This sort of phenomenon can be seen lots of times throughout the past decades. Anytime oil falls below a certain price, it becomes cheaper to pay to keep the ships running offshore under the assumption that oil prices will increase in the near term.

It does seem that that would be the pertinent question.

If you look at the density map layer option, you can crossfade between 2013 and 2014. I didn't sign up for an account, but it looks like in 2014 at least they saw an increase in traffic where the tankers are now parked.

But, last year there was also significantly more traffic through that port in general, so it may not be that the percentage of temporarily held ships as a function of total traffic changed?