Guest Post by Willis Eschenbach
In the first part of this disquisition, I discussed the oddity that the warmer it gets around Antarctica, the more ice accumulates on the Antarctic ice cap. However, that’s only one part of a very large planet. So I thought I’d take a look at the situation in Greenland. To start with, here is the Greenland temperature record:
Figure 1. Temperatures calculated from the ∂18O oxygen isotope levels and borehole temperatures in the GISP2 ice core in Greenland.
The data archive says:
DESCRIPTION:
Temperature interpretation based on stable isotope analysis, and ice accumulation data, from the GISP2 ice core, central Greenland. Data are smoothed from original measurements published by Cuffey and Clow (1997), as presented in Figure 1 of Alley (2000).
ABSTRACT:
Greenland ice-core records provide an exceptionally clear picture of many aspects of abrupt climate changes, and particularly of those associated with the Younger Dryas event, as reviewed here. Well-preserved annual layers can be counted confidently, with only 1% errors for the age of the end of the Younger Dryas 11,500 years before present. Ice-flow corrections allow reconstruction of snow accumulation rates over tens of thousands of years with little additional uncertainty. Glaciochemical and particulate data record atmospheric-loading changes with little uncertainty introduced by changes in snow accumulation. Confident paleothermometry is provided by site-specific calibrations using ice-isotopic ratios, borehole temperatures, and gas-isotopic ratios.
I note that after being a very chilly minus 45° to minus 50°C during the last glacial period, for the last 9,000 years or so the ice cap temperature has been running along at a smoking-hot minus 28-30°C …
So how does that temperature record compare with the Greenland ice accumulation rates? Figure 2 shows how fast the ice builds up on the ice cap:
Figure 2. Ice accumulation rate on the Greenland ice cap.
Dang. The situation is the same in Greenland as it was in Antarctica—the warmer it gets, the faster the ice accumulates.
Now, the Vostok area in Antarctica is like a frozen desert, in that there is little annual snowfall. So at Vostok, the ice accumulation rates varied from about 10 to about 20 mm/year between glacial and interglacial conditions. Greenland, on the other hand, is much wetter, with much more annual snowfall. There, the accumulation rates vary from about 60 to about 240 mm/year as the temperature change occurs.
The greater amount of snow is also responsible for the greater sensitivity of the accumulation rates to the temperature. In Antarctica, the ice accumulation rate increased by 1.2 mm/year for each additional degree. In Greenland, the ice accumulation rate goes up by 8.4 mm/year per 1°C temperature increase.
A final oddity. While overall the temperature and ice accumulation rates move in the same direction, look at the modern interglacial era. For the last 9,000 years or so, the situation is reversed. Temperatures have been steadily dropping, but the ice accumulation has been rising … go figure. During this time, for each one degree of warming, ice accumulation goes down by 3.3 mm/year, not a small amount.
OK, so the Greenland ice cap acts the same as the Antarctic ice cap, in that the warmer it is, the more snow falls, and the faster the ice accumulates … except for the last 9,000 years, when it worked the other way. Hey, I can only go where the data leads me.
But what about in the areas where people actually live? At present, do we get more ice and snow on northern lands when it is warmer?
My early researches say no, but stay tuned, I’ll assuredly get back to that piece of research as long as I don’t get distrac… oooh, shiny …
My best regards to all of you. Here, another two inches (5 cm) of rain last night, and it is pouring down now, with more storms on the horizon. The trees like it. The garden likes it. I like it. The gorgeous ex-fiancee likes it. The cat hates it.
w.
My Usual Request: Clarity is critical in order to ensure domestic tranquility. If you disagree with me or anyone, please quote the exact words you disagree with. I can defend my own words. I cannot defend someone else’s interpretation of some unidentified words of mine.
My Other Request: If you think that e.g. I’m using the wrong method on the wrong dataset, please educate me and others by demonstrating the proper use of the right method on the right dataset. Simply claiming I’m wrong doesn’t advance the discussion.
The point is Willis, you’re looking at twice the same.
I once tried to explain why in this draft here. https://dl.dropboxusercontent.com/u/22026080/non-calor-sed-umor.pdf
But I figured that it’s no use:
Thanks, Andre. You are the only person I know of who thinks that ∂18O measures humidity and not temperature … but the truth is, it doesn’t matter. Either one strongly supports the idea that “the warmer, the wetter”.
Regards,
w.
Seems not odd to me Willis; how else would it work ??
The ice on Antarctica, would pretty much have to come out of the Southern Ocean, South Pacific, South Indian, and South Atlantic oceans in that order and then proceed north to the cheese side of the pizza and finally to the Arctic ocean, if needed.
Antarctica is supposed to be the driest continent, and there is not much water making machinery there to make ice.
G
“You are the only person I know of who thinks that ∂18O measures humidity and not temperature”
It is an area of controversy, at least in the tropics. For example, from Climate Audit:
http://climateaudit.org/2013/04/07/the-quelccaya-update/
“There has been a longstanding dispute about whether d18O at Quelccaya and other tropical glaciers is a proxy for temperature or for the amount of precipitation. In monsoon region precipitation, negative d18O values show rain-out. Quelccaya d18O has been (IMO plausibly) interpreted by Hughen as evidence of north-south migration of the ITCZ, with Hughen comparing Quelccaya information particularly to information from Cariaco, Venezuela. It seems to me that, among specialists, Thompson is probably standing fairly alone in claiming that d18O at tropical glaciers is a proxy for temperature rather than amount effect.
The warmer, the wetter? Would the Bedouins in the Sahara agree?
Andre
I hope the Bedouins noticed that there were rivers and large lakes -and crocodiles, fish and hippos – in the Sahara 6,000 years ago when it was much warmer during the Holocene climatic optimum.
leftturnandre. Your paper is interesting. It’s dry and hot some places because of weather patterns but, where there is water to evaporate, more water will evaporate when the temperature is hotter. Globally, the surface are of water is relatively constant so a hotter planet should mean a more humid planet. Plants and trees also add significant water through evapo-traspiration. The coasts of the Arabian Peninsula have some of the highest absolute humidity levels recored in modern times but the rain fall elsewhere so they are very humid deserts.
Anyway, Willis
The notion of ice core isotopes not resembling global temperatures can easily be disproven. It’s probably too far fetched to get anybody out of the extreme cold doctrine of the Younger Dryas, but maybe MIS3 might do it. Just google “karginsk interglacial”, “farmdalian interstadial”, or the Klondike megafauna or check out fig 6 here epic.awi.de/9052/1/Hub2004a.pdf on page 1339. So much of the local evidence suggest conditions equal to or warmer than today. Now check where the isotope global temperatures were some 30-40 thousand years ago. See the problem?
Majormike1 notice that the African Humid period started some 15 thousand years ago http://www.ldeo.columbia.edu/~peter/site/Papers_files/deMenocal.etal.2000.pdf while the world was supposed to be just starting to pull out of the ice age. So maybe it was not the temperature that caused the African Humid Period.
I don’t see the last 9000 years as anomalous. By comparison to before, still very ‘warm’ so ice accumulates. Glacier Girl is non-ice core evidence. There is uncertainty in all the ice core data as well.
Possible that the last 9000 years are not anomalous … but still, one is going up and the other going down.
w.
Izzere some inherent reason why north and south need to co-operate, or disco-operate or whatever ??
Can’t they just act locally as makes sense to each ??
G
Thanks, Willis, for yet another interesting analysis. It would be quite helpful to see the two graphs in one, so that it could be seen, for example, whether the results of the last few k years are actually that different (has it happened before, briefly?).
Thinking contemporaneously with 9,000 years ago, temperature warmed rather abruptly, snow accumulation increased more slowly, as sea levels were rising and snow fields were melting. That could be related, or not. The shape of the ice accumulation graph closely resembles the sea level rise graph for that period.
How much might the rise and fall of the sea levels between the glaciation and inter-glaciation periods effect things? The cause for the snow accumulation difference could be as simple as the shore being closer or further away.
Is it a case the warmists looking at the wrong driver? Could the phenomena you describe be due to water/water vapour? The warmer the system the more water evaporates to form clouds and rain. In cold regions the precipitation comes down as snow and ice. Therefore, more ice accumulates the warmer it gets. Locking up water as ice and snow would also act to slow down any rises in sea level.
If so, then there is probably sufficient feedback mechanisms that would ensure that the variations in global temperature would be comparatively minor – only a percent or so on the Kelvin scale. One feature of the temperature record is that the variation is comparatively minor, though it may not seem so to the panic stricken.
Amazingly detailed response of snow/ice accumulation and temperature. I would have thought that the delta snowfall between, say -50 and -30 would be insignificant but on the warmer end, it would be much more evident. Having grown up on the Canadian prairies, I don’t recall much snow falling below 30C. For more temperate areas that get snow, it seems that one should expect more snow (or rain) with warmer weather.
I’m probably missing tons of compiled insight on this, but is the Greenland Ice Cap where it is because of weather patterns and storm system tracks that put it there over time?
The Greenland ice sheet is where it is, because the shape of the island protects the ice.
The Greenland sheet should have gone long ago, just like the grounded polar cap has melted long ago. However, the underlying topography of Greenland forms a convenient bowl, that prevents the ice sheet flowing off the edges. And it also protects the base of the ice sheet from the warm warters of the N Atlantic Gulf Stream.
http://www.csmonitor.com/var/ezflow_site/storage/images/media/content/2013/0830-greenland-canyon-topographic/16859445-1-eng-US/0830-Greenland-canyon-topographic_full_600.jpg
thanks for that map. I was aware of the topography but have never seen such a clear visualisation. Very nice.
Wow, that’s a powerful point.
An example of covering all factors.
Nice subsurface map, but that’s not the answer I expected. The bathtub shape of the basement rock is a result of the weight of the ice and not some unique island morphology that came before. The same bathtub effect has now been mapped in more detail in Antarctica. My question was about the placement of the island in weather patterns and storm tracks explaining the ice deposition that created the column. Greenland’s exposure to ocean currents may be more unique than other areas such as Baffin, etc.
Glacier girl was found under 264 feet of ice, rather a lot over 50 plus years. Willis when do you think that Greenland GISP 2 graph ends? I understand it’s about 1850s. So what would it look like extended to 2015? Just asking. And just about the most important question of all. Has Greenland gained or lost ice since 1950 and 1990?
“Willis when do you think that Greenland GISP 2 graph ends? I understand it’s about 1850s. So what would it look like extended to 2015?”
http://wattsupwiththat.com/2013/04/13/crowdsourcing-the-wuwt-paleoclimate-reference-page-disputed-graphs-alley-2000/
“Any graph that claims to use Alley’s GISP2 data must either finish at 95 years Before Present (BP=1950) or AD1855 because that is the final date in his database which is on-line and freely available to us all. Lappi’s graph mistakes Present for 2000 as does Easterbrook, they should have a note added pointing out their error or be excluded.”
And (One interpretation)….
http://oi53.tinypic.com/sg2wav.jpg
Toneb thanks for that graph update. According to your adjustment Greenland is warmer today than during the Med WP. And would you care to speculate about ice accumulation or not since 1950 and 1990?
Err, not sure what you mean here, but the deepest ice cores from Greenland go back about 110,000 years. The upper layers are the thickest, and they get progressively thinner down below, as they are squeezed from above. So most of the climate record, is in the last 1/3 of the sheet depth.
Regards Glacier Girl, at Gisp2, the 1945 layer is only 22 meters down. So I imagine that Glacier Girl has sunk through extra layers, due to her weight.
The depth and age of the layers at Gisp2 are as follows:
100 m. 275 years ago
500 m. 2 kyr
1,000 m. 5 kyr
1,500 m. 9 kyr
2,000 m. 24 kyr
2,500 m. 57 kys
2,800 m. 110 kyr
(Data: Mayewski et al, ‘Gisp2 Ice Core 110,000 Year Ions Data.)
Note: ‘years ago’ or BP means before 1950. Scientists wanted to get away from the ‘BC-AD nonsense’, but all they have done is made a new BC-AD in the recent past.
R
“Regards Glacier Girl, at Gisp2, the 1945 layer is only 22 meters down. So I imagine that Glacier Girl has sunk through extra layers, due to her weight.”
No, the snow is too compact for that. GISP2 is much further north and has a much lower accumulation rate. Also the landing site was fairly close to the coast where accumulation rates are high while drilling sites are inland right on the ice divide (which is the only place where very old ice is preserved).
“Note: ‘years ago’ or BP means before 1950. Scientists wanted to get away from the ‘BC-AD nonsense’, but all they have done is made a new BC-AD in the recent past.”
Not quite. The 1950 convention was adopted because (1) that was about the time when radiocarbon dating was invented and (2) a fixed reference point was needed so different radiocarbon dates can be easily compared and (3) 1950 is just before the first H-bomb tests messed up the amount of C14 in the atmosphere.
More like 60 years.
g
Not 264 feet of ice, 264 feet of mostly compacted snow. As a matter of fact that depth is just about the point where the pressure gets high enough to compress the firn into solid ice.
As Dr. Lindzen has often pointed out the recent warming is tiny. It is way to small to be a significant change from a climate perspective. I think the last 9000 years are generally a warming trend. It really didn’t start to get cooler until the end of the Roman Warm period roughly 2000 years ago. The Medieval warm period was an anomaly in a generally cooling trend. There might be a little bit of cooling between the Minoan Warm Period and the Roman, but it is not large. If we continue to cool, then I bet the precipitation will taper off with time. History shows cool=dry=bad and warm=wet=good. I agree with Kelvin Duncan on that. Remember in the Holocene Thermal Optimum the Sahara was a lush savanna. It didn’t turn into a desert until it got cooler after 5000 BP or so and that was a slow process taking hundreds of years.
“For the last 9,000 years or so, the situation is reversed.”
The Polar See-Saw, it exists when the Arctic is open to warm Atlantic currents through inter-glacial periods, and you should see the same effect in the warmer and longer DO events. The 8.2kyr event shows as warm spike on the Vostok proxy, as does the period around 2700-2400 BC, both cold on GISP.
Based on the ice core data, during the last glacial maximum there was very little ice in Greenland. The vast majority was added during the recent interglacial. (The current warm period.) It seems pretty clear that cold reduces the amount of ice and that warm increases it. It seems that everyone wants to ignore sublimation. When it is too cold for snow (ie, it is snowing someplace a bit warmer) ice is loss by direct evaporation. If you assume a change in the Gulf Stream, that would explain it – when it is “close”, it snows, when an ice shelf blocks it, it snows somewhere else and Greenland loses ice. This would also explain why ice accumulation doesn’t follow small temperature changes.
Your statement is just wrong. Completely wrong. Google the NEEM Greenland ice core for proof of what has changed in north central Greenland since the previous Eemian interglacial. IIRC, a shocking Eemian diminution of less than 200 meters in an ice sheet 2500 meters thick, for temps as much as 8C higher than now, back then.
I found a press release that agrees with your statement, but I can’t find the actual ice core data. I do have data from other Greenland cores that completely support my position. Do you have a link to actual NEEM core data? I am not convinced that it has been released yet since it is still being used to produce papers. This is where I normally get data.
ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/greenland/
The only NEEM data there covers only 60 years. Based on other papers, the Eemian ice is currently more than 2km below the present surface. Therefore, the real question is – Why? Or, if you accept your statement, What happened to the 2km of ice that was below the Eemian when it was laid down? Since it has been well established that Greenland is actually a basin surrounded by mountains, where did the older ice go? And before answering that, remember that there is a discontinuity near bead rock, and that the ice below the Eemian is thought to be very old – more than one million years old. Thus, the ice below the Eemian did not just melt and go away since even older ice is still below it.
To me, the obvious conclusion is that the Eemian snow fell on a nearly ice free Greenland – which disagrees with the current papers. Therefore, I disagree that my statement “is just wrong”. On the other hand, I am interested in logical arguments that explain anything I am missing.
Robert Clemenzi
The relevant paper is available here:
https://www.researchgate.net/publication/235228877_Eemian_interglacial_reconstructed_from_a_Greenland_folded_ice_core
Almost all available icecore datasets are archived here:
https://www.ncdc.noaa.gov/data-access/paleoclimatology-data/datasets/ice-core
Note however that not all NEEM data have been puiblished/archived yet. And I agree with Ristvan – you are utterly wrong. If there was little ice on Greenland during the last glaciation, how come the icecap then extended all the way to the edge of the continental shelf?
Thanks tty – that is a great link. However, I don’t agree with your interpretation of it. It claims that the Eemian ice was laid down at a higher altitude and 120 km away from its current position. It says nothing about the amount of ice during that time at the current drill position. Alpine glaciers typically form at high altitudes and flow down into green, ice free, valleys. Nothing in that paper supports the suggestion that the ice at the current drill site was as thick as it is today. In fact, the data they present suggests that the ice was only about 200m thick at the current drill site – the thickness of the undateable basement ice. Their data clearly shows that the Eemian ice underwent considerable deformation, then there was a period of no new ice, then the more recent horizontal layers were added on top. That kind of deformation *could* be caused by the failure of an alpine glacier which suddenly moved down hill. Or it could be caused by squeezing the ice between to mountains. (Think plate techtonics.) However, only one of these explains why older ice is missing under the initial Eemian ice. And that is the key point – where is the ice?
Two responses.
1. The Alaskan glaciers are in the south where there is a lot of snow, not in the much colder northern ice desert.
2. During the last glacial maximum, Canada had huge glaciers and Siberia had almost none. To be clear, the ice was concentrated on one part of the globe and missing on the other – at the same latitude.
(Sorry, my browser would not let me leave this comment under the one I was responding to.)
“During the last glacial maximum, Canada had huge glaciers and Siberia had almost none. To be clear, the ice was concentrated on one part of the globe and missing on the other – at the same latitude.”
We are talking about Greenland, and there the ice extended to the edge of the continental shelf, as proven by any number of drill cores, submarine end moraines etc.
And while it is true that eastern Siberia was largely ice-free, there was an enormous ice cap over the Barents and Kara Seas, Severnaya Zemlya and coastal Western Siberia.
“That kind of deformation *could* be caused by the failure of an alpine glacier which suddenly moved down hill.”
Could you kindly point out any hills of consequence anywhere near the NEEM site? That is rhetorical question, since one of the criteria for selecting the site was that the bedrock has very subdued relief over a large area. And alpine glaciers don’t “fail”, though they may surge. The only cases where they “fail” is when they end at an abrupt more or less vertical cliff face, but what you get then is not “deformed layers”, you get an “lcefall” and lot of crushed ice at the bottom (this is uncommon but I’ve seen it happen in South Georgia).
And a 200 m thick ice layer at NEEM site would be most remarkable since the bedrock is about 100 m below sea level. For one thing it would imply that climate in northern Greenland was much colder during the interglacial than during glaciations (which it wasn’t), since with the local lapse rate of about 7,5 deg/1000 m the Eemian temperature would be about 10 degrees lower than the temperature today at the same altitude (100 m a s l ).
Sorry, “fail” is obviously a bad word, “surge” is much better. How would you explain the folds? I assume that something caused compression. Since it occurred during a warm period followed by a period with no new ice, rapid advance of a recently lubricated glacier seems logical.
Ice to the shelf is irrelevant – there is sea ice all the way around Antarctica, but a significant part of the land is ice free at least part of the year.
Whether bed rock is below sea level today is irrelevant – there could have been isostatic rebound due to the loss of ice. Or maybe sea level was lower then. We know that sea level has risen more than 100 meters since the last glacial maximum.
At any rate, the real problem is “What happened to the ice under the Eemian layer?” Since the site is surrounded by mountains, it didn’t just get squeezed out and flow up hill into the sea.
I also saw that in the paper. No idea where it comes from. The current lapse rate is 6.5 K/km. I assume it is just a typo, but if you have a reference confirming the 7.5 K/km value, I would like to see it.
On the other hand, a dry wind blowing over a mountain ridge would warm almost 10 K/km as it sinks and melt a lot of ice.
When ice forms it gives up a lot of latent heat, warming the air. Air temperature is the effect, not the cause of ice formation.
Air has to be cooler than water, to suck out latent heat so water can become ice, so how does latent heat warm the air ??
Seems to me that at best, latent heat due to freezing of water, can slow down the cooling rate of the air, but I don’t see it warming the air. Heat goes from hot to cold. So if latent heat warmed the air, the loss of heat from the water would cease, and freezing would stop.
G
Remember the air over Antarctica and Greenland is extremely cold and dry, way below freezing. The warmer temps are still frigid.
https://rclutz.wordpress.com/2015/08/24/arctic-amplification/
? So where does the cold come from then? From beneath??
In my world the air has to be cold to make ice form. The fact that ‘latent heat’ has to be overcome asks for more cold air or to succeed in making ice. It will not get warmer when ice forms. Ice growth will just stop or reverse when the air temperature rises. Furthermore, I agree with what George E. Smith writes.
Yes, but remember that the ice actually forms high in the troposphere and sometimes quite far from where the snow finally falls.
just one question:
could it be the compression of the ice that disfigures the last 10000 years of the graph?
just to say that the deeper the ice the more it gets compressed. I suspect that at a certain depth it’s at it’s compression max (can’t be squeezed more).
could that be causing the discrepancy or was the ice accumulation graph adjusted to this constant ice depth related compression parameter?
if the ice data is unadjusted, compression might partially explain the discrepancy of the last 10000 years.
sorry it should be “ice accumulation data is unadjusted” in the last line
Yes, I was wondering what these mm data are. I suspect it is ice depth not mm of water content. ie this is not a clear measure of precipitation.
There is also the question of ice flow. The gradual glacial flow will evacuate ice from the centre towards the coast leading to thinning of the layers. There is also melting and run -off though moulins which must erode and carry away some deeper ice.
This will be happening all the time but is obviously masked during periods of ‘rapid’ change and only becomes apparent in the relatively stable conditions of the current interglacial.
As pressure increases with depth the air content becomes compressed and the volume ( and hence thickness ) of the ice reduces.
I think some further thought is needed before interpreting the ice accumulation data as a direct indication of precipitation, which it seems is what Willis is doing in seeing this as a reversal.
I’m not saying he’s wrong because I have not looked at the magnitudes but it seems that there are several processes that need to be considered before interpreting the data.
Perhaps it needs to be converted to accumulation in mm of water instead of ice which contains air.
It isn’t unadjusted. Glaciologists aren’t complete idiots.
A couple of reasons for the greater snowfall, when the climate warms.
Firstly, the very cold conditions on the high ice sheet, mean that the air contains very little moisture. And so there is very little precipitation, during the glacial maximum. But there is more moisture and precipitation, as the temperatures rise.
Secondly, the oceans were a long way away from the Greenland core sites, during the glacial maximum. But as the climate warmed, and the ice sheets melted, the moist air over the oceans got closer and closer to those drill sites.
Had we had ice cores from the Winsconsin ice sheet over the Great Lakes, during the glacial maximum, you may well have found that this region experienced the same snowfall as modern Greenland. So all that may have happened, is that the heavy snowfall band moved north, as the ice sheets melted, and finally arrived up into the highlands of Greenland. However, all that Wisconsin evidence has long gone, so we shall never know.
R
ralfellis you have a better understanding of Greenland climate then me. Now if l was told that the UK climate had been getting wetter but also cooler. Then that would have suggested to me that there had been a increase in areas of low pressure and rainfall turning up during the summer months. But am not sure if the same would be true for somewhere as far north as Greenland. Do you know the answer.?
Also there is a other very good reason why there is less snow when its very cold. The coldest weather mostly comes when high pressure is in charge.
I don’t think that the CO2 levels from ice cores could be correct. Varying little during the last glacial around the limit for C3 plants surviving. I would expect it to reflect boom and bust populations of plants.
Another reason for the temp/CO2 correlation could be there is a dependence of the measurement on snow fall. Greenlands too large results could be the higher snowfall.
Robert B,
CO2 levels in ice are quite correct: +/- 1.2 ppmv (1 sigma) for multiple samples at the same and adjacent ice cores, +/- 5 ppmv for ice cores with extreme differences in average temperature and accumulation rate.
The high accumulation Law Dome ice cores have an overlap of ~20 years (1960-1980) with the South Pole direct air measurements…
See:
http://www.antarcticglaciers.org/glaciers-and-climate/ice-cores/ice-core-basics/
and
http://courses.washington.edu/proxies/GHG.pdf
You still need to address why it doesn’t vary a lot when close to the threshold of C3 plants.
4-5% extra from humans is indigestible by Gaia but large changes in natural sinks makes bugger all difference? There is a large problem there.
Ferdinand:
You say
Ah, the beauty of a True Faith.
Your belief is truly indisputable, but ice core data is not.
Richard
Richard,
If you have any information that ice cores are not reflecting the real CO2 levels of ancient air, averaged over several years (10-600 years, depending of local snow accumulation), please give your undisputable source.
BTW, the ideas of the late Dr. Jaworowski on CO2 in ice cores are very disputable, to say the least…
Willis –
This gets interesting.
Your Fig 2 indicates a stadial/interstadial ice-sheet accumulation change of 4½x. Assuming little change in air circulation, that suggests the same air specific-humidity change, which corresponds to +22C above zero, or +17C below – very comparable to your Fig 1 range of +20C. The stadial N Atlantic can’t have been that cold.
I can only think of persistent sea-ice as a means of isolating ice-sheet from ocean. Does anyone have an estimate for the “fetch” of sea-ice needed to drop average air temperature by 10-20C? (the lower figure assumes a 10C cooler N Atlantic)
This substantial cooling would imply snow accumulation on such sea-ice – your Fig 2 hints at maybe 1-200 mm/yr (as ice). nb Cooler = *more* snow. Could this offset seasonal melt?
You may have a proxy for regional sea-ice extent.
This would explain your different Antarctic (Vostok) finding, as this applies to a region always remote from ocean. If this has merit, data from ice-cores on the Antarctic periphery should be comparable with Greenland.
Watching the Pineapple Express wave moisture over the west coast this week, I took a peek at similar moisture patterns aroung the globe. Look at Antarctica on earth.nullschool. The blue treads are moisture from the lower latitudes being mixed by the polar vortex.
Link http://earth.nullschool.net/#current/wind/isobaric/700hPa/overlay=total_precipitable_water/orthographic=-91.04,-92.66,403/loc=158.778,-63.360
Another interesting view …
AJB,
Thank you for the very interesting video.
One thing that caught my eye was central Africa with the pulsating cloud formation. Interesting indeed.
eysonu:
“One thing that caught my eye was central Africa with the pulsating cloud formation.”
Those are is the daily late afternoon thunderstorms you are seeing. You can see them over the Amazon and New Guinea as well.
Before using the earth.nullschool as an example you must first verify that the image is from observation; otherwise the image shown is from a model.
True. The data sets used are themselves the output of models combining measurements and interpolations by the source organizations.
eyesonu, follow the midday sun in this one (best viewed full screen in HD) …
Just noting that the Greenland ice core temperatures in the above chart are calculated based on a model of the borehole temperatures. The borehole models can have a wide variation which changes the numbers by a great amount.
If one used the standard formula for how the dO18 isotopes vary by temperature in Greenland, the ice age differentials would only be about 9.0C rather than the 20.0C used in the accepted borehole-dO18 conversion.
Since in Antarctic ice cores, they don’t use borehole models and the temperature change is only 10.0C, the standard 2X polar amplification factor, I’m assuming the Greenland ice core temperature conversion model from boreholes is probably wrong and it should only be 9.0C.
If you look at the assumptions involved in going from d18O to temperature (NOAA website used to have a concise description, but it seems to have gone the way of all useful information), you will have to conclude that their temperatures are a rather coarse approximation. The trends are almost certainly real, but the absolute values of temperature are not.
It’s complicated further by the fact that many of the Antarctic ice-core temperatures are calculated using deuterium ratios, while 18O is more popular in Greenland, making north-south comparisons even trickier.
It’s all really good data, but it needs to be used with appropriate care.
There is a quite good book by Dansgaard on the history of ice-core research, and how the techinque was developed: “Frozen Annals”. It is available online here:
http://www.iceandclimate.nbi.ku.dk/publications/FrozenAnnals.pdf
I strongly recommend it. It’s quite an interesting read and answers to most of the questions asked above can be found in it.
Bill,
As a former minerals guy used to drilling holes on land, I have reservations about this borehole temperature method. The mind model I use is mostly covered generally by Prensky 1992 http://www.sprensky.com/publishd/temper2.html and more closely Tolwinski 2008 http://suztw.com/projects/geos582/BoreholePrez.pdf
Objections to the borehole T reconstruction method are in 2 main classes, being probability of T records being preserved in core (or walls of holes) without change such as from circulating ground waters; and the physics of heat flow and the math that follows and goes into estimates of past temperatures.
Note that some mathematical inversions do not give unique answers so subjective choices have to be made. This can limit the accuracy of calculated temperatures which are already stressed by poor signal:noise. Other reservations are noted by Kilty http://www.kilty.com/pdfs/t-d.pdf
The general case usually gives temperature reconstruction curves that look similar in gross shape all over the globe. That graph shape is almost always a concave curve sloping down in the direction of older = colder, sometimes with a small, recent upwards bump imposed.
Ice core is not rock core, so my mental rock pictures from the above reference types have to be modified.
For years I have tried to work out if anything is going wrong. I wonder loosely if there is enough attention paid to the effect of past extreme above-ground temperatures wiping out the earlier gradient records and imposing a clean sheet to be filled in afterwards. Example, a very cold, long historical above-ground period would allow local geothermal heat to fill the most upper part of the core, obliterating earlier fingerprints.
For now, my preference is to disregard borehole temperature reconstructions when there are important policy consequences. It is still an immature research tool IMO and not a strong policy advocate method.
I agree, I was quite surprised when I first read about this method.
There are clearly several ways a final profile could result from different historical changes so a reverse mapping is not unique.
At least boreholes in rock are a fairly constant geometry of material. Since ice is actually flowing and accumulating over the period of interest this has to become a very uncertain calculation.
Given the very poor S/N ratio the ambiguities are amplified.
It should be noted that temperature measurement based on d15N has confirmed the large temperature swings in Greenland (see e. g. https://www.researchgate.net/publication/270574474_Temperature_reconstruction_from_10_to_120_kyr_b2k_from_the_NGRIP_ice_core)
Hi Willis,
Maybe there are two simultaneous factors in action in Greenland: the increase in snowfall with rising temperatures, and an opposing influence (at least at warmer temperatures where summertime surface melt is possible) of high latitude summertime solar intensity, where falling summertime solar intensity increases net accumulation because of less summertime surface melt. Summertime solar intensity above 60N has been continuously falling over the Holocene, in parallel with the rising net accumulation.
Surface melt is very unusual near the center of the icecap even during interglacials, and melting events are very conspicuous in the ice cores. In short: no, melting is not an important factor.
..Anthony is going to get blamed for this, I just know it !
http://video.foxnews.com/v/4795368682001/glacier-ice-bridge-collapses-in-dramatic-fashion/?intcmp=hpvid1#sp=show-clips
A passing question. The last 10,000 years appear to be amazingly stable. In the previous 40,000 years, there were fairly regular 15 degree swings. Any idea why? I know you are just showing the data. But your graph certainly raises some questions. We seem overdue for a big drop in temperature or are we in an unusual zone of stability for some reason? It may be an unanswerable question but very curious.
Ocean Currents (AMOC, Gulf Stream,…) have two modes. Marginally unstable during interglacials (extra heat driving engine) and stable during glacials (but can be flipped on and off by small tidal, solar, orbital, whatever drivers), but prone to occasional flips to the warm mode.
https://chiefio.wordpress.com/2012/12/15/d-o-ride-my-see-saw-mr-bond/
Paper with specifics:
http://www.pik-potsdam.de/~stefan/Publications/Nature/rapid.pdf
Thanks E.M.
l think a key point to understand is that the ice ages are to a large extent a regional climate change, and its this that lead to the huge build up of the ice sheets. Because when limited regions become much colder but the rest of the globe remains fairly warm. Then there is going to be very intense weather activity over these colder regions. Because as the warm moist air hits these cold regions then large amounts of snowfall are going to be dumped over these cold regions. So leading up to the large build up of the ice sheets.
Willis, I recall from my an early glaciology course that seasonality of both temperature and precipitation is critical to ice accumulation and the effects of seasonality vary by latitude.
So annual or longer average figures are not going to reveal how ice accumulation works.
Also, Greenland ice accumulates mostly in an enclosed basin, while Antarctic ice accumulates around the perimeter, possibly related to the effect of the sizes of the land masses on average distances from the water masses.
The questions you are addressing are diabolically complex.
Willis, a friendly suggestion that you change “the warmer, the wetter” to read ” the less FREAKING COLD, the wetter”.
To whit: the ice core data comes from Summit camp.
“Summit Camp, also Summit Station, is a year-round research station on the apex of the Greenland Ice Sheet. …The station is located 3,216 metres (10,551 ft) above sea level. … The climate is classified as polar, and the weather is highly variable. Typical daily maximum temperatures at Summit Camp are around −35 °C (−31 °F) in winter (January) and −10 °C (14 °F) in summer (July). Winter minimum temperatures are typically about −45 °C (−49 °F) and only rarely exceed −20 °C (−4 °F). Annual precipitation is about 3,000 mm (118.1 in), much of which falls as sleet or snow, which is possible in any month. Inland, the snow line in summer is at an altitude of about 300 m (984 ft). The highest temperature at Summit Camp was 3.6 °C (38.5 °F), recorded on July 16, 2012; the lowest recorded temperature is −67.2 °C (−89.0 °F).” https://en.wikipedia.org/wiki/Summit_Camp
The record high temperature, 3.6 °C above freezing, apparently lasted all of 4 days starting July 8, 2012. They try to characterize this as a ‘melt’.
Many times have I skied on a 3.6°C thaw day following an overnight low of -10°C and seen the snow pack produce zero run off. The snow must consolidate to the saturation point before it will produce any run off. Above freezing for four 24hr cycles and maybe there is a chance for some runoff.
It will be taking a long time to melt all those meters of ice at summer temperatures that average a high of -11 °C during June and July and -14 °C in August. A global warming of 3 °C still leaves us at a sweltering -8 °C. That would be a nice blue/green wax day for skiing?
Enjoy the rain. Stay safe.
Willis:
For the last 9,000 years or so, the situation is reversed. Temperatures have been steadily dropping, but the ice accumulation has been rising …
Temperature as measured as δ180 in the ice core ice is mainly the temperature from where the water vapor is transformed into snow, high in the troposphere.
Amount of water vapor and thus precipitation is mainly caused by ocean surface temperatures. There may be a long lag between the two, where high troposphere temperature is slowly cooling after a maximum, while the ocean surface still is slowly warming (including the deep ocean return) out of the previous glacial period…
Even according to new greenhouse theory and observation, there should be no warming over Greenland highland. Something like CO2 cooling over Antarctica.
“However, above Antarctica the top-of-atmosphere (TOA) spectra look different; the spectra yield a maximum in the CO2 band [Thomas and Stamnes, 1999, Figure 1.2c]. This observation is consistent with the finding that in the interior of the Antarctic continent the surface is often colder than the stratosphere; therefore, the emission from the stratospheric CO2 is higher than the emission from the surface.”
How increasing CO2 leads to an increased negative greenhouse effect in Antarctica.
Authors Holger Schmithüsen, Justus Notholt, Gert König-Langlo, Peter Lemke,Thomas Jung
Published: 14 December 2015
Based on this graph, I would have thought that the Antarctic Stratosphere was ALWAYS warmer than the surface.
http://www.cpc.ncep.noaa.gov/products/stratosphere/polar/gif_files/time_p_t90s_2015.png
Willis, if you isolate the GRISP data for the last 20 ka and compare the period before an after about 10,000 BP, the “warmer-wetter” pattern breaks down at the point where temperatures reach modern levels. I think that one possibility is that the glacials are simply immensely drier than than interstadials. That would seems to suggest a strange attractor operating in the shift between glacial and interglacial periods that is quasi-periodical. The change in periodicity between the Pliocene and Pleistocene glacial-interglacial shifts actually might resemble a Lorenz “butterfly.” I don’t know if that can be resolved for earlier interstadials well enough to determine if they resemble the present climate pattern.
Mr. Eschenbach, with the caveat that I have not the smallest fraction of your understanding in this field, and also with the assumption that it is true that warmer temps lead to greater amounts of polar ice, is this not yet another example of your “thermostat hypothesis” regarding earth’s temperature regulation? Not emergent phenomena per se, but something similar, this time affecting the poles rather than the tropics. Just a thought–what do you say? (P.S.: I know you will not consider this question to be stupid.)
Its a mistake to believe that Temperature alone accounts for increased rainfall. The Earth is a big interconnected set of heat engines and they reorganize occasionally to reach a more stable and efficient configuration. Its like trying to consider the effects of CO2 in the atmosphere from observing it in a laboratory – yep, it definitely causes warming in a test tube but bring it into the chaos we call Earth and its hard to predict all the interactions. It likely causes additional warming but its anyone guess as to how much.
Warmer temperatures also mean less temperature gradients – on average – because the cold areas warm faster than the warm ones (or so models tell us). Warmer air CAN hold more water IF there is sufficient bodies of water nearby that evaporate – so just because a place gets warmer is no guarantee its going to get wetter.
Understanding the Greenland ice sheet, or the Antarctica one, or the desert regions can’t be done on temperature alone – one really needs to understand how both ocean currents and air currents reorganize to predict what becomes of the target area. If the Hadley cells break down, or contract or stretch – due to temperature changes then that is going to have a tremendous impact to large areas. The same goes for ocean currents. if they relocate its going to dramatically change rainfall patterns.
My point is you may not be able to simply line up two (or three, or ten) variables and see a simple pattern emerge. Climate is so very complex, its a wonder we can predict 10 years into the future let alone 100 years…Oh, wait, we can’t. 🙂