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Apparently not. They say the ice "is not organized into neat layers", so they have approximated the age based on potassium and argon concentration.

Though it doesn't mention what potassium and argon have to do with age. Short explanation, anyone?

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Isotopes of potassium decay to argon and the amount of accumulated argon - combined with knowledge of the decay rate - allows one to use the system as a clock:

https://en.wikipedia.org/wiki/K%E2%80%93Ar_dating

that assumes you know how much it started with and what the environment was like then

It's safe to assume that these assumptions have been accounted for by the scientists developing and performing isotopic dating.

The Wikipedia page covers these issues, albeit for crystalized rock instead of ice. The measurement is a ratio, so the key thing is establishing that Argon 40 is normally not present in rain or brand new ice.

But are there at least a million layers?

I mean, there have to be some amount of well preserved cycles from the compaction of snowfall right? It would be very strange if ALL the ice was not organized!

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