Antarctica’s ‘Doomsday Glacier’ May Be More Dangerous Than Thought

Antarctica’s so-called “Doomsday Glacier” may pose an even greater threat to global coastlines than scientists previously estimated, according to a new study.

Located in western Antarctica, Thwaites Glacier is a vast frozen river spanning an area larger than Great Britain.

A complete collapse could eventually push global sea levels up by about 26 inches (65 centimetres), creating severe consequences for coastal communities around the world.

Scientists do not expect the entire glacier to disappear imminently, but they say Thwaites is moving increasingly quickly towards a dangerous tipping point.

New projections indicate that warmer ocean water is melting the glacier from below at a faster pace than previously understood. That process could contribute as much as 1.2 inches (30mm) to sea-level rise by 2100—twice the amount suggested by earlier estimates.

The major revision stems from a more detailed model of the conditions beneath the glacier, allowing researchers to better account for how seawater interacts with the ice at its base.

Study co-author Professor Eric Rignot of the University of California said: “Most projections to date have struggled to match the rapidity of the mass loss because of missing physics; our new model with more complete physics can match the record and then produces projections that are twice as large as before.

“These results predict greater risk of and exposure to coastal flooding than anticipated in the coming decades.”

Thwaites has experienced a worrying pattern of rapid thinning and retreat over the past several decades.

Yet the computer simulations used to forecast its future have increasingly failed to match evidence gathered by satellites.

Existing models suggested the glacier would advance into the ocean at a far slower rate than the acceleration now being recorded by researchers.

In a new study published in the journal Nature Communications, Professor Rignot and his colleagues developed a model designed to more closely reflect what is happening in the real world.

Lead author Dr Mattia Poinelli of UC Irvine said: “Glaciologists have long based their assumptions of ice sheet dynamics on the ‘grounding line’, a discrete, narrow and mostly stable demarcation where ice leaves the land and begins floating on water.”

“We have come to acknowledge a different arrangement beneath Earth’s major ocean-terminating glaciers.”

Satellite observations now suggest that these glaciers do not end at a single, sharply defined boundary. Instead, they extend into what scientists describe as a “grounding zone”.

The zone can stretch for several miles, allowing warm seawater to move far beneath the ice and drive much faster melting than earlier models accounted for.

For the study, the researchers examined measurements from Finland’s ICEYE satellite constellation, which tracks subtle shifts across the surface of the ice.

Those observations revealed that seawater travels several miles beneath the grounded section of the glacier, lifting the ice during the rise and fall of the tides.

As the ice lifts, the grounding zone is flushed with pressurised, warm seawater that is being pushed into the Antarctic coastline by currents already altered by climate change.

Using these new observations to model Thwaites’ future behaviour, the researchers discovered that the glacier is likely to melt much faster than previously thought.

They were then able to reconstruct historical glacier change from the 1990s to the present that is four times more pronounced than traditional models.

YOU MAY ALSO READ: Education Secretary Lucy Powell: Put Speaking Alongside Reading and Writing

A major concern is the fact that these grounding zone processes appear to be accelerating the detachment of the Thwaites Glacier from its stabilising ridges.

Currently, the Doomsday Glacier’s flow into the ocean is being held back by critical points where the ice is attached to elevated parts of the seabed, such as the vital Mouginot Ridge.

However, as water is forced up and under the ice, melting processes are wearing away that grounding connection.

According to their new model, there is now a 60 per cent chance that Thwaites will become disconnected from the Mouginot Ridge by the end of the century.

Dr Poinelli says: ‘Once that ridge is unpinned, the glacier will continually retreat across a predominantly retrograde seafloor toward its next topographic high, the South Ridge.’

This comes after studies suggested that the Thwaites Glacier is close to losing its entire ice shelf in the coming year or so.

The Thwaites Eastern Ice Shelf is a wall of ice attached to the glacier’s eastern flank, holding back the flow of ice into the sea.

This supporting barrier is over 1,150ft (350m) thick and covers 580 square miles (1,500 square kilometres) – about the area of Greater London.

However, the Antarctic’s warming oceans are now thinning this frozen bulwark at an alarming rate.

Speaking in May, Dr Robert Larter, a marine geophysicist at the British Antarctic Survey, warned that the shelf’s breakup is ‘very likely to happen sometime this year’.