Sam, multi-year dynamics are off-topic here as long as discussing them does not lead to anyhow better understanding of the 2019 melting season. The _topic_ is named "The 2019 melting season", and thus any discussion which does not and/or can not allow to gain knowledge about this one single melting season, in here - is off-topic by definition. This does not anyhow reduce such discussion's own value, of course. The term "off-topic" merely indicates the discussion, however valuable, is not supposed to happen in this particular topic, nothing more and nothing else.
That said, there are indeed some subjects which, despite being off-topic, may be allowed to be discussed in this topic by the board's administration, to some finite length. The one Sark so originally touched - is probably among them. Importance and obvious relation to this melting season are among probable reasons for it to be. However, please always remember that the more off-topic discussion we'd do here, the less compact and "handy" the topic becomes for great many people who come to it for information specifically about the melting season itself. It is, you see, much about respect to other people to limit off-topic discussion here quite much, even if and when there would be good reasons to have it.
IMHO.