‘Doomsday’ glacier set to melt faster, causing seas to swell as planet warms, scientists say

Tidal action on the underside of Antarctica’s Thwaites Glacier will “inexorably” accelerate the melting of the ice sheet this century, according to a new study by British and American scientists. The researchers warn that this faster melting could destabilise the entire West Antarctic ice sheet, leading to its collapse.

This giant glacier, which is about the size of Florida, is of particular interest to scientists because of how quickly it is changing and the impact its disappearance would have on sea levels (which is why it is nicknamed “Apocalypse”). It also acts as an anchor to hold back the West Antarctic ice sheet.

At over 2 kilometres thick in places, Thwaites has been compared to a cork in a bottle. If it collapsed, sea levels would rise by 65 centimetres. That’s a significant amount, given that ocean levels are currently rising by 4.6 millimetres per year. But if it led to the disappearance of the entire ice sheet, sea levels would rise by 3.3 metres.

Although some computer models suggest that greenhouse gas emission reductions under the 2015 Paris Agreement could mitigate the glacier’s retreat, the outlook for the glacier remains “bleak,” according to a report from the International Thwaites Glacier Collaboration, or ITGC, a project that includes researchers from the British Antarctic Survey, the U.S. National Science Foundation and the U.K. Natural Environment Research Council.

The Thwaites Glacier has been retreating for more than 80 years, but that process has accelerated in the past 30 years, Rob Larter, a marine geophysicist who contributed to the research, said in a news release. “Our findings indicate that the glacier is poised to retreat further and more rapidly.” Other dynamics not currently incorporated into large-scale models could accelerate its demise, the new research suggests.

Using a torpedo-shaped robot, scientists were able to determine that the lower part of the Thwaites Glacier is insulated by a thin layer of cold water. However, in areas where parts of the glacier lift off the seafloor and the ice begins to float, tidal action pumps warmer, high-pressure seawater up to 10 kilometres beneath the ice.

This process disrupts this insulating layer and will likely significantly accelerate the rate at which the anchoring zone (the area where the glacier rests on the seafloor) retreats.

A similar process has been observed on the glaciers of Greenland.

The group also discussed a worst-case scenario, in which ice cliffs 100 metres or more high would form ahead of Thwaites and then rapidly break off into icebergs, causing uncontrolled glacier retreat that could raise sea levels by dozens of centimetres this century. However, the researchers said it was too early to know whether such scenarios were likely.

The key question is whether the loss of the Thwaites Glacier is already irreversible. Heavy snowfalls, for example, occur regularly in Antarctica and help replenish the ice melt, Michelle Maclennan, a climate scientist at the University of Colorado Boulder, said at a news conference. “The problem is that we have an imbalance: the ice melt is greater than the snowfall can compensate for,” she said.

Increased moisture in the planet’s atmosphere, caused by global warming and evaporation of ocean waters, could lead to more snow in Antarctica, at least for a while. But at some point, that’s expected to turn into rain and melting of the ice surface, creating a situation where the glacier melts from the top and bottom. How quickly that happens depends in part on how much progress nations make in slowing climate change.

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