Amazon Data Contradicts Glacial Aridity Hypothesis Of The Ice Age

  • #26
Not much. There have always been different estimates considered side by side, but they are pretty similar in broad details.

You may be mislead by the different projections, but the differences in the two glacial extents shown are pretty small. Some differences are not surprising, especially given that there has never been one gold standard extent, but rather various proposals by different researchers.

Cheers -- sylas
I wouldn't estimate the difference between the two as "pretty small". Extremely significant in fact. Studies have concluded that the Gulf Stream must have entered the Arctic basin during glaciation and kept some areas ice free. The standard model doesn't account for this as far as I'm aware.
 
  • #27
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The EuroAsian glaciers waxed and wanned a great deal during the ice ages. Europe seems to be more succeptible to the Milankovitch cycles (with a 5,000 year lag) than the North American glaciers were. [The Milankovitch Cycles indicate that the ice ages should only last around 20,000 to 40,000 years (varying) at a time rather than the 100,000 year timeline which has happened in the last 1 million years).

The extent of the glaciation in Russia also waxed and wanned and the extent reconstruction probably depends somewhat on the time period the evidence was taken from.

(Just an aside here, but if one looks at how far out into the Arctic Ocean, the EuroAsian continental shelf goes - past Spitzbergen and the Franz-Josef Land islands - it is possible that the continental ice sheets extended all the way to the shelves, (as one reconstruction above shows) far out into the Arctic Ocean. The weight of the glaciers might have depressed the land so much that it still has not rebounded sufficiently yet to go above sea level. Europe and Asia are actually much bigger continents than it looks on the current maps and what it may have looked like 3 million years ago before the ice ages started).

Here is a nice paper on the time-evolution of the glaciers in Europe in the last ice age. It is more concentrated on Europe than Russia but one can see how the glaciers probably increased and decreased over Russia at different times as well.

"Ice marginal fluctuations during the Weichselian glaciation in Fennoscandia, a literature review."
Hanna Lokrantz, Gustav Sohlenius
Geological Survey of Sweden (SGU)

http://www.skb.se/upload/publications/pdf/TR-06-36webb.pdf

A nice illustration from the paper.

http://img688.imageshack.us/img688/9750/europeglacialcycles.png [Broken]
 
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  • #28
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See for a more extensive reconstruction of the Early Weichselian glaciation also this study

Also considering the last glacial maximum, we have also discussed some of the complications in this thread.
 
  • #29
I'm aware of the mega-grasers and their predators and the hypothesis of aridity leading to more savannah. The trouble is that it doesn't account for twice-size Amazonian rainforest monkeys. Your hand-waving dismissal of the finds as "not unusual" is completey unfounded imo. The finds are completely counter intuitive and requires a firm explanation.
Treetop monkey eat fruit not grass. Aridity doesn't make fruit yield double, only extra sunshine does.
 
  • #30
Skyhunter
Treetop monkey eat fruit not grass. Aridity doesn't make fruit yield double, only extra sunshine does.
Why are the mod's letting you get away with such nonsense.

You keep making this ridiculous claim that two big monkey heads prove that the Sun was hotter during the late Pleistocene glaciation.

Monkey heads are not evidence of solar activity. http://en.wikipedia.org/wiki/Beryllium-10" [Broken] concentrations fluctuate with the strength of the solar wind, which governs the number of galactic cosmic rays in the upper atmosphere available for beryllium-10 production. The solar wind is a direct indicator of solar intensity.

You need more than monkey heads and a vague theory that a more active Sun cools the ocean by reversing convection in order to call into doubt the isotopic evidence.

The idea is as preposterous as the statement that only extra sunshine can double a trees fruit production.

Disclaimer - Big fan of http://97bottles.com/breweries/us/ca/berkeley/triple-rock-brewery-and-alehouse/monkey-head/" [Broken].
 
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  • #31
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Why are the mod's letting you get away with such nonsense.

You keep making this ridiculous claim that two big monkey heads prove that the Sun was hotter during the late Pleistocene glaciation.

Monkey heads are not evidence of solar activity. http://en.wikipedia.org/wiki/Beryllium-10" [Broken] concentrations fluctuate with the strength of the solar wind, which governs the number of galactic cosmic rays in the upper atmosphere available for beryllium-10 production. The solar wind is a direct indicator of solar intensity.

You need more than monkey heads and a vague theory that a more active Sun cools the ocean by reversing convection in order to call into doubt the isotopic evidence.

The idea is as preposterous as the statement that only extra sunshine can double a trees fruit production.

Disclaimer - Big fan of http://97bottles.com/breweries/us/ca/berkeley/triple-rock-brewery-and-alehouse/monkey-head/" [Broken].
ROFL!

I think he could be on to something. Maybe we could create a Monkey head temperature proxy? Couldn't be any crazier than tree ring proxies, right?

:D
 
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  • #32
sylas
Science Advisor
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I wouldn't estimate the difference between the two as "pretty small". Extremely significant in fact.
Yes, I left myself open to that response. Say rather the differences are not as significant as what is being proposed in this thread.

Bill Illis' point about timing is important. There is no one gold standard for what extent is at a given time, and the various estimates are all part of the same general picture of the ice age, and it is that more general picture that is being questioned in this thread, without adequate references. Everyone actually working on this recognizes a substantial "Barrents-Kara" ice sheet at the LGM, and a much larger Laurentide ice sheet over Greenland and North America.

And while I am at it... the difference between tree rings and monkey heads as a proxy for temperatures is that the first has a wealth of published work supporting and studying it, and the latter... doesn't. That means, like it or not, the first is entirely appropriate to the forum, and the latter is completely inappropriate. The idea of the guidelines, as I understand them, means we shouldn't have to waste time arguing that tree rings are a better proxy than monkey heads. One is used by scientists, and the other isn't; and we are trying to learn about what is actually being practiced in science; not trying to work out new replacements of our own.

Sylas
 
  • #33
Okay, leaving the new data out of the equation, there's still the Amazon Fan sediments from 50,000 years ago which concludes that there was NO decrease in rainfall across the entire ice age! You still haven't answered the question of whether the extreme penetration of the Gulf Stream into the Arctic basin is modelled in the IPCC climate models. I assume not. This change of ocean circulation patterns is extremely significant, since it links the Atlantic with the Pacific via the Bering Strait. It's quite possible that the change in circulation patterns could be responsible for the rise in CO2 recorded in glacial termination, for example.

(Incidentally, the OP report also has relevance our early ancestors' rise to bipedalism due to an African drought, or another 'savannah hypothesis')
 
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  • #34
There's also conflicting data from the Congo fan sediment analysis: http://earthobservatory.nasa.gov/Newsroom/view.php?id=32348 [Broken]

The results show that the land environment of tropical Africa was cooled more than the adjacent Atlantic Ocean during the last ice-age. This large temperature difference between land and ocean surface resulted in drier conditions compared to the current situation, which favors the growth of a lush rainforest

This Nasa article states that drier conditions favor growth of lush rainforest!

Cool Tropical Africa
The new proxy was used in this sediment core to obtain both a continental and a sea surface temperature record. A comparison of both records shows that ocean surface and land temperatures behaved differently during the past 25,000 years. During the last ice age, temperatures over tropical Africa were 21°C, or about 4°C lower than today, whereas the tropical Atlantic Ocean was only about 2.5°C colder. By comparing this temperature difference with existing records of continental rainfall variability, lead author Johan Weijers and his colleagues concluded that the land-sea temperature difference has by far the largest influence on continental rainfall. This can be explained by the strong relationship of air pressure to temperature. When the temperature of the sea surface is higher than that of the continent, stronger offshore winds reduce the flow of moist sea air onto the African continent. This occurred during the last ice age and, as a consequence, the land climate in tropical Africa was drier than it is in today's world, where it favours the growth of a lush rainforest. These results provide further insight into the natural variation of climate and the possible consequences of a warming earth on precipitation in central Africa
 
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  • #35
The 'Hot Sun/Cold Sea' hypothesis is favorable to explain the heinrich events as well imo Heinrich Events: Marine Record of Abrupt Climate Changes in the Late Pleistocene. Cold seas would promote coastal glaciation, whilst increased insolation overall would warm the 'middle green blanket', or land between the highlands and the freezing coast. Meltwater streams would lubricate the lower glaciers and allow them to slide into the sea..
 
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  • #36
sylas
Science Advisor
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The 'Hot Sun/Cold Sea' hypothesis is favorable to explain the heinrich events as well imo Heinrich Events: Marine Record of Abrupt Climate Changes in the Late Pleistocene. Cold seas would promote coastal glaciation, whilst increased insolation overall would warm the 'middle green blanket', or land between the highlands and the freezing coast. Meltwater streams would lubricate the lower glaciers and allow them to slide into the sea..
Your reference does not back up the specifics of a "Hot Sun/Cold Sea" hypothesis at all. It's true enough that there can be sudden shifts in climate due to various effects considered in the slide set you have linked, but there's no mention there of "Hot Sun". It's rather about the work being done to explore Heinrich events, and very good introduction to the phenomenon and the work being done to investigate them.

The final slide in the set concludes as follows:
Heinrich events and other mysteries of the earth's climate system.

While we now know more than ever before about Heinrich events, there are still many questions to be answered: Why were these changes so abrupt? What drove them? Are they a reflection of variations in glaciological regimes, or are they driven by global climatic changes? How might they have been related to changes elsewhere in the world?

These issues are important, for they provide a better knowledge of the past that may prove essential in understanding the course of future changes in earth's climate system. Most important, perhaps, is the potential instability of the West Antarctic Ice Sheet. Some scientists fear that this enormous ice sheet is unstable and might collapse, thus generating modern-day Heinrich events in the Southern Hemisphere. The consequences of such a collapse would be dire indeed: a rapid 1-5 m rise in global sea levels that flood heavily-populated low-lying areas across the globe.

In the twenty-first century, perhaps more data, improved methodologies, and a new generation of scientists will put within our reach the knowledge we need to understand Heinrich events and other mysteries of the earth's climate system.

Given that this whole discussion area is about to be closed, we can't really go into it more. But for the record, there is an enormous difference between the perspective you are enunciating yourself, and the perspective described within your link.

That's a problem. You are not sticking to the forum guidelines here at all. What we need to do here -- not only in climate, but in all discussions -- is actually look at the real practice of science. NOT invent controversial new interpretations or notions of our own, and then cite that to papers which merely look at the problem for which you have some a unique set of claims not appearing in that paper.

You, and Andre, consistently fail to understand that. This is not a forum for you to propose new ideas you have for doing science better. There are other forums where you can try to reform science. Not this one.

If you cite a paper, the idea is to explain the work described in the paper, or else cite papers that directly back up the specifics of what we are describing ourselves. The aim is to make papers comprehensible, occasionally to criticize it -- though criticism should itself be backed up by other references to show that the criticism is actually a part of the science mainstream and not your own personal animus.

We must keep the focus on the actual work being done by scientists -- NOT our own personal theories for how they could do it differently. There are other forums where you can try doing your own independent theory development. This forum has a focus on exploring the current practice of science.

Cheers -- sylas
 
  • #37
There are other forums where you can try to reform science. Not this one.
I appreciate I stepped over the line with lateral thinking w.r.t the heinrich event mystery. The link was just an informative tool to describe the known phenomenon to the unitiated.

The original paper of this thread IS consistent with the rules of this forum. You have failed to answer the simple objection that the data contradicts the glacial aridity hypothesis. The Congo fan sediment data similarly contradicts the glacial aridity hypothesis:

This large temperature difference between land and ocean surface resulted in drier conditions compared to the current situation, which favors the growth of a lush rainforest
 
  • #38
sylas
Science Advisor
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I appreciate I stepped over the line with lateral thinking w.r.t the heinrich event mystery. The link was just an informative tool to describe the known phenomenon to the unitiated.

The original paper of this thread IS consistent with the rules of this forum. You have failed to answer the simple objection that the data contradicts the glacial aridity hypothesis. The Congo fan sediment data similarly contradicts the glacial aridity hypothesis:

This large temperature difference between land and ocean surface resulted in drier conditions compared to the current situation, which favors the growth of a lush rainforest
I don't have any particular problem with what the paper says, from what I have seen. I don't see why you think I need to "answer" it. I haven't said it is wrong.

Of course the paper is consistent with the forum guidelines. It might have been better for subsequent discussion to try to explain to people a bit better the content of the paper, but the idea of some modifications to existing notions is not particularly controversial. Science thrives on such challenges.

The difficulty is that the thread had diverged a number of times into more sweeping claims than what appears to be made or supported in the paper.

I am well used to science having open questions and alternative hypotheses. I'd prefer us to focus a bit better on the specifics of hypotheses actually given in the paper.

I thought [post=2519363]msg #10[/post] by mspelto gave some useful input, challenging the implication that there ever really was a requirement for aridity in the Amazon region during the LGM. But alas, that was not taken up, and the discussion went off in the usual way to look at far more sweeping personal objections to conventional ideas of the LGM rather than consideration of what is actually being investigated and challenged by the scientists cited.... (I think).

But do note we need to be winding this up now, unfortunately.

Cheers -- sylas
 

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