Some guy said it was, so there
The idea of ice sheets slowly melting and concomitant gradual sea level rise is not very frightening. The satellites suggest that the rate is accelerating, but the onshore gauges shrug their shoulders. Neither the accelerating rate of rise reported by the satellites, nor the slow and steady creep reported by the gauges are anything for modern civilization to fear.
What if I could suddenly trump that unexciting slow rise with something that would get Cnut scampering off the beach? Or at least, the threat of a sudden rise soon, let’s say by 2030? What if an entire glacier might slide off Antarctica like a kid on a toboggan and add, let’s say, half a metre to present sea level? Are you scared yet? Why not, dammit?
I think we should call this glacier the Doomsday Glacier, just in case anybody is still refusing to wet their bed about it. It does have an ordinary name too: Thwaites Glacier.
Fans of DC Comics will know that there is a supervillain in that fictional universe who is also called Doomsday. (You will also have fleetingly glimpsed him in the movie Batman v Superman: Dawn of Justice if you put yourself through that ordeal.) Doomsday has a very special power, which aficionados will know about but casual viewers of the recent film will not have picked up on. More on that in a moment. First let us focus on our real (harrumph) Doomsday.
As an aside, let me just say that the idea of advancing ice sheets has always seemed more frightening to me than retreating ice sheets. I suppose it depends where they are: if the ice sheet is near where you live, you would prefer it to roll back. If it is far away, and you live let’s say within a metre of Mean High-Water Springs, then you’d probably prefer to hear that the ice is rolling forwards. Not too fast though, because if it’s rolling forwards too fast it might slide off altogether.
Intermission: a selection box of headlines
Warmer oceans driving Antarctic Peninsula glacier melt, study says
New study reveals glaciers are rapidly melting
The East Antarctic glacier that has shrunk by 5 kilometres in 22 years
Glaciers in part of Antarctic thought to be stable suddenly melting at a massive rate say scientists
West Antarctic ice melt is now ‚unstoppable‘
Anyway, Thwaites. Now that you’re trembling, tremble some more, mortals, etc. Thwaites is scary because some time ago some scientists found that the floating bit of the ice sheet is perched on a ridge. The ridge – oh heck, let’s hear how the scientists themselves describe it:
Lamont-Doherty geophysicist Robin Bell, study co-author, compares the ridge in front of Thwaites to a person standing in a doorway, holding back a crowd. “Knowing the ridge is there lets us understand why the wide ice tongue that used to be in front of the glacier has broken up,” she said. “We can now predict when the last bit of floating ice will lift off the ridge. We expect more ice will come streaming out of the Thwaites Glacier when this happens.”Columbia.edu
The figure from Tinto & Bell shows the profile of Thwaites. The long nose is the ice shelf that is no longer in touch with the ridge. When did it lift clear? Some time between 1861 and 1956. Not, you might think, something to do with our emissions of CO2, etc:
At these rates, floating ice could have been grounded across the offshore ridge between 55 and 150 years ago.Tinto & Bell 2011, paragraph 24
With the nose clear of the ridge, and the couple of peaks that remain to pin it, Thwaites will flow faster. Too, the water seeping in from the ocean will be able to trickle down under the glacier, lubricating it so that it flows still faster. So the story goes.
Of course the excitement around Thwaites did not actually begin in 2011. It began around 1973 with Terry Hughes‘ article “Is the West Antarctic ice sheet disintegrating?” According to a computer realisation of Hughes‘ mathematical model (1981):
Future collapse of the West Antarctic ice sheet resulted from present surges of Thwaites and Pine Island Glaciers and was complete in only 200 years.Hughes 1981
Eric Rignot revisited the peril at the turn of the millennium. Thwaites was flowing faster, and in consequence, getting thinner. In fact you might as well say that ever since anybody looked at Thwaites in any detail, terror has abounded. But there is no doubt that as attention has grown, so has the peril. Perhaps there is too much science these days. In any case Antarctic scientists on Thwaites are now like wasps on jam.
Here are the search returns by decade (actually 11 year bins, since both start and end years end in 0s) for “Thwaites Glacier” (string in quotes) on Google Scholar.
|Time Period||Hits in Google Scholar|
These days there are enough glaciologists rolling around on Thwaites drunk on sugar that in the proper season it’s hard not to trip over them. (This is a lie, or at least a gross exaggeration.) Even journalists get to visit in order to (a cynic might think) raise the profile of the terror still more to keep the funding flowing. So it was that in the southern summer of 2019/20, the BBC’s intrepid Justin Rowlatt went on his own adventure to Thwaites.
Antarctica melting: Climate change and the journey to the ‚doomsday glacier ‘
Icefin [a submersible robot] has reached the point at which the warm ocean water meets the wall of ice at the front of the mighty Thwaites glacier – the point where this vast body of ice begins to melt.
In discussions of Thwaites Glacier, we often hear the phrase “warm water.” This conjures up an image of something Caribbean. Not something that would kill you in under a minute. How warm is warm?
„The deep Antarctic circumpolar water is only a handful of degrees warmer than the water above it – a degree or two above 0C – but that’s warm enough to light this glacier up,“ says David Holland, an oceanographer with New York University and one of the lead scientists at the grounding zone camp.
So that’s salty water at 2 degrees. The glacier is composed of fresh water and melts at 0. A blowtorch it ain’t.
The scientists say the Pacific Ocean is warming up and that is shifting wind patterns off the coast of West Antarctica, allowing the warm deep water to well up over the continental shelf.
Rowlatt’s BBC article blames the thermohaline circulation. We all know that there’s a transport of heat from warm regions of the Atlantic up north, which keeps the UK at a nice temperature, usually not too hot, and only rarely too cold (compare other places around the world at similar latitudes). The returning water does not, however, go directly to Thwaites. Instead it joins the circumpolar current that flows eastward. Thwaites is at about 105 W, which is opposite Baja California, not the Fram Strait. In fact the bit of the Antarctic opposite Greenwich is the Fimbul Ice Shelf. (Fimbulwinter, you might remember, is the three years of winter that heralds Ragnarok in Norse mythology.)
Anyway the key to the circumpolar current is the Drake Passage, without which there wouldn’t be a circumpolar current. Once the strait opened, Antarctica became isolated from the flow of heat from warmer climes, and a massive expansion of the ice sheet was initiated.
Thus you might be forgiven for thinking that a slowing of the circumpolar current would lead to melting ice in the Antarctic. However, a speeding up of the circumpolar current also leads to melting ice in the Antarctic. Perhaps we are in the Goldilocks zone at the moment: not too fast, and not too slow. (In fact it is said to be that the eddies in the current become more pronounced when the current speeds up: see image below – Thwaites is at about 9 o’clock.)
There’s been a sudden flurry of Thwaites news recently. More or less anytime a bunch of scientists go to Thwaites, they come back with new data telling everyone to be more afraid than we were before. Surely one day they will come back and say “actually, it’s not as bad as we thought.”
The latest terror is that of the windshield crack’d. Science:
The most dramatic sign of impending failure is a set of diagonal fractures that nearly span the entire shelf. Last month, satellites spotted accelerating movement of ice along the fractures, says Erin Pettit, a glaciologist at Oregon State University, Corvallis, who is part of a multiyear expedition studying the glacier. The shelf is a bit like a windshield with a series of slowly opening cracks, she says. “You’re like, I should get a new windshield. And one day, bang—there are a million other cracks there.”Science
[Sometimes I catch myself abusing the word “like” as well. I must not judge.]
How much is being spent on this multiyear expedition? Glad you asked. “…more than $50 million…”
Once the ice shelf shatters, large sections of the glacier now restrained by it are likely to speed up, says Ted Scambos, a glaciologist at the University of Colorado, Boulder, and a leader of the Thwaites expedition.Ibid.
In 2008 Scambos predicted that the Arctic Ocean would be ice free in summer by 2013. [So far, history records that it wasn’t.]
Oh, the title of the Science piece, dated 13 December 2021, is:
Ice shelf holding back keystone Antarctic glacier within years of failure
I like the word “keystone.” It is suggestive of an actual keystone, which when removed from the heart of a structure, causes the collapse of the whole.
Now, where did the name come from? Who had the audacity to christen this inert lump of ice, which has hitherto harmed no-one, and whose threats are seemingly speculative, the “Doomsday Glacier”? Why not call it something nice, like “Mr Tiddles”? For the answer to that, we have to look to Rolling Stone, and its contributor Jeff Goodell:
Great, thanks professor – we’ll take it from here. (By the way, Goodell also had the opportunity to trip to Thwaites, in 2019.)
The Rolling Stone article that quote was taken from has arguably jumped the shark, or whatever the appropriate equivalent is for colder climes. Picked up the penguin, perhaps. I mean, it’s only coming for those of us who live within half a metre of Mean High Water Springs, right? Folks like me who live at about 30 metres above sea level can still afford to snark about it.
I am very doubtful that anything bad will happen thanks to Thwaites in the near future, or by 2100 for that matter. The suggestion that any sea level rise due to Thwaites would be beyond what modern civilisation could cope with easily is absurd. (This may be argument from incredulity, so feel free to correct me.)
Now, to return to the real Doomsday, the real fictional Doomsday that is. His special supervillainous power was that, while he could be killed, he always came back to life. And every time he came back to life, he was immune to everything that had already killed him up to that point. Doomsday: a perennial favourite, and every time he comes back, it’s a definite case of „It’s worse than we thought.“
This is a shot from NASA’s Terra satellite taken on March 10 2021. The ice shelf is moving roughly towards the south west with the image as the reference frame. The position of the shelf in about 2010 is outlined in faint grey, & the considered „grounding line“, or „coastline“, at that date is in a darker grey. Oh yeh: the smooth ice is frozen sea water, the lumpy stuff is the shelf, some bits of which will have broken free previously.
The literature is available via Google Scholar as pdfs.
Hughes, T. J. (1981). The weak underbelly of the West Antarctic ice sheet. Journal of Glaciology, 27(97), 518-525.
Rignot, E. (2001). Evidence for rapid retreat and mass loss of Thwaites Glacier, West Antarctica. Journal of Glaciology, 47(157), 213-222.
Tinto, K. J., & Bell, R. E. (2011). Progressive unpinning of Thwaites Glacier from newly identified offshore ridge: Constraints from aerogravity. Geophysical Research Letters, 38(20).
via Climate Scepticism
January 5, 2022