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Andre
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It may not have gone unnoticed that I've looked at a paper or two concerning the Younger Dryas oscillation
The amount of data and records about large changes in weather patterns is dazzling, confusing and sometimes contradictory, as I demonstrated here
Recalling the enigmatic start date dispute of the Younger Dryas exhaustingly elaborated upon here I did some more checking and I may stumbled upon something that may explain those contradictions a bit more.
I believe that the erratic start date of 12,900 calendar years before present caused a lot of the confusion. But first, how did that error sneaked in? I can't know for sure but I believe it's about a misidentification of volcanic tracers in the GISP2 ice core on the summit of Greenland.
It's a popular thought that the dates in ice cores can be counted by annual layers, due to seasonal differences that remain visible in the ice, however that is only true to a certain depth. Progressing with the overlaying weight the compression of the ice becomes so strong that annual layers can no longer be discerned and dating has to be done with other techniques as decribed here by Svenson et al 2008.
Incidentely notice:
The GISP2 time scale is already a few decennia old and techniques may have been less develloped then. Anyway, one important dating technique is identifying volcanic markers. Volcanic ashes known as tephra are obviously isosynchrone layers, as well as sulphur in precipitation. However you have to identify the right one. Here are ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/greenland/summit/gisp2/chem/volcano.txt, which was used to contribute to the chronology.
Notice there is a huge spike at 12932 years. Now maybe -speculating- that they could have assumed that that must have been the Laacher See eruption in the Eiffel which was the biggest volcanic event in that time frame and which was dated around 12,900 years. However their Younger Dryas started soon after that spike fixing the onset of the Younger Dryas erroneously on 12,900 years. But there may be other explanations.
It was known from tree rings and mollusc scales that this volcanic event happened about 200 years before the onset of the Younger Dryas (Kaiser and Eicher 1987, Kaiser 1993). But google wasn't really active in that time.
Note that the bigger spike of volcanic markers at data points 13033 and 13038 may have been the real Laacher See event, if one would bring that forward 130 years, the GISP2 start of the Younger Dryas would have indeed be much closer to 12,700 calendar years before present. Just a thought though.
Much more to come.
Refs:
Kaiser, K.F., 1993. Beitraege zur Klimageschichte vom Hochglazial bis ins fruehe Holozaen, rekonstruiert mit Jahrringen und Molluskenschalen aus verschiedenen Vereisungsgebieten. Habilitation, Eidgenoessische Forschungsanstalt fuer Wald, Schnee und Landschaft.,
Ziegler Druck- und Verlags-AG, Winterthur, Birmensdorf.
Kaiser, K.F., Eicher, U., 1987. Fossil pollen, molluscs, and stable isotopes in the Daettnau valley Switzerland. Boreas 16, 293}303
The amount of data and records about large changes in weather patterns is dazzling, confusing and sometimes contradictory, as I demonstrated here
Recalling the enigmatic start date dispute of the Younger Dryas exhaustingly elaborated upon here I did some more checking and I may stumbled upon something that may explain those contradictions a bit more.
I believe that the erratic start date of 12,900 calendar years before present caused a lot of the confusion. But first, how did that error sneaked in? I can't know for sure but I believe it's about a misidentification of volcanic tracers in the GISP2 ice core on the summit of Greenland.
It's a popular thought that the dates in ice cores can be counted by annual layers, due to seasonal differences that remain visible in the ice, however that is only true to a certain depth. Progressing with the overlaying weight the compression of the ice becomes so strong that annual layers can no longer be discerned and dating has to be done with other techniques as decribed here by Svenson et al 2008.
Incidentely notice:
In the 40–60 ka interval, the new time scale has a discrepancy with the Meese-Sowers GISP2 time scale of up to 2.4 ka.
The GISP2 time scale is already a few decennia old and techniques may have been less develloped then. Anyway, one important dating technique is identifying volcanic markers. Volcanic ashes known as tephra are obviously isosynchrone layers, as well as sulphur in precipitation. However you have to identify the right one. Here are ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/greenland/summit/gisp2/chem/volcano.txt, which was used to contribute to the chronology.
Notice there is a huge spike at 12932 years. Now maybe -speculating- that they could have assumed that that must have been the Laacher See eruption in the Eiffel which was the biggest volcanic event in that time frame and which was dated around 12,900 years. However their Younger Dryas started soon after that spike fixing the onset of the Younger Dryas erroneously on 12,900 years. But there may be other explanations.
It was known from tree rings and mollusc scales that this volcanic event happened about 200 years before the onset of the Younger Dryas (Kaiser and Eicher 1987, Kaiser 1993). But google wasn't really active in that time.
Note that the bigger spike of volcanic markers at data points 13033 and 13038 may have been the real Laacher See event, if one would bring that forward 130 years, the GISP2 start of the Younger Dryas would have indeed be much closer to 12,700 calendar years before present. Just a thought though.
Much more to come.
Refs:
Kaiser, K.F., 1993. Beitraege zur Klimageschichte vom Hochglazial bis ins fruehe Holozaen, rekonstruiert mit Jahrringen und Molluskenschalen aus verschiedenen Vereisungsgebieten. Habilitation, Eidgenoessische Forschungsanstalt fuer Wald, Schnee und Landschaft.,
Ziegler Druck- und Verlags-AG, Winterthur, Birmensdorf.
Kaiser, K.F., Eicher, U., 1987. Fossil pollen, molluscs, and stable isotopes in the Daettnau valley Switzerland. Boreas 16, 293}303
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