Radar mapping reveals ancient Antarctic giant fjords

From the University of Texas at Austin

New map reveals giant fjords beneath East Antarctic ice sheet

Radar Cross Section of Ice Sheet

This radar cross section of the ice sheet reveals the dramatic landscape at the base of the ice. Click to enlarge

Scientists from the U.S., U.K. and Australia have used ice-penetrating radar to create the first high- resolution topographic map of one of the last uncharted regions of Earth, the Aurora Subglacial Basin, an immense ice-buried lowland in East Antarctica larger than Texas.

The map reveals some of the largest fjords or ice cut channels on Earth, providing important insights into the history of ice in Antarctica. The data will also help computer modelers improve their simulations of the past and future Antarctic ice sheet and its potential impact on global sea level.

“We knew almost nothing about what was going on, or could go on, under this part of the ice sheet and now we’ve opened it up and made it real,” said Duncan Young, research scientist at The University of Texas at Austin’s Institute for Geophysics and lead author on the study, which appears in this week’s journal Nature.

“We chose to focus on the Aurora Subglacial Basin because it may represent the weak underbelly of the East Antarctic Ice Sheet, the largest remaining body of ice and potential source of sea-level rise on Earth,” said Donald Blankenship, principal investigator for the ICECAP project, a multinational collaboration using airborne geophysical instruments to study the ice sheet.

Because the basin lies kilometers below sea level, seawater could penetrate beneath the ice, causing portions of the ice sheet to collapse and float off to sea. Indeed, this work shows that the ice sheet has been significantly smaller in the past.

Previous work based on ocean sediments and computer models indicates the East Antarctic Ice Sheet grew and shrank widely and frequently, from about 34 to 14 million years ago, causing sea level to fluctuate by 200 feet . Since then, it has been comparatively stable, causing sea-level fluctuations of less that 50 feet. The new map reveals vast channels cut through mountain ranges by ancient glaciers that mark the edge of the ice sheet at different times in the past, sometimes hundreds of kilometers from its current edge.

Topographic Map of Aurora Subglacial Basin with Fjords Labeled

This new topographic map of a portion of the East Antarctic Ice Sheet revealed several giant fjords carved by the advancing and reatreating ice sheet between 34 and 14 million years ago. Click to enlarge

“We’re seeing what the ice sheet looked like at a time when Earth was much warmer than today,” said Young. “Back then it was very dynamic, with significant surface melting. Recently, the ice sheet has been better behaved.”

However, recent lowering of major glaciers near the edge detected by satellites has raised concerns about this sector of Antarctica.

Young said past configurations of the ice sheet give a sense of how it might look in the future, although he doesn’t foresee it shrinking as dramatically in the next 100 years. Still, even a small change in this massive ice sheet could have a significant effect on sea level. Scientists at The University of Texas at Austin’s Institute for Computational Engineering and Sciences, and at Australia’s Antarctic Climate and Ecosystems CRC are developing models that will use the new map to forecast how the ice sheet will evolve in the future and how it might affect sea level.

This research is part of ICECAP (Investigating the Cryospheric Evolution of the Central Antarctic Plate), a joint project of The University of Texas at Austin’s Jackson School of Geosciences, the University of Edinburgh and the Australian Antarctic Division. For three field seasons, the team flew an upgraded World War II-era DC-3 aircraft with a suite of geophysical instruments to study the ice and underlying rock in East Antarctica.

###

Funding for this research is provided by the National Science Foundation (U.S.), the National Aeronautics and Space Administration (U.S.), the Natural Environment Research Council (U.K.), the Australian Antarctic Division, the G. Unger Vetlesen Foundation (U.S.), the Antarctic Climate and Ecosystems CRC (Aus.), and the University of Texas at Austin’s Jackson School of Geosciences (U.S.).

A gallery of images is available at: http://www.jsg.utexas.edu/galleries/antarcticice060111/

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60 Responses to Radar mapping reveals ancient Antarctic giant fjords

  1. Michael Schaefer says:

    How a portion of ice that’s already under water should be supposed to rise the sea level when floating in the ocean, totally evades me.

    REPLY: That’s the ARCTIC that entirely floats, not the ANTARCTIC. Note the radar map, solid rock below, ice above. – Anthony

  2. Doug in Seattle says:

    While some of the valleys look like they could have been carved by glaciers the overall terrain must have been rapidly covered (draped?) by stable ice to retain its sharp relief.

  3. Mike Jowsey says:

    I think Maybe Michael Schaefer is getting confused by this alarmism:

    Because the basin lies kilometers below sea level, seawater could penetrate beneath the ice, causing portions of the ice sheet to collapse and float off to sea.

    Question: How much does the kilometres-thick ice weigh and how is it proposed that seawater penetrate beneath this massive weight of ice to cause this massive icecap to “float off to sea’? What’s up with those guys?

  4. Keith Minto says:

    For three field seasons, the team flew an upgraded World War II-era DC-3 aircraft with a suite of geophysical instruments to study the ice and underlying rock in East Antarctica.

    They deserve a medal for bravery for flying a DC-3 in that environment. What a great workhorse.

  5. Antarctic ice also floats before it melts.
    That’s where most of the icebergs come: Antarctic and Greenland.

  6. pat says:

    OK. This is seriously interesting. I love it.

  7. Sarah says:

    I guess it all froze over again thanks to the greens forcing the dinosaurs to switch to wind farms and energy saving bulbs instead of driving around in SUVs

  8. Roger Carr says:

    Michael Schaefer says: (June 1, 2011 at 10:37 pm)
    How a portion of ice that’s already under water…

    If Michael’s point concerns this paragraph in the paper, Anthony (“Because the basin lies kilometers below sea level, seawater could penetrate beneath the ice, causing portions of the ice sheet to collapse and float off to sea.”) it is a valid question it would be interesting to see answered. I do not think floating and land based point apply. The ice noted is below sea level.

  9. Richard111 says:

    “We’re seeing what the ice sheet looked like at a time when Earth was much warmer than today,” said Young. “Back then it was very dynamic, with significant surface melting. Recently, the ice sheet has been better behaved.”

    Must have been the penguins. /sarc

  10. Typo:
    Since then, it has been comparatively stable,
    stabile

  11. Richard111 says:

    REPLY: That’s the ARCTIC that entirely floats, not the ANTARCTIC. Note the radar map, solid rock below, ice above. – Anthony

    Just curious. That land is below sea level so only the ice above present sea level will be of concern?

  12. Justthinkin says:

    What a load of more CAGW bullcrap! You need only look at the sponsers of said project(?) to see the Warmistas hand at play again.
    And where is the evidence for their sea level rise figures? And just how much GHG does a DC-3 produce???

  13. barry says:

    “Just curious. That land is below sea level so only the ice above present sea level will be of concern?”

    The wight of the ice depresses the land beneath, by as much as a kilometer in some parts of the Antarctic. Isostatic rebound occurs when ice sheets melt. I don’t know the values, or how significant they are, but isostatic rebound would contribute to rising sea levels in a warming world. But the ice in the Antarctic is kilometers thick, and IIRC, a small percentage of the volume is below sea level.

  14. Galane says:

    How much would ice below sea level raise the sea level if it melted? Zero! Ice like mentioned above, which is below sea level and *not floating* would actually have a net *negative* impact on sea level if it melted.

    The only ice that can raise sea levels if it melts is ice that is both 1. above sea level and 2. not floating.

    Floating ice has a net zero effect on sea level when it melts because it’s displacing 100% of its mass and volume in water already.

    The AGW people love to go on and on about how huge the impact would be if the giant Ross Ice Shelf all suddenly melted, implying the entire ice volume of it would go directly into higher sea level. *bzzzt!* Wrong answer. Only the part of the ice that’s above sea level and not floating would. From what I’ve seen, the majority of the Ross shelf is below sea level.

    Now for the really puzzling bit, if that basin is below sea level *now*, how did the terrain get all carved up by ice in the warmer distant past? With less ice – and thus more water in the oceans – wouldn’t that have put that land even deeper down, under water? Are these researchers saying the land got depressed a large amount since the last warm period? It would have had to be above the higher sea level present when there was less ice, which allowed glaciers to move and carve up the land. Then it would have to be depressed to its present state below today’s lower sea level.

    This needs some more information added to account for such a large land elevation change in such a relatively short time.

  15. Hoser says:

    Because of the difference in density between liquid water and ice, 90% of an iceberg is below water. If more than 10% of the glacier is above sea level, then the sea cannot penetrate below the ice due to the excess weight forcing it out. If the bottom is “kilometers” below sea level, that means the glacier must be several hundred meters above sea level to stay grounded. The radar image shown indicates the surface of the glacier is between 2 and 3 kilometers above sea level.

    Why are we worried at all? The basin bottom would have to be at least 20 to 30 kilometers deep to float that ice. The thinnest part shown on the right side of the figure is only 2 km above sea level. The basin bottom appears to be about 1.5 km deep at most.

  16. Adrian W says:

    As a very non-scientist, yet another fascinating offering from WUWT. Thank you!

    But as a very accomplished consumer of drinks that contain ice, I’m really intrigued by the question of the ice below sea level and what it might do in the event of penetration by water. Since water expands in its frozen form, is it conceivable that ice, liberated back to liquid form in this situation, could actually take up less space and cause sea level to decline?

    And yes – I acknowledge in advance that this might be a silly question!

  17. Tony Mach says:

    So it is 2500 meters above the water line, and 1500 meters below water line (max), and only in the “blue dots”. How exactly is this piece of ice supposed to float? Bloody fearmongering.

  18. kwik says:

    So NASA is founding this as well? There you go. US taxpayers has lost control over what NASA is actually doing. Founding education of muslims, looking for fjords under the ice……..a very strange situation.

    In the mean time Rutan and Branson builds a new space travelling vehicle….

    Must be Post Normal Science. Nothing is normal anymore.

  19. Keith Minto says:

    Interesting study with helpful enlargements. That part or Antarctica ‘released’ Australia about 50mya and there is a match with the Great Australian Bight. Those fjords are shaped to be slipping into that ‘sea’, another rock profile is here.

    ICECAP ? ….. rings a bell……..:)

  20. Sandy Rham says:

    If you want to float a ship out of dry dock you must flood the dock to the ships waterline.
    Considering the E. Ant. ice sheet as a single iceberg would require a waterline that submerged 9/10 of the ice sheet.
    I would suggest that is probably a good few thousand feet above any historical sea level ever.
    There may be a layer of water from pressure (like an ice-skater’s blade) but it certainly can’t ‘float’

  21. omnologos says:

    Are they suggesting the climate has changed in the past in quite dramatic ways? Is there any radar trace of the ancient SUVs that caused that?

  22. Mike Jowsey says:

    Glacial melting is accompanied by rebound of Earth’s crust as the ice load and eroded sediment is removed (also called isostasy or glacial rebound). In some cases this rebound is faster than sea level rise.

    http://en.wikipedia.org/wiki/Fjord

    My apologies for not understanding. Perhaps someone will steer me in the right path….

    Sea water somehow ‘penetrates’ between ice and bedrock at enormous pressures, then somehow it causes the ice to break off and ‘drift off to sea’. Okaaaay.
    Then, according to the Wiki quote cited above the land will rise. So now the land rises, the pressure-at-depth is a little reduced and it is easier for the seawater to penetrate. Therefore, it’s a positive feedback! It’s worse that we thought.

    If only I was involved with Deep Freeze I could get on the gravy-ice train myself. This is gonna take some serious funding, for a decade or two. Trenberth would be proud.

    The problem I have though, is I do not understand the physics of seawater a couple of kilometres down being able to penetrate between ice and rock when the ice is continually sliding down the bedrock and it’s probably liquid methane down there anyway.

    An aside:

    The worldwide amounts of methane bound in gas hydrates is conservatively estimated to total twice the amount of carbon to be found in all known fossil fuels on Earth.

    (from the same Wiki link above.)

  23. Spector says:

    I assume, for the seawater to get in under the ice, the water pressure would have to be greater than the ice-pressure and that would depend on how much the ice is above sea level…

  24. Michael Schaefer says:

    How a portion of ice that’s already under water should be supposed to rise the sea level when floating in the ocean, totally evades me.

    REPLY: That’s the ARCTIC that entirely floats, not the ANTARCTIC. Note the radar map, solid rock below, ice above. – Anthony

    Antony, when I posted the above, I was referring to the following quote from the article:

    “Because the basin lies kilometers below sea level, seawater could penetrate beneath the ice, causing portions of the ice sheet to collapse and float off to sea.”

    While the basin lies kilometers below sea level, the ice on top of it is, to a large part, supposed to be below sea level too already, isn’t it?

  25. John Marshall says:

    A few comments on this post.

    Rock surface levels would rise if the ice melted due to isostatic adjustment. This would take several thousands of years.

    The ffiord indicated is more likely a river valley given the distortion imposed by the height expansion compared to range. Ffiords ratio of depth to width are different to that of river valleys which are wider than the depth.

    This graphic is never the less a good example of real climate change not the couple of degrees that the alarmists are scared about which lies within natural variation of weather in any case.

  26. David L says:

    “We’re seeing what the ice sheet looked like at a time when Earth was much warmer than today,” said Young. “Back then it was very dynamic, with significant surface melting. Recently, the ice sheet has been better behaved.”

    What BS. We all know the planet was never warmer. What are they talking about sea level fluctuation of 200 ft over millions of years? Everyone knows the sea only started to rise a few years ago. Its warmer and the sea is rising now because evil humans emit CO2. /sarc

  27. Terry says:

    Despite the arguments re ice floating etc that are being raised, for my money it is a welcome report that actually quantifies the true ice extent and if their interpretations are correct, how much used to be there. Makes a nice change from the “assumed” extent that is so often used as definitive data. Th more hard data we have , the better.

  28. Jimbo says:

    “We chose to focus on the Aurora Subglacial Basin because it may represent the weak underbelly of the East Antarctic Ice Sheet,….”

    Just as they chose the Antarctic Peninsula because it juts out so far so they planted loads of thermometers there while warming it UHI style. ;O)

    January 2010
    “SEA water under an East Antarctic ice shelf showed no sign of higher temperatures despite fears of a thaw linked to global warming……”
    http://wattsupwiththat.com/2010/01/11/antarctic-sea-water-shows-no-sign-of-warming/

  29. Brian H says:

    If the land were to rise there, it would sink somewhere else, so the effect would possibly be local. Depends where the “somewhere else” is, I suppose — and whether it’s linked to the oceans.

  30. Steve Keohane says:

    The ice below sea level melting and raising sea level caught my eye too. The following statement I found interesting as well.

    “Back then it was very dynamic, with significant surface melting. Recently, the ice sheet has been better behaved.”

    It seems to me that the assigning of anthropomorphic attributes to inanimate objects has been the basis of religion for eons, and goes on.

  31. Conspiratheorist says:

    So, did they find any Nazi artifacts under the ice at Neuschwabenland? Adm. Byrd went looking in 1946, but something ran him off….

  32. Tom Harley says:

    It would need an increase of tens of degrees C before this would all melt, I don’t think we would be around to see that in millions of years, even if we burnt every tonne of carbon. It would take an almighty upheaval to change this, like a killer asteroid hitting or something, or a massive continental shift.

  33. R.S.Brown says:

    Galane says: June 2, 2011 at 12:03 am :

    Now for the really puzzling bit, if that basin is below sea level *now*, how did the terrain get all carved up by ice in the warmer distant past?

    You’ve asked the right question.

    The continent we call Antarctica wasn’t always home to the “south” pole.
    Over the eons, thanks to “continental drift” the Antarctic land mass
    migrated to the location we find it now, relative to the other continents,
    ocean basins, and spreading centers.

    See the article by Campbell Craddock, “Antarctic Geology and Gondwanaland”,
    from the December, 1970, Bulletin of the Atomic Scientists at:

    http://books.google.com/books?id=EAcAAAAAMBAJ&pg=PA2&lpg=PA2&dq=Polar+migration+++continental+drift+Antarctic&source=bl&ots=cecy92RTQT&sig=OnjT9LgVrg-6J9lSy3j_7lmWGNI&hl=en&ei=2WnnTcqgIMaRgQfPwLjzCg&sa=X&oi=book_result&ct=result&resnum=2&ved=0CCEQ6AEwAQ#v=onepage&q=Polar%20migration%20%20%20continental%20drift%20Antarctic&f=false

    This was written long before changes in climate became synonymous with
    politically charged anthropomorphically influenced temperature or
    climate shifts.

    As the continent drifted into it’s current bottom-of-the-world position, it
    gradually “froze”. The gradual build up of the ice over the ensuing
    millennia physically depressed the land beneath it.

    If you look at the above radar “map” at around the 290 kilometer mark,
    there’s a “saddle” or “Twin Peaks” formation that is, I recall from a glaciology
    class long ago, a classic signature of once-active aggressive glaciation.
    (Don’t forget that little gotcha in the upper right corner of the map… 50 x
    vertical exaggeration make for a startling virtual snapshot. )

    If you’ll scroll down a bit after the Craddock piece, there are a couple
    more articles that seem germane to threads running here on WUWT.

  34. Myrrh says:

    Now for the really puzzling bit, if that basin is below sea level *now*, how did the terrain get all carved up by ice in the warmer distant past? With less ice – and thus more water in the oceans – wouldn’t that have put that land even deeper down, under water?

    I think it would have started out during a period of very much colder, during glacials the sea levels would have been much lower by several hundred feet. Glaciers are always moving anyway as you say, sliding and scraping the ground beneath, but this goes in overdrive during interglacials when the big melts set them moving with enough weight to carve out the huge glacial valleys, and then the land free of ice goes on the rebound up. The next re-freeze could have then depressed the frozen land with the basin blocked up and now below sea level only because our interglacial has raised sea levels some 350 feet. But if so, what’s puzzling me, is why hasn’t the sea melted more of it during the last few thousand years?

  35. Bill Illis says:

    It seems that large continental ice sheets do eventually push a land mass far enough below sea level that the oceans can seep in and break-up the glaciers.

    There is probably no issue with this given the extent and height of the current Antarctic ice sheet but I am surprised at how far below sea level some of these areas in Antarctica are.

    Land depression, ocean moving in and breaking-up the glaciers has happened before when north Africa was at the South Pole and to southern South America when it was at the south pole. It seems to have happened every 5 Mys during the Carboniferous ice age given the sea level changes which occurred.

    Hudson Bay is really just a depression caused by the peak load point of the glaciers during the ice ages. Look at Google maps and see how much of the continental shelf of north Europe and north Asia extends out into the Arctic ocean. It seems to me that at some point in the last last 1.5 Mys, this area was all above sea level, became significantly glaciated, the land was pushed below sea level and now there is only ocean there (except in the height of ice ages when the glaciers push back out into the Arctic ocean).

    Antarctica melted back to less than 1/4 of its present size between 27 and 14 Mys ago. May be this was part of it.

  36. Geoff Sherrington says:

    Have you ever wondered what the climate and geography were like some 700,000 years ago if that is the correct age of the Vostok ice core hole? It seems to have ended close to a rock basement.
    Was there no ice there 700,000 years ago? Is all the ice that is there now younger than 700,000 years? Are there any disconformities in the ice core, showing precious melting or erosion? Has the earlier basal ice (if any) been squeezed laterally away to the sea, there to melt? Has anyone found older ice being squeezed sideways into the sea in the Antarctic?
    That’s only a few questions for a settled science.

  37. 1DandyTroll says:

    Isn’t it a tad bit odd to to reference climate 34-14 million years ago in antarctica like antarctica was situated where it is now? Antarctica wasn’t really located in antarctica back the when grand dad was that young. If I understand it right, that piece of land has had the gall to move quite a bit since then.

    So why would the climate 34 million years ago be interesting in comparison to today.

  38. wws says:

    “Hudson Bay is really just a depression caused by the peak load point of the glaciers during the ice ages.”

    There’s a possibility that Hudson Bay is a scar left from an ancient collision, one that would have been far, far larger than the K-T event which ended the Cretaceous. Since the Canadian shield is some of the oldest surface rock on the planet, this could be a memento of an event that occurred at the dawn of land based lifeforms on this world.

    (and this has nothing to do with the now apparently discredited theory of an impact 13,000 years ago in the area)

  39. Jack Green says:

    Anybody ever done a study on continental drift and it’s affect on climate history of the earth?

    This is very interesting and brings up another question for you guys. All these modelers focus on the components of green house gases but what about the biggest component and it’s distribution over geologic time? That would be water.

    What would happen to the planet if there were no clouds? What would happen to the planet if there was 100% cloud cover? After all we have a planet that is 70% oceans. Has it ever been 90% ocean or 50% ocean? What affects would land mass vs ocean coverage have on climate?

    I think we spend too much money researching CO2 and other gases when we ignore the most common one H2O.

    If the oceans start rising maybe it would be cheaper to just build a pipeline to the south pole and spray sea water out over the icecap and make ice there by offsetting the melting if any. Kind of like the ski areas do.

  40. nandheeswaran jothi says:

    i don’t know about fjords. Is it conceivable it is another rift valley kind of situation?

  41. Jim G says:

    Jack Green says:
    June 2, 2011 at 8:23 am
    “Anybody ever done a study on continental drift and it’s affect on climate history of the earth? ”

    Saw a History Channel or Science Channel or some such channel that posed a theory that “snowball earth” was caused by continental drift blocking the ocean conveyor that brings warm waters north.

  42. a holmes says:

    The antarctic ice must be an enormous store of the intense cold in the winters , so how come seawater close to freezing but still liquid is able to trickle into the area below sea level without being frozen solid immediately it encounters the ultra cold ice ?

  43. u.k.(us) says:

    “We knew almost nothing about what was going on, or could go on, under this part of the ice sheet and now we’ve opened it up and made it real,” said Duncan Young, research scientist at The University of Texas at Austin’s Institute for Geophysics and lead author on the study, which appears in this week’s journal Nature.
    ====
    “There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact.”
    Mark Twain

    But, it’s a start :)

  44. Scott Covert says:

    “a holmes says:
    June 2, 2011 at 11:27 am
    The antarctic ice must be an enormous store of the intense cold in the winters , so how come seawater close to freezing but still liquid is able to trickle into the area below sea level without being frozen solid immediately it encounters the ultra cold ice ?”

    Obviously the antarctic ice can’t allow water to flow under the ice until the ice above sea level was less than 10% of the total ice volume and became neutrally buoyant.

    Your idea about quickly freezing water as it penetrates under the ice sheet might cause the ice to “stick” to the land beneath via suction as the ice forms all around the ice sheet. If that happened and the sea level rise /ice melt caused the ice above the sea level to be <90% the ice sheet would be positively buoyant but "stuck" to the land mass.

    Can you imagine the chaos that would happen when it finally got "un-stuck"? Tsunamis all over the world, other really bad stuff. It probably wouldn't drop sea level by much but it would move a hell of a lot of water in a short time.

    But the statement in the thread that water could get under the ice before the ice became neutrally buoyant is hog wash.

  45. Phineas says:

    Consider a homogeneous slab (2-D) of ice. Archimedes principle says:

    —If floating ice melts, water level does not change.
    —If ice is anchored and it melts above the waterline, runoff will raise the water level.
    -The underlying land can respond to the runoff by moving either up or down depending on whether the ice is buoyant, which depends on how much ice is above the waterline and how much is below (which can depend on how the ice is attached to the land).
    —The land’s response depends as well on its own mechanical properties and how its own mass is supported.
    —How the waterline (water level referenced to the land) changes is indeterminate without further information. A change in waterline will also change the buoyancy of any ice in contact with both water and the land (feedback).

    Consider two simple ‘bedrock’ cases – fixed land (no moving or stretching) with ice on top and surrounding water.

    1 – If the ice above water is massive enough, ice will weigh down on the bedrock. If ice above water melts, the ice weight (on the bedrock) will drop and the amount of water will increase (water level rises). This is the conventional GW scenario for ice melting and sea levels rising. However, in this same scenario, if submerged ice melts, the opposite happens – sea level drops and ice weight increases.

    2 – If ice is in some way attached (freezing?) to the bedrock and too little is above water, it will be buoyant (pull upward). As before above-water melting increases the water level and underwater melting decreases it. But now above-water melting increases (and below-water melting decreases) buoyancy.

    Even in such oversimplified examples, the case for GW melting and rising water levels is not leakproof. To be more realistic, the examples have to be expanded to allow ice and land to vary in horizontal directions. Then the mechanical responses of both become important – loading local ice does not affect distant ice beyond some distance ‘characteristic’ of the ice, so notions of loading and buoyancy must be expanded

    Overall, even these simple models based only on first principles exhibit complex behavior. In reality, of course, there are other things that bear on the outcome – the response of the land and how melting at the ice-land boundary is affected by pressure, to name but two. Sea level response (and therefore the global drowning bogeyman) is also complex, the more so because remote parts of the ocean are also involved.

  46. u.k.(us) says:

    “Because the basin lies kilometers below sea level, seawater could penetrate beneath the ice, causing portions of the ice sheet to collapse and float off to sea.”
    ====
    The devilish thing about ice is that it “sticks” to anything.
    Why is that?
    As long as the object stays cold the ice will not release its grip, so I assume the seawater penetration is warming the rock the ice has its grip upon.
    Heat transfer of rock vs seawater, anybody ??

  47. kadaka (KD Knoebel) says:

    Bold added:
    Scientists from the U.S., U.K. and Australia have used ice-penetrating radar to create the first high- resolution topographic map of one of the last uncharted regions of Earth, the Aurora Subglacial Basin, an immense ice-buried lowland in East Antarctica larger than Texas.

    I wasn’t aware of the ocean basins being charted all that well, let alone at a high resolution. When we were discussing the March 2011 Japan Earthquake and I was researching the differing terms hypocenter and epicenter to figure out what was meant by “…the hypocenter at an underwater depth of approximately 32 km (20 mi)…” (From sea level or sea floor?), I found there was a relative paucity of depth soundings for what should be a well-studied geographically important area around Japan.

    Have we really charted the ocean basins well enough to justify the “one of the last” statement and its implication the total job is nearly done, or is the writer just being land-centric?

  48. Galane says:

    Where has Antarctica moved in the past million years? I presume its location in that time has been pretty close to its present location.

    To have the ice cap reduced enough to where glaciers had the room to move through the Aurora Subglacial Basin, carving up the land, the whole planet would have to have been a lot warmer and sea levels higher.

    How does this time scale fit with the precession of Earth’s axis? Northern hemisphere winter is during perihelion and summer is during aphelion. That makes northern summers slightly cooler than southern summers, vice-versa for the winters – but- the southern hemisphere has much more ocean to moderate the temperature. That leads to an overall more temperate climate in the southern hemisphere except for in the antarctic which is in a deeper freeze at aphelion.

    Add to that the fact that most of the antarctic gets no heat input from ocean currents while most of the arctic does. With only atmospheric convection to bring heat to the antarctic when the sun never rises, plus winter at aphelion, it’s no wonder why the south pole gets colder than the north.

    Relatively warm water currents, plus atmosphere convection, plus 24 hour a day sun during perihelion – no wonder why the arctic ice cap shrinks so much in summer.

    What’s the effect when precession reverses the winter/summer perihelion/aphelion positions?

  49. tty says:

    “Because the basin lies kilometers below sea level, seawater could penetrate beneath the ice, causing portions of the ice sheet to collapse and float off to sea.”

    This can only happen under very special conditions. Since glacier ice is about 80-90% as dense as sea-water more than this proportion of the ice thickness at the coast must be below sea-level. Furthermore the depth to bedrock must continuously increase inland in order for the sea-water to be able to continue penetrating further inland under ever thicher ice. As far as I can see from the map this is not the case in this area. There is a sill of bedrock along the coast, so this is actually a glacier lying in a depression, the most stable type there is.

    “a holmes says:
    June 2, 2011 at 11:27 am
    The antarctic ice must be an enormous store of the intense cold in the winters , so how come seawater close to freezing but still liquid is able to trickle into the area below sea level without being frozen solid immediately it encounters the ultra cold ice ?”

    The ice at the bottom of the ice-cap is not “ultra cold”. It is close to melting due to geothermic heat and high pressure. A couple of kilometers of ice is pretty good insulation.

    “1DandyTroll says:
    June 2, 2011 at 6:52 am
    Isn’t it a tad bit odd to to reference climate 34-14 million years ago in antarctica like antarctica was situated where it is now? Antarctica wasn’t really located in antarctica back the when grand dad was that young. If I understand it right, that piece of land has had the gall to move quite a bit since then.
    So why would the climate 34 million years ago be interesting in comparison to today.”

    Sorry, but no. Antarctica has been fairly stationary near the South Pole since long before 34 million years ago.

    “Geoff Sherrington says:
    June 2, 2011 at 6:05 am
    Have you ever wondered what the climate and geography were like some 700,000 years ago if that is the correct age of the Vostok ice core hole? It seems to have ended close to a rock basement.
    Was there no ice there 700,000 years ago? Is all the ice that is there now younger than 700,000 years? Are there any disconformities in the ice core, showing precious melting or erosion? Has the earlier basal ice (if any) been squeezed laterally away to the sea, there to melt? Has anyone found older ice being squeezed sideways into the sea in the Antarctic?”

    Yes, the earlier ice has been squeezed laterally away to melt. Deep ice cores are taken at “ice divides” where sideways motion is zero, but ice divides move around with changing climate so it is probably difficult to find places where much older ice can be found even close to rock basement. Also there is basal melt in some areas which removes the oldest ice. Finding the old ice being squeezed into the sea is a tad difficult since it is all happening many hundred meters below sea level.
    However there is a chance of finding really old ice in Antarctica in the so called “blue ice areas”. Blue ice is old deep ice that has been blocked from moving by getting stuck against a mountain and is just lying there very slowly sublimating away. The oldest blue ice found up till now is about 500 000 years old, but in principle it can be as old as the present icecap, i e about 15 million years.

  50. Gary from Chicagoland says:

    I recall that the recent average temperature of Antarctic ice averages -37C, and the total mass is extemely large. Since seawater has a large specific heat value, the amount of time to melt this ice must be in the thousands of years, and by then Earth will be in the next Ice Age. In addition, the discussion of if this ice already below sea level today ever does totally melt, will it affect ocean levels is an excellent question. Al Gore says yes, but my guess states very little because this ice is already submerged. In addition, this continent may have been at the South Pole for millions of years, but before that it was much more north where liquid water could cause erosion and form the bottom physical features that the radar indicates are there today.

  51. Ric Werme says:

    Adrian W says:
    June 2, 2011 at 12:13 am

    … as a very accomplished consumer of drinks that contain ice, I’m really intrigued by the question of the ice below sea level and what it might do in the event of penetration by water. Since water expands in its frozen form, is it conceivable that ice, liberated back to liquid form in this situation, could actually take up less space and cause sea level to decline?

    If you had a chunk of ice held underwater by rocks sitting on top of it (or embedded in the ice), then yeah, when it melts, its volume would go down and sea level would go down. (Assuming there were no other processes affecting sea level!)

    In the case at hand, I expect that there is so much ice above sea level that sea water can’t get underneath it. There’s likely melting at the bottom anyway from ground heat. In that case, the water either flows someplace where it refreezes or it flows to the ocean at and ice settles from the top. The latter case would increase sea level just like any advance of above sea level glacial melt.

    Other processes, like snow fall, would likely be happening – after all, a glacier grounded like this grew into this situation and may still be growing.

  52. Mac the Knife says:

    Keith Minto says:
    June 1, 2011 at 11:14 pm
    “They deserve a medal for bravery for flying a DC-3 in that environment. What a great workhorse.”

    Keith,
    I suspect they were flying a ‘zero timed, stretched and strengthened’ DC-3 airframe, retrofitted with modern turboprop engines (“Polar 5″ or “Polar 6″). These wonderful old Douglas birds are ‘remanufactured’ to far better than new, at Basler Aircraft LLC, in Oshkosh WI, specifically for rugged ‘back country’ work!

    Oshkosh is also home to the single largest aviation conference, airshows, and aviation fly-ins in the world: The Experimental Aircraft Association (EAA) annual AirVenture! It’s the greatest aviation lalapalooza on earth, during the last week of July each year. Oshkosh is to aviation fans what mecca is to the muslims! Here’s a couple of links, for those similarly afflicted as I!

    Basler Turbo Conversions, LLC Basler Turbo 67 Aircraft
    http://www.baslerturbo.com/

    Experimental Aircraft Association
    http://www.eaa.org/
    http://www.airventure.org/

  53. Jim G says:

    u.k.(us) says:
    June 2, 2011 at 12:23 pm
    ““We knew almost nothing about what was going on, or could go on, under this part of the ice sheet and now we’ve opened it up and made it real,” said Duncan Young, research scientist at The University of Texas at Austin’s Institute for Geophysics and lead author on the study, which appears in this week’s journal Nature.
    ====
    “There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact.”
    Mark Twain

    But, it’s a start :)”

    It’s all of the “Iceholes” that cause these problems, in the ice sheet, that is. Lord knows there are plenty of them.

  54. Jack Green says:

    I wonder if they saw any inclusions in the ice like old airplanes, Noah’s Ark, giant flying saucers crashed 10,000 years ago, or old Coors Beer cans? I wonder if they saw any inactive volcanos under there that might erupt and cause a problem? Maybe Jimmie Hoffa is in there somewhere?

    Just thinking outside the box and trying to make the weekend more fun.

  55. Jim G says:

    Irrespective of temperatures, I would expect that glaciers if, indeed, resting on the bottom and not floating would continue to carve the fjords and those pictured need not be so old. Pressure creates its own lubricant for glaciers and if there is a slope they would conyinue on their merry way down hill.

  56. Keith Minto says:

    Mac the Knife says:
    June 3, 2011 at 10:29 am ,

    Thanks for that information and the links, fascinating. Looking at the photos later, yes, they looked like turboprop engines but I had no idea that the DC3′s were being remade to close to their original design. I spent a lot of time in these in outback NSW in earlier times, in the days when going up and sitting and chatting with the pilot was OK.

  57. pwl says:

    “The only ice that can raise sea levels if it melts is ice that is both 1. above sea level and 2. not floating. Floating ice has a net zero effect on sea level when it melts because it’s displacing 100% of its mass and volume in water already.”

    Given the accuracy of that,

    (1) What is the Total Volume all naturally occurring ice on Planet Earth?

    (2) What volume of the Total Volume of ice is floating in water?

    (3) What volume of the Total Volume of ice is sitting on the sea floor?

    (4) What volume of the Total Volume of ice is on land?

    How much will the oceans rise given the melting of each of these?

  58. stumpy says:

    lets see the ice become “lubricated” with melt water and “slip” of those puppies!

  59. jim says:

    Very interesting set of conversations! I would like to add the thought of a positive feed back loop.
    If for one unit of sea level rise there occurs 10 units of flooding or coast line recession along thousands of miles of mile thick glacier, would this not increase dramatically the rate of sea level change? I found the ICECAP article by looking for a topo-map of Antarctica that would show how the feed back loop i envisioned could or could not happen. I think it would be good if we could figure out the possibilities.

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