Meaning of "plumb" as verb

I found in the free dictionary the various meanings of plumb as a verb and mainly it seems to have the meaning of explore/study/delve into.

However, within the title of an article of the International Herald Tribune (Aug. 11, 2011), namely Spanish case plumbs trans-Atlantic divide on Web privacy, it seems to have the meaning trigger. Is that right?

Solution 1:

Plumb is "measure the depth of", and shares a root with "plumb" meaning "connect pipework" -- both come from the latin plumbium, meaning "lead", as a lead weight at the end of a string was an instrument for measuring the depth of a body of water, while pipes were once made of lead.

Solution 2:

Personally I think it's a play on words: The title originally was Spanish case plumbs depth of trans-atlantic [sic] divide on Web privacy. Plumb here means to measure the depth of a body of water;

I don't think it means trigger, you had it correctly the first time: exploring, using the first example on the free dictionary; http://www.thefreedictionary.com/plumb (edit)

For those who are confused, I used THIS website: http://e.mydigitalfc.com/PUBLICATIONS/DCF/DCF/2011/08/11/ArticleHtmls/Fight-for-the-right-to-be-forgotten-11082011161005.shtml ; (where the screenshot is from) in order to answer the question, in the comments below the question someone put in the correct link (It was correct for me, I couldn't open the other websites), and THAT is the link to the article I based my answer on. As you can see, it DOES say 'plumbs depth'. I did not change the title.