Antarctic Ice Discussion

[knocker]

Drop in carbon dioxide levels led to polar ice sheet, study finds

WEST LAFAYETTE, Ind. — A drop in carbon dioxide appears to be the driving force that led to the Antarctic ice sheet's formation, according to a recent study led by scientists at Yale and Purdue universities of molecules from ancient algae found in deep-sea core samples.

The key role of the greenhouse gas in one of the biggest climate events in Earth's history supports carbon dioxide's importance in past climate change and implicates it as a significant force in present and future climate.

The team pinpointed a threshold for low levels of carbon dioxide below which an ice sheet forms in the South Pole, but how much the greenhouse gas must increase before the ice sheet melts - which is the relevant question for the future - remains a mystery.

Matthew Huber, a professor of earth and atmospheric sciences at Purdue, said roughly a 40 percent decrease in carbon dioxide occurred prior to and during the rapid formation of a mile-thick ice sheet over the Antarctic approximately 34 million years ago.

http://www.purdue.edu/newsroom/research/2011/111201HuberGlaciation.html

[Gray-Wolf]

If we sat above 600ppm CO2 for so long I wonder what became of the extra carbon that used to be within the carbon cycle?

Is a good proportion of it held within the permafrosts we have today? Could the slow move to an ice free Arctic bring enough carbon back into the cycle to take us above 600ppm (along with the Carbon we have re-introduced from long locked away deposits?) again.

With the recent observations of Methane seepage from the Arctic submerged and terrestrial Permafrosts I have to wonder just where our CO2 levels will platue out?

If the Antarctic was once a subtropical landmass then at the base of it's miles deep ice should be remnants of that ecosystem meaning even more carbon that could find it's way back into the carbon cycle over time?

I start to wonder just how far our current climate shift has to go before the planet again settles into an equilibrium?

[knocker]

Tropical sea temperatures influence melting in Antarctica

Accelerated melting of two fast-moving outlet glaciers that drain Antarctic ice into the Amundsen Sea Embayment is likely the result, in part, of an increase in sea-surface temperatures in the tropical Pacific Ocean, according to new University of Washington research.

Higher-than-normal sea-level pressure north of the Amundsen Sea sets up westerly winds that push surface water away from the glaciers and allow warmer deep water to rise to the surface under the edges of the glaciers, said Eric Steig, a UW professor of Earth and space sciences.

"This part of Antarctica is affected by what's happening on the rest of the planet, in particular the tropical Pacific," he said.

http://www.eurekalert.org/pub_releases/2011-12/uow-tst120511.php

[Snowangel-MK]

Here’s an interesting article on the Antarctic..... http://www.bbc.co.uk...onment-15735625

Ever wondered what Antarctica would look like without all that ice?

Scientists have successfully produced the most detailed picture of the Antarctic continents rock bed.

Visit bbc.co.uk/news to read all about it !

[Gray-Wolf]

Sea ice. Well the Arctic thread was not the place to discuss this?

We are now at the time of year for maximum ice melt but we seem to have a lot more ice than we are used to (BFTV puts it as 650,000sqkm?) so we need use our heads to figure 'why'?

Which ice melt out and which ice does not over a summer? Well F.Y. ice melts out in the Antarctic over the southern summer. Thick ice bergs/floes from shelf collapse do not (but they are included in the 'sea ice' extent). With Wilkins slow break down over the past few years we have had a steady stream of large, very thick, floes of ice making it's way into the seas around the continent. We also had the 'collision' of one of these 'ex' shelfs into the glacier snout adding another big chunk of ice into the seas around the continent.

I would be very interested in the 'figure' of the total extent that these floes bring to the Antarctic sea ice extent esp. when the ice approaches min. and the F.Y. ice is gone?

[loafer]

I find it hard to believe it could possibly be a material percentage of the 650,000 sqkm mentioned.

To be honest, GW, you need to relax and enjoy Christmas. At this rate if you won the lottery, you'd probably see it as a bad thing!

[4wd]

Everything has to be seen in the light of terrible man-made disruption.

It is rather hard to see how anyone can blame man-made climate change for simultaneously increasing sea ice at one pole while decreasing it at the other.

Granted the poles are very different but suggesting the increase in Antarctica must be due to glaciers sliding into the sea faster is pushing it.

The obvious explanation is that the air and ocean is a bit colder surely.

And human influence is rather trivial.

[Gray-Wolf]

How much SQ KM did we loose last year alone from the glacier tip that was knocked off by part of the o4' Ross calve berg? If you then look at the sq kms that Wilkins commited to the deep then you have a large proportion of that figure? The fact that we still have large slabs of the Ross Calve floating in the inshore waters must surely go some way to prove that some of the amazing sq km total since the 02' Larsen calvings ends up as 'sea ice' around the shores of Antarctica?

The other fact being the 'speed up' of the glaciers behind the ice shelfs that have been lost? what happens to the bergs that a glacier , moving at 10 times it's old speed, places into the southern oceans?

All in all you must concede that a significant amount of that 650sq km could easily be taken up with rubble from collapse.

[loafer]

The current SH anomoly is about 320,000 sqkm*.

I can believe that the events you refer to could be a material percentage of 650 sqkm (sic) that you quote, but not of 320,000 sq km.

*source : http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/seaice.anomaly.antarctic.png

[knocker]

Everything has to be seen in the light of terrible man-made disruption.

It is rather hard to see how anyone can blame man-made climate change for simultaneously increasing sea ice at one pole while decreasing it at the other.

Granted the poles are very different but suggesting the increase in Antarctica must be due to glaciers sliding into the sea faster is pushing it.

The obvious explanation is that the air and ocean is a bit colder surely.

And human influence is rather trivial.

There is another rather more obvious explanation. The man made ozone hole.

Increased growth in Antarctic sea ice during the past 30 years is a result of changing weather patterns caused by the ozone hole according to new research published this week (Thurs 23 April 2009).

Reporting in the journal Geophysical Research Letters scientists from British Antarctic Survey (BAS) and NASA say that while there has been a dramatic loss of Arctic sea ice, Antarctic sea ice has increased by a small amount as a result of the ozone hole delaying the impact of greenhouse gas increases on the climate of the continent.

Sea ice plays a key role in the global environment — reflecting heat from the sun and providing a habitat for marine life. At both poles sea ice cover is at its minimum during summer. However, during the winter freeze in Antarctica this ice cover expands to an area roughly twice the size of Europe. Ranging in thickness from less than a metre to several metres, the ice insulates the warm ocean from the frigid atmosphere above. Satellite images show that since the 1970s the extent of Antarctic sea ice has increased at a rate of 100,000 square kilometres a decade.

The new research helps explain why observed changes in the amount of sea-ice cover are so different in both polar regions.

Lead author Professor John Turner of BAS says “Our results show the complexity of climate change across the Earth. While there is increasing evidence that the loss of sea ice in the Arctic has occurred due to human activity, in the Antarctic human influence through the ozone hole has had the reverse effect and resulted in more ice. Although the ozone hole is in many ways holding back the effects of greenhouse gas increases on the Antarctic, this will not last, as we expect ozone levels to recover by the end of the 21st Century. By then there is likely to be around one third less Antarctic sea ice.â€

Using satellite images of sea ice and computer models the scientists discovered that the ozone hole has strengthened surface winds around Antarctica and deepened the storms in the South Pacific area of the Southern Ocean that surrounds the continent. This resulted in greater flow of cold air over the Ross Sea (West Antarctica) leading to more ice production in this region

.http://www.antarctic...ease.php?id=838

Edited December 24, 2011 by weather ship

[Gray-Wolf]

Agreed, not all the mid 'summer' anom is glacial/shelf ice but we must accept some portion of the remnant ice is! We need also be mindful that there is more 'sea' for ice extent to cover with the areas from the 11 collpased shelfs now counted as 'sea' and not classed as 'land' as the rest of the shelfs are.

Once again I'd welcome 4wd astute observations on the same?

[songster]

Why only from 4wd? Aren't any of the rest of us good enough? Indeed, why not go and look it up yourself?

From the British Antarctic Survey, on the first page of Google hits for "Antarctic ice shelf loss".

http://www.antarctic...ice_shelves.php

"Since the 1950s, a total of 25,000 km2 of ice shelf has been lost from around the Antarctic Peninsula."

From another article:

http://www.celsias.c...nd-what-it-mea/

"In total, Antarctic ice loss since 1950 exceeds 9,652 square miles" (I suspect that's a direct conversion of the

25,000 km2 figure)

That's the total ice shelf losses in the last 60 years, and it isn't even a meaningful fraction of the total anomaly, let alone the total ice area. It's around half the size of the average daily change in the Southern hemisphere anomaly (i.e. around half the day-to-day noise). Honestly GW, many of your comments are not just out by a small factor, but by multiple orders of magnitude.

Even if you grant that any number, no matter how tiny, may be relevant, you're simply wrong that it would bias estimates of ice loss. The only way this could affect the measurements is if the scientists were constantly updating the land masks and thus processing their data with an inconsistent set of masks. Nobody does that. If they update the land mask, then they reprocess the whole data set to keep things consistent. It's therefore as meaningless as the choice of which decade you use as the baseline for measuring anomalies

Ice shelf loss is important, sure - but not in the context of a direct effect on sea ice area. It's like complaining that people are mis-measuring the rate of coastal erosion because a bit of moss fell off your roof and they didn't take that into account.

Edited December 27, 2011 by songster

[Gray-Wolf]

http://www.nasa.gov/topics/earth/features/larsen-collapse.html

The sheer tonnage of losses must have me bamboozled Songster. To me, when I look at the sheer scale of the the ice losses The appear very significant (over 11 gigtonnes a year!!!) since the end of the 80's? As for the masking of the maps .Mr Grumbine assured me that the maps would reflect the changes in 'land area' but made no mention of 'normalising' the data for the rest of the set? How would you set about such?? (out of interest) would it not refelct wrongly on the process they are involved in mapping???

[songster]

Mr Grumbine assured me that the maps would reflect the changes in 'land area' but made no mention of 'normalising' the data for the rest of the set? How would you set about such?? (out of interest) would it not refelct wrongly on the process they are involved in mapping???

Well, all the satellite images are archived (and presumably the raw satellite microwave intensities as well, somewhere). Reprocessing data really isn't the hard part of the process, compared to acquiring it in the first place!

I don't know in detail how the masking process is currently handled, but I am sure that a consistent mask is used for any given ice area/extent product. If you're asking me how I personally would do it, I guess that if sufficient of the ice shelves crumble away as to materially affect the "land" area, then one would simply adjust the land mask and then recalculate the ice areas for the complete data set. That would have the effect of retroactively "adding" ice area to older dates, to be lost in more recent times. Fully documented, of course, so you'd put a prominent note somewhere saying "On <date>, the land mask was adjusted to reflect the loss of <x> km2 of ice shelf area, and the data set was reprocessed".

Edited December 27, 2011 by songster

[songster]

Logically, I think the ideal way to handle it would be to not mask the ice shelves in the first place - i.e. treat all floating ice the same. Then, on each annual cycle graph, put a second line showing the ice shelf area: this would be going down over time in jumps as various regions crumble. I suspect the main reason they don't do this is that the detailed outline of the land under the ice sheets isn't actually known - not to mention the fact that a "coastline" isn't even a well-defined concept in the regions where the ice is grounded below sea level.

[loafer]

To put the 10.4 gigatons of ice loss from the Antarctic ice sheet per year into context;

10.4 billion tons of ice is equivalent to 9.43 cubic km.

It is estimated that the ice sheet is 25.4 million cubic km.

The loss is therefore .000037161% of the ice sheet per annum since 2006.

Funny how a gigaton doesn't seem quite so scary suddenly...

Full calculation is here;

10.4 gigatons 1,000,000,000.00 tons 10,400,000,000.00 ton loss per annum since 2006 2,000.00 lbs in a ton 20,800,000,000,000.00 lbs loss per annum since 2006 62.40 lbs in a cubic foot of ice 333,333,333,333.33 cubic feet of ice loss per annum since 2006 0.0283168466 cubic metres per cubic foot 9438948866.66667 cubic metres loss per annum since 2006 0.000000001 cubic km to m conversion 9.4389488667 cubic km loss per annum since 2006 25400000 total ice sheet 0.000037161% percentage of ice sheet lost per annum since 2006

[Devonian]

To put the 10.4 gigatons of ice loss from the Antarctic ice sheet per year into context;

10.4 billion tons of ice is equivalent to 9.43 cubic km.

It is estimated that the ice sheet is 25.4 million cubic km.

The loss is therefore .000037161% of the ice sheet per annum since 2006.

Funny how a gigaton doesn't seem quite so scary suddenly...

Full calculation is here;....

But we don't know if that loss is: like saying losing part of your brain is only a tiny part of your body, or like losing a toe, or indeed like taking a crucial piece out of a Jenga tower? And, since much of the ice lost in in the small area of the Antarctic Peninsula the % loss there is much larger?

Of course Antarctica is a continent surrounded by water, it's also, mostly, very high. Much of it can stand a fair bit of warming with little change? But, is it like a toe, a brain or a Jenga block? Do we know?

[Gray-Wolf]

Mr Grumbine was quite clear that the 'shelf' was accessed as land and so needed 'altering' to allow it to become 'open water'. In most cases most of that 'open water is occupied by the shelf just shed.

And ,Indeed, pull of a corn , no issue. Pull off your main vien......

[loafer]

All very interesting, worthy and valid points, if speculative.

From an objective perspective, are you both able to concede that the original article was misleading by using weight as a measure instead of area or percentage of total?

[Devonian]

All very interesting, worthy and valid points, if speculative.

From an objective perspective, are you both able to concede that the original article was misleading by using weight as a measure instead of area or percentage of total?

I can't see anything misleading about the NASA article. It's talking about the peninsula and ice shelves not Antarctica as a whole? And there is nothing wrong with the figures?

[loafer]

What, other than a Gigaton sounds like alot, and 0.00003% doesn't?!

No wonder there are climate sceptics.

Science needs objectivity.

[Devonian]

What, other than a Gigaton sounds like alot, and 0.00003% doesn't?!

No wonder there are climate sceptics.

Science needs objectivity.

But, isn't the NASA Giga tonne figure for the peninsula and your % for the whole Antarctic?

I accept, and I'm sure NASA would, that not much of the total ice of Antarctica has been lost but it's also beyond dispute that a lot of ice has been lost form the peninsula - which, again, was what the article was about?

What % of Antarctic peninsula ice has been lost?

[loafer]

If you want to make it sound like a big figure, make it a %age of part of the peninsula...

Why don't you tell me what percentage of the peninsula ice it is...or don't they release that data because it doesn't sound so impressive...?

Science. Data matters.

[Devonian]

If you want to make it sound like a big figure, make it a %age of part of the peninsula...

Why don't you tell me what percentage of the peninsula ice it is...or don't they release that data because it doesn't sound so impressive...?

Science. Data matters.

But the article was about the Antarctic peninsula.

If I wrote an article about ice loss in the Antarctic peninsula I'd no more show that as a % of total Antarctic ice than I would show UK unemployment as a % of the total European workforce in an article about UK employment.

Edited December 27, 2011 by Devonian

[loafer]

I understand what you are trying to say, but it's premise is biased from two perspectives;

Firstly, I presume they didn't study other areas where ice wasn't breaking off.

Secondly, they didn't provide any context for their weight measurement within the study area so we don't know whether it is a little or alot? You and GW seem to have got excited by the word Gigaton without context.

I do agree that the weight over a subset study area, so dividing by the whole volume is equally misleading, but in the absence of any other objective context, we have no choice and at least it shows how minor the ice loss is in the context of the wider Antarctic.

What is certain is that it is pointless basing additional doom-laden questions speculating about the tipping point of the Antarctic shelf based on incomplete data - perhaps you can find the contextual info so we can work out whether we need to panic, or whether it is a PR release bolstering a fund raising, or somewhere between?