[jannes]

It wouldn't be trapped in ice if it had been there for that long... I think he meant: how did it get trapped in permafrost? The only hint the article gave was this:

> Mercury accumulates in aquatic and terrestrial food chains [...]

and:

> [...] trapped in permafrost [...] since the last Ice Age.

[foota]

So... Used to be a bunch of living stuff there, it died and the mercury stayed around after it got frozen?

[fastball]

I guess it could be considered the arctic/marine equivalent of oil.