From AAAS online:
Widespread Persistent Thickening of the East Antarctic Ice Sheet by Freezing from the Base
Abstract
An International Polar Year aerogeophysical investigation of the high interior of East Antarctica reveals widespread freeze-on that drives significant mass redistribution at the bottom of the ice sheet. While surface accumulation of snow remains the primary mechanism for ice sheet growth, beneath Dome A 24% of the base by area is frozen-on ice. In some places, up to half the ice thickness has been added from below.
These ice packages result from conductive cooling of water ponded near the Gamburtsev Subglacial Mountain ridges and supercooling of water forced up steep valley walls. Persistent freeze-on thickens the ice column, alters basal ice rheology and fabric and upwarps the overlying ice sheet, including the oldest atmospheric climate archive, and drives flow behavior not captured in present models.
- Received for publication 8 November 2010.
- Accepted for publication 18 February 2011.
- Robin E. Bell1,
- Fausto Ferraccioli2,
- Timothy T. Creyts1,
- David Braaten3,
- Hugh Corr2,
- Indrani Das1,
- Detlef Damaske4,
- Nicholas Frearson1,
- Thomas Jordan2,
- Kathryn Rose2,
- Michael Studinger5, and
- Michael Wolovick1
+ Author Affiliations
1Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964, USA.
2British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 0ET, UK.
3Center for the Remote Sensing of Ice Sheets, Kansas University, Lawrence, KS, USA.
4Bundesanstalt für Geowissenschaften und Rohstoffe, Hannover, Germany.
5Goddard Earth Science and Technology Center, University of Maryland Baltimore County, MD, and NASA Goddard Space Flight Center, MD, USA.
I know nothing of glacial mechanics, but I have to wonder if super-cooled water does not play a significant role in glacial flow, rather than melting.
….so more atmospheric warming results in more melt..results in more ice formation beneath..hhmmm Surely the header should read “East Antarctic Ice Sheet getting thicker from underneath, thinner from the top”…or is there some agenda on here…surely not
Wow, that is impressive.
Despite several thousand feet of ice insulating the rock surface, the cold has been severe enough for long enough to freeze out the water that is found down there by conduction.
Also means the ice at the bottom is the youngest, not the oldest.
Interpreting those cores will be interesting.
Phenomenal! There are more things in heaven and earth…
Right now, it”s about 2:30 in the morning in California, Anthony. I know all of us want you to keep up the good work, but if you are in your home state, you are going the extra distance! We should allow you to rest.
Additional to my earlier comment: I meant to say ‘melting, as called for by the Antarctic-ice-sheet-is-gonna-collapse crowd.’
Fascinating stuff. Funny how the universal quest for knowledge pushes all of us in different directions; I was diverted by the term ‘rheology’, utterly new to me, and found a whole world of non-Newtonion liquids that behave in ways I did not expect. When I am preparing meals, I will look inside the neck of my honey and mayo jars each time I open them with a new understanding. Education late in one’s life is truly exciting,
super-cooled water is believed to be what brought down Air France Flight 447 in 2009.
“Accident investigators believe that super-cooled water in the clouds – well below freezing, but too pure to turn into ice – could have disabled the pitot probes.”
Read more: http://www.dailymail.co.uk/news/article-1282367/Air-France-crash-The-truth-disaster-killed-228-people.html#ixzz1G0Twk1Q6
In between the frivilous but humourous comments which I enjoy, I look forward to a comment from a knowledgeable person explaining what this really means.
Allied to this, it is often said that a deeper ice core hole at Vostok would meet bedrock. What does this mean? (a) Was there a period estimated at some 700,000 years or more ago when the globe was so hot that there was no ice where Vostok sits now? (b) has the basal ice from earlier times been squeezed sideways out of the picture? (c) would it not be interesting to discover where, on earth, there sits the oldest known ice in contact with rock below? (d) some people hypothesise that below Vostok there is a lake. Can it be that this lake is also freezing from the bottom up? (e) Is the time axis derived from Vostok horribly wrong?
I can offer no suggestions. I do not have to, because the science is “settled”.
@Baa Humbug:
Don’t know if I meet your qualifications, or if I’ve got it right, but what it said to me was:
1) Ice can form at the bottom. Some ice cores may ‘have issues’ due to this, or not, if you are careful.
2) Ice forms around the edges where there are puddles from the mountains. Ice growth is NOT just from snowfall. Measuring snowfall does not tell you total ice growth.
3) We don’t really know where all the ice is coming from.
4) We don’t really know the exact history of all the ice (as we now know some is from the bottom). So things like “it’s about this thick so about that old” are now broken.
5) How does adding ice from the bottom change the implied CO2 in the ice (if at all)? Does it in any way mess up the nice snow layers? (I’d guess not, but…)
6) Doing a “mass balance” that says “snow on / calving and melt off” will be saying “it’s MELTING” when it isn’t as you missed the “added from below” ice. It may well be growing a lot more than that technique would indicate. So you need something more like sats and radar measuring height…
7) It’s just kind of way cool and a new idea!
I’m sure there is more, but that’s the big bits I got at 4 am and sleepy 😉
Someone should tell Tim Naish about this because he seems to be coming to very different and alarming conclusions:
–Victoria University Antarctic and climate change researcher Professor Tim Naish has been watching the weather this year and has found nothing to reassure him.
In Antarctica, where Tim’s research is focused, the trends are the same. Both the Greenland and West Antarctic ice sheets are beginning to melt and new research suggests the same is happening to the world’s biggest ice sheet in East Antarctica.
“Rising sea levels present one of the biggest threats to civilisation as we know it,” says Tim.
Tim is Director of Victoria University’s Antarctic Research Centre and one of the lead authors of the next international climate change assessment from the Intergovernmental Panel on Climate Change (IPCC) , due for release in 2014. –
http://wiredcampus.chronicle.com/campusViewpointArticle/Climate-change-The-clock-is/388/
This is evidence that at this region on our earth, it is getting colder rather than warmer. Now they need to quantify the rate of cooling and determine what natural cycle of climate change it is following. It isn’t following the rise in atmospheric CO2.
For those of you who are questioning how water can exist below kilometers of ice, google “triple point of water”. Water flows and collects in the valleys and is not found in any significant quantities under ice cores taken over domes. But ice flows as well (much more slowly).
“Someone should tell Tim Naish about this because he seems to be coming to very different and alarming conclusions”
The most interesting thing about that interview is the things that are not mentioned. Note that now it’s the Pliocene, 3 or 4 million years back that is held up as the model for what will happen in 2100. Until quite recently it was the last interglacial 120,000 years ago, or MIS 11, the fourth interglacial back that were all the rage. The West Antarctic Ice sheet was supposed to have melted and the sea level to have been 6-9 or even 15-20 meters higher than now. Unfortunately the ANDRIL cores (that Tim Naish is involved with) showed that it simply didn’t happen. There has not been appreciably less ice than now in Antarctica for more than a million years, despite interglacials that were considerably warmer than the present one.
So now the AD 2100 horror story has perforce had to move back into Pliocene, when the climate and geography was vastly different from the present (there was no Panama Isthmus, just for starters).
Normal glaciers melt at the contact surface with the valley floor because of geothermal heat. This is why glacier streams flow. This water also helps glacier movement. So I do not understand this as there will be a significant amount of geothermal heat there and the thick ice insulates this surface from the cold atmosphere above.
Normal glaciers melt at the contact surface with the valley floor because of geothermal heat. This is why glacier streams flow. This water also helps glacier movement. So I do not understand this report as there will be a significant amount of geothermal heat there and the thick ice insulates this surface from the cold atmosphere above.
This seems to be largely a mass redistribution process. The supercooling process has been recognized in modern glaciers. It occurs when liquid water, pressurized by the weight of overlying ice reaches temperatures below freezing but does not freeze due to this pressure. Freezing may occur as the water moves to areas of lower pressure. The critical element for this to occur seems to be the bed slope vs. ice surface slope ratio. If the bed slope is 1.2-1.7 times the ice surface slope, then freeze-on of the supercooled water may take place. This is essentially the process described in the abstract. The freeze-on process occurs along overdeepenings (or in this case valley sides where the appropriate slope ratios are liekly met).
As some of you have suggested, and the abstract mentions, this will have implications for interpreting ice cores. However, there are likely very diagnostic ‘signatures’ of ice accreted by supercooling (physical characteristics and isotopic signatures) which should allow for its recognition in ice cores. The supercooling process also entrains sediments and freezes them in the ice layers (if sediments are present along the flow path prior to freezing), which maks these layers distinguishable form clean ice and layers of ice-rich sediment derived directly from erosion.
This is highly interesting and yet another glimpse into the ever evolving understanding of the subglacial hydrology of Antarctica.
BTW, regarding a previous comment, there is ice accreting at the base of Lake Vostok.
Fred H. Haynie,
I don’t think the temperature linkages are that simple. The refreezing water is either 1) very old and it has been ‘trapped’ in topographic saddles where the pressure keeps it liquid, and/or 2) it is young and produced by the pressure melting and the very limited sliding that occurs (if at all). The geothermal heat flux also likely melts some of the basal ice to produce some water (ice thickness is like an insulating blanket).
The main point is that there will be an enormously long lag time for a warming or freezing front to penetrate to that depth and tying it to an atmospheric cycle may be difficult due to this lag time. As well, by the time a warming/freezing front, reaches those depths, it may be difficult to differentiate the cause of the warming/cooling from the ‘background’ temperatures. There will also be some degree of feedbacks that will muddle the ‘signal’. For example, increased temperatures at the base (whatever the cause) could lead to greater melting, which could increase sliding and friction, leading to more heat generation. It might be possible to differentiate the sources of warming/cooling but it would depend on the magnitude of the changes relative to the ‘background’ and initial conditions, as well as the time scale(s) at which these changes can take place.
icicling ,
I agree. I have simplified the system for those who do not understand the basics. Still it is more complex than the simple model that increasing atmospheric levels of CO2 are increasing the rate of melting of Antarctic ice sheets.
Gary Mount says:
March 8, 2011 at 3:36 am
super-cooled water is believed to be what brought down Air France Flight 447 in 2009.
Supercooled water is pretty common in the atmosphere. Any time ice forms on a plane flying in cloud it is probably because of the prescence of supercooled water.
Yet another real world phenomenon that the models fail to allow for.
“Normal glaciers melt at the contact surface with the valley floor because of geothermal heat. This is why glacier streams flow. This water also helps glacier movement. So I do not understand this as there will be a significant amount of geothermal heat there and the thick ice insulates this surface from the cold atmosphere above.”
It’s not that simple. Glaciers can be both warm-based with a water film at the bottom and cold-based, i. e. frozen to the bed. Cold-based glaciers also flow, but slower than warm-based since they can only flow by internal deformation. Large ice-sheets (like Antarctica) are usually polythermic, i e partly warm-based and partly cold-based, depending on the thickness of the ice and the geothermic heat-flow.
“In some places, up to half the ice thickness has been added from below.”
Whew! That is a concept I never dreamed of. It simply has to seriously alter, bend, or even interupt the top-side flow of the ice. It will cause problems for any model that does not include the concept of ice-added-from-below.
This is an absolute mind adjuster as far as I am concerned. I would not have guessed this was happening, thanks be to the scientists who have discovered this process, I look forward to more enlightenment on the subject. Thanks again.
I read “getting thicker from underneath”, leaned back to laugh and my chair creaked. Time to lay off the doughnuts :/