From the University of Texas at Austin
New map reveals giant fjords beneath East Antarctic ice sheet
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.
“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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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.
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/
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.
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.
So, did they find any Nazi artifacts under the ice at Neuschwabenland? Adm. Byrd went looking in 1946, but something ran him off….
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.
Galane says: June 2, 2011 at 12:03 am :
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.
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?
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.
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.
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.
“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)
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.
i don’t know about fjords. Is it conceivable it is another rift valley kind of situation?
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.
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 ?
“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 🙂
“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.
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.
“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 ??
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?
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?
“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.
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.
Adrian W says:
June 2, 2011 at 12:13 am
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.