For a while now, glaciologists have been worried that as the oceans warm and rise, coastal glaciers will be lifted clear of the sea floor, allowing them to flow much faster. The Thwaites glacier in Antarctica has been of particular concern, because it’s holding back enough ice to raise global sea levels by as much as ten feet. If the glacier starts flowing into the ocean faster, the ice behind it will also speed up. As you can imagine, knowing the shape of the sea floor is key to understanding and predicting what the glacier will do. More than that, it can give us insight into what the glacier has done in the past.

And what it has done in the past is worrisome, to say the least:

For the first time, scientists mapped in high-resolution a critical area of the seafloor in front of the glacier that gives them a window into how fast Thwaites retreated and moved in the past. The stunning imagery shows geologic features that are new to science, and also provides a kind of crystal ball to see into Thwaites’ future. In people and ice sheets alike, past behavior is key to understanding future behavior.

The team documented more than 160 parallel ridges that were created, like a footprint, as the glacier’s leading edge retreated and bobbed up and down with the daily tides. “It’s as if you are looking at a tide gauge on the seafloor,” said Graham. “It really blows my mind how beautiful the data are.”

a–d, Examples of high-frequency sidescan imagery illustrating the back-stepping conformity of ridge shape (a), non-alignment of ribs to underlying lineations (b), rib formation on terraces (c) and the ‘beading’ (red circle) and overprinting (red arrow) of existing subglacial features (d). e, Multibeam hillshade showing fine-scale landforms, <20 cm high, crossing lineation ridges and grooves. f, Corresponding profile X–X′, demonstrating the subtle geometries of some of the landforms (5–20 cm) and their surprising depth (>740 m). g,h, Multibeam swath bathymetry covering the longest series of ribs (profile Y–Y′ and Z–Z′ combined; stars mark start and end of profile sections). Inset shows close-up example of lateral continuity in the southern portion of the ribs. Black arrows in ‘b’ mark lateral continuation of one oblique ridge. Yellow arrows in each image show ice flow direction inferred from lineations.

Beauty aside, what’s alarming is that the rate of Thwaites’ retreat that scientists have documented more recently are small compared to the fastest rates of change in its past, said Graham.

Yeah, “alarming” feels like the right word.

With global warming, it’s not just the changes that are happening that causes problems – it’s the speed. Faster changes mean more people dead. It really is that simple. That’s also why slower action to respond to climate change means more people dead. We know that this sea level rise is coming, we know we’re not ready for it, and we’re doing next to nothing to get ready. The death-cult of Neoliberalism, with its dogmatic adherence to laissez-faire capitalism, could not have taken over the United States at a worse time.

To understand Thwaites’ past retreat, the team analyzed the rib-like formations submerged 700 meters (just under half a mile) beneath the polar ocean and factored in the tidal cycle for the region, as predicted by computer models, to show that one rib must have been formed every single day.

At some point in the last 200 years, over a duration of less than six months, the front of glacier lost contact with a seabed ridge and retreated at a rate of more than 2.1 kilometers per year (1.3 miles per year) — twice the rate documented using satellites between 2011 and 2019.

“Our results suggest that pulses of very rapid retreat have occurred at Thwaites Glacier in the last two centuries, and possibly as recently as the mid-20th Century,” said Graham.

“Thwaites is really holding on today by its fingernails, and we should expect to see big changes over small timescales in the future – even from one year to the next – once the glacier retreats beyond a shallow ridge in its bed,” said marine geophysicist and study co-author, Robert Larter, from the British Antarctic Survey.

Completely aside from its implications, this mission was an accomplishment all on its own. Getting close to the edge of a rapidly retreating glacier is difficult and dangerous. In this case, it was only possible because of record lows in sea ice, combined with advances in technology.

To collect the imagery and supporting geophysical data, the team, which included scientists from the United States, the United Kingdom, and Sweden, launched a state-of-the-art orange robotic vehicle loaded with imaging sensors called ‘Rán’ from the R/V Nathaniel B. Palmer during an expedition in 2019. Rán, operated by scientists at the University of Gothenburg in Sweden, embarked on a 20-hour mission that was as risky as it was serendipitous, Graham said. It mapped an area of the seabed in front of the glacier about the size of Houston – and did so in extreme conditions during an unusual summer notable for its lack of sea ice. This allowed scientists to access the glacier front for the first time in history.

Anna Wåhlin, a physical oceanographer from the University of Gothenburg who deployed Rán at Thwaites, said, “This was a pioneering study of the ocean floor, made possible by recent technological advancements in autonomous ocean mapping and a bold decision by the Wallenberg foundation to invest into this research infrastructure. The images Ran collected give us vital insights into the processes happening at the critical junction between the glacier and the ocean today.”

“It was truly a once in a lifetime mission,” said Graham, who said the team would like to sample the seabed sediments directly so they can more accurately date the ridge-like features. “But the ice closed in on us pretty quickly and we had to leave before we could do that on this expedition,” he said.

While many questions remain, one thing’s for sure: It used to be that scientists thought of the Antarctic ice sheets as sluggish and slow to respond, but that’s simply not true, said Graham.

“Just a small kick to Thwaites could lead to a big response,” he said.

And that brings us back to our regularly scheduled existential dread!

I believe this glacial retreat, and associated sea level rise are going to happen. I do not think it is a question of “if”, but of “when”. I suppose it is hypothetically possible that all of the world’s rich and powerful decide to completely change how they’ve always behaved. It’s “possible” that they could invest in truly dealing with climate change and its attendant problems. Were that to happen, it’s possible that through herculean effort, we could even stop the warming in my lifetime. Maybe.

I think it is equally possible that I will be named king of the world.

The unfortunate reality is that before we can devote the needed time and resources to climate mitigation and adaptation, we need revolutionary political and economic change. It’s my hope that in working towards that will also push more incremental change, like the recent climate bill. Things like that will never be enough to solve the problem, but they can slow things down, and buy us the time that this research shows we very much need.

This is one more warning among so many that it almost feels like white noise at this point. I think that could be a very real danger. In addition to our propensity to think that “the weather has always been like this”, after a certain point we just don’t have the energy to get worked up over every new apocalyptic update. I think the antidote to that is to keep the focus on the step we’re currently on – building collective power. Networking and organization aren’t just tools for affecting political change – they can also make a community more resilient, and better able to survive the disasters that our governments are too corrupt and incompetent to prevent.

When disaster strikes, humanity is always forced back to our single greatest strength – the ability to work together to achieve more than any of us could alone. Warnings like this give us a heads-up that we need to be exercising that muscle now, so that it’s fit for purpose when we really need it.

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