The backlog in the Suez Canal last month caused by the container vessel Ever Given that got itself stuck in the waterway, produced a spike in ship pollution, visible from space.
The log jam forced hundreds of other ships wanting passage to park up causing the concentration of sulphur dioxide (SO2) in the air to increase five times the normal levels on the Mediterranean side of the canal.
More than 350 ships got caught up in the Suez blockage, which ran from 23 to 29 March.
Most ships were anchored at the canal’s northern end, in the Mediterranean. And while their main engines would have been turned off, the vessels were still running auxiliary power units and boilers – in what’s called “hotelling” mode
This led to a build-up of SO2 in the atmosphere locally that was observed by the EU’s Sentinel-5P satellite.
The spacecraft, managed by the European Space Agency, carries a sensitive spectrometer called Tropomi, which can detect a range of trace pollutants, including sulphur dioxide.
Sulphur dioxide is a by-product of the heavy fuel oils burnt by ship engines.
Currently, the International Maritime Organization (IMO) is on a drive to limit emissions of the gas to prevent the harmful effects it can have on the environment and human health.
“When the ships are moving, when they’re actually cruising, they are emitting more sulphur dioxide than when they’re just hotelling. But it’s the fact that we have so many ships collected together, all parked, that we get to see this signal in the Sentinel-5P satellite data,” explained Dr. Maryam Pourshamsi, an Earth Observation specialist with Airbus Defence and Space.
The spike quickly dissipated when the Even Given was freed and traffic started moving through the canal once more.
The IMO introduced a new regulation last year requiring ships to use cleaner fuel oils, with the aim of reducing annual sulphur emissions by more than 70%. Efforts must now be made to demonstrate the industry’s compliance. Satellites can play a role in this.
Later this decade, even tighter restrictions on sulphur emissions are likely to be implemented in the Mediterranean itself. The sea hosts some of the greatest ship activity in the world.
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