Earth Sciences Forum

Andre · Last edited by Andre on Tue Aug 21, 2007 7:21 pm; edited 3 times in total

The objective of the "Exhibit-#n-The-Younger-Dryas-and .......,"-threads is to investigate for ourselfs what evidence is available to judge about the alleged cold conditions of the Younger Dryas.

So, I'm nosing around in "The Holocene" articles to find:

Bryn Thomas · Joined: 27 Jul 2007 Posts: 3

A nice bit of research, very well presented but not yet sufficiently convincing. I am writing from the other side of the world, where we do not have comparable information to detail events during the Pleistocene and Holocene. Even so, the Australian Pleistocene is renowned for one particular aspect. Regional aridity.

True, one cannot say universally aridity = low temperatures, after your underlying proposition is that aridity = mild/hotter temperatures. But what about places in Asia during the Pleistocene, the Gobi Desert, for example, which were much dryer than they are now?

I would be better convinced of your conclusions if you could demonstrate other maars in the Eifel region from which cores of bottom sediments have been analysed and that show similar results.

Further, were there noticeable vegetational zone shifts in the Younger Dryas?

Again, drawing upon a reference from Tunisia, in another and completely different geographic and climatic position (south of the Alps) and claiming aridity does not equal temperature change seems to be mixing apples and oranges.

I do not deny your proposition, but, like most research, more is needed to be convincing.

Bryn
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Andre · Posted: Fri Jul 27, 2007 7:29 am Post subject:

Thanks for the reaction, permit me to restate the objective a bit better.

This is the results from the Greenland Ice Cores for that period:

The middle graph, the d18O is supposed to be a proxy for temperature. There has been extensive research with all kind of isotopes and fractination processes to confirm that isotopes are representing temperature indeed. As it was already established that there were glacial readvances dated around 11,000 years BP and around 10,000 years BP, it seemed to be confirmed that the Younger Dryas was very cold. Done deal. Right?

But 11,000 years BP and 10,000 years BP are actually just outside the confines of the Younger Dryas case. The isotope oscillations are so abrupt and given carbon dating complications, it can not be discerned if events are in or out the Younger Dryas.

Note also the extreme correlation between the middle isotopes and the upper graph of the annual snow accumulation.

There is another YD lacustrine stratification proxy in the Alps, also of the Gerzensee in Germany, I'll come to that later. Other than that virtually all cores show a hiatus in the Younger dryas, suggesting that those lakes dried up?

Anyway this is only the beginning, we will cover some more areas. Stay tuned.

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