author Mulkey responds to a similar question in the comments:

Aaron O'Dea, told me in an email that the upwelling has been "as predictable as clockwork" for at least 40 years of detailed data used in the study. They have less detailed data showing that it goes back at least 80 years. And while this doesn't mean it never vanished before, he said they can trace the the upwelling's impact on coastal ecology and humans for 11,000 years.

That's not really a retort, unless the question in the comments is different than my comment.

11,000 years of data doesn't give you any meaningful data unless you can show that this _never_ happened in the past. 40 years is the amount of data for that.

There's no good evidence to suggest that 1/40 of it not happening is an abberation. It could be 1/100 of those 11,000 years this happened and there'd be no way to know.

If it continues to happen, we'll have something. For now nobody should be "alarmed".