I just realized that each line represents the total variation of karma, with the individual data points that correspond to each language represented on its respective line, and at the end the line goes down to the total that corresponds to the presented language.
Currently I have 1992 points (en) plus 833 points (es) that total 2825 points. This is reflected in each graph.
EDIT: Total karma on the date of last received karma in each language will set the peak for this language graph. So the /en graph peak below is 2825, and /es a bit below, as perceived in the graph.
I guess, but could not verify, that the sum of karma enables on the site in both languages. So a high karma user in the /en site could close and reopen questions (200 karma required) in the /es site (or maybe in all the languages of the site).
The line remains four and a half years in karma 1, from when I registered on the site until I began to participate.