“Gloomy prospects” for the Thwaites Glacier

​​After six years of intensive probing and sampling with submarines, satellites and drills on a chunk of ice the size of Florida in West Antarctica, scientists from the International Thwaites Glacier Collaboration said Thursday that the worst-case scenario of glacier melting still cannot be ruled out as emissions of climate-warming greenhouse gases reach new record levels every year.

Combined with meltwater from other parts of Antarctica and Greenland, as well as from mountain glaciers around the globe, and the thermal expansion of warming oceans, melting of the Thwaites Glacier could cause sea levels to rise two meters higher than today by 2100, researchers say.

Many coastal communities would not be able to adapt to such a large sea level rise in this timeframe, and millions of people would likely be forced to flee their homes as extreme flooding devastates low-lying cities, residential areas, farmland and natural ecosystems. This rise in water levels would completely swallow some small islands within a few decades.

The Thwaites Glacier is over 1,800 metres thick in places and contains enough ice to raise sea levels by 60 centimetres if it melts completely. It is also a cornerstone holding back the West Antarctic Ice Sheet, which lies mostly on a bed below sea level and would raise sea levels by about 3.3 metres if it reached completely to the sea.

The glacier has been retreating for 80 years. This process has accelerated significantly over the past three decades and will accelerate even further in the coming years, the researchers said during the release of a scientific briefing on the key findings from studies conducted by hundreds of researchers working on different parts of the glacier and in the adjacent ocean.

The international collaboration was led by the British Antarctic Survey and the United States National Science Foundation and included scientists and research instruments and equipment from several other countries, including Germany and South Korea.

“Our results suggest that Thwaites will retreat further and faster,” said Rob Larter, coordinator of the research team and a marine geophysicist with the British Antarctic Survey. Some of the team's studies in recent years have revealed new vulnerabilities that could accelerate the glacier's retreat faster than expected, he added.

Overall, the scientific briefing suggests that a complete collapse of Thwaites Glacier this century is somewhat less likely than previously thought. However, the latest models predict accelerated ice loss in the 22nd and 23rd centuries, potentially leading to a “general collapse of the West Antarctic Ice Sheet in the 23rd century.”

Some of the data was collected by remote-controlled submarines and shows how tides can trigger surges of water beneath glaciers, causing more melting. Other scientists looked at melting at the surface and how pooling water and more precipitation can weaken the ice from above. In some cases, towering ice cliffs could collapse like dominoes, causing city-sized sheets of ice to crumble in sudden bursts.

The scientists also found that the floating extension of the Thwaites Glacier – its ice shelf – is close to breaking off completely. That would not directly accelerate sea level rise significantly, they said, because the ice is already in the ocean. But it is uncertain how the glacier front at the edge of the sea will respond once the floating ice shelf is gone.

Irreversible changes

“It is really worrying that the latest models all indicate that an irreversible decline has already begun,” said climate scientist James Kirkham of the University of Cambridge, chief scientific adviser to the International Cryosphere Climate Initiative.

The rate of sea level rise is already overwhelming coastal ecosystems such as mangroves and wetlands that help buffer storm-related floods, he added.

“I was in Houston earlier this year and because much of the land is subsiding, sea levels are rising by about 8 millimeters a year,” he said, adding that coastal ecosystems such as marshes cannot keep up with that rate of change. Climate experts in the region say those ecosystems are drowning, he said.

Once that happens, he added, “they will lose very large areas of wetland, and very quickly, probably within decades rather than in the long term.”

The root of the problem is that “eight billion misbehaving monkeys” are ravaging the planet, said Dominic Hodgson, deputy scientific director of the British Antarctic Survey.

“We form tribes and fight a lot,” he said. “We also go around burning things. First it was dung, then the trees, then we moved on to oil and gas. We are just continuing to destroy our planet. Burning biomass and fossil fuels has led to carbon dioxide concentrations in our atmosphere that are more than 1.5 times higher than they should be… so we have completely thrown our planet out of its natural balance.”

Hodgson said the Thwaites collaboration was part of the scientific community's “great challenge” to determine “how much and how fast this sea level rise will be, where it will come from and where the impacts will be felt.”

He said geological records show that sea levels do not always rise evenly, but “occur in jumps, and these jumps can be quite violent, several meters over the course of a few hundred years.”

Recent studies off the coast of West Antarctica have supported the idea that earlier geological periods of rapid warming were accompanied by periods of rapid melting. Detailed mapping of the seafloor shows patterns of grooves that indicate ice shelf retreat of more than 1 mile per year.

The $50 million research project may not have answered all the important questions about West Antarctica's ice, but there were some real eureka moments, says glaciologist Kiya Riverman, an assistant professor of environmental studies at the University of Portland who piloted a robotic submarine that directly observed the run-up line of the Thwaites Glacier's floating ice shelf for the first time.

The grounding line is where the bottom of an ice shelf jutting out to sea is anchored to a ridge on the seafloor that prevents the ice shelf from retreating. But these grounding lines are very sensitive to warming sea water and changing currents. Being able to see exactly what's happening there can help refine sea level rise predictions.

“I think for glaciologists, this had the same emotional impact as perhaps the moon landing had on the rest of society,” Riverman said. “We saw this place for the first time.”

She said she started studying glaciers because she liked “the fundamental questions we were asking and how little we knew about glaciers.”

Sometimes, while doing hard physical work in the extreme weather on the Thwaites Glacier, she thought, “I should be miserable, right? But it was the best time of my life,” she said.

“We had American planes and British exercises, Korean ships and German instruments and scientists from all these places,” she said. “And so we could actually start to answer some of these fundamental questions. And there's nothing more satisfying than that.”