The ice age and the ice volume problem

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Multiple evidence suggest that the Pleistocene epoch (2.56 Million years - 11.6 thousand years) was about waxing and waning Ice sheets with the pace of the milankovitch wobbles superimposed on the earth orbit.

One intriguing element showing this is a multiple multi-millenium cycle in variation of isotope ratios in foraminifera remains in the ocean sediments, which all show the same pattern, which is also matched in the ice cores of Antarctica.

This cyclic variation in isotopes is thought to be basin effect in pace with the waxing and waning of the ice sheets. Evaporation favors light isotopes, escaping much more easily from the liquid condition into gas. Hence if the ice sheets are growing with more light isotopes, the concentration of heavy isotopes in the ocean is increasing. And it is thought that this is reflected in the isotope ratio in the biota sediments. This is considered to be easily quantifiable and hence the isotope ratios in the ocean cores are considered to be a proxy for ice volume.

Bintanja et al 2002 model those quantities for the last glacial maximum as function of contribution to sea level rise and propose:

Model simulations show that at the last glacial maximum (LGM) a volume of ice representing about 65 m of sea level equivalent is stored on the Eurasian continent, whereas North America stores 42 m. The other regions (Greenland, Tibet, South-America and Antarctica) contribute about 17 m to global sea level lowering at the LGM compared to present day
Now let’s focus on that 65 meters stored in the Eurasian continent. Bintanja shows the essence of the publication on his webside

http://www.phys.uu.nl/~bintanja/Fig_lgm.jpg
 
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Note that Bintanja et al merely propose an outcome of a model run at state:

If properly validated against field data, model results complement observations, and may even give directions to field studies.
There is the key, "if properly validated"; has this ever been properly validated against field data?

Take for instance the ice sheet height, the domes on Russia seem to exceed 4000 meter height. That's of Antarctic proportion and the oldest ice in the EPICA dome C cores is at least 800,000 years old. The 3000 meters of Greenland, a much faster accumulating ice sheet is estimated to be 130 - 200,000 years old

So how does that compare to the accumulation time of that Eurasian ice sheet?

http://www.phys.uu.nl/~bintanja/Fig2a3.jpg

So that means that the hypothetical Eurasian ice grew to one and a half time the Greenland ice sheet height in about half the time, in an area with a logically continental arid climate; and the higher, the more arid. How does that compare to reality?
 
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Xnn

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Can a free copy of this paper be make available.
 
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Perhaps indeed
 

Xnn

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According to their website, it is a crude model:

The model time step is 4 years.
So, there were no seasons in the model; just 4 year averages.

The radiation component includes snow depth and surface albedo, a variable that varies greatly (0.2 for soil, 0.45 for ice and 0.80 for dry snow).
Albedo changes are much more complicated than that. Remember melt ponds!

Changes in precipitation owing to changes in atmospheric circulation have been ignored.
Everyone should realize that mile high ice sheets impact circulation patterns big time.

In this particular experiment, there is more ice in Eurasia than in North America, which does not agree with what most observations suggest.
and in conclusion.

The most likely mechanism by which this aspect-ratio problem may be solved is basal sliding, as enhanced basal sliding tends to make ice sheets thinner. Another possibility is that the ice sheets at LGM were not in steady-state.
 
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Anyway, the proof is in the pudding.

Svendsen et al 2004, also here

from the abstract:

The maximum limits of the Eurasian ice sheets during four glaciations have been reconstructed: (1) the Late Saalian (>140 ka), (2) the Early Weichselian (100–80 ka), (3) the Middle Weichselian (60–50 ka) and (4) the Late Weichselian (25–15 ka). ...The Barents-Kara Ice Sheet got progressively smaller during each glaciation, whereas the dimensions of the Scandinavian Ice Sheet increased. During the last Ice Age the Barents-Kara Ice Sheet attained its maximum size as early as 90–80,000 years ago when the ice front reached far onto the continent. A regrowth of the ice sheets occurred during the early Middle Weichselian, culminating about 60–50,000 years ago. During the Late Weichselian the Barents-Kara Ice Sheet did not reach the mainland east of the Kanin Peninsula, with the exception of the NW fringe of Taimyr.
Looks a bit neutral or even the opposite when comparing to the predicted ice sheet volume:

http://www.phys.uu.nl/~bintanja/Fig2a3.jpg
starting off small and growing bigger.

Also the readvances would have had not too much time to attain the heights as predicted by Bintanja et al. Instead, there were mammoths walking, where they predicted the ice sheets.

In a word, not looking good, but Xnn already suspected that in his post.

According to their website, it is a crude model:
Yes but calculating ice volume does not require a model, just an empiric basic function with isotope value as main variable, the model is more a simulation to see where the ice would grow

Note that Bintanja et al basically did nothing wrong here. They just took an hypothesis and formulated a prediction from that. Only the last step was missing, testing against reality, alas, another beautiful theory destroyed by an ugly fact.
 
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Here is a rough projection of the field results plot of the LGM of Svendsen et al in red aganst the computations of Bintanja et al

2884cnt.jpg


Considired that also the dome of Svendsen et all is around 2500 meters versus 4000 meters for Bintanja, it is clear that a lot of ice volume is missing, seriously challenging one of the fundamentals of paleo climatology, that maritieme isotopes are a proxy for ice volume.
 

Xnn

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... it is clear that a lot of ice volume is missing, seriously challenging one of the fundamentals of paleo climatology, that maritieme isotopes are a proxy for ice volume.

I think it is more likely their simplifying assumption that atmospheric circulation is not altered by huge ice sheets is obviously wrong. In addition, they did not have a climate model included. To do so, takes lots of time and money.
 
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I think it is more likely their simplifying assumption that atmospheric circulation is not altered by huge ice sheets is obviously wrong. In addition, they did not have a climate model included. To do so, takes lots of time and money.
Certainly, but that's not the point. The essence is that it is a checksum problem. No matter where ice sheets would or would not be accumulating and how that would happen; everybody would require so many cubic kilometers ice in total to fit in the total sum of isotopes/sea level/ice volume formulas, regardless of the sophistocation of their models. But there were mammoths no ice. For instance the most easterly part of the red outlined LGM area according to Svendsen et al is known as the Taimyr peninsula.
2884cnt.jpg


Check what happened there just before the Last Glacial Maximum. For instance, Mol et al 2006 also outlined http://www.yukonmuseums.ca/mammoth/abstrmol-mor.htm [Broken].

Fishhook Mammoth

The Fishhook Mammoth is a 20,620 ± 70 BP (24.7 Ka Cal BP) old woolly mammoth carcass (Mol et al. 2001, MacPhee et al. 2002). It was discovered in the estuary of the Upper Taimyra River,....

The matrix of the stomach sample from the Fishhook Mammoth consisted of a mass of unidentifiable grassy material. Among the identifiable remains were leaves of Dryas octopetala (dryad), Salix sp. (willow), Betula nana (dwarf birch), Vaccinium species, a catkin of Alnus fruticosa (alder), and needles of Larix (larch)....

The find of Larix is especially interesting, because the site where the Fishhook Mammoth was found is situated at about 200 kilometres north of the present timber line.
Trees on places presently well north of the present treeline on a place where others expect the ice accumulating. Seems that something is wrong here.
 
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Addendum,

It may be interesting to see how the hypothesis was develloped about the deep sea isotopes being a proxy for total ice sheet volume. It was thought out by Late Nick Shackleton but it has always been plagued by complications like this. The attempt of Bintanja et al for linking assumed sea levels to ice volume is one of the latest I know about. However as the fieldwork shows, there wasn't enough ice volume to suit the assumptions.

It could be that the isotope signal reflected in the carbonate shells of the foraminifera is not only a function of the isotopes in the sea water but also functions of unknown changing conditions and we know that the oceans did unexpected things during the last Glacial transition for instance Marchitto et al 2007
 

Xnn

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The essence is that it is a checksum problem. No matter where ice sheets would or would not be accumulating and how that would happen; everybody would require so many cubic kilometers ice in total to fit in the total sum of isotopes/sea level/ice volume formulas, regardless of the sophistocation of their models.
No; my read from the website, is that they assumed current atmospheric circulation pattens and then varied temperature in proportion to the Antartic ice record. And they did it in 4 year steps! No days, no nights, no seasons, just 4 year averages and without any variation in circulation. And they have already realized the serious shortcomings of their model.

Also, they don't discuss it, but I can also see that they made huge simplyfying assumptions about albedo.

So, they have a lot of work to do. Eventually, I'm sure if they get the funding, there will be future attempts to improve their model and compare it against independant data. At this point in time, it is obviously very crude, and I wouldn't be surprised if somebody else has a better model.
 
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No; my read from the website, is that they assumed current atmospheric circulation pattens and then varied temperature in proportion to the Antartic ice record. And they did it in 4 year steps! No days, no nights, no seasons, just 4 year averages and without any variation in circulation. And they have already realized the serious shortcomings of their model.

Also, they don't discuss it, but I can also see that they made huge simplyfying assumptions about albedo.

So, they have a lot of work to do. Eventually, I'm sure if they get the funding, there will be future attempts to improve their model and compare it against independant data. At this point in time, it is obviously very crude, and I wouldn't be surprised if somebody else has a better model.
But what is on that webside is irrelevant, they could have everything as right as possible with the most modern means and yet they still would have to put rougly 3-4 times more ice on the Eurasian continent to get the checksum matching the hypothesis.
 

Xnn

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Andre;

That paper by Williams is 28 years old!

There has to be something more recent than that.
 
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Andre;

That paper by Williams is 28 years old!

There has to be something more recent than that.

The idea was to give some illustration of the problems around the isotopes - ice volume hypothesis.
 
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Trees on places presently well north of the present treeline on a place where others expect the ice accumulating. Seems that something is wrong here.
The idea of a stronger Gulf Stream reaching the Arctic Basin can explain this scenario.

Andre;

That paper by Williams is 28 years old!

There has to be something more recent than that.
I agree.
 

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