By Mary Beth Sheridan
Scores of ships are backing up at the Panama Canal, where low water levels linked to El Niño and climate change have led authorities to restrict travel through one of the world's most important trade arteries.
The traffic jam is a grim sign for a global economy that has been whipsawed by supply-chain challenges - and for American businesses in particular.
Around 40 percent of US container traffic moves through the canal that connects the Atlantic and Pacific oceans.
The congestion is driving up shipping prices and causing delays in transporting merchandise just as importers are starting to gear up for the Christmas season.
And things could get worse.
"We have all the conditions we need to repeat what we had with 2015-16," said Steven Paton, who heads the environmental monitoring programme at the Smithsonian Tropical Research Institute.
That was one of the driest periods on record in many areas of the Central American nation.
"There will absolutely be greater restrictions" on ships crossing the canal next spring, the driest time of the year, he said.
To conserve water, canal authorities are limiting the number of ships allowed to make the crossing to 32 per day, down from an average of 36 in normal times.
They've also imposed weight restrictions on the vessels. Around 50 million gallons of water is required to move each ship through the locks. Only some of it is recycled.
Normally, there are up to 90 ships waiting to enter the canal; this week, there were more than 120. Earlier this month, as many as 160 ships sat idling.
The congestion is adding to the global bottlenecks caused by the Russian invasion of Ukraine and the Covid-19 pandemic, said Abe Eshkenazi, CEO of the Chicago-based Association for Supply Chain Management.
"We're seeing just another disruption on top of an already stressed system," he said.
Panama is ordinarily considered one of the world's wettest countries, with a rainy season that extends from May until late December.
But the canal region is suffering one of its driest years since record-keeping began 143 years ago, said Paton.
This summer, high-pressure heat domes have focused on much of the Caribbean and Central America, squashing rainfall chances and delivering intense heat.
Mexico and other countries in the region are also dealing with widespread drought.
In addition to the lesser replenishment of the lakes that feed the Panama Canal from the source rainforests, the hot and dry conditions lead to higher water temperatures and increased evaporation. This means even less available water in the lakes, and lower waters in the canal itself.
A combination of a developing and powerful El Niño, the warming of waters in the equatorial Pacific Ocean, and human-caused climate change are probably supersizing Panama's recent dry spell.
While El Niño acts as a multiplier, the drought was underway earlier in the year - February through April featured about 10 to 25 percent of normal rainfall in the area.
"The main impacts of climate change in Panama are related to the increase in the number, intensity and variability of extreme precipitation events, severe droughts and high temperatures," said the United Nations' Piedad Martin earlier this year when the Panama government launched a programme to increase climate resilience.
Ian Livingston in Washington contributed to this report.