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Why Our Intuition About Sea-Level Rise Is Wrong
- air7 6y agoI love counter-intuitive facts. They are a helpful reminder that things are more complicated than I think they are, and I don't understand the world as well I think I do. "Gravity has a very strong effect. So what happens when an ice sheet melts is sea level falls in the vicinity of the melting ice sheet. That is counterintuitive. The question is, how far from the ice sheet do you have to go before the effects of diminished gravity and uplifting crust are small enough that you start to raise sea level? That’s also counterintuitive. It’s 2,000 kilometers away from the ice sheet. "
- seesawtron 6y agoAlso Simpson's paradox is so counterintutive. [0] [0] https://en.wikipedia.org/wiki/Simpson%27s_paradox#UC_Berkeley_gender_bias https://en.wikipedia.org/wiki/Simpson%27s_paradox#UC_Berkele...
- barking 6y agoYes, it sure is, took me a while to get it. I don't have any paradoxes but here are my two favourite surprising facts. 1: NY city on the East coast of N. America lies further west than Santiago the capital of Chile on the West coast of S. America 2: The Atlantic opening of the Panama canal lies further west than the Pacific opening.
- VBprogrammer 6y agoOne that always surprises me, Edmonton (Canada's most northern city) is about the same latitude as Manchester in the UK.
- barking 6y agoOr that the most northerly French-speaking town in the world is Dunkirk in France and not somewhere in Quebec.
- arethuza 6y agoI did wonder about Belgium but it looks like most of Belgium (and all of the French speaking parts) are further south than Dunkirk.
- jwilliamson 6y agoThis is not true. The town of Radisson was built in the 70s during work on the James Bay Project and is still mainly francophone. It's about 2° north of Dunkirk. https://en.wikipedia.org/wiki/Radisson,_Quebec https://en.wikipedia.org/wiki/Radisson,_Quebec
- barking 6y agoInteresting but I'm not sure I'm buying it ;-) Radisson is a small unconstituted locality so whether it qualifies as a town is questionable. It also has a population small enough to fit in two or three buses.
- nkurz 6y agoHow about Fermont in Quebec, then? http://www.toponymie.gouv.qc.ca/ct/ToposWeb/fiche.aspx?no_seq=22297 http://www.toponymie.gouv.qc.ca/ct/ToposWeb/fiche.aspx?no_se... It is predominantly French speaking, is 1° further north than Dunkirk, is incorporated as Ville de Fermont, has a population of about 2400. It also has a Wikipedia page that claims "Fermont is arguably the world's northernmost Francophone settlement of any considerable size": https://en.wikipedia.org/wiki/Fermont https://en.wikipedia.org/wiki/Fermont.
- barking 6y agoIt's much cooler that Dunkirk should hold this distinction, isn't it, so can we agree please that these rather undistinguished places in Canada don't count? Anyway Dunkirk is a proper town/city (91K people, interesting history) not like this awful sounding place where everyone lives in a single building because it's like the moon there or something.
- wdobbels 6y agoWe should rename North-America to North-West-America and South-America to South-East-America.
- lt 6y agoI opened google maps to check #2 and stared for a while trying to understand what you meant... Then I zoomed out!
- antognini 6y agoA few more: * The US state closest to Africa is Maine. * New York City is south of Rome. * Los Angeles, California is east of Reno, Nevada.
- divbzero 6y agoWhoa! That’s cool. Another one (somewhat more obvious) is that the southernmost point in the USA is on the Big Island of Hawaii.
- CrazyStat 6y agoMy favorite example of Simpson's paradox: On average, in the United States, houses without central AC cost more than houses with central AC. When you break it down by state it turns out this is almost entirely due to lots of expensive houses without central AC in California. In every single state houses with central AC are more expensive than houses without, but California with its high real estate prices and temperate climate skews the national averages.
- codecamper 6y agoGood article. I was hoping that he would talk about the effect on tectonic plate stability with these massive bodies of weight shifting around a spinning sphere.
- Super_Jambo 6y agoDoes the North America plate losing Greenland's ice increase earthquake risk on the west coast then? Intuitively seems like it should... But then this is an article about how bad intuition is for complex problems.
- rshnotsecure 6y agoThis is actually very concerning. We have significant evidence now to suggest that asteroids in the past have caused large earthquakes. Sometimes on the other side of the impact zone (the antipode). More scary though is what comets can do. They have a highly elliptical orbit, so they are much harder to spot than asteroids as they come out of nowhere. The elliptical orbit gives them much greater speed to. Comets tends to generate enormous levels of heat too, they explode shorty before impact as one did in Tunguska in Russia in 1908. Anyway it now seems that these "bursts" have happened during ice ages, vaporizing massive ice sheets. We are talking perhaps the entire northern hemisphere in some cases like the Younger Dryas Impact Hypothesis. The crust floats like water and is as gooey as pudding when suddenly trillions of tons of weight just "disappears" above it. We have no idea how this unfolds currently except to say it is destructive and chaotic at the least.
- arethuza 6y agoWe do have some idea what happens - post-glacial rebound is very noticeable in some parts of the world that were heavily glaciated in the last ice age: https://en.wikipedia.org/wiki/Post-glacial_rebound https://en.wikipedia.org/wiki/Post-glacial_rebound
- rshnotsecure 6y agoJust saw this. Fascinating.
- strogonoff 6y agoThe illustration seems misleading—showing increase in sea level starting right outside of a glacier. As discussed in the article, the area of diminishing sea level spans thousands of kilometers far from where a glacier used to be, depending on its mass. The person interviewed claims that people usually don’t appreciate his points since they’re so counter-intuitive, well right there we have Nautilus not helping that at all.
- mikro2nd 6y agoMitrovica has some videos on YT that probably do a better job of explaining.
- fritzo 6y agoAs I understand it is gravity's inverse square law that makes the effect strongest closet to the glacier and tapering off over a couple thousand kilometers.
- strogonoff 6y agoMy understanding as well. The image, though, doesn't convey sea level dipping for many kilometers around former glacier edge and rising only further away (possibly in another hemisphere entirely)—instead it shows sea level rising immediately at the edge, which doesn't seem to track.
- dangirsh 6y agoI think the image is trying to convey that there's a rising immediately near the glacier due to the tectonic plate lifting up. Then there's a falling due to reduced gravitation. What's not shown would be (much further away) a rising due to increased water volume. I agree that the image is a bit confusing.
- strogonoff 6y agoI think the green line is the sea level after the melting, since it is labeled Final Sea Level. It does not show a fall, only a rise, next to the glacier.
- jessaustin 6y agoI recall Augustus reigned on the order of 2000 years ago, not 2500? Normally this would be a trivial detail, but the calculations under discussion would seem to require exacting precision. I suspect this is an error on the reporter's part, so it's good that Nautilus is online and can update its articles.
- keiferski 6y agoI wouldn't call it trivial at all; 500 years is the difference between the Renaissance and present day. 2500 years ago, Rome had just become a republic, while 2000 years ago (during Augustus' time) it became an empire and would soon reach its territorial peak.
- jaspax 6y agoWait. My intuition says that the mass of ice cannot possibly have a gravitational influence on nearby water big enough to create the effects described. Back of envelope calculation: surface area of Antarctica is on the order of 10M km^2, with an average thickness of 1 km (a high estimate), means 10M km^3 of ice; some further calculations from volume to mass multiply out to 10^19 kg of ice. (Note that we're assuming that 1kg of ice is 1 cubic deciliter, as with liquid water; this is definitely wrong but let's go with it since this is just an order-of-magnitude estimate). The mass of the Earth is on the order of 10^24 kg, so this is 10^-5 of the mass of the earth. Can you get really get 50m of local displacement from 10^-5 Earth masses?
- _petronius 6y agoThe force vector from a polar ice sheet doesn't get cancelled out by the rest of the earth though (because they aren't pointing in opposite directions). Plus, you have to account for the force of the ice sheet, plus the water it attracts, plus the water that those combined attract, etc. I'm no good with calculus so can't run that back-of-the-envelope for you, but it doesn't seem all that surprising to me.
- jfindley 6y agoEven if we ignore all that, and treat everything as a point mass, it's still believable, I think. The earths radius is very approximately 6.4km. So 1km out from the ice sheet, we have 1(1/6.4^2) (earth) vs 10^-5(1/1^2) (ice), which is very roughly 1/2500th of the effect of earths gravity. But the earths gravity is strong! The forces it exerts on the ocean are titanic - it doesn't seem outside the realms of belief that even this small percentage of the force could produce an observable effect, when the forces are so huge, and the differences are only measured in meters. I think part of the reason we find this difficult to grasp intuitively is we don't really have a good mental model of just how titanic many of these forces are - huge numbers are just not something we, as a species, are good at understanding.
- silvestrov 6y agoEarth’s radius is 6371 km, not ~6 km.
- Proven 6y agoMy intuition in the 90's was that it won't matter to me, and it's been 100% right.
- barbegal 6y agoIf you want to get a better feel for this NASA has made a great visualization tool https://vesl.jpl.nasa.gov/sea-level/slr-gfm/ https://vesl.jpl.nasa.gov/sea-level/slr-gfm/
- rshnotsecure 6y agoThis article is bizarre. Some quotes that strikes me as just really really odd: "Jerry Mitrovica has been overturning accepted wisdom for decades" - no one is this good. "What he calls postmodern geology" - this is very concerning. Postmodernism is like Foucault and Derrida and about power and society. Foucault is actually the most cited academic of all time statistically, so for a Professor to knowingly use this word to describe the science of geology is just strange. "Though a practiced public speaker" - what is this? should he be ashamed? "These are known as sea-level fingerprints, because each ice sheet has its own geometry. Greenland produces one geometry of sea level change and the Antarctic has its own. Mountain glaciers have their own fingerprint." - what?
- praveen9920 6y agoThe interview is nicely done. The followup questions were exactly what I would have asked, probably to explain the theory to someone who doesn't know much about geology
- mrfusion 6y agoI’m trying to get as many people out to see Florida one last time before it’s underwater.
- supremeWhite 6y agoSo does that mean that the rising sea levels predicted as a consequence of global warming were wrong?
- kryogen1c 6y agothis article doesnt do much to dispel the counterintuitive nature of the subject. 1) the mass of glacier sheets have gravity, so sea level is higher near glaciers 2) the weight of the glacier on the land its sitting on pushes the land into the water and raises sea level 3) when glaciers melt, they add water to the sea. however, the melting glacier removes gravitational mass and removes weight that was forcing the land it was sitting on into the water. the combination of these 3 effects is lowering the nearby sea level and raising the faraway sea level 4) the distance that makes a given spot nearby or faraway is dependent on the glacier sheet itself - how massive it is, its geometry, etc. the all-in, 3 dimensional accounting of where on the globe sea levels change for a given glacier melting is called its fingerprint. the article claims that the major glacier fingerprints are unique such that global sea level data points can identify, simultaneously, what percentage of all glaciers are melting. on a side note: the provided infographic is wrong - the yellow and green lines are touching at the edge of the glacier. its attempting to model pretty pictures in 3d with 2d lines, and its just not accurate. it sort of conveys the point, i guess, if you just squint and dont think about it.
- ppod 6y agoThe problem I have with this stuff is that I just can't imagine how bad it could possibly be if sea levels rose even three meters over the next hundred years.
- gbear605 6y agoSignificant fractions of many coastal cities are under 3m above sea level. Even if they could put up walls, many seaside communities are also under 3m.
- greendave 6y ago> What do Roman fish tanks tell us about sea levels? This article has many such gems. Fascinating and well-written. (Note that it was originally published in 2016).
- puranjay 6y agoMore on Roman fish tanks if anyone wants to read about this topic. I thought this was very insightful: https://www.harvardmagazine.com/2016/08/what-roman-ruins-reveal https://www.harvardmagazine.com/2016/08/what-roman-ruins-rev...
- mgamache 6y agoAll the discussion about gravity is good, but I was equally interested in the slowing of the earth's rotation. 1.8ms per day? It seems like that's large enough to be noticed with modern clocks/astronomy outside of eclipse records. Is this confirmed outside of eclipse records?
- CabSauce 6y agoYes. That's why we have leap seconds.
- mgamache 6y agoI thought that was just to correct for the initial definition of a second which was inaccurate. But, it looks like it is the reason for leap seconds: https://www.timeanddate.com/time/leap-seconds-background.html#:~:text=Leap%20seconds%20are%20added%20to,slowing%20of%20the%20Earth's%20rotation https://www.timeanddate.com/time/leap-seconds-background.htm....
- jandrese 6y agoLeap seconds can be affected by things like big volcanic eruptions and earthquakes. That's why they are defined "as needed" instead of at regular intervals, and why they are applied somewhat irregularly.
- vharuck 6y agoThis struck me, too. So days were 4 hours shorter 2500 years ago? The evidence our ancestors worked fewer hours a day just keeps piling up [0]! [0] https://news.ycombinator.com/item?id=16656903 https://news.ycombinator.com/item?id=16656903
- jaycroft 6y agoPerhaps I'm missing some sarcasm, but the article states that two clocks, one synchronized to the earth's rotation, and the other keeping atomic time, they would drift by a total of 4 hours over 2500 years, not drift by 4 hours per day. Those are completely different things.
- charliebrownau 6y agoYet to see a single bit of TRUTH come from the GLOBAL LEFT over 20 years Everything is the opposite its all fucking lies
- mentos 6y ago>If humans weren’t warming the climate, Earth might be poised to enter into another Ice Age in the future. Is there a chance it is beneficial to keep the next ice age at bay?
- trynumber9 6y agoThe agricultural regions of Europe and North America not being covered with sheets of ice may be a positive. Especially if you like having food.
- mberning 6y agoHistorically ice ages have not been very good for humanity.
- fsckboy 6y agoThe idea is interesting and I'm glad to know about it, but there is a glaring flaw in his reasoning which nobody else here has commented on so I'll do it: "I was in Holland a few summers ago and was trying to convince the Dutch that if the Greenland ice sheet melts, they have less to worry about than the Antarctic ice sheet melting. But it doesn’t register." because, is there a polar melting hypothesis that melts the Arctic without melting the Antarctic? It could be that his idea is that both poles have water stacked up from ice sheet gravity more than it would be than melted, but the reasoning in that quote doesn't make that point, it makes a different point that is not useful, and he is I guess saying that there would just be more flooding than expected near the equator?
- eximius 6y agoIce is less dense than water. Why would ice's gravity be more influential than the waters?
- frank2 6y agoBecause when the ice melts, the water does not remain where the ice was, but rather enters the ocean. Water entering the ocean anywhere in the world will tend to raise the height of the ocean worldwide.
- BeKindAndLearn 6y agoGravity pulls on both objects. The water (along with the rest of the planet) pulls the ice down, the ice pulls the water up.
- mcguire 6y ago"What do Roman fish tanks tell us about sea levels? "Wealthy Romans at the time of Augustus were building fish holding tanks. The fishermen would come in with the fish, they’d put them there so that the fish were fresh when they ate them—they wanted to keep them alive for a few days or weeks or whatever. The Romans were engineers, so they built these fish tanks at very precise levels relative to sea level at the time. You didn’t want the walls to be too low because at high tide the fish would swim out; you didn’t want it to be too high because you wanted tides to refresh the water within the tanks. "Kurt Lambeck, a professor at the Australian National University, recognized that by looking at the present day elevation of those fish tanks, we could say something about how sea level had changed over the 2,500 years since then. If sea level over the last 2,500 years was going up at the rate that it went up in the 20th century, those fish tanks would be under 4 meters of water—12 feet of water—and I can assure you they’re not. You can see them. You can walk along the coast, they’re visible. What that tells you is that it is impossible that sea level went up by the rates that we saw in the 20th century for any extended period of time earlier than that. Sea level has not gone up over the last 2,500 years like it has in the 20th century." Italy is tectonically active. The level of 2000 year old Roman constructions versus the sea may well have more to do with local ground rise or fall. This assertion needs significant supporting data.
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- arnoooooo 6y agoI thought the main contributor to the rise was the thermal expansion of water as it heats up. I don't see a single mention of this in the article ?