ScienceDaily (Aug. 4, 2008) — Researchers in Germany, Switzerland, and the United States have shown, for the first time, that an extremely fast climate change occurred in Western Europe. This took place long before human-made changes in the atmosphere, and is causatively associated with a sudden change in the wind systems.
Now that is frightening.
mgb_phys
Aug7-08, 05:15 PM
Wasn't the ice retreating in europe 12,700 BP? I thought the maximum extent for the Wisconsin/Wurm ice age was about 20,000BP.
It's been thought for a while that ice ages can start very quickly, but I didn't realise it was down to a few years!
This is extremely important. Achim Brauer published 3 earlier articles about the Meerfelder maar, the most outstanding high resolution record for the Younger Dryas, Pollen analysis shows a quick and distinct shift from abundant boreal forest type to arid steppe around 12,680 "varve" years BP. But "cold" is not reflected in the plant species. In the previous article, Lücke and Brauer 2004, mention "warmer summers". See:
http://earth.myfastforum.org/about18.html
Considering that 12,700 true calendar years is just about 10,700 radio carbon (14C) years ago, compare that with:
...Two very significant climatic warming events (centered around 12,400 14C yr BP and ~10,700 14C yr BP respectively) correspond with the observed major changes in diatom assemblages....
Hence That cooling is highly ambigeous
Integral
Aug7-08, 09:04 PM
Not sure of my sources on this as it has been some years since I read it. Have they not found Mammoths with nearly intact vegetation in their digestive system. The understanding that I came away with was that the living animal had to have been nearly flash frozen to explain the state of preservation. The remains were found in what is now the Arctic region, the digestive system contends where more in line with a moderate climate. the explanation offered was that there could have been a shift in the earth angle of tilt. I believe that the time scale on this would have been in the neighborhood of 12000yrs ago. The effects of such a dramatic change would vary, some regions would move from moderate to cold, in other areas you would see the opposite change, from cold to warm.
Such a change would have to be caused by gravitational interaction with a fairly massive body. 1200yrs seems a little late for such a interaction.
DEMcMillan
Aug7-08, 09:41 PM
Brian Fagan, the retired archeologist has produced a series of books on weather discerned from the archeologic record, including food and migration patterns. I believe his work about this time period should prove useful in answering some of the questions raised.
wolram
Aug7-08, 10:58 PM
Here is a nice peice about the mamouths
http://www.talkorigins.org/faqs/mammoths.html
nucleus
Aug8-08, 12:28 AM
In Whitehorse, Yukon, Canada they have the Beringia Interpretive Centre which I went through a couple years ago. It has woolly mammoths and other animals on display. You can take a virtual tour etc here:
http://www.beringia.com/01/01index.html
Andre
Aug8-08, 02:25 AM
You guys picked a wrong time to discuss mammoths. There are no "flash frozen" mammoths, just peat preserved mummies of mammoths including complete stomach contents. The Yukagir mammoth has been analysed in detail again with the same result: productive grassy steppe.
jim mcnamara
Aug8-08, 11:44 AM
The Younger Dryas manifests in the Chesapeake Bay region in the Eastern US as a ~.5 - 3m aeolian layer deposited over a period of ~800 years. It was very dry in that area with a lot of blown dust - obviously - during that time. The onset was abrupt, based on pollen analysis.
One hypothesis for the cooler dryer phase was that the St Lawrence River became ice free, and really massive fresh water flows caused thermohaline flow shutdown.
One hypothesis for the cooler dryer phase was that the St Lawrence River became ice free, and really massive fresh water flows caused thermohaline flow shutdown.
It's also a bit unclear/counter intuitive how a relative (earth scale) minor hydrographic event could have such an impact allmost world wide, including oceanic proxies in the Pacific.
jim mcnamara
Aug11-08, 12:40 PM
What you show is another hypothesis, clearly: Does this article constitute "any" evidence?
Broecker, WS., Does the trigger for abrupt climate change reside in the oceans or in the atmosphere? Science 300 (5625): 1519-1522 JUN 6 2003.
Abstract:
Two hypotheses have been put forward to explain the large and abrupt climate changes that punctuated glacial time. One attributes such changes to reorganizations of the ocean's thermohaline circulation and the other to changes in tropical atmosphere-ocean dynamics. In an attempt to distinguish between these hypotheses, two lines of evidence are examined. The first involves the timing of the freshwater injections to the northern Atlantic that have been suggested as triggers for the global impacts associated with the Younger Dryas and Heinrich events. The second has to do with evidence for precursory events associated with the Heinrich ice-rafted debris layers in the northern Atlantic and with the abrupt Dansgaard-Oeschger warmings recorded in the Santa Barbara Basin.
Andre
Aug12-08, 06:43 AM
What you show is another hypothesis,
Dunno, they sought supper for the melt water hypothesis but didn't find any:
The EOS article:
http://www.eeescience.utoledo.edu/Faculty/Fisher/Lowell_etal_EOS05.pdf
Preliminary results indicate that ice recession at both outlet areas is later than supposed, and that large volumes of meltwater were not catastrophically released from Lake Agassiz at the beginning of the Younger Dryas
clearly: Does this article constitute "any" evidence?
Currently no access to the article, but I would not take any conclusions before checking all the evidence and that's a few decades worth of work.
See also:
http://www.physicsforums.com/showthread.php?t=242912
http://www.physicsforums.com/showthread.php?t=209528