Mechanical erosion of ice sheets

[AtlanticFlamethrower]

If Ted Scanbos is right and there's nothing much that's out of the ordinary happening - eg. the RossB iceshelf collapse removed ice that had grown since the 1950s and 1960s - might scarce scientific funds be diverted to more important causes?

All well and good wanting to know if a glamarous End of The World As We Know It final catastrophe is about to happen it is another thing to be able to stop it happening. As you have said there may be no clear evidence anything is happening given processes work slowly until the final hours when it "breaks" - so what good will research do?

Given the likely increase in tourism to Antarctica and development on the continent I would have thought research into the production, size and range of icebergs would be top of the scientific agenda for Antarctica. Better maps and predictions of Antarctic icebergs would definitely help save lives.

Edited January 18, 2007 by AtlanticFlamethrower

[parmenides3]

AF: I suppose the main reason why the thread began was to consider the possibility of a collapse of the West Antarctic Ice Sheet. This could only occur, if my reading is correct, after the Ross Ice Shelf first detached and drifted off. Whilst both of these things are possible, recent papers estimated the possibility of a collapse of the WAIS starting (the whole process would take a long time) at about 50%, by 2200, assuming BAU scenarios. G-W, not unreasonably, sees the evidence of GW around the world in recent years as an indication that this could well be a conservative estimate. There is some support for his idea in the literature (but not much).

Because the Antarctic is so hard to model effectively, it is not much use relying on the climate models to show us the circumstances under which the Ross Shelf might deteriorate; so the work being done by the BAS and others on the ground is more important than it would otherwise be, for two reasons: first, an improved understanding of the processes of calving and ice failure, especially in relation to changes in temperature and sea conditions, helps improve the models and helps improve the likelihood of us being able to spot the problems ahead of time. Second, because the loss of the Ross shelf, followed by the anticipated outflow from the WAIS would commit us, pretty much irrevocably, to a large rise in global sea level in the following centuries; the implications of this are obvious.

I don't think it has ever been about stopping a potential problem, but more about placing the long-term risks and probabilities into the context of what GW could lead to in the future. With a few years more research, we may well be in a position to be more specific about when, or if, this event might happen.

My personal thoughts tend towards the more conservative estimates, but I would definitely not dismiss G-W's concern as unduly 'alarmist'; what he is postulating is not outside the bounds of reason or of the known science and, as we know, the state of understanding of the climate and its systems is a ongoing process. I would be more inclined to be worried, though, if I saw more signs of alarm from the BAS who are, after all, both expert and in situ.

Final postscript: I thought that the ITV coverage, showing the reporter drifting around bergs in the middle of the (very normal) Spring thaw, and claiming that it was hard proof of GW, was both risible and misleading. It's a shame they sunk to the obvious, instead of considering the real issues.

:)P

Edited January 18, 2007 by parmenides3

[AtlanticFlamethrower]

By 2200 chances are the whole Earth will have become a museum/nature reserve for the well-to-do martian tourist, while everyone else are zipping about Andromeda in space buggies.

That's if Supervolcano or some other unavoidable catastrophe doesn't stop human development first. Which is an important point.

There's reaction science - oh no problem! gasp! - and then there's solution science - let's do this, fix this, make this better - now.

Something like Antarctica's ice sheet is a side issue. Even the most dewy-eyed rainbow-swinging enviro kid doesn't believe it's going to happen within the next hundred years.

What's the rush? This would not even be *urgent* for the next generation of Phd students.

[Gray-Wolf]

I understand what is being said about pre-95 Antartica and our understanding of it's processes at that time but feel that we have entered a different rate of change down there over the past 10yrs.

As we are all aware change is slow to manifest in the region and though the Peninsula is warming fast (larger influence of sea warming due to the geography) I fail to see how the same oceanic influence will not start to have effect along all the Antarctic coastlines (including the shelf areas).

Personally I feel that Mr Lovelock has a good general feel for the planets 'response' to change (it mitigates effects as long as it is able up until a 'step change' occurs) .I believe the warming that should have occured over half of the last century is a climate shift that was 'tied up' for that period and along with the general trend to warming we also must factor in some of this 'lost warming' from the dimmed period.

We must all be aware that the state change from ice to water is only 1c but the differences of property in effect and response are very different in either state.

[Mondy]

Final postscript: I thought that the ITV coverage, showing the reporter drifting around bergs in the middle of the (very normal) Spring thaw, and claiming that it was hard proof of GW, was both risible and misleading. It's a shame they sunk to the obvious, instead of considering the real issues.

Agreed.

Why oh why did ITV sent yet another patronising reporter to Antarctica to do a piece to the camera with ice in the background? I'm guessing they didn't cycle there, so I can only assume they burned some fuel to make this complete waste of time possible. Do we really have to have the ice pointed at and have people say "This is ice! It is melting! We've come here to be of bugger all use other than to try and make our story more sensational."

Stay at home and look at pictures of ice instead if you need to see some so desperately.

/rant off\ [ ]

[Gray-Wolf]

They asked for you to 'ask their expert ' , so I did. This is what I got;

Ian

Thnaks for your email. It's way beyond me technically, so I've passed it on to BAS. Hope they can help.

Cheers

Lawrence

[Gray-Wolf]

They asked for you to 'ask their expert ' , so I did. This is what I got;

Ian

Thnaks for your email. It's way beyond me technically, so I've passed it on to BAS. Hope they can help.

Cheers

Lawrence

B**ger ,thought I'd be able to edit but no.

The Beebs climate change projections show the Ross Sea area with a 2-4c anomaly by 2020.....it only needs 1.5c to set things in motion.

As Mr MacAyeal (et al) told me as long as things remain as they are now thing's will remain in their current 'Go slow' mode.

Edited January 21, 2007 by Gray-Wolf

[Gray-Wolf]

B**ger ,thought I'd be able to edit but no.

The Beebs climate change projections show the Ross Sea area with a 2-4c anomaly by 2020.....it only needs 1.5c to set things in motion.

As Mr MacAyeal (et al) told me as long as things remain as they are now thing's will remain in their current 'Go slow' mode.

According to the NOAA satelite SST anomalies the Ross sea abutting the Ross ice shelf (the internal melt of the sea ice) is currently 2-4c above the 72-2000 average. As Mr MacAyeal pointed out in his appraisal if things remain the 'same' then no problems. If the others are correct then land temps of 1 to 1.5c lead to water pooling on the surface which, as with rocks, exploits the cracks/crevasses where it refreezes ,expands and causes collapse.

All eyes on surface pooling in March then.

The major carving events tend to happen in March so we may need to have a peep then. The remnant of the B15 calving (march 2000) has now developed an 'inlet' on it's eastern flank and may well be part of the 'calving' event later in the year.

From a few days of MODIS Rapid Response watching (been cloudy around the ice edge) the 'crack' that I'm watching appears more defined than ever leading me to think that surface ablation is now revealing the feature. Surface ablation means temps above freezing on the shelf front.

Edited January 25, 2007 by Gray-Wolf

[Devonian]

According to the NOAA satelite SST anomalies the Ross sea abutting the Ross ice shelf (the internal melt of the sea ice) is currently 2-4c above the 72-2000 average. As Mr MacAyeal pointed out in his appraisal if things remain the 'same' then no problems. If the others are correct then land temps of 1 to 1.5c lead to water pooling on the surface which, as with rocks, exploits the cracks/crevasses where it refreezes ,expands and causes collapse.

All eyes on surface pooling in March then.

The major carving events tend to happen in March so we may need to have a peep then. The remnant of the B15 calving (march 2000) has now developed an 'inlet' on it's eastern flank and may well be part of the 'calving' event later in the year.

From a few days of MODIS Rapid Response watching (been cloudy around the ice edge) the 'crack' that I'm watching appears more defined than ever leading me to think that surface ablation is now revealing the feature. Surface ablation means temps above freezing on the shelf front.

Interesting - do keep us informed

I'd not fully appreciated that re freezing melt ponds, and especially water filled cracks, are (of course ) going to expand when they freeze - very destructive I'd think? Is that's what happens though rather than them draining away or simply re-freezing on the surface? Does ice 'give' a bit more than say rock under such stress I wonder? Otoh, Larsen simply collapsed, and almost overnight ....

Edited January 25, 2007 by Devonian

[Gray-Wolf]

Interesting - do keep us informed

I'd not fully appreciated that re freezing melt ponds, and especially water filled cracks, are (of course ) going to expand when they freeze - very destructive I'd think? Is that's what happens though rather than them draining away or simply re-freezing on the surface? Does ice 'give' a bit more than say rock under such stress I wonder? Otoh, Larsen simply collapsed, and almost overnight ....

Doug MacAyeal seems to be the 'man of the moment' so far as Ice sheet collapse but if I understand him rightly it runs a bit like;

Glaciers roll down from the ice sheet. On the way down they 'roll over ' geographical changes' in the rate of descent (steep bits).

In rivers the point is called a 'knick point' and ,because the river is flowing faster than it did, the river displays the characteristics of a younger river (is rejuvenated) and so produces rapid, fast flowing water with all the features of a 'young' river (rapids, potholes, waterfalls etc.).

In a glacier it produces Crevasses and acceleration. When the cracks open up they can run as deep as the glacier. When the glacier 'hits the bottom' of the slope the cracks 'heal/refreeze' and the glacier rolls on.

When the glacier hits the coast it flows out over the water and calves into icebergs at the seaward edge. When a lot of glaciers do this in the same spot you build up an ice shelf (like the Ross).

The 'old' cracks are an inherent 'weakness' within the ice shelf.

When the ice approaches the sea and the ice in front 'falls away' pressure is released within the section of ice and the ice 'shears along the 'old cracks' and in slabs (deeper than they are wide, but very long! as B15 was!!!) the shelf 'calves into the ocean.

The crack I'm watching is longer than Hawaii but too wide for a single calving episode I feel (there are 3 other cracks in front) but it is displaying deepening (from my observations) as this years snow melts away, as though last march saw it open and then fill up with snow before satellite tracking 'spotted it' so this year is the first chance to 'see the damage' as it were. The crack formed in 1979 (was first observed) but since 2000 when B15 calved off it has been 'offloading' because it is no longer compressed by the mass of ice to the front.

EDIT; Of course we don't know 'where' we are in the ice sheet as the rapid acceleration that formed the 'ruck' within the WAIS will have had other influences too (the faster a glacier 'runs over' an obstical the more shattered it becomes ,less chance of 'plastic deformation' smoothing out the transit) so it is possible that we will experience rapid calving as a result of the smashed up condition of the ice as it presents at the 'ice front' from the period representing the end of the last ice age and the rapid sea level rises of around 14500yrs ago

Edited January 25, 2007 by Gray-Wolf

[Gray-Wolf]

Doesn't look like a 'business as usual' scenario down there does it?

Sadly plenty of cloud banks rolling in and off Ross for the past week so no chance to see my 'crack' and how it is responding to these abnormal SST's (just not what the good Dr ordered).

The section left by the B15 when it calved ( the one Mr MacAyeal said they had wired up) now has a large 'inlet' on it's eastern edge further exploiting the weakness that calved off B15. Maybe we'll get to see that go in March?

EDIT: for those who have no idea Ross is situated at the bottom between +160 and -160.

Edited January 30, 2007 by Gray-Wolf

[trevw]

The crack I'm watching

GW,

very interesting discussion/info, out of interest, what is your source of images? do you use the nsidc site? they seem about a month behind, I was wondering if there was somewhere that had more up to date images..

cheers

Trev

[parmenides3]

GW,

very interesting discussion/info, out of interest, what is your source of images? do you use the nsidc site? they seem about a month behind, I was wondering if there was somewhere that had more up to date images..

cheers

Trev

try http://www.seaice.dk/iwicos/ and check out the daily images/java links. They take a while to load up, but there's a lot there. :)P

Or you could take a look here: http://amrc.ssec.wisc.edu/realnoaa.html

Edited February 3, 2007 by parmenides3

[Gray-Wolf]

http://rapidfire.sci.gsfc.nasa.gov/

The above link puts you on the main page and you want to click on 'near real-time production'.

there are two Sat.s Terra and Aqua and they both pass over my crack (at 250m resolution) a number of times a day. These sat images are 2 to 3hrs behind.

http://www.nsidc.org/data/iceshelves_images/index.html

Gives excellent images of all the major shelves and are updated monthly/twice monthly (good for downloading and 'zooming in' on.

It is amazing once you get your eye in and due to the size of the place the more eyes watching (like amature astronomers and their 'use' in astronomy) the better.

Have fun! (remember the scale of things you're looking at........let yourself have a peep at the uk at 50m scale and then you'll understand)

[parmenides3]

G-W: how about a 'reference' image to show where your crack (sic) is? It isn't that easy if you don't know where to look in the first place!

:)P

[Gray-Wolf]

G-W: how about a 'reference' image to show where your crack (sic) is? It isn't that easy if you don't know where to look in the first place!

:)P

Being the numbskull that I am I can't upload the file/image. If you go to the 'Ice shelf' link I posted and search the 'East Ross Ice shelf' I think you'll spot it (on the dec28th 'intro' image or the later jan8? larger file). It is the areas 'behind' where B15 calved and is bounded by Roosevelt island to the east and goodness knows where on the west!. You can see the remnant chunk of shelf left by B15 calving stickiung out from the ice front with the crack now an inlet to it's East.

[Gray-Wolf]

Blinkin' edit feature.

Sorry P3 ,had to dash off to take Luke to his singing group.

The 'Remnant' from the B15 calving event is the one 'wired for sound'. They must expect it to calve soon and so they have positioned seismometers on it checking for it's rumblings prior to calving. Note the similarity of both cracks in dimensions (not length).

[Gray-Wolf]

I see that the East Ronne sheet is also having a 'collapse' I need to check where the ice front was last year as it could just be this years sea ice loosening away but it's a big chunk. I'll get back to you when I've seen a bit more.

[parmenides3]

Interesting that the AR4 has taken 'sudden ice sheet changes' out of its estimate for sea-level change, on the grounds that there is too little known to put a figure on it. this doesn't mean that they expect it to happen, just that they won't 'factor it in' to the numbers. Hmm...

:)P

Oh, thanks for the map!

:)P

[Gray-Wolf]

Interesting that the AR4 has taken 'sudden ice sheet changes' out of its estimate for sea-level change, on the grounds that there is too little known to put a figure on it. this doesn't mean that they expect it to happen, just that they won't 'factor it in' to the numbers. Hmm...

:)P

Oh, thanks for the map!

:)P

As far as I can gauge it seems the more we know the less we understand!

If AR4 is to be accepted as a 'reasonable and reasoned' assessment of our understanding today then best not labour on 'uncertainties' eh?

As an off topic aside I think the report is chilling enough reading as it stands but, as we both know, if it were to include all the recent observations/understandings then it could easily be an even more disturbing read.

I am interested in the southern melt this year as we have had quite an El-Nino winter here and I wonder just how that will manifest down there (esp. if we are to expect them to be more 'common' over the coming years) If storm swells generated in our oceans can 'shake up' the ice shelves whilst they are in melt then further denudation of ice fronts will occur. As was explained the Ross ice front is in its 1960's position (the front of Roosevelt island) and I wonder if the island acts as an 'anchor' for the front in this area. If my 'crack' were to cleave then it would take the ice front way back into the island and would then change the structural integrity that the island gives the sheet.

So far as water pooling occurring on the Ross shelf you can plainly see (to the south of McMurdo) blue pools of water on the glacier surface.

Edited February 4, 2007 by Gray-Wolf

[Iceberg]

I see that the East Ronne sheet is also having a 'collapse' I need to check where the ice front was last year as it could just be this years sea ice loosening away but it's a big chunk. I'll get back to you when I've seen a bit more.

To my eye there looks to have been a breakaway of older shelf ice, that's pretty much been attached to the rest of the shelf though thick sea ice.

[Gray-Wolf]

With the Larsen shelves floating off from this side of Antartica I am interested in the fate of the remaining shelves within this 'Big Bay' Hope you're enjoying having a look down there!

[trevw]

P3 and G-W, thanks for all the links - am starting to work through them now!

cheers

Trev

[Gray-Wolf]

P3 and G-W, thanks for all the links - am starting to work through them now!

cheers

Trev

It certainly gives you the 'big picture' doesn't it? I suppose we may see something happening that will be of use to the relevant bodies when we bring it to their attention. From the warm reception I have received from the Guys down there they are glad for the extra sets of eyes to help them with their research and to help them by not missing stuff (significant changes).

Edited February 5, 2007 by Gray-Wolf

[Gray-Wolf]

Interesting that the AR4 has taken 'sudden ice sheet changes' out of its estimate for sea-level change, on the grounds that there is too little known to put a figure on it. this doesn't mean that they expect it to happen, just that they won't 'factor it in' to the numbers. Hmm...

P

This is my quandry. To listen to the climatologists you'd feel that the melting of the Antarctic ice shelves ware a 'back burner' type of issue.

When you listen to the folk working on the Continent you come away with a very different feeling.

The New Zealand rags today are carrying a story on the Ross Ice sheet collapse by a Seismologist (Tim Naish) who is working on the sediment log beneath Ross (going back 3 million years). His work suggests that past Ross collapses have been extremely rapid (as with the Larson Shelf) and minor 'local' changes seem to be the driver for collapse.

Continued temp. rises over the summer months will bring this 'sudden collapse' closer to reality and the release of such a large amount of cold, fresh water has implications for the global climate.