Scientists warn that a huge Antarctic glacier on the brink of collapse could raise sea level by just half a meter

A huge glacier the size of Florida is likely to melt so quickly that it could cause a catastrophic rise in sea level, scientists warned.

While the climate crisis has caused a surge in temperatures and a rapid reduction of ice levels in the Arctic, In Antarctica, it is thought today that much larger layers of ice, containing much more water, are likely to collapse, although they have previously been considered stable.

Thwaites Glacier is one of five recently identified unstable Antarctic glaciers that have doubled their ice loss rate in just six years.

Covering 70,000 square miles, it is likely to accelerate its flow into the ocean, a new study on the stability of the Antarctic Ice Sheet has suggested.

Once it has crossed a tipping point, it will become an unstoppable process that could raise sea levels much faster than previously expected.Researchers at the Georgia Institute of Technology, NASA Jet Propulsion Laboratory and the University of Washington said after using computer models to predict the effects of glacier instability on ice-breaking velocity.

All models were pointing towards the glacier, reaching a tipping point and the subsequent collapse of the ice cap, they said.

In the worst case, Thwaites Glacier ice alone could raise sea levels by nearly half a meter (20 inches) in less than 150 years.

The team warned that once the tipping point is reached, even if global temperatures decrease, the flow of the glacier into the sea would already be impossible to stop.

"If you trigger this instability, you do not need to continue forcing the ice cover by raising the temperature. This will continue, and that's the concern, "said the study's chief Alex Robel, Assistant Professor, School of Earth and Atmospheric Sciences, Georgia Tech.

"Climatic variations will always be important after this tipping point, as they will determine the speed at which the ice will move."

NASA scientist Hélène Seroussi added: "After reaching the tipping point, Thwaites Glacier could lose all its ice in 150 years. This would make a sea level rise of about half a meter (1.64 feet). "

By comparison, the current sea level is 20 cm above pre-global warming levels and is the cause of the increase in coastal flooding.

For about 2,000 years until the late 1800s, the world's seas remained almost static, with small fluctuations, but then began to rise, according to the Smithsonian Institution.

The annual rate of sea level rise has almost doubled since 1990.

The extent of instability of the Antarctic Ice Sheet is difficult to study, but computer models predicting its future collapse pose challenges to forecasters and climate modeling teams because they offer a wide range of potential scenarios.

This is particularly relevant to the challenge of engineering against the dangers of flooding.

"You want to design critical infrastructure to withstand the upper limit of potential sea-level scenarios in a hundred years," said Dr. Robel. "It can mean building your water treatment plants and your nuclear reactors in the worst case, which could be a sea level rise in Thwaites Glacier alone, which is a huge difference."

The Antarctic contains large amounts of ice – about 90% of the world's ice – and unlike 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 layer of ice is almost three miles deep.

As a result, the collapse of its ice caps presents more serious scenarios for sea level rise. While in the Arctic, 90% of the iceberg's mass is already under water. When the ice melts, the volume decreases, resulting in little change in sea level.

Instability under the Thwaites Glacier would be related to the topography of the ice and sea meet zone.

The "grounding line", where the bottom of the ice cap rests on the bottom of the sea, can retreat under the glacier due to warming ocean waters that are digging ice.

In deeper areas, ice above the sea floor can move faster because the water gives it more lift, which can accelerate the movement of the glacier.

"Once the ice has passed over the ground line and a little above the water, it contributes to the sea level because the buoyancy holds it more than it was before" , said Dr. Robel. "The ice pours on the floating ice floe and melts or breaks into an iceberg."

Dr. Seroussi added, "The process becomes self-perpetuating."

The study is published in Proceedings of the National Academy of Sciences.