Mechanical erosion of ice sheets

[parmenides3]

A bit of shameless self-promotion here; you might like to read my most recent entry on my blog: http://fergusbrown.wordpress.com/

on this very subject.

:)P

[Gray-Wolf]

A bit of shameless self-promotion here; you might like to read my most recent entry on my blog: http://fergusbrown.wordpress.com/

on this very subject.

P

I would and I did! If your lucky you may find others to blow your trumpet but, if your like me, you have to blow your own!!!

[Filski]

Hi guys, I've been following this thread for a while. The southern ocean is my area of interest so the article on cold pooling was very interesting. Just wondered if there was any new information on the Kamb Ice Stream. I've read a few old reports about ice balance in the Ross area and the relationship of the Kamb stopping. There are signs of relubrication of the base of this ice stream and an imminent restart of the flow. But all this is a couple of years old now.

[parmenides3]

I haven't seen anything specific on the Kamb; if you can let me know who was doing the earlier reseach, it might be easier to find updates. I don't even know where the Kamb ice stream is.

Pine Island seems to be flavour of the month at the moment, apparently it is a quite important indicator of what may be going on.

:)P

[parmenides3]

More fun and games. Here is a brand new paper on the George VI ice shelf from the Cambridge Journal Antarctic Science: truly a fascinating read for scholars of the subject.

http://journals.cambridge.org/action/displayJournal?jid=ANS

I coan't get the page to link directly, but it is in the current journal; click to connect.

It is open access, so no breach of copyright in printing the link. A neat, well presented 12 page article.

:)P

Edited April 1, 2007 by parmenides3

[Gray-Wolf]

Seems my twaddling on about 'old ice' declining and not being rebuilt is now gaining statistical proof as this NASA paper shows

http://earthobservatory.nasa.gov/Newsroom/...7040324675.html

I'm sure as the central mass of ice sheet ablates it will fall prey to wind/currents and be driven against the shallow (warmer) coastal waters and ablate at even faster rates than currently predicted.

[Gray-Wolf]

Well here's a good start point! Reasearchers at Boulder Colorado have this to say;

The researchers at CU-Boulder's Colorado Center for Astrodynamics Research also say there is a 57 percent chance the 2007 sea-ice minimum will be lower than the 2006 minimum of 2.27 million square miles, now the second lowest on record. There is a 70 percent chance the 2007 sea-ice minimum will rank within the lowest five years on record, according to Research Associate Sheldon Drobot of CCAR's Arctic Regional Ice Forecasting System group in CU-Boulder's aerospace engineering sciences department.

Sea-ice extent is the area of an ocean covered by at least 15 percent ice. Declining sea ice in the Arctic is believed by researchers to be caused by higher winter temperatures due to greenhouse warming, said Drobot. Arctic sea ice has been declining since the late 1970s.

Researchers pay particular attention to September and March because they generally mark the annual minimum and maximum sea-ice extents respectively, said Drobot. On April 4, researchers from CU-Boulder's National Snow and Ice Data Center reported the maximum extent of this year's March Arctic sea ice, 5.7 million square miles, was the second-lowest maximum on satellite record.

(thanks to science daily)

Edited April 22, 2007 by Gray-Wolf

[Iceberg]

Interesting discussion on the new AR4 release on ocean circulations, I've included this snipet because its good for this thread.

[parmenides3]

Nice find, Iceberg; shame the file is a bit tiddly: I have to wear glasses, you know...

Perhaps you could cut & paste it?

:)P

[Gray-Wolf]

Thanks Iceberg, maybe I wasn't totaly off my crunch to note the 'outflow cold anom.' last melt season flowing out from the Ross sea then?

[BrickFielder]

NSIDC Latest Report

Interestingly they pick up on the fact that climate models are failing to accurately forecast the atmospheric circulation changes due to global warming.

This is consistent with the failure of models to accurately show that whilst at low levels the greenland ice cap is melting at high levels it is getting deeper due to increases in precipitation (snow).

[Iceberg]

The worrying thing is that this has been going on for 40 years, and from looking at argo float data etc looks to be gathering pace (at least the anom is increasing more rapidly).

Most of the water would surely come from basal flow ?. and it's bad news if this is increasing and has done for so long...

Particularly with this being one of the suspected causes of the Larsen breakup. What prey tell is being damed up due to the increase precip and what is not ?.

A good call though G

Mr P it's a Jpeg taken from the PDF (I can't find a web version of it yet (bloody anoying !).) It's also the same size as the font in the PDF.

[Gray-Wolf]

NSIDC Latest Report

Interestingly they pick up on the fact that climate models are failing to accurately forecast the atmospheric circulation changes due to global warming.

This is consistent with the failure of models to accurately show that whilst at low levels the greenland ice cap is melting at high levels it is getting deeper due to increases in precipitation (snow).

Thank you very much for that Brickfielder!

I don't like things looking like they are starting to confirm my deepest fears but the last 12 months have brought us Radar pictures of ice streams /lakes acting in unexpected ways, sat images of ice sheets heaving up and down under the water pressure from below, circumpolar winds strengthening, basal freshening above and beyond predictions in both polar regions, new islands thawing out of the Greenland ice sheets, new evidence of how volatile the Ross embayment has been over the past 10 million years and increasing loads at the heads of glaciers/interior ice sheets.

I do find it a tad 'irksome' to be faced with folk reassuring me on yesteryears evidence when the real deal is happening in front of our eyes and common sense can predict the 'what nexts' as well as cutting edge science (so it would seem), hence this thread. I wonder how long before the title question is answered in the 'real world'?

[Filski]

This might be an appropriate place to add this link.

www.scar.org/treaty/atcmxxx/Atcm30_ip005_e.pdf

This is interesting

The SASOCS document was prepared during the last few months in the run up to the release of the Summary

for Policy Makers prepared by Working Group (WG) 1 of the Intergovernmental Panel on Climate Change

(IPCC) on February 2, 2007. The full report of WG1 will not be released on line until May 2007. Given the

timing of the SASOCS document, it can be taken as a more up to date version of the climate story than is

presented in the Policy Makers Summary, especially as far as Antarctica and the Southern Ocean are

concerned.

[Gray-Wolf]

This might be an appropriate place to add this link.

www.scar.org/treaty/atcmxxx/Atcm30_ip005_e.pdf

This is interesting

Thanks Filski, i think folk will get to the paper easier with the link below.

http://www.scar.org/treaty/atcmxxx/Atcm30_ip006_e.pdf

Seeing as we're in the international 'Polar year' I guess we'll be hearing more from them!

[Iceberg]

"Analysis of climate models suggests that by 2100 the marginal ice zone will warm in winter by upto 0.6C/decade, resulting in a decrease of 25% in sea ice coverl central antarctica will warm at 0.4C/decade in all seasons; precipitation will increase, westerly winds will stengthen over the ocean.

Drilling through the Ross sea ice shelf shows that the shelf has come and gone repeatedly over the past few hundred thousand years in response to climate change."

I think the next step(hopefully this year), will be to establish what the triggers are for the ice shelf collaspe and how quickly it happens.

Lots of other good stuff in here as well.

Matt

[Gray-Wolf]

Another interesting article for all those who would have the Antarctic 'colder than ever'.......

http://www.sciencedaily.com/releases/2007/...70515152520.htm

It would make more sense of the large sub-ice movements of ice streams/lakes measured over recent years and does now bring forward the spectre of 'ice sheet collapse through basal lubrication' (if set to become more frequent) a little closer.

Edited May 16, 2007 by Gray-Wolf

[parmenides3]

Try this one for size, then, from NASA: first evidence from QUICKSCAT shows antarctic melt in 2005:

http://www.nasa.gov/vision/earth/lookingat...c-20070515.html

:)P

[Gray-Wolf]

Try this one for size, then, from NASA: first evidence from QUICKSCAT shows antarctic melt in 2005:

http://www.nasa.gov/vision/earth/lookingat...c-20070515.html

:unsure: P

To me the area of greatest concern would be the mountains to the rear of the Ross embayment (furthest right of the 3 areas). The pathway for the 'free' water from the melt is down below the Embayment (thus lubricating it). The other thing to note, I suppose, is that this range is on the EAIS and at altitude, an area we 'supposed' was stable.

the image below shows the 'topography' of the continent minus the ice, sadly you need to turn it back (anticlockwise)90 degrees to have it in alignment with the NASA one but it shows what I mean.

Thinking on my feet here....it would seem to suggest crevassing that has been eroded by water all around the back of the Ross Embayment, i.e. no longer cemented to the 'coastal mountains' leaving only its 'resting on the floor of the depression forming the Ross.

With potential meltwater perculating underneath Ross (remember the ice lakes and their multimetre rises and falls of the ice field above reported this year?) then the potential for a rapid 'floatoff' of large sections of Ross may already be in the offing .If so,....well you can see where it could go from there.......

Edited May 17, 2007 by Gray-Wolf

[Gray-Wolf]

http://news.bbc.co.uk/1/hi/sci/tech/6665147.stm

This article is from another thread but it may have a bearing here. If the increase in the circumpolar wind is driving some of the 'deep water' mixing, flushing out the CO2 sink then what will basal meltwater pulses do down there?

The CO2 records from the end of the last glacial period show 2 spikes, one at 18,000yrs and another at 13,000yrs could these spikes be a reflection of CO2 'sinks' being flushed out as the final phases of melt sent pulses of dense,cold, fresh waters along the ocean bed?

EDIT: I've just added some pondweed to our new 'nature pond' and it doesn't take much of a localised disturbance to cause a clouding of all layers of the ponds water......life reflected in micro?

Edited May 18, 2007 by Gray-Wolf

[Filski]

Adding to the body of knowledge - sea levels rising at the upper limit of IPCC projections that use 'land ice uncertainty'.

http://www.pik-potsdam.de/~stefan/Publicat...cience_2007.pdf

[jethro]

Adding to the body of knowledge - sea levels rising at the upper limit of IPCC projections that use 'land ice uncertainty'.

http://www.pik-potsdam.de/~stefan/Publicat...cience_2007.pdf

And yet another example of the IPCC getting it wrong; we're all supposed to believe they've got their finger on the pulse. The worlds' greatest climatologists and scientists are supposed to know, almost beyond doubt that AGW is to blame and yet time and again the models do not reflect what is happening in the real world. Could it just possibly be that there is something else going on that we are unaware of? Or do we have to continue to buy into the belief that they haven't got it wrong, it's all feedback, tipping points blah, blah, blah. If I came up with a computer program which performed as poorly as these climate models, I'm sure, sooner or later, someone would point their finger at me and ask "you sure you put all the relevant data in? Could you have missed something out?"

[Filski]

Categorically - no. The IPCC is by nature a conservative bunch. This is well established. Not enough research or information about 'land ice' melting was known or could be agreed upon in time for this report. We now have a lot more recent information and more is coming out all the time. That does not mean they are worng, just cautious. They don't want to alarm the populace any more than Bush is interested in signing Kyoto.

The IPCC state something like 50-70cm of sea level rise could be expected by the end of the century. This is assuming a constant rate of melt from the ice sheets basd on a figure now known to be outdated. The actual rate is steadily increasing. Recent calculations start at 1.2m as a lower level of rise. The upper level is unkown because as this thread shows, we simply do not know what could happen.

FWIW a rise of 0.25m would inundate much of the Olympic site in East London.

[parmenides3]

Hi, Filski: I'd be interested to know where the 1.25m figure comes from. I've seen 'up to 1m' offered recently, but nothing more than that; do you have a source?

Regards,

:)P

[Filski]

Hi, it's a bit of a fag packet figure gleaned from Real Climate who did their own checking of the figures and a couple of other sources backing up the calculations. It's certainly not peer reviewed though. I also provided a link (post #139) with updated info and the graphs in post #146 also show real data at the upper limits of projections.