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Antarctic Ice Discussion


pottyprof

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Posted
  • Location: Swallownest, Sheffield 83m ASL
  • Location: Swallownest, Sheffield 83m ASL

Before anyone posts in this area, please read the following.....

http://forum.netweat...ion=rules&f=105

Failure to abide by these rules will mean a 1 month ban from the climate discussion area, possibly leading to a permanent ban or a total suspension of your Netweather account.

With the Antarctic Ice melt upon us, what level of retreat will we see given that we have had some record extents over the last couple of years? How low will it go? When posting, please make sure you can back up your claims/details with links to relevant papers and articles. Links to blogs are acceptable provided they contain actual scientific detail and not just a personal view.

Enjoy the season. :drinks:

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Posted
  • Location: Mytholmroyd, West Yorks.......
  • Weather Preferences: Hot & Sunny, Cold & Snowy
  • Location: Mytholmroyd, West Yorks.......

I'd like to thank the Mod team for allowing this thread. http://nwstatic.co.uk/forum/public/style_emoticons/<#EMO_DIR#>/biggrin.gif

Right , Antarctica is a very different beastie from the Arctic with it's own set of unique issues when viewed in terms of 'Climate change' and ,in some ways, lead the way with the collapses of the ice shelfs over the past 20 years or so.

Because of it's geography we need to get to grips with upland ice sheets and their 'operating' along with Glaciers and their extensions over the ocean (ice shelfs and glacial tongues). By summers end we have not a lot of sea ice survives so my interest is focused on the ice shelf situation and the glaciers that feed them.

At present the main focus appears to be the 'pine island' area

post-2752-030529800 1285951808_thumb.png

as the warming works it's way down the peninsula and towards Ross.

Here's a nice image that allows you to see how the continent is two separate 'islands'

anttilttoday1.tiff

And here's an image of 'my crack' on the Roosevelt island side of Ross

post-2752-009383600 1285952041_thumb.jpg

when I last spoke with the guys down at McMurdo they were putting seismometers along it's length to check for movement and ,if I have things right, some of the first images from CryoSat2 showed the ,from surface to base ,and it looks set to go sometime soon

.

It'll make the 'Peterman Berg' look like an ice chip (when it does go) and will raise the question of Ross's future stability (again!).

Ross is 'grounded' below sea level (and about the size of France) so we could do with a stable Ross as it holds back the majority of the East Antarctic Ice Sheet. We are only just discovering how much Ross has changed through past warmings but it's now looking likely that we will see Ross fail at some point over the next 50yrs or so as the Ozone heals and global temps are able to penetrate into Antarctic proper and the warm seas into the remaining ice shelfs (which is already occurring around the peninsula as far as Wilkins).

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Posted
  • Location: Camborne
  • Location: Camborne

The Pine Island Glacier is creating much scientific interest in that it could contribute significantly to sea level rise. Specifically, what's causing it to speed up?

A few facts about the PIG.

  • Pine Island Glacier drains an area of 162, 300 km², two thirds the size of the United Kingdom.
  • The glacier was named after the bay into which it flows, which was named after the U.S.S. Pine Island, a ship that carried sea-planes and discovered the bay in 1947. This ship was named after Pine Island off the coast of Lee County, Florida.
  • The nearest base is the U.K.'s Rothera Research Station 804 miles away from the centre of Pine Island Glacier.
  • The glacier contributes ~ 83 km³ of ice to the sea each year, the largest contribution of any individual ice stream in the world.
  • Satellite measurements indicate the glacier thinned by ~ 1.5 m per yr and accelerated by ~ 10% during the 1990s. The speed has continued to increase by approximately 30% in the last decade.
Edited by weather ship
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Posted
  • Location: Orleton, 6 miles south of Ludlow
  • Location: Orleton, 6 miles south of Ludlow

Is there any evidence that Antarctica has been ice-free, like the Arctic has been in the distant past?

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Posted
  • Location: Camborne
  • Location: Camborne

Is there any evidence that Antarctica has been ice-free, like the Arctic has been in the distant past?

Depends what you mean by evidence. Some resarch has suggested that antarctica could have been ice-free at some point in the past but to the best of my knowledge that's as close as it gets.

http://www.telegraph.co.uk/news/worldnews/antarctica/5442820/Mountain-range-as-big-as-Alps-discovered-under-Antarctic-ice.html

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Posted
  • Location: Mytholmroyd, West Yorks.......
  • Weather Preferences: Hot & Sunny, Cold & Snowy
  • Location: Mytholmroyd, West Yorks.......

I think you'll find that Antarctica has been ice free for most of it's history as a 'continent'. We have plenty of paleo data showing more 'recent' melt episodes and it appears (as today) that the West Antarctic Ice sheet (W.A.I.S.) is always the first to be deglaciated. It will be interesting to see how the channel/sound between the two parts of Antarctica is deglaciated as this will prove key to the release of the ice on the Trans Antarctic Mountains that flank the edge of the East Antarctic Ice Sheet. This will involve a partial failure of the Ross embayment at the Roosevelt island end (the section with "my crack" on it).

By the time we get to Jan the ice/snow on Ross will have melted enough to show the ice stream that feeds this side of the shelf and the amount of crevassing that this stream undergoes on it's journey from the mountains. If ,as with other shelfs/glaciers, the process includes warm water attack at the base of the shelf (Ross is grounded below sea level) then we can expect large and rapid failures as the ice is floated off and the grounding line moves 'inland'.

Ross is the biggest 'buttress' on the planet and once it goes you can expect a 'mechanical collapse' of the ice it holds back and there after an acceleration of the E.A.I.S.'s 'drain glaciers' until a new equilibrium is reached.

As a thought I have to ponder how much the pressure of the ice to the rear of Ross will actually facilitate the final collapse of Ross by bulldozing it off it's anchorage on the sea floor and allowing float off. I cannot be sure but I think I read somewhere that if 1/3 of the front of Ross failed then the tremendous pressure from the rear will 'snap' the rest of the shelf off the sea floor and allow the ocean underneath 'floating off' the majority of the shelf in one catastrophic collapse (as we saw with Larsen B only much ,much bigger.

With Ross gone the Channel will be open to 'float off' (or partial 'float off'?) its ice working it's way across the sound towards Weddell. It would appear that the peninsula protects the Weddell sea from the worst of the Souther oceans storms so it may stay frozen until the channel has clear passage and 'chisels' it's way through Weddell to the southern oceans.

Be aware that none of this requires the kind of hike in temps it will receive when the circumpolar winds/drift slacken back off when the Ozone issue is resolved. What we see around the peninsula (and studied at Wilkins) is a warm water intrusion that is working it's way towards Ross. It was Beyond Pine island suite last year so may be knocking on Ross's door this southern summer.

I'm gonna be very interested to watch 'my crack' the next two melt seasons esp. now we have the Cryosat2 data (or will have shortly???).

Edited by Gray-Wolf
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Posted
  • Location: Camborne
  • Location: Camborne

Okeydoke. I stand corrected GW.

Antarctic Peninsula: rapid warming.

The Antarctic Peninsula is a rugged mountain chain generally more than 2000 m high, differing from most of Antarctica by having a summer melting season. Summer melt produces many isolated snow-free areas, which are habitats for biological communities of primitive plants, microbes and invertebrates, and breeding grounds for marine mammals and birds. During the last half-century, the Antarctic Peninsula has experienced dramatic warming at rates several times the global mean. This warming has been the focus of considerable recent research, and substantial progress is now being made in understanding the causes and profound impacts of this warming.

http://www.antarctic...c_peninsula.php

A brief note regarding the meteorology of the Antarctic.

The poleward air circulation in the tropospheric vortex leads to subsiding air over the Antarctic Plateau and outward flow over the ice sheet surfaces. The winds represent a balance between gravitational acceleration, Coriolis force, friction and inversion strength. On the slopes of the ice sheet, there are stronger downslope katabatic flows, and extreme winds are observed in some coastal locations. Cape Denison, Adelie Land, recorded average daily wind speeds of 35kts on over 60 per cent of days in 1912-13. This was the famous Douglas Mawson expedition.

The Antarctic is the windiest place on Earth.

Edited by weather ship
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Posted
  • Location: Camborne
  • Location: Camborne

I think you'll find that Antarctica has been ice free for most of it's history as a 'continent'.

I’ve given this a bit more thought and there are some loose ends somewhere. The following is an extract from “A History of Antarctic Science†by G.E. Fogg. This was written in 1992, so do I take it that recent paleo evidence has somewhat altered the thinking on this?

"The palaeontological evidence makes it clear that Antarctica was not always glaciated to the extent that it is now and that it had experienced climatic amelioration, for example, in Triassic times. Before that, in the severe Permo-Carboniferous glaciation, Antarctica was evidently the centre from which ice flowed outwards to leave tillites and other evidences of glacial action in other parts of Gondwana. The time of the onset of the most recent glaciation was speculative when Adie (1964) wrote his review but the finding of fossil penguins in the late Oligocene to lower Miocene of northern Graham Land suggested that the climate was getting cooler then. It seemed that the present ice-sheet had begun to form in the mid-Pliocene contemporaneously with that in the northern hemisphere. By the early 1960s there was considerable evidence from work on raised beaches, wavecut platforms, submerged sea caves revealed by SCUBA diving and morainic deposits interbedded with lava flows, of late Tertiary fluctuations in sea-level in the Peninsula and Scotia Arc area but accurate dating had not been carried out (Odell, 1952; Adie, 1964). These fluctuations seemed to have been greater in West Antarctica, where they were related to worldwide sea-level changes which caused the major outlet glaciers to rise in level as their outlets dammed up. The ice-sheet in East Antarctica seemed to have been more stable (Hendy et al., 1979). Drilling during the McMurdo Sound sedimentary and tectonic study showed that glaciomarine conditions in that area go back to late Palaeocene, 60 million years ago (Webb, 1983). A global temperature drop was inferred from isotope records to have occurred at the end of the Eocene, 40 million years ago, but there was no evidence from the Antarctic to support this. Ice-sheet formation presumably began about 25 million years ago when the continents comprising Gondwanaland had separated sufficiently to allow the Circumpolar Current to become established and isolate Antarctica. The major build-up of the East Antarctic ice-sheet appeared from oxygen isotope determinations on benthic foraminifera recovered from Deep Sea Drilling Project cores obtained by the Glomar Challenger to have started in middle Miocene, 12 million years ago (Savin, 1977; Frakes, 1983)".

Edited by weather ship
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Posted
  • Location: Mytholmroyd, West Yorks.......
  • Weather Preferences: Hot & Sunny, Cold & Snowy
  • Location: Mytholmroyd, West Yorks.......

http://home.freeuk.n...am/geochron.htm

http://www.coolantar..._antarctica.htm

obviously not the full 4.6billionyrs but a 'glimpse' of the strat history!

and , of course;

http://en.wikipedia.org/wiki/Geology_of_Antarctica

Edited by Gray-Wolf
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Posted
  • Location: Camborne
  • Location: Camborne

Well we won't beat this one to death. Rather depends on whether picog meant present day Antarctica when the Circumpolar Current became established 25 million years ago, or the millions of years prior to that.

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Posted
  • Location: Mytholmroyd, West Yorks.......
  • Weather Preferences: Hot & Sunny, Cold & Snowy
  • Location: Mytholmroyd, West Yorks.......

Well we won't beat this one to death. Rather depends on whether picog meant present day Antarctica when the Circumpolar Current became established 25 million years ago, or the millions of years prior to that.

Defo!

Once freed of the other land masses the unique circulation we see today was free to evolve. We must remember though that the continent has carried a lot less ice at times (in recent geological history) than today and the evidence of the partial melt 125,000yrs ago is something we must consider as global temps are heading in that direction? I think it unwise not to look at what a sustained period of warmth meant for both Greenland and Antarctica 125,000yrs ago even if our 'warm up' is much faster than back then and may cause a 'changed' response/timescale of change to what was experienced back then.

We now have evidence from southern Greenland (of this 'warm episode' )and ,more recently , evidence from Antarctica. Both seem to point to an imminent readjustment in current sea levels?

Edit: Would anyone wish to have a stab at how an increase of sea levels will impact the grounded ice in Antarctica (without any great hike in temps needed)?

Edited by Gray-Wolf
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Posted
  • Location: Camborne
  • Location: Camborne

Defo!

Once freed of the other land masses the unique circulation we see today was free to evolve. We must remember though that the continent has carried a lot less ice at times (in recent geological history) than today and the evidence of the partial melt 125,000yrs ago is something we must consider as global temps are heading in that direction? I think it unwise not to look at what a sustained period of warmth meant for both Greenland and Antarctica 125,000yrs ago even if our 'warm up' is much faster than back then and may cause a 'changed' response/timescale of change to what was experienced back then.

We now have evidence from southern Greenland (of this 'warm episode' )and ,more recently , evidence from Antarctica. Both seem to point to an imminent readjustment in current sea levels?

Edit: Would anyone wish to have a stab at how an increase of sea levels will impact the grounded ice in Antarctica?

I wouldn’t disagree with that. Also the Vostok ice core record is of some significance. The core gave direct evidence of past changes in carbon dioxide content of the atmosphere with variation over 100,000 years between glacial and interglacial periods and lesser cyclic changes with a period of some 21,000 years. These results show a close correlation with the temperature record (determined by the deuterium content and which themselves are in good agreement with the marine records as far back as 110,000 years). Thus, carbon dioxide concentration emerges as the major factor forcing, or following, temperature changes. I’ll opt for the former although it has been suggested that that these are triggered by and amplify insolation changes brought about in both the northern and southern hemispheres by orbital forces.

I'll have a think about your question re. sea levels (rather depends on the size) but just off to watch the rugby leave.

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Posted
  • Location: Mytholmroyd, West Yorks.......
  • Weather Preferences: Hot & Sunny, Cold & Snowy
  • Location: Mytholmroyd, West Yorks.......

Thanks W.S. (Rugby L. was my mainstay back in the day......when Swinton had a ground and Salford were just plain Salford!!!)

The prospect of any (relatively) sudden hike in sea levels (10cm+ or so) coupled with a spring tide/Strom swell has had me with concerns and I would like other folk's inputs.

We are becoming inundated with evidence for sudden climate 'snaps' , be they cold or warm, and rapid shifts in the global setup. With that as a backdrop (in a warming world) some folk ask 'how'? and though I'm reassured from many quarters that E.A.I.S. is 'stable' if the 'collapse' is mechanical (and not 'melt') then there seems to be scope for a rapid alteration to the mass balance there.

Edited by Gray-Wolf
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Posted
  • Location: Sheffield South Yorkshire 160M Powering the Sheffield Shield
  • Weather Preferences: Any Extreme
  • Location: Sheffield South Yorkshire 160M Powering the Sheffield Shield

I know the artic has been ice free in the past while the south pole hasn't. So how often have both poles be free from ice or one or the other have been free???

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Posted
  • Location: West London - ASL 36.85m/120ft
  • Weather Preferences: Cold/stormy
  • Location: West London - ASL 36.85m/120ft

Due to the artic being at the top of the world, how can global warming be the most effective there? I read in the daily mail that it is one of the most effected areas. Well, i disagree with that it hardly produces any Global warming so it is the other countrys effecting it. Thats what the daily mail did not make clear so really it is not the most effected country as it is not at the source of it unlike america which is one of the main sources so as it is not overhead as MUCH (i'm not saying it isnt as i know it is). So if the USA was at the top and was full of ice would'nt it be worse? so really i think there is not much saying its as bad there it is worse in the main countrys in my opiniun.

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Posted
  • Location: Cheddar Valley, 20mtrs asl
  • Weather Preferences: Snow and lots of it or warm and sunny, no mediocre dross
  • Location: Cheddar Valley, 20mtrs asl

Because of the way the atmosphere of the world works, the Arctic reaps the rewards of a warming world and therefore is effected more than the country of origin of the CO2 emissions.

Have a read through this to see how the process works:

http://climatepredic...climate-science

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Posted
  • Location: Orleton, 6 miles south of Ludlow
  • Location: Orleton, 6 miles south of Ludlow

Thank you — my question about the historic possibility of an ice-free Antarctica was very general, and you've provided some great info.

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Posted
  • Location: Mytholmroyd, West Yorks.......
  • Weather Preferences: Hot & Sunny, Cold & Snowy
  • Location: Mytholmroyd, West Yorks.......

Due to the artic being at the top of the world, how can global warming be the most effective there? I read in the daily mail that it is one of the most effected areas. Well, i disagree with that it hardly produces any Global warming so it is the other countrys effecting it. Thats what the daily mail did not make clear so really it is not the most effected country as it is not at the source of it unlike america which is one of the main sources so as it is not overhead as MUCH (i'm not saying it isnt as i know it is). So if the USA was at the top and was full of ice would'nt it be worse? so really i think there is not much saying its as bad there it is worse in the main countrys in my opiniun.

However bizarre it first seems the midsummer sun (24hrs) over the Arctic delivers the biggest wallop of energy (per sq metre of surface) than anywhere on the planet!

http://www.applet-magic.com/insolation.htm (scroll down to the table and check the summer solstice figures)

around 12.64 Kw/m2 (the equator max's out at 10.22Kw/m2)

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Posted
  • Location: Camborne
  • Location: Camborne

Thanks W.S. (Rugby L. was my mainstay back in the day......when Swinton had a ground and Salford were just plain Salford!!!)

The prospect of any (relatively) sudden hike in sea levels (10cm+ or so) coupled with a spring tide/Strom swell has had me with concerns and I would like other folk's inputs.

We are becoming inundated with evidence for sudden climate 'snaps' , be they cold or warm, and rapid shifts in the global setup. With that as a backdrop (in a warming world) some folk ask 'how'? and though I'm reassured from many quarters that E.A.I.S. is 'stable' if the 'collapse' is mechanical (and not 'melt') then there seems to be scope for a rapid alteration to the mass balance there.

I'm not sure the E.A.I.S. is the major concern. I suspect the major problem is the W.A.I.S. and people started worrying about this six years ago. A press release from BAS at the time explains it better than my woffle. http://www.antarctica.ac.uk/press/press_releases/press_release.php?id=47

21 September 2004 No. 13/2004 Scientists have found a remarkable new structure deep within the West Antarctic Ice Sheet which suggests that the whole ice sheet is more susceptible to future change than previously thought. The discovery, by scientists from Bristol University and the British Antarctic Survey in collaboration with US colleagues, is reported this week (September 24) in the international journal Science. The stability of the West Antarctic Ice Sheet has been hotly debated since the 1960s because of its potential to raise global sea level by around 5 m over several centuries. The potential impacts of a major change in the West Antarctic ice sheet are severe ? sea level rise will be fantastically expensive for developed nations with coastal cities and dire for poor populations in low-lying coastal areas. Lead author Prof Martin Siegert of Bristol University said, ?There is a great deal of speculation that global warming may cause sea levels to rise due to the melting of ice sheets. Until now, scientific observations suggested that change to the West Antarctic Ice Sheet would be restricted to the edges implying that large-scale instability of the ice sheet is unlikely. This new discovery deep within the ice means that we need to re-think our current assessment of the risk of collapse of this ice sheet.? The structure - a distinctive fold in the ice, 800m deep by 50 km long - was detected using ice-penetrating radar. Ice sheets normally consist of flat layers of ice, so finding this huge fold was a complete surprise. Its presence suggests that a few thousand years ago surface ice at the centre of the ice sheet was moving rapidly and being ?drawn down? towards the bottom of the ice sheet. More recently the rate of the ice flow has changed from fast to slow. The direction of flow has also changed. The most likely explanation for these changes is the ?switching-off? of a large ice stream at the margin of the ice sheet several centuries ago. These changes imply that the centre of the ice sheet is more mobile than scientists previously realised, requiring them to rethink existing models. ENDS Issued by the University of Bristol & British Antarctic Survey Press Offices The University of Bristol Press Office: Cherry Lewis: (w) 0117 928 8086, (m) 07729 421 885, (e) cherry.lewis@bristol.ac.uk British Antarctic Survey Press Office: Linda Capper (w) 01223 221448, (mobile) 07714 233744 (h) 01480 880302; (e) L.capper@bas.ac.uk Athena Dinar (w) 01223 221414; (mobile) 07740 822229 (h) +44 (0)1223 513298 (e) a.dinar@bas.ac.uk Notes for editors: The paper, Ice Flow Direction Change in Interior West Antarctica by Martin J. Siegert, et al. is published in Science. Vol 305, 24 September 2004 Picture editors: Video footage and stills of Antarctic ice sheets, ice streams and general views are available from the BAS Press Office Contacts : Professor Martin Siegert, Centre for Polar Observation and Modelling, Bristol Glaciology Centre, School of Geographical Sciences, University of Bristol, Tel: +44 (0)117 928 8902. Email: m.j.siegert@bristol.ac.uk (m) 07780 703008 Dr Edward King, British Antarctic Survey, Tel: +44 (0)1223 221580; Email ecki@bas.ac.uk Risk Estimation of Collapse of the West Antarctic Ice Sheet by David Vaughan and John Spouge, was published in Climatic Change January 2002, Volume 52, page 65-91. The authors used engineering risk-analysis techniques to conclude that there is a 5% chance of major sea level rise (1 metre per century) due to disintegration of the ice covering West Antarctica. This was the first study to gives a realistic assessment of differing scientific opinions in a useful way for policy makers. West Antarctic Ice Sheet (WAIS), which contains 13% of all the ice on the Antarctic continent. Currently this ice sheet is anchored to the rock beneath, much of which is below sea level. However, in past warm periods, the ice sheet thinned and disintegrated into floating icebergs. If the WAIS completely disintegrated, it would raise global sea levels by about 5 metres over several centuries. Ice sheet The Antarctic ice sheet is the layer of ice up to 5000 m thick covering the Antarctic continent. It is formed from snow falling in the interior of the Antarctic which compacts into ice. The ice sheet slowly moves towards the coast, eventually breaking away as icebergs which gradually melt into the sea. The ice sheet covering East Antarctica is very stable, because it lies on rock that is above sea level and is thought unlikely to collapse. The West Antarctic is less stable, because it sits on rock below sea level. If the ice sheet does collapse, it is more likely to be part of a natural collapse cycle, or as a response to climatic change that occurred many thousands of years ago, rather than a response to current climatic change. British Antarctic Survey is responsible for most of the UK?s research in Antarctica. It is a component of the Natural Environment Research Council. More information about the work of the Survey can be found on our website.

Not surprisingly the Dutch take this quite seriously as about half the Netherlands is at risk.

Edited by weather ship
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Posted
  • Location: Camborne
  • Location: Camborne

However bizarre it first seems the midsummer sun (24hrs) over the Arctic delivers the biggest wallop of energy (per sq metre of surface) than anywhere on the planet!

http://www.applet-ma.../insolation.htm (scroll down to the table and check the summer solstice figures)

around 12.64 Kw/m2 (the equator max's out at 10.22Kw/m2)

I must admit I find these figures very odd and frankly don't really understand them. My understanding has always been along these lines unless they are talking about something else such as measuring the energy prior to it being reflected. A tad deceptive if they are. On a second reading I realise the refinements have been ignored.

Effect of latitude

Different parts of the earth's surface receive different amounts of solar radiation. The time of the year is one factor controlling this, more radiation being received in summer than in winter because of the higher altitude of the sun and the longer days. Latitude is a very important control because this will determine both the duration of daylight and the distance travelled through the atmosphere by the oblique rays from the sun. However, actual calculations show the effect of the latter to be negligible in the Arctic, apparently due to the low vapour content of the air limiting tropospheric absorption. Figure 2.7 shows that in the upper atmosphere over the North Pole there is a marked maximum of solar radiation at the June solstice, yet only about 30 per cent is absorbed at the surface. This may be compared with the global average of 48 per cent of solar radiation being absorbed at the surface. The explanation lies in the high average cloudiness over the Arctic in summer and also in the high reflectivity of the snow and ice surfaces.

Source: Atmosphere, Weather & Climate (seventh edition) Roger G. Barry, Richard J. Chorley.

Edited by weather ship
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Posted
  • Location: Mytholmroyd, West Yorks.......
  • Weather Preferences: Hot & Sunny, Cold & Snowy
  • Location: Mytholmroyd, West Yorks.......

We seem to be at 'crossed threads' here? (that's why we weren't allowed 2 before I guess!)

The fact that (as we saw this year) we now have dark water, beyond 80N, changes that 'dated' figure somewhat. If we have 50% clearence of ice then we go from 90%+ reflected incoming to 80%+ absorbed incoming. This is why Arctic Amplification is such a worry as the change from one state (ice) to the other (dark water) is so marked.:)

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Posted
  • Location: Mytholmroyd, West Yorks.......
  • Weather Preferences: Hot & Sunny, Cold & Snowy
  • Location: Mytholmroyd, West Yorks.......

I'm not sure the E.A.I.S. is the major concern. I suspect the major problem is the W.A.I.S. and people started worrying about this six years ago. A press release from BAS at the time explains it better than my woffle. http://www.antarctic...lease.php?id=47

21 September ............................

SNIP

The West Antarctic is less stable, because it sits on rock below sea level. If the ice sheet does collapse, it is more likely to be part of a natural collapse cycle, or as a response to climatic change that occurred many thousands of years ago, rather than a response to current climatic change. British Antarctic Survey is responsible for most of the UK?s research in Antarctica. It is a component of the Natural Environment Research Council. More information about the work of the Survey can be found on our website.

Not surprisingly the Dutch take this quite seriously as about half the Netherlands is at risk.

I remember raising this on the 'old' Antarctic thread but not getting much feedback. The 'fold' suggests a lot of tied up energy in the sheet which will offload as soon as enough of the 'buttressing' at the coast goes. Folk seem to peddle in temperatures when talking about Antarctic mass loss.

This is not the be all and end all of ice loss.

The process that will cause 'collapse' will be a mechanical one due to the immense pressures involved within the 2 mile thick sheet.

Pour some golden syrup on a plate and watch it spread, this is what the mass wants to make the ice do and under the pressures at the bottom of the sheet 'plastic deformation' (as occurs in rocks at depth) will occur no matter what the temps do up above. The thing that forced the ice flow to stop (I imagine) was the setting up of the coastal ice shelfs as temps cooled enough. Because the majority of these are frozen to the sea bed we have a very solid anchor point to help 'buttress' the massive pressures behind. Over the past 20yrs this 'buttress' has begun to fail.

What happens next?

Edited by Gray-Wolf
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Posted
  • Location: Camborne
  • Location: Camborne

What happens next? That's a very good question. There is no definitive answer of course but it can't be ignored. As long as we don't get a sediment slide in Antarctica like the one that occured in the Mesozoic period which covered an area of at least 20km x 6km. We can do without further complications.

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Posted
  • Location: Camborne
  • Location: Camborne

A new report supporting the mechanical scenario of ice shelf collapse.

Depicting a cause-and-effect scenario that spans thousands of miles, a scientist at Scripps Institution of Oceanography at UC San Diego and his collaborators discovered that ocean waves originating along the Pacific coasts of North and South America impact Antarctic ice shelves and could play a role in their catastrophic collapse.

http://www.scienceda...00211175219.htm

Abstract from the paper.

http://www.agu.org/j...9GL041488.shtml

Edited by weather ship
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Posted
  • Location: Mytholmroyd, West Yorks.......
  • Weather Preferences: Hot & Sunny, Cold & Snowy
  • Location: Mytholmroyd, West Yorks.......

Very timely w.s.!

Again, what happens with a sea level hike or a full moon tide when such waves arrive?

I think folk depend too heavily on 2m temps when looking at Antarctica and not the mechanical forcing it faces. Bring in the ocean floor 'warm water' and grounding line recede and we have issues.

As I've said a partial collapse of Ross will lead to a complete collapse due to the pressures it is at present in 'equilibrium' with.

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