of the human population lives within 60 miles of the coast, according to the UN.
