[HN Gopher] What does the land under Antarctica's ice sheet look...
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What does the land under Antarctica's ice sheet look like?
Author : bryanrasmussen
Score : 160 points
Date : 2023-01-13 08:03 UTC (14 hours ago)
(HTM) web link (ubique.americangeo.org)
(TXT) w3m dump (ubique.americangeo.org)
| moloch-hai wrote:
| Antarctica probably looks a lot like much of Canada, Norway, and
| Chile.
|
| Scraped.
| petodo wrote:
| Quite odd article, when I click on picture to enlarge it, it
| opens completely different site and article from 3 years ago
|
| https://scitechdaily.com/high-precision-map-shows-what-the-l...
|
| Which I assume is using data from here
|
| https://nsidc.org/data/nsidc-0756/versions/3
| JorgeGT wrote:
| I think the old article (and thus the picture) is from the
| version 2 dataset, and now they have realeased version 3. I
| went ahead and rendered the version 3 dataset with QGIS:
| https://i.imgur.com/jj8B4D8.jpg
|
| Edit: without the underwater parts:
| https://i.imgur.com/tR67Nwq.jpg
| platz wrote:
| Why is there land at all at the south pole? Can't just be
| coincidence.
| NKosmatos wrote:
| Well, land is heavier than water so it drops to the bottom of
| the earth (South Pole) whereas there is nothing at the top of
| the earth (North Pole), just water and ice. (Joking obviously,
| I'm not a flat/hollow-earther or anything similar)
| jameshart wrote:
| But there's none at the North Pole.
|
| One pattern that is curiously consistent is that broadly land
| tends to be antipodal to ocean (and not just because there's
| more ocean in general - there's a genuine statistical skew) -
| so having land at one pole and none at the other matches that
| overall pattern. (https://www.geodatos.net/en/antipodes)
|
| Basically a surprisingly large proportion of antipodal pairs
| have land at one end and water at the other (although water-
| water is also common).
|
| In other words it would certainly be more surprising to have
| land at both poles; and we should be unsurprised if we find
| land at neither or land at one and not the other.
|
| So by that measure the poles are fairly typical of other
| antipodes.
| mFixman wrote:
| Is antipodal land a physical property of Earth's continents,
| or is it mathematical fact of distribution on spheres?
|
| If we distribute chunks of land randomly on a sphere we would
| expect roughly the same amount of land on any randomly-chosen
| hemisphere. But what can we say about the average amount of
| land in the hemisphere with the most land?
|
| My intuition says that in an Earth-like sphere, with 29% land
| and 71% water, there's a high chance of there existing a
| hemisphere with almost all of the land.
|
| I have no idea how to prove this empirically, but it seems
| like a really nice maths problem.
| s1artibartfast wrote:
| My understanding is that it is a physical property, arising
| from the fact that crustal basically all crustal growth
| occurs in ocean floors .
|
| The locations of the continents spend the vast majority of
| the time either approaching a clustered state, or leaving
| it.
|
| Because the thick continents with land are a minority of
| the surface [2], They only briefly pass through a period of
| even dispersal when passing from one clustered state to
| another.
|
| >My intuition says that in an Earth-like sphere, with 29%
| land and 71% water, there's a high chance of there existing
| a hemisphere with almost all of the land
|
| Can you explain more? If you have 7 or so plates with land,
| why would you expect them to have a high chance of being in
| the same hemisphere? The math is the same as flipping a
| coin 7 times. Flip the first and see which side it lands
| on, then flip the remaining 6 and see how many match the
| same hemisphere. What am I missing?
|
| https://www.youtube.com/watch?v=gQqQhZp4uG8
|
| https://www.imperial.ac.uk/news/199334/scientists-find-
| link-...
| mFixman wrote:
| > The math is the same as flipping a coin 7 times [...]
|
| I'm not saying that a particular hemisphere has a high
| change of having most of the land; I'm saying that there
| will be a hemisphere that has this chance.
|
| 29% of Earth is land and 80% of this land is in the land
| hemisphere, so this problem would be the equivalent of
| rolling a D48 14 times and placing the dice on a table so
| that any 11 of the rolled numbers are visible if I look
| at it from the top.
| s1artibartfast wrote:
| I see, so if you have the freedom to define hemispheres
| however you want, what are the chances you can fit a
| definition that captures the majority.
|
| I think that is also fairly solvable. let me think on it.
| I cant understand your example, but is this the same?:
|
| Roll a d100 once per continent (e.g. 7 times) and write
| the numbers down. What percent of the time can you pick a
| range 50 numbers that captures all 7 results. the range
| can wrap around from 100 to 0.
|
| The problem would be easy to monte carlo, but I would
| have to think about how to solve it in closed form.
|
| Will update if I have a solution.
| mFixman wrote:
| Your example is not the same for two reasons: 1. You are
| assuming there always are 7 continents and each of them
| contains 1% of all space on the Earth's surface. I assume
| there are 14 continents with 2% of the Earth's surface
| each, which is still incorrect but it's closer to
| reality. 2. I'm not defining hemisphere however I want:
| I'm using the canonical definition of hemisphere, but
| choosing any hemisphere for me dice. For example, two
| continents that appear on numbers 1 and 48 can never be
| in the same hemisphere.
|
| My question is the probability of being able to choose 11
| of the 14 continents so that there exists a hemisphere
| that contains all of them, like the land hemisphere
| contains 80% of the Earth's land.
| s1artibartfast wrote:
| Thats interesting. A few questions:
|
| 1)When you say you are using the canonical definition of
| hemisphere, do you mean North and South? Or are you
| talking about East and West as well?
|
| 2) Out of curiosity, why 14 continents?
|
| If you are using North and South as pre-defined
| hemispheres, ignoring East and West, I do think it can be
| reduced down to a coin flip if you want to prove that
| plates are _unlikely_ to almost all be in the same
| hemisphere. This is because allowing them to overlap
| allows _more_ clustering, not less.
|
| 12/14 continents is >80% and 11/14 is <80%.
|
| If you drop a continent randomly, it has a 50/50 chance
| of being in the north or south.
|
| The probability of 12 or more being in the northern
| hemisphere is 0.647%. The probability of 12 or more being
| in the southern hemisphere is 0.647%. Together, the
| probability of 12 or more being in the same N/S
| hemisphere is 1.294%
|
| You can do the same for E and W, getting another 1.294%,
| for a total of 2.588% chance. This is allowing the
| continents to overlap, so the real chance would be
| _lower_.
| mFixman wrote:
| The Northern, Southern, Eastern, and Western Hemispheres
| are just four of the infinite hemispheres of a sphere.
|
| By "canonical definition of hemisphere" I'm talking about
| the surface of any half-sphere that covers half of the
| Earth; the "joke" in my proof is that you can choose any
| one.
|
| For any two continents there's always a hemisphere that
| contains both of them (assuming you don't worry about the
| semicircle in the border of the hemisphere). If you put
| three equidistant continents with the maximum possible
| distance between them (so that they form an equilateral
| triangle whose centre is the centre of the sphere) then
| you can't do anything about it.
|
| Think it like shining a light from some point in space
| that lights 80% of the land in Earth.
| s1artibartfast wrote:
| I see, that joke went over my head.
|
| That is what I initially meant by having "freedom to
| define hemispheres however you want", eg set arbitrary
| centers.
|
| That certainly makes it a more interesting problem and
| increases the chances substantially.
| treeman79 wrote:
| Take it account dice rolling in a small fixed area where
| they tend to get stuck together?
| jameshart wrote:
| It also depends on how strongly clustered the land tends to
| be - if the land is all going to be continuous then
| presumably there are more distributions of that land that
| are weighted towards a single hemisphere.
|
| Suspect there's something to do with the fractal dimension
| of the coastlines as well. Agreed - sounds like a rich vein
| of math.
| gorgoiler wrote:
| The North Pole isn't far off being land. A lot of the Arctic
| Sea is only slightly underwater.
|
| https://commons.m.wikimedia.org/wiki/File:IBCAO_betamap.jpg
| SketchySeaBeast wrote:
| To me that really looks like pattern matching where there
| isn't actually any (though I'd like to know more details
| around the "statistical skew")- saying that there's a lot of
| antipodal land-water or water-water pairs only makes sense
| considering the vast majority of the planet is water.
|
| Regardless, it's just an interesting snapshot in time
| considering continental drift.
| jameshart wrote:
| 30% of the surface is land. But only 15% of land has land
| antipodal to it, which certainly initially feels like less
| than you would expect by random chance.
|
| It's easy to fall into some counterintuitive fallacies
| reasoning about this though because we're considering a
| spherical surface pairwise and you might be tempted to say
| 'ah, but we're counting the antipodal land twice so that
| probably accounts for the 15%/30% thing' - but I don't
| think that follows; that 15% with land antipodal to it can
| be thought of as two sets of 7.5% of the land, which are
| antipodal to one another - the 'double counting' doesn't
| work that way to eliminate the anomaly.
| SketchySeaBeast wrote:
| Just for curiosities sake I fell down the rabbit hole and
| ran the numbers (please someone correct me if I'm wrong
| on this - it's been a loooooong time since I did
| statistics). This is all assuming some sort of even
| distribution of land/water, so the numbers don't reflect
| real world continental distribution, but I don't know how
| to account for that.
|
| We have a 30% chance of picking a random point on Earth
| and getting land. Because earth is so big and these
| theoretical points are so small I'm going to assume that
| one point of land existing doesn't effect the odds of
| another piece of land existing. So that's two antipodal
| points, each with a 30% chance of being land.
|
| Putting that into a probability calculator (again, long
| time since statistics) that gives us odds of both point A
| & B being land as 9%. If we flip that around and go with
| the 30% land and 70% water odds we end up with a chance
| of 21%. It seems like there's actually MORE land that's
| antipodal to other land than we'd expect statistically? I
| must have some bad math here.
| jameshart wrote:
| (Edit - I misread my own math here)
|
| Not sure where 21% comes from - if 3/10 of points are on
| land, 9/100 antipode-pairs should be land-land, and that
| means 9/100 / 30/100 = 9/30 = 30% of land should have
| land opposite it, and conversely 70% should have water?
|
| But the true numbers are 15%/85% - on the actual earth,
| land is more likely to have ocean opposite it than random
| chance would suggest.
|
| Analyzing whether items sufficiently far from the
| 'expected' random distribution as to be statistically
| significant is a rather different exercise though.
| [deleted]
| addaon wrote:
| > We have a 30% chance of picking a random point on Earth
| and getting land. Because earth is so big and these
| theoretical points are so small I'm going to assume that
| one point of land existing doesn't effect the odds of
| another piece of land existing.
|
| This is the issue.
|
| A large contributor of the "point antipodal to land is
| water" anomaly is the typical size of land masses. If,
| for example, the average size of land masses was 30% of
| earth's area, then we'd have a single large land mass
| (Pangaea style), and all antipodal points would be water.
|
| The approximation of independence here doesn't reflect
| reality. Eurasia alone is more than 10% of the land area
| of Earth.
| vl wrote:
| If you look at the Pacific Ocean from "top" (i.e. get a
| globe and rotate it), you'll see that it effectively
| covers almost entire hemisphere. So there is no surprise
| that most of the land has no antipodal land. The more
| interesting question is why initial continent, Pangea
| existed as such instead of the bunch of the smaller
| continents, which would seem more logical and likely.
|
| EDIT: also, do we know if there were no other continents
| that submerged?
| joshuaheard wrote:
| Coincidentally, I just watched a TEDx video, "The Hidden World
| Beneath the Antarctic Ice Sheet", by John Priscu, who is really
| an amazing scientist.
|
| https://www.youtube.com/watch?v=mTwS9_PReM4
| [deleted]
| markus_zhang wrote:
| Antarctica has always fascinated me since my reading of HPL's _At
| the Mountains of Madness_.
| rintakumpu wrote:
| I immediately thought of that story as I saw the map! Sad the
| del Toro movie never got made.
| xwdv wrote:
| Antarctica looks like a very interesting land, perhaps because it
| is forbidden to us. Still, with that geography alone I wish we
| could swap its place with something like Australia. Perhaps with
| advanced geo-engineering it would be possible to someday rotate
| the earth in such a way that Australia ends up at the South Pole
| and Antarctica is uplifted to a warmer climate.
| barryvan wrote:
| I think the Australians might have a few objections to that
| proposal... As one of them, I know I do at least!
|
| It is interesting how much more archipelago-like Antarctica is.
| I wonder if that would mean fewer interior deserts than a large
| continent like Australia has
| nirimda wrote:
| > I think the Australians might have a few objections to that
| proposal... As one of them, I know I do at least!
|
| Well, Australia claims about half of Antarctica so as long as
| we can enforce that claim maybe it's not the end of the
| country. Just have to declare part of it "New Southern New
| South Wales" and take it from there.
|
| > I wonder if that would mean fewer interior deserts than a
| large continent like Australia has.
|
| There Arabian pensinsula are the Sahara are surrounded on
| three sides by sea, but they're still very dry. The Sahara
| and Arabian deserts go right up to the coast. As mentioned in
| my reply to your other reply, as far as I know it's not a
| lack of water but what happens to the water once it's
| evaporated that causes the dryness in those areas - it goes
| up into the high atmosphere and comes down in rain over the
| tropics. Wish I remembered the name though.
| someNameIG wrote:
| > Well, Australia claims about half of Antarctica so as
| long as we can enforce that claim maybe it's not the end of
| the country.
|
| I have always wondered how this would turn out. Currently
| not many other countries recognise our claims, but so far
| there's been no reason to enforce them. Given out proximity
| we are in a good position to enforce them, and the likes of
| BHP and Rio Tinto would love access to all the possible
| resources.
| valarauko wrote:
| > as far as I know it's not a lack of water but what
| happens to the water once it's evaporated that causes the
| dryness in those areas - it goes up into the high
| atmosphere and comes down in rain over the tropics. Wish I
| remembered the name though.
|
| It's the other way around - the subtropical ridges are high
| pressure high altitude masses of dry air that fall to the
| surface around 30 N & S. This dry air is then sucked back
| to the equator as the Trade Winds, which further dry out
| the sub tropics.
|
| > Wish I remembered the name though.
|
| Hadley cell?
| seanmcdirmid wrote:
| Doesn't Antarctica technically have the largest deserts in
| the world?
| nirimda wrote:
| Only because it's at the south pole. If we tilted the earth
| a bit, it would warm up and start raining. But if we tilted
| the earth a bit, Australia could probably also get wetter.
| As far as I understand it, the dryness of Australia, the
| Sahara etc are caused by the particular location from the
| equator, where moist air is lifted and brought to the
| equator and dumped there as rain. So if we pushed Australia
| further from the equator it would get a bit damper and
| maybe Indonesia would dry out.
|
| I recommend we don't adopt this program of rotating the
| earth. It's almost certainly worse than just inventing
| fission power and pumping desalinated sea water to wherever
| we want to de-desertify. We'd probably also be better off
| if we wasted quintillions of dollaeuroyuans on a program to
| terraform Mars that ends in complete failure and the deaths
| of millions of workers over a century, but that's also an
| outcome I recommend we avoid.
| qikInNdOutReply wrote:
| The evidence does not seem to follow this logic.
|
| There are lots of countries closer to the equator - they
| are wetter.. large body masses have continental clima,
| which enocourages the growth of dessert, but they usually
| do so only when the war of forrest vs savannah is lost by
| the forrest. Which can cling to areas quiet defiantly,
| for example the last big forrests in syria, that once
| covered the middle east
| jeddy3 wrote:
| To be fair, they said particular location _from_ the
| equator.
|
| Does not have to mean close to the equator.
| swader999 wrote:
| A celestial collision would probably be the only thing that
| could do that. The nimby crowd would also be an issue.
| [deleted]
| EdwardDiego wrote:
| That Denham canyon is interesting AF.
| idoh wrote:
| Time to demote Antarctica to an archipelago? (And join Pluto on
| the geographic name B-team)
| usrusr wrote:
| I believe that the term you were looking for was toponymy,
| avoids the awkwardness of "geography, but off-earth": and join
| Pluto on the toponymic B-team.
| schrodinger wrote:
| How long have you been waiting to find a use for that word?
| :)
| roamerz wrote:
| When the ice melts we will probably find an remnants of an
| advanced civilization. Through some of the preserved records we
| will see that they were trying there best to ban solar and wind
| and rid the earth of electric cars so as to ward off global
| cooling.
| s1artibartfast wrote:
| For those who enjoy geography and tectonics, I suggest the this
| article, with many more detailed maps of the antarctic plate.
|
| http://www.seismolab.org/model/antarctica/lithosphere/index....
| Gravityloss wrote:
| I'm always amazed at the science we can do. We can measure
| gravity with satellite constellations so precisely, we can
| estimate surface features from that. We have ice penetrating
| radar. We measure glacier velocity. Dive under glaciers.
|
| And yet I'm saddened by the huge waste of it all, as this can be
| brushed away by one "charismatic" speaker that enough masses will
| follow. Voters will not want to do anything. People burn their
| gas stoves out of spite.
| hackerman123469 wrote:
| I wonder if the locations researchers are staying at are located
| on top of the land or if it's just randomly located and could be
| either. Like if all (or a majority of) the ice melted how big of
| an impact would it have on the locations?
| frogulis wrote:
| McMurdo station (the biggest one) is standing on land and does
| thaw in summer [1]. That's on an island at the outskirts of
| Antarctica though, so I don't imagine it's representative of
| stations elsewhere on the continent.
|
| [1] https://brr.fyi/posts/mud-murdo
| ErikCorry wrote:
| What about the actual South Pole? Looks like it might be over
| water.
| jl6 wrote:
| Note that this isn't necessarily what the continent would look
| like if all the ice melts.
|
| The lack of ice weight would allow the land to rebound upwards:
|
| https://polarjournal.ch/en/2022/07/13/what-greenland-and-ant...
| cwmma wrote:
| I mean it's what the content would look like for a long time,
| Scandinavia is still not done rising from the last glacial
| period.
| telesilla wrote:
| Are there earthquakes or other events that are recognized on
| a human scale?
| Zash wrote:
| Yes, small ones. http://www.snsn.se/map_right.html lists
| earthquakes in Sweden the last year.
| kevin_thibedeau wrote:
| Yes. The entire northern lattitudes have quakes (typically
| mag 1-3) from ongoing post-glaciation uplift.
| throw827474737 wrote:
| We will see soon! (:
| rr888 wrote:
| Also Greenland and Antartica have so much ice it produces a
| gravitational pull on the surrounding water. Its one of the
| reasons sea levels rise in most of the world when that gravity
| weakens and water is redistributed.
| placebo wrote:
| Also, what is the relative sea level for this map - is it the
| same as the current one or what it will be like after the ice
| melts
| cwmma wrote:
| if all the ice in antarctic melted (and nothing else
| happened), it would cause sea levels in antarctic to fall.
| That's because all the ice currently there exerts enough of a
| gravitation pull to increase sea levels there now. That being
| said there would be other things like the melting of the
| Greenland ice sheet and thermal expansion of the oceans that
| would be acting to increase the sea level.
| 0xbadcafebee wrote:
| It's gonna be interesting when the poles melt and the major
| powers war over who gets the land
| heavyset_go wrote:
| And the new sea routes in the North.
| sacrosancty wrote:
| [dead]
| Tepix wrote:
| Are there any interesting sci-fi novels or games that take place
| in the (far) future in Antarctica with humanity being forced away
| from the equator by the increasing temperatures?
| thorin wrote:
| It's obviously incredibly dated now, but I used to absolutely
| love this game on the Amiga in the 90s - Midwinter
|
| [1] https://en.wikipedia.org/wiki/Midwinter_(video_game)
| jameshart wrote:
| _Midwinter_ and _Flames of Freedom_ were _so far_ ahead of
| their time. It's like Mike Singleton had a vision from the
| future of _Just Cause_ or _Far Cry_ or something and tried to
| build it using 90s technology.
| totetsu wrote:
| Wow it's fascinating to see what games could be imagined in
| the era before all the genres were decided upon. Action rpg
| with strategy elements.
| perhonen wrote:
| It doesn't take place in Antarctica, but The Drowned World by
| J.G. Ballard describes such a future - the last remnants of
| civilization have retreated to Greenland, and London is a
| flooded tropical lagoon.
| PopAlongKid wrote:
| Yes, _A World Out Of Time_ by Larry Niven.
|
| " _Almost all remaining life on Earth has adapted to live in
| Antarctica. Elsewhere life is extinct except for some evidence
| of biological activity in the Himalayan mountains._ "
|
| https://en.wikipedia.org/wiki/A_World_Out_of_Time
| rgarciah wrote:
| "Antarctica" by Kim Stanley Robinson. Near future, but
| excellent prose and narrative.
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