The spot rate for a 40-foot container from Shanghai to Los Angeles rose to US$11,030, up 3.3 per cent late last week from the previous week and 125 per cent higher than a year ago, according to the Drewry World Container Index released last Thursday.

A slightly upward trajectory is also seen in weekly data from Freightos that includes surcharges and premiums: China to the US West Coast rates were up 2.6 per cent at $15,615 and China to the US East Coast jumped 6 per cent to $17,901 - both the highest since early November.

It's unusual to see container rates not fall between mid-January and the week following Lunar New Year in China, according to research from Oslo-based Xeneta, a freight market-analytics platform. Many shippers of cargo had hoped for a decline in what's traditionally been a seasonal shipping lull after that holiday, but it hasn't happened.

"It just goes to show how different the market is this year compared to what we've seen in previous years," Emily Stausboll, a market analyst with Xeneta, said on a webinar. "These are different times, and you have to be ready for that to come and not expect everything to happen as it usually does."

Port congestion, particularly in the US, is among the biggest reasons container rates remain elevated. Kuehne+Nagel International AG, the Swiss logistics giant, launched its Seaexplorer disruption indicator in January, and the latest reading shows shipping snarls jumped to a new high last week.

Beyond the capacity shortages, the fighting in Ukraine threatens to affect the availability of workers in maritime trade.

According to the International Chamber of Shipping, 10.5 per cent of the world's 1.9 million seafarers are Russian, while 4 per cent are Ukrainian. Any obstructions to their ability to travel for work and receive regular pay would exacerbate shipping disruptions.