The Younger Dryas

[Robert Henvell]

The cold,dry Younger Dryas,with warmer interludes,had a
variable impact on the world’s climate from ca 10850-
9700 BC.Melt water from the Keewatin ice dome probably
entered the Arctic Ocean via the Mackenzie River Valley
post 10900 BC.Earlier the direction of flow had been toward
Hudson Bay.Lighter density Keewatin melt water was
transported to the Gin Seas and North Atlantic Ocean via
the Frome Strait.This impacted on the deep water Atlantic
current movements and influenced the Younger Dryas
climate change [T Tarasov,2005].About the same time
the flow of glacial Lake Candona was diverted from the
Mississippi drainage system to the St Lawerence River.
This water flowed into the Champlain lowlands.The cold
 influx altered the direction of the warm Gulf Stream
current,which contributed to the Younger Dryas,which
had its strongest impact on NW Europe.The polar front
moved south,sea level receded and vegetation patterns
were reserved.This event had less impact on Alaska and
the Siberian Plains,[reconstructions of deglaciation phases
are tenuous.

High concentrations of methane clathrate occur in sea floor
beds and permafrost.Cold and deep sea pressures contain
the methane clathrate masses.Analyses of air bubbles,
that were trapped in 15 tons of ice from the Pakitsoq site,
Greenland,imply that the C14 levels were too high in
methane to have been derived from the clathrates. C14
 isotope measurements infer a 50% increase in methane
levels over a c150 year period ca 9700 BC,which was
probably chemically consist with wetland expansion,
that produced large volumes of methane from the
bacterial breakdown of organic matter.Post ca 9700 BC
Greenland temperatures rose c10 degrees C over c 20 years
[J Severinghaus,2009].

Cores from 84 Siberian peat bogs and C14 dates from 1432
northern hemisphere peat bogs indicate that the initial
development occurred ca 16.5-14 Ka.From ca 12-8 Ka the
areal expanse of peat lands accelerated dramatically and
large volumes of natural gas were released,which helped
to initiate a major phase of deglaciation.Oak forests began
to grow proximal to the retreating ice and the C14 content
of trees and vegetation increased [G MacDonald,2006].

This segment of my prehistory notes needs additional data.
Any suggestions,references and/articles would be appreciated.

[trehinp]

I don't know up to what point this may be relevant, but I have just read this news today:

Wetlands Likely Source of Methane from Ancient Warming Event
Source: University of California, San Diego         Thu 23-Apr-2009
 Click here for more

Description
Analysis of Greenland ice led by Scripps researchers could allay fears about methane ‘burp’ accelerating current global warming trend.
Newswise — An expansion of wetlands and not a large-scale melting of frozen methane deposits is the likely cause of a spike in atmospheric methane gas that took place some 11,600 years ago, according to an international research team led by Scripps Institution of Oceanography at UC San Diego.

Yours sincerely.

Paul

[E.P. Grondine]

Melt water from the Keewatin ice dome probably
entered the Arctic Ocean via the Mackenzie River Valley
post 10900 BC.

Many thanks for this excellent summary of post 10,900 BCE events, Robert.

The start of this process appears to me to be impact related.

If the Pacific Current grew colder, then less snow fell on today's Canada,
more sunlight was absorbed, and the Earth grew warmer - hence the melt water.

It's kind of counter-intuitive how a colder Pacific Current could actually warm the Earth,
but that's what I think happened. Since my stroke I am unable to argue this or contribute much,
but that is the conclusion I reached before it.

I do expect the remains of very early marine turtle hunting maritime peoples to be recovered from the
west coast of today's Canada, probably from sites near their coastal sites, which should be well under water
now.

E.P. Grondine
Man and Impact in the Americas