Lake Agassiz
Monday, 10. December 2007, 09:57:58
Different posts on the Black Sea Flood have lately caught a lot of attention, most recently (I think) in the 29th edition of the Four Stone Hearth blog carnival. The starting point was Chris Turney’s article claiming that Noah's Ark flood spurred European farming.
As to Noah’s Ark I would like to point out that the story about this deluge or flood is not restricted to the Bible, but also told in the Koran. The Biblical flood story (Genesis 5:28-9:17) and the Koran version (Sura 11: 25-48) were likely derived, directly or indirectly, from the Epic of Gilgamesh.
And now back to geology. So much happened around 8200 years before the present, that you can hardly talk about a twist of fate. But first a word on dates. Within this time scale geologists talk about years before present or in short BP/bp/b.p. Because the "present" time changes, standard practice is to use 1950 as the arbitrary benchmark of what's considered "present". Historians, however, talk about calendar years years and BC (Before Christ). (Funny enough there is no year zero in our calendar). This means that 8200 years ago is 8143 BP (± 1) or 6193 BC (± 1).
So maybe the Black Sea was flooded around 8200 B.P, and maybe this gave rise to the Noah myth, and maybe this spurred European farming. Anyway the Greenland ice core documents an abrupt cooling around 8200 B.P. and this may be connected with the occurrence of the outburst flood and catastrophic drainage from the glacial lake Agassiz on the margin of the retreating (North American) Laurentide Ice Sheet into the North Atlantic via the Hudson Strait.
The rapid flow of immense amounts of cold meltwater into the North Atlantic could have changed the ocean circulation for a considerable time, it has been speculated (in the first instance the bottom circulation as cold water is denser than relatively warmer water).
A new study seems to confirm this.
The released water masses has been estimated to 164 000 km3, and must have disturbed the temperature and salinity gradients driving the ocean currents, including the Golf Stream. The reaction was felt within a few decades. The Golf Stream weakened. The atmosphere cooled down. Glaciers in Norway grew. There was drought in Northern Africa and the monsoon in Asia weakened.
The study is based on sediment cores taken between Greenland and Canada - at the red spot on the map. The grain size indicates a rapid increase in bottom current activity. This coincides with an abrupt increase in sedimentation rates. A radical change in the sediment source area over a period of about 100 years is evident. Plancton fossils in the core indicates a sharp near surface cooling of around 1.5°C.
The research article will later be published in the journal Science but is already available on line at Sciencexpress (subscription is needed to access the article).
Reduced North Atlantic Deep Water Coeval with the Glacial Lake Agassiz Fresh Water Outburst
Published Online December 6, 2007
Science DOI: 10.1126/science.1148924
http://www.sciencemag.org/cgi/content/abstract/1148924v1?etoc
As to Noah’s Ark I would like to point out that the story about this deluge or flood is not restricted to the Bible, but also told in the Koran. The Biblical flood story (Genesis 5:28-9:17) and the Koran version (Sura 11: 25-48) were likely derived, directly or indirectly, from the Epic of Gilgamesh.
And now back to geology. So much happened around 8200 years before the present, that you can hardly talk about a twist of fate. But first a word on dates. Within this time scale geologists talk about years before present or in short BP/bp/b.p. Because the "present" time changes, standard practice is to use 1950 as the arbitrary benchmark of what's considered "present". Historians, however, talk about calendar years years and BC (Before Christ). (Funny enough there is no year zero in our calendar). This means that 8200 years ago is 8143 BP (± 1) or 6193 BC (± 1). So maybe the Black Sea was flooded around 8200 B.P, and maybe this gave rise to the Noah myth, and maybe this spurred European farming. Anyway the Greenland ice core documents an abrupt cooling around 8200 B.P. and this may be connected with the occurrence of the outburst flood and catastrophic drainage from the glacial lake Agassiz on the margin of the retreating (North American) Laurentide Ice Sheet into the North Atlantic via the Hudson Strait.
The rapid flow of immense amounts of cold meltwater into the North Atlantic could have changed the ocean circulation for a considerable time, it has been speculated (in the first instance the bottom circulation as cold water is denser than relatively warmer water).
A new study seems to confirm this.
The released water masses has been estimated to 164 000 km3, and must have disturbed the temperature and salinity gradients driving the ocean currents, including the Golf Stream. The reaction was felt within a few decades. The Golf Stream weakened. The atmosphere cooled down. Glaciers in Norway grew. There was drought in Northern Africa and the monsoon in Asia weakened.
The study is based on sediment cores taken between Greenland and Canada - at the red spot on the map. The grain size indicates a rapid increase in bottom current activity. This coincides with an abrupt increase in sedimentation rates. A radical change in the sediment source area over a period of about 100 years is evident. Plancton fossils in the core indicates a sharp near surface cooling of around 1.5°C.
The research article will later be published in the journal Science but is already available on line at Sciencexpress (subscription is needed to access the article).
Reduced North Atlantic Deep Water Coeval with the Glacial Lake Agassiz Fresh Water Outburst
Published Online December 6, 2007
Science DOI: 10.1126/science.1148924
http://www.sciencemag.org/cgi/content/abstract/1148924v1?etoc
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Have you some data of the glaciers development in this period? Or do you know how to find them?
By piombaldo, # 12. December 2007, 23:34:13
Climate in Greenland is said to have a 500 years-cycle. http://www.geus.dk/viden_om/voii/voii03_fig001.jpg is a temperature graph over the latest 1500 years. The Nordic settlement took place in a warm period. 500 years later all Nordic settlers had disappeared. Vesterbygden and Østerbygden are the names of the two main settlements and “uddør” means “dye out”. It is not known why they died out. Did it become too cold for farming? Did the Inuits kill them? Or was there another reason (like disease)?
Unfortunately my Italian knowledge is restricted to ordering a couple of beers and that sort of things, otherwise i would have read your blog at http://aldopiombino.blogspot.com/ with great interest.
Ole
By nielsol, # 13. December 2007, 15:25:46
My blog is in italian. I know that this is a problem. Perhaps I will do an English edition, in the future...
By piombaldo, # 14. December 2007, 08:49:40
I have posted it on my blog (in Italian, obviously...) but I want to ask you what do you think.
Certenly if tis is true, there is a danger and other volcanoes can exist beneath greenland ice, in this case a good ground surface must be scheduled....
By piombaldo, # 15. December 2007, 13:40:46
‘http://mobile.ljworld.com/news/2007/dec/13/ku_prof_global_warming_not_sole_culprit/
“Where the crust is thicker, things are cooler, and where it’s thinner, things are warmer,” von Freese explained in a press release from Ohio State. “And under a big place like Greenland or Antarctica, natural variations in the crust will make some parts of the ice sheet warmer than others,” he said.’
This sounds reassuring, and the rest may be pure journalist speculation?
I doubt that there are any future volcanoes hidden under Greenland.
I would like to hear more about these/this hotspot(s) - probably some publication will turn up later. I would also like to know the exact geographic location. The only thing I have seen so far was in the “north east corner”. As you will know the tertiary volcanism was at the south east.
Ole
By nielsol, # 15. December 2007, 19:36:22