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What does the land under Antarctica’s ice sheet look like?

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Re: What does the land under Antarctica’s ice sheet look like?

#71

Post by crazygringo »

jl6 wrote: post #5

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...

Thank you! I was wondering why it looked so different from any other landmass, with the land being so much "sparser".

The end of the 7-second animated video on your link shows a landmass that looks much more like the rest of the Earth.

Utterly fascinating to see a "hidden continent" like this -- I'm so used to unfamiliar maps being fantasy (like Westeros from Game of Thrones), so it's quite remarkable to see an unfamiliar map that is on our very planet.

Re: What does the land under Antarctica’s ice sheet look like?

#72

Post by joshvm »

ErikCorry wrote: post #69
hackerman123469 wrote: post #4

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?

What about the actual South Pole? Looks like it might be over water.

The South Pole is also over bedrock, around 3 miles down. See "glaciology" here: https://icecube.wisc.edu/science/research/

Scientific implications would be IceCube would no longer work, because the premise is based on the detector(s) being drilled 2 km into the glacier. You can't just bury it in rock, it specifically needs a transparent medium and ice is surprisingly good for neutrino propagation. The other telescopes would probably be fine, provided it was still sufficiently dry. SPT and BICEP are mostly taking advantage of the location - e.g. high altitude, extremely low humidity and extremely radio quiet, to a lesser extent the ability to stare at the same patch of sky all year. I guess you'd lose a lot of the environmental advantages, but maybe it would still be a desert.

There isn't a particularly good reason why everything is sited there beyond geopolitics. You could pick pretty much any place on the polar plateau and it would be fine. We just happened to luck out at how suitable the ice was for certain experiments.

The station is on a moving/shearing ice sheet though, which has some minor implications (like the relative position of the pole changes, so we have to move the marker each year by about 10 m).

https://svs.gsfc.nasa.gov/4060

Re: What does the land under Antarctica’s ice sheet look like?

#73

Post by late2part »

sanj wrote: post #70
rr888 wrote: post #65

Earlier quoted context omitted.

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.

Do you have a link to an article explaining this?

The math is trivial to explain this (in theory).

Re: What does the land under Antarctica’s ice sheet look like?

#74

Post by gus_massa »

rr888 wrote: post #65
jl6 wrote: post #5

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...

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.

I never heart that. My guess is that the difference is minimal. Do you have a source with a detailed calculation?

Re: What does the land under Antarctica’s ice sheet look like?

#75

Post by SketchySeaBeast »

addaon wrote: post #66
SketchySeaBeast wrote: post #35

Earlier quoted context omitted.

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 l…

> 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…

There we go - where land appears, it clumps.

Re: What does the land under Antarctica’s ice sheet look like?

#76

Post by cpleppert »

rr888 wrote: post #65
jl6 wrote: post #5

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...

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.

This effect only has an impact on the surrounding sea level, it somewhat counterbalances the local sea level rise from the melting ice sheet. It has no impact ( likes tides) on global sea levels.

Re: What does the land under Antarctica’s ice sheet look like?

#77

Post by therealdrag0 »

gus_massa wrote: post #74
rr888 wrote: post #65

Earlier quoted context omitted.

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.

I never heart that. My guess is that the difference is minimal. Do you have a source with a detailed calculation?

I just read this article about it https://nautil.us/why-our-intuition-about-sea_level-rise-is-...

Re: What does the land under Antarctica’s ice sheet look like?

#78

Post by therealdrag0 »

sanj wrote: post #70
rr888 wrote: post #65

Earlier quoted context omitted.

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.

Do you have a link to an article explaining this?

This article talks about gravity part https://nautil.us/why-our-intuition-about-sea_level-rise-is-...

Re: What does the land under Antarctica’s ice sheet look like?

#79

Post by ErikCorry »

joshvm wrote: post #72
ErikCorry wrote: post #69

Earlier quoted context omitted.

What about the actual South Pole? Looks like it might be over water.

The South Pole is also over bedrock, around 3 miles down. See "glaciology" here: https://icecube.wisc.edu/science/research/ Scientific implications would be IceCube would no longer work, because the premise is based on the detector(s) being drilled 2 km into the glacier. You can't just bury it in rock, it specifically needs a transparent medium and ice is surprisingly good for neutrino propagation. The other telescop…

Fascinating.

Is there any benefit to having in a place that rotates in situ rather than going around in circles in a given day?

Re: What does the land under Antarctica’s ice sheet look like?

#80

Post by gus_massa »

therealdrag0 wrote: post #77
gus_massa wrote: post #74

Earlier quoted context omitted.

I never heart that. My guess is that the difference is minimal. Do you have a source with a detailed calculation?

I just read this article about it https://nautil.us/why-our-intuition-about-sea_level-rise-is-...

Let's do some back of the envelope calculation. Using data from https://en.wikipedia.org/wiki/Antarctic_ice_sheet

The volume of the Antarctic Ice Sheet is 26.5 million cubic kilometres. If you use the Spherical Cow Theorem and put all that ice into an sphere, the radius is 185km https://www.wolframalpha.com/input?i=sphere+of+26.5+million+... . The gravity caused by that sphere at the surface is 0.047m/s^2 https://www.wolframalpha.com/input?i=gravity+of+24%2C380%2C0...

Compared to the usual acceleration of gravity that is almost 9.8m/s^2, it's only a 0.0048 = 0.48%. That is the slope of the real see compared to an ideal sea where there is no gravity from the ice. I'm using a spherical ice instead of a sheet of ice. With a sheet of ice the effect would be much smaller, but I'm too lazy to look up.

The gravity from the ice decrease as 1/r^2 when you go farther. We must integrate the slope to get the volume. I'm going to use a flat Earth, to simplify the calculation, but as the 1/r^2 reductions is quite fast, it's not a problem. With a curved Earth it will be more, but not too much.

Also, we must multiply by 2*pi*r to get the volume in the flat surface all around the sphere instead of the surface of a vertical cut of the sea.

The radios of the Earth is 6371km, so the "distance" to the north pole is 6371kmpi=20000km and we can cut the integral there https://www.wolframalpha.com/input?i=Integral+from+185+to+20... The result is 48,000 km^3 of water. But melting the Antarctic Ice sheet will release 24,300,000 km^3 So it's only a .2% more.

In other units, melting all the Antarctic Ice would increase the sea level like 58m (190ft). The additional effect of the gravity is less than .3m (1ft) And I expect that a calculation if a sheet shaped ice will give a much smaller result.

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