More than 2% of global freight capacity is at a standstill in the North Sea, an expert from Germany's IfW economic institute said, a "very unusual" situation for the ports there.

"There is currently no end in sight to the congestion in container shipping," said IfW's Vincent Stamer, adding that traffic jams were also growing outside Chinese ports.

"For Germany and the EU, this affects overseas trade in particular, especially with Asia, where consumer electronics, furniture and textiles, for example, are shipped from."

So much for the light at the end of the supply-chain tunnel!