Its collapse would raise global sea levels by more than half a metre on its own, and subsequently release other major bodies of ice in West Antarctica, which together could raise sea levels by 2-3 metres. The ramifications for many countries, including most of the world’s coastal cities, would be catastrophic.
For this reason, Thwaites is known as Antarctica’s “Doomsday glacier”.
Earlier this year a team of scientists observed, for the first time, the presence of warm water at a vital point underneath the glacier, which helps explain the reason behind the extent of its decrease.
The Thwaites glacier is 74,000 square miles, roughly the size of the UK. The ice melt draining from Thwaites into the Amundsen Sea already accounts for 4 per cent of global sea-level rise but scientists are concerned its continued existence is hanging in the balance as the world warms.
“The big question is how quickly it becomes unstable. It seems to be teetering at the edge,” Paul Cutler, programme director for Antarctic glaciology at America’s National Science Foundation told the Financial Times this week.
“It is a keystone for the other glaciers around it in West Antarctica,” he said. “If you remove it, other ice will potentially start draining into the ocean too.”
Rob Larter, UK principal investigator for the Thwaites Glacier Project at the British Antarctic Survey, added: “It is the most vulnerable place in Antarctica.”
Antarctica accounts for vast quantities of ice – around 90 per cent of all ice in the world - and unlike in the Arctic, most of the ice is out of the water and on land. The average thickness of the ice is 1.6 miles deep. At its thickest point, the ice sheet is almost three miles deep.
Current sea level is around 20cm (almost 8 inches) above pre-industrial levels and is blamed for increased coastal flooding.
For about 2,000 years until the late 1800s, global sea levels remained almost static with small fluctuations.
The burning of fossil fuels ramped up during the Industrial Revolution in the mid-18th century, increasing levels of carbon dioxide (CO2) in the atmosphere. The greenhouse gas absorbs heat from the sun and traps it, heating the atmosphere and the planet.
Our rapidly-warming planet causes sea levels to rise on two fronts. Warmer temperatures melt ice sheets and glaciers, leading the run-off to flow into oceans. The ocean also absorbs excess heat from greenhouse gas emissions and warm water expands, taking up more space than colder water.
The annual rate of sea-level rise has roughly doubled since 1990.
Scientists previously found the extent of the instability of the Antarctic ice sheet difficult to study but improved technologies are allowing greater insight into the changes in the ice on, and surrounding, the continent.
In January, a probe designed to search for alien life on Jupiter’s Moon Europa was tested by scientists working at Thwaites.
The cylindrical robot was lowered down a 600m-deep hole just 35cm in diameter to measure the waters moving below the glacier's surface.
It measured temperatures and also the turbulence of the water - a means of testing the mixing of fresh meltwater from the glacier and salty water from the ocean. The turbulence allows scientists to understand the rate of melting and therefore the overall stability of the glacier.
The latest warning over Antarctica’s melting glaciers comes amid a record heatwave on the other side of the planet in the Arctic.
Both the Antarctic and Arctic regions are warming faster than the rest of the world but in the Arctic temperatures have hit record highs, with an alarming all-time high of 38C recorded in Siberia in June.
The high temperatures have fuelled hundreds of wildfires and Russian authorities have declared emergency situations in seven regions.