Climate Fluctuations 115,000 Years Ago: Were Short Warm Periods Typical for Transitions to Glacial Epochs?

As the archaeology creates new scenarios for the migration of hominids
out of Africa and into Asia and Europe dating back beyond the
"traditional" 70,000 years or so, the climate needs to be studied for
explanations for this expansion.



Climate Fluctuations 115,000 Years Ago: Were Short Warm Periods
Typical for Transitions to Glacial Epochs?

Russian and German researchers took sediment probes of four silted up
lakes in Central and Eastern Europe in order to reconstruct the
climate of the Eemian Interglacial 115,000 years ago. At this time the
Eemian Interglacial ended and was followed by the Weichselian Glacial
which ended 15,000 years ago. (Credit: Frank W. Junge/SAW)

ScienceDaily (Mar. 7, 2010) 7 At the end of the last interglacial
epoch, around 115,000 years ago, there were significant climate
fluctuations. In Central and Eastern Europe, the slow transition from
the Eemian Interglacial to the Weichselian Glacial was marked by a
growing instability in vegetation trends with possibly at least two
warming events. This is the finding of German and Russian climate
researchers who have evaluated geochemical and pollen analyses of lake
sediments in Saxony-Anhalt, Brandenburg and Russia.

Writing in Quaternary International, scientists from the Helmholtz
Centre for Environmental Research (UFZ), the Saxon Academy of Sciences
(SAW) in Leipzig and the Russian Academy of Sciences say that a short
warming event at the very end of the last interglacial period marked
the final transition to the ice age.

The Eemian Interglacial was the last interglacial epoch before the
current one, the Holocene. It began around 126,000 years ago, ended
around 115,000 years ago and is named after the river Eem in the
Netherlands. The followed Weichselian Glacial ended around 15,000
years ago is the most recent glacial epoch named after the Polish
river Weichsel. At its peak around 21,000 years ago, the glaciers
stretched as far as the south of Berlin (Brandenburg Stadium).

The researchers studied lake sediments to reconstruct the climate
history of the Eemian Interglacial, since deposits on river and lake
beds can build up a climate archive over the years. The sediment
samples came from lakes that existed at the time, but which have since
silted up and been uncovered in the former open cast mines at Gröbern
near Bitterfeld, Neumark-Nord in the Geiseltal valley near Merseburg,
and Klinge near Cottbus and at Ples on the upper reaches of the Volga,
around 400 kilometres north-east of Moscow. Gröbern in Saxony-Anhalt
is now seen by experts as one of the most studied places for Eemian
Interglacial climate history in Germany. As well as pollen
concentrations, the researchers analysed the level and ratios of
stable carbon (13C/12C) and oxygen isotopes (18O/16O) in carbonates
and organic matter from sediment layers, since these provide
information about the vegetation development and an indication of the
climate.

The results show a relatively stable climate over most of the time,
but with instabilities at the beginning and end of the Eemian
Interglacial. "The observed instability with the proven occurrence of
short warming events during the transition from the last interglacial
to the last glacial epoch could be, when viewed carefully, a general,
naturally occurring characteristic of such transition phases,"
concludes Dr Tatjana Boettger of the UFZ, who analysed the sediment
profiles at the UFZ's isotope laboratory in Halle. "Detailed studies
of these phenomena are important for understanding the current
controversial discussed climate trend so that we can assess the human
contribution to climate change with more certainty," explains Dr Frank
W. Junge of the SAW.

From reconstructions of climate history, we know that in the Earth's
recent history, interglacial epochs occurred only once every 100,000
years or so and lasted for an average of around 10,000 years. The
current interglacial epoch -- the Holocene -- has already lasted more
than 10,000 years and reached its highest point so far around 6000
years ago. From a climate history perspective, we are currently at the
end of the Holocene and could therefore expect to see a cooling-down
in a few thousand years if there had been no human influence on the
atmosphere and the resulting global warming.

With its expertise, the UFZ plays a part in researching the
consequences of climate change and in developing adaptation
strategies. You can find more on this in the special issue of the UFZ
newsletter entitled "On the case of climate change" at
http://www.ufz.de/index.php?enD10690



http://www.sciencedaily.com/releases/2010/03/100302111912.htm

On Mon, 8 Mar 2010 09:48:27 -0800 (PST), Jack Linthicum
<jacklinthicum@earthlink.net> wrote:


The archaeologists revealed a high number of items, mainly prehistoric
stone tools, about nine metres under the ground in Arbil, capital of
the Kurdish autonomous region, said archaeologist Novacek, from the
University of West Bohemia in Plzen.


nine meters below current surface - that's a truly amazing
sedimentation rate, especially for a terrestrial location.

Hayabusa