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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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
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.
I think Maybe Michael Schaefer is getting confused by this alarmism:
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?
They deserve a medal for bravery for flying a DC-3 in that environment. What a great workhorse.
Antarctic ice also floats before it melts.
That’s where most of the icebergs come: Antarctic and Greenland.
OK. This is seriously interesting. I love it.
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
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.
“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
Typo:
Since then, it has been comparatively stable,
stabile
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?
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???
“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.
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.
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!
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.
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.
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……..:)
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’
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?
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:
(from the same Wiki link above.)
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…
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?
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.
“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