Warm Arctic AND Glaciers At The Same Time?

Mammo

I've recently come to believe in the possibility of the Gulf Stream being stronger in the recent past and warming the Arctic Ocean. It would explain why Mammoth remains are found on the New Siberian Islands, which lie between the Arctic coast of Siberia and the North Pole. Could a decrease in the Earth's orbital eccentricity from around 40,000 years ago have reduced this meridianal heat transfer mechanism to the levels of today? Is a stronger Gulf Stream which warms the Arctic been in existence from at least the last interglacial, 120,000 years ago, until relatively recently? If so, presumably cold currents must have circulated around Greenland, North America and Europe, since ice sheets are known to have existed from about this time. A warm Arctic AND ice sheets over North America and Europe? Is this speculation complete madness, or is it simply the unknown truth?

Andre

Welcome Mammo

It's probably a lot more complex than that.

This chart depicts insect remains and bones rigtht in the middle of that area,

source: H.W. Hubberten et al. 2004 Quaternary Science Reviews 23 (2004) 1333–1357 (page 1339)



The caption reads:

Obviously there have been sudden and large changes in the climate of that area while the Milankovitch cycles are very gradually. Note also that sometimes summers used to warmer than nowadays

However this is the assumed maximum extend of the Last Glacial Maximum. some 20,000 - 15,000 years ago or indicated as 20 - 15 Ka BP (Before Present).



(Hubberten et al 2004 Page 1335)
Yellow dots are the research sites. Note that several mammoths have been found in the far north around "2"

Andre

Now, there is a bit of a problem with that insect diagram and mammal fossils. Any idea, Anybody?

edit: Let's say that I would have made a serious remark about it, should I have reviewed it (which I'm doing nowadays )

Andre

I mean, should you be temped to compare/corrollate the chronology of the climate with the nearby Greenland Ice cores, you'd get this:



(source Alley 2000)

versus Hubberten et al (2004) fig 6, rotated and mirrorred:



You'd probably be happy with the 'same' warming around 15-14,000 years ago, although the missing (or delay?) of the Younger Dryas is a bit puzzling.

But you cannot compare the two this way, that's a serious error. Why?? (explained that several times).

Mammo

Hi Andre, you already know me as 'common_sense_seeker' from Sciforums (Alan). I've been re-reading the Hapgood chapters from The Path Of The Pole. It's quite funny now that we are so aware of continental drift and plate tectonics. But he did make some very interesting claims about a warm Arctic. Have you managed to find any confirmational evidence for warm unglaciated conditions in Baffin Island and Bank Island during the Wisconsin ice age? I was also very interested in the Stone Age settlements found in the New Siberian Islands. Are Hapgood's claims valid?

Thanks for the given information and links. It certainly looks a lot more complicated, like you say. I'll have to work through it all and begin to get a picture of the latest findings. Are there deep sea sediment cores from these areas?

BTW, why isn't Greenland shown to be glaciated in the map of the LGM?

Mammo

As well as the variations in summer radiation due to orbital forcing, which can vary drastically with in orders of a thousand years, there is also the millennial cycle to consider. The orbital eccentricity variation could also be amplified by ocean currents transfering heat from the equator to the higher latitudes. My consideration of rapidly altering Gulf Stream and Pacific warm currents is still in contention for being a major factor in the climate of the region.

Maureen Raymo makes an interesting comment on the Thermohaline Circulation of the North Atlantic. http://maureenraymo.com/current_projects.php

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Mammo

I have a problem with the abstract from the given report. They say that the region became progressively cooler from 30kya and that glaciation occurred. But it is common knowledge that the effect of glaciation is primarily due to low summer temperatures! Milankovitch cycles clearly predict a sudden drop in nothern hemisphere summer radiation from 30kya, reduced levels lasting around 15,000 years. I agree that the reason for the rest of Eurasia remaining unglaciated is due to low precipitation rates.

Andre

Addressing this question first, Alan otherwise it gets too confusing.

The answer can be seen in the top left of fig 6 of Hubberten et al 2004:

Hence the dates are uncalibrated carbon dates. Although carbon dating is a reliable tool nowadays, it does not produce the date directly because of many complications in the ¹⁴C cycle, especially the ratio of ¹⁴C in atmospheric CO2 at the the time of the photosynthesis. But these problems have been solved now and there are calibration tables based on both counting annual layers and carbon dating them. The newest one is IntCal04. So if we want to synchronize those both graphs, the layer counted ice cores versus the carbon dated sediments we must calibrate those dates first. Here is the main table. We see that 14,000 and 15,000 ¹⁴C BP calibrate to about 16,700 and 18,500 Calendar years BP (Cal BP) and gone is our synchronous warming.

I would contend that the major lesson here is that our basic understanding of climate changes in the past is insufficient to draw any kind of conclusions at all and that we really should scrutinize all the data again with the latest additional techniques.

Incidently should I have been reviewing then I would have problems putting the highly variable carbon dating scale on a pure linear plot, this way the real graphs are distorted. So they should have calibrated all dates individually first before processing them further although it might not reduce the anomaly. Of course Intcal04 was not available then but the previous IntCal98 was, and the difference is not great.

Andre

No Alan, you turn the scientific method inside out. Not uncommon these days. The Milankovitch idea is hypothesis or even a theory that should be able to do predictions what to expect. If the expectation is not in agreement with what they find, then you can only scrutinize their data, methods and information once more. But if their work is good, you have to adapt your expectation, which means changing the hypothesis.

Andre

I would concur but it's not that we can see exactly what happened, and what is cause and what is effect? but I have an interesting studie here:



Edit periods mentioned in the graph:

Hol is Holocene
YD is Younger Dryas
A is Allerod
B is Bolling
H1 is Heinrich event #1 (massive ice berg rafting)
LGM is Last Glacial Maximum

We see here that in the ice ages the radiocarbon (14C) in the CO2 of the ocean waters was pretty stratisfied. Most in the higher layers, depletion in the bottom waters. To me that means that the bottom waters were very old and did not hardly mix (radiocarbon decayed without replenishment). We see gradual changes, apparently Then suddenly, almost overnight, things changed at the beginning of the 'warm' Bolling Allerod stadial at around 14,500 years ago and again during the 'cold' Younger Dryas oscilation. also it looks a lot faster than the normal ocean inertia. But we end up with well mixed 14C in the waters. I wonder what forces were required to get these changes.

It's from here:
Robinson, L.F, J.F. Adkins, L.D. Keigwin, J. Southon, D.P. Fernandez, S-L Wang, D.S. Scheirer 2005 Radiocarbon Variability in the Western North Atlantic During the Last Deglaciation, Science, Vol 310, 2 December pp 1469-1473

http://www.whoi.edu/cms/files/Robins...2005_21687.pdf

Mammo

This thread is starting to get very complicated. Lets just concentrate on the Milankovitch prediction for glaciation starting from around 30kya B.P due to a decrease in the summer insolation and reduced orbital eccentricity. It's in perfect agreement in my opinion. I have reproduced a photograph of beach terraces and the corresponding orbital forcing data (Imbrie and Imbrie). The geologist Lawrence Dillon "found that the essential condition governing the growth of an ice sheet is not the average year-round temperature nor the average snowfall but the average temperature during the summer. He points out that no ice sheets form at the present time in areas with average summer temperatures of 45'F or higher and suggests that this situation must have also been true in the past."

Sustained high sea levels are recorded by the formation of coral terraces. These are times of low glaciation, since the seawater is not 'locked up' in the form of snow, and advancing the ice sheet. The three terraces given below match up with times of high summer radiation, implying that winter snowfall in the higher latitudes was all melted during the warm summer temperatures.

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Mammo

Andre, have you heard about the genome sequencing programme for the Siberian Mammoth? http://live.psu.edu/story/36123. They have worked out that one species died out around 45,000 years ago. I believe that this could be due to a decline in the orbital eccentricity, which reduced the intensity of warm currents reaching the Arctic. Just an idea.

Andre

The problem is that the pace at which we progress with new & improved data and information has a tendency to falsify old thoughts. Imbrie and Imbrie was the best available in 1979, however with polishing the data, things got nasty as Karner and Muller (yes Richard) explain here. published

Guess why I repeat that on every possible occasion? Now almost another decade further on, that's still very true. Falsifying old thoughts is fine but yet those thoughts linger on and on as you just showed. There is a lot more about that

Mammo

Firstly, thanks for the interesting report which challenges Imbrie & Imbrie's coral terraces graph that I gave earlier. I wasn't aware of this angle of debate, although I quickly knew what was causing the confusion. The first line of the report goes:

"According to the Milankovitch theory, changes in the incident solar radiation, called insolation, in the Northern Hemisphere provide the driving force for global glacial cycles."

This pre-supposes that the forcing mechanism due to changing eccentricity is solar radiation. This is where the confusion lies. There is a possible second mechanism for global temperature forcing which is independent of insolation. This is due to gravitational tidal force. It is only the amplifying mechanism which is unknown. I have a simple but effective speculation which would account for this amplification. It is linked to the 'gravity problem' in physics. If it is assumed that the gravitational acceleration of the Earth is non-linear in response to the Sun's gravitational field, much larger changes in tidal force are possible with changing eccentricity. The non-linearity is due to the increasing entropy of matter towards the center of the Earth. This means that matter is 'more orderly' at the inner core, and so will experience a greater gravitational pull compared to the ordinary baryonic matter of the outer Earth. When the Earth is closer to the Sun, even by only a few percent, a much larger Earth bulge is possible than previously thought by conventional wisdom. Therfore a new name needs to be applied to this idea, since it isn't just insolation which is the proposed driving force but a combination of insolation and tidal force. Perhaps it should be called Milankovitch-Mammo theory. The effect of this largely varying tidal force is further complicated due to the combined effect of ocean currents. This means that further amplification is possible due to the transport of heat from the equator to the poles. It is the re-distribution of heat via ocean currents which is the main driving factor in the 100,000 eccentricity glacial cycle.

The idea can also be used to explain the millennial cycle of unknown origin and driving force. The 1,800 year oceanic tidal cycle was explored by Charles D. Keeling and Timothy P. Whorf. article

Mammo

I suspect that there is a lot of rivalry between Californian Universities. The article authors seem uncharitable to suggest that 'Milankovitch supporters' only consider insolation as the driver of glacial ages. I've just come across a 2007 report from New Zealand which supports the basic idea of orbital forcing due to varying insolation. article

"..Southern Hemisphere summer insolation minima suggests that orbital forcing has played a first-order role in regulating glacial extent in New Zealand."

BTW, this movie here shows how the Arctic ice advances and retreats at the present time.

Andre

That's not the spirit. We try to talk about ideas not events or persons.

But if you look at the big picture throughout the whole Pleistocene there will show up some problems (expanding tomorrow at home).

Mammo

Sorry Andre, I may have been slightly negative in my responses. I have only just printed out the above report, since I've just realised it's high degree of relevance to my original post. What I have noticed is that the tundra warm periods seem to correspond with Heinrich Events. There seems to be a warming response in the Arctic prior to the ice-rafted debris (IRD) record. Events H5 (around 45,000 B.P) and H4 (around 38,000 B.P) match with '2', '3' and '4' of the above graph. Do you concur with this? The Mammoth data that I had originally also bears some resemblance to these events. I beginning to build a picture of what's happening. An increase in the Gulf Stream could trigger extra warming due to the melting of the ice cap. This effect has been studied by Vladimir Semenov article and would explain the additional heat needed to lubricate the Greenland icesheets as well as an increase in the strength and height of the Labrador current (since this would be the only outlet). What do you think? (Incidentally, it would have been nice to see the above graph continue beyond 60kya)

A few simplistic questions Andre: (1) If northern Siberia was a lot warmer than today during periods of the last ice age, what mechanism other than an increase in the Gulf Stream could have caused it? (2) During the last ice age, why wasn't there a Eurasian Ice sheet prior to 30ka BP, in line with the North American ice sheet?

I have been slow in understanding the calibrated/uncalibrated argument. This is new to me, but I'm looking into it. Thanks for being so patient with me. I'm learning just as fast as I can.