A critical global shipping node – Egypt’s Suez Canal – was reopened on Monday, March 29, six days after being shut down when the 400-meter-long container ship Ever Given became lodged in the canal. A statement by the Suez Canal Authority initially blamed the incident on high winds and a sand storm that reduced visibility, but later said that strong winds were “not the only cause,” and that an investigation was ongoing.

There is no clear indication at this point that climate change played a role in the sandstorm that led to the ship’s blocking the canal, but the incident raises intriguing questions that likely will prompt research into any correlation.

The multi-day shutdown of one of the world’s busiest shipping chokepoints underscores the vulnerability of the global food system and economy to disruptions. That vulnerability is playing on the stage of increasingly extreme weather, rising seas, and an increasingly just-in-time world of shipping.

Meteorology of the event

The high winds and sand storm that contributed to the grounding incident were caused by a cold front trailing to the south of a low-pressure system centered near southern Turkey.

As the cold front swept eastwards across Egypt on March 23, powerful winds of 25-30 knots (29-35 mph) blew along the axis of the Red Sea from the south-southeast, into the southern end of the Suez Canal, as seen in the 6 UTC analysis from the GFS model (Figure 2). The Ever Given became stuck at 05:40 UTC that day. According to the GFS analysis, a sharp wind shift, with winds blowing out of the southwest to west, was present near the spot where the Ever Given blocked the canal, about five miles north of its connection with the Red Sea.

The New York Times reported that winds in excess of 70 mph blew in the region where the Ever Given became stuck; the owner of the ship, BSM, said that “initial investigations suggest the vessel grounded due to strong wind.” The strong winds were accompanied by large amounts of sand and dust, reducing visibility and making navigation more challenging.

Winds this strong are uncommon in the region, but strong winds have delayed shipping traffic or closed the Suez Canal on at least two occasions – December 11, 2010, and February 11, 2015.

A video Tweeted by Vakrio Technologies showed the course and heading of the Ever Given as it entered the canal, demonstrating that the canal is initially angled from southwest to northeast. Ever Given passed very close to the northwest bank of the canal at the start of its traverse, presumably pushed by the strong south-southeasterly winds blowing into the canal entrance from the Red Sea. For unknown reasons, the vessel was moving at 15 mph, well in excess of the 10 mph speed limit in the canal. As explained in an excellent analysis in the Financial Times (free registration required) by Brendan Greely, when a ship gets too close to a bank, shallow-water hydrodynamic forces can act to spin the boat – a well-known phenomenon known as the bank effect, where the water speeds up between the boat and the bank, the pressure drops, and the stern is pulled into the bank while the bow is pushed away from shore. Possibly because of the bank effect, the Ever Given then slewed close to the opposite (east) bank of the canal. At that point, the canal is oriented north-south, and the vessel angled its heading to the left, perhaps again due to the bank effect, or possibly in response to a crosswind that had developed due to a wind shift to a more westerly direction. The ship again came close to the west (left) bank, potentially because of a swirling wind that briefly blew from the south, reducing the cross-wind component that was pushing the boat to the right. The Ever Given finally ran aground with its stern on the west bank of the canal and its bow on the east bank (Figure 3), suggesting that the bank effect may have acted to spin the ship and lodge it in the canal when it came too close to the west bank.

Near-record March heat preceded the March 23 sandstorm

An extraordinary March heat wave preceded the cold front and sandstorm that contributed to the canal-blocking incident; the day previously, Kharga, Egypt, recorded a scorching temperature of 44 degrees Celsius (111.2°F), just 0.2 degrees Celsius below the highest March temperature ever recorded in the nation, according to weather records expert Maximiliano Herrera. The day of the sandstorm (March 23), Luxor, Egypt, hit 43.6 degrees Celsius – just 0.6 degrees Celsius below the March national record. Herrera documented that on the day after the sandstorm, Mitribah, Kuwait hit 44.6 degrees Celsius (112.3°F) – the hottest temperature ever recorded in the Arabian Peninsula in March.

Extreme heat dries the soil, allowing winds to more readily mobilize sand grains and create a dust storm. For example, a study of a high-impact sandstorm over the Middle East during August-September 2015 found that unusually hot and dry conditions preceding the event were responsible for its near-record intensity.

“The simulations showed that what was very unique about this storm is that, first, it was preceded by a very hot period, and so the land that was not covered with vegetation would be drier and it would be easier to entrain sand grains from it,” said study co-author Eli Bou-Zeid, in an interview with the Climate News Network.

Similarly, when the strong cold front swept through Egypt on March 23, 2021, the winds behind the front were able to loft an unusual amount of dust and sand into the air because of the earlier hot conditions. That created difficult circumstances for navigation on the Suez Canal. Climate change is increasing the incidence of such extreme heat events, and may have played a role in the blockage of the Suez Canal if reduced visibility is determined to have played a role in the ship’s grounding.

Wind a more likely culprit than poor visibility

Wind appears to be the main culprit for the grounding of the ship, however, with the sandstorm’s strong and variable winds making it more difficult to navigate the passage. For now at least, it’s speculative whether climate change may have increased the odds of the strong wind event on March 23.

However, the large-scale weather pattern responsible for the sandstorm was quite extreme, and climate change could have contributed to make this event more extreme. Observations of the upper-level air patterns at 500 millibars (about 18,000 feet) on that date showed a very amplified and wavy jet stream pattern, with a strong ridge of high pressure over the Middle East and a strong trough of low pressure just to its west over the central Mediterranean Sea (Figure 5). Both features were about two standard deviations from the mean.

There has been a sharp increase in similar “global weirding” extreme jet stream patterns in summer, as a result of a phenomenon known as quasi-resonant amplification or “QRA” – described in detail in an October 2018 realclimate.org post by Michael Mann and reported in this writer’s 2018 post at Weather Underground. Modeling studies have shown that climate change may be responsible for the observed increase in summer QRA events, potentially because of how the Arctic is warming up more than twice as fast as the planet overall. A March 2021 study, “Large scale connection to deadly Indian heat waves” found that QRA events can also occur in spring, and may be connected to deadly April and May heat waves that affected India in 2010-2015.

But Dr. Stefan Rahmstorf, a co-author of the 2018 QRA study, wrote in an email that there was no evidence of QRA conditions during the week leading up to the Suez Canal sandstorm on March 23. Dr. Mann, lead author of the 2018 QRA study, added, “Our work certainly supports the increased incidence of persistent weather extremes of this sort (in fact, there’s a new study just out that further confirms that these events are indeed increasing in Europe during the warm season), so the connection is plausible but not confirmed.” Thus, it is possible that climate change may have increased the odds of the unusually amplified jet stream pattern responsible for the March 23 wind event in Egypt, but this possibility is speculative, and only more research may lead to further understanding of a possible connection with a changing climate.

Climate change increasingly likely to threaten global trade chokepoints

While the connections to climate change of the grounding of the Ever Given and closure of the Suez Canal are speculative, the event serves as a warning that climate change can be expected to cause an increase in extreme events that will impact critical global trade chokepoints. As explained in a 2017 report from Chatham House, much of the food required to feed 2.8 billion people passes through 14 critical shipping chokepoints (Figure 6): maritime corridors such as straits and canals, coastal infrastructure in major crop-exporting regions, and inland transport infrastructure in major crop-exporting regions. These chokepoints are at risk of closure due to three factors:

1) Extreme weather events or sea level rise;
2) Security and conflict hazards from war, political instability, piracy, organized crime and/or terrorism; and
3) Decisions by authorities to close a chokepoint or restrict the passage of food (for example, by imposing export controls).

Thirteen of the 14 critical chokepoints have had a closure or interruption in transit at least once between 2002-2017, with the Strait of Gibraltar the only exception. Many of these events had potential climate change connections: for example, the 2011 and 2012 heat waves in the U.S. that led to multiple derailments of trains where railroad tracks warped in excessive heat.

The report explained, “Climate change is increasing the threat of disruption by acting as a hazard multiplier across all three categories of chokepoint risk. It will increase the frequency and severity of extreme weather, leading to more regular closures of chokepoints and greater wear and tear on infrastructure. Rising sea levels will threaten the integrity of port operations and coastal storage infrastructure, and will increase their vulnerability to storm surges. Climate change is expected to aggravate drivers of conflict and instability. It will also lead to more frequent harvest failures, increasing the risk of governments imposing ad hoc export controls.”

The forced closure of the Suez Canal due to a possibly climate change-related event should act as a warning: Climate change will cause disruptions to critical global trade chokepoints more frequently in the coming years, and we need to take strong actions to reduce emissions of greenhouse gases and reduce vulnerabilities to chokepoint disruptions.

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