The layers form annually BUT it takes about 50 years for the bubbles to be isolated from the atmosphere... meaning that some gas exchange in the bubbles to the atmosphere is possible.... therefore it takes about 50 years for the bubbles to be "isolated" from the atmosphere (totally encased in solid ice) so the isotopic analysis of any particular year's bubbles must be taken as part of an "average" for the 50 years PRECEDING it... since the gases in that bubble could theoretically have been partially contaminated or gases exchanged with a changing atmosphere over that time period before it was isolated... basically time-differentiated error bars for that period of time when the bubble became trapped in the snow but before the snow became solid ice. Make sense??
This is great, I've given it as a compulsory watch for some of my masters students!
very much informative. Thank you.
@2:70 Annual layers... but 50 year moving average. Which one is it then?
The layers form annually BUT it takes about 50 years for the bubbles to be isolated from the atmosphere... meaning that some gas exchange in the bubbles to the atmosphere is possible.... therefore it takes about 50 years for the bubbles to be "isolated" from the atmosphere (totally encased in solid ice) so the isotopic analysis of any particular year's bubbles must be taken as part of an "average" for the 50 years PRECEDING it... since the gases in that bubble could theoretically have been partially contaminated or gases exchanged with a changing atmosphere over that time period before it was isolated... basically time-differentiated error bars for that period of time when the bubble became trapped in the snow but before the snow became solid ice. Make sense??