The Collapse of the West Antarctic Ice Sheet Now Seems Inevitable.

I struggled a bit in thinking about what to post today. I’ve been working on a Gaza post for a little while now, but it keeps not feeling done, and then new things keep happening. I hope I’ll have it out very soon, but that’ll depend a bit on how well I can wrangle my brain this week. Then I was thinking about a post that can be summarized by paraphrasing Forrest Gump: “Cops are like a box of chocolates. They’ll kill your dog.” I may still write that one, but that felt a bit too grim, and hit a little too close to home. I have guests in town, and I didn’t want  to be putting myself in a bad mood while playing host. I considered a couple other topics, but eventually I turned to my standby, climate science headlines, and boy do they disappoint! Specifically, I always hope for good news, and am very often disappointed, so I’ve got bad news today! It’s exciting!

As you are all no doubt aware, this little planet of ours currently has two ice caps – one on top of the island of Greenland, and one on top of the continent of Antarctica. These are such massive sheets of ice that they generate a gravitational pull on the ocean surrounding their respective landmasses, pulling the water toward them in the same way that mountains do. I know it’s no surprise that there’s a lot of ice in those ice sheets, but it bears repeating, because those ice sheets are melting, and the hotter this planet gets, the faster they melt. I think it would be helpful, for today’s discussion, to think of the ice sheets that make up those ice caps as big lakes, and glaciers as the rivers flowing from them.

For a while now, the Thwaites glacier in Antarctica has been dubbed “The Doomsday Glacier”, which sounds like a disaster movie so over the top and campy it would put The Day After Tomorrow to shame. It’s called that because that glacier is all that’s keeping the west Antarctic ice sheet from sliding into the ocean. There has long been a worry that the combination of rising sea levels and warming water would lift the glacier above it’s current “grounding line”- the spot on the sea floor that’s currently slowing it down. If the bottom melts enough, and the glacier floats up enough, then it loses that friction, and can just flow out into the ocean, soon followed by the ice sheet. The final result of that would be 3-4 meters of sea level rise, or roughly 10-13 feet. The sea level rise in that time frame would considerably more than that, given contributions from the rest of Antarctica, from Greenland, from mountain glaciers, and from thermal expansion as the temperature continues to rise.

And so I regret to inform you that we have yet more bad news from the Thwaites glacier:

A team of glaciologists led by researchers at the University of California, Irvine used high-resolution satellite radar data to find evidence of the intrusion of warm, high-pressure seawater many kilometers beneath the grounded ice of West Antarctica’s Thwaites Glacier.

In a study published today in Proceedings of the National Academy of Sciences, the UC Irvine-led team said that widespread contact between ocean water and the glacier – a process that is replicated throughout Antarctica and in Greenland – causes “vigorous melting” and may require a reassessment of global sea level rise projections.

The glaciologists relied on data gathered from March to June of 2023 by Finland’s ICEYE commercial satellite mission. The ICEYE satellites form a “constellation” in polar orbit around the planet, using InSAR – interferometer synthetic aperture radar – to persistently monitor changes on the Earth’s surface. Many passes by a spacecraft over a small, defined area render smooth data results. In the case of this study, it showed the rise, fall and bending of Thwaites Glacier.

“These ICEYE data provided a long-time series of daily observations closely conforming to tidal cycles,” said lead author Eric Rignot, UC Irvine professor of Earth system science. “In the past, we had some sporadically available data, and with just those few observations it was hard to figure out what was happening. When we have a continuous time series and compare that with the tidal cycle, we see the seawater coming in at high tide and receding and sometimes going farther up underneath the glacier and getting trapped. Thanks to ICEYE, we’re beginning to witness this tidal dynamic for the first time.”

ICEYE Director of Analytics Michael Wollersheim, co-author, said, “Until now, some of the most dynamic processes in nature have been impossible to observe with sufficient detail or frequency to allow us to understand and model them. Observing these processes from space and using radar satellite images, which provide centimeter-level precision InSAR measurements at daily frequency, marks a significant leap forward.”

Rignot said the project helped him and his colleagues develop a better understanding of the behavior of seawater on undersides of Thwaites Glacier. He said that seawater coming in at the base of the ice sheet, combined with freshwater generated by geothermal flux and friction, builds up and “has to flow somewhere.” Water is distributed through natural conduits or collects in cavities, creating enough pressure to elevate the ice sheet.

“There are places where the water is almost at the pressure of the overlying ice, so just a little more pressure is needed to push up the ice,” Rignot said. “The water is then squeezed enough to jack up a column of more than half a mile of ice.”

Just to be clear, half a mile is just under the height of the tallest building in the world, we’re talking a solid sheet of ice, not a hollow building. I know the scale is probably familiar to everyone reading this blog, but I still find it a bit mind-boggling how much weight is being lifted by this slowly intruding water. Maybe it’s just that this is a small enough “big” part of what’s happening to the planet as a whole that I can just about wrap my brain around it. Unfortunately, this is exactly what scientists have long been fearing, because that layer of water isn’t just lifting the ice, it’s acting as lubrication, letting it slide faster, and worse, it’s speeding the melting from the underside:

And it’s not just any seawater. For decades, Rignot and his colleagues have been gathering evidence of the impact of climate change on ocean currents, which push warmer seawater to the shores of Antarctica and other polar ice regions. Circumpolar deep water is salty and has a lower freezing point. While freshwater freezes at zero degrees Celsius, saltwater freezes at minus two degrees, and that small difference is enough to contribute to the “vigorous melting” of basal ice as found in the study.

Climate scientists have been warning the world about the dangers of climate change since at least the 1950s, and all along the way, their projections have proven to be either accurate, or too optimistic. They’ve been ignored and dismissed by the rich and powerful, and contrary to the fantasies of climate science deniers, the scientists are not actually getting the support they need.

Co-author Christine Dow, professor in the Faculty of Environment at the University of Waterloo in Ontario, Canada, said, “Thwaites is the most unstable place in the Antarctic and contains the equivalent of 60 centimeters of sea level rise. The worry is that we are underestimating the speed that the glacier is changing, which would be devastating for coastal communities around the world.”

Rignot said that he hopes and expects the results of this project to spur further research on the conditions beneath Antarctic glaciers, exhibitions involving autonomous robots and more satellite observations.

“There is a lot of enthusiasm from the scientific community to go to these remote, polar regions to gather data and build our understanding of what’s happening, but the funding is lagging,” he said. “We operate at the same budget in 2024 in real dollars that we were in the 1990s. We need to grow the community of glaciologists and physical oceanographers to address these observation issues sooner rather than later, but right now we’re still climbing Mount Everest in tennis shoes.”

They’ll keep on climbing in those tennis shoes, but It feels like it would be a good idea to get them proper funding. The whole world is changing, and for all I called this a “little planet”, that’s a lot of area to cover, in studying how global warming is changing things. It’s nice to have a warning about what looks to be the unavoidable collapse of the west Antarctic ice sheet, but the less we fund climate science, the more likely are to get a nasty surprise.

The good news is that this process will not happen all at once. We do still have time to slow the warming, and to prepare for the rising sea. Even with the rapid acceleration, it will take many, many years for the ice sheet to flow into the ocean. This is not a meltwater pulse. That said, it will result in more rapid sea level rise throughout this century. As always, the degree to which this is a disaster will depend on what we do, as a species, to prepare for it, and to mitigate change. We’ve been warned with time to respond. The only question is whether we will heed that warning.


  1. says

    There’s no stopping it in Florida and Bangladesh. There’s no solid substrate. You can build a wall and the ocean will seep under it, emerging inside any protected region.

    Most of Africa is fine. Canada is in great shape. The Netherlands is in a bad situation but they do have experience with this engineering and with the qualities of the local bedrock. But there are huge sections of Brazil, Venezuela, Suriname, Guyana, and Argentina in South America, a few large and densely populated portions of China (from Beijing in the north to Shanghai on the central coast) and SE Asia (including but not only large swathes of Bangladesh), and an awful lot of the US gulf coast (and the entirety of the aforementioned Florida, even the Atlantic side) that has little chance of retaining its population centres. Los Angeles slopes up towards the hills, so they might lose… a third? Half? Not sure how flat the plain is. San Diego is bumpier, but you’re still going to lose a lot there.

    Oh, and it’s not going to happen instantly, but there’s only about 10m of elevated river delta separating the long slope down to the Salton Sea from the Sea of Cortez (between the Baja peninsula and mainland Mexico). If the sea level rises that much, a huge chunk of California farmland disappears under a lengthy inlet coming up from the Mexican Pacific Ocean.

    Yeah, we’re fucked.

  2. says

    Isn’t the collapse of agriculture going to be a bigger problem than the rising oceans? Or, will the heat depopulate the equatorial areas?

    Yeah, we’re fucked.

  3. Pierce R. Butler says

    Has there ever been a prediction from climatologists in the last half-century that didn’t happen sooner and worse than forecast?

  4. says

    Yeah, agriculture has me more worried than sea level rise (though as Crip Dyke said, they’re not unconnected), but with climate change it’s an “all of the above” situation. We’re gonna deal with sea level rise one way or another. Theoretically, a society willing to proactively relocate the population of Miami, for example, would also be actively working to climate-proof the food supply.

    @Pierce – not that I’m aware of? They do tend to “predict” probability spreads, so most of the time when they’re accused of “getting it wrong” it’s just someone pointing to the outlier scenarios.

  5. garnetstar says

    Isn’t the West Antarctic ice sheet the same one that Kim Stanley Robinson had collapse in the Mars trilogy, also from global warming? And then the whole world was so flooded that a lot of civilization collapsed too?

    And he wrote that book in 1996. The guy seems to have been pretty prescient.

  6. says

    @garnetstar – I couldn’t tell you. I’ve had the second two books for something like a decade now, and I keep forgetting to buy the first so I can read them all.

  7. lochaber says

    Adding onto what Crip Dyke brought up, Sacramento is also only about ~10 meters elevation, so that’s enough sea level change to start flooding the California Central Valley, which would also have a big impact on agriculture.

    And possibly also freshwater supply to much of the California coast, since that’s mostly through open-air aqueducts.

    And probably disrupt ground transportation along the I-5?

    So, while the L.A. sprawl and S.F. Bay area may have a fair amount not get outright flooded, they may loose their freshwater supply… Much of the nation looses a lot of agricultural production, and a good bit more population displacement, on top of other issues.

    I am so often reminded to be grateful that I never wanted, or had offspring :/ …

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